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Supplementary Figure from A Phase I Study Investigating AZD8186, a Potent and Selective Inhibitor of PI3Kβ/δ, in Patients with Advanced Solid Tumors

Purpose:To characterize safety and tolerability of the selective PI3Kβ inhibitor AZD8186, identify a recommended phase II dose (RP2D), and assess preliminary efficacy in combination with abiraterone acetate or vistusertib.Patients and Methods:This phase I open-label study included patients with advanced solid tumors, particularly prostate cancer, triple-negative breast cancer, and squamous non–small cell lung cancer. The study comprised four arms: (i) AZD8186 monotherapy dose finding; (ii) monotherapy dose expansion; (iii) AZD8186/abiraterone acetate (with prednisone); and (iv) AZD8186/vistusertib. The primary endpoints were safety, tolerability, and identification of the RP2D of AZD8186 monotherapy and in combination. Secondary endpoints included pharmacokinetics (PK), pharmacodynamics, and tumor and prostate-specific antigen (PSA) responses.Results:In total, 161 patients were enrolled. AZD8186 was well tolerated across all study arms, the most common adverse events being gastrointestinal symptoms. In the monotherapy dose-finding arm, four patients experienced dose-limiting toxicities (mainly rash). AZD8186 doses of 60-mg twice daily [BID; 5 days on, 2 days off (5:2)] and 120-mg BID (continuous and 5:2 dosing) were taken into subsequent arms. The PKs of AZD8186 were dose proportional, without interactions with abiraterone acetate or vistusertib, and target inhibition was observed in plasma and tumor tissue. Monotherapy and combination therapy showed preliminary evidence of limited antitumor activity by imaging and, in prostate cancer, PSA reduction.Conclusions:AZD8186 monotherapy had an acceptable safety and tolerability profile, and combination with abiraterone acetate/prednisone or vistusertib was also tolerated. There was preliminary evidence of antitumor activity, meriting further exploration of AZD8186 in subsequent studies in PI3Kβ pathway–dependent cancers.

Supplementary Data from A Phase I Study Investigating AZD8186, a Potent and Selective Inhibitor of PI3Kβ/δ, in Patients with Advanced Solid Tumors

Background: AcSé-ESMART is a proof-of-concept, phase I/II platform trial designed to explore targeted agents in a molecularly enriched pediatric population. WEE1 plays a role in DNA repair and cell cycle control and is overexpressed in pediatric cancers. Adavosertib combinations resulted in enhanced antitumor activity compared to single agent in neuroblastoma, rhabdomyosarcoma, medulloblastoma and high-grade glioma in vivo models. The efficacy and safety of the adavosertib-carboplatin combination has been established in adults with focus on TP53 mutated ovarian cancer. Arm C of AcSé-ESMART applied this regimen to children with advanced malignancies enriched for alterations in TP53, DNA repair/replication stress and cell cycle control. Methods: Adavosertib was administered orally, twice daily on Days 1 to 3 and carboplatin intravenously on Day 1 of a 21-day cycle. Dose finding used the continuous reassessment method starting at adavosertib 100 mg/m2/dose and carboplatin AUC 5. Pharmacokinetic (PK) and retrospective molecular bioinformatic analysis was performed. Results: Twenty patients (median age: 14.0 years, range 3.4-23.5) were included, 18 received a total of 69 cycles. Seven dose-limiting toxicities (DLTs) were observed leading to two de-escalations to adavosertib 75 mg/m2/dose and carboplatin AUC 4. All patients with DLT had thrombocytopenia grade 3/4 requiring transfusions for >7 days and/or neutropenia grade 4 for >7 days. Main overall treatment-related toxicities were hematologic and gastrointestinal. Based on the identified DLT risk, no recommended Phase 2 dose was defined. PK analysis demonstrated equivalent adavosertib exposure in children to that in adults and both doses (75 and 100 mg/m2) achieved the cell kill target. Two patients with neuroblastoma achieved partial response (PR), one with medulloblastoma unconfirmed PR, and five had stable disease (SD) >4 cycles. Patients with PR/SD >4 cycles were considered as clinical benefit (CB) for retrospective molecular analysis. There was no correlation between TP53 genomic alteration alone and response. However, 7 of 8 patients with CB but none of the 10 patients without CB had 1 to 3 genomic alterations in the DNA repair (BRCA2 mutation, 11q loss containing ATM, MRE11A, CHEK1), cell cycle control/replication stress (CCNE1 amplification, RB1 mutation/loss, SETD2 mutation/loss) and RAS pathway (KRAS mutation and amplification, NF1 loss, PTPN11 mutation) in their tumor. Conclusions: Adavosertib combined with carboplatin exhibited significant hematologic toxicity. Activity signals and identified potential molecular biomarkers suggest further combination studies with less hematotoxic DNA damaging therapy in molecularly enriched pediatric cancers. Citation Format: Susanne A. Gatz, Anne C. Harttrampf, Caroline Brard, Francisco J. Bautista, Nicolas André, Samuel Abbou, Jonathan Rubino, Windy Rondof, Marc Deloger, Marc Rübsam, Daniel Hübschmann, Lynley V. Marshall, Souad Nebchi, Isabelle Aerts, Estelle Thebaud, Emilie De Carli, Anne-Sophie Defachelles, Xavier Paoletti, Robert Godin, Kowser Miah, Peter G. Mortimer, Gilles Vassal, Birgit Geoerger. Phase I/II study of the WEE1 inhibitor adavosertib in combination with carboplatin in children with advanced malignancies: arm C of the AcSé-ESMART trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT087.

