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DNA methylation aberrations have been implicated in acquired resistance to platinum drugs in ovarian cancer. In this study, we elucidated an epigenetic signature associated with platinum drug resensitization that may offer utility in predicting the outcomes of patients who are coadministered a DNA methyltransferase inhibitor. The ovarian cancer specimens we analyzed were derived from a recent clinical trial that compared the responses of patients with recurrent platinum-resistant ovarian cancer who received carboplatin plus the DNA methyltransferase inhibitor guadecitabine or a standard-of-care chemotherapy regimen selected by the treating physician. Tumor biopsies or malignant ascites were collected from patients before treatment (day 1, cycle 1) or after treatment (after 2 cycles) for epigenomic and transcriptomic profiling using the Infinium HumanMethylation450 BeadChip (HM450). We defined 94 gene promoters that were hypomethylated significantly by guadecitabine, with 1,659 genes differentially expressed in pretreatment versus posttreatment tumors. Pathway analysis revealed that the experimental regimen significantly altered immune reactivation and DNA repair pathways. Progression-free survival correlated with baseline expression levels of 1,155 genes involved in 25 networks. In functional investigations in ovarian cancer cells, engineered upregulation of certain signature genes silenced by promoter methylation (DOK2, miR-193a, and others) restored platinum drug sensitivity. Overall, our findings illuminate how inhibiting DNA methylation can sensitize ovarian cancer cells to platinum drugs, in large part by altering gene expression patterns related to DNA repair and immune activation, with implications for improving the personalized care and survival outcomes of ovarian cancer patients.Significance: Epigenomic targeting may improve therapeutic outcomes in platinum-resistant and recurrent ovarian cancer in part by effects on DNA repair and antitumor immune responses. Cancer Res; 78(3); 631–44. ©2017 AACR.

Table S3. 77 integrated genes

Figure S1. (A) Predicted cancer/stromal signatures in TCGA and our data. (B) Correlation between NMF and ESTIMATION estimated cancer cell purity in TCGA OV data. (C,D) Predicted relative proportion of cancer/stromal cell in our and TCGA data. Figure S2. Full list of pathways enriched by differentially expressed genes induced by guadecitabine. Figure S3. A-D. Spearman correlation between the beta values of 24 CpG sites within the promoters of 19 genes significantly demethylated in ascites samples and predicted proportions of B cells (A), T cells (B), NK cells (C), and total cells (D). E-H. Spearman correlation between the beta values of 352 CpG sites within the promoters of 94 genes significantly demethylated in tumor samples and predicted proportion of B cells (E), T cells (F), NK cells (G), and total cells (H). Complete sets of correlation coefficients are provided in Supplementary Table 8. X axis corresponds to Spearman correlation coefficients.

Table S1. Genes demethylated by Guadecitabine Table S2. Differentially expressed genes

Table S4. 1155 genes associated with PFS Table S5. 203 guadecitabine deM genes associated with PFS Table S6. 293 guadecitabine upregulated genes associated with PFS

Supplementary Material and Methods

Tolinapant (ASTX660) is a potent, nonpeptidomimetic antagonist of cellular inhibitor of apoptosis proteins 1 and 2 (cIAP1/2) and X-linked IAP, which is currently being evaluated in a phase 2 study in T-cell lymphoma (TCL) patients. Tolinapant has demonstrated evidence of single-agent clinical activity in relapsed/refractory peripheral TCL and cutaneous TCL. To investigate the mechanism of action underlying the single-agent activity observed in the clinic, we have used a comprehensive translational approach integrating in vitro and in vivo models of TCL confirmed by data from human tumor biopsies. Here, we show that tolinapant acts as an efficacious immunomodulatory molecule capable of inducing complete tumor regression in a syngeneic model of TCL exclusively in the presence of an intact immune system. These findings were confirmed in samples from our ongoing clinical study showing that tolinapant treatment can induce changes in gene expression and cytokine profile consistent with immune modulation. Mechanistically, we show that tolinapant can activate both the adaptive and the innate arms of the immune system through the induction of immunogenic forms of cell death. In summary, we describe a novel role for IAP antagonists as immunomodulatory molecules capable of promoting a robust antitumor immune response in TCL.

Background DNA methyltransferase inhibitors (DNMTis) improve survival for patients with myelodysplastic syndromes (MDS) and those with acute myeloid leukemia (AML) unable to receive standard cytotoxic chemotherapy and are, accordingly, the backbone of standard-of-care treatment for these conditions. Standard regimens with DNMTIs, decitabine (DEC) or azacitidine (AZA) include daily subcutaneous (s.c.) or intravenous (i.v.) administration for 5–7 consecutive days. Attempts to provide the therapy orally have been limited given rapid clearance of the agents by the enzyme cytidine deaminase (CDA), which is ubiquitous in the gut and liver as part of first-pass metabolism. Recently, cedazuridine (CDZ), an oral inhibitor of CDA, was successfully combined with DEC to approximate the pharmacokinetics of i.v. DEC in patients. Objective To determine if an oral dosing strategy might be feasible in the clinic with AZA, we attempted to increase the bioavailability of oral AZA through the use of CDZ, in a murine model. Methods Following pharmacokinetic and pharmacodynamic assessment of oral AZA dosed with CDZ in murine and monkey models, we tested this regimen in vivo with a human cell line-derived xenograft transplantation experiment (CDX). Following this we combined the regimen with venetoclax (VEN) to test the efficacy of an all-oral regimen in a patient-derived xenograft (PDX) model. Results Parenteral AZA and oral AZA + CDZ exhibited similar pharmacokinetic profiles, and efficacy against human AML cells. Tumor regression was seen with AZA + CDZ in MOLM-13 CDX and PDX models. Conclusions We conclude that oral AZA when combined with CDZ achieves successful tumor regression in both CDX and PDX models. Furthermore, the combination of AZA + CDZ with VEN in a PDX model emulated responses seen with VEN + AZA in the clinic, implying a potential all-oral VEN-based therapy opportunity in myeloid diseases.

Purpose: Platinum resistance in ovarian cancer is associated with epigenetic modifications. Hypomethylating agents (HMA) have been studied as carboplatin resensitizing agents in ovarian cancer. This randomized phase II trial compared guadecitabine, a second-generation HMA, and carboplatin (G+C) against second-line chemotherapy in women with measurable or detectable platinum-resistant ovarian cancer. Patients and Methods: Patients received either G+C (guadecitabine 30 mg/m2 s.c. once-daily for 5 days and carboplatin) or treatment of choice (TC; topotecan, pegylated liposomal doxorubicin, paclitaxel, or gemcitabine) in 28-day cycles until progression or unacceptable toxicity. The primary endpoint was progression-free survival (PFS); secondary endpoints were RECIST v1.1 and CA-125 response rate, 6-month PFS, and overall survival (OS). Results: Of 100 patients treated, 51 received G+C and 49 received TC, of which 27 crossed over to G+C. The study did not meet its primary endpoint as the median PFS was not statistically different between arms (16.3 weeks vs. 9.1 weeks in the G+C and TC groups, respectively; P = 0.07). However, the 6-month PFS rate was significantly higher in the G+C group (37% vs. 11% in TC group; P = 0.003). The incidence of grade 3 or higher toxicity was similar in G+C and TC groups (51% and 49%, respectively), with neutropenia and leukopenia being more frequent in the G+C group. Conclusions: Although this trial did not show superiority for PFS of G+C versus TC, the 6-month PFS increased in G+C treated patients. Further refinement of this strategy should focus on identification of predictive markers for patient selection.

Summary Background Guadecitabine is a next-generation hypomethylating agent whose active metabolite decitabine has a longer in-vivo exposure time than intravenous decitabine. More effective hypomethylating agents are needed for the treatment of myelodysplastic syndromes. In the present study, we aimed to compare the activity and safety of two doses of guadecitabine in hypomethylating agent treatment-naive or relapsed or refractory patients with intermediate-risk or high-risk myelodysplastic syndromes. Methods This phase 2 part of the phase 1/2, randomised, open-label study enrolled patients aged 18 years or older from 14 North American medical centres with International Prognostic Scoring System intermediate-1-risk, intermediate-2-risk, or high-risk myelodysplastic syndromes, or chronic myelomonocytic leukaemia. They were either hypomethylating agent treatment-naive or had relapsed or refractory disease after previous hypomethylating agent treatment as determined by the investigators' judgment. Eligible patients had Eastern Cooperative Oncology Group performance status of 0–2. Patients were randomly assigned (1:1) using a computer algorithm for dynamic randomisation to subcutaneous guadecitabine 60 or 90 mg/m2 on days 1–5 of a 28-day treatment cycle. Treatment was stratified by previous treatment with hypomethylating agents and neither patients nor investigators were masked. The primary endpoint was overall response (a composite of complete response, partial response, marrow complete response, and haematological improvement) assessed in all patients who received at least one dose of study drug. This study is registered with ClinicalTrials.gov, number NCT01261312. Findings Between July 9, 2012, and April 7, 2014, 105 patients were enrolled: 55 (52%) were allocated to guadecitabine 60 mg/m2 (28 patients were treatment-naive and 27 had relapsed or refractory disease after previous hypomethylating agent treatment) and 50 (48%) patients to 90 mg/m2 (23 patients were treatment-naive and 27 had relapsed or refractory disease). Three (3%) patients of 105 did not receive study treatment and were excluded from analyses. Median follow-up was 3·2 years (IQR 2·8–3·5). The proportion of patients achieving an overall response did not significantly differ between dose groups (21 of 53 [40%, 95% CI 27–54] with 60 mg/m2 and 27 of 49 [55%, 95% CI 40–69] with 90 mg/m2; p=0·16). 25 of 49 (51%, 95% CI 36–66) patients who were treatment-naive and 23 of 53 (43%, 30–58) patients with relapsed or refractory disease achieved an overall response. The most common grade 3 or worse adverse events in both groups, regardless of relationship to treatment, were thrombocytopenia (22 [41%] of 53 patients in the 60 mg/m2 group and 28 [57%] of 49 in the 90 mg/m2 group), neutropaenia (21 [40%] and 25 [51%]), anaemia (25 [47%] and 24 [49%]), febrile neutropaenia (17 [32%] and 21 [43%]), and pneumonia (13 [25%] and 15 [31%]). Seven (7%) of 102 patients died due to adverse events (three with 90 mg/m2 and four with 60 mg/m2), and all except one were in the relapsed or refractory cohort. Two deaths were deemed treatment related (septic shock with 60 mg/m2; pneumonia with 90 mg/m2). Interpretation Guadecitabine was clinically active with acceptable tolerability in patients with intermediate-risk and high-risk myelodysplastic syndromes. Responses and overall survival in the relapsed or refractory cohort offer the potential of a new therapeutic option for patients for whom currently available hypomethylating agents are not successful. We therefore recommend guadecitabine at a dose of 60 mg/m2 on a 5-day schedule for these patients. Funding Astex Pharmaceuticals and Stand Up To Cancer.

9085 Background: Aberrant activation of the RAS-RAF-MEK-ERK pathway is common in human cancers. This is an open-label Phase 1 study of ASTX029, a dual-mechanism extracellular signal-regulated kinase 1/2 (ERK1/2) inhibitor, in subjects with relapsed/refractory solid tumors (NCT03520075). Methods: The primary objective is to identify a recommended Phase 2 dose. Subjects with relapsed/refractory solid tumors were eligible for Phase 1A with any molecular feature and for Phase 1B if the tumor demonstrated RAS or BRAF mutations. ASTX029 was administered orally daily on a continuous basis in 21-day cycles. Phase 1A was a modified 3+3 dose-escalation design based on dose-limiting toxicity (DLT) events. Phase 1B subjects were treated at the recommended dose for expansion (RDE) based on emerging safety, pharmacokinetic (PK), and pharmacodynamic (PD) data. Disease response was evaluated by RECIST v1.1. Results: 76 subjects were treated with at least one dose of ASTX029 in Phase 1A (n = 56) and Phase 1B (n = 20). In Phase 1A, ASTX029 was evaluated from 10 mg to 280 mg daily. Two subjects experienced grade 2 central serous retinopathy (CSR) within a few days of dosing at the 280 mg daily dose level (one event was declared a DLT). Both subjects recovered to baseline within days of dose interruption. CSR is an expected AE based on the class of drugs. At the selected RDE dose level of 200 mg daily, the mean PK exposure was 109% of target exposure (13,022 ng*hr/ml), defined as the level expected to have biological activity based on mouse models. As of the data cut-off of February 7, 2022, the most frequent grade ≥2 AEs experienced by subjects (≥5%) assessed as related to ASTX029 included ocular AEs (n = 6: all Grade 2); nausea (n = 7: all Grade 2); diarrhea (n = 6: 5 Grade 2, 1 Grade 3); fatigue (n = 4: all Grade 2); rash (n = 4, 3 Grade 2, 1 Grade 3). There were 52 serious AEs, all unrelated to ASTX029 except for one subject with Grade 3 malaise. Four subjects had a partial response, including KRAS-G12A BRAF-D549N non-small cell lung cancer (NSCLC; Phase 1A: 120 mg treated 20.0 months); KRAS-G12D pancreatic cancer (Phase 1A: 200 mg treated 2.1 months); KRAS-G13D NSCLC (Phase 1B; treated 10.6 months); KRAS-G12S NSCLC (Phase 1B; treated 10.4 months and ongoing). In all, two partial responses were observed out of 3 NSCLC subjects enrolled in Phase 1B. Phospho-ERK and phospho-RSK were evaluated for PD effect on fresh tumor biopsies obtained at baseline and cycle 2. A PD effect and decreased cell proliferation (Ki-67) were observed in 6 of 9 and 3 of 8 evaluable Phase 1B samples, respectively. The most common reason for ASTX029 discontinuation was disease progression. Conclusions: This Phase 1 study of the ERK1/2 inhibitor ASTX029 has identified a dose level of 200 mg daily continuously for investigation in the Phase 2 study. PK and PD data suggest target exposures are achieved with preliminary clinical activity, especially in KRAS-mutated NSCLC. Clinical trial information: NCT03520075.

High-grade serous ovarian cancer (HGSOC) harbours aberrant epigenetic features, including DNA methylation. In this study we delineate pathways and networks altered by DNA methylation and associated with HGSOC initiation and progression to a platinum-resistant state. By including tumours from patients who had been treated with the hypomethylating agent (HMA) guadecitabine, we also addressed the role of HMAs in treatment of HGSOC. Tumours from patients with primary (platinum-naïve) HGSOC (n = 20) were compared to patients with recurrent platinum-resistant HGSOC and enrolled in a recently completed clinical trial (NCT01696032). Human ovarian surface epithelial cells (HOSE; n = 5 samples) served as normal controls. Genome-wide methylation profiles were determined. DNA methyltransferase (DNMT) expression levels were examined by immunohistochemistry and correlated with clinical outcomes. Cancer-related and tumorigenesis networks were enriched among differentially methylated genes (DMGs) in primary OC vs. HOSE. When comparing platinum-resistant and primary tumours, 452 CpG island (CGI)-containing gene promoters acquired DNA methylation; of those loci, decreased (P

Purpose Germ cell tumors (GCTs) are cured with therapy based on cisplatin, although a clinically significant number of patients are refractory and die of progressive disease. Based on preclinical studies indicating that refractory testicular GCTs are hypersensitive to hypomethylating agents (HMAs), we conducted a phase I trial combining the next‐generation HMA guadecitabine (SGI‐110) with cisplatin in recurrent, cisplatin‐resistant GCT patients. Methods Patients with metastatic GCTs were treated for five consecutive days with guadecitabine followed by cisplatin on day 8, for a 28‐day cycle for up to six cycles. The primary endpoint was safety and toxicity including dose‐limiting toxicity (DLT) and maximum tolerated dose (MTD). Results The number of patients enrolled was 14. The majority of patients were heavily pretreated. MTD was determined to be 30 mg/m2 guadecitabine followed by 100 mg/m2 cisplatin. The major DLTs were neutropenia and thrombocytopenia. Three patients had partial responses by RECIST criteria, two of these patients, including one with primary mediastinal disease, completed the study and qualified as complete responses by serum tumor marker criteria with sustained remissions of 5 and 13 months and survival of 16 and 26 months, respectively. The overall response rate was 23%. Three patients also had stable disease indicating a clinical benefit rate of 46%. Conclusions The combination of guadecitabine and cisplatin was tolerable and demonstrated activity in patients with platinum refractory germ cell cancer., A phase I trial demonstrates tolerable toxicity and clinical activity for combining the hypomethylating agent guadecitabine with cisplatin for testicular cancer patients that have failed prior chemotherapy. This strategy has the potential to be the first targeted treatment for chemotherapy refractory testicular cancer.

