Primary Endpoint Of Progression-free Survival Research Articles

Abstract PO4-27-06: Design of Active Phase 3 ENABLAR-2 Study Evaluating Enobosarm +/- Abemaciclib in Patients with AR+ER+HER2- 2nd-Line Metastatic Breast Cancer Following Tumor Progression on an Estrogen Blocking Agent Plus Palbociclib or Ribociclib

Abstract Background: Targeting the androgen receptor (AR) with an oral selective agonist, enobosarm, is a novel approach to overcome ER and CDK4/6 resistance to suppress metastatic breast cancer (mBC). Preclinical studies in CDK4/6 inhibitor and estrogen blocking agent resistant PDX mBC models demonstrated that enobosarm alone or in combination with another CDK 4/6 inhibitor suppressed PDX mBC growth. In a subgroup analysis from a Phase 2 study, enobosarm demonstrated efficacy in the treatment of AR+ ER+ HER2- metastatic breast cancer in patients who had tumor progression on estrogen blocking agent and a CDK 4/6 inhibitor with a best overall response rate of 30% (2CRs and 1 PR). A Phase 3 ENABLAR-2 multi-center, open label, study evaluating enobosarm +/- abemaciclib is open and active for the treatment of HR+HER2- mBC. Methods: The two-staged Phase 3 ENABLAR-2, open-label, randomized, multicenter study is being conducted in AR+ER+ HER2- 2nd-line mBC who have progressed on estrogen blocking agent plus palbociclib or ribociclib. In the Stage 1 of the study (160 patients), five treatment arms will be assessed with the primary efficacy endpoint of ORR: enobosarm 9 mg QD, enobosarm 1 mg QD + abemaciclib, enobosarm 3 mg QD + abemaciclib, enobosarm 9 mg QD + abemaciclib, and an estrogen blocking agent, active control (a nonsteroidal AI, exemestane +/- everolimus, or SERD). Secondary efficacy endpoints include progression-free survival (PFS). In Stage 2 of the study, patients will be randomized to receive enobosarm +/- abemaciclib (based on outcome of ORR in Stage 1) or estrogen blocking agent, active control, with the primary endpoint of PFS and secondary efficacy endpoints including, ORR, CBR, OS, as well as changes in quality-of-life measurements (SPPB, EORTC-QLQ, body composition measured by DEXA). Randomization will be stratified by AR% nuclei staining and by line of treatment for metastatic disease. Subjects will receive study drug until disease progression is observed. Preliminary Results: To date, 3 patients have been treated with enobosarm 9 mg in combination with abemaciclib. The combination therapy was well tolerated with no new safety findings. There were no drug-drug interactions between enobosarm and abemaciclib. Two patients have achieved BOR of a partial response with up to 79% and 56% reduction in their target lesion recorded by local reads on day 224 post-treatment initiation (PTI). The third patient has achieved a stable disease and continues to receive treatment (on study 10+ months). Conclusions: Preliminary data of efficacy and safety of enobosarm in combination with abemaciclib are encouraging. The Phase 3 ENABLAR-2 study is underway to further evaluate enobosarm monotherapy or in abemaciclib combination therapy in 2nd-line metastatic breast cancer population. Clinical trial information: NCT05065411. Research Sponsor: Veru Inc Citation Format: Kristine Rinn, Hannah Linden, Lee Schwartzberg, Gary Barnette, Domingo Rodriguez, Itay Shalev, Mitchell Steiner, Adam Brufsky, Joyce O'Shaughnessy. Design of Active Phase 3 ENABLAR-2 Study Evaluating Enobosarm +/- Abemaciclib in Patients with AR+ER+HER2- 2nd-Line Metastatic Breast Cancer Following Tumor Progression on an Estrogen Blocking Agent Plus Palbociclib or Ribociclib [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-27-06.

Abstract PO3-18-09: OPERA-01: A randomized, open-label, phase 3, study of palazestrant (OP-1250) vs standard-of-care treatment for ER+, HER2- advanced or metastatic breast cancer after endocrine and CDK4/6 inhibitor therapy

