Representativeness of study participants

3018 Background: Ataxia telangiectasia and Rad3-related (ATR) protein kinase and poly-ADP ribose polymerases (PARPs) are crucial components in the DNA damage response (DDR). Combining tuvusertib and niraparib may synergistically enhance synthetic lethality and increase apoptosis. Part B1 of the DDRiver Solid Tumors 301 study (NCT04170153) assessed this combination. Methods: Part B1 of this open-label multicenter dose-escalation phase Ib trial enrolled unselected patients with metastatic or locally advanced unresectable solid tumors refractory to standard treatment. The primary objective was to determine safety (including maximum tolerable dose and recommended dose(s) for expansion [RDE]). Secondary and tertiary objectives included determination of the pharmacokinetics (PK), pharmacodynamics (PD), and preliminary efficacy of different dosing regimens of tuvusertib plus niraparib. Multiple continuous and intermittent schedules were explored with tuvusertib doses ranging from 90–180 mg once-daily (QD) and niraparib doses from 100–200 mg QD. A partial ordering continual reassessment method was used to identify the RDEs. Results: As of 02 January 2024, 43 patients had been enrolled (all with baseline body weight <77kg or platelet count <150,000/mm 3 ); 13 patients remained on treatment. Ten (26.3%) patients had dose-limiting toxicities (DLTs). The most common DLT was grade 3 anemia requiring blood transfusion (n=4; 10.5%); the most frequent grade ≥3 treatment-emergent adverse events were anemia (n=18; 41.9%), platelet count decrease (n=6; 14.0%) and fatigue (n=4; 9.3%). The PK of tuvusertib when combined with niraparib was consistent with that of tuvusertib monotherapy, suggesting a lack of any clinically meaningful mutual drug–drug interactions. Dose-dependent ɣ-H2AX inhibition (proximal PD marker) was observed at tuvusertib doses ≥130 mg QD. Preliminary efficacy data show 5 (15.6%) responses (3 confirmed) by RECIST v1.1 in 32 evaluable patients: 2 in patients with epithelial ovarian cancer (EOC; 1 with BRCA1-mutant [ BRCA1m] PARPi-resistant EOC, 1 with BRCA-wild type homologous recombination deficiency-positive EOC) and 1 each in patients with non-small cell lung cancer, estrogen receptor-positive HER2-negative BRCA1m breast cancer, and BRCA1m PARPi-resistant pancreatic cancer. Tuvusertib 180 mg QD and niraparib 100 mg QD or tuvusertib 90 mg QD and niraparib 200 mg QD, both given in a 1 week on/1 week off schedule, were identified as RDEs. Conclusions: The combination of tuvusertib plus niraparib, each administered on a 1 week on/1 week off schedule, has a manageable safety profile and is suitable for further investigation. A combination study in patients with PARPi-resistant EOC is planned. Clinical trial information: NCT04170153 .

Figure S1. Tuvusertib in vivo activity in ATM- and ARID1A-mutated xenograft models in mice

AbstractPurpose: Tuvusertib (M1774) is a potent, selective, orally administered ataxia telangiectasia and Rad3-related (ATR) protein kinase inhibitor. This first-in-human study (NCT04170153) evaluated safety, tolerability, maximum tolerated dose (MTD), recommended dose for expansion (RDE), pharmacokinetics (PK), pharmacodynamics (PD), and preliminary efficacy of tuvusertib monotherapy. Patients and Methods: Ascending tuvusertib doses were evaluated in 55 patients with metastatic or locally advanced unresectable solid tumors. A safety monitoring committee determined dose escalation based on PK, PD, and safety data guided by a Bayesian 2-parameter logistic regression model. Molecular responses (MR) were assessed in circulating tumor DNA samples. Results: Most common grade ≥3 treatment-emergent adverse events were anemia (36%), neutropenia, and lymphopenia (both 7%). Eleven patients experienced dose-limiting toxicities, most commonly grade 2 (n = 2) or 3 (n = 8) anemia. No persistent effects on blood immune cell populations were observed. The RDE was 180 mg tuvusertib QD (once daily), 2 weeks on/1 week off treatment, which was better tolerated than the MTD (180 mg QD continuously). Tuvusertib median time to peak plasma concentration ranged from 0.5 to 3.5 hours and mean elimination half-life from 1.2 to 5.6 hours. Exposure-related PD analysis suggested maximum target engagement at ≥130 mg tuvusertib QD. Tuvusertib induced frequent MRs in the predicted efficacious dose range; MRs were enriched in patients with radiological disease stabilization, and complete MRs were detected for mutations in ARID1A, ATRX, and DAXX. One patient with platinum- and PARP inhibitor–resistant BRCA wild-type ovarian cancer achieved an unconfirmed RECIST v1.1 partial response. Conclusions: Tuvusertib demonstrated manageable safety and exposure-related target engagement. Further clinical evaluation of tuvusertib is ongoing.