Ovarian cancer (OC) cells frequently metastasize to the omentum, and adipocytes play a significant role in ovarian tumor progression. Therapeutic interventions targeting aberrant DNA methylation in ovarian tumors have shown promise in the clinic, but the effects of epigenetic therapy on the tumor microenvironment are understudied. Here, we examined the effect of adipocytes on OC cell behavior in culture and impact of targeting DNA methylation in adipocytes on OC metastasis. The presence of adipocytes increased OC cell migration and invasion, and proximal and direct coculture of adipocytes increased OC proliferation alone or after treatment with carboplatin. Treatment of adipocytes with hypomethylating agent guadecitabine decreased migration and invasion of OC cells toward adipocytes. Subcellular protein fractionation of adipocytes treated with guadecitabine revealed decreased DNA methyltransferase 1 (DNMT1) levels even in the presence of DNA synthesis inhibitor, aphidicolin. Methyl-Capture- and RNA-sequencing analysis of guadecitabine-treated adipocytes revealed derepression of tumor-suppressor genes and epithelial–mesenchymal transition inhibitors. SUSD2, a secreted tumor suppressor downregulated by promoter CpG island methylation in adipocytes, was upregulated after guadecitabine treatment, and recombinant SUSD2 decreased OC cell migration and invasion. Integrated analysis of the methylomic and transcriptomic data identified pathways associated with inhibition of matrix metalloproteases and fatty acid α-oxidation, suggesting a possible mechanism of how epigenetic therapy of adipocytes decreases metastasis. In conclusion, the effect of DNMT inhibitor on fully differentiated adipocytes suggests that hypomethylating agents may affect the tumor microenvironment to decrease cancer cell metastasis. Implications: Epigenetic targeting of tumor microenvironment can affect metastatic behavior of ovarian cancer cells. Mol Cancer Res; 16(8); 1226–40. ©2018 AACR.

Purpose: PARP inhibitors (PARPi) are primarily effective against BRCA1/2-mutated breast and ovarian cancers, but resistance due to reversion of mutated BRCA1/2 and other mechanisms is common. Based on previous reports demonstrating a functional role for DNMT1 in DNA repair and our previous studies demonstrating an ability of DNA methyltransferase inhibitor (DNMTi) to resensitize tumors to primary therapies, we hypothesized that combining a DNMTi with PARPi would sensitize PARPi-resistant breast and ovarian cancers to PARPi therapy, independent of BRCA status. Experimental Design: Breast and ovarian cancer cell lines (BRCA-wild-type/mutant) were treated with PARPi talazoparib and DNMTi guadecitabine. Effects on cell survival, ROS accumulation, and cAMP levels were examined. In vivo, mice bearing either BRCA-proficient breast or ovarian cancer cells were treated with talazoparib and guadecitabine, alone or in combination. Tumor progression, gene expression, and overall survival were analyzed. Results: Combination of guadecitabine and talazoparib synergized to enhance PARPi efficacy, irrespective of BRCA mutation status. Coadministration of guadecitabine with talazoparib increased accumulation of ROS, promoted PARP activation, and further sensitized, in a cAMP/PKA-dependent manner, breast and ovarian cancer cells to PARPi. In addition, DNMTi enhanced PARP “trapping” by talazoparib. Guadecitabine plus talazoparib decreased xenograft tumor growth and increased overall survival in BRCA-proficient high-grade serous ovarian and triple-negative breast cancer models. Conclusions: The novel combination of the next-generation DNMTi guadecitabine and the first-in-class PARPi talazoparib inhibited breast and ovarian cancers harboring either wild-type– or mutant-BRCA, supporting further clinical exploration of this drug combination in PARPi-resistant cancers. Clin Cancer Res; 24(13); 3163–75. ©2018 AACR.

Abstract text: Background/Introduction: Chronic Myelomonocytic Leukemia (CMML) is an uncommon MDS/MPN overlap syndrome that has historically been included under the umbrella of myelodysplastic syndromes (MDS) for clinical trial and treatment. As a result, DNA methyltransferase inhibitors (DNMTi) such as decitabine or azacitidine have been the established standard of care for the treatment of CMML. The oral bioavailability of these agents has been limited due to rapid degradation by cytidine deaminase (CDA) in the gut and liver so treatment has required intravenous infusion or subcutaneous injections daily for 5-7 days every month (m) adding significant burden to older cancer patients due to daily time commitment and travel to treatment centers. In the context of pandemic SARS-CoV-2, parenteral therapy also increases contact with medical settings with increased infection risk. Oral decitabine 35 mg/cedazuridine 100 mg (ASTX727) is an oral fixed dose combination of decitabine and the CDA inhibitor cedazuridine that produced equivalent exposure (99%; 90% CI 93% to 106%) to IV decitabine 20 mg/m 2 in a randomized cross-over study (Garcia-Manero et al, ASH 2019), and Median overall survival (mOS) for the entire study population in the ASCERTAIN study was approximately 32 months (Savona, 2021). Here, we present outcome data for this study for the enrolled subpopulation of patients with CMML. Methods: We used a randomized cross over design in which patients were randomized in the first 2 cycles 1:1 to either Sequence A: (decitabine 35 mg/ cedazuridine 100 mg in Cycle 1 followed by IV decitabine at 20 mg/m 2 in Cycle 2), or Sequence B: (IV decitabine in Cycle 1 followed by oral decitabine/cedazuridine in Cycle 2). We conducted an intra-patient comparison of decitabine PK (primary PK endpoint: decitabine AUC equivalence over 5 days of dosing). Cycles were repeated every 28 days (unless delays were needed). All patients received oral decitabine/cedazuridine in Cycles 3 and above until disease progression or unacceptable toxicity. Patients were eligible per the FDA-approved label of IV decitabine (MDS patients by FAB classification including CMML, or MDS IPSS Intermediate-1, 2 or high-risk patients). Clinical endpoints were best response according to International Working Group (IWG) 2006 response criteria, transfusion independence for at least 8 or 16 consecutive weeks, overall survival, and safety. Adverse events (AEs) were graded by Common Terminology Criteria for Adverse Events (CTCAE) v 4.03. Results: Of the 133 patients enrolled and treated in ASCERTAIN, 16 (12%) had a diagnosis of CMML with demographics and as follows: median age 71.5 years, 69% Male/31% Female, median weight 87kg (range 65-124), 25% ECOG 0, 75% ECOG 1. Population disease characteristics were: 19% poor or intermediate risk cytogenetics, with median baseline hemoglobin 90 g/L, neutrophils 1.27 X 10 9/L, platelets 84 x 10 9/L, bone marrow blasts 5%, with 38% RBC transfusion dependent. Patients received a median of 7 cycles of therapy (range 3-24). Treatment-emergent adverse events of CTCAE Grade 3 or higher in > 10% of patients, independent of relationship to ASTX727, were cytopenias (neutropenia [69%], thrombocytopenia [63%], anemia [56%], leukopenia [19%]), febrile neutropenia (31%), fatigue (13%). Two patients (12.5%) had Complete Responses (CR), 8 (50%) had marrow CR ([mCR], including 3 (19%) with hematologic improvement (HI); Overall Response rate (ORR) [CR + PR+ mCR + HI] was 75%. Of six patients with baseline RBC transfusion dependence 3 (50%) became transfusion independent. Leukemia-free survival was 28.2 months and after a median follow up of more than 33 months, median overall survival had not been reached. Two patients (13%) went on to Hematopoietic Stem Cell Transplant (HCT). Conclusions: In the overall study, oral decitabine/cedazuridine delivered equivalent PK exposure to 5 days of IV decitabine 20mg/m 2 with a resultant clinical activity safety and efficacy profile in CMML patients consistent with the published literature (e.g Zeidan, et al 2017) and the Phase 2 experience. The use of oral decitabine/cedazuridine is a reasonable approach in CMML patients. References: Garcia-Manero, et al ASH 2019 Savona, et al, Int. MDS Symposium, 2021 Zeidan, et al, Cancer 2017: 3754-3762. Figure 1 Figure 1. Disclosures Savona: Geron: Consultancy, Membership on an entity's Board of Directors or advisory committees; CTI: Consultancy, Membership on an entity's Board of Directors or advisory committees; Karyopharm: Consultancy, Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees; BMS-Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; NOVARTIS: Consultancy, Membership on an entity's Board of Directors or advisory committees; Ryvu: Consultancy, Membership on an entity's Board of Directors or advisory committees; Sierra Oncology: Consultancy, Membership on an entity's Board of Directors or advisory committees; Taiho: Consultancy, Membership on an entity's Board of Directors or advisory committees; TG Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; ALX Oncology: Research Funding; Astex: Research Funding; Incyte: Research Funding. McCloskey: Pfizer: Consultancy; Takeda: Consultancy, Speakers Bureau; Incyte: Speakers Bureau; Novartis: Consultancy; COTA: Other: Equity Ownership; BMS: Honoraria, Speakers Bureau; Amgen: Speakers Bureau; Jazz: Consultancy, Speakers Bureau. Griffiths: Boston Biomedical: Consultancy; Celgene/Bristol-Myers Squibb: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Honoraria; Taiho Oncology: Consultancy, Honoraria; Genentech: Research Funding; Astex Pharmaceuticals: Honoraria, Research Funding; Takeda Oncology: Consultancy, Honoraria; Novartis: Honoraria; Apellis Pharmaceuticals: Research Funding; Alexion Pharmaceuticals: Consultancy, Research Funding. Yee: Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Forma Therapeutics: Research Funding; Geron: Research Funding; Shattuck Labs: Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb/Celgene: Membership on an entity's Board of Directors or advisory committees; F. Hoffmann La Roche: Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Honoraria; Janssen: Research Funding; Onconova: Research Funding; Genentech: Research Funding; Otsuka: Membership on an entity's Board of Directors or advisory committees; MedImmune: Research Funding; Jazz: Research Funding; Astex: Membership on an entity's Board of Directors or advisory committees, Research Funding; Tolero: Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees; TaiHo: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; Paladin: Membership on an entity's Board of Directors or advisory committees. Zeidan: BeyondSpring: Consultancy; Janssen: Consultancy; Boehringer Ingelheim: Consultancy, Research Funding; BioCryst: Other: Clinical Trial Committees; AstraZeneca: Consultancy; Pfizer: Other: Travel support, Research Funding; Kura: Consultancy, Other: Clinical Trial Committees; Incyte: Consultancy, Research Funding; Ionis: Consultancy; Daiichi Sankyo: Consultancy; Epizyme: Consultancy; Novartis: Consultancy, Other: Clinical Trial Committees, Travel support, Research Funding; Loxo Oncology: Consultancy, Other: Clinical Trial Committees; Genentech: Consultancy; Geron: Other: Clinical Trial Committees; Cardiff Oncology: Consultancy, Other: Travel support, Research Funding; BMS: Consultancy, Other: Clinical Trial Committees, Research Funding; Gilead: Consultancy, Other: Clinical Trial Committees; Aprea: Consultancy, Research Funding; Astellas: Consultancy; Astex: Research Funding; Jazz: Consultancy; Jasper: Consultancy; Amgen: Consultancy, Research Funding; Agios: Consultancy; ADC Therapeutics: Research Funding; Acceleron: Consultancy, Research Funding; AbbVie: Consultancy, Other: Clinical Trial Committees, Research Funding. Al-Kali: Novartis: Research Funding; Astex: Other: Research support to institution. Patel: Agios: Membership on an entity's Board of Directors or advisory committees; Celgene-BMS: Membership on an entity's Board of Directors or advisory committees; PVI: Honoraria. Sabloff: Takeda: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; TaiHo: Membership on an entity's Board of Directors or advisory committees; Jaxx: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; ROCHE: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees. Dao: Astex Pharmaceuticals, Inc.: Current Employment. Fazal: Janssen Oncology: Consultancy, Honoraria, Speakers Bureau; Taiho Pharmaceuticals: Consultancy, Honoraria, Speakers Bureau; Gilead Sciences: Consultancy, Honoraria, Speakers Bureau; Novartis: Consultancy, Honoraria, Speakers Bureau; Agios: Consultancy, Honoraria, Speakers Bureau; Sanofi Genzyme: Consultancy, Honoraria, Speakers Bureau; Takeda: Consultancy, Honoraria, Speakers Bureau; Glaxo Smith Kline: Consultancy, Honoraria, Speakers Bureau; AMGEN: Consultancy, Honoraria, Speakers Bureau; Incyte: Consultancy, Honoraria, Speakers Bureau; Jazz Pharmaceuticals: Consultancy, Honoraria, Speakers Bureau; Bristol Myers Squibb: Consultancy, Honoraria, Speakers Bureau; Stemline Therapeutics: Consultancy, Honoraria, Speakers Bureau; Karyopharm Pharmaceuticals: Consultancy, Honoraria, Speakers Bureau. Odenike: Celgene, Incyte, AstraZeneca, Astex, NS Pharma, AbbVie, Gilead, Janssen, Oncotherapy, Agios, CTI/Baxalta, Aprea: Research Funding; AbbVie, Celgene, Impact Biomedicines, Novartis, Taiho Oncology, Takeda: Consultancy. Kantarjian: Ipsen Pharmaceuticals: Honoraria; Astra Zeneca: Honoraria; Astellas Health: Honoraria; Aptitude Health: Honoraria; Pfizer: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Jazz: Research Funding; Immunogen: Research Funding; Daiichi-Sankyo: Research Funding; BMS: Research Funding; Ascentage: Research Funding; Amgen: Honoraria, Research Funding; AbbVie: Honoraria, Research Funding; KAHR Medical Ltd: Honoraria; NOVA Research: Honoraria; Precision Biosciences: Honoraria; Taiho Pharmaceutical Canada: Honoraria. DeZern: Bristol-Myers Squibb: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Taiho: Consultancy, Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees. Roboz: Janssen: Research Funding; AbbVie: Consultancy; Actinium: Consultancy; Agios: Consultancy; Amgen: Consultancy; Astex: Consultancy; Astellas: Consultancy; AstraZeneca: Consultancy; Bayer: Consultancy; Blueprint Medicines: Consultancy; Bristol Myers Squibb: Consultancy; Celgene: Consultancy; Daiichi Sankyo: Consultancy; Glaxo SmithKline: Consultancy; Helsinn: Consultancy; Janssen: Consultancy; Jasper Therapeutics: Consultancy; Jazz: Consultancy; MEI Pharma - IDMC Chair: Consultancy; Mesoblast: Consultancy; Novartis: Consultancy; Otsuka: Consultancy; Pfizer: Consultancy; Roche/Genentech: Consultancy. Busque: Novartis: Consultancy. Leber: Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pfizer: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; AMGEN: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; TaiHo: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Otsuka: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Astellas: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jazz: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Hao: Astex Pharmaceuticals, Inc.: Current Employment. Keer: Astex Pharmaceuticals, Inc.: Current Employment. Azab: Astex Pharmaceuticals, Inc.: Membership on an entity's Board of Directors or advisory committees.