Background: AcSé-ESMART is a proof-of-concept, phase I/II, platform trial, designed to explore targeted agents in a molecularly enriched relapsed/refractory pediatric population. Arm D was evaluating the PARP inhibitor (PARPi) olaparib (ola) in combination with irinotecan (iri). In contrast to other PARPi/chemotherapy combination studies, we opted for a prolonged course of PARPi and low dose irinotecan as sensitizer. The Phase I part previously established the recommended Phase II dose (RP2D) (Gatz ASCO 2019). This is the report of the Phase II part of the trial assessing the activity in two separate expansion cohorts: cohort 1: homologous recombination repair defect (HRD) and cohort 2: Ewing sarcoma (ES). Methods: Ola was administered orally twice daily at 90 mg/m2 on Days 1 to 10 and iri intravenously at 20 mg/m2 on Days 4 to 8 of a 21-day cycle. Activity assessment followed a Minimax Simon 2-stage design. Each cohort was to progress to the second stage (additional 9 patients) if 2 or more confirmed responses were observed in the first 16 patients. Patients treated in the Phase I part at the RP2D were counting towards the respective expansion cohorts. Results: Seventy patients (median age: 14 years, range 5-23) were included in the whole study, 67 received treatment; 27 patients were treated in the dose escalation part, including 10 at the RP2D (8 in cohort 1 and 2 in cohort 2). Both cohorts passed the 1st stage and a total of 24 and 26 patients were recruited to cohort 1 and 2, respectively. Main diagnoses in cohort 1 were sarcoma (n=10), brain tumor (n=9), neuroblastoma (n=4). In cohort 1, 15 of 24 patients were considered enriched based on molecular alteration at relapse (ATM n=6; BRCA1 n=2; DNA signature 3 n=3; FANCD2, CHEK2, FANCA, ATRX all n=1); all patients in cohort 2 had presence of a ES fusion (ESWR1::FLI1 n=22; EWSR1::ERG n=4). Median number of treatment cycles were 2, range 1;51 in cohort 1 and 1;32+ in cohort 2. In cohort 1, 3 patients had a partial response (PR) (pinealoblastoma, neuroblastoma, choroid plexus carcinoma; treated with 12, 51, 25 cycles), 1 patient an unconfirmed PR (rhabdomyosarcoma, 6 cycles) and 7 patients stable disease (SD) (2 prolonged with 6 and 8 cycles). In cohort 2, 1 patient had a complete response (10 cycles) and 1 a PR (32+ cycles), 7 patients had SD (3 prolonged with 6, 10, 16 cycles). Molecular enrichment did not predict response. Retrospective correlative analysis of the molecular profiling data and tumor tissue expression analysis are ongoing to identify predictive biomarkers for PARPi combination trials and data will be presented. Conclusions: Encouraging clinical benefit was observed with the protracted ola-iri schedule in a subset of patients. Current molecular hypothesis is insufficient for patient selection and better biomarkers are needed. Citation Format: Susanne A. Gatz, Pablo Berlanga, Baptiste Archambaud, Yassine Bouchoucha, Nicolas André, Nadege Corradini, Windy Rondof, Jonathan Rubino, Souad Nebchi, Antonin Marchais, Estelle Thebaud, Alba Rubio San Simón, Natasha K. van Eijkelenburg, Lynley V. Marshall, Anne-Sophie Defachelles, Adela Canyete, Stephane Ducassou, Guy Makin, Michela Casanova, Emilie De Carli, Arnaud Petit, Gwenael Le Teuff, Xavier Paoletti, Peter G. Mortimer, Gilles Vassal, Birgit Geoerger. Phase I/II study of the PARP inhibitor olaparib in combination with irinotecan in children with advanced malignancies: arm D of the AcSé-ESMART trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT088.

