AbstractPurpose: AcSé-ESMART Arm C aimed to define the recommended dose and activity of the WEE1 inhibitor adavosertib in combination with carboplatin in children and young adults with molecularly enriched recurrent/refractory malignancies. Patients and Methods: Adavosertib was administered orally, twice every day on Days 1 to 3 and carboplatin intravenously on Day 1 of a 21-day cycle, starting at 100 mg/m2/dose and AUC 5, respectively. Patients were enriched for molecular alterations in cell cycle and/or homologous recombination (HR). Results: Twenty patients (median age: 14.0 years; range: 3.4–23.5) were included; 18 received 69 treatment cycles. Dose-limiting toxicities were prolonged grade 4 neutropenia and grade 3/4 thrombocytopenia requiring transfusions, leading to two de-escalations to adavosertib 75 mg/m2/dose and carboplatin AUC 4; no recommended phase II dose was defined. Main treatment-related toxicities were hematologic and gastrointestinal. Adavosertib exposure in children was equivalent to that in adults; both doses achieved the cell kill target. Overall response rate was 11% (95% confidence interval, 0.0–25.6) with partial responses in 2 patients with neuroblastoma. One patient with medulloblastoma experienced unconfirmed partial response and 5 patients had stable disease beyond four cycles. Seven of these eight patients with clinical benefit had alterations in HR, replication stress, and/or RAS pathway genes with or without TP53 alterations, whereas TP53 pathway alterations alone (8/10) or no relevant alterations (2/10) were present in the 10 patients without benefit. Conclusions: Adavosertib–carboplatin combination exhibited significant hematologic toxicity. Activity signals and identified potential biomarkers suggest further studies with less hematotoxic DNA-damaging therapy in molecularly enriched pediatric cancers.

e20118 Background: The treatment of relapsed or refractory small-cell lung cancer (SCLC) remains challenging due to a paucity of effective options and its rapid proliferation coupled with a high rate of genomic alterations in the DNA damage response (DDR) pathway. The SUKSES-B2 study is designed to assess the efficacy and safety of a PARP inhibitor combined with a VEGF inhibitor within a biomarker-focused umbrella framework. Methods: In this open-label, phase II, multi-cohort umbrella trial, patients received 300mg of olaparib every 12 hours and 15mg/kg of bevacizumab on day 1 of a 21-day cycle. The biomarker based inclusion criteria for SUKSES-B2 arm were as follows: (1) SLFN11 positivity, (2) POU2F3 positivity, (3) DDR pathway alterations, or (4) ATM deficiency. A total of 25 evaluable patients were targeted for recruitment, with the primary endpoint being the objective response rate (ORR). Concurrent biomarker studies were also conducted. Results: Between August 2021 and September 2023, twenty-five patients were enrolled at Samsung Medical Center, South Korea. The median age was 67 (range: 49-80), with the cohort being predominantly male (n = 24) and smokers (n = 23). The Eastern Cooperative Oncology Group Performance Status was 0 (n = 1) or 1 (n = 24) for all participants. Patients were identified to possess following biomarkers: ATM loss (n = 1), SLFN11 expression (n = 18), POU2F3 expression (n = 1), and co-expression of SLFN11 & POU2F3 (n = 5). The ORR was 12.0%, with 3 partial responses. Median progression-free survival was 1.31 months (95% CI: 1.28-5.28) and overall survival was 7.80 months (95% CI: 5.21-9.87). All responders demonstrated 3+ SLFN11 expression with ASCL1 expression. The disease control rate was 48.0%, including nine patients with stable disease, showcasing a PFS range of 2.1 to 6.8 months. Among the patients with stable disease, four patients exhibited tumor volume reductions of 4% to 17%. Drug-related adverse events (AEs) included grade 3 anemia (n = 4) and febrile neutropenia (n = 1); however, the majority of AEs were grade 1 or 2 and were managed with standard treatments. Conclusions: The combination of olaparib and bevacizumab has shown clinical benefits in a subset of patients, particularly those with SLFN11 expression, and was generally well-tolerated. The observed extended duration of response in certain patients suggests the need for further studies. Clinical trial information: NCT04939662 .