Background/Introduction: Lower-risk (IPSS low risk and Int-1) myelodysplastic syndromes (MDS) are typically treated supportively to address cytopenias. DNA methyltransferase inhibitors (DNMTi) such as azacitidine and decitabine (DEC) are FDA-approved for higher risk MDS patients (pts), and while the DEC USPI includes IPSS Int-1 pts, it is not widely used in this population. Approved intravenous (IV) or subcutaneous (SC) regimens require 5-7 days of treatment every month burdening older cancer pts due to daily travel and treatment time and may increase potential risk from pandemic SARS-CoV-2 infection. Because DNMTis are rapidly degraded by cytidine deaminase (CDA) in the gut and liver, oral availability has only been recently possible. A randomized study with CC-486, an oral formulation of azacitidine, in the Int-1 population showed a median overall survival (mOS) of approximately 17 months for both placebo and treated patients (Garcia-Manero, 2021). Oral DEC 35 mg/cedazuridine 100 mg (ASTX727) or DEC-C, is an oral fixed dose combination (FDC) of DEC and the CDA inhibitor cedazuridine (CED) resulting in equivalent exposure (99%; 90% CI 93% to 106%) to standard IV DEC 20 mg/m 2 for 5 days in an intra-patient randomized cross-over study (Garcia-Manero et al, ASH 2019). Here, we present data on patients with lower risk MDS from that study. Methods: We used a randomized cross over design with pts randomized 1:1 in the first 2 cycles to either Sequence A: (DEC 35 mg/ CED 100 mg in Cycle 1 and IV DEC at 20 mg/m 2 in Cycle 2), or Sequence B (IV DEC in Cycle 1 and oral DEC/CED in Cycle 2). Cycles were repeated every 28 days unless delays were needed, and all patients received oral DEC-C in Cycles 3+ until disease progression or unacceptable toxicity. We conducted an intra-patient comparison of DEC PK (DEC AUC equivalence over 5 days of dosing). Pts were eligible as per the FDA-approved label of IV DEC (MDS pts by FAB classification including CMML, or MDS IPSS Intermediate-1, 2 or high-risk pts). Clinical endpoints were best response as assessed by an independent expert panel according to IWG 2006 response criteria, transfusion independence (TI), overall survival (OS), and safety. Results: Of the 133 pts treated in ASCERTAIN, 69 had a diagnosis of lower-risk MDS (93% Int-1, 7% LR). Median age was 70.0 years (range 45-87), 65% were male, median weight was 84 kg (range 50-127), median baseline hematologic parameters were: hemoglobin 89 g/L (range 69.8-146.5), WBCs 1.50 X 10 9/L (range 0.11-7.1), platelets (plt) 86 x 10 9/L (range 5-703), bone marrow blasts 4% (range 0-18), cytogenetics: 7 (10.1%) poor-risk, 21 (30.4%) intermediate risk, 37 (53.6%) better-risk, 4 (5.7%) missing or not evaluable. 27(39%) of the pts were RBC transfusion dependent (TD) and 6 (9%) plt TD. 17 (25%) had received prior MDS treatment, 3% prior DNMTi. Pts received a median of 9 cycles of therapy (range 1-28). Treatment-emergent adverse events of CTCAE Gr 3 or higher in >10% of pts, independent of relationship to ASTX727, included cytopenias (neutropenia [59%], thrombocytopenia [58%], anemia [48%], leukopenia [26%]), febrile neutropenia (32%), and pneumonia (19%). Sixteen pts (23%) achieved Complete Response (CR), 18 (26%) had marrow CR (mCR), including 9 (13%) with hematologic improvement (HI). Overall Response rate (ORR; CR + PR+ mCR + HI) was 57%. Of those RBC or plt TD at baseline, 13 (48%) became RBC TI and 4 (67%) became plt TI. With approximately 32 months of median follow up, neither median leukemia-free survival (mLFS) nor mOS had been reached (Figure 1). Twelve pts (17%) went on to allogeneic stem cell transplant. Conclusions: Oral decitabine/cedazuridine given as a FDC in MDS pts produced equivalent PK exposure to 20 mg/m 2 IV DEC; in lower risk MDS pts with treatment indicated, the agent was generally well-tolerated with prolonged treatment and could result in mLFS and mOS which exceeds 32 months. This FDC and other dosing regimens of oral DEC-C should be further studied in this patient population. References: Garcia-Manero, et al, ASH 2019 Savona, et al, Int. MDS Symp. 2021 Garcia-Manero, et al, Phase III, Randomized, Placebo-Controlled Trial of CC-486 (Oral Azacitidine) in Patients with Lower-Risk Myelodysplastic Syndromes. J.Clin.Onc. 2021 39:13, 1426-1436 Figure 1 Figure 1. Disclosures McCloskey: Pfizer: Consultancy; Jazz: Consultancy, Speakers Bureau; COTA: Other: Equity Ownership; Incyte: Speakers Bureau; Takeda: Consultancy, Speakers Bureau; Novartis: Consultancy; BMS: Honoraria, Speakers Bureau; Amgen: Speakers Bureau. Griffiths: Alexion Pharmaceuticals: Consultancy, Research Funding; Abbvie: Consultancy, Honoraria; Taiho Oncology: Consultancy, Honoraria; Genentech: Research Funding; Novartis: Honoraria; Takeda Oncology: Consultancy, Honoraria; Astex Pharmaceuticals: Honoraria, Research Funding; Celgene/Bristol-Myers Squibb: Consultancy, Honoraria, Research Funding; Apellis Pharmaceuticals: Research Funding; Boston Biomedical: Consultancy. Yee: Paladin: Membership on an entity's Board of Directors or advisory committees; TaiHo: Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Genentech: Research Funding; Geron: Research Funding; Janssen: Research Funding; Jazz: Research Funding; MedImmune: Research Funding; Onconova: Research Funding; Tolero: Research Funding; AbbVie: Honoraria; Bristol-Myers Squibb/Celgene: Membership on an entity's Board of Directors or advisory committees; Otsuka: Membership on an entity's Board of Directors or advisory committees; Shattuck Labs: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees; F. Hoffmann La Roche: Membership on an entity's Board of Directors or advisory committees, Research Funding; Forma Therapeutics: Research Funding; Astex: Membership on an entity's Board of Directors or advisory committees, Research Funding. Zeidan: Novartis: Consultancy, Other: Clinical Trial Committees, Travel support, Research Funding; Genentech: Consultancy; Ionis: Consultancy; Astellas: Consultancy; Epizyme: Consultancy; AbbVie: Consultancy, Other: Clinical Trial Committees, Research Funding; Jasper: Consultancy; Cardiff Oncology: Consultancy, Other: Travel support, Research Funding; BeyondSpring: Consultancy; Loxo Oncology: Consultancy, Other: Clinical Trial Committees; Janssen: Consultancy; Acceleron: Consultancy, Research Funding; AstraZeneca: Consultancy; Kura: Consultancy, Other: Clinical Trial Committees; Gilead: Consultancy, Other: Clinical Trial Committees; Agios: Consultancy; Daiichi Sankyo: Consultancy; Boehringer Ingelheim: Consultancy, Research Funding; Geron: Other: Clinical Trial Committees; BMS: Consultancy, Other: Clinical Trial Committees, Research Funding; BioCryst: Other: Clinical Trial Committees; Pfizer: Other: Travel support, Research Funding; Aprea: Consultancy, Research Funding; ADC Therapeutics: Research Funding; Jazz: Consultancy; Incyte: Consultancy, Research Funding; Amgen: Consultancy, Research Funding; Astex: Research Funding. Al-Kali: Astex: Other: Research support to institution; Novartis: Research Funding. Patel: Celgene-BMS: Membership on an entity's Board of Directors or advisory committees; PVI: Honoraria; Agios: Membership on an entity's Board of Directors or advisory committees. Sabloff: Pfizer: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees; ROCHE: Membership on an entity's Board of Directors or advisory committees; TaiHo: Membership on an entity's Board of Directors or advisory committees; Jaxx: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees. Dao: Astex Pharmaceuticals, Inc.: Current Employment. Fazal: Taiho Pharmaceuticals: Consultancy, Honoraria, Speakers Bureau; Stemline Therapeutics: Consultancy, Honoraria, Speakers Bureau; Sanofi Genzyme: Consultancy, Honoraria, Speakers Bureau; Novartis: Consultancy, Honoraria, Speakers Bureau; Karyopharm Pharmaceuticals: Consultancy, Honoraria, Speakers Bureau; Jazz Pharmaceuticals: Consultancy, Honoraria, Speakers Bureau; Janssen Oncology: Consultancy, Honoraria, Speakers Bureau; Incyte: Consultancy, Honoraria, Speakers Bureau; Glaxo Smith Kline: Consultancy, Honoraria, Speakers Bureau; Gilead Sciences: Consultancy, Honoraria, Speakers Bureau; Bristol Myers Squibb: Consultancy, Honoraria, Speakers Bureau; AMGEN: Consultancy, Honoraria, Speakers Bureau; Agios: Consultancy, Honoraria, Speakers Bureau; Takeda: Consultancy, Honoraria, Speakers Bureau. Odenike: AbbVie, Celgene, Impact Biomedicines, Novartis, Taiho Oncology, Takeda: Consultancy; Celgene, Incyte, AstraZeneca, Astex, NS Pharma, AbbVie, Gilead, Janssen, Oncotherapy, Agios, CTI/Baxalta, Aprea: Research Funding. Kantarjian: AbbVie: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Ascentage: Research Funding; Pfizer: Honoraria, Research Funding; BMS: Research Funding; Daiichi-Sankyo: Research Funding; Amgen: Honoraria, Research Funding; Ipsen Pharmaceuticals: Honoraria; Jazz: Research Funding; Astellas Health: Honoraria; Immunogen: Research Funding; Astra Zeneca: Honoraria; Aptitude Health: Honoraria; KAHR Medical Ltd: Honoraria; NOVA Research: Honoraria; Precision Biosciences: Honoraria; Taiho Pharmaceutical Canada: Honoraria. DeZern: Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees; Taiho: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Consultancy, Membership on an entity's Board of Directors or advisory committees. Roboz: Novartis: Consultancy; Mesoblast: Consultancy; Jasper Therapeutics: Consultancy; Jazz: Consultancy; MEI Pharma - IDMC Chair: Consultancy; Daiichi Sankyo: Consultancy; Otsuka: Consultancy; Bristol Myers Squibb: Consultancy; Blueprint Medicines: Consultancy; Bayer: Consultancy; AstraZeneca: Consultancy; Astellas: Consultancy; Astex: Consultancy; Amgen: Consultancy; Agios: Consultancy; Actinium: Consultancy; AbbVie: Consultancy; Janssen: Research Funding; Celgene: Consultancy; Glaxo SmithKline: Consultancy; Helsinn: Consultancy; Janssen: Consultancy; Pfizer: Consultancy; Roche/Genentech: Consultancy. Busque: Novartis: Consultancy. Leber: Astellas: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Otsuka: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; TaiHo: Honoraria, Membership on an entity's Board of Directors or advisory committees; AMGEN: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pfizer: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jazz: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Hao: Astex Pharmaceuticals, Inc.: Current Employment. Keer: Astex Pharmaceuticals, Inc.: Current Employment. Azab: Astex Pharmaceuticals, Inc.: Membership on an entity's Board of Directors or advisory committees. Savona: Geron: Consultancy, Membership on an entity's Board of Directors or advisory committees; Karyopharm: Consultancy, Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees; CTI: Consultancy, Membership on an entity's Board of Directors or advisory committees; BMS-Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; NOVARTIS: Consultancy, Membership on an entity's Board of Directors or advisory committees; Ryvu: Consultancy, Membership on an entity's Board of Directors or advisory committees; Sierra Oncology: Consultancy, Membership on an entity's Board of Directors or advisory committees; Taiho: Consultancy, Membership on an entity's Board of Directors or advisory committees; TG Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; ALX Oncology: Research Funding; Astex: Research Funding; Incyte: Research Funding.

Introduction: The combination of a DNA methyltransferase inhibitor (DNMTi; parenteral azacitidine or decitabine) with the BCL2 inhibitor venetoclax is a newly established standard-of-care regimen for patients with newly diagnosed acute myeloid leukemia (AML) ineligible to receive intensive induction chemotherapy (DiNardo et al, 2020). Replacing the parenteral DNMTi with an oral DNMTi with equivalent exposure may provide the benefit of reducing patient and caregiver burden of chronic parenteral therapy, and may help responding patients stay on treatment longer. ASTX727 (a fixed-dose combination of decitabine 35 mg and cedazuridine 100 mg) is an oral DNMTi that provides equivalent exposure to its parenteral DNMTi at standard dosing (Savona et al, 2020) and is under evaluation in combination with venetoclax as an all-oral regimen. Methods: This is an ongoing Phase 1 study being conducted at 7 US medical centers (ClinicalTrials.gov NCT04657081). Newly diagnosed AML patients 75 years or older, or with comorbidities that preclude use of intensive induction chemotherapy are eligible. The primary objective is to evaluate the effect of ASTX727 on the PK of venetoclax. Key secondary objectives are to evaluate the effect of venetoclax on the PK of ASTX727, and to determine the safety and efficacy profile for the combination. For Cycle 2 and beyond, ASTX727 is administered orally daily on days 1-5 and venetoclax 400 mg is administered orally daily on days 1-28 of 28-day cycles. For Cycle 1, ASTX727 is given in the same dose schedule while venetoclax is given as a ramp-up on days 1 and 2 according to the venetoclax US prescribing information (USPI); therefore, the PK studies are conducted during Cycle 2. Delay of subsequent cycles and venetoclax dose modifications for hematologic toxicities and anti-fungal concomitant medications follow the venetoclax USPI. Response assessments are evaluated using the 2017 ELN criteria (Döhner et al, 2017) and the CRh criterion (complete response [CR] with partial hematologic recovery) defined as those patients achieving marrow CR criteria but not peripheral blood count criteria and demonstrating an absolute neutrophil count >500/μL and platelet >50,000/μL (Kantarjian et al, 2017). Results: At the data cut-off date of August 1, 2021, 15 AML patients have enrolled and received study treatment. Median age is 78 years (range 66 - 84) and 9 (60%) are males. Of the 12 patients with data, 2 (17%), 6 (50%), and 4 (33%) patients are in the favorable, intermediate, and adverse risk ELN categories, respectively. Of the 15 dosed patients, 6 (40%) are diagnosed with AML with myelodysplasia-related changes. The median duration of exposure is 2 cycles (range 1-5) and 1.7 months (range 0.8-5.6). The most common adverse events (AEs) of Grade 2 or higher occurring in ≥10% of patients include neutropenia (5, 33%), febrile neutropenia (2, 13%), anemia (2, 13%), thrombocytopenia (2, 13%), vomiting (2, 13%), pneumonia (2, 13%), peripheral edema (2, 13%), hypertension (2, 13%) and vascular access complication (2, 13%). There are 17 serious AEs experienced in 7 patients; a grade 3 pneumonia and a grade 3 dysphagia are the only serious AEs assessed as related to ASTX727 and/or venetoclax and both events occurred in the same patient. Both AEs were part of the patient's medical history. Two deaths have occurred to date: one patient due to rapidly progressive disease during Cycle 2 and one patient who achieved a best response of CRh transitioned to hospice due to progressive multiple myeloma. Of 9 patients with response assessments and evaluable data, 3 (33%) achieved CR and 4 (44%) achieved CRh as the best response for a composite CR+CRh rate of 78%. Preliminary PK data available from 9 patients show venetoclax exposures are not affected by coadministration of ASTX727and are similar to historical data. Exposures of decitabine and cedazuridine are consistent with the range seen in previous studies. Updated PK, safety, and efficacy data will be provided in December 2021. Conclusions: A preliminary analysis of ASTX727 and venetoclax combination therapy in patients with newly diagnosed AML unfit for intensive induction chemotherapy demonstrate expected PK data, and a similar safety and efficacy profile to the approved combination therapy of a DNMTi and venetoclax. These preliminary data suggest that an all-oral regimen of a DNMTi in combination with venetoclax is feasible and should be investigated further. Disclosures Mannis: AbbVie, Agios, Astellas Pharma, Bristol Myers Squibb, Genentech, MacroGenics, Pfizer, and Stemline: Consultancy; Astex, Forty Seven Inc/Gilead, Glycomimetics, and Jazz Pharmaceuticals: Research Funding. Griffiths: Novartis: Honoraria; Apellis Pharmaceuticals: Research Funding; Alexion Pharmaceuticals: Consultancy, Research Funding; Boston Biomedical: Consultancy; Genentech: Research Funding; Abbvie: Consultancy, Honoraria; Takeda Oncology: Consultancy, Honoraria; Astex Pharmaceuticals: Honoraria, Research Funding; Taiho Oncology: Consultancy, Honoraria; Celgene/Bristol-Myers Squibb: Consultancy, Honoraria, Research Funding. Savona: Geron: Consultancy, Membership on an entity's Board of Directors or advisory committees; Karyopharm: Consultancy, Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees; CTI: Consultancy, Membership on an entity's Board of Directors or advisory committees; BMS-Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; NOVARTIS: Consultancy, Membership on an entity's Board of Directors or advisory committees; Ryvu: Consultancy, Membership on an entity's Board of Directors or advisory committees; Sierra Oncology: Consultancy, Membership on an entity's Board of Directors or advisory committees; Taiho: Consultancy, Membership on an entity's Board of Directors or advisory committees; TG Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; ALX Oncology: Research Funding; Astex: Research Funding; Incyte: Research Funding. Odenike: Celgene, Incyte, AstraZeneca, Astex, NS Pharma, AbbVie, Gilead, Janssen, Oncotherapy, Agios, CTI/Baxalta, Aprea: Research Funding; AbbVie, Celgene, Impact Biomedicines, Novartis, Taiho Oncology, Takeda: Consultancy. Roboz: MEI Pharma - IDMC Chair: Consultancy; Amgen: Consultancy; Jazz: Consultancy; Celgene: Consultancy; Agios: Consultancy; Janssen: Consultancy; Astex: Consultancy; Daiichi Sankyo: Consultancy; Janssen: Research Funding; AstraZeneca: Consultancy; Blueprint Medicines: Consultancy; Bayer: Consultancy; Actinium: Consultancy; AbbVie: Consultancy; Jasper Therapeutics: Consultancy; Helsinn: Consultancy; Glaxo SmithKline: Consultancy; Mesoblast: Consultancy; Bristol Myers Squibb: Consultancy; Novartis: Consultancy; Astellas: Consultancy; Otsuka: Consultancy; Pfizer: Consultancy; Roche/Genentech: Consultancy. Dillingham: Astex Pharmaceuticals, Inc.: Current Employment. Wason: Astex Pharmaceuticals, Inc.: Current Employment. Zhu: Astex Pharmaceuticals, Inc.: Current Employment. Chan: Astex Pharmaceuticals, Inc.: Current Employment. Keer: Astex Pharmaceuticals, Inc.: Current Employment. Oganesian: Astex Pharmaceuticals, Inc.: Current Employment. Dao: Astex Pharmaceuticals, Inc.: Current Employment. DiNardo: AbbVie: Consultancy, Research Funding; Agios/Servier: Consultancy, Honoraria, Research Funding; Novartis: Honoraria; Takeda: Honoraria; Notable Labs: Current holder of stock options in a privately-held company, Membership on an entity's Board of Directors or advisory committees; ImmuneOnc: Honoraria, Research Funding; GlaxoSmithKline: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Honoraria, Research Funding; Foghorn: Honoraria, Research Funding; Forma: Honoraria, Research Funding; Celgene, a Bristol Myers Squibb company: Honoraria, Research Funding. OffLabel Disclosure: 1. Inqovi (35 mg decitabine and 100 mg cedazuridine) is a prescription medicine approved in the United States to treat adults with myelodysplastic syndromes and chronic myelomonocytic leukemia. In this study, Inqovi is referred as ASTX727 due to the off-label investigational use in combination with venetoclax in adults with newly diagnosed acute myeloid leukemia 75 years or older, or who have comorbidities that preclude use of intensive induction chemotherapy. 2. Venclexta is a prescription medicine approved in the United States for: 1) adults with chronic lymphocytic leukemia or small lymphocytic lymphoma; 2) adults with newly diagnosed acute myeloid leukemia 75 years or older, or who have comorbidities that preclude use of intensive induction chemotherapy, in combination with azacitidine, decitabine, or low-dose cytarabine. In this study, Venclexta is referred as venetoclax due to the off-label investigational use in combination with ASTX727 in adults with newly diagnosed acute myeloid leukemia 75 years or older, or who have comorbidities that preclude use of intensive induction chemotherapy.

