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BackgroundAcute myeloid leukemia (AML) is fatal in elderly patients who are unfit for standard induction chemotherapy. The objective of this study was to evaluate the survival benefit of administering sapacitabine, an oral nucleoside analogue, in alternating cycles with decitabine, a low-intensity therapy, to elderly patients with newly diagnosed AML.MethodsThis randomized, open-label, phase 3 study (SEAMLESS) was conducted at 87 sites in 11 countries. Patients aged ≥70 years who were not candidates for or chose not to receive standard induction chemotherapy were randomized 1:1 to arm A (decitabine in alternating cycles with sapacitabine) received 1-hour intravenous infusions of decitabine 20 mg/m2 once daily for 5 consecutive days every 8 weeks (first cycle and subsequent odd cycles) and sapacitabine 300 mg twice daily on 3 consecutive days per week for 2 weeks every 8 weeks (second cycle and subsequent even cycles) or to control arm C who received 1-hour infusions of decitabine 20 mg/m2 once daily for 5 consecutive days every 4 weeks. Prior hypomethylating agent therapy for preexisting myelodysplastic syndromes or myeloproliferative neoplasms was an exclusion criterion. Randomization was stratified by antecedent myelodysplastic syndromes or myeloproliferative neoplasms, white blood cell count (

Background In neuroblastoma, genetic alterations in ATRX, define a distinct poor outcome patient subgroup. Despite the need for new therapies, there is a lack of available models and a dearth of pre-clinical research. Methods To evaluate the impact of ATRX loss of function (LoF) in neuroblastoma, we utilized CRISPR-Cas9 gene editing to generate neuroblastoma cell lines isogenic for ATRX. We used these and other models to identify therapeutically exploitable synthetic lethal vulnerabilities associated with ATRX LoF. Findings In isogenic cell lines, we found that ATRX inactivation results in increased DNA damage, homologous recombination repair (HRR) defects and impaired replication fork processivity. In keeping with this, high-throughput compound screening showed selective sensitivity in ATRX mutant cells to multiple PARP inhibitors and the ATM inhibitor KU60019. ATRX mutant cells also showed selective sensitivity to the DNA damaging agents, sapacitabine and irinotecan. HRR deficiency was also seen in the ATRX deleted CHLA-90 cell line, and significant sensitivity demonstrated to olaparib/irinotecan combination therapy in all ATRX LoF models. In-vivo sensitivity to olaparib/irinotecan was seen in ATRX mutant but not wild-type xenografts. Finally, sustained responses to olaparib/irinotecan therapy were seen in an ATRX deleted neuroblastoma patient derived xenograft. Interpretation ATRX LoF results in specific DNA damage repair defects that can be therapeutically exploited. In ATRX LoF models, preclinical sensitivity is demonstrated to olaparib and irinotecan, a combination that can be rapidly translated into the clinic. Funding This work was supported by Christopher's Smile, Neuroblastoma UK, Cancer Research UK, and the Royal Marsden Hospital NIHR BRC.