Background: Ataxia telangiectasia and Rad3-related (ATR) protein kinase plays a critical role in the DNA damage response. M1774, a potent, selective, orally administered ATR inhibitor with antitumor activity in preclinical models, was evaluated in Part A1 of an open-label, single-arm study (NCT04170153) for safety, tolerability, maximum tolerated dose, pharmacokinetics (PK) and pharmacodynamics (PD). M1774 monotherapy in patients with advanced solid tumors was well-tolerated and the totality of evidence, including quantitative model-based analyses, suggested the recommended dose for expansion (RDE) as 180 mg QD 2 weeks on/1 week off.1 Here, we report findings of the M1774 PD and immunophenotyping analyses. Methods: M1774 PD was explored by assessing phosphorylation by ATR of CHK1 (p-CHK1) in tumor and of H2AX (γ-H2AX) in serial blood samples, stimulated ex vivo with the radiomimetic 4-Nitroquinoline N-oxide or Dimethyl sulfoxide as control. A flow cytometry quantitative assay was used to measure γ-H2AX in the CD45+ lymphocytes fraction. The effect of M1774 on the immunophenotype was explored by flow cytometry. Blood samples were collected at baseline, 3 and 24 hours after first M1774 administration on day 1 of cycle 1 for the γ-H2AX analysis, and on Days 1 and 15 of Cycles 1 and 2 before treatment for immunophenotyping. Results: Preclinical tumor tissue-blood bridging PD analyses in a mouse model demonstrated that the inhibition of γ-H2AX in lymphocytes highly correlated with inhibition of p-CHK1 in tumor. Clinical data of γ-H2AX levels and immunophenotyping were generated for the blood samples collected from the 55 participants of Part A1 of the study. Exploratory PK-PD analysis using γ-H2AX levels 3 h post-dose on day 1 across the doses predicted target inhibition >80% for doses ≥130 mg, suggesting target engagement. The levels of ɣ-H2AX at 24 h after first dose intake were variable and mean levels rebounded to baseline value. M1774 treatment did not cause any significant and consistent change in the levels of all explored immune cell subsets at the tested dose levels, including myeloid-derived suppressor cells, T and B lymphocytes, monocytes, and natural killer cells. Conclusions: PD analyses showed that M1774 efficiently inhibited ATR at the RDE without impacting the immunophenotype. 1TA Yap, et al. Ann Oncol. 2022; 33(suppl_7): S197-S224. Citation Format: Ruth Plummer, Anthony W. Tolcher, Timothy A. Yap, Giuseppe Sessa, Jatinder K. Mukker, Annick Seithel-Keuth, Christine Hicking, Zoltan Szucs, Ioannis Gounaris, Giuseppe Locatelli, Johann S. de Bono. Pharmacodynamic and immunophenotyping analyses of ATR inhibitor M1774 in a Phase I study in patients with solid tumors (DDRiver Solid Tumors 301) [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 CT272.