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BACKGROUND:Based on a high incidence of genomic alteration in the cell cycle and DNA damage and response (DDR)-related pathways in small cell lung cancer (SCLC), the clinical efficacy of the DDR-targeting agent olaparib (PARP inhibitor) as monotherapy and in combination with ceralasertib (ATR inhibitor) in relapsed or refractory SCLC was evaluated.METHODS:As part of a phase 2 biomarker driven umbrella study, patients with SCLC and predefined DDR gene alterations who failed to benefit from prior platinum-based regimens were allocated to the olaparib monotherapy arm and nonbiomarker-selected patients were allocated to the olaparib and ceralasertib combination arm.RESULTS:In the olaparib monotherapy arm (n = 15), the objective response rate was 6.7% (one partial response), and the disease control rate was 33.3%, including three patients with stable disease. The median progression-free survival was 1.3 months (95% CI, 1.2-NA). In the combination arm (n = 26), the objective response rate and disease control rate were 3.8% and 42.3%, respectively, with one partial response and 10 patients with stable disease. The median progression-free survival was 2.8 months (95% CI, 1.8-5.4). Treatment was generally well tolerated except for one fatal case of neutropenic fever in the combination arm.CONCLUSIONS:Targeting DDR pathways with olaparib as a single agent or in combination with ceralasertib did not meet the predefined efficacy end point. However, disease stabilization was more evident in the combination arm. Further investigation of the combination of olaparib in SCLC should be performed with diverse combinations and patient selection strategies to maximize efficacy.

8104 Background: In extensive stage small-cell lung cancer (SCLC), the standard first-line treatment is an immune checkpoint inhibitor (ICI) combined with chemotherapy. However, in the relapsed or refractory setting, the benefits of ICI-based combinations are modest, regardless of prior ICI exposure. Ceralasertib, a selective ATR inhibitor, not only enhances DNA damage, inducing apoptosis, but also affects immune and inflammatory pathways. This study assesses the safety and efficacy of combining durvalumab with ceralasertib in SCLC patients. Methods: This open-label, phase II, multi-cohort umbrella trial recruited relapsed and refractory SCLC patients independent of biomarker status. Initially, patients received 1500mg of durvalumab on day 1, followed by 240mg of ceralasertib twice daily from day 15 to 28 of a 28-day cycle (Dose A). An amendment aligned the dosing regimen to other studies to 240mg of ceralasertib twice daily from day 1 to 7, with 1500mg of durvalumab administered on day 8 (Dose B). The primary endpoint was the objective response rate (ORR), with a target enrollment of 40 evaluable patients. Results: Between June 2022 and May 2023, forty-two patients were recruited (Dose A: 27; Dose B: 15). The median age was 67 (range: 43-83), with a predominance of males (n = 36) and smokers (n = 40). ECOG PS scores were 0 (n = 1) or 1 (n = 41), and nearly half (n = 20, 47.6%) had prior ICI exposure. The ORR per RECIST was 9.5%, with a disease control rate of 26.2%, including 4 partial responses (PR) and 7 cases of stable disease (SD). Median progression-free survival (PFS) was 1.64 months (95% CI: 1.61-1.97), and overall survival was 7.16 months (95% CI: 6.07-13.9). The duration of responses was notable, showing PFS of 4.8, 17.0, and 18.3 months in ICI-naïve PR patients and 14.1 months in ICI-exposed patient currently still ongoing on treatment. A sustained clinical benefit of up to 10.7 months was observed in an ICI-naïve patient with SD. Hematologic adverse events (AEs) included thrombocytopenia as grade 4 (n = 9) and grade 3 (n = 3), anemia as grade 3 (n = 3), and neutropenia as grade 4 (n = 3) and grade 3 (n = 1). Other AEs were mostly grades 1 or 2 and manageable. Exploratory biomarker analysis is in progress and will be presented. Conclusions: Ceralasertib and durvalumab combination therapy have demonstrated durable responses in select patients with manageable hematologic toxicity. Biomarker research is ongoing to identify patients most likely to benefit from this treatment strategy. Clinical trial information: NCT04361825 .