Background: Sapacitabine is a novel, orally bioavailable, cytosine nucleoside analogue with a unique mechanism that generates single-stranded DNA breaks which are converted into double-stranded DNA breaks resulting in cell death. Previous studies of sapacitabine alone and alternating with decitabine (DAC) have demonstrated activity in acute myeloid leukemia (AML). Preclinical studies have suggested synergy with the combination of sapacitabine and a BCL-2 inhibitor. We conducted a study investigating the combination of sapacitabine and venetoclax (VEN) as an entirely oral regimen for patients with relapsed/refractory (R/R) AML. Methods: This is a phase I/II study for patients ≥ 18 years with R/R AML or MDS with blasts ≥10% investigating the safety and efficacy of escalating doses of sapacitabine combined with VEN. Eligibility included ECOG performance status ≤ 2 and adequate organ function. Two cohorts were investigated: Cohort 1 studied sapacitabine given PO BID on D1-5; Cohort 2 studied sapacitabine given PO BID on D1-3 and D8-10 of each cycle, which was defined as 4 weeks. Sapacitabine was escalated from a starting dose of 250mg. VEN was given to a target dose of 400mg PO on D1-14 of each cycle. VEN ramp-up was utilized, starting at 100mg on D1, 200mg on D2, and 400mg on days 3 through 14. Adjustments to the VEN dose were made based on concomitant CYP3A inhibitors. Results: Between 03/2020 and 03/2021, 13 pts were enrolled in the study. Baseline characteristics are shown in table 1. The median age was 70 years (range, 30-82) and 8 pts (62%) were aged ≥ 70 years. One pt (7%%) had favorable risk, 3 (23%) had intermediate risk, and 9 (70%) had adverse risk karyotype; 5 pts (38%) had a complex karyotype. The most common mutations detected by next-generation sequencing were: TET2 (46%), ASXL1 (30%), NRAS (30%), and WT1 (23%%). One patient (8%) had a TP53 mutation. This was a heavily pretreated population, having received a median of 2 prior therapies (1 - 9), including 6 patients (46%) having received prior intensive chemotherapy and 4 patients (30%) with prior allogeneic SCT. Six patients (46%) had received prior VEN-based therapy. Among 13 evaluable patients, there was 1 (8%) complete response with incomplete platelet recovery (CRp). Patients received a median of 1 cycle (1-9) on protocol. Five patients (38%) were able to remain on protocol without a protocol defined response, but with clinical benefit and good tolerability, for ≥2 cycles. With a median follow up of 14.61 months (1-16), the median overall survival (OS) was 3.8 months with a 60-day survival rate of 76% (Figure 1). There was no significant difference in OS between the two dosing schedules. The median OS among patients that had and had not received prior VEN was 3.32 months and 4.5 months, respectively (P=0.25). The patient that achieved a CRi had secondary AML with 7q deletion, an ASXL1 mutation, and only single-agent DAC as prior therapy. The oral chemotherapy combination was well tolerated, with 4- and 8-week mortality of 8% and 15%, respectively. The most common grade 3/4 non-hematologic adverse events regardless of attribution were: febrile neutropenia (31%), cellulitis (23%) pneumonia (15%), hypophosphatemia (8%), hypokalemia (8%). Two patients (15%) had grade 5 sepsis on study in the setting of active AML. Conclusion: In a heavily pretreated population of patients with R/R AML, the combination of sapacitabine and VEN was well tolerated and feasible to be administered as a completely oral, outpatient regimen. Most patients had multiple prior cycles of nucleoside analogue containing regimens and the only notable responder had only prior DAC. Further study of this well-tolerated combination in less heavily pretreated patients may be considered. Figure 1 Figure 1. Disclosures Kantarjian: Jazz: Research Funding; Novartis: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Amgen: Honoraria, Research Funding; Aptitude Health: Honoraria; NOVA Research: Honoraria; Ascentage: Research Funding; Ipsen Pharmaceuticals: Honoraria; Astra Zeneca: Honoraria; Astellas Health: Honoraria; BMS: Research Funding; Daiichi-Sankyo: Research Funding; KAHR Medical Ltd: Honoraria; Immunogen: Research Funding; AbbVie: Honoraria, Research Funding; Precision Biosciences: Honoraria; Taiho Pharmaceutical Canada: Honoraria. DiNardo: Novartis: Honoraria; Forma: Honoraria, Research Funding; Foghorn: Honoraria, Research Funding; GlaxoSmithKline: Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria; Agios/Servier: Consultancy, Honoraria, Research Funding; Bristol Myers Squibb: Honoraria, Research Funding; ImmuneOnc: Honoraria, Research Funding; AbbVie: Consultancy, Research Funding; Notable Labs: Current holder of stock options in a privately-held company, Membership on an entity's Board of Directors or advisory committees; Celgene, a Bristol Myers Squibb company: Honoraria, Research Funding. Borthakur: GSK: Consultancy; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Protagonist: Consultancy; Takeda: Membership on an entity's Board of Directors or advisory committees; University of Texas MD Anderson Cancer Center: Current Employment; ArgenX: Membership on an entity's Board of Directors or advisory committees; Astex: Research Funding; Ryvu: Research Funding. Daver: ImmunoGen: Consultancy, Research Funding; Trovagene: Consultancy, Research Funding; Abbvie: Consultancy, Research Funding; Astellas: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Daiichi Sankyo: Consultancy, Research Funding; Amgen: Consultancy, Research Funding; FATE Therapeutics: Research Funding; Gilead Sciences, Inc.: Consultancy, Research Funding; Trillium: Consultancy, Research Funding; Bristol Myers Squibb: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; Glycomimetics: Research Funding; Novimmune: Research Funding; Hanmi: Research Funding; Sevier: Consultancy, Research Funding; Novartis: Consultancy; Jazz Pharmaceuticals: Consultancy, Other: Data Monitoring Committee member; Dava Oncology (Arog): Consultancy; Celgene: Consultancy; Syndax: Consultancy; Shattuck Labs: Consultancy; Agios: Consultancy; Kite Pharmaceuticals: Consultancy; SOBI: Consultancy; STAR Therapeutics: Consultancy; Karyopharm: Research Funding; Newave: Research Funding. Pemmaraju: Dan's House of Hope: Membership on an entity's Board of Directors or advisory committees; Celgene Corporation: Consultancy; ASH Communications Committee: Membership on an entity's Board of Directors or advisory committees; Sager Strong Foundation: Other; Daiichi Sankyo, Inc.: Other, Research Funding; HemOnc Times/Oncology Times: Membership on an entity's Board of Directors or advisory committees; DAVA Oncology: Consultancy; Aptitude Health: Consultancy; Springer Science + Business Media: Other; Roche Diagnostics: Consultancy; Novartis Pharmaceuticals: Consultancy, Other: Research Support, Research Funding; LFB Biotechnologies: Consultancy; ASCO Leukemia Advisory Panel: Membership on an entity's Board of Directors or advisory committees; Incyte: Consultancy; MustangBio: Consultancy, Other; Cellectis S.A. ADR: Other, Research Funding; Samus: Other, Research Funding; Plexxicon: Other, Research Funding; Affymetrix: Consultancy, Research Funding; Stemline Therapeutics, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding; CareDx, Inc.: Consultancy; Abbvie Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding; Protagonist Therapeutics, Inc.: Consultancy; Clearview Healthcare Partners: Consultancy; Blueprint Medicines: Consultancy; Bristol-Myers Squibb Co.: Consultancy; ImmunoGen, Inc: Consultancy; Pacylex Pharmaceuticals: Consultancy. Alvarado: Sun Pharma: Consultancy, Research Funding; Daiichi-Sankyo: Research Funding; Astex Pharmaceuticals: Research Funding; CytomX Therapeutics: Consultancy; BerGenBio: Research Funding; FibroGen: Research Funding; Jazz Pharmaceuticals: Research Funding; MEI Pharma: Research Funding. Burger: AstraZeneca: Consultancy; Beigene: Research Funding, Speakers Bureau; Pharmacyclics LLC: Consultancy, Other: Travel/Accommodations/Expenses, Research Funding, Speakers Bureau; Novartis: Other: Travel/Accommodations/Expenses, Speakers Bureau; Gilead: Consultancy, Other: Travel/Accommodations/Expenses, Research Funding, Speakers Bureau; TG Therapeutics: Other: Travel/Accommodations/Expenses, Research Funding, Speakers Bureau; Janssen: Consultancy, Other: Travel/Accommodations/Expenses, Speakers Bureau. Ravandi: Syros Pharmaceuticals: Consultancy, Honoraria, Research Funding; Jazz: Honoraria, Research Funding; Astex: Honoraria, Research Funding; Taiho: Honoraria, Research Funding; Agios: Honoraria, Research Funding; AbbVie: Honoraria, Research Funding; AstraZeneca: Honoraria; Novartis: Honoraria; Xencor: Honoraria, Research Funding; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Prelude: Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Honoraria, Research Funding. Kadia: AstraZeneca: Other; Ascentage: Other; Jazz: Consultancy; BMS: Other: Grant/research support; AbbVie: Consultancy, Other: Grant/research support; Aglos: Consultancy; Amgen: Other: Grant/research support; Cure: Speakers Bureau; Dalichi Sankyo: Consultancy; Genfleet: Other; Cellonkos: Other; Sanofi-Aventis: Consultancy; Pulmotech: Other; Novartis: Consultancy; Pfizer: Consultancy, Other; Liberum: Consultancy; Genentech: Consultancy, Other: Grant/research support; Astellas: Other.

The mechanism of action of CNDAC (2′-C-cyano-2′-deoxy-1-β-d-arabino-pentofuranosyl-cytosine) is unique among deoxycytidine analogs because upon incorporation into DNA it causes a single strand break which is converted to a double strand break after DNA replication. This lesion requires homologous recombination (HR) for repair. CNDAC, as the parent nucleoside, DFP10917, and as an oral prodrug, sapacitabine, are undergoing clinical trials for hematological malignancies and solid tumors. The purpose of this study is to investigate the potential of CNDAC for the therapy of ovarian cancer (OC). Drug sensitivity was evaluated using a clonogenic survival assay. Drug combination effects were quantified by median effect analysis. OC cells lacking function of the key HR genes, BRCA1 or BRCA2, were more sensitive to CNDAC than corresponding HR proficient cells. The sensitization was associated with greater levels of DNA damage in response to CNDAC at clinically achievable concentrations, manifested as chromosomal aberrations. Three classes of CNDAC-based drug combinations were investigated. First, the PARP1 inhibitors, rucaparib and talazoparib, were selectively synergistic with CNDAC in BRCA1/2 deficient OC cells (combination index