Background: Ataxia telangiectasia and Rad3-related (ATR) protein kinase plays a critical role in the DNA damage response. M1774, a potent, selective, orally administered ATR inhibitor with antitumor activity in preclinical models, was evaluated as monotherapy in Part A1 of the first-in-human open-label, single-arm study (NCT04170153). M1774 was well-tolerated and pharmacodynamic analyses showed that maximum target engagement was reached from the dose of 130 mg QD. The totality of evidence, including quantitative model-based analyses, suggested the recommended dose for expansion (RDE) as 180 mg QD 2 weeks on/1 week off.1 One patient with platinum and PARP inhibitor-resistant BRCAwt ovarian cancer and ATRX mutation on local tumor testing achieved an unconfirmed RECIST v1.1 partial response. Retrospective analyses were conducted to explore the molecular portrait and evolution of the underlying disease of patients treated with M1774. Methods: Archival tumor biopsies, baseline and serial on-treatment circulating tumor DNA (ctDNA) samples collected from patients enrolled in the study were analyzed by next generation sequencing. Somatic putative CHIP mutations and cases with mutation variant allele frequency (VAF) < 0.3% in circulating free DNA at baseline were excluded. Molecular response (MR) was defined as at least 50% reduction of VAF. Results: Molecular data were generated from archival biopsies collected for 33/55 patients and ctDNA samples from 55/55 patients enrolled in the study. High impact mutations were detected in ARID1A (N=10), ATM (N=5), ATRX (N=3), BRCA1/2 (N=13), and other homologous recombination-related genes (N=5). MRs were observed in 11/34 (32%) patients treated with more than 130 mg QD, none were observed in the 10 patients treated with lower doses. The MRs were enriched in patients with ovarian (3/8, 38%), prostate (4/8, 50%), and breast cancer (1/3, 33%), while less frequent (3/15, 25%) in other indications. TP53 mutations were significantly associated with MR, independently of tumor type. Complete MRs were achieved for any mutations in ARID1A (2/7), ATRX (2/5), DAXX (1/3), BRCA1/2 (1/10). A complete MR was seen in a patient with ovarian cancer with prolonged stable disease by RECIST (200 days), and ARID1A mutation in ctDNA. Conclusions: M1774 induced MRs in patients treated with doses in the predicted efficacious concentration range. TP53 alterations were significantly associated with MR. Complete MRs were detected for mutations in the genes ARID1A, ATRX, DAXX that are being tested for participant selection in the ongoing biomarker expansion cohorts of the DDRiver 301 study. 1TA Yap, et al. Ann Oncol. 2022; 33(suppl_7): S197-S224. Citation Format: Anthony W. Tolcher, Timothy A. Yap, Ruth Plummer, Thomas Grombacher, Danyi Wang, Corinna Schaffroth, Christine Hicking, Zoltan Szucs, Giuseppe Locatelli, Johann S. de Bono. Translational analyses of ATR inhibitor M1774 in a Phase I study in patients with solid tumors (DDRiver Solid Tumors 301) [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 CT271.