Background Loss of PTEN function leads to increased PI3K beta signaling. AZD8186, a selective PI3K beta/delta inhibitor, has shown anti-tumor activity in PTEN-deficient preclinical models. Although the combination of AZD8186 and paclitaxel was well tolerated, limited clinical efficacy was observed in advanced gastric cancer with PTEN loss. Methods In the phase Ib dose-escalation, subjects with advanced solid tumors received oral AZD8186 (60 mg or 120 mg; twice daily (BID); 5 days on/2 days off) plus intravenous paclitaxel (70 mg/m(2) or 80 mg/m(2); days 1, 8, and 15) every 4 weeks. In the phase II part, MRGC patients with PTEN loss or PTEN/PIK3CB gene abnormality were enrolled and received recommended phase II dose (RP2D) of AZD8186 plus paclitaxel. Primary endpoints were to determine maximum tolerated dose (MTD) and RP2D in phase Ib and 4-month progression-free survival (PFS) rate in phase II. Results In phase Ib, both MTD and RP2D were determined at paclitaxel 80 mg/m(2) and AZD8186 120 mg BID. In phase II, 18 patients were enrolled [PTEN loss (n = 18) and PIK3CB mutation (n = 1)]. The 4-month PFS rate was 18.8% (3 of 16 evaluable patients) and further enrollment stopped due to futility. Conclusion Although the combination of AZD8186 and paclitaxel was well tolerated, limited clinical efficacy was observed. ClinicalTrials.gov Identifier: NCT04001569. This phase Ib/II study was conducted to determine the safety and efficacy of AZD8186 and paclitaxel combination in patients with metastatic or recurrent gastric cancer.

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.

Supplementary Figure 1. Single dose ceralasertib PK. PK from patients in cohorts 1 to 4 was in line with the PK model predictions (shadowed area) built with data from other studies. Supplementary Figure 2. ATM protein expression by IHC in patients with melanoma. Supplementary Figure 3. ctDNA clearance of mutant alleles from a responder to ceralasertib+paclitaxel; example 1. ctDNA was sequenced at baseline, day 61 and day 403. Re-staging scans were performed at day 63, day 117, intermediate days at approximate 8 week intervals (not shown) and day 426 (at the time of PD). The stream plot shows rapid clearance of the mutant alleles in line with RECIST v1.1 response. Supplementary Figure 4. CtDNA clearance of mutant alleles from a responder to ceralasertib+paclitaxel; example 2. ctDNA was sequenced at baseline, day 24, day 52 and day 241. Re-staging scans were performed at day 46, day 98, intermediate days at approximate 8 week intervals (not shown) and day 235. The stream plot shows rapid clearance of the mutant alleles prior to the day of the first re-staging scan which showed a RECIST v1.1 response.