Purpose: The double-strand breaks elicited by sapacitabine, a clinically active nucleoside analogue prodrug, are repaired by RAD51 and the homologous recombination repair (HR) pathway, which could potentially limit its toxicity. We investigated the mechanism by which histone deacetylase (HDAC) inhibitors targeted RAD51 and HR to sensitize acute myelogenous leukemia (AML) cells to sapacitabine. Experimental Design: Chromatin immunoprecipitation identified the role of HDACs in silencing miR-182 in AML. Immunoblotting, gene expression, overexpression, or inhibition of miR-182 and luciferase assays established that miR-182 directly targeted RAD51. HR reporter assays, apoptotic assays, and colony-forming assays established that the miR-182, as well as the HDAC inhibition–mediated decreases in RAD51 inhibited HR repair and sensitized cells to sapacitabine. Results: The gene repressors, HDAC1 and HDAC2, became recruited to the promoter of miR-182 to silence its expression in AML. HDAC inhibition induced miR-182 in AML cell lines and primary AML blasts. miR-182 targeted RAD51 protein both in luciferase assays and in AML cells. Overexpression of miR-182, as well as HDAC inhibition–mediated induction of miR-182 were linked to time- and dose-dependent decreases in the levels of RAD51, an inhibition of HR, increased levels of residual damage, and decreased survival after exposure to double-strand damage-inducing agents. Conclusions: Our findings define the mechanism by which HDAC inhibition induces miR-182 to target RAD51 and highlights a novel pharmacologic strategy that compromises the ability of AML cells to conduct HR, thereby sensitizing AML cells to DNA-damaging agents that activate HR as a repair and potential resistance mechanism. Clin Cancer Res; 22(14); 3537–49. ©2016 AACR.

INTRODUCTION Acute myeloid leukemia (AML) remains a poor prognosis hematological malignancy. The introduction of aggressive chemotherapy with allogeneic stem cell transplantation has resulted in improved clinical outcomes in younger patients. However, the treatment results in unfit elderly AML population remain disappointing. New strategies should be introduced to improve the prognosis in this group of patients. Areas covered: This review presents and discusses the mechanism of action, safety and efficacy of sapacitabine in AML patients. Expert opinion: Sapacitabine, a novel nucleoside analog, seemed to be a promising new agent for AML treatment. Its oral bioavailability and tolerable toxicity profile allow the drug to be used in an outpatient setting, especially in elderly unfit patients. Sapacitabine is known to have antileukemic activity in randomized clinical trials. In AML patients, sapacitabine monotherapy offered no advantage over low-intensity cytarabine treatment, and the combination of sapacitabine with decitabine was not significantly more effective than decitabine alone. However, the oral administration of sapacitabine allows it to be used in AML maintenance therapy.

Introduction: The treatment of acute myelogenous leukemia remains challenging, especially in older adults or those unfit for intensive induction therapy or allogeneic stem cell transplant. Sapacitabine is a novel, rationally-designed, orally administered nucleoside analog that has shown promising activity in early clinical trials in acute myelogenous leukemia. Areas covered: This review covers the biochemical and pharmacologic properties of the drug with a focus on the clinical activity, safety and tolerability of sapacitabine in the treatment of acute myelogenous leukemia. Expert opinion: Sapacitabine is a promising orally administered drug in the treatment of acute myelogenous leukemia. While clinical data have failed to show significant benefit as a single agent, the drug has demonstrated clinical activity as monotherapy. Early clinical data has shown encouraging results in combinations with other agents.

The development of new treatments for older patients with acute myeloid leukaemia (AML) is an active area, but has met with limited success. Sapacitabine is a novel orally administered nucleoside analogue that has shown encouraging activity in unrandomised early-stage trials. We randomised 143 untreated patients with AML or with high-risk myelodysplastic syndrome (>10% marrow blasts) between sapacitibine and low-dose ara-C (LDAC) in our ‘Pick a Winner’ trial design. At the planned interim analysis there was no difference between LDAC and sapacitibine in terms of remission rate (CR/CRi, 27% vs 16% hazard ratio (HR) 1.98(0.90–4.39) P=0.09), relapse-free survival (10% vs 14% at 2 years, HR 0.73(0.33–1.61) P=0.4) or overall survival (OS; 12% vs 11% at 2 years, HR 1.24(0.86–1.78) P=0.2). Sapacitibine was well tolerated, apart from more grade 3/4 diarrhoea. On the basis of these findings sapacitibine did not show sufficient evidence of benefit over LDAC for the trial to be continued.

Acute myeloid leukemia (AML) is characterized by clonal proliferation of neoplastic myeloid precursor cells resulting in impaired hematopoiesis. Despite initial responses to intensive induction therapy, relapses are frequent and most patients die in less than 5 years (National Cancer Institute 2015). Nucleoside analogues represent an important category of anti-leukemic cytotoxic drugs. Cytarabine (Ara-C) is the most active drug against AML; azacitidine and decitabine are active treatments of myelodysplastic syndrome (MDS) and AML. Sapacitabine is a novel, orally bioavailable nucleoside analogue with a unique ability to induce single-strand DNA breaks after incorporation into DNA, leading eventually to production of double-strand DNA breaks and/or G2 cell cycle arrest. In phase 1 and 2 clinical trials, sapacitabine has induced complete remission (CR), CR with incomplete platelet count recovery (CRp), partial remission (PR), and major hematological improvement (HI) in patients with AML and MDS. A subset of these responding patients were previously treated with other nucleoside analogues, suggesting that the anti-leukemic activity of sapacitabine is not limited by resistance to other nucleoside analogues (Kantarjian H et al, JCO, 2010, ASH, 2013). Two clinical studies have demonstrated the synergistic activity of venetoclax in combination with hypomethylating agents or low-dose ara-C in newly diagnosed AML, leading to its recent approval by the FDA for the front-line treatment of this disease. The synergy between venetoclax and cytotoxic therapy in AML models is mediated by combined targeting of the anti-apoptotic BCL2 and MCL1 mechanisms (Teh T-C et al, Leukemia, 2018). Cytotoxic drugs induce apoptosis through genotoxic damage, TP53 activation and increased expression of pro-apoptotic NOXA and PUMA (Villunger A et al, Science, 2003) - features that have also been demonstrated for sapacitabine (Green S et al. Br J Cancer 2010). Although most cytotoxic agents do not directly affect MCL1 levels, increased levels of the pro-apoptotic NOXA and PUMA proteins can inactivate MCL1 to synergize with venetoclax to induce apoptosis. The combination of CNDAC (2'-C-cyano-2'-deoxy-1-β-D-arabino-pentafuranosylcytosine), the active metabolite of sapacitabine, and BCL2 inhibitor ABT737 was studied in AML cell line MV-411. A synergistic increase in apoptosis induction was observed when CNDAC and ABT737 were combined (Frame S. et al, 14th EHA, 2009, Abs 0761). The above findings support the conduct of a clinical study (NCT01211457) evaluating a combination of sapacitabine with venetoclax in patients with relapsed/refractory AML and MDS. This is an entirely oral treatment regimen. The primary objective is to evaluate the safety and efficacy of two dosing schedules of sapacitabine given concomitantly with venetoclax: twice daily for 5 consecutive days or twice daily for 3 consecutive days per week for 2 weeks. One treatment cycle is 4 weeks. Dose will be escalated in increments of 50 mg twice daily. RP2D is the highest dose level at which ≤2 of 6 patients experience a dose-limiting toxicity during the first 2 treatment cycles. Eligible patients are ≥18 years with previously treated AML or MDS and ≥10% blasts in bone marrow or peripheral blood; adequate bone marrow, renal and liver functions are required. Treatment will continue until progression of disease, unacceptable toxicity or changes in patient condition that renders patients ineligible for further treatment. Laboratory tests and bone marrow aspirate/biopsy will be performed to assess responses according to standard criteria. Disclosures Kadia: Bioline RX: Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees; Genentech: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Consultancy, Research Funding; Celgene: Research Funding; Jazz: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Research Funding. Borthakur:Agensys: Research Funding; BMS: Research Funding; Oncoceutics, Inc.: Research Funding; PTC Therapeutics: Consultancy; Eli Lilly and Co.: Research Funding; Janssen: Research Funding; Merck: Research Funding; Polaris: Research Funding; Strategia Therapeutics: Research Funding; Tetralogic Pharmaceuticals: Research Funding; Eisai: Research Funding; Xbiotech USA: Research Funding; Novartis: Research Funding; Oncoceutics: Research Funding; BioLine Rx: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Arvinas: Research Funding; AbbVie: Research Funding; Incyte: Research Funding; AstraZeneca: Research Funding; Bayer Healthcare AG: Research Funding; Argenx: Membership on an entity's Board of Directors or advisory committees; FTC Therapeutics: Membership on an entity's Board of Directors or advisory committees; Cantargia AB: Research Funding; GSK: Research Funding; Cyclacel: Research Funding; BioTheryX: Membership on an entity's Board of Directors or advisory committees; NKarta: Consultancy. Jabbour:Pfizer: Consultancy, Research Funding; Cyclacel LTD: Research Funding; AbbVie: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Adaptive: Consultancy, Research Funding; Amgen: Consultancy, Research Funding; Takeda: Consultancy, Research Funding. Konopleva:Kisoji: Consultancy, Honoraria; Ascentage: Research Funding; Genentech: Honoraria, Research Funding; F. Hoffman La-Roche: Consultancy, Honoraria, Research Funding; Agios: Research Funding; Astra Zeneca: Research Funding; Ablynx: Research Funding; Reata Pharmaceuticals: Equity Ownership, Patents & Royalties; Eli Lilly: Research Funding; Forty-Seven: Consultancy, Honoraria; Stemline Therapeutics: Consultancy, Honoraria, Research Funding; Calithera: Research Funding; Amgen: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria, Research Funding; Cellectis: Research Funding. Ravandi:Macrogenix: Consultancy, Research Funding; Selvita: Research Funding; Menarini Ricerche: Research Funding; Xencor: Consultancy, Research Funding; Cyclacel LTD: Research Funding; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. DiNardo:celgene: Consultancy, Honoraria; medimmune: Honoraria; agios: Consultancy, Honoraria; jazz: Honoraria; syros: Honoraria; daiichi sankyo: Honoraria; abbvie: Consultancy, Honoraria; notable labs: Membership on an entity's Board of Directors or advisory committees. Zheleva:Cyclacel Ltd: Employment, Equity Ownership, Patents & Royalties. Blake:Cyclacel Ltd: Employment, Equity Ownership, Patents & Royalties. Chiao:Cyclacel Ltd: Employment, Equity Ownership, Patents & Royalties.