M4076 is a potent and selective oral inhibitor of ataxia-telangiectasia mutated (ATM), a key kinase of the DNA damage response (DDR) involved in double-strand break repair. Preclinically, M4076 when combined with DNA damage-inducing therapy or other DDR inhibitors caused unrestricted cell cycle progression and DNA damage accumulation, resulting in tumor cell death. Part 1A of this ongoing open-label study (NCT04882917) evaluated the safety, tolerability, pharmacokinetics (PK), pharmacodynamics (PD), and maximum tolerated dose (MTD) of M4076 monotherapy in patients (pts) with advanced solid tumors. Dose escalation was guided by safety, along with Bayesian analysis, PK, and PD. In total, 22 pts received M4076 at 4 different dose levels (100-400 mg once daily [QD]); 21 pts (95.5%) discontinued treatment (progressive disease: 11 [50%], adverse events [AEs]: 5 [22.7%]). Dose-limiting toxicities (DLTs) were reported in 4 pts. Overall, 6 pts had ≥1 treatment-related AE (TRAE) of Grade ≥3 (including one Grade 4 hypersensitivity). The most common TRAEs were rash and anemia (Table 1). MTD was determined at 300 mg QD. As per preliminary PK across cohorts, M4076 was rapidly absorbed with median Tmax ~0.5-2 h and mean elimination half-life (t1/2) ~2-10 h; exposure increased in a dose-related manner, with minimum accumulation after multiple QD doses. At ≥200 mg QD, unbound steady state plasma concentration exceeded in vivo pCHK2 IC90 throughout the dosing interval. PD evaluation was based on the modulation of γ-H2AX (a direct ATM target) in ex vivo bleomycin stimulated CD45+ lymphocytes, by flow cytometry. Preliminary analyses showed a trend of reduction of γ-H2AX levels from day 1 to day 2, reaching 80-100% of target inhibition on day 2 with the dose range 100-400 mg QD. The MTD of M4076 was determined, and target exposure and engagement were achieved without significant hematological toxicity. Future investigations on M4076 as combination therapy are planned. Table 1. Safety overview Dose (Safety set) Patients with TRAEs (Grade ≥3) DLT analysis set (Patients with ≥80% of the planned dose or DLT per investigator) DLT DLT AE terms 100 mg(n = 2) No n = 2 No NA 200 mg(n = 7) n = 1 (decreased lymphocyte count, maculo-papular rash) n = 5 Yes(n = 1) Grade 3 maculo-papular rash (TRAE, required drug withdrawal; resolved) 300 mg(n = 9) n = 3 (anemia, spontaneous bacterial peritonitis) n = 7 Yes(n = 1) Grade 1 maculo-papular rash; Grade 2 fever (TRAEs, required treatment discontinuation; resolved) 400 mg(n = 4) n = 2 (nausea, maculo-papular rash, hypersensitivity) n = 4 Yes(n = 2) Grade 3 maculo-papular rash (TRAEs, required dose reduction/interruption and/or concomitant medication; resolved) MedDRA version 23.0, NCI-CTCAE version 5.0. Data cutoff: 2 Nov 2022 AE, adverse event; DLT, dose-limiting toxicity; NA, not applicable; TRAE, treatment-related AE Citation Format: Lillian L. Siu, Timothy A. Yap, Sofia Genta, Gregory Pennock, Christine Hicking, Xiaoli You, Jatinder K. Mukker, Giuseppe Locatelli, Anthony W. Tolcher. A first-in-human phase I study of the ATM inhibitor M4076 in patients with advanced solid tumors (DDRiver Solid Tumors 410): Part 1A results [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 CT171.

Ataxia telangiectasia and Rad3-related (ATR) protein kinase plays a critical role in the DNA damage response. M1774, a potent, selective, orally administered ATR inhibitor, exerts antitumour activity in preclinical models.

Background: In the CLARITY (CLAdRIbine Tablets treating multiple sclerosis orallY) study, Cladribine Tablets significantly improved clinical and magnetic resonance imaging (MRI) outcomes (vs placebo) in patients with relapsing-remitting multiple sclerosis. Objective: Describe two clinically relevant definitions for patients with high disease activity (HDA) at baseline of the CLARITY study (utility verified in patients receiving placebo) and assess the treatment effects of Cladribine Tablets 3.5 mg/kg compared with the overall study population. Methods: Outcomes of patients randomised to Cladribine Tablets 3.5 mg/kg or placebo were analysed for subgroups using HDA definitions based on high relapse activity (HRA; patients with ⩾2 relapses during the year prior to study entry, whether on DMD treatment or not) or HRA plus disease activity on treatment (HRA + DAT; patients with ⩾2 relapses during the year prior to study entry, whether on DMD treatment or not, PLUS patients with ⩾1 relapse during the year prior to study entry while on therapy with other DMDs and ⩾1 T1 Gd+ or ⩾9 T2 lesions). Results: In the overall population, Cladribine Tablets 3.5 mg/kg reduced the risk of 6-month-confirmed Expanded Disability Status Scale (EDSS) worsening by 47% vs placebo. A risk reduction of 82% vs placebo was seen in both the HRA and HRA + DAT subgroups (vs 19% for non-HRA and 18% for non-HRA + DAT), indicating greater responsiveness to Cladribine Tablets 3.5 mg/kg in patients with HDA. There were consistent results for other efficacy endpoints. The safety profile in HDA patients was consistent with the overall CLARITY population. Conclusion: Patients with HDA showed clinical and MRI responses to Cladribine Tablets 3.5 mg/kg that were generally better than, or at least comparable with, the outcomes seen in the overall CLARITY population.