Purpose: Ceralasertib is a potent and selective oral inhibitor of the serine/threonine protein kinase ataxia telangiectasia and Rad3-related (ATR) protein. Patients and Methods: Eligible patients with solid tumors, enriched for melanoma, received ceralasertib in combination with a fixed dose of paclitaxel (80 mg/m2 on D1, D8, D15) in 28-day cycles. The dose of ceralasertib was escalated to reach an MTD in a rolling 6 design. The starting dose of ceralasertib was 40 mg QD. Fifty-seven patients (33 patients with melanoma who failed prior PD1/L1 treatment) were enrolled in 7 dose cohorts ranging from 40 mg QD to 240 mg BD plus weekly paclitaxel. Results: The RP2D was established as ceralasertib 240 mg BD days 1–14 plus paclitaxel 80 mg/m2 on D1, D8, D15 every 28 days. The most common toxicities were neutropenia (n = 39, 68%), anemia (n = 25, 44%), and thrombocytopenia (n = 21, 37%). In the full analysis set of 57 patients, the overall response rate (ORR) was 22.6% (95% CI, 12.5–35.3). In 33 patients with melanoma, resistant to prior anti-PD1 therapy, the ORR was 33.3% (95% CI, 18.0–51.8). In the melanoma subset, the mPFS was 3.6 months (95% CI, 2.0–5.8), the median duration of response was 9.9 months (95% CI, 3.7–23.2), and the mOS was 7.4 months (95% CI, 5.7–11.9). Conclusions: Ceralasertib in combination with paclitaxel was well tolerated in patients with advanced malignancies and showed evidence of antitumor activity. Durable responses were observed in patients with advanced cutaneous, acral, and mucosal melanoma resistant to anti-PD1/L1 treatment. See related commentary by Ashworth, p. 4667

PURPOSE Some gastric cancers harbor MET gene amplifications that can be targeted by selective MET inhibitors to achieve tumor responses, but resistance eventually develops. Savolitinib, a selective MET inhibitor, is beneficial for treating patients with MET-driven gastric cancer. Understanding the resistance mechanisms is important for optimizing postfailure treatment options. PATIENTS AND METHODS Here, we identified the mechanisms of acquired resistance to savolitinib in 3 patients with gastric cancer and MET-amplified tumors who showed a clinical response and then cancer progression. Longitudinal circulating tumor DNA (ctDNA) is useful for monitoring resistance during treatment and progression when rebiopsy cannot be performed. RESULTS Using a next-generation sequencing 100-gene panel, we identified the target mechanisms of resistance MET D1228V/N/H and Y1230C mutations or high copy number MET gene amplifications that emerge when resistance to savolitinib develops in patients with MET-amplified gastric cancer. CONCLUSION We demonstrated the utility of ctDNA in gastric cancer and confirmed this approach using baseline tumor tissue or rebiopsy.