Background: Guadecitabine (G) is a next generation subcutaneous (SC) hypomethylating agent (HMA) resistant to degradation by cytidine deaminase which results in prolonged in vivo exposure to the active metabolite decitabine. We conducted a large global randomized phase 3 study (ASTRAL-2) of G vs TC in AML patients who were either refractory to or relapsed (r/r) after prior anthracycline-based intensive chemotherapy with or without hematopoietic cell transplant (HCT). Methods: r/r AML patients were randomized to G (60 mg/m 2 SC/d for 10 days in first 1-2 cycles followed by 5-day cycles Q 28 days) vs Treatment Choice (TC). TC were preselected prior to randomization to either low intensity (LI) treatment; high intensity (HI) chemotherapy; or Best Supportive Care (BSC). LI choices were other HMAs of azacitidine or decitabine, or low-dose Ara-C (LDAC) at their standard doses. HI choices were high-dose Ara-C (HiDAC), MEC, or FLAG± Ida combination chemotherapy at standard doses. Primary endpoint was overall survival (OS) based on ITT analysis with secondary endpoints including 12 and 24-month survival rates, complete response (CR), event-free survival (EFS), and safety. P values for secondary endpoints and subgroups are nominal as there was no adjustment of p values for multiple analyses. Results: 302 patients were randomized to G (148) or TC (154). Preselected TCs were mainly LI (77%) predominantly HMAs (86% of the patients randomized to LI), or HI (21%), with only 6 patients (2%) in the BSC subset. Baseline variables were well balanced across the 2 treatment arms. For G vs TC respectively, age ≥65 y in 51.4% vs 40.3% with median age 65y vs 63y, ECOG PS 2 in 15.5% vs 20.8%, poor risk cytogenetics in 44.6% vs 42.2%, refractory AML in 44.6% vs 33.1%, prior HCT in 18.2% vs 26%, a majority of patients were in second or subsequent relapse after ≥ 2 prior therapies (54.7% vs 56.5%). Median number of treatment cycles was short (3 cycles for G vs 2 cycles for TC). Median follow up was 21.6 months. Most common causes of treatment discontinuation were disease progression (35.2% for G vs 38.1% for TC), or death (15.2% for G vs 18.4% for TC). Median OS on G was 6.4 months vs 5.4 months for TC and not statistically significant (OS HR 0.88, 95% CI 0.67, 1.14, log rank p value 0.3). There was no significant difference in OS between G and each of the LI and HI preselected subsets. However, several other planned prospective subgroups favored G with OS HR 95% CI upper limit ≤ 1.0 including patients Adverse events (AEs) of grade ≥3, regardless of relationship to treatment, were 89% on G vs 84% on TC. Most common Grade ≥3 AEs for G vs TC respectively were febrile neutropenia (38.6% vs 38.1%); neutropenia (32.4% vs 17%); thrombocytopenia (28.3% vs 29.9%); anemia (21.4% vs 24.5%); pneumonia (18.6% vs 20.4%); and sepsis (11.7 vs 10.9%). None of the differences were significant except for neutropenia (p 0.003). Summary/Conclusions: In this randomized study in r/r AML after intensive chemotherapy, G did not significantly improve OS compared to standard of care TC composed mainly of LI treatment with other HMAs. The data suggest that G may be better than TC in in some of the secondary endpoints (24-month survival rate, EFS, CR, CR+CRh, and CRc). Prospective subgroup analyses of OS suggest that younger ( Disclosures Roboz: Actinium: Consultancy; Mesoblast: Consultancy; Janssen: Research Funding; AbbVie: Consultancy; Astex: Consultancy; AstraZeneca: Consultancy; Novartis: Consultancy; Agios: Consultancy; Glaxo SmithKline: Consultancy; Blueprint Medicines: Consultancy; Janssen: Consultancy; Jasper Therapeutics: Consultancy; Amgen: Consultancy; Astellas: Consultancy; Bristol Myers Squibb: Consultancy; Celgene: Consultancy; MEI Pharma - IDMC Chair: Consultancy; Helsinn: Consultancy; Bayer: Consultancy; Daiichi Sankyo: Consultancy; Jazz: Consultancy; Otsuka: Consultancy; Pfizer: Consultancy; Roche/Genentech: Consultancy. Sanz: Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Gilead Sciences: Other: Travel, accommodations, and expenses; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel, accommodations, and expenses; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Boehringer Ingelheim: Consultancy, Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel, accommodations, and expenses, Speakers Bureau; Helsinn Healthcare: Consultancy, Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, accommodations, and expenses, Research Funding. Griffiths: Novartis: Honoraria; Abbvie: Consultancy, Honoraria; Celgene/Bristol-Myers Squibb: Consultancy, Honoraria, Research Funding; Taiho Oncology: Consultancy, Honoraria; Apellis Pharmaceuticals: Research Funding; Astex Pharmaceuticals: Honoraria, Research Funding; Genentech: Research Funding; Boston Biomedical: Consultancy; Alexion Pharmaceuticals: Consultancy, Research Funding; Takeda Oncology: Consultancy, Honoraria. Yee: Forma Therapeutics: Research Funding; Astex: Membership on an entity's Board of Directors or advisory committees, Research Funding; F. Hoffmann La Roche: Membership on an entity's Board of Directors or advisory committees, Research Funding; TaiHo: Membership on an entity's Board of Directors or advisory committees; Genentech: Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees; Paladin: Membership on an entity's Board of Directors or advisory committees; Otsuka: Membership on an entity's Board of Directors or advisory committees; AbbVie: Honoraria; Bristol-Myers Squibb/Celgene: Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Onconova: Research Funding; Tolero: Research Funding; Jazz: Research Funding; MedImmune: Research Funding; Geron: Research Funding; Janssen: Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees; Shattuck Labs: Membership on an entity's Board of Directors or advisory committees. Kantarjian: Daiichi-Sankyo: Research Funding; BMS: Research Funding; Ipsen Pharmaceuticals: Honoraria; Astellas Health: Honoraria; Aptitude Health: Honoraria; KAHR Medical Ltd: Honoraria; Astra Zeneca: Honoraria; Pfizer: Honoraria, Research Funding; Ascentage: Research Funding; Amgen: Honoraria, Research Funding; Immunogen: Research Funding; Novartis: Honoraria, Research Funding; AbbVie: Honoraria, Research Funding; Precision Biosciences: Honoraria; Jazz: Research Funding; NOVA Research: Honoraria; Taiho Pharmaceutical Canada: Honoraria. Recher: Incyte: Honoraria; Janssen: Honoraria; Jazz: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Macrogenics: Honoraria, Membership on an entity's Board of Directors or advisory committees; MaatPharma: Research Funding; Astellas: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS/Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Daiichi Sankyo: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Agios: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Byrne: Karyopharm: Research Funding. Patkowska: Astellas Pharma, Inc.: Consultancy, Other: Travel fees; KCR US, Inc.: Consultancy; Bristol-Myers Squibb: Other: Travel fees; Jazz Pharmaceuticals: Other: Travel fees; Angelini Pharma: Honoraria, Other: Travel fees; Novartis: Honoraria, Other: Travel fees; Servier: Honoraria, Other: Travel fees; Pfizer: Other: Travel fees; AMGEN: Honoraria. Kim: AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; AIMS Biosciense: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; AML-Hub: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Astellas: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; BL & H: Research Funding; BMS & Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Boryung Pharm Co.: Consultancy; Daiichi Sankyo: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Handok: Consultancy, Honoraria; LG Chem: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Honoraria; Pintherapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees; Sanofi Genzyme: Honoraria, Speakers Bureau; SL VaxiGen: Consultancy, Honoraria; VigenCell: Consultancy, Honoraria. Stock: Pfizer: Consultancy, Honoraria, Research Funding; amgen: Honoraria; agios: Honoraria; jazz: Honoraria; kura: Honoraria; kite: Honoraria; morphosys: Honoraria; servier: Honoraria; syndax: Consultancy, Honoraria; Pluristeem: Consultancy, Honoraria. Illes: Janssen, Celgene, Novartis, Pfizer, Takeda, Roche: Consultancy; Takeda, Seattle Genetics: Research Funding; Novartis, Janssen, Pfizer, Roche: Other: Travel, Accommodations, Expenses. Fenaux: Abbvie: Honoraria, Research Funding; Takeda: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; JAZZ: Honoraria, Research Funding; Celgene/BMS: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Syros Pharmaceuticals: Honoraria. Miyazaki: Pfizer: Honoraria; Bristol-Myers Squibb: Honoraria; Abbvie: Honoraria; Novartis: Honoraria; Nippon-Shinyaku: Honoraria; Chugai: Honoraria; Janssen: Honoraria; Sumitomo-Dainippon: Honoraria, Research Funding; Astellas: Honoraria; Eisai: Honoraria; Daiichi-Sankyo: Honoraria; Takeda: Honoraria; Kyowa-Kirin: Honoraria; Sanofi: Honoraria. Yamauchi: Daiichi Sankyo: Research Funding; Astellas: Research Funding; Abbie: Research Funding; Chugai: Honoraria; Pfizer: Honoraria, Research Funding; Ono Pharmaceutical: Honoraria; Otsuka: Research Funding; Solasia Pharma: Research Funding. Hao: Astex Pharmaceuticals, Inc.: Current Employment. Keer: Astex Pharmaceuticals, Inc.: Current Employment. Azab: Astex Pharmaceuticals, Inc.: Membership on an entity's Board of Directors or advisory committees. Dohner: Celgene: Honoraria, Research Funding; Bristol Myers Squibb: Honoraria, Research Funding; Berlin-Chemie: Honoraria; Abbvie: Honoraria, Research Funding; AstraZeneca: Honoraria; Agios: Honoraria, Research Funding; Astex Pharmaceuticals: Honoraria; Amgen: Honoraria, Research Funding; Astellas: Honoraria, Research Funding; GEMoaB: Honoraria; Gilead: Honoraria; Helsinn: Honoraria; Janssen: Honoraria; Jazz Pharmaceuticals: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Oxford Biomedica: Honoraria; Pfizer: Research Funding; Roche: Honoraria.

Background: The RAS-RAF-MEK-ERK pathway is commonly upregulated in human cancers. This is an open-label Phase 1 study of ASTX029, a dual-mechanism extracellular signal-regulated kinase 1/2 (ERK1/2) inhibitor, in subjects with relapsed/refractory solid tumors (NCT03520075). Methods: The primary objectives are to identify a maximum tolerated dose and/or recommended Phase 2 dose. ASTX029 was administered orally daily of 21-day cycles as powder-in-bottle (PiB, Cohort 1/10mg) and tablet formulation (beginning with Cohort 6/80 mg) under fed conditions, and as tablet formulation under fasting conditions (beginning with Cohort 8/40 mg). Dose escalation occurred according to a “3+3 design” based on dose-limiting toxicity (DLT) events. Disease response was evaluated according to RECIST v1.1 and exploratory indicators, including tumor variant allele frequency changes detected by cell-free DNA (cfDNA) quantitation. Results: 56 subjects were treated with at least one dose of ASTX029 in Phase 1A (dose escalation). Of 46 subjects with data, 35 (76%) had any RAS mutations and 4 (9%) had BRAF mutations; 1 subject had both. At the 200 mg dose level (Cohort 5, PiB/fed), one of six evaluable subjects developed a DLT (grade 3 maculopapular rash). At the 280 mg dose level (Cohort 12, tablet/fasting), two subjects experienced grade 2 central serous retinopathy adverse events (CSR AEs) within a few days of dosing. These were the only CSR AEs noted and one event was declared a DLT. Both subjects recovered to baseline within days of dose interruption. One cohort level below this dose was expanded (Cohort 11/200 mg, tablet/fasting); this dose level was deemed safe (without a DLT or grade ≥2 visual AE in 7 subjects) and was selected for Phase 1B dose expansion. Mean pharmacokinetic (PK) exposure was 151% of target exposure, which is defined as the level expected to have biological activity based on animal studies. The most frequent grade ≥2 AEs assessed as drug-related included nausea (4 subjects, grade 2) and transaminitis (4 subjects: 3 grade 2, 1 grade 3). The grade 3 transaminitis occurred in a subject with metastatic sarcoma involving the liver. There was one serious AE of malaise considered related to study drug. Two subjects, one with KRAS-G12A and BRAF-D549N non-small cell lung cancer (120 mg) and one with KRAS-G12D metastatic pancreatic cancer (200 mg), achieved partial responses (cycle 15/ongoing and cycle 3/ongoing, respectively). In 2 subjects with stable disease as the best response, longitudinal cfDNA sequencing showed a decrease of tumor variant allele frequencies after 2 cycles of ASTX029, followed by a return to baseline levels before disease progression. The most common reason for ASTX029 discontinuation was disease progression. Conclusions: This Phase 1A study of the ERK1/2 inhibitor ASTX029 has identified a dose level of 200 mg daily of a 21-day cycle for investigation in the Phase 1B portion of the study. Pharmacokinetic and pharmacodynamic data suggest target exposures are achieved with preliminary clinical activity. Citation Format: Patricia LoRusso, Drew Rasco, Geoffrey Shapiro, Filip Janku, Alain Mita, Nilofer Azad, Marcia Toguchi, Chris Hindley, Shannon Bradley, Danna Chan, Harold Keer, Kim-Hien Dao, Ryan J. Sullivan, Alexander Spira. A first-in-human, Phase 1 study of ASTX029, a dual-mechanism inhibitor of ERK1/2, in relapsed/refractory solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT108.