Introduction: Sapacitabine, a nucleoside analog, and seliciclib, a cyclin-dependent kinase 2/9 inhibitor, constitute a novel oral regimen aimed at augmenting DNA damage and impairing cell cycle checkpoints. The initial phase I cohort investigating this combination demonstrated a 25% response rate in BRCA carriers. Hence, we developed an expansion cohort to assess the safety and efficacy of this regimen in patients with metastatic breast cancer and BRCA1/2 mutations. Methods: We enrolled 20 patients with HER2-negative metastatic breast cancer and germline or somatic BRCA1/2 mutations, who were treated with sapacitabine 50 mg twice daily for days 1-7 followed by seliciclib 800 mg twice daily for days 8-10 of a 21-day cycle. Baseline or archival biopsies underwent RAD51 immunohistochemistry to assess for functional homologous recombination proficiency. Available tissue was sent for whole exome and transcriptome sequencing, and pre- and post-treatment blood was submitted for cell-free DNA sequencing to assess for genomic correlates of response. Results: Participants received a median of 2 prior lines of chemotherapy for metastatic disease. Of the 9 patients who received a prior platinum agent, 6 progressed on this therapy. In addition to chemotherapy, 7 patients received and progressed on a prior PARP inhibitor. The overall response rate for sapacitabine and seliciclib in this cohort was 10%, consisting of 2 patients with partial responses lasting 4.7 and 9.0 months, respectively. The clinical benefit rate (CR + PR + SD ≥ 6 months) was 30%, and durations of stable disease ≥ 6 months ranged from 7.4 to 11.7 months. For all patients, median PFS was 3.7 months. The most frequent grade 3/4 adverse events were neutropenia (25% of patients), transaminitis (20%), and rash (10%). No patients who progressed on prior PARP inhibitor therapy and 6 of 13 patients (46%) with no history of PARP inhibitor resistance experienced clinical benefit (p = 0.052 by Fisher’s exact test). In contrast, 1 of 6 patients (17%) who progressed on prior platinum chemotherapy and 5 of 14 patients (36%) with no history of platinum resistance experienced clinical benefit (p = 0.61 by Fisher’s exact test). Notably, the tumors of some resistant patients harbored BRCA reversion mutations. Additional genomic analyses and RAD51 immunohistochemistry will be presented. Conclusions: The combination of sapacitabine and seliciclib was safe and led to durable clinical benefit in some patients with metastatic breast cancer and BRCA1/2 mutations. Prior progression on PARP inhibitors predicted resistance to this combination, associated in some cases with BRCA reversion mutations. Based on these results, the combination of sapacitabine and the PARP inhibitor olaparib is now being investigated in patients with PARP-naïve metastatic HER2-negative breast cancer and germline BRCA1/2 mutations. Citation Format: Tanya Keenan, David Liu, Haitham Elmarakeby, Daniel Stover, Bose Kochupurakkal, Adam Tracy, Elaine Danielczyk, Leilani Anderson, Chelsea Andrews, Brendan Reardon, Beth Overmoyer, Eric Winer, Daniella Zheleva, Judy Chiao, David Blake, Eliezer Van Allen, Geoffrey I. Shapiro, Sara Tolaney. Expansion cohort of Phase I study of oral sapacitabine and oral seliciclib in patients with metastatic breast cancer and BRCA1/2 mutations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT050.

Therapies for AML have remained mostly unchanged since the introduction of anthracyline- and cytarabine-based regimens in the 1970s. Though some changes have been made in the dosing of anthracylines, in the choice of consolidation regimens versus allogeneic stem cell transplant, and in supportive care, clinical outcomes remain poor for most patients. As we continue to strive for better treatment options to improve upon outcomes, different agents, both chemotherapeutic and targeted therapies, are being studied. Here we discuss new chemotherapeutic agents that show promise in recent clinical trials and attempt to answer the question if there are any new effective cytotoxic chemotherapy agents out there.