The VIKTORY (targeted agent eValuation In gastric cancer basket KORea) trial was designed to classify patients with metastatic gastric cancer based on clinical sequencing and focused on eight different biomarker groups (RAS aberration, TP53 mutation, PIK3CA mutation/amplification, MET amplification, MET overexpression, all negative, TSC2 deficient, or RICTOR amplification) to assign patients to one of the 10 associated clinical trials in second-line (2L) treatment. Capivasertib (AKT inhibitor), savolitinib (MET inhibitor), selumetinib (MEK inhibitor), adavosertib (WEE1 inhibitor), and vistusertib (TORC inhibitor) were tested with or without chemotherapy. Seven hundred seventy-two patients with gastric cancer were enrolled, and sequencing was successfully achieved in 715 patients (92.6%). When molecular screening was linked to seamless immediate access to parallel matched trials, 14.7% of patients received biomarker-assigned drug treatment. The biomarker-assigned treatment cohort had encouraging response rates and survival when compared with conventional 2L chemotherapy. Circulating tumor (ctDNA) analysis demonstrated good correlation between high MET copy number by ctDNA and response to savolitinib. Significance: Prospective clinical sequencing revealed that baseline heterogeneity between tumor samples from different patients affected response to biomarker-selected therapies. VIKTORY is the first and largest platform study in gastric cancer and supports both the feasibility of tumor profiling and its clinical utility. This article is highlighted in the In This Issue feature, p. 1325

Background Modulating the DNA damage response and repair (DDR) pathways is a promising strategy for boosting cancer immunotherapy. Ceralasertib (AZD6738) is an oral inhibitor of the serine/threonine protein kinase ataxia telangiectasia and Rad3-related protein, which is crucial for DDR. Patients and methods This phase II trial evaluated ceralasertib plus durvalumab for the treatment of patients with metastatic melanoma who had failed anti-programmed cell death protein 1 therapy. Results Among the 30 patients, we observed an overall response rate of 31.0% and a disease control rate of 63.3%. Responses were evident across patients with acral, mucosal, and cutaneous melanoma. The median duration of response was 8.8 months (range, 3.8-11.7 months). The median progression-free survival was 7.1 months (95% confidence interval, 3.6-10.6 months), and the median overall survival was 14.2 months (95% confidence interval, 9.3-19.1 months). Common adverse events were largely hematologic and manageable with dose interruptions and reductions. Exploratory biomarker analysis suggested that tumors with an immune-enriched microenvironment or alterations in the DDR pathway were more likely to respond to the study treatment. Conclusion We conclude that ceralasertib in combination with durvalumab has promising antitumor activity among patients with metastatic melanoma who have failed anti-programmed cell death protein 1 therapy, and constitute a population with unmet needs.

PURPOSE Poly (ADP-ribose) polymerase (PARP) inhibitors have emerged as promising therapy in cancers with homologous recombination repair deficiency. However, efficacy is limited by both intrinsic and acquired resistance. The Olaparib Combinations basket trial explored olaparib alone and in combination with other homologous recombination–directed targeted therapies. Here, we report the results of the arm in which olaparib was combined with the orally bioavailable ataxia telangiectasia and RAD3-related inhibitor ceralasertib in patients with relapsed or refractory cancers harboring DNA damage response and repair alterations, including patients with BRCA-mutated PARP inhibitor–resistant high-grade serous ovarian cancer (HGSOC). PATIENTS AND METHODS Germline and somatic mutations had to be deleterious by COSMIC or ClinVar for eligibility. Olaparib was administered at 300 mg twice daily and ceralasertib at 160 mg daily on days 1-7 in 28-day cycles until progression or unacceptable toxicities. Primary end points were confirmed complete response (CR) or partial response (PR) rates and clinical benefit rate (CBR; CR + PR + stable disease [SD] at 16 weeks). RESULTS Twenty-five patients were enrolled, with median four prior therapies. Five patients required dose reductions for myelosuppression. Overall response rate was 8.3% and CBR was 62.5% among the entire cohort. Two of five patients with tumor harboring ATM mutation achieved CR or SD ongoing at 24+ months, respectively (CBR 40%). Of seven patients with PARP inhibitor–resistant HGSOC, one achieved PR (–90%) and five had SD ranging 16-72 weeks (CBR 86%). CONCLUSION Olaparib with ceralasertib demonstrated preliminary activity in ATM-mutated tumors and in PARP inhibitor–resistant BRCA1/2–mutated HGSOC. These data warrant additional studies to further confirm activity in these settings.