Abstract Background: AcSé-ESMART is a European proof-of-concept, phase I/II, platform precision cancer medicine trial designed to explore targeted agents in a molecularly enriched population. Arm N explores the PARP inhibitor (PARPi) olaparib (ola) in combination with the Ataxia telangiectasia mutated rad3 related (ATR) inhibitor (ATRi) ceralasertib (cer). In pediatric cancer, the rationale for this combination is twofold: i) Many cancers show evidence of a constitutively active ATR pathway due to endogenous replication/transcription stress (RS) which can be targeted by ATRi. PARPi in this setting serves as additional replication stressor/ATRi sensitizer. ii) Classical BRCA alterations are rare and alterations conferring homologous recombination deficiency (HRD) likely require a combination approach including PARPi. This is a first-in-child study and we here report the results of the Phase I dose escalation part. Methods: Children and adolescents with relapsed or refractory cancer and advanced molecular profiling at relapse were eligible. All patients had to have molecular alterations consistent with HRD or RS in their tumor. Ola was administered orally twice daily (BID) continuously and cer orally BID on days 1-14 of a 28-day cycle. Dose level (DL) 1 was ola 150/100/50 mg BID and cer 80/40/30 mg BID in age group 12-18/6-<12/3-<6 years, respectively. Dose-escalation followed a Boin design, 12 patients treated at the recommended Phase II dose (RP2D) were required to conclude the Phase I part. Plasma for pharmacokinetics (PK) of both drugs was collected during Cycle 1. Results: Eighteen patients (8 sarcomas, 5 central nervous system tumors, 4 neuroblastomas, 1 carcinoma) with a median age of 16 years (range, 4;24) were enrolled over 3 dose levels between Feb 2021 and Sep 2022 and received a median of 3.5 cycles (range 1-12+; data cut-off Jan 2023). The combination was well tolerated overall, toxicity was mainly hematologic (thrombocytopenia, neutropenia, anemia) and gastrointestinal (nausea/vomiting). Five patients encountered dose-limiting toxicities (thrombocytopenia grade 3/4 requiring platelet transfusions > 7 days in all, and grade 4 neutropenia for > 7 days or with documented infection in 1 patient each; 0/3 DL-1, 2/12 in DL1 and 3/3 in DL2), suggesting DL1 as RP2D. One confirmed partial response (PR) was observed in a patient with pinealoblastoma (FANCA VUS), a prolonged stable disease converted to a PR after cycle 9 in a neuroblastoma (11q loss, ATRX VUS, in cycle 10). Four patients are ongoing in cycle 5/6/10/12, respectively. PK and retrospective biomarker analysis are ongoing to identify factors associated with clinical benefit and data will be presented. Conclusions: Ola and cer in combination are well tolerated. Recruitment in two expansion cohorts (HRD and RS) is ongoing at the RP2D, including confirmation of RP2D in younger children. Citation Format: Susanne A. Gatz, Alba Rubio San Simón, Baptiste Archambaud, Samuel Abbou, Morgane Cleirec, Amaury Leruste, Anne-Sophie Defachelles, Nicolas André, Jonathan Rubino, Souad Nebchi, Windy Rondof, Simon A. Smith, Peter G. Mortimer, Bienvenu Loembé, Gwenael Le Teuff, Gilles Vassal, Birgit Geoerger. Phase I/II study of the PARP inhibitor olaparib and ATR inhibitor ceralasertib in children with advanced malignancies: Arm N 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 CT019.

Background Targeting the DNA damage repair (DDR) pathways is an attractive strategy for boosting cancer immunotherapy. Ceralasertib (AZD6738) is an oral kinase inhibitor of ataxia telangiectasia and Rad3 related protein, which is a master regulator of DDR. We conducted a phase II trial of ceralasertib plus durvalumab in patients with previously treated advanced gastric cancer (AGC) to demonstrate the safety, tolerability, and clinical activity of the combination.Methods This phase II, open-label, single-center, non-randomized study was designed to evaluate the efficacy and safety of ceralasertib in combination with durvalumab in patients with AGC. The study drug regimen was ceralasertib (240 mg two times a day) days 15–28 in a 28-day cycle in combination with durvalumab (1500 mg) at day 1 every 4 weeks. The primary end point was overall response rate (ORR) by Response Evaluation Criteria in Solid Tumors (V.1.1). Exploratory biomarker analysis was performed using fresh tumor biopsies in all enrolled patients.Results Among 31 patients, the ORR, disease control rate, median progression-free survival (PFS), and overall survival were 22.6% (95% CI 9.6% to 41.1%), 58.1% (95% CI 39.1% to 75.5%), 3.0 (95% CI 2.1 to 3.9) months, and 6.7 (95% CI 3.8 to 9.6) months, respectively. Common adverse events were manageable with dose modification. A subgroup of patients with a loss of ataxia telangiectasia mutated (ATM) expression and/or high proportion of mutational signature attributable to homologous repair deficiency (sig. HRD) demonstrated a significantly longer PFS than those with intact ATM and low sig. HRD (5.60 vs 1.65 months; HR 0.13, 95% CI 0.045 to 0.39; long-rank p<0.001). During the study treatment, upregulation of the innate immune response by cytosolic DNA, activation of intratumoral lymphocytes, and expansion of circulating tumor-reactive CD8 +T cell clones were identified in responders. Enrichment of the tumor vasculature signature was associated with treatment resistance.Conclusions Ceralasertib plus durvalumab has promising antitumor activity, with durable responses in patients with refractory AGC. Thus, a biomarker-driven trial is required.Trial registration NCT03780608.