Whilst mitogen-activated protein kinase (MAPK) pathway inhibitors are approved therapies in mutant-BRAF driven cancers and have demonstrated a high response rate in the clinic, the duration of response is often short-lived. Approaches targeting the immune system have elicited durable responses and led to the approval of checkpoint inhibitors such as the anti-PD1 therapy, pembrolizumab, in indications where MAPK pathway activation is often observed, such as melanoma. Activation of the MAPK pathway has been associated with an immunosuppressive tumor microenvironment (TME). Further, preclinical studies have demonstrated that in addition to inhibiting MAPK activity in tumor cells, MAPK pathway inhibitors such as the BRAFV600E inhibitor dabrafenib or MEK inhibitor trametinib have promoted a more proinflammatory TME leading to upregulated antigen presentation on tumor cells, increased CD8+ T cell infiltration and tumor cell killing. Similar preclinical results were recently reported for a KRASG12C inhibitor, AMG 510, where treatment of in vivo models led to an increase in tumor infiltrating lymphocytes, macrophages, dendritic cells and an increase in active immune gene signatures leading to tumor immunity. We have recently described the discovery of ASTX029, which is currently undergoing clinical development in advanced solid tumors (NCT03520075). ASTX029 is a dual-mechanism ERK1/2 (ERK) inhibitor, inhibiting both the catalytic activity and phosphorylation of ERK, and shows potent inhibition of MAPK-activated tumor growth in preclinical models. Previous studies have demonstrated a difference in regulation of genes involved in response to type I interferon following treatment with dual-mechanism compared to catalytic ERK inhibitors. We investigated whether treatment with ASTX029 modulates antigen presentation and the TME in MAPK-activated tumors. Following treatment of cell lines in vitro, we observed ASTX029-dependent changes consistent with increased antigen presentation, including an increase in cell surface expression of MHC class I and the increase in gene expression of tumor-specific antigens gp100 and MART-1 following treatment of melanoma cells. We have previously demonstrated that ASTX029 has good bioavailability following oral dosing in mice. To further investigate the effect of ASTX029 on the TME, syngeneic tumors grown in immunocompetent mice dosed with ASTX029 were characterized in terms of immune cell composition of the TME and gene expression. Our results were consistent with increased immune activation, including increased interferon signaling and a change in the immune cell composition of the TME. These data demonstrate that treatment with ASTX029 leads to modulation of the TME and we hypothesize that to optimize therapeutic activity, ASTX029 could be partnered either with an immunomodulatory or tumor-directed agent. Citation Format: Chris Hindley, Andrea Biondo, Kim-Hien Dao, Matthew Davis, Lynsey Fazal, Roberta Ferraldeschi, Keisha Hearn, Vanessa Martins, Harpreet Saini, Martin Sims, Nicola Wallis, Nicola Wilsher, Harold Keer, John Lyons, Joanne Munck. Immune modulation by the dual-mechanism ERK inhibitor, ASTX029, in MAPK-activated tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1661.

Background: Disease relapse remains to be the one of the major reasons of treatment failures after allogeneic stem cell transplantation (allo-SCT) in AML and MDS patients (pts). SGI-110 is a next generation hypomethylating agent that molecularly is a dinucleotide derivative of decitabine and therefore a more potent inhibitor of DNA methyltransferase activity. We present interim results of a single arm phase II trial evaluating the efficacy and safety of SGI-110 in AML/MDS pts. to improve transplant outcomes. Methods: In this study, there are 3 treatment cohorts defined by disease status after transplant with different primary outcomes of interest. Cohort 1 includes AML/MDS pts. with morphological relapse after transplant; cohort 2 pts with minimal residual (MRD) and cohort 3 pts with no evidence of disease. As of June 2020, 54 pts have enrolled. Herein, we report the interim analyses of 22 pts treated in cohort 3 and received SGI-110 as post-transplant maintenance while in remission. Other cohorts' results will be reported separately. The maintenance cohort includes high risk AML/MDS pts aged 18-75. High risk MDS is defined as having (1) poor or very poor cytogenetics by revised-IPSS or (2) monosomal karyotype or (3) bone marrow blast count > 5% before transplant; high risk AML as (1) adverse risk group by European LeukemiaNet (ELN) or (2) presence of MRD or active disease at transplant. Therapy-related AML/MDS is included. Pts. are excluded in the presence of (1) active acute graft versus host disease (GvHD), (2) uncontrolled systemic infection, or (3) concurrent use of systemic immune suppressive other than calcineurin inhibitors and sirolimus. The study intervention includes SGI-110 given as 30 mg/m2/day subcutaneously for 5 consecutive days every 28 days until completion of 12 cycles, disease relapse, or experience of unacceptable toxicity. SGI-110 is initiated between 42 to 100 days following allo-SCT if there is adequate engraftment with absolute neutrophil count >/= 1.0 x 109 /L; platelet >/= 50 x 109 /L and no documented evidence of relapse. Treatment delays up to 70 days and dose reductions are allowed per protocol. The primary endpoint for this cohort is relapse-free survival (RFS) time defined as either time to disease progression or death whichever happened first. The maximum planned sample size is 40. Results: As of June 2020, 22 pts were enrolled; M/F, 12/10, median age, 62 (range 18 to74). Of 11 AML pts., ELN risk category was adverse in 8, intermediate in 2 and favorable in 1. Of 11 MDS pts, 6 had poor/very poor and 4 good and 1 intermediate risk cytogenetic abnormalities by revised-IPSS. Of 22, 6 were in complete remission with count recovery at transplant. Median time to initiation of first cycle of maintenance with SGI-110 was 59.5 days (range, 43 to 114 days). So far, 14 pts of 22 were taken off the study; 6 due to disease relapse, 4 completed planned 12 cycles of treatment, 1 lost insurance, 1 withdrew the consent, 1 had travel issues due to COVID19 pandemic and 1 had pulmonary complications unrelated to study drug. Currently, 8 remain to be on the study. Median number of treatment cycles administered have been 4 (range, 1 to 12). Of 22, 7 pts. required the SGI-110 dose to be reduced down to 20 mg/m2/dayX5 days and 1 patient to 20 mg/m2/dayX3 days to be able to continue the treatment. At a median follow-up of 13.1 months for survivors (n=17), RFS and overall survival at 1-year was 66.3% (95% confidence interval (CI)=42% to 82.3%) and 88.9% (95%CI=61.8 to 92.2%) respectively (Figure) During the study, 353 AEs observed with 125 cycles of SGI-110 treatments. Of 353, 287 (81.3%) were attributable to SGI-110 and 133 of 287 (46.3%) were grade 3 or higher in severity. Most of the grade 3 or higher AEs were related with bone marrow suppression; 71 (25%) thrombocytopenia, 64 (22%) neutropenia, 67 (23%) leukopenia and 8 (2%) anemia. Of 22 pts, 15 had grade 4 neutropenia at least once and 8 pts grade 4 thrombocytopenia. There was 18 episodes of infectious AEs and 11 of 18 were grade 3-4. There were no grade 5 AEs observed attributable to study drug. Conclusion: SGI-110 led to frequent grade 3-4 BM suppression in high risk AML/MDS pts when given as maintenance therapy after allo-SCT. However, bone marrow suppression was not associated with increased risk of infection and it was temporary with count recovery. The efficacy of SGI-110 has been promising with 1-year RFS of 66.3%. The study currently is ongoing. Disclosures Oran: Celgene: Consultancy; Arog Pharmaceuticals: Research Funding; ASTEX: Research Funding. Alousi:Incyte: Honoraria, Research Funding; Therakos: Research Funding; Alexion: Honoraria. Mehta:CSL Behring: Research Funding; Incyte: Research Funding; Kadmon: Research Funding. Hosing:NKARTA Inc.: Consultancy. Popat:Bayer: Research Funding; Novartis: Research Funding. Keer:Astex Pharmaceuticals, Inc.: Current Employment. Champlin:Actinium: Consultancy; Genzyme: Speakers Bureau; Omeros: Consultancy; Cytonus: Consultancy; DKMS America: Membership on an entity's Board of Directors or advisory committees; Takeda: Patents & Royalties; Johnson and Johnson: Consultancy. OffLabel Disclosure: The abstract presents interim analyses of a clinical trial investigating efficacy and safety of SGI-110 used as maintenance therapy in high risk AML and MDS patients after transplant.

Introduction: Hypomethylating agents (HMAs) or DNA methyltransferase inhibitors (DNMTi) such as decitabine or azacitidine are established standard of care for the treatment of MDS and CMML. The oral bioavailability of these agents has been limited due to rapid degradation by cytidine deaminase (CDA) in the gut and liver, hence requiring intravenous infusion or subcutaneous injections daily for 5-7 days every month (m). This parenteral administration requirement adds significant burden to older cancer patients due to daily time commitment and travel to treatment centers. It also increases exposure to and infection risk with SARS-CoV-2 during the COVID-19 pandemic. Oral decitabine 35 mg/cedazuridine 100 mg (ASTX727) is an oral fixed dose combination drug of decitabine and the CDA inhibitor cedazuridine that have shown 99% (90% CI 93% to 106%) equivalent exposure to standard dose IV decitabine 20 mg/m2 in a randomized cross-over study (Garcia-Manero et al, ASH 2019). Here, we present the clinical efficacy and safety results of oral decitabine/cedazuridine from 133 patient study in MDS and CMML (ASTX727-02 ASCERTAIN study). Methods: We used a randomized cross over design where patients were randomized in the first 2 cycles 1:1 to either Sequence A: decitabine 35 mg/ cedazuridine 100 mg in Cycle 1 followed by IV decitabine at 20 mg/m2 in Cycle 2, or Sequence B: IV decitabine in Cycle 1 followed by oral decitabine/cedazuridine in Cycle 2 to do an intra-patient comparison of decitabine PK (primary PK endpoint: decitabine AUC equivalence over 5 days of dosing). Cycles were repeated every 28 days. All patients received oral decitabine/cedazuridine in all subsequent cycles from Cycle 3 onwards until disease progression or unacceptable toxicity. Patients were eligible as per the FDA-approved label of IV decitabine (MDS patients by FAB classification including CMML, or MDS IPSS Intermediate-1, 2 or high-risk patients). Clinical endpoints were best response as assessed by an independent expert panel according to International Working Group (IWG) 2006 response criteria, transfusion independence for at least 8 or 16 consecutive weeks, overall survival, and safety. Adverse events (AEs) were graded by Common Terminology Criteria for Adverse Events (CTCAE) v 4.03. Results: 138 subjects were randomized, of whom 133 were treated on study. The median age was 71.0 years (range 44-88), 65% were male, 88% MDS and 12% CMML, 43% were either red blood cells (RBCs) or platelets transfusion-dependent at baseline, 25% had poor-risk cytogenetics, and 42% had baseline bone marrow blasts >5%. At the data cutoff for the response analysis, the median duration of follow up was 12.6 m (range 9.3 to 20.5 m) with median number of treatment cycles of 8 (range 1 to 18). Of the 133 treated patients the best response was complete response (CR) in 28 patients (21%; 95% CI 15-29%), marrow (m)CR with hematological improvement (HI) in 20 patients (15%), mCR without HI in 23 patients (17.3%), and HI in 10 patients (7.5%) for an overall objective response (CR+mCR+HI) in 81 patients (61%; 95% CI 52-69%). Median duration of CR was 7.5 m (range 1.6 to 17.5 m), and median time to CR was 4.3 m (range 2.1 to 15.2 m). Of the 133 treated patients 27 (20%) went on to receive allogeneic hematopoietic cell transplant. Of the 57 patients who were either RBCs or platelets transfusion-dependent at baseline, 30 (53%) became transfusion independent for both RBCs and platelets for at least 8 consecutive weeks, and 19 (33%) were both RBCs and platelets transfusion independent for at least 16 consecutive weeks. Median survival has not been reached. Most common Treatment-Emergent AEs of Grade ≥3 regardless of causality were neutropenia in 51.5%, thrombocytopenia in 50%, anemia in 40%, febrile neutropenia in 26%, leukopenia in 21%, pneumonia in 12%, and sepsis in 7% of patients treated with oral decitabine/cedazuridine (excluding the IV decitabine cycle). Summary/Conclusions: Efficacy and safety from oral decitabine 35 mg/ cedazuridine 100 mg daily for 5 days every 28 days are consistent with clinical data from standard IV decitabine 20 mg/m2 daily for 5 days. Oral decitabine/cedazuridine is the only oral HMA with systemic exposure equivalent to its injectable drug. Further investigation of oral decitabine/cedazuridine in all-oral combination studies is warranted and underway. Disclosures Savona: BMS: Consultancy; AbbVie: Consultancy; Gilead: Consultancy; Karyopharm: Consultancy, Current equity holder in publicly-traded company; Ryvu: Consultancy; Boehringer Ingelheim: Patents & Royalties; Takeda: Consultancy, Research Funding; Incyte: Consultancy, Research Funding; Astex: Consultancy, Research Funding; Sunesis: Consultancy, Research Funding; TG Therapeutics: Consultancy, Research Funding. Griffiths:Celgene/BMS: Honoraria, Research Funding; Genentech Inc: Research Funding; Boston Biomedical: Honoraria; AbbVie Inc: Honoraria; Persimmune: Research Funding; Novartis: Honoraria, Research Funding; Alexion Pharmaceuticals: Honoraria, Research Funding; Astex Pharmceuticals: Research Funding. Zeidan:CCITLA: Other; Seattle Genetics: Consultancy, Honoraria; BeyondSpring: Consultancy, Honoraria; Taiho: Consultancy, Honoraria; Cardinal Health: Consultancy, Honoraria; Epizyme: Consultancy, Honoraria; Leukemia and Lymphoma Society: Other; Jazz: Consultancy, Honoraria; Trovagene: Consultancy, Honoraria, Research Funding; Ionis: Consultancy, Honoraria; Takeda: Consultancy, Honoraria, Research Funding; Astex: Research Funding; Daiichi Sankyo: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria, Research Funding; Otsuka: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria, Research Funding; Acceleron: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Research Funding; Boehringer-Ingelheim: Consultancy, Honoraria, Research Funding; Celgene / BMS: Consultancy, Honoraria, Research Funding; Agios: Consultancy, Honoraria; ADC Therapeutics: Research Funding; Aprea: Research Funding; MedImmune/Astrazeneca: Research Funding; Cardiff Oncology: Consultancy, Honoraria, Other; Incyte: Consultancy, Honoraria, Research Funding; Astellas: Consultancy, Honoraria. Patel:DAVA Pharmaceuticals: Honoraria; France Foundation: Honoraria; Celgene: Consultancy, Speakers Bureau; Agios: Consultancy. Keating:Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Hoffman La Roche: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Merck: Membership on an entity's Board of Directors or advisory committees; Sanofi: Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Consultancy; Servier: Membership on an entity's Board of Directors or advisory committees; Shire: Membership on an entity's Board of Directors or advisory committees; Taiho: Membership on an entity's Board of Directors or advisory committees. Dao:Astex Pharmaceuticals, Inc.: Current Employment. Fazal:Jansen: Speakers Bureau; Gilead/Kite: Consultancy, Speakers Bureau; Takeda: Consultancy, Speakers Bureau; Jazz Pharma: Consultancy, Speakers Bureau; Karyopham: Speakers Bureau; Celgene: Speakers Bureau; Glaxosmith Kline: Consultancy, Speakers Bureau; Incyte Corporation: Consultancy, Honoraria, Speakers Bureau; Agios: Consultancy, Speakers Bureau; Stemline: Consultancy, Speakers Bureau; Amgen: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Odenike:Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Astex Pharmaceuticals, NS Pharma, Gilead Sciences, Janssen Oncology, Oncotherapy, Agios, CTI/Baxalta, Aprea: Other: Institutional research funding; Astra Zeneca: Research Funding; Incyte: Other: Institutional research funding; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Impact Biomedicines: Consultancy, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Kantarjian:Abbvie: Honoraria, Research Funding; BioAscend: Honoraria; Delta Fly: Honoraria; Ascentage: Research Funding; Janssen: Honoraria; Novartis: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Sanofi: Research Funding; Actinium: Honoraria, Membership on an entity's Board of Directors or advisory committees; Immunogen: Research Funding; Aptitute Health: Honoraria; BMS: Research Funding; Daiichi-Sankyo: Honoraria, Research Funding; Jazz: Research Funding; Oxford Biomedical: Honoraria; Amgen: Honoraria, Research Funding; Adaptive biotechnologies: Honoraria. DeZern:MEI: Consultancy; Celgene: Consultancy, Honoraria; Astex: Research Funding; Abbvie: Consultancy. Roboz:Novartis: Consultancy; Janssen: Consultancy; Celgene: Consultancy; Astex: Consultancy; Amphivena: Consultancy; Agios: Consultancy; Pfizer: Consultancy; Abbvie: Consultancy; Array BioPharma: Consultancy; Bayer: Consultancy; Celltrion: Consultancy; Eisai: Consultancy; Jazz: Consultancy; Roche/Genentech: Consultancy; Sandoz: Consultancy; Actinium: Consultancy; Argenx: Consultancy; Astellas: Consultancy; Daiichi Sankyo: Consultancy; AstraZeneca: Consultancy; Orsenix: Consultancy; Otsuka: Consultancy; Takeda: Consultancy; Trovagene: Consultancy; Cellectis: Research Funding; Jasper Therapeutics: Consultancy; Epizyme: Consultancy; Helsinn: Consultancy; MEI Pharma: Consultancy. Busque:Pfizer: Honoraria; BMS: Honoraria; Novartis: Honoraria. Wells:Alexion: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Leber:Pfizer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Otsuka Pharmaceutical: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda/Palladin: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Treadwell: Honoraria, Membership on an entity's Board of Directors or advisory committees; Lundbeck: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Alexion: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BMS/Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees. Hao:Astex Pharmaceuticals, Inc.: Current Employment. Keer:Astex Pharmaceuticals, Inc.: Current Employment. Azab:Astex Pharmaceuticals, Inc.: Current Employment. Garcia-Manero:Acceleron Pharmaceuticals: Consultancy, Honoraria; AbbVie: Honoraria, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; H3 Biomedicine: Research Funding; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astex Pharmaceuticals: Consultancy, Honoraria, Research Funding; Amphivena Therapeutics: Research Funding; Helsinn Therapeutics: Consultancy, Honoraria, Research Funding; Onconova: Research Funding; Merck: Research Funding; Jazz Pharmaceuticals: Consultancy; Celgene: Consultancy, Honoraria, Research Funding; Novartis: Research Funding.