Summary Background Available treatments for acute myeloid leukaemia (AML) have limited durable activity and unsatisfactory safety profiles in most elderly patients. We assessed the efficacy and toxicity of sapacitabine, a novel oral cytosine nucleoside analogue, in elderly patients with AML. Methods In this randomised, phase 2 study, we recruited patients with AML who were either treatment naive or at first relapse and who were aged 70 years or older from 12 centres in the USA. We used a computer-generated randomisation sequence to randomly allocate eligible patients to receive one of three schedules of oral sapacitabine (1:1:1; stratified by a history of AML treatment): 200 mg twice a day for 7 days (group A); 300 mg twice a day for 7 days (group B); and 400 mg twice a day for 3 days each week for 2 weeks (group C). All schedules were given in 28 day cycles. To confirm the safety and tolerability of dosing schedules, after 20 patients had been treated in a group we enrolled an expanded cohort of 20–25 patients to that group if at least four patients had achieved complete remission or complete remission with incomplete blood count recovery, and if the 30 day death rate was 20% or less. Our primary endpoint was 1-year overall survival, analysed by intention-to-treat (ie, patients who have received at least one dose of sapacitabine) in those patients who had been randomly allocated to treatment. This trial is registered with ClinicalTrials.gov, number NCT00590187. Results Between Dec 27, 2007, and April 21, 2009, we enrolled 105 patients: 86 patients were previously untreated and 19 were at first relapse. Of the 60 patients randomly allocated to treatment, 1-year overall survival was 35% (95% CI 16–59) in group A, 10% (2–33) in group B, and 30% (13–54) in group C. 14 (13%) of 105 patients died within 30 days and 27 (26%) died within 60 days. The most common grade 3–4 adverse events were anaemia (eight of 40 patients in group A, 12 of 20 patients in group B, and 15 of 45 patients in group C), neutropenia (14 in group A, 10 in group B, 11 in group C), thrombocytopenia (24 in group A, 12 in group B, and 22 in group C), febrile neutropenia (16 in group A, nine in group B, and 22 in group C), and pneumonia (seven in group A, five in group B, and 10 in group C). The most common grade 5 events were pneumonia (two in group A, one in group B, and three in group C) and sepsis (six in group A, three in group B, and one in group C). Seven deaths were thought to be probably or possibly related to sapacitabine treatment. Interpretation Sapacitabine seems active and tolerable in elderly patients with AML. The 400 mg dose schedule had the best efficacy profile. Future investigations should aim to combine sapacitabine with other low-intensity therapies in elderly patients with AML. Funding Cyclacel Limited.

Sapacitabine is an orally bioavailable prodrug of the nucleoside analog 2'-C-cyano-2'-deoxy-1-β-D-arabino-pentofuranosylcytosine (CNDAC). Both the prodrug and active metabolite are in clinical trials for hematologic malignancies and/or solid tumors. CNDAC has a unique mechanism of action: after incorporation into DNA, it induces single-strand breaks (SSBs) that are converted into double-strand breaks (DSBs) when cells go through a second S phase. In our previous studies, we demonstrated that CNDAC-induced SSBs can be repaired by the transcription-coupled nucleotide excision repair pathway, whereas lethal DSBs are mainly repaired through homologous recombination. In the current work, we used clonogenic assays to compare the DNA damage repair mechanism of CNDAC with two other deoxycytidine analogs: cytarabine, which is used in hematologic malignacies, and gemcitabine, which shows activity in solid tumors. Deficiency in two Rad51 paralogs, Rad51D and XRCC3, greatly sensitized cells to CNDAC, but not to cytarabine or gemcitabine, indicating that homologous recombination is not a major mechanism for repairing damage caused by the latter two analogs. This study further suggests clinical activity and application of sapacitabine that is distinct from that of cytarabine or gemcitabine.

For the last twenty years, significant progress in Molecular and Cellular Biology has resulted in a better characterization and understanding of the biology and prognosis of acute myeloid leukemia (AML). These achievements have provided new opportunities for the development of innovative, more effective therapies. Novel agents potentially useful in the treatment of patients with AML include new formulations of established drugs, newer nucleoside analogs, molecular target drugs, monoclonal antibodies and other agents. Three newer nucleoside analogs, clofarabine, troxacitabine and sapacitabine have been recently investigated in patients with AML. Two methylation inhibitors, 5-azacyticline and decitabine are pyrimidine nucleoside analogs of cytidine which can be incorporated into RNA and/or DNA. Lower doses of these agents are active in AML and have been extensively investigated, especially in secondary AML and AML in elderly patients. Tipifarnib and lonafarnib are orally available farnesyltransferase inhibitors with in vitro and in vivo activity against AML. In recent years, FLT3 inhibitors, lestaurinib, tandutinib and PKC 412 have been developed and tested in AML. The preclinical observations and clinical studies indicate that FLT3 inhibitors are promising agents in the treatment of FLT3 mutated AML patients, especially when used in combinations with chemotherapy. Several newer MDR inhibitors, including valspodar (PSC-833) and zosuquidar trihydrochloride have been also tested for the treatment of relapsed AML. This article reviews the various classes of AML targets and drugs that are under early phase clinical evaluation, especially those that are likely to enter clinical practice in the near future.

Coumarin derivative RKS262 belongs to a new class of potential anti-tumor agents. RKS262 was identified by structural optimization of Nifurtimox which is currently undergoing phase II clinical trials to treat high-risk neuroblastoma. In a NCI(60) cell-line assay RKS262 exhibited significant cytotoxicity in ovarian cancer cells and a variety of other cell lines exceeding effects of commercial drugs such as cisplatin, 5-FU, cyclophosphamide or sapacitabine. Various leukemia cell-lines were most sensitive (GI(50): ~ 10 nM) while several non-small cell lung cancer cell lines and few cell lines from other tissues were relatively resistant (GI(50) 1 µM) to RKS262 treatment. The mechanism of cytotoxicity was examined using ovarian cancer cell-line OVCAR-3 as a model. RKS262 treatment resulted in a reduced mitochondria-transmembrane-depolarization potential. RKS262 effects included up-regulation of apoptotic markers and were not correlated with activation of pro-apoptotic MAP-Kinases (p38, SAP/JNK). RKS262 exerted strong inhibitory effects on oncogene ras, down-regulated DNA-pk KU-80 subunit expression and caused activation of Akt. A signature effect of RKS262 is the regulation of the mitochondrial Bcl2-family pathway. Pro-apoptotic factors Bid, Bad and Bok were up-regulated while expression of pro-survival factors Bcl-xl and Mcl-1 was inhibited. Moreover, at sub-cytotoxic doses RKS262 delayed OVCAR-3 cell-cycle progression through G2 phase and up-regulated p27 while cyclin-D1 and Cdk-6 were down-regulated, indicating that RKS262 is a specific cyclin/CDK inhibitor. In summary, RKS262 has been identified as a molecule belonging to a new class of potential chemotherapeutic agents affecting the viability of multiple cancer cell-lines and causing selective adverse effects on the viability of ovarian cancer cells.