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

9514 Background: Alterations in DNA damage response (DDR) and repair are associated with genomic instability and increased somatic tumor mutational burden, and modulating DNA repair 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 metastatic melanoma (MM) who had failed to anti-PD-1 therapy. The study drug schedule was: ceralasertib at 240 mg BD on days 15 to 28 in combination with durvalumab at 1500 mg on day 1 in a 28-day cycle. The primary end point was overall response rate (ORR) by RECIST (v1.1). To investigate markers predictive of clinical outcome, fresh tumor biopsies were obtained from all enrolled patients before treatment. Results: From August 2019 to May 2020, 30 MM patients (median # of lines, 2; range, 2 - 5) were enrolled. All enrolled patients were exposed to prior anti-PD-1 treatment (immediate failure, n = 23). The ORR was 30.0% (9 PRs, 10 SDs, 10 PDs), DCR 63.3%, median PFS 7.1 months (95% confidence interval (CI), 3.6-10.6), and median OS was 14.2 months (95% CI, 9.3-19.1). Common adverse events of any grade were anemia (n = 23, 76.7%), anorexia (n = 20, 66.7%) and thrombocytopenia (n = 19, 63.3%). Common adverse events of grade 3 or more included anemia (n = 10, 33.3%). One death occurred due to febrile neutropenia in a patient with a pre-existing wound infection. Conclusions: Ceralasertib in combination with durvalumab demonstrated a promising anti-tumor activity, particularly in melanoma patients who failed to standard of care including anti-PD1 treatment. Clinical trial information: NCT03780608.

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.

risk of BP for many months (Naidoo et al.). Our experiences highlight the challenges faced in managing these patients while balancing their risk of immunosuppression and contracting COVID-19. These cases emphasize the benefits of teledermatology in this setting. For all patients, treatment was initiated remotely with patients/carers providing regular clinical images prior to telephone consultations. Dermatologists liaised closely with carers, primary care clinicians, community nurses (regularly checking blood pressure and glucose levels) and oncologists to ensure coordinated multidisciplinary care, despite the challenges imposed by the pandemic.

TPS4166 Background: Ceralasertib (AZD6738) is a selective ATR inhibitor that causes stalled replication forks to collapse, leading to accumulation of double-strand DNA breaks, which is expected to have synergistic anti-tumor effects with immune checkpoint inhibitors (ICI) or PARP inhibitors. First, accumulation of DNA damage by ceralasertib induces tumor cell death, leads to the release of tumor-specific antigen, changing the tumor microenvironment to promote antigen presentation and enhances the anti-tumor effect of ICI. Second, by simultaneously inhibiting two DNA-damage response (DDR) pathways downstream of PARP and ATR, cancer cells are unable to repair damaged DNA, leading to cell death. Ceralasertib has demonstrated promising anti-tumor activity and manageable toxicity in combination with durvalumab or olaparib in solid tumors in a phase 1 study (NCT02264678). In preclinical studies, ceralasertib has shown potent anti-tumor effects in biliary tract cancer (BTC) as a monotherapy and in combination with chemotherapy (Nam, et al, 2019). Methods: This is an open-label, phase 2 umbrella study assessing the efficacy of ceralasertib in combination with durvalumab or olaparib in patients with advanced BTC. Eligible patients have histologically confirmed BTC (including intrahepatic or extrahepatic cholangiocarcinoma, gallbladder cancer, or ampullary cancer), have failed at least one chemotherapy and have ECOG performance status of 0-1. Patients who have received prior ICI, ATR or PARP inhibitor are excluded. Each cycle consists of 4 weeks. In ceralasertib /durvalumab cohort, 37 patients will receive durvalumab 1.5g on day 1 and ceralasertib 240mg twice daily on days 15-28. In ceralasertib /olaparib cohort, 37 patients receive ceralasertib 160mg once daily on days 1-7 and olaparib 300mg twice daily on days 1-28. The primary endpoint is disease control rate, with key secondary endpoints including overall response rate, progression-free survival, overall survival, and safety. Tissue and blood samples are being collected for translational biomarker studies. Clinical trial information: NCT04298021.

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.

AbstractPurpose: 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