BACKGROUND:Immune reconstitution therapies (IRT) for patients with multiple sclerosis are used for short, intermittent treatment periods to induce immune resetting and allow subsequent treatment-free periods. Cladribine tablets are postulated to be an IRT that causes selective and transient reductions in CD19+ B cells and T cells, followed by reconstitution of adaptive immune function. OBJECTIVE:To characterize long-term lymphocyte count changes in pooled data from the 2-year CLARITY and subsequent 2-year CLARITY Extension studies, and the PREMIERE registry (Long-term CLARITY cohort). METHODS:Data from patients randomized to placebo (n = 435) or cladribine tablets 10 mg (MAVENCLAD®; 3.5 mg/kg cumulative dose over 2 years, referred to as cladribine tablets 3.5 mg/kg; n = 685) in CLARITY or CLARITY Extension, including time spent in the PREMIERE registry were pooled to provide long-term follow-up data. The study investigated absolute lymphocyte counts (ALC) up to 312 weeks and B and T cell subsets up to 240 weeks after the first dose, in patients receiving placebo or cladribine tablets 3.5 mg/kg administered as two short (4 or 5 days) weekly treatments at the start of months 1 and 2 in each treatment year, followed by no further active treatment. RESULTS:Treatment with cladribine tablets 3.5 mg/kg resulted in selective reductions in B and T lymphocytes. Lymphocyte recovery began soon after treatment in each of years 1 and 2. Median ALC recovered to the normal range and CD19+ B cells recovered to threshold values by week 84, approximately 30 weeks after the last dose of cladribine tablets in year 2. Median CD4+ T cell counts recovered to threshold values by week 96 (approximately 43 weeks after the last dose of cladribine tablets in year 2). Median CD8+ cell counts never dropped below the threshold value. CONCLUSION:These results show the dynamics of lymphocyte count changes following treatment with cladribine tablets 3.5 mg/kg. The immune cell repopulation results provide further evidence that cladribine tablets may represent a form of IRT.

Cladribine Tablets (MAVENCLAD®) selectively reduce absolute lymphocyte counts (ALCs) in patients with multiple sclerosis. The recommended cumulative dose of Cladribine Tablets is 3.5 mg/kg over 4–5 days in months 1 and 2 of treatment years 1 and 2, followed by prolonged efficacy with no additional treatment. After the cladribine-induced reduction, ALCs recover to normal within each treatment year in most patients. Those patients with slow ALC recovery can develop Grade 3–4 lymphopenia, especially those patients with Grade ≥  2 lymphopenia at the start of year 2. Guidelines allowing treatment postponements during year 2 have been proposed for patients with a low ALC, subsequent to CLARITY, the pivotal clinical trial.

9569 Background: Avelumab, an FDA-approved human anti–PD-L1 IgG1 monoclonal antibody for patients (pts) with metastatic Merkel cell carcinoma, showed an objective response rate (ORR; by RECIST v1.1) of 31.8% in a second-line phase 2 trial (NCT02155647). We assessed the association of tumor mutational burden (TMB; nonsynonymous somatic variants/megabase), PD-L1 expression, Merkel cell polyomavirus (MCPyV) status, and CD8+ tumor-infiltrating T-cell density with ORR and survival. Molecular profiles (RNAseq and WEX) also were analyzed. Methods: Baseline tumors (n = 36) were profiled using RNAseq and WEX sequencing. PD-L1 expression (≥1% cutoff), MCPyV status, and CD8+ T-cell density at the tumor invasive margin were evaluated by IHC. MHC locus expression was measured with OptiType and loss of heterozygosity (LOH) with LOHHLA. Results: Of 36 pts profiled, 12 had a response, 27 were PD-L1+, and 23 were MCPyV+. The TMB upper tertile and quartile values were 1.34 and 3.16, respectively. Consistent with literature, MCPyV− pts had a higher median TMB (2.72) than MCPyV+ pts (0.49). PD-L1+ tumors trended toward a higher TMB. An empirical cohort-specific TMB cutoff of ≥2 was chosen to include sufficient pts per subgroup. Pts with TMB ≥2 vs TMB < 2 had higher ORR (5 of 11 [45.5%] vs 7 of 25 [28.0%]) and 6-mo PFS rates (60% vs 38%). Among pts with TMB ≥2, the highest ORRs were reported in MCPyV− (4 of 7 pts), PD-L1+ (5 of 9 pts), and CD8+ T-cell density higher than median (5 of 6 pts) subgroups. MHC expression trended with ORR and survival. Higher mean MHC expression was found in pts with CD8+ T-cell density higher than median (p < 0.05). Mutations in antigen presentation genes were detected: LOH at the HLA locus in 9 of 30 pts (28%), including 4 with a response; an NK cell activation signature was also associated with response. These data may suggest that ADCC contributes to response. Factorial analysis of gene signature scores identified signatures (eg, IFNγ, TP53 pathway) associated with MCPyV status and response. Conclusions: Responses in this data set were not attributed to any specific biomarker alone. Future analysis is focused on validating these results and identifying rational drug combinations with avelumab. Clinical trial information: NCT02155647.