Background: Disease relapse remains to be the one of the major reasons of treatment failures after allogeneic stem cell transplantation (allow-SCT) in AML and MDS patients (pts.). Guadecitabineis (SGI-110) a next generation hypomethylating agent that molecularly is a dinucleotide derivative of decitabine and achieves a more effective hypomethylation activity due to extended exposure window of the active metabolite decitabine. We present interim results of a single arm phase II trial evaluating the efficacy and safety of SGI-110 in AML/MDS pts. to improve transplant outcomes. Methods: In this study, there are 3 treatment cohorts defined by disease status after transplant with different outcomes. Cohort 1 includes AML/MDS pts. with morphological relapse; cohort 2 with minimal residual (MRD) and cohort 3 with no evidence of disease. As of June 2020, 54 pts. have enrolled. Herein, we report the interim analyses cohort 2 pts. aged 18-75 with detectable MRD by flow cytometry or cytogenetic or molecular testing after allo-SCT. Pts. are excluded in the presence of (1) any anti-leukemic agents used after MRD detection (2) active acute or chronic graft versus host disease (GvHD), (3) uncontrolled systemic infection (4) Concurrent use of systemic immune suppressive other than calcineurin inhibitors and sirolimus. The study intervention includes SGI-110 given as 40 mg/m2/day subcutaneously for 5 consecutive days every 28 days in addition to 3 planned donor lymphocyte infusions (DLI) if clinically feasible. The pts. are allowed to receive maximum 6 cycles of SGI-110 to achieve response which was defined as eradication of MRD. Pts. achieving response continue the treatment with SGI-110 given as maintenance to complete 12 cycles of treatment. DLI is planned to be given on the 6th day of the 2nd, 4th and 6th cycles of SGI-110 if clinically feasible. Pts. are taken off the study if there is (1) relapse or no response within the first 6 cycles of SGI-110 (2) related and unexpected serious adverse events (AEs) (3) withdrawal of consent or death or lost to follow up. Study is designed to take a response probability of .20 or larger as considered promising. A maximum of 25 pts. with MRD will be treated. Results: As of June 2020, 17 pts. enrolled; M/F was 6/11, median age 63 (range 28 to70) and 11 had AML. Of 17 pts., 6 had their second allo-SCT. European LeukemiaNet risk category was adverse in 8, intermediate in 2 and favorable in 1 AML pts. Of 6 MDS pts., 6 had poor or very poor risk cytogenetics by revised-IPSS. Median time to MRD detection after the last transplant was 94 days (range, 28 to 504 days). Chimerism was checked in 16 pts. at the time of MRD detection; median T and myeloid cell chimerism was 100% (range, 35% to 100% for T and 24% to 100% for myeloid cell lineages). Pts. started SGI-110 within a median of 17 days after MRD detection (range, 1 to 58 days). Of 17 pts., 14 were evaluable for response; 2 have been undergoing the treatment with no response evaluation yet done and one died of respiratory complications not related to study drug before response evaluation was possible. Of 14, 6 achieved response with MRD eradication (posterior probability of response=41.3% with 95% credible interval (CI) 18.0% to 65.3%). The number of SGI-110 treatment cycles before response varied from 1 to 6 with a median of 3. All but 1 responders received at least one DLI infusion before achieving MRD eradication. Of the 6 responders, only 1 had disease relapse and another died due to GvHD related complications, both 20 months after MRD detection. For pts. who had response with MRD eradication, relapse-free survival (RFS) at 1-year after response determination was 100% (95%CI=21%-69.6%) and it was 0% for non-responders (Figure 1a). Similarly, OS was 100% for responders and 0% for non-responders at 1-year after response determination (Figure 1b). During the study, 130 AEs observed during the 53 cycles of SGI-110 treatment applied. Of 130, 108 (83%) were attributable to SGI-110 and 70 of 108 (65%) were grade 3 or higher in severity. Most of the AEs were related with bone marrow suppression; of 70 AEs grade 3 or higher, 23 (33%) were thrombocytopenia, 15 (21%) were neutropenia, and 2 were anemia. There was no grade 5 AE observed attributable to study drug. Conclusion: SGI-110 given with or without DLI is well tolerated and yields encouraging response rates that are durable to prevent morphological relapse after MRD detection in the post-transplant setting. The study has been ongoing. Figure 1 Disclosures Oran: ASTEX: Research Funding; Arog Pharmaceuticals: Research Funding; Celgene: Consultancy. Alousi:Incyte: Honoraria, Research Funding; Alexion: Honoraria; Therakos: Research Funding. Mehta:Kadmon: Research Funding; Incyte: Research Funding; CSL Behring: Research Funding. Kebriaei:Amgen: Other: Research Support; Jazz: Consultancy; Kite: Other: Served on advisory board; Novartis: Other: Served on advisory board; Pfizer: Other: Served on advisory board; Ziopharm: Other: Research Support. Popat:Bayer: Research Funding; Novartis: Research Funding. Keer:Astex Pharmaceuticals, Inc.: Current Employment. Champlin:Johnson and Johnson: Consultancy; Genzyme: Speakers Bureau; Actinium: Consultancy; DKMS America: Membership on an entity's Board of Directors or advisory committees; Cytonus: Consultancy; Omeros: Consultancy; Takeda: Patents & Royalties. OffLabel Disclosure: Guadecitabine was used off-label for relapse prevention in the post-transplant setting.

Oncogenic mutations in genes such as the RAS family (KRAS, NRAS or HRAS) or receptor tyrosine kinases (RTKs) drive tumor growth through aberrant activation of the mitogen activated protein kinase (MAPK) signaling pathway. Acute myeloid leukemia (AML) patients frequently exhibit activating mutations in MAPK pathway members, such as NRAS and KRAS, suggesting that these malignancies may be driven by aberrant activation of the MAPK pathway. Targeting of the MAPK pathway has been clinically validated in solid tumors, with agents targeting BRAF and MEK approved for the treatment of BRAF-mutant melanoma. However, there is currently no approved therapy directly targeting activated RAS family members and resistance to MAPK pathway inhibitors is frequently associated with reactivation of MAPK signaling. ERK1/2 (ERK) is a downstream node in the MAPK pathway and therefore represents an attractive therapeutic target for inhibition of MAPK signaling in these settings. We have recently described in vivo anti-tumor activity in MAPK-activated solid tumor models following treatment with ASTX029, a highly potent ERK inhibitor developed using fragment-based drug design. ASTX029 has a distinctive ERK binding mode which confers dual mechanism inhibition of ERK, inhibiting both the catalytic activity of ERK and its phosphorylation by MEK. Here, we demonstrate that ASTX029 is also active in AML models and potently inhibits in vitro and in vivo MAPK signaling and growth in these models. Using a panel of 15 AML cell lines, we investigated sensitivity to ASTX029 in vitro. We observed that 8 cell lines bearing mutations leading to increased MAPK pathway signaling were sensitive to treatment with ASTX029 with an average IC50 value of 47 nM, in contrast to an average IC50 value of 1800 nM for cell lines without activating mutations. The phosphorylation of RSK, a direct substrate of ERK, was suppressed for up to 24 h following treatment with ASTX029 in vitro. We have previously demonstrated good oral bioavailability for ASTX029 and once daily dosing resulted in significant tumor growth inhibition in AML cell line xenograft models. To confirm target engagement in vivo, we examined MAPK signaling in xenograft tissue and observed inhibition of the phosphorylation of RSK and of ERK itself, consistent with the dual mechanism of action proposed for ASTX029. In summary, the ERK inhibitor, ASTX029, has potent activity against MAPK-activated tumor models, including AML models, and is now being tested in a Phase 1/2 clinical trial in advanced solid tumors (NCT03520075). These data highlight its therapeutic potential for the treatment of AML in patients with mutations leading to MAPK pathway activation and support further investigation in these patient populations. Disclosures Hindley: Astex Pharmaceuticals: Current Employment. Fazal:Astex Pharmaceuticals: Current Employment. Munck:Astex Pharmaceuticals: Current Employment. Martins:Astex Pharmaceuticals: Current Employment. Shah:Astex Pharmaceuticals: Current Employment. Wilsher:Astex Pharmaceuticals: Current Employment. Wallis:Astex Pharmaceuticals: Current Employment. Keer:Astex Pharmaceuticals, Inc.: Current Employment. Lyons:Astex Pharmaceuticals: Current Employment.

Purpose: This first-in-human, phase I study evaluated ASTX660, an oral, small-molecule antagonist of cellular/X-linked inhibitors of apoptosis proteins in patients with advanced solid tumors or lymphoma. Patients and Methods: ASTX660 was administered orally once daily on a 7-day-on/7-day-off schedule in a 28-day cycle. Dose escalation followed a standard 3+3 design to determine the MTD and recommended phase II dose (RP2D). Dose expansion was conducted at the RP2D. Results: Forty-five patients received ASTX660 (range 15–270 mg/day). Dose-limiting toxicity of grade 3 increased lipase with or without increased amylase occurred in 3 patients at 270 mg/day and 1 patient at 210 mg/day. The MTD was determined to be 210 mg/day and the RP2D 180 mg/day. Common treatment-related adverse events included fatigue (33%), vomiting (31%), and nausea (27%). Grade ≥3 treatment-related adverse events occurred in 7 patients, most commonly anemia (13%), increased lipase (11%), and lymphopenia (9%). ASTX660 was rapidly absorbed, with maximum concentration achieved at approximately 0.5–1.0 hour. An approximately 2-fold accumulation in AUC exposures was observed on day 7 versus 1. ASTX660 suppressed cellular inhibitor of apoptosis protein-1 in peripheral blood mononuclear cells, which was maintained into the second cycle beyond the off-therapy week at the 180-mg/day RP2D and above. Clinical activity was seen in a patient with cutaneous T-cell lymphoma. Conclusions: ASTX660 demonstrated a manageable safety profile and exhibited evidence of pharmacodynamic and preliminary clinical activity at the 180-mg/day RP2D. The phase II part of the study is ongoing.

Background Gastrointestinal stromal tumours (GIST) treated with the tyrosine kinase inhibitor (TKI) imatinib can become resistant when additional mutations in the receptor tyrosine kinases KIT or PDGFRA block imatinib activity. Mutated KIT requires the molecular chaperone heat-shock protein 90 (HSP90) to maintain stability and activity. Onalespib (AT13387) is a potent non-ansamycin HSP90 inhibitor. We hypothesised that the combination of onalespib and imatinib may be safe and effective in managing TKI-resistant GIST. Patients and methods In this dose-escalation study, we evaluated the safety and efficacy of combination once-weekly intravenous onalespib for 3 weeks and daily oral imatinib in 28-d cycles. Twenty-six patients with TKI-resistant GIST were enrolled into four sequential dose cohorts of onalespib (dose range, 150–220 mg/m 2 ) and imatinib 400 mg. The relationship between tumour mutational status ( KIT/PDGFRA ) and efficacy of treatment was explored. Results Common onalespib-related adverse events were diarrhoea (58%), nausea (50%), injection site events (46%), vomiting (39%), fatigue (27%), and muscle spasms (23%). Overall, 81% of patients reported more than one onalespib-related gastrointestinal disorder. Nine patients (35%) had a best response of stable disease, including two patients who had KIT mutations known to be associated with resistance to imatinib and sunitinib. Disease control at 4 months was achieved in five patients (19%), and median progression-free survival was 112 d (95% confidence interval 43–165). One patient with PDGFRA -mutant GIST had a partial response for more than 376 d. Conclusion The combination of onalespib plus imatinib was well tolerated but exhibited limited antitumour activity as dosed in this TKI-resistant GIST patient population. Trial registration ID: clinicaltrials.gov : NCT01294202

Background Fibroblast growth factors (FGFs) play important roles in multiple cancers by supporting tumor growth and angiogenesis. FP-1039 (GSK3052230) is a FGF ligand trap consisting of the extracellular domain of FGF receptor 1 (FGFR1) fused with the Fc region of IgG1. FP-1039 binds and neutralizes multiple FGFs that normally bind FGFR1. The primary objective of this phase I study was to evaluate the safety and tolerability of FP-1039. Patients and methods Eligible patients with metastatic or locally advanced solid tumors for which standard treatments were ineffective were treated with weekly doses of FP-1039 for 4 weeks, followed by 2 weeks observation. Results Thirty-nine subjects received a mean of 6 infusions of FP-1039 at doses ranging from 0.5 to 16 mg/kg weekly, with no maximally tolerated dose identified. Grade 3 or greater treatment emergent adverse events were uncommon. Four dose-limiting toxicities were reported at doses of 0.75 mg/kg (urticaria), 1 mg/kg (intestinal perforation and neutropenia), and 16 mg/kg (muscular weakness). Drug exposure was dose proportional, and the terminal elimination half-life was 2.6–3.9 days following a single dose. Target engagement as measured by low free plasma FGF2 levels was achieved. FGF pathway dysregulation was uncommon. No objective responses were observed. Conclusion In nonselected cancer patients with advanced disease, treatment with FP-1039 was well tolerated and toxicities associated with small molecule drugs that inhibit FGFR tyrosine kinases, including hyperphosphatemia, were not observed. Further studies of FP-1039 in patients selected for FGF pathway dysregulation, who are most likely to benefit, are now underway.

Background: Therapeutic targeting of the PD-1/PDL-1 axis significantly increases the survival of melanoma (MM) and non-small cell lung cancer (NSCLC) patients. Despite this unprecedented efficacy, a sizeable proportion of MM and NSCLC patients fails to benefit from therapy due to primary or secondary resistance to treatment. In this scenario, deepening the knowledge on mechanism(s) underlying treatment failure allows to design novel, mechanism-based, therapeutic approaches to overcome resistance to anti-PD-1/PDL-1 therapy. Along this line, we have extensively characterized the immunomodulatory properties of DNA hypomethylating agents (DHA) in different human malignances. Exposure of neoplastic cells to DHA efficiently improved antigen-restricted and -unrestricted T cell recognition of cancer cells in vitro through the upregulation/induction of the expression of epigenetically regulated tumor associated antigens, HLA class I and/or accessory/co-stimulatory molecules by neoplastic cells. Supporting these ex vivo data, combining the systemic administration of DHA (ie, decitabine or guadecitabine) with antibodies to different immune checkpoints significantly reduced tumor growth of murine syngeneic grafts, compared to single-agent therapy. Supporting these pre-clinical findings, our phase Ib NIBIT-M4 study has been the first clinical trial demonstrating that systemic administration of guadecitabine followed by CTLA-4 blockade with ipilimumab is safe and tolerable in MM patients, shows a promising anti-tumor, and induces a significant modulation of immune related pathways in tumor samples (Di Giacomo AM, Clin Cancer Res 2019). Prompted by these results and to further explore the efficacy of DHA combined with immune-checkpoints blockade we have designed and activated the NIBIT-ML1 trial. This study aims at investigating the efficacy of guadecitabine combined with ipilimumab and nivolumab in reverting the resistance to PD-1/PDL-1 therapy of MM and NSCLC patients. Methods: The NIBIT-ML1 is a randomized, phase II study designed according to the two stages optimal design by Simon, in unresectable Stage III or Stage IV MM (Cohort A) or NSCLC (Cohort B) patients who failed therapy with anti-PD-1/PDL-1 as last treatment. Primary objective of the study is immune (i)-ORR according to iRECIST criteria. Secondary objectives include safety, DCR, PFS, median OS, and survival rate at 1 and 2-years. Extensive cellular and molecular immune correlates will also be explored. Following a safety run-in phase in 6 subjects per Cohort, eligible patients will be randomized to receive: guadecitabine plus ipilimumab and nivolumab (ARM A) or ipilimumab and nivolumab (ARM B). Sample size will range from 6 to 92 patients per Cohort. The first patient first visit is foreseen by March 2020 (NCT04250246) Citation Format: Anna Maria Di Giacomo, Luana Calabrò, Riccardo Danielli, Monica Valente, Elisabetta Gambale, Sandra Coral, Giovanni Amato, Harold Keer, Diana Giannarelli, Mohammad Azab, Andrea Anichini, Alessia Covre, Michele Maio. A randomized, multi-center, phase II study of nivolumab combined with ipilimumab and guadecitabine or nivolumab combined with ipilimumab in melanoma and NSCLC patients resistant to anti-PD-1/-PD-L1: The NIBIT-ML1 Study [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT270.