International audience; Aim: Arms E and F of the AcSé-ESMART phase I/II platform trial aimed to define the recommended dose and preliminary activity of the dual mTORC1/2 inhibitor vistusertib as monotherapy and with topotecan-temozolomide in a molecularly enriched population of paediatric patients with relapsed/refractory malignancies. In addition, we evaluated genetic phosphatidylinositol 3-kinase (PI3K)/AKT/ mammalian (or mechanistic) target of rapamycin (mTOR) pathway alterations across the Molecular Profiling for Paediatric and Young Adult Cancer Treatment Stratification (MAPPYACTS) trial (NCT02613962). Experimental design and results: Four patients were treated in arm E and 10 in arm F with a median age of 14.3 years. Main diagnoses were glioma and sarcoma. Dose escalation was performed as per the continuous reassessment method, expansion in an Ensign design. The vistusertib single agent administered at 75 mg/m2 twice a day (BID) on 2 days/week and vistusertib 30 mg/m2 BID on 3 days/week combined with temozolomide 100 mg/m2/day and topotecan 0.50 mg/m2/day on the first 5 days of each 4-week cycle were safe. Treatment was well tolerated with the main toxicity being haematological. Pharmacokinetics indicates equivalent exposure in children compared with adults. Neither tumour response nor prolonged stabilisation was observed, including in the 12 patients whose tumours exhibited PI3K/AKT/mTOR pathway alterations. Advanced profiling across relapsed/refractory paediatric cancers of the MAPPYACTS cohort shows genetic alterations associated with this pathway in 28.0% of patients, with 10.5% carrying mutations in the core pathway genes. Conclusions: Vistusertib was well tolerated in paediatric patients. Study arms were terminated because of the absence of tumour responses and insufficient target engagement of vistusertib observed in adult trials. Targeting the PI3K/AKT/mTOR pathway remains a therapeutic avenue to be explored in paediatric patients. Clinical trial identifier: NCT2813135.

MET amplification is a frequently observed genomic aberration in solid tumors. We conducted a phase I trial to evaluate dose-limiting toxicity (DLT) and recommended phase II dose (RP2D) for the combination therapy. The following dose levels were tested in this single-arm phase I study: docetaxel as an intravenous infusion over 1 hour at 60 mg/m2 once every 3 weeks of a 21-day schedule plus savolitinib (level 1, 200 mg qd; level 2, 400 mg qd; level 3, 600 mg qd; level 4800 mg qd). In total, there were 17 patients enrolled on to this study [7 gastric cancer (GC) patients, 5 melanoma patients, 3 sarcoma patients, and 2 rectal cancer patients]. Most of the patients (14 of 17) were heavily pretreated (≥third line or greater lines of treatment). For the first 3 cohorts (200 mg savolitinib + docetaxel 60 mg/m2, 400 mg savolitinib + docetaxel 60 mg/m2, 600 mg savolitinib + docetaxel 60 mg/m2), there were no DLTs. In the fourth dose cohort (800 mg savolitinib + docetaxel 60 mg/m2), one DLT occurred with generalized edema grade 3 that required intensive management. One GC patient with both MET overexpression (3+) and MET amplification (MET/CEP7 ratio, 7.3) achieved a durable partial response for 297 days, and another MET-amplified GC patient (MET/CEP7 ratio, 7.6) achieved stable disease for 86 days. Due to the higher incidence of G4 neutropenia in cohort 4 (800 mg), we recommend savolitinib 600 mg qd in combination with docetaxel 60 mg/m2 as the RP2D for phase II trial. The combination therapy demonstrated a very promising antitumor activity with durable responses in MET amplified GC patients.