Abstract Background: In estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer (MBC), adding a cyclin-dependent kinase 4/6 (CDK4/6) inhibitor to endocrine therapy (ET) has improved outcomes and is the current standard-of-care treatment in the first-line setting. However, resistance to first-line treatment develops in most patients (pts), which is often attributed to acquired mutations in ESR1. Limited data exist for ET-based treatment options after progression on prior ET and CDK4/6 inhibitors, and most pts will transition to chemotherapy for further treatment. Therefore, there is a significant unmet need for more effective ET in pts with ER-positive, HER2-negative MBC to improve outcomes and delay time to chemotherapy. Palazestrant (OP-1250) is a small molecule oral complete ER antagonist (CERAN) and selective ER degrader (SERD) that binds the ligand binding domain of ER and completely blocks ER-driven transcriptional activity in both wild-type (ESR1-wt) and mutant (ESR1-mut) forms of ER. In preclinical studies, palazestrant demonstrated better tumor shrinkage in ESR1-wt and ESR1-mut models when compared to fulvestrant; it also showed efficacy in brain metastasis models. In a phase 1/2 monotherapy study in pts with heavily pretreated ER-positive, HER2-negative advanced breast cancer (BC) or MBC (NCT04505826), palazestrant showed a tolerable safety profile, promising antitumor efficacy, and favorable pharmacokinetics (PK) supporting once a day (qd) dosing. The recommended Phase 2 dose of palazestrant is 120 mg qd. Methods: The OPERA-01 trial is an international, multicenter, randomized, open-label, phase 3 clinical trial comparing the efficacy and safety of palazestrant as a single agent to standard-of-care ET (fulvestrant, anastrozole, letrozole, or exemestane) in pts with ER-positive, HER2-negative advanced BC or MBC that has relapsed or progressed on 1 or 2 prior lines of ET for MBC, which includes a CDK4/6 inhibitor. Eligible pts are women (pre- or post-menopausal) or men who have a confirmed diagnosis of ER-positive, HER2-negative locally advanced evaluable BC or MBC not amenable to curative therapy. ER and HER2 status are determined according to the American Society of Clinical Oncology/College of American Pathologists guidelines. Patients must have Eastern Cooperative Oncology Group performance status 0 or 1. Prior treatments must include 1 or 2 prior lines of ET as monotherapy or in combination with a CDK4/6 inhibitor for MBC; must have received CDK4/6 inhibitor in combination with ET and have disease progression during or within 28 days of completion of each line of prior treatment for MBC; most recent ET given for ≥6 months. Prior chemotherapy in the metastatic setting is not permitted. Patients (N∼500) are randomized to palazestrant or standard-of-care ET monotherapy, and are stratified by ESR1 mutation status, prior lines of ET for advanced disease (1 vs 2 lines), and presence or absence of visceral disease. The primary endpoint of progression-free survival will be assessed by blinded independent central review in pts with and without ESR1 mutations in the intent-to-treat population. Secondary endpoints include overall survival, antitumor activity (objective response rate, clinical benefit rate, and duration of response), safety, patient-reported outcomes, and PK in pts with and without ESR1 mutations. The study is planned to be conducted globally. Citation Format: Arlene Chan, Jane Meisel, Komal Jhaveri, Joo Hyuk Sohn, Meritxell Bellet- Ezquerra, Jason Schroeder, Mark Shilkrut, Barbara Pistilli. OPERA-01: A randomized, open-label, phase 3, study of palazestrant (OP-1250) vs standard-of-care treatment for ER+, HER2- advanced or metastatic breast cancer after endocrine and CDK4/6 inhibitor therapy [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-18-09.

Abstract PO2-04-07: Efficacy and Safety of First-line Therapy in Patients with HER-2 positive Advanced Breast Cancer:A network Meta-analysis of Randomized Controlled Trials

Abstract Background: The numerous but conflicting first-line treatment regimens for Her-2 positive advanced breast cancer necessitate a comprehensive evaluation to inform clinical decision-making. In this study, we conducted a Bayesian network meta-analysis (NMA) to compare the efficacy and safety of different interventions. Methods: We systematically searched for relevant randomized controlled trials (RCTs) in Pubmed, Embase, Cochrane Library and online abstracts published by ASCO, SABCS. NMA was performed using R software, STATA and Review Manager 5.4 to calculate and analyze the primary endpoint progression free survival (PFS), as well as the secondary endpoints of overall survival (OS), objective response rate (ORR) and adverse events (AE) higher than grade 3. Results: Out of the 8,603 manuscripts retrieved, we included 30 RCTs involving 12,045 patients in our analysis. Regarding PFS, the combination of trastuzumab with TKI was more favorable than dual-target therapy (hazard ratio=0.54, 95% [CI]: 0.40–0.72), and combination chemotherapy was superior to monotherapy (HR=0.66, 0.53-0.83). It is important to note that the addition of anthracycline did not result in improved PFS (HR=1.27, 0.87-1.86). For the HR+HER2+ population, dual-target plus endocrine therapy was more effective than single-target plus endocrine therapy (HR=0.65, 0.53-0.80). Monotherapy combined with dual-target therapy significantly improved OS and ORR compared to monotherapy with single-target therapy (HR=0.69, 0.56-0.84; OR=1.89, 1.34-2.65). A comprehensive analysis of both PFS and AE higher than grade 3 indicated that monotherapy plus dual-target therapy struck a balanced approach between effectiveness and toxicity compared to other regimens. Conclusions: Monotherapy plus dual-target therapy remains the optimal choice among all first-line treatment options for advanced breast cancer. The combination of trastuzumab with TKI demonstrated a significant improvement in PFS, but further data are warranted to confirm the survival benefit. Figure 1. Network diagrams of PFS, OS, ORR and adverse events higher than grade 3 in eligible experimental arms. Figure 2. Forest plot of PFS, OS, ORR and adverse events higher than grade 3 in eligible experimental arms. (A): PFS of HER2+ for experimental arms. (B): PFS of HR+ and HER2+ for experimental arms. (C): OS of HER2+ for experimental arms. (D): ORR of HER2+ for experimental arms. (E): Adverse events higher than grade 3 of HER2+ for experimental arms. Figure 3. Each endpoint ranking for experimental arms. (SUCRA, surface under the cumulative ranking) (A): PFS ranking for experimental arms. (B): OS ranking for experimental arms. (C): ORR ranking for experimental arms. (D): Adverse events higher than grade 3 ranking for experimental arms. (E): Experimental arms ordered by their overall probability as the best treatment in terms of both efficacy and safety Citation Format: Junxiao Wang, Yushuai Yu, Jie Zhang, Chuangui Song. Efficacy and Safety of First-line Therapy in Patients with HER-2 positive Advanced Breast Cancer:A network Meta-analysis of Randomized Controlled Trials [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-04-07.