Cytotoxic nucleoside analogues are clinically important anticancer drugs. These agents behave as antimetabolites, compete with physiologic nucleosides, and, consequently, interact with a large number of intracellular targets to induce cytotoxicity. Nucleoside analogues share some general common characteristics, namely in terms of requiring transport by specific membrane transporters and intracellular metabolism. However these compounds differ in regard to the preferential interaction with certain targets which may explain why some compounds are more effective against rapidly proliferating tumours and others on neoplasia with a more protracted evolution. Purine and pyrimidine analogues are widely used not only as antileukaemic agents, but also as cytotoxic agents to treat solid tumours. However, the clinical use of these compounds is limited by important side-effects and primary or acquired drug resistance. Thus, there is an unmet medical need for the development of new antimetabolites and for technologies allowing a more suitable and effective administration of nucleoside analogues for the treatment of cancer patients. Here, we will review literature data concerning the recent development of novel purine nucleoside analogues (clofarabine, nelarabine and forodesine) and pyrimidine nucleoside analogues (troxacitabine, sapacitabine, CP-4055, 3'-C-ethynylcytidine and 5-azapyrimidines) that are in evaluation at the clinical level.

PURPOSE OF REVIEW Nucleoside analogs remain a cornerstone in acute myeloid leukemia therapy. As many new nucleosides are being investigated in clinical trials, this review aims to update the current state of experience with these new compounds and where they may fit into treatment strategies for acute myeloid leukemia. RECENT FINDINGS Many new nucleoside analogs are emerging with novel metabolic properties and mechanisms of action. Some have entered clinical trials and are actively investigated in the context of acute myeloid leukemia therapy. Clofarabine is the most-developed compound, and single-agent experience and combinations with other active agents in acute myeloid leukemia are being explored. Troxacitabine and sapacitabine are still in single-agent phases of their development and clinical experience is accumulating quickly. SUMMARY Nucleosides remain the most important class of drugs in acute myeloid leukemia and the interest in new compounds is strong. The plethora of new analogs continues to provide ample opportunity to expand the effectiveness of these drugs in acute myeloid leukemia therapy. Furthermore, their unique mechanisms of action provide possibilities for mechanism-based combinations.

BackgroundCancer control by radiotherapy (RT) can be improved with concurrent chemotherapy. Outpatient strategies for sarcomas that combine chemotherapy and RT are possible since supportive care and RT techniques have improved.MethodsThe current status of non-anthracycline chemotherapy in combination with radiation for high-risk sarcoma is reviewed.ResultsIfosfamide with mesna and newer activated ifosfamide agents (ZIO-201 and glufosfamide) have high potential to improve sarcoma cancer control. In Ewing's sarcoma and osteosarcoma, high-dose ifosfamide with mesna (2.8 g/m2/day of each x 5 days; mesna day 6) can be safely given to outpatients using continuous infusion. Reducing ifosfamide nephrotoxicity and central nervous system side effects are discussed. Other outpatient radiosensitization regimens include gemcitabine (600–1000 mg/m2/dose IV over 1 hour weekly x 2–3 doses), temozolomide (75 mg/m2/daily x 3–6 weeks), or temozolomide (100 mg/m2/dose daily x 5) + irinotecan (10 mg/m2/dose daily x 5 x 2 weeks). In osteosarcoma with osteoblastic metastases on bone scan, samarium (1 mCi/kg; day 3 of RT) and gemcitabine (600 mg/m2IV over 1 hour day 9 of RT) is a radiosensitization strategy. Future drugs for radiosensitization include beta-D-glucose targeted activated ifosfamide (glufosfamide) and sapacitabine, an oral nucleoside with in vitro activity against solid tumors including sarcomas.ConclusionsThe potential to treat major causes of sarcoma treatment failure (local recurrence and distant metastases) with concurrent chemotherapy during radiation should be considered in high-grade sarcomas.

This study assessed the antiproliferative activity of sapacitabine (CYC682, CS-682) in a panel of 10 human cancer cell lines with varying degrees of resistance or sensitivity to the commonly used nucleoside analogues ara-C and gemcitabine. Growth inhibition studies using sapacitabine and CNDAC were performed in the panel of cell lines and compared with both nucleoside analogues and other anticancer compounds including oxaliplatin, doxorubicin, docetaxel and seliciclib. Sapacitabine displayed antiproliferative activity across a range of concentrations in a variety of cell lines, including those shown to be resistant to several anticancer drugs. Sapacitabine is biotransformed by plasma, gut and liver amidases into CNDAC and causes cell cycle arrest predominantly in the G(2)/M phase. No clear correlation was observed between sensitivity to sapacitabine and the expression of critical factors involved in resistance to nucleoside analogues such as deoxycytidine kinase (dCK), human equilibrative nucleoside transporter 1, cytosolic 5'-nucleotidase and DNA polymerase-alpha. However, sapacitabine showed cytotoxic activity against dCK-deficient L1210 cells indicating that in some cells, a dCK-independent mechanism of action may be involved. In addition, sapacitabine showed a synergistic effect when combined with gemcitabine and sequence-specific synergy with doxorubicin and oxaliplatin. Sapacitabine is therefore a good candidate for further evaluation in combination with currently used anticancer agents in tumour types with unmet needs.

More than half of the patients with acute myeloid leukaemia (AML) are older than 60years. The treatment outcomes in this group remain poor with a median overall survival of

Prognosis of elderly patients with acute myeloid leukemia (AML) remains poor and new treatment approaches are urgently needed. A novel nucleoside analog sapacitabine has recently emerged as a feasible agent because of its oral administration and acceptable toxicity profile. Clinical efficacy of sapacitabine, both as a single agent and in combination, has been evaluated in elderly AML patients or AML patients unfit for standard intensive chemotherapy. Response rates varied from 15 to 45% in phase II studies. Sapacitabine was overall well-tolerated with gastrointestinal and myelosuppression-related complications were the most common side effects. Unfortunately, in a phase III study sapacitabine showed no clinical superiority as compared to low-dose cytarabine (LDAC) in patients with AML. Another large phase III study comparing the combination of sapacitabine with decitabine to decitabine alone is currently ongoing and is expected to be completed by the end of 2015 or by the first half of 2016.

CNDAC (2′-C-cyano-2′-deoxy-1-β-d-arabino-pentofuranosyl-cytosine, DFP10917) and its orally bioavailable prodrug, sapacitabine, are undergoing clinical trials for hematologic malignancies and solid tumors. The unique action mechanism of inducing DNA strand breaks distinguishes CNDAC from other deoxycytidine analogs. To optimize the clinical potentials of CNDAC, we explored multiple strategies combining CNDAC with chemotherapeutic agents targeting distinct DNA damage repair pathways that are currently in clinical use. The ability of each agent to decrease proliferative potential, determined by clonogenic assays, was determined in paired cell lines proficient and deficient in certain DNA repair proteins. Subsequently, each agent was used in combination with CNDAC at fixed concentration ratios. The clonogenicity was quantitated by median effect analysis, and a combination index was calculated. The c-Abl kinase inhibitor imatinib had synergy with CNDAC in HCT116 cells, regardless of p53 status. Inhibitors of PARP1 that interfere with homologous recombination (HR) repair or base excision repair (BER) and agents such as temozolomide that cause DNA damage repaired by the BER pathway were also synergistic with CNDAC. The toxicity of the nitrogen mustards bendamustine and cytoxan, or of platinum compounds, which generate DNA adducts repaired by nucleotide excision repair and HR, was additive with CNDAC. An additive cell killing was also achieved by the combination of CNDAC with taxane mitotic inhibitors (paclitaxel and docetaxel). At concentrations that allow survival of the majority of wild-type cells, the synergistic or additive combination effects were selective in HR-deficient cells. This study provides mechanistic rationales for combining CNDAC with other active drugs. Mol Cancer Ther; 15(10); 2302–13. ©2016 AACR.