4045 Background: Alterations in DNA damage response (DDR) and repair are associated with genomic instability and increased somatic tumor mutational burden, and modulating DNA repair using specific inhibitors is a promising strategy to boost the efficacy of cancer immunotherapy. Ceralasertib is an oral inhibitor of the serine/threonine protein kinase Ataxia Telangiectasia and Rad3 Related (ATR), which is crucial to the cell’s response to replication stress. Methods: This phase 2 trial was designed to evaluate the efficacy and safety of ceralasertib in combination with durvalumab in patients with advanced gastric cancer (AGC). The study drug regimen was ceralasertib 240 mg BD days 15 to 28 in a 28-day cycle in combination with durvalumab at 1500 mg day 1 every 4 weeks. The primary end point was overall response rate (ORR) by RECIST (v1.1). Exploratory biomarker analysis was performed using fresh tumor biopsies in all enrolled patients. Results: 31 patients (median no. of prior lines, 2; range, 2-5) were enrolled between Jul 2019 and Mar 2020. All enrolled patients had confirmed microsatellite stable tumors, 5 patients were EBV positive, and 24 patients were PD-L1 positive (CPS≥1). Two patients had received prior anti-PD-1 treatment. At the time of data cut-off (Dec 2020), 30 patients were evaluable for response: 7 partial responses (one patient with prior anti-PD-1 treatment), 11 stable disease, and 12 disease progression were observed. The ORR was 22.6%, DCR 58.1 %, median PFS 3.0 months (95% confidence interval (CI), 2.1-3.9), median duration of response 5.7 months (95% CI, 4.9-6.5), and median OS was 6.7 months (95% CI, 3.8-9.6). A subgroup of patients (n = 11) who with loss of ATM expression and/or high proportion of mutational signature attributable to homologous repair deficiency (sig. HRD) demonstrated significantly longer PFS than those (n = 12) who had intact ATM and low sig. HRD (5.60 vs 1.65 months, hazard ratio 0.13, 95% CI 0.045-0.39, long-rank P < 0.001). The most common adverse events of any grade were fatigue (n = 22, 71.0%), nausea (n = 20, 64.5%) and anorexia (n = 19, 61.3%), and the most common adverse events of grade 3 or more were anemia and thrombocytopenia (n = 11, 35.5% each). Conclusions: Ceralasertib in combination with durvalumab demonstrated promising anti-tumor activity with durable responses in refractory AGC. Clinical trial information: NCT03780608.

3503 Background: Ataxia Telangiectasia and Rad3 Related (ATR) is an apical kinase with a critical role in the DNA-damage response. During normal DNA replication, ATR is recruited at stalled replication forks which can progress to double strand breaks if left unrepaired. AZD6738 is an oral inhibitor of the serine/threonine protein kinase ATR, a member of the phosphoinositide 3-kinase related kinase (PIKK) family. Methods: Eligible patients (pts) with advanced solid tumours were administered AZD6738 in combination with fixed dose paclitaxel 80 mg/m2 D1, D8, D15 in 28-day cycles. The dose of AZD6738 was escalated to reach a maximum tolerated dose (MTD) in a rolling 6 design. The trial evaluated safety, MTD, pharmacokinetics (PK) and pharmacodynamics (PD). Translational studies on plasma samples included cytokine analysis, panel sequencing of ctDNA, as well as IHC and immunofluorescence of immune cell markers. Results: 58 pts (34 melanoma, 15 gastric cancer (GC), 4 sarcoma, 3 colon cancer, 1 neuroendocrine and 1 hepatocellular cancer) were enrolled in 7 dose cohorts ranging 40mg OD to 240 mg BID. One dose-limiting toxicity (DLT) of neutropenic fever occurred in each cohort of n = 6 evaluable pts at AZD6738 160 mg BD and 240 mg BD days 1-14. Per protocol, the maximum tolerated dose of AZD6738 is 240 mg BID days 1-14. The most common toxicities (all causality, all grade) were: anorexia/nausea (n = 15, 26%), leukopenia (n = 11, 19%) and anemia (n = 11, 19%). 51 pts are evaluable for efficacy; we observed 1 complete response (1.9 %, melanoma), 12 confirmed partial responses (23.5%; 2 gastric, 10 melanoma all of which were post-immunotherapy), 18 stable disease (35.3%) and 20 disease progression (39.2%). The overall confirmed response rate from the dose escalation is 25.5%. Genomic analysis of baseline plasma (27 pts) revealed enrichment of NF1 somatic mutations and activating NRAS mutations amongst melanoma pts (6/18 and 4/18, respectively). Cyclical changes in interleukin-12 levels were observed in three pts with disease control which could reflect an immunological component to the mechanism of response. We will present a comprehensive case report of a patient with dramatic and durable response. Conclusions: We conclude that AZD6738 can be safely combined with weekly paclitaxel and propose a recommended phase II dose and schedule. The combination of AZD6738 and paclitaxel demonstrated promising anti-tumor activity with durable responses, especially in melanoma pts after failing anti-PD1 therapy. Clinical trial information: NCT02630199 .