Abstract GS02-01: Randomized phase 3 study of datopotamab deruxtecan vs chemotherapy for patients with previously-treated inoperable or metastatic hormone receptor-positive, HER2-negative breast cancer: Results from TROPION-Breast01

Abstract Background: The global, phase 3 TROPION-Breast01 trial (NCT05104866) assessed the TROP2-directed antibody-drug conjugate (ADC) datopotamab deruxtecan (Dato-DXd) compared with investigator’s choice of chemotherapy (ICC) in patients (pts) with inoperable or metastatic hormone receptor-positive, HER2-negative (HR+/HER2‒) breast cancer (BC). Primary results were presented at ESMO 2023 (Bardia A, et al. Abstract LBA11). Here we report expanded data from TROPION-Breast01. Methods: Pts aged ≥18 years who had inoperable or metastatic HR+/HER2‒ BC, had disease progression on endocrine therapy (ET) and for whom ET was unsuitable, and had received 1‒2 prior lines of systemic chemotherapy (CT), were eligible. Pts were randomized 1:1 to Dato-DXd (6 mg/kg Q3W) or ICC (eribulin, vinorelbine, capecitabine, or gemcitabine) until progression or unacceptable toxicity. The dual primary endpoints were progression-free survival (PFS) by blinded independent central review (BICR) per RECIST 1.1, and overall survival (OS). Results: In total, 732 pts were randomized: 365 to the Dato-DXd arm and 367 to ICC. At data cut-off (Jul 17, 2023), 93/39 pts in the Dato-DXd/ICC groups were ongoing treatment. Pts receiving Dato-DXd had significantly improved PFS vs ICC (HR 0.63 [95% CI 0.52‒0.76]; p<0.0001). Hazard ratios for PFS favored Dato-DXd over ICC across prespecified pt subgroups, including prior lines of CT in the metastatic setting (1 vs 2), prior use of CDK4/6 inhibitor (≤12 months vs >12 months), prior use of endocrine therapy in the metastatic setting ( <6 months vs ≥6 months) and brain metastases (yes vs no). OS data were not mature at this data cut-off. In the Dato-DXd vs ICC arms, 192 (53%) vs 247 (67%) pts had received a subsequent therapy after study treatment discontinuation, including 15 (4%) vs 52 (14%) who received subsequent ADC therapy, and 165 (45%) vs 186 (51%) who received subsequent CT. Median time to first subsequent therapy was 8.2 months in the Dato-DXd arm vs 5.0 months in the ICC arm (HR 0.53 [95% CI 0.45–0.64). Overall, rate of grade ≥3 treatment-related adverse events (TRAEs) with Dato-DXd was less than half that with ICC. The secondary patient-reported outcome endpoints showed that time to deterioration in physical functioning, pain, and global health status/quality of life were delayed in the Dato-DXd arm compared with ICC. Conclusions: TROPION-Breast01 met its dual primary endpoint of PFS, demonstrating statistically significant and clinically meaningful improvement in PFS with Dato-DXd compared with ICC across all subgroups. Overall, the safety profile and QoL with Dato-DXd was favorable compared with ICC. These data support Dato-DXd as a potential new therapeutic option for pts with inoperable or metastatic HR+/HER2‒ BC who have received 1‒2 prior lines of CT. Citation Format: Aditya Bardia, Komal Jhaveri, Seock-Ah Im, Michelino De Laurentiis, Binghe Xu, Sonia Pernas, Giuliano Borges, David Cescon, Masaya Hattori, Yen-Shen Lu, Noelia Martínez-Jáñez, Erika Hamilton, Shusen Wang, Junji Tsurutani, Kevin Kalinsky, Lu Xu, Sabrina Khan, Neelima Denduluri, Hope Rugo, Barbara Pistilli. Randomized phase 3 study of datopotamab deruxtecan vs chemotherapy for patients with previously-treated inoperable or metastatic hormone receptor-positive, HER2-negative breast cancer: Results from TROPION-Breast01 [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr GS02-01.

Modified FOLFOX6 plus bevacizumab with and without nivolumab for first-line treatment of metastatic colorectal cancer: phase 2 results from the CheckMate 9X8 randomized clinical trial

BackgroundStandard first-line therapies for metastatic colorectal cancer (mCRC) include fluoropyrimidine-containing regimens with oxaliplatin and/or irinotecan and a biologic agent. Immunotherapy may enhance antitumor activity in combination with standard therapies in...

Overall survival and long-term safety with ripretinib vs sunitinib in patients with advanced gastrointestinal stromal tumor previously treated with imatinib: Final analyses from INTRIGUE.