Background: Sapacitabine is a novel oral nucleoside analogue with a unique ability to induce single-strand DNA breaks after incorporation into DNA, leading to production of double-strand DNA breaks and/or G2 cell cycle arrest. In AML cell lines, the active metabolite of sapacitabine, CNDAC, is synergistic with hypomethylating agents (HMAs) particularly when treated with HMAs first. In a pilot study, there were 6 CRs and 2 PRs in 25 patients treated with sapacitabine in alternating cycles with decitabine. This global randomized phase 3 study evaluated the survival benefit of this treatment strategy vs. decitabine monotherapy. Methods: Decitabine 20 mg/m2 was administered intravenously daily x 5 days of a 4-week cycle (for the control arm and odd cycles of the study arm) alternating with sapacitabine 300 mg p.o. b.i.d. x 3 days/week x 2 weeks of a 4-week cycle (even cycles of the study arm). The safety of these doses was further evaluated in the lead-in phase of the phase 3 study to confirm the findings from the pilot study. Eligible patients were ≥70 years with untreated AML and unsuitable for or unwilling to receive standard induction chemotherapy. Patients who had received HMAs for prior MDS or MPD were excluded. Results: For 482 patients randomized to receive decitabine/sapacitabine (n=241) vs. decitabine only (n=241), randomization was stratified by the presence of antecedent MDS or MPN, peripheral white blood cell count (WBC 40,000 in 59 patients (12%); 194 patients (40%) had unfavorable cytogenetic risk by SWOG criteria. Disease characteristics were well balanced in both arms. In total, 13.7% of patients achieved CR, more on the study arm vs. control (16.6% vs. 10.8%). A total of 37.3% treated patients received ≥5 cycles of treatment, similar on both arms, as were 30- and 60-day death rates. Median overall survival was 5.9 months on the study arm vs. 5.7 months on control arm, which did not reach a statistically significant difference. In the subgroup of patients with 10% patients were thrombocytopenia, anemia, neutropenia, pneumonia, febrile neutropenia, sepsis, and disease progression. Conclusion: The regimen of sapacitabine administered in alternating cycles with decitabine was active and well tolerated but it did not significantly improve overall survival as compared to decitabine monotherapy. Further analyses are being conducted to characterize the subgroups of patients who appeared to have benefited from this treatment regimen and the potential cost savings associated with the use of an oral drug. Disclosures Kantarjian: Amgen: Research Funding; Pfizer: Research Funding; Delta-Fly Pharma: Research Funding; ARIAD: Research Funding; Bristol-Meyers Squibb: Research Funding; Novartis: Research Funding. Goldberg: Novartis: Honoraria, Research Funding, Speakers Bureau; Bristol Myers Squibb: Research Funding, Speakers Bureau; Celgene: Speakers Bureau; COTA: Employment, Equity Ownership; Pfizer: Honoraria; Ariad: Speakers Bureau; Jazz: Speakers Bureau. Sekeres: Celgene: Membership on an entity's Board of Directors or advisory committees. Strickland: Boehringer Ingelheim: Consultancy; Daiichi Sankyo: Consultancy; CTI BioPharma: Consultancy; Tolero Pharmaceuticals: Consultancy; Sunesis Pharamaceuticals: Consultancy, Research Funding; Baxalta: Consultancy; Alexion Pharmaceuticals: Consultancy; Astellas Pharma: Honoraria. Rubenstein: Alexion Pharmaceuticals: Speakers Bureau. Arellano: Cephalon Oncology: Research Funding. Schiller: bluebird bio: Research Funding; mateon therapeutics: Research Funding. Gaidano: Roche: Consultancy, Honoraria; Gilead: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria; Amgen: Consultancy, Honoraria. Montesinos: Celgene Corporation: Honoraria, Research Funding. Rizzieri: Shire: Research Funding; Erytech: Research Funding. Subramanian: Boehringer-Ingelheim, Lilly, BMS, Astra-Zeneca, Pfizer, Biocept: Consultancy, Speakers Bureau. Buyse: IDDI: Employment, Equity Ownership. Chiao: Cyclacel LTD: Employment, Equity Ownership.

Sapacitabine (CS-682 or CYC682; 1-[2-C-cyano-2-deoxy-β-D-arabino-pentfuranosyl]N4-palmitoyl cytosine), a novel antitumor 2'-deoxycytidine analogue, shows a marked reduction in the water solubility because of the fatty acid side chain on the N4 group of the cytosine moiety. Poor water solubility is one of the important reasons why sapacitabine does not exert maximum antitumor activity. Therefore, we attempted to improve the water solubility of sapacitabine using a novel surfactant, Soluplus®, which consisted of a polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer. In this study, we examined whether Soluplus® increased the water solubility and an antitumor activity of sapacitabine. The cytotoxicity of Soluplus® alone was lower than that of Tween 80 and Kolliphor® D-α-tocopherylpolyethylene glycol 1000 succinate (TPGS). The water solubility and the chemosensitivity of sapacitabine against several tumor cell lines to sapacitabine markedly increased upon using Soluplus®. In addition, the potential of Soluplus® including sapacitabine in increasing the antitumor activity was compared with sapacitabine alone in vivo. Although the total dose in the experimental period was considerably lower than the effective dose of sapacitabine alone, the life span of mice treated with sapacitabine containing 40 mg/mL Soluplus® increased by 150%. If Soluplus® was used as the solubilizing agent in clinical trials of sapacitabine, a low administration dose was appeared to require, and thus side effects might be prevented.

Acute myeloid leukemia (AML) is the second most common form of leukemia and the most frequent cause of leukemia-related deaths in the United States. The incidence of AML increases with advancing age and the prognosis for patients with AML worsens substantially with increasing age. Many older patients are ineligible for intensive treatment and require other therapeutic approaches to optimize clinical outcome. To address this treatment gap, novel agents with varying mechanisms of action targeting different cellular processes are currently in development. Hypomethylating agents (azacitidine, decitabine, SGI-110), histone deacetylase inhibitors (vorinostat, pracinostat, panobinostat), FMS-like tyrosine kinase receptor-3 inhibitors (quizartinib, sorafenib, midostaurin, crenolanib), cytotoxic agents (clofarabine, sapacitabine, vosaroxin), cell cycle inhibitors (barasertib, volasertib, rigosertib) and monoclonal antibodies (gentuzumab ozogamicin, lintuzumab-Ac225) represent some of these promising new treatments. This review provides an overview of novel agents that have either completed or are currently in ongoing phase III trials in patients with previously untreated AML for whom intensive treatment is not an option. Other potential drugs in earlier stages of development will also be addressed in this review.