Introduction: Olaparib is a PARP inhibitor (PARPi) that provides significant clinical benefit in several BRCA-mutant cancers, including ovarian, breast, pancreas and prostate. The benefit is reduced considerably in patients with multiple prior lines of therapy and olaparib resistance has no specific treatment. PARP inhibition results in replication stress (RS) due to unrepaired single strand DNA breaks (SSB) and PARP trapping in BRCA- and other HR repair-deficient tumors. ATR has critical roles in the cellular response to SSB and RS. This makes ATR inhibitors an attractive partner with olaparib, since ATR inhibition has the potential to reverse the two major mechanisms of PARP inhibitor resistance, including restored HR or stabilization of stalled replication forks. The OLAPCO trial (NCT02576444 clinicaltrials.gov) investigated. the combination of olaparib and AZD6738, an inhibitor of ATR, in relapsed, refractory cancer patients with tumors harboring HR repair mutations and in patients with BRCA-mutated PARPi pre-treated/resistant high-grade serous ovarian cancer (HGSOC). Methods: Patients with treatment-refractory, relapsed cancer were enrolled at 4 participating centers. Germline and somatic mutations had to be deleterious by COSMIC or ClinVar for eligibility. Performance status and organ function requirements were standard for early phase trials. Olaparib was given at 300 mg bid daily and AZD6738 at 160 mg daily days 1-7 in a 28-day cycle. Patients were treated until progression. Objective response was assessed by RECIST1.1 and toxicity was assessed by CTCAE4.0. Endpoints were confirmed complete [CR] or partial [PR] response rate and clinical benefit (CB) rate (response [PR] and stable disease [SD] for > 16 weeks). Results: We enrolled 24 patients; 17 (71%) females; median age 59 (36-78) years. Patients were heavily pretreated, with a median of 4 (0-10) prior regimens. Myelosuppression, especially anemia and thrombocytopenia, was the most frequent toxicity but no patient required discontinuation. Two patients required olaparib reductions for anemia. At the time of data cut-off, 20 patients are evaluable for response assessment. One of 5 patients with ATM mutations had a CR, 2 patients have CB ongoing at 12+ months. Of 7 patients with HGSOC resistant to platinum and PARP inhibitors (1-3 prior agents), 1 achieved a PR ( -90%), 3 had a best response of SD with regression < 30% (1 ongoing at 1 year) and 3 patients had progression (PD) as best response (Table 1). No other mutation or cancer type demonstrated objective response. Conclusions: The combination of olaparib and the ATR inhibitor AZD6738 demonstrated preliminary activity in patients with tumors harboring ATM mutations and in PARPi-resistant BRCA1/2-mutated HGSOC. Activity in ATM loss with an ATR inhibitor is consistent with the expected synthetic lethality of these interwoven DNA repair pathways. The encouraging data in HGSOC patients who have already progressed on a PARP inhibitor warrants additional study to further define the potential of this regimen to reverse PARPi resistance in BRCA-mutated HGSOC and other relevant solid tumors. The durability of responses in both groups (4 >1 year) is promising. Table 1MutationATMBRCA prostate pancreasBRCA Prior PARPi HGSOCCHEK2MUS81PALB2IDH and SDHD #5471142 CR1 PR0 1 SD > 4 mos213 11 PD 33112 Inevaluable110 11 Citation Format: Joseph Paul Eder, Davendra Sohal, Haider Mahdi, Khanh Do, Vicki Keedy, Navid Hafez, Deborah Doroshow, Manuel Avedissian, Peter Mortimer, Colin Glover, Patricia LoRusso, Juliane M Juergensmeier, Geoffrey I Shapiro. Olaparib and the ATR inhibitor AZD6738 in relapsed, refractory cancer patients with homologous recombination (HR) repair mutations – OLAPCO [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr A080. doi:10.1158/1535-7163.TARG-19-A080