9507 Background: Merkel cell carcinoma (MCC) is a rare, aggressive skin cancer with poor prognosis. Studies of second-line chemotherapy for metastatic MCC (mMCC) have reported median progression-free survival (PFS) of up to 3 months and no benefit to overall survival (OS). Avelumab, a human anti–PD-L1 monoclonal antibody, is approved in several countries for the treatment of mMCC. Here, we report updated efficacy and safety data from part A of the pivotal, single-arm, phase 2, JAVELIN Merkel 200 trial of avelumab in patients (pts) with mMCC and ≥2 y of follow-up. Methods: Pts with mMCC and progression on prior chemotherapy received avelumab 10 mg/kg intravenously every 2 weeks until disease progression or intolerable adverse event (AE). Objective response rate (ORR), duration of response (DOR), and PFS were evaluated by independent review per RECIST v1.1; OS and AEs (per NCI CTCAE v4.0) were also evaluated. Results: As of Sep 26, 2017, 88 pts were followed for a median of 29.2 mo (range 24.8-38.1). The median duration of treatment was 3.9 mo (range 0.5-36.3); treatment was ongoing in 9 pts (10.2%). The confirmed ORR of 33.0% (95% CI 23.3-43.8; complete response in 11.4%) remained unchanged from previous analyses at 1 y and 18 mo; responses were ongoing in 19 of 29 pts, including 12 pts with > 2 y response duration. Median DOR had not been reached (range 2.8-31.8 mo; 95% CI 18.0-not estimable). Durable responses led to stable rates of PFS (29% at 1 y, 29% at 18 mo, and 26% at 2 y). Median OS was 12.6 mo (95% CI 7.5-17.1) and the 2-y OS rate was 36% (50% at 1 y and 39% at 18 mo). Clinical activity was observed across all pt subgroups, irrespective of tumor PD-L1 and MCPyV status. The AE profile remained consistent with previous analyses: 67 pts (76.1%) had a treatment-related AE (TRAE), 10 pts (11.4%) had a grade ≥3 TRAE, 20 pts (22.7%) had an immune-related AE, and no treatment-related deaths occurred. Conclusions: At ≥2 y of follow-up, avelumab shows continued durable responses and meaningful survival outcomes in pts with mMCC, exceeding the outcomes associated with cytotoxic chemotherapy. Efficacy and safety results confirm the lasting clinical benefit of avelumab in pts with mMCC. Clinical trial information: NCT02155647.

Background: An independent meta-analysis determined that malignancy risk was not increased with cladribine tablets (CT) compared with other DMDs in patients with RMS. An unusually low rate was observed in the placebo (PBO) group.1 lymphocyte reductions occur following annual courses of CT, but are transient relative to the sustained clinical efficacy characteristic of selective immune reconstitution therapy. Data from additional trials/registry with CT3.5 mg/kg (CT3.5) (up to 8 years of follow up) are now available. The objective was assessment of malignancy risk with CT3.5 monotherapy and PBO 3 phase III trials and the premiere registry, and comparison with a global malignancy database.