High-risk acute myeloid leukemia (AML) is defined by clinical and biologic features that predict for poor response to induction chemotherapy and high risk of relapse. Despite even the most aggressive and well-developed strategies for care, most patients succumb to the disease. No currently available treatment has demonstrated consistent efficacy in terms of remission induction or long-term survival. This review will highlight some of the emerging strategies to treat high-risk AML with an emphasis on clinical trials of novel strategies currently enrolling patients. Targeted molecular therapies, novel cytotoxics, and immune-based therapies are under investigation for the management of high-risk AML. Some of the agents covered include tyrosine kinase inhibitors targeted to AML specific oncoproteins, nanoparticle formulations of existing drugs, nucleoside analogs, monoclonal antibodies, chimeric antigen receptors, bispecific T-cell engaging antibodies, and vaccines. As our understanding of the biology of AML has improved, targeted therapy for AML has emerged, offering to change not only response rate, but also the nature of response. Differentiation, rather than necrosis or apoptosis, is often seen in response to targeted agents and may be seen more frequently in the future. Interventions that might be more widely used in the near future include FLT3 inhibitors and nanoparticle formulations of drugs already known to have activity in the disease. Long term immune therapy holds significant promise.

A number of new agents in acute myeloid leukemia (AML) have held much promise in recent years, but most have failed to change the therapeutic landscape. Indeed, with the exception of gemtuzumab ozogamicin (which was subsequently voluntarily withdrawn from the commercial market), no new agent has been approved for acute myeloid leukemia (AML) beyond the 7 + 3 regimen, which was has been in use for over 40 years. This review touches upon the potential reasons for these failures and explores the newer therapeutic approaches being pursued in AML.

Sapacitabine, an orally bioavailable prodrug of the deoxycytidine analog, CNDAC, is currently in a Phase III registration trial for elderly AML patients (NCT01303796). CNDAC (as DFP-10917) is in a Phase I/II trial for relapsed or refractory acute leukemia (NCT01702155) with very limited toxicity. CNDAC-induced DNA damage, double-strand breaks converted from initial single-strand breaks, is repaired mainly by the homologous recombination (HR) pathway. Deficiency in HR components (e.g. ATM, Rad51, Xrcc3, Brca1 and Brca2) confers sensitivity to CNDAC. Brca1/2 function is frequently compromised in ovarian cancer (OC). To determine the role of Brca2 in DNA damage repair after CNDAC, we used in this study a Brca2-mutant ovarian adenocarcinoma cell line, PEO1 and its revertant line, PEO1 C4-2, in which Brca2 function is restored due to a secondary mutation. First, the clonogenic sensitivities of the two lines to therapeutic agents were compared. The mutant was 6-10 fold more sensitive to CNDAC than the revertant. In contrast, Brca2 restoration did not confer resistance to cytarabine or gemcitabine, confirming the unique action mechanism of CNDAC among nucleoside analogs. Second, CNDAC-induced chromosome damage was compared in both lines. We found Brca2- mutant cells bearing more chromosomal structural abnormalities (67% metaphases with scorable breaks or fusions, N = 51) than Brca2-restored cells (14%, N = 50), apparently due to genetic instability when lacking Brca2. The mutant cells exposed to 25 nM CNDAC for 3d manifested massive chromosomal aberrations (100% metaphases unscorable, N = 51). In contrast, the revertant cells showed significantly fewer chromosome aberrations (30% scorable, N = 50). These results provided cytogenetic evidence for Brca2 involvement in DNA damage repair after CNDAC. Third, the combination effect of CNDAC with two classes of front-line anti-OC drugs, platinum compounds and taxanes, was explored using clonogenic assays and median effect analyses. Both cisplatin and oxaliplatin each had additive cell killing effects with CNDAC (combination index, CI ∼1) independent of Brca2 status. Similarly, CNDAC was additive with either paclitaxel or docetaxel in both lines (CI ∼1). Finally, two PARP inhibitors (PARPis), rucaparib and talazoparib, greatly sensitized Brca2-mutant cells. Despite the distinctive sensitivities of the two lines, both rucaparib-CNDAC and talazoparib-CNDAC combinations showed synergistic killing effect (CI Citation Format: Xiaojun Liu, Yingjun Jiang, Billie Nowak, Bethany Qiang, Nancy Cheng, William Plunkett. The DNA strand breaking nucleoside analogue sapacitabine sensitizes Brca2-deficient ovarian cancer cells and synergizes with PARP inhibitors. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4633.

2503Background: Sapacitabine is an oral nucleoside analogue; the active metabolite CNDAC generates ssDNA breaks that are converted to dsDNA breaks (DSB) during subsequent replication, resulting in cell death. CNDAC-induced DSB repair is dependent on homologous recombination (HR). Seliciclib is an oral CDK2, 7 and 9 inhibitor, and sensitizes cells to CNDAC by decreasing DSB repair via compromise of HR protein activation. This phase I study evaluates sequential and concomitant sapacitabine and seliciclib treatment. Methods: Dose escalation was conducted in patients with incurable solid tumors with sapacitabine b.i.d. x 7 consecutive days (d 1-7) followed by seliciclib b.i.d. x 3 consecutive days (d 8-10) or sapacitabine q.d. concomitantly with seliciclib q.d. x 5 days per week x 2 weeks (d 1-5, 8-12). MTD was the highest dose level at which less than one-third of at least 6 patients experienced cycle 1 DLT. Skin biopsies were obtained to assess DNA damage following sapacitabine and seliciclib treatment. Res...

Nucleoside analogs are widely used for treatment of various malignancies. Benchmark drugs are cytarabine for acute myeloid leukemia and gemcitabine for pancreatic and lung cancer. Sapacitabine is a novel cytidine analog currently in development. This editorial focuses on the potential of new nucleoside analogs and on novel possibilities of gemcitabine. Gemcitabine is a nucleoside analog with many faces, which shows a remarkable activity in a variety of cancers, most likely because it has a unique metabolism, a so-called self-potentiation. Gemcitabine is taken up by nucleoside transporters, is activated by deoxycytidine kinase and incorporated into both RNA and DNA. Inhibition of ribonucleotide reductase and dCMP deaminase enhances its activation, while cytidine deaminase converts gemcitabine to its presumably inactive metabolite 2',2'-difluorodeoxyuridine, which in its nucleotide form may inhibit thymidylate synthase. Gemcitabine is widely used in combination, predominantly with a platinum analog, with other combinations less frequently used or being explored. Standard administration of gemcitabine is with a 30-min weekly infusion at 1000 mg/m(2), but alternatives are being explored such as prodrugs (e.g., CO-1.01, which can bypass transport deficiency), the fixed-dose rate infusion (10 mg/m(2)/min), and local routes of administration by a 24-h hepatic artery infusion, by instillation in the bladder or by intraperitoneal administration to treat advanced ovarian cancer. Other alternatives for combinations of gemcitabine in ovarian cancer consist of increasing the inhibition of ribonucleotide reductase with triapine or hydroxyurea. Gemcitabine's action on signaling also provides a rational concept for combination with signal transduction pathways.