3609 Background: Combination BRAF and MEK inhibitor therapy is associated with response in patients (pts) with BRAF mutant (mut) solid tumors; however critical limitations for the durable activity of these agents remains. Preclinically, the addition of heat shock protein 90 (HSP90) inhibitors improves the efficacy of BRAF inhibitor (BRAFi) therapy in both BRAFi -sensitive and resistant mutant cell lines. Methods: CTEP study 9557 (NCT02097225) is a phase I study designed to determine the safety and efficacy of the small molecule HSP90inhibitor, AT13387, in combination with dabrafenib (dab) and trametinib (tram) in patients with BRAF V600E/K mut solid tumors. Prior chemotherapy, immunotherapy, BRAF and/or MEK exposure was permitted. The primary objective was to determine the maximum tolerated dose (MTD). Results: From July 2015 to June 2018, 22 patients with previously treated, metastatic BRAF V600E/K mut solid tumors were enrolled using a 3 + 3 design at four dose levels (DL) (Table). Pts were predominantly female (59%) with a median age of 57.5yrs (37 -75). The most common tumor type was BRAF V600Emut colon cancer (N=12). Dose limiting toxicities (DLTs) occurred in one patient in DL3 and one in DL4, specifically grade 3 myelosuppression and fatigue, respectively. The MTD was Dab 150mg [BID/PO], Tram 2mg [QD/PO] and AT1187 260mg/m2 [D1,8,15/IV]. Twenty-one of 22 pts were eligible for efficacy assessment. Best response, per RECIST 1.1, was partial response (PR) in 2 pts – one with colon ca (TKI-naïve), one with melanoma (TKI-resistant) - stable disease (SD) in 8 pts, and disease progression (PD) in 11 with a disease control rate (PR + SD) of 47.6% (90% CI: 29% - 67%). Median time to progression was significantly longer in DL3 (3.9 mths; 1.8-9.2) compared to DL1 (1.6mths; 0.9-1.7) or DL2 (1.5; 0.6-3.6). Median PFS and OS were 1.8mths (90% CI: 1.6 – 3.7mths) and 5.1 mths (90% CI: 2.5 -10.6mths), respectively. Median OS was not reached in DL3/4. Correlative data on the expression of the key signaling proteins relating to response will be presented at the meeting. Conclusions: HSP90 inhibition combined with BRAF/MEK inhibition was determined to be safe with evidence of disease control in a heavily pre-treated population of pts with BRAF V600E/K mut solid tumors. Clinical trial information: NCT02097225 . [Table: see text]

Purpose: Onalespib is a potent, fragment-derived second-generation HSP90 inhibitor with preclinical activity in castration-resistant prostate cancer (CPRC) models. This phase I/II trial evaluated onalespib in combination with abiraterone acetate (AA) and either prednisone or prednisolone (P) in men with CRPC progressing on AA/P. Patients and Methods: Patients with progressing CRPC were randomly assigned to receive 1 of 2 regimens of onalespib combined with AA/P. Onalespib was administered as intravenous infusion starting at 220 mg/m2 once weekly for 3 of 4 weeks (regimen 1); or at 120 mg/m2 on day 1 and day 2 weekly for 3 of 4 weeks (regimen 2). Primary endpoints were response rate and safety. Secondary endpoints included evaluation of androgen receptor (AR) depletion in circulating tumor cells (CTC) and in fresh tumor tissue biopsies. Results: Forty-eight patients were treated with onalespib in combination with AA/P. The most common ≥grade 3 toxicities related to onalespib included diarrhea (21%) and fatigue (13%). Diarrhea was dose limiting at 260 and 160 mg/m2 for regimens 1 and 2, respectively. Transient decreases in CTC counts and AR expression in CTC were observed in both regimens. HSP72 was significantly upregulated following onalespib treatment, but only a modest decrease in AR and GR was shown in paired pre- and posttreatment tumor biopsy samples. No patients showed an objective or PSA response. Conclusions: Onalespib in combination with AA/P showed mild evidence of some biological effect; however, this effect did not translate into clinical activity, hence further exploration of this combination was not justified.

Purpose: Epigenetic changes are implicated in acquired resistance to platinum. Guadecitabine is a next-generation hypomethylating agent (HMA). Here, we report the clinical results, along with pharmacokinetic (PK) and pharmacodynamic analyses of the phase I study of guadecitabine and carboplatin in patients with recurrent, platinum-resistant high-grade serous ovarian cancer, primary peritoneal carcinoma (PPC), or fallopian tube cancer (FTC). Experimental Design: Guadecitabine was administered once daily on days 1 to 5 followed by carboplatin i.v. on day 8 of a 28-day cycle. Patients had either measurable or detectable disease. Safety assessments used CTCAE v4. Results: Twenty patients were enrolled and treated. Median age was 56 years (38–72 years). The median number of prior regimens was 7 (1–14). In the first cohort (N = 6), the starting doses were guadecitabine 45 mg/m2 and carboplatin AUC5. Four patients experienced dose-limiting toxicity (DLT; neutropenia and thrombocytopenia), leading to dose deescalation of guadecitabine to 30 mg/m2 and of carboplatin to AUC4. No DLTs were observed in the subsequent 14 patients. Grade ≥3 adverse events ≥10% were neutropenia, leukopenia, anemia, nausea, vomiting, ascites, constipation, hypokalemia, pulmonary embolism, small-intestinal obstruction, and thrombocytopenia. Three patients had a partial response (PR), and 6 patients had stable disease (SD) >3 months, for an overall response rate (ORR) and clinical benefit rate of 15% and 45%, respectively. LINE-1 demethylation in PBMCs and promoter demethylation/gene reexpression in paired tumor biopsies/ascites were recorded. Conclusions: Guadecitabine and carboplatin were tolerated and induced clinical responses in a heavily pretreated platinum-resistant ovarian cancer population, supporting a subsequent randomized phase II trial. Clin Cancer Res; 24(10); 2285–93. ©2018 AACR.

Leiomyosarcomas are rare mesenchymal neoplasms characterized by a smooth muscle differentiation pattern. Due to the extremely poor prognosis in patients, the development of novel chemotherapeutic regimens remains critically important. In this study, multiple leiomyosarcoma cell lines, SK-UT1, SK-LMS1, and MES-SA were treated with varying doses of the DNA Methyltransferase Inhibitors (DNMTi) 5-azacitidine (Aza), 5-aza-2-deoxycytidine (DAC), and guadecitabine (SGI-110). The effect of these epigenetic modulators was measured using both in-vitro and in-vivo models. Of the three epigenetic modulators, Guadecitabine was the most effective at decreasing cell survival in LMS cell lines. SK-UT1 was found to be the more sensitive to all three epigenetic modulators, while SK-LMS1 and MES-SA were more resistant. The contrast in sensitivity seen was also represented by the increase in apoptosis in Aza and guadecitabine. In parallel with Aza, guadecitabine was observed to also arrest the cell cycle. Treatment with guadecitabine led to a decrease in growth across the spectrum of sensitivity in LMS cell lines, both in a delayed in vitro and in vivo model; in parallel experiments, apoptotic pathways were activated in sensitive and less sensitive lines. Additional studies are required to explore potential therapeutic applications and mechanisms for leiomyosarcoma treatment.

DNA methylation aberrations have been implicated in acquired resistance to platinum drugs in ovarian cancer. In this study, we elucidated an epigenetic signature associated with platinum drug resensitization that may offer utility in predicting the outcomes of patients who are coadministered a DNA methyltransferase inhibitor. The ovarian cancer specimens we analyzed were derived from a recent clinical trial that compared the responses of patients with recurrent platinum-resistant ovarian cancer who received carboplatin plus the DNA methyltransferase inhibitor guadecitabine or a standard-of-care chemotherapy regimen selected by the treating physician. Tumor biopsies or malignant ascites were collected from patients before treatment (day 1, cycle 1) or after treatment (after 2 cycles) for epigenomic and transcriptomic profiling using the Infinium HumanMethylation450 BeadChip (HM450). We defined 94 gene promoters that were hypomethylated significantly by guadecitabine, with 1,659 genes differentially expressed in pretreatment versus posttreatment tumors. Pathway analysis revealed that the experimental regimen significantly altered immune reactivation and DNA repair pathways. Progression-free survival correlated with baseline expression levels of 1,155 genes involved in 25 networks. In functional investigations in ovarian cancer cells, engineered upregulation of certain signature genes silenced by promoter methylation (DOK2, miR-193a, and others) restored platinum drug sensitivity. Overall, our findings illuminate how inhibiting DNA methylation can sensitize ovarian cancer cells to platinum drugs, in large part by altering gene expression patterns related to DNA repair and immune activation, with implications for improving the personalized care and survival outcomes of ovarian cancer patients. Significance: Epigenomic targeting may improve therapeutic outcomes in platinum-resistant and recurrent ovarian cancer in part by effects on DNA repair and antitumor immune responses. Cancer Res; 78(3); 631–44. ©2017 AACR.

Introduction: Hypomethylating agents (HMAs) such as decitabine (DEC) or azacitidine (AZA) are FDA approved therapies for patients with different myeloid malignancies as single agent or in combination with venetoclax. Both DEC and AZA require IV infusion for 1 hour or subcutaneous (SC) injections daily for 5-7 days of every 28-day treatment cycle. They both have limited oral bioavailability due to rapid degradation by cytidine deaminase (CDA) in the gut and liver. An orally bioavailable HMA option could reduce clinic visit frequency and reduce infusions/injections related adverse events and burden. ASTX727 is an oral tablet comprised of a fixed-dose combination (FDC) of CDA inhibitor cedazuridine (C) at 100 mg with DEC at 35 mg. In a phase 2 study, C-DEC (ASTX727) demonstrated pharmacokinetic (PK) AUC exposure similar to IV-DEC at 20mg/m2 with comparable clinical activity and safety (Garcia-Manero, et al, 15th Int'l MDS Symposium, 2019). We describe here the results of a phase 3 study designed to demonstrate exposure bioequivalence of oral C-DEC and IV-DEC and generate clinical data using C-DEC in a larger population (ASCERTAIN study). Methods: The study used a randomized cross over design where patients were randomized 1:1 to either Sequence A: C-DEC (100 mg/35 mg respectively) in Cycle 1 followed by IV-DEC at 20 mg/m2 in Cycle 2, or Sequence B receiving IV-DEC in Cycle 1 followed by C-DEC on Cycle 2 to compare PK (primary endpoint AUC equivalence over 5 days of dosing) and pharmacodynamic (PD) of DNA demethylation using LINE-1 assay. All patients received C-DEC in all subsequent cycles from Cycle 3 onwards until treatment discontinuation to study clinical efficacy and safety of C-DEC. Patients were eligible as per the FDA-approved label (MDS IPSS Intermediate [Int]-1,-2 or high risk[HR] and CMML patients). Clinical responses were assessed by an independent expert panel according to International Working Group (IWG) 2006 response criteria. Adverse events (AEs) were graded by Common Terminology Criteria for Adverse Events (CTCAE) v 4.03. Results: 138 patients were randomized, of whom 133 were treated with median age of 71.0 years (range 44-88), median weight was 83.1 kg (range 45-158), and median BSA was 1.99 m2 (range 1.4-2.9 m2). The IPSS status of the patients were Int-1 in 44%, Int-2 in 20%, and HR in 16%, and 12% of pts had CMML. Patients in the two arms were well balanced regarding cytogenetic risk, baseline hemoglobin, neutrophils, platelets, or red blood cell or platelet transfusion dependence. For the primary end point, the decitabine AUC0-24 (h*ng/mL) 5-Day geometric mean estimate was 856 from the C-DEC and 865 from IV-DEC resulting in an oral/IV AUC ratio of 98.9% (90% CI of 92.7-105.6%). All sensitivity and secondary exposure analyses confirmed the primary results. Comparison of hypomethylating activity as measured by LINE-1 demethylation showed difference between oral C-DEC and IV-DEC demethylation of Summary/Conclusions: This randomized phase 3 study demonstrates that C-DEC, the oral FDC of cedazuridine/decitabine (100 mg/35 mg) resulted in an equivalent DEC exposure to IV-DEC at 20 mg/m2 over 5 days. Safety findings are consistent with those anticipated with IV-DEC with no clinically significant GI toxicity. Preliminary clinical activity is also consistent with published data from IV-DEC. C-DEC is an oral HMA alternative to IV-DEC. Combination studies with other oral agents are being planned. Disclosures Garcia-Manero: Amphivena: Consultancy, Research Funding; Helsinn: Research Funding; Novartis: Research Funding; AbbVie: Research Funding; Celgene: Consultancy, Research Funding; Astex: Consultancy, Research Funding; Onconova: Research Funding; H3 Biomedicine: Research Funding; Merck: Research Funding. Griffiths:New Link Genetics: Consultancy; Astex Phramaceuticals/Otsuka Pharmaceuticals: Consultancy, Research Funding; Persimmune: Consultancy; Boston Scientific: Consultancy; Genentech, Inc.: Research Funding; Genentech, Inc.: Research Funding; Novartis Inc.: Consultancy; Novartis Inc.: Consultancy; Partner Therapeutics: Consultancy; Astex Phramaceuticals/Otsuka Pharmaceuticals: Consultancy, Research Funding; Onconova Therapeutics: Other: PI on a clinical trial; Celgene, Inc: Consultancy, Research Funding; Abbvie, Inc.: Consultancy; Celgene, Inc: Consultancy, Research Funding; Persimmune: Consultancy; Partner Therapeutics: Consultancy; Boston Scientific: Consultancy; New Link Genetics: Consultancy; Onconova Therapeutics: Other: PI on a clinical trial; Abbvie, Inc.: Consultancy, PI on a clinical trial; Appelis Pharmaceuticals: Other: PI on a clinical trial; Appelis Pharmaceuticals: Other: PI on a clinical trial. Yee:Celgene: Honoraria, Research Funding; Novartis: Honoraria, Research Funding. Zeidan:Ariad: Honoraria; Acceleron Pharma: Consultancy, Honoraria, Research Funding; Celgene Corporation: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Honoraria, Research Funding; Otsuka: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; Medimmune/AstraZeneca: Research Funding; Astellas: Honoraria; Seattle Genetics: Honoraria; Cardinal Health: Honoraria; Novartis: Honoraria; Agios: Honoraria; Daiichi Sankyo: Honoraria; BeyondSpring: Honoraria; Boehringer-Ingelheim: Consultancy, Honoraria, Research Funding; Trovagene: Consultancy, Honoraria, Research Funding; Incyte: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Research Funding; ADC Therapeutics: Research Funding; Jazz: Honoraria. Al-Kali:Astex Pharmaceuticals, Inc.: Research Funding. Dao:Incyte Corporation: Membership on an entity's Board of Directors or advisory committees, Research Funding. Patel:Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Dava Oncology: Honoraria; France Foundation: Honoraria. Sabloff:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; ASTX: Membership on an entity's Board of Directors or advisory committees, Research Funding; Sanofi Canada: Research Funding; Actinium Pharmaceuticals, Inc: Membership on an entity's Board of Directors or advisory committees; Pfizer Canada: Honoraria, Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees; Astellas Pharma Canada: Honoraria, Membership on an entity's Board of Directors or advisory committees. Keating:Sanofi: Membership on an entity's Board of Directors or advisory committees; Hoffman La Roche: Membership on an entity's Board of Directors or advisory committees; Shire: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Consultancy; Celgene: Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria. Fazal:Janssen: Honoraria, Speakers Bureau; Takeda: Honoraria, Speakers Bureau; Gilead: Consultancy, Honoraria, Speakers Bureau; Pfizer: Speakers Bureau; Novartis: Consultancy, Honoraria, Speakers Bureau; Incyte: Consultancy, Honoraria, Speakers Bureau; BMS: Consultancy, Honoraria, Speakers Bureau; Jazz: Consultancy, Honoraria, Speakers Bureau; Celgene: Speakers Bureau; Karyopharm: Honoraria, Speakers Bureau. Odenike:AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen Oncology: Research Funding; Astra Zeneca: Research Funding; Gilead Sciences: Research Funding; Agios: Research Funding; CTI/Baxalta: Research Funding; Astex Pharmaceuticals: Research Funding; Incyte: Research Funding; NS Pharma: Research Funding; Oncotherapy: Research Funding. DeZern:Astex Pharmaceuticals, Inc.: Consultancy; Celgene: Consultancy. O'Connell:Astex: Membership on an entity's Board of Directors or advisory committees, Research Funding; Genentech: Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Shionogi: Membership on an entity's Board of Directors or advisory committees. Roboz:Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Jazz: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Orsenix: Consultancy, Membership on an entity's Board of Directors or advisory committees; Otsuka: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Trovagene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees; Sandoz: Consultancy, Membership on an entity's Board of Directors or advisory committees; Roche/Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees; MEI Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Eisai: Consultancy, Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celltrion: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bayer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Actinium: Consultancy, Membership on an entity's Board of Directors or advisory committees; Agios: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amphivena: Consultancy, Membership on an entity's Board of Directors or advisory committees; Argenx: Consultancy, Membership on an entity's Board of Directors or advisory committees; Astex: Consultancy, Membership on an entity's Board of Directors or advisory committees. Oganesian:Astex Pharmaceuticals, Inc.: Employment. Hao:Astex Pharmaceuticals, Inc.: Employment. Keer:Astex Pharmaceuticals, Inc.: Employment. Azab:Astex Pharmaceuticals, Inc.: Employment. Savona:Incyte Corporation: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene Corporation: Membership on an entity's Board of Directors or advisory committees; AbbVie: Membership on an entity's Board of Directors or advisory committees; Boehringer Ingelheim: Patents & Royalties; Sunesis: Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; TG Therapeutics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Selvita: Membership on an entity's Board of Directors or advisory committees; Karyopharm Therapeutics: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees.