10047 Background: AcSé-ESMART is a proof-of-concept, phase I/II, multicenter, prospective basket trial designed to explore targeting agents in a molecularly enriched cancer population; treatment arms with targeted agents as single agent or in combination regimens are explored independently. Arm D explores the PARP inhibitor olaparib (ola) in combination with irinotecan (iri). The design is based on the hypothesis that in pediatric cancer pathogenic BRCA alterations are extremely rare and proliferative capacity is high requiring a chemotherapy sensitisation approach. Preclinical data in pediatric cancer suggest PARP inhibitor activity in other genomic alterations impairing homologous recombination (HR) and demonstrate synergy with iri. We here report the results of the Phase I part of the trial. Methods: Children and adolescents with relapsed/refractory cancer and comprehensive molecular profiling (whole exome and RNA sequencing) at relapse were eligible. Dose-escalation followed a continuous reassessment method design of pre-specified dose combinations of oral ola and iv iri. Plasma for pharmacokinetics (PK) was collected. Results: From Oct 2016 to April 2018, 27 pts (19 sarcomas, 3 brain tumors, 5 other) with a median age of 15 y (range 4;22) were enrolled over 4 dose levels. Dose limiting toxicities occurred in 7 of 24 evaluable pts (gastrointestinal (n = 4), febrile neutropenia (n = 1), thrombocytopenia (n = 2)). The RP2D was defined as ola 90 mg/m2 BID day 1-10 and iri 20 mg/m2 day 4-8. Twenty-three pts evaluable for response received a median of 2 cycles (range 1-27+). Confirmed PRs were seen in one osteosarcoma, one pinealoblastoma and one neuroblastoma; time to progression was 22.4, 50 and 89+ weeks, respectively. Eight pts experienced disease stabilization (median 14.8 weeks, range 9;42.3). PK and biomarker analysis (ie. HR alterations, DNA and gene expression signatures) is ongoing to identify factors associated with clinical benefit and data will be presented. Conclusions: The RP2D of the combination is ola 90 mg/m2 BID day 1-10 and iri 20 mg/m2 day 4-8. Preliminary activity led to the ongoing Phase II part of the arm. Clinical trial information: NCT02813135.

TPS3120Background: Immune checkpoint inhibitor (ICI) containing regimens have significantly improved survival outcomes in first- and second-line non-small cell lung cancer (NSCLC). However, the maj...

4061Background: This trial was a phase II study with selumetinib (AZD6244)/docetaxel as second-line treatment for metastatic GC patients with MEK signature or RAS gene alterations as part of the GC...

4024 Background: The VIKTORY trial is a biomarker-based umbrella trial in GC. Methods: See table below. Results: From June 2014 to Jan 2017, 432 metastatic gastric cancer patients were enrolled. 124 (28.7%) were treated on one of the associated study protocols. At January 2017, 25 pts were allocated to selumetinib/paclitaxel arm, 25 to AZD1775/paclitaxel arm, 16 to AZD5363/paclitaxel arm, 16 to vistusertib/paclitaxel arm, 4 to savolitinib monotherapy, 19 to savolitinib/docetaxel arm, 19 to phase I AZD6738/paclitaxel arm. Initial efficacy signals have been seen in several arms (selumetinib/paclitaxel, 6 of 21 evaluable patients in PR). Correlative analyses between molecular signatures and treatment response are ongoing and will be presented at the meeting. For vistusertib/paclitaxel in the biomarker negative arm, we found RICTOR amplification as a promising predictive biomarker for response. Two (of three) GC patients with RICTOR amplification achieved PR to vistusertib/paclitaxel. Conclusions: This is one of the first attempts to undertake a biomarker-driven trial in metastatic GC. 28.7% of the patients were guided to one of the parallel arms based on molecular screening outcomes. We were able to identify potential molecular targets in the biomarker-negative arm, for further assessment in new protocols. Clinical trial information: 02299648. [Table: see text]