748 Background: Ripretinib is a switch-control tyrosine kinase inhibitor approved for patients (pts) with gastrointestinal stromal tumor (GIST) who received prior treatment with 3 or more kinase inhibitors, including imatinib. Sunitinib is approved for advanced GIST after imatinib failure. In the second interim analysis of overall survival (OS) from the phase 3 INTRIGUE study, the OS event rate was 41% in the all-patient (AP) intent-to-treat (ITT) population, and OS was similar between treatment arms in both the KIT exon 11 ITT and AP ITT populations. Here, we present the final OS and updated safety from INTRIGUE. Methods: INTRIGUE (NCT03673501) is an open-label, phase 3 study of adults with advanced GIST who had disease progression on or intolerance to imatinib. Randomization was 1:1 to ripretinib 150 mg once daily (QD) or sunitinib 50 mg QD (4 weeks on/2 weeks off) and was stratified by KIT mutational status and imatinib intolerance. OS was a key secondary endpoint (the primary endpoint of progression-free survival was reported previously); final OS analysis was prespecified to occur with ≥200 and ≥145 events in the AP ITT and KIT exon 11 ITT populations, respectively. Data cutoff was March 15, 2023. Results: Of 453 pts, 444 received treatment; 40 remain on treatment (ripretinib, 28/223 [13%]; sunitinib, 12/221 [5%]). Treatment discontinuation was due to progressive disease (PD) by independent radiologic review (56%), PD by investigator (11%), clinical PD (6%), withdrawal of consent (6%), and adverse events (AEs; 5%). Fewer pts discontinued treatment due to AEs with ripretinib vs sunitinib (3% vs 6%). There were 211 OS events (47%) in the AP ITT population and 151 OS events (46%) in the KIT exon 11 ITT population. OS was similar with ripretinib vs sunitinib in the 2 ITT populations (Table). Fewer pts had grade 3/4 treatment-emergent AEs with ripretinib vs sunitinib (43% vs 67%). Dose interruptions and reductions were lower with ripretinib vs sunitinib. Median treatment duration for ripretinib vs sunitinib was 7.9 vs 6.5 months. Conclusions: In the finalOS analysis from the INTRIGUE study, OS was similar between treatment arms. The safety profile remained consistent and more favorable for ripretinib vs sunitinib in pts with advanced GIST previously treated with imatinib. Clinical trial information: NCT03673501 . [Table: see text]

Addition of metastasis-directed therapy to standard-of-care systemic therapy for oligometastatic pancreatic ductal adenocarcinoma (EXTEND): Results of a multicenter, randomized phase II trial.

603 Background: Standard treatment of oligometastatic pancreatic ductal adenocarcinoma (PDAC) consists of multi-agent chemotherapy, although outcomes remain poor. We tested the hypothesis that the addition of comprehensive metastasis-directed therapy (MDT) to standard-of-care systemic therapy would improve progression-free survival (PFS) compared with systemic therapy alone. Methods: The External Beam Radiation to Eliminate Nominal Metastatic Disease (EXTEND) trial is a multicenter phase II basket trial randomizing patients with ≤ 5 solid tumor metastases 1:1 to MDT plus systemic therapy versus systemic therapy alone. Each histology-specific basket was pre-specified and independently powered for the primary endpoint of PFS; here we present results of the pancreatic cancer basket. Progression was defined by radiographic criteria (RECIST v1.1), clinical events, or death. Patients were stratified at randomization by number of metastases (1-2 vs 3-5), number of prior lines of systemic therapy (0-1 vs 2+), and cancer antigen 19-9 (CA-19-9) level (<90U/ml vs ≥90U/ml). Exploratory endpoints included systemic immune response measures. The cutoff date for the primary analysis was September 1, 2023. ClinicalTrials.gov registration: NCT03599765. Results: Between March 2019 and February 2023, 41 patients with oligometastatic PDAC were randomized and 40 were eligible for PFS analysis (MDT arm: 19 patients; control arm: 21 patients). Baseline characteristics were well-balanced between arms. Thirty-one patients experienced progression or death; median follow-up time for censored patients was 9.9 months. The MDT arm had significantly longer PFS compared to the systemic therapy arm (median PFS 10.3 versus 2.5 months; log-rank p=0.006). After stratification, the estimated PFS hazard ratio was 0.43 (95% confidence interval: 0.20, 0.94; p=0.03) for MDT compared with systemic therapy. There were no grade 3 or greater adverse events with at least possible attribution to MDT, and only one grade 2 adverse event possibly related to treatment in the MDT arm occurred. Increased systemic T-cell stimulatory cytokines, CD8+ T-cell activation, CD8+ T-cell proliferation, and T-cell receptor clonal expansion following treatment were associated with the MDT arm compared with the control arm (all p<0.05). Conclusions: Among patients with oligometastatic PDAC, the combination of MDT plus systemic therapy was associated with improved PFS compared with systemic therapy alone. Further exploration in phase III trials is warranted, as is investigation into the potential therapeutic implications of systemic immune activation associated with MDT receipt. Clinical trial information: NCT03599765 .

Pre-treatment 18F-FDG-PET/CT parameters as biomarkers for progression free survival, best overall response and overall survival in metastatic melanoma patients undergoing first-line immunotherapy.

Checkpoint inhibitors have drastically improved the therapy of patients with advanced melanoma. 18F-FDG-PET/CT parameters might act as biomarkers for response and survival and thus can identify patients that do not benefit from immunotherapy. However, little literature exists on the association of baseline 18F-FDG-PET/CT parameters with progression free survival (PFS), best overall response (BOR), and overall survival (OS). Using a whole tumor volume segmentation approach, we investigated in a retrospective registry study (n = 50) whether pre-treatment 18F-FDG-PET/CT parameters of three subgroups (tumor burden, tumor glucose uptake and non-tumoral hematopoietic tissue metabolism), can act as biomarkers for the primary endpoints PFS and BOR as well as for the secondary endpoint OS. Compared to the sole use of clinical parameters, baseline 18F-FDG-PET/CT parameters did not significantly improve a Cox proportional-hazard model for PFS (C-index/AIC: 0.70/225.17 and 0.68/223.54, respectively; p = 0.14). A binomial logistic regression analysis for BOR was not statistically significant (χ2(15) = 16.44, p = 0.35), with a low amount of explained variance (Nagelkerke's R2 = 0.38). Mean FDG uptake of the spleen contributed significantly to a Cox proportional-hazard model for OS (HR 3.55, p = 0.04). The present study could not confirm the capability of the pre-treatment 18F-FDG-PET/CT parameters tumor burden, tumor glucose uptake and non-tumoral hematopoietic tissue metabolism to act as biomarkers for PFS and BOR in metastatic melanoma patients receiving first-line immunotherapy. The documented potential of 18F-FDG uptake by immune-mediating tissues such as the spleen to act as a biomarker for OS has been reproduced.

A global phase 3 study of serplulimab plus chemotherapy as first-line treatment for advanced squamous non-small-cell lung cancer (ASTRUM-004)

Combining immunotherapy with chemotherapy can provide improved survival in advanced squamous non-small-cell lung cancer (NSCLC) patients without targetable gene alterations. 537 previously untreated patients with stage IIIB/IIIC or IV squamous NSCLC without targetable gene alterations were enrolled and randomized (2:1) to receive serplulimab 4.5mg/kg or placebo, both in combination with nab-paclitaxel and carboplatin, intravenously in 3-week cycles. The primary endpoint of progression-free survival (PFS) was met at the first interim analysis. At the second interim analysis, PFS benefit was maintained in serplulimab-chemotherapy group (hazard ratio [HR] 0.53, 95% confidence interval [CI] 0.42-0.67). At the final analysis, serplulimab-chemotherapy significantly improved median OS compared to placebo-chemotherapy (HR 0.73, 95% CI 0.58-0.93; p= 0.010). Grade ≥3 serplulimab or placebo-related adverse events occurred in 126 (35.2%) and 58 (32.4%) patients, respectively. Our results demonstrate that adding serplulimab to chemotherapy significantly improves survival in advanced squamous NSCLC patients, with manageable safety.

Zotiraciclib (TG02) for newly diagnosed glioblastoma in the elderly or for recurrent glioblastoma: The EORTC 1608 STEAM trial

BackgroundZotiraciclib (TG02) is an oral multi-cyclin dependent kinase (CDK) inhibitor thought to inhibit tumor growth via CDK-9-dependent depletion of survival proteins such as c-MYC and MCL-1 which are frequently overexpressed in glioblastoma. MethodsEORTC 1608 (NCT03224104) (STEAM) had a three parallel group (A,B,C) phase Ib, open-label, non-randomized, multicenter design in IDH wild-type newly diagnosed glioblastoma or anaplastic astrocytoma. Groups A and B explored the maximum tolerated dose (MTD) of TG02 in elderly patients, in combination with hypofractionated radiotherapy alone (group A) or temozolomide alone (group B), according to O6-methylguanine DNA methyltransferase promoter methylation status determined centrally. Group C explored single agent activity of TG02 at first relapse after temozolomide chemoradiotherapy with a primary endpoint of progression-free survival at 6 months (PFS-6). Tumor expression of CDK-9, c-MYC and MCL-1 was determined by immunohistochemistry. ResultsThe MTD was 150 mg twice weekly in combination with radiotherapy alone (group A) or temozolomide alone (group B). Two dose-limiting toxicities were observed at 150 mg: one in group A (grade 3 seizure), one in group B (multiple grade 1 events). Main toxicities included neutropenia, gastrointestinal disorders and hepatotoxicity. PFS-6 in group C was 6.7%. CDK-9, c-MYC and MCL-1 were confirmed to be expressed and their expression was moderately cross-correlated. High protein levels of MCL-1 were associated with inferior survival. ConclusionsTG02 exhibits overlapping toxicity with alkylating agents and low single agent clinical activity in recurrent glioblastoma. The role of CDK-9 and its down-stream effectors as prognostic factors and therapeutic targets in glioblastoma warrants further study.

Comparison of Methotrexate Maintenance Versus Autologous Stem Cell Transplant Consolidation after High-Dose Methotrexate-Based Induction Therapy in Primary Central Nervous System Lymphoma

Background: Primary central nervous system lymphoma (PCNSL) is a rare form of non-Hodgkin lymphoma with historically poor outcomes. Induction therapy with high-dose methotrexate (HD-MTX)-based regimens followed by consolidation with autologous stem cell transplant (auto-SCT) has become the mainstay of treatment with overall response rates (ORR) of 69-87% and two-year overall survival (OS) of 66-70% reported in prospective clinical trials. Limited data are available regarding a maintenance approach with single-agent HD-MTX, particularly in patients who are not auto-SCT candidates. Herein, we describe a comparison of outcomes in patients with PCNSL who underwent HD-MTX-based induction followed by either HD-MTX maintenance or auto-SCT consolidation at Mayo Clinic, Rochester. Methods: Patients with a diagnosis of PCNSL who received HD-MTX as part of induction therapy at Mayo Clinic between October 2010 and June 2022 were identified. Patients with prior or concurrent diagnosis of systemic lymphoma were excluded. Primary endpoints were progression-free survival (PFS) defined as time from post-induction treatment initiation to relapse, progression, or death due to any cause; and OS defined as time from post-induction treatment initiation to death due to any cause. We compared baseline characteristics by post-induction therapy using descriptive statistics. The primary endpoints PFS and OS were evaluated using Kaplan-Meier curves and compared by risk scores using a log-rank test. Results: A total of 148 patients were identified (51% female, 95% white) with median age at diagnosis of 66 years (range 29-85), with 48 patients (32%) age > 70. Most patients had multifocal disease (n=89, 60%) and deep brain involvement (n=100, 70%) at diagnosis. Few had vitreoretinal (n=15, 10%) or CSF involvement (n=9, 6%) at diagnosis. Using the Memorial Sloan Kettering (MSKCC) prognostic score for PCNSL, 35 patients (26%) scored class 3 (poor prognosis), 85 (62%) scored class 2, and 17 (12%) scored class 1. In total, 117 patients (79%) received methotrexate, rituximab, and temozolomide (MRT) induction therapy, and the remaining 31 patients (21%) received methotrexate and rituximab (MR) induction therapy (Table 1). A total of 70 patients (47%) underwent consolidation with auto-SCT and 37 patients (25%) received maintenance methotrexate. The patients who received maintenance methotrexate had higher median age of 72 versus 62 years, higher proportion of patients older than 70 (54% versus 16%, p<0.001), higher proportion of MSKCC prognostic score class 3 patients (33% versus 17%, p=0.026), and trend towards higher proportion of patients ECOG 2 or higher (41% versus 29%, p=0.109). A higher proportion of patients who underwent auto-SCT received MRT (vs MR) induction (n=64, 91%) compared to those who received maintenance methotrexate (n=24, 65%, p=0.004) (Table 1). The median follow-up for all patients was 4.5 years. At 1-, 3-, and 5-years post-induction treatment initiation, the PFS in the auto-SCT cohort was 85.8% (95% CI 77.7-94.9), 81.0% (95% CI 72.0-91.0), and 74.6% (95% CI 63.3-87.9), respectively; and the PFS in the HD-MTX maintenance cohort was 88.6% (95% CI 78.7-99.8), 72.6% (95% CI 58.8-89.8), and 72.6% (95% CI 58.8-89.8), respectively. At the same time points, the OS in the auto-SCT cohort was 94.0% (95% CI 88.4-99.9), 81.3% (95% CI 71.8-92.0), and 76.0% (95% CI 65.0-89.0), respectively; and the OS in the HD-MTX maintenance cohort was 94.3% (95% CI 86.9-100.0), 87.5% (76.8-99.8%), and 82.4% (69.0-98.4), respectively. Overall, there was no significant difference in PFS (p=0.64) or OS (p=0.95) based on post-induction treatment (Figure 1). Conclusions: Our study demonstrates comparable outcomes in PCNSL between a post-induction treatment approach with maintenance HD-MTX and consolidation auto-SCT, even though baseline characteristics indicate that patients who went on to receive auto-SCT were younger and had overall better performance status. This suggests that maintenance HD-MTX is a reasonable, time-limited strategy for patients with PCNSL responding to initial induction therapy, particularly in patients who are not candidates for auto-SCT.

Progression-Free Survival (PFS) and Toxicity with Nivolumab-AVD Compared to Brentuximab Vedotin-AVD in Pediatric Advanced Stage (AS) Classic Hodgkin Lymphoma (cHL), Results of SWOG S1826

Background: Approaches to therapy in pediatric and adult cHL have differed historically. Brentuximab vedotin (BV) is efficacious in pediatric patients (pts) with high-risk cHL when combined with chemotherapy and response based involved site radiation therapy (RT) ( Castellino. NEJM 2022). Inhibition of the PD-1 pathway, central to the pathogenesis of cHL, is safe and effective in children with relapsed HL but has not been evaluated in the frontline setting. Led by SWOG, the National Clinical Trials Network (NCTN) conducted the randomized, phase 3 trial S1826 to evaluate nivolumab (N)-AVD vs BV-AVD in pts ages ≥12 years (y) with newly diagnosed Stage 3-4 cHL. Methods: Eligible pts were randomized 1:1 to either 6 cycles of N-AVD or BV-AVD. At randomization enrollment was stratified by age, International Prognostic Score (IPS), and intent to use RT. Treating site of pts 12-17y, the subject of this subgroup analysis, declared intent to use RT for residual metabolically active lesions on the end of treatment PET per protocol. Recipients of BV-AVD were required to receive G-CSF prophylaxis vs optional with N-AVD. Dexrazoxane was permitted, but not mandated. Response and disease progression was assessed by investigators using the 2014 Lugano Classification. The primary endpoint was PFS; secondary endpoints included overall survival (OS), event-free survival (EFS), and safety. Results: Of 976 eligible pts enrolled (from 7/9/2019 to 10/5/2022): 24.3% (n=237) were 12-17 y and randomized to N-AVD (n=120) or BV-AVD (n=117). Median age was 15.6 y (range, 12-17.9 y), 50% of pts were male, 69% were white, 15% were black, and 18% were Hispanic. 27% had an IPS score 4-7. At the 2nd interim analysis (50% of total PFS events) the SWOG Data and Safety Monitoring Committee recommended reporting the primary results as the primary PFS endpoint crossed the protocol-specified conservative statistical boundary for the full trial. In the pediatric cohort, 6 PFS events were observed after N-AVD compared to 12 events after BV-AVD. At a median follow-up of 12.1 months, the PFS was compared between arms [HR 0.48, 95% CI 0.18-1.28, stratified one-sided logrank p=0.067) in the pediatric cohort; 1 y PFS: N-AVD, 94%, BV-AVD, 88% (Fig.1). There have been no deaths in this age group. Overall use of RT was 0.8% (2/237) and 79% of pediatric pts received dexrazoxane. The rate of grade (gr) ≥ 3 hematologic adverse events (AE) was 45% after N-AVD compared to 41% after BV-AVD, with 3% gr ≥ 3 febrile neutropenia and 1% with sepsis after either regimen, despite differences in GCSF use (59.2% N, 93.2% BV). Overall rates of immune related AEs (irAEs) (any gr) were low: pneumonitis (3.0% N vs 1% BV), and colitis (0% N vs 1% BV). Rash (any gr) was more common in BV-AVD (2% N vs 14% BV). Hypo/hyperthyroidism (any gr) was higher after N-AVD (2% N vs 0% BV). Rates of transaminitis were similar (ALT elevation: 42% N vs 54% BV). While sensory peripheral neuropathy was more frequent after BV-AVD (sensory: 18% N vs 29% BV; motor: 8% N vs 5% BV), only 1% was > grade 3. Discontinuation of N vs BV therapy occurred in 8.3% vs 2.6% of pediatric pts respectively, compared to 7.9% vs 21.1% of adults. Conclusions: In early follow-up, N-AVD and BV-AVD are well tolerated and associated with low rates of irAEs in pts ages 12-17 y. With 12.1 mos median follow-up the PFS benefit observed for N-AVD in pediatric pts mirrors that observed in the overall study. RT usage is lower, and cumulative doxorubicin dose is higher than historical pediatric cHL trials. The difference in rate of discontinuation between study arms and by age group needs further evaluation. Longer follow-up is needed to better define the roles of N-AVD and Bv-AVD for AS cHL. S1826 is a model NCTN trial, providing earlier access to novel agents and harmonization of treatment for adolescents and young adults with AS cHL. Funding: NIH/NCI/NCTN grants U10CA180888 and U10CA180819, U10CA180820, U10CA180821, U10CA180863, U10 CA180886; and Bristol-Myers Squibb. Bv provided by Seagen (Canada Only). Clinical Trial NCT03907488.

Combination of tumor asphericity and an extracellular matrix-related prognostic gene signature in non-small cell lung cancer patients

One important aim of precision oncology is a personalized treatment of patients. This can be achieved by various biomarkers, especially imaging parameters and gene expression signatures are commonly used. So far, combination approaches are sparse. The aim of the study was to independently validate the prognostic value of the novel positron emission tomography (PET) parameter tumor asphericity (ASP) in non small cell lung cancer (NSCLC) patients and to investigate associations between published gene expression profiles and ASP. This was a retrospective evaluation of PET imaging and gene expression data from three public databases and two institutional datasets. The whole cohort comprised 253 NSCLC patients, all treated with curative intent surgery. Clinical parameters, standard PET parameters and ASP were evaluated in all patients. Additional gene expression data were available for 120 patients. Univariate Cox regression and Kaplan–Meier analysis was performed for the primary endpoint progression-free survival (PFS) and additional endpoints. Furthermore, multivariate cox regression testing was performed including clinically significant parameters, ASP, and the extracellular matrix-related prognostic gene signature (EPPI). In the whole cohort, a significant association with PFS was observed for ASP (p < 0.001) and EPPI (p = 0.012). Upon multivariate testing, EPPI remained significantly associated with PFS (p = 0.018) in the subgroup of patients with additional gene expression data, while ASP was significantly associated with PFS in the whole cohort (p = 0.012). In stage II patients, ASP was significantly associated with PFS (p = 0.009), and a previously published cutoff value for ASP (19.5%) was successfully validated (p = 0.008). In patients with additional gene expression data, EPPI showed a significant association with PFS, too (p = 0.033). The exploratory combination of ASP and EPPI showed that the combinatory approach has potential to further improve patient stratification compared to the use of only one parameter. We report the first successful validation of EPPI and ASP in stage II NSCLC patients. The combination of both parameters seems to be a very promising approach for improvement of risk stratification in a group of patients with urgent need for a more personalized treatment approach.

CTNI-34. ZOTIRACICLIB (TG02) FOR NEWLY DIAGNOSED GLIOBLASTOMA IN THE ELDERLY OR FOR RECURRENT GLIOBLASTOMA: FINAL RESULTS OF THE EORTC 1608 STEAM TRIAL

Abstract BACKGROUND Zotiraciclib (TG02) is an oral multi-cyclin dependent kinase (CDK) inhibitor that is supposed to suppress tumor growth via CDK-9-dependent depletion of survival proteins such as c-MYC and MCL-1 which are frequently overexpressed in glioblastoma. METHODS EORTC 1608 (NCT03224104) (STEAM) had a three parallel group (A,B,C) phase Ib, open-label, non-randomized, multicenter design. Groups A and B explored the maximum tolerated dose (MTD) of TG02 in elderly patients with IDH1R132H-non-mutant newly diagnosed glioblastoma or anaplastic astrocytoma, in combination with hypofractionated radiotherapy alone (group A) or temozolomide alone (group B), based on O6-methylguanine DNA methyltransferase promoter methylation status determined centrally. Group C explored single agent activity of TG02 in IDH1R132H-non-mutant glioblastoma or anaplastic astrocytoma at first relapse after temozolomide chemoradiotherapy with a primary endpoint of progression-free survival at 6 months. Secondary objectives included efficacy, quality of life, and safety. Expression of CDK-9, c-MYC and MCL-1 was determined by immunohistochemistry. RESULTS The MTD was 150 mg twice weekly in combination with radiotherapy alone (group A) or temozolomide alone (group B) in elderly patients. Two dose-limiting toxicities were observed at 150 mg, one in group A (grade 3 seizure) and one in group B (multiple grade 1 events). Main toxicities included neutropenia, gastrointestinal disorders, and hepatotoxicity. Progression-free survival at 6 months in group C was 6.7%. CDK9 and its indirect targets, c-MYC and MCL-1, were confirmed to be expressed and their expression was correlated, supporting a regulatory role for CDK-9. The protein levels of CDK-9 and MCL-1 correlated with overall survival. CONCLUSION TG02 exhibits overlapping toxicity with alkylating agents and low clinical activity as a single agent. Larger randomized trials are required to explore activity in combination with RT or TMZ. The role of CDK-9 and its down-stream effectors as prognostic factors and therapeutic targets in glioblastoma warrants further study.

Subcutaneous daratumumab plus pomalidomide and dexamethasone versus pomalidomide and dexamethasone in patients with relapsed or refractory multiple myeloma (APOLLO): extended follow up of an open-label, randomised, multicentre, phase 3 trial

The primary analysis of the APOLLO trial, done after a median follow-up of 16·9 months, showed that daratumumab plus pomalidomide and dexamethasone significantly improved progression-free survival versus pomalidomide and dexamethasone. Here, we report the final overall survival and updated safety results from APOLLO. APOLLO was an open-label, randomised, phase 3 trial conducted at 48 academic centres and hospitals across 12 countries in Europe, that included adults aged 18 years or older with relapsed or refractory multiple myeloma who had an ECOG performance status score of 0-2, had received at least one previous line of therapy, including lenalidomide and a proteasome inhibitor, had a partial response or better to one or more previous lines of antimyeloma therapy, and were refractory to lenalidomide if they had received only one previous line of therapy. An interactive web-response system was used to randomly assign patients (1:1) to receive daratumumab plus pomalidomide and dexamethasone or pomalidomide and dexamethasone; patients were stratified by the number of previous lines of therapy and International Staging System disease stage. Oral pomalidomide (4 mg once daily; days 1-21) and dexamethasone (40 mg once daily; days 1, 8, 15, and 22) were given in 28-day cycles until disease progression or unacceptable toxicity. Daratumumab (1800 mg subcutaneously or 16 mg/kg intravenously) was administered weekly (cycles 1-2), every 2 weeks (cycles 3-6), and every 4 weeks thereafter. The primary endpoint of progression-free survival, which has previously been reported, and the pre-planned secondary endpoint of overall survival were assessed in the intention-to-treat population. This trial is registered with ClinicalTrials.gov (NCT03180736) and is no longer enrolling patients. Between June 22, 2017, and June 13, 2019, 304 patients were randomly assigned: 151 to the daratumumab plus pomalidomide and dexamethasone group and 153 to the pomalidomide and dexamethasone group. The median age was 67 years (IQR 60-72); 143 (47%) patients were female and 161 (53%) were male, and 272 (89%) were White. At a median follow-up of 39·6 months (IQR 37·1-43·7), median overall survival was 34·4 months (95% CI 23·7-40·3) in the daratumumab plus pomalidomide and dexamethasone group versus 23·7 months (19·6-29·4) in the pomalidomide and dexamethasone group (hazard ratio [HR] 0·82 [95% CI 0·61-1·11]; p=0·20). The most common grade 3-4 treatment-emergent adverse events were neutropenia (103 [69%] of 149 with daratumumab plus pomalidomide and dexamethasone vs 76 [51%] of 150 with pomalidomide and dexamethasone), anaemia (27 [18%] vs 32 [21%]), and thrombocytopenia (27 [18%] vs 28 [19%]). Serious treatment-emergent adverse events occurred in 80 (54%) of 149 patients in the daratumumab plus pomalidomide and dexamethasone group and in 60 (40%) of 150 patients in the pomalidomide and dexamethasone group, the most common of which was pneumonia (23 [15%] of 149 vs 13 [9%] of 150). Treatment-emergent adverse events resulting in death occurred in 13 (9%) of 149 patients in the daratumumab plus pomalidomide and dexamethasone group and in 13 (9%) of 150 patients in the pomalidomide and dexamethasone group, with 4 (3%) of 151 adverse events leading to death within 30 days of the last treatment dose thought to be related to study treatment in the daratumumab plus pomalidomide and dexamethasone group (septic shock [n=1]; sepsis [n=1]; bone marrow failure, campylobacter infection, and liver disorder [n=1]; and pneumonia [n=1]) and none in the pomalidomide and dexamethasone group. Although the difference in overall survival observed between treatment groups was not significant, the safety profile results with long-term follow-up reported here continue to support the use of daratumumab plus pomalidomide and dexamethasone in patients with relapsed or refractory multiple myeloma. European Myeloma Network and Janssen Research & Development.

Tucidinostat plus exemestane for postmenopausal patients with advanced, hormone receptor