Epithelial ovarian cancer (OC) is the most lethal gynecologic malignancy. The majority of advanced stage patients develop uniformly fatal resistance to standard platinum-based treatments. Epigenetic changes, particularly DNA methylation aberrations have been implicated in acquired resistance to platinum in OC. The goal of the current study was to identify methylation changes associated with the development of acquired resistance to platinum-based chemotherapy. We hypothesized that OC tumors harboring an aberrant DNA methylome could be reversed by DNMTi and re-sensitized to platinum treatment. To achieve our objective, we generated and compared tumor DNA methylation profiles from patients with recurrent platinum-resistant OC treated on a clinical trial with a DNA methyl transferase inhibitor, guadecitabine, before (n=65) and after (n=19) treatment (NCT01696032), and patients with primary (platinum-naïve) OC (n=20). Human ovarian surface epithelial cells (HOSE) were used as controls (n=5). We examined methylation levels across the genome using the Infinium Human Methylation 450 Bead Chip (Illumina). By comparing the methylome of platinum naive and platinum resistant ovarian tumors, normalized to HOSE, we identified 444 CpG island-containing gene promoters that became hypermethylated in resistant tumors. Of those, 45 gene promoters were hypermethylated at an FDR0.1. Among those significantly hypermethylated genes, acquired promoter CpG island methylation of Ras Association Domain Family 1A (RASSF1A; a tumor suppressor gene in multiple cancer types) was observed. Of the 444 hypermethylated promoters in tumor resistant samples, 93 CpG islands became hypomethylated after guadecitabine treatment, suggesting that these promoters may be associated with reversal of resistance. Of those were the IFNA8 promoter, a gene known to be associated with anti-tumor effects in ovarian and other solid malignancies, and DEFB124, which is involved in the innate immune response. Pathways associated with immune reactivation were highly enriched by guadecitabine treatment, including IL-12 signaling and production of macrophages and MAPK and apoptosis signaling. Together, these results support that aberrant DNA methylation affecting gene networks associate with immune response plays a role in platinum resistant development and could be a therapeutic target. Citation Format: Fang Fang, Horacio Cardenas, Guanglong Jiang, Susan M. Perkins, Chi Zhang, Harold Keer, Yunlong Liu, Daniela Matei, Kenneth Nephew. Epigenomic signatures of acquired platinum resistance in high grade serous ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2997.

Pancreatic ductal adenocarcinoma (PDAC) is expected to be the second leading cause of cancer mortality by 2030. PDAC remains resistant to the majority of systemic chemotherapies. In this paper, we explore if epigenetic sensitization can improve chemotherapy response in PDAC. Multiple PDAC cell lines were tested with serial concentrations of the epigenetic modulators 5-azacitidine (Aza) and guadecitabine (SGI-110). Guadecitabine was effective at inhibiting the expression of DNA Methyltransferase 1 (DNMT1) and in decreasing cell viability at nanomolar concentrations. We also report that guadecitabine has increased efficacy following a delay period or as we reference, a 'rest period'. Sensitization with guadecitabine improved response to the chemotherapeutic agent-Irinotecan- as measured by decreased cell viability and accompanied by an increase in caspase activity. Additional studies are needed to understand the mechanism of action.

Background: We report dose escalation results from a phase 1/2 trial of ASTX660 (NCT02503423). This non-peptidomimetic, dual XIAP and cIAP antagonist inhibits tumor cell lines at nanomolar concentrations and is active against xenografts. Methods: Study ASTX660-01, an open-label, multi-center, dose-escalation study in subjects with advanced cancers and lymphomas, used a 3+3 dose escalation design. Study drug was administered orally once daily in 28 day cycles of alternating 7 days on, then 7 days off therapy. Dose escalation was planned from a starting fixed 15 mg dose until the maximum tolerated dose (MTD) was reached. Endpoints included safety, MTD, recommended phase 2 dose (RP2D), pharmacokinetics, pharmacodynamics, and antitumor effects. Results: Forty-five subjects received at least 1 dose of ASTX660 (range 15 mg - 270 mg). Mean age was 62 years (range 36-77); 60% of subjects were female. Median duration of study therapy was 2 cycles (range 1-8). Four dose-limiting toxicities (DLTs) were observed: 3 at 270 mg QD (grade 3/4 lipase increased), and 1 at 210 mg QD (grade 3 lipase increased). These lipasemia DLTs were all asymptomatic. Most declined after dose interruption and did not recur after dose reduction. The MTD was 210 mg QD, and the RP2D was 180 mg QD. Common adverse events (AEs) included fatigue, lipasemia, and vomiting (29%); nausea and lymphopenia (27%); anemia (24%); rash and edema (20%); ALT increase and pruritus (18%); AST increase (16%); appetite decrease and diarrhea (13%); and amylasemia and hyponatremia (11%). Lipasemia and amylasemia appeared to be dose-related. Most AEs were CTCAE grades 1-2 and manageable with supportive treatment. Median time to peak plasma concentration (tmax) was 1 hour. ASTX660 t ½ was 15.3 hours at the RP2D. Day 1 and 7 AUC0-24h plasma exposures after 180 mg ASTX660 were 1450 (67%) and 2080 (62%) ng*hr/mL (geometric mean [CV]), respectively. Modest accumulation (1.4 fold) at Day 7 vs Day 1 was observed for ASTX660 AUC0-24h exposures but not for Cmax. Human RP2D exposure levels reached the biologically active exposure range seen in preclinical models. ASTX660 at all dose levels suppressed cIAP1 in peripheral blood mononuclear cells (PBMCs). At 180 mg cIAP1 suppression was sustained beyond the off-therapy week. A clinical response in cutaneous T cell lymphoma was observed at the 180-mg dose level. Conclusions: In phase 1, ASTX660 caused manageable toxicities, achieved target study drug exposures, and demonstrated both biologic and clinical activity at the RP2D. Enrollment to phase 2 expansion cohorts in lymphoma and other selected cancers is ongoing. Citation Format: Monica Mita, Patricia LoRusso, Michael S. Gordon, Aram Oganesian, Xiaoping Zhang, Roberta Ferraldeschi, Simone Jueliger, Harold N. Keer, Purvee Kumar, Chihche Lin, Edwin P. Rock, Alain Mita, Anthony W. Tolcher. Phase 1 study of IAP inhibitor ASTX660 in adults with advanced cancers and lymphomas [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A091.

TPS2617 Background: The 90kDa heat shock chaperone protein (HSP90) exerts housekeeping functions within cells. HSP90 participates in the folding, stabilization, activation, and proteolytic turnover of mutant or over-expressed “client proteins” that contribute to the growth and survival of cancer cells. HSP90 inhibition leads to degradation of these aberrant proteins through the ubiquitin-proteasome pathway, allowing for simultaneous targeting of multiple pathways. Inhibition of HSP90 alone stimulates a compensatory upregulation of HSP70, which is anti-apoptotic at the pre-mitochondrial, mitochondrial and post-mitochondrial levels. The transcriptional induction of HSP70 has been linked to the activity of CDK9. In vitro and in vivo studies show that disruption of HSP70 induction by CDK9 inhibition can augment HSP90 inhibitor responses. Combined inhibition of HSP90 and CDK9 may produce synergistic anti-tumor activity. Methods: We are conducting an a phase I trial of the combination of the HSP90 inhibitor onalespib, and the CDK9 inhibitor AT7519, utilizing a 3+3 trial design, with dose-limiting toxicities defined during cycle 1. Estimated enrollment: 37 patients. Onalespib and AT7519M are both administered on days 1, 4, 8, and 11 of a 21-day cycle following a 1-week lead-in of onalespib alone to facilitate PK/PD endpoints. Patients must have histologically confirmed solid tumors that have progressed on standard of care therapy or for which no standard treatment exists, with an ECOG 0-1. Exclusion criteria include a prolonged QTc interval (Fridericia formula), pre-existing retinal disease, or cardiac dysfunction with EF < 50% at study entry. Current pharmacodynamic analyses include the analysis of HSP70 expression in plasma and peripheral blood mononuclear cells after treatment with onalespib, and after the combination, as proof-of-principle of target inhibition. At this time, DL1 has completed enrollment; accrual is ongoing with measurement of HSP90 client proteins and HSP70 levels in patient plasma and PBMC samples. This trial is open through the ETCTN. Clinical trial information: NCT02503709.

9059Background: Crizotinib (C) was the first approved ALK inhibitor for use in in ALK positive (pos) NSCLC, but resistance ultimately develops through both ALK-related and other signaling pathways....

5547Background: Development of resistance to platinum (P) is fatal in OC and epigenetic changes are linked to this process; a previous phase II study demonstrated efficacy of decitabine and carbopl...

Purpose: Epigenetic changes, particularly in DNA methylation, have been implicated in acquired resistance to platinum in ovarian cancer (OC). The goal of the current study was to analyze and integrate global RNA expression and DNA methylation profiles of platinum resistant tumors compared to untreated, platinum-sensitive ovarian tumors, as well as to measure genomic and epigenomic changes induced by guadecitabine (SGI-110) in tumors. Methods: An ongoing phase I/II multi-institutional clinical trial uses the novel DNA methyltransferase (DNMT) inhibitor guadecitabine to re-sensitize recurrent platinum resistant OC to carboplatin. Patients enrolled in this trial had recurrent platinum resistant OC. Tumor biopsies were collected at baseline and after two cycles of guadecitabine administered daily for 5 days at a low (30mg/m2) dose (28 days per cycle). RNA and DNA were extracted from 48 and 57 baseline tumors and analyzed for next generation sequencing approaches to interrogate transcriptomes (RNA-seq) and methylomes (Infinium Human Methylation450 (HM450) arrays), respectively. Differential gene expression and DNA methylation profiles were generated and used for Ingenuity Pathway Analysis (IPA) to identify the top altered pathways in response to guadecitabine. Expression of DNMTs was examined by real-time RT-PCR and immunohistochemistry. LINE1 methylation and promoter methylation of selected genes (MAGE-A2, MAGE-A3, MAGE-A11, NY-ESO, RASSF1, MLH1, and HOXA11) were quantified by pyrosequencing before and after guadecitabine treatment (n=12 paired samples). Results: Analysis of a limited number of paired samples before and after treatment (n=8) revealed significant changes in global gene expression profiles induced by guadecitabine, with 960 altered genes representing immunopathway enrichment including cytokine production in macrophages and T helper cells by IL-17A and IL-17F, granulocyte /agranulocyte adhesion and inflammation, IL-8 signaling, p38 MAPK signaling, cAMP-mediated signaling, and innate immunity. Epigenetic profiling using HM450 revealed extensive methylation changes when comparing recurrent platinum resistant ovarian tumors (n=42) to primary, untreated ovarian cancer specimens analyzed as part of the TCGA project (n=10). Six hundred and four promoters were significantly differentially methylated (adjusted p0.2), among which, 498 and 106 were hypermethylated or hypomethylated respectively in recurrent platinum resistant ovarian tumors. IPA analysis of baseline tumor transcriptome and methylome demonstrated significant enrichment in a wide range of pathways associated with cancer, stem cells, inflammation and the immune system. DNMT1, 3A, and 3B mRNA levels in the tumors were highly variable (n=19). Analysis of a limited number of paired samples (n=7) revealed no significant changes in global methylation or in DNMT expression levels induced by treatment with guadecitabine (adjusted p>0.05). However, the DNMT inhibitor induced significant methylome alterations in selected patients. Significant hypomethylation of MAGE-A3 and MAGE–A11 promoters (p Conclusions: These data suggest that treatment with the DNMT inhibitor guadecitabine induces a reactivation of immune responses in human OC. Correlations between methylation changes and expression profiles are being explored. Citation Format: Fang Fang, Horacio Cardenas, Dave Miller, Aaron Buechlein, Qing Yu, Yunlong Liu, Guanglong Jiang, Pietro Taverna, Harold Keer, Doug Rusch, Daniela Matei, Kenneth P. Nephew. Epigenome and genome alterations in platinum resistant ovarian tumors. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: Exploiting Vulnerabilities; Oct 17-20, 2015; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(2 Suppl):Abstract nr A70.

Background: HCC is the sixth most common cancer and the third most common cause of cancer death worldwide. Sorafenib treatment improves survival in advanced disease, but no therapy has demonstrated significant activity after progression on sorafenib. Increased methylation of genes implicated in tumorigenesis has been described in HCC and has been associated with outcome and etiology. We evaluated the therapeutic and biologic effects of SGI-110, a hypomethylating agent in patients with HCC. SGI-110, a dinucleotide of decitabine and deoxyguanosine, increases decitabine exposure by protecting it from deamination due to slow release on subcutaneous (SC) injection. PK and PD results of an open-label, phase 2 study in patients with HCC are presented here. Methods: Adults with histologically confirmed, advanced-stage HCC who had received sorafenib, had evidence of disease progression, and ECOG PS 0-1 were enrolled. SGI-110 (SC) was given on D1-5 of a 28-day cycle. Blood samples were taken for PK/PD analysis and, when possible, paired tumor biopsies were taken for analysis of global DNA (LINE-1) and gene-specific methylation and gene expression. Patients were imaged every 8 weeks and allowed to continue treatment after radiologic but not clinical progression. End points include disease control rate (DCR) at 16 weeks, overall response rate, progression-free survival, and overall survival. Results: 50 HCC patients (43M/7F; median age 60 years [range 32-82]; ECOG PS 0/1: 21/29) were enrolled. The initial dose of SGI-110 was 60 mg/m2 (4 patients treated), but due to grade 4 neutropenia, the dose was decreased to 45 mg/m2 for subsequent patients. SGI 110 was well tolerated at 45 mg/m2; myelosuppression was the major adverse event. Full PK was available from 16 patients (3F/13M). The PK profile for SGI-110 after 45 mg/m2 showed protracted conversion to deliver active metabolite decitabine with exposure window lasting beyond 8-hr and mean(SD) decitabine AUC exposures of 94(22) ng*hr/mL that were comparable to those achieved in AML/MDS after 60 mg/m2. Potent LINE-1 demethylation was observed in blood (-35.6%, n = 27) and in tumor (-12.9%, n = 10) DNA; significant demethylation (-27.4%, n = 6) was also observed on promoter of tumor suppressor gene MZB1 which is frequently hypermethylated and silenced in HCC. Conclusions: SGI-110 was well tolerated at a dose of 45 mg/m2 administered SC on D1-5 of a 28-day cycle. PK was consistent with that seen in another solid tumor study and provided more persistent decitabine exposures compared with PK in hematologic malignancies. The PD changes in blood and tumor LINE-1 and MZB-1 methylation are promising and consistent with the desired biologic effect of SGI-110. Analysis for clinical efficacy is ongoing. Citation Format: Anthony El-Khoueiry, Mary F. Mulcahy, Tanios Bekaii-Saab, Richard Kim, Crystal Denlinger, Rakesh Goel, Shweta Gupta, Simone Jueliger, Aram Oganesian, Harold Keer, John Nemunaitis. Pharmacodynamic (PD) and pharmacokinetic (PK) results of the second-generation hypomethylating agent, SGI-110, in patients with hepatocellular carcinoma (HCC) after progression on sorafenib. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2947. doi:10.1158/1538-7445.AM2015-2947

5555 Background: Epigenetic changes, particularly DNA methylation aberrations have been implicated in acquired resistance to platinum in ovarian cancer (OC). Methods: An ongoing phase I/II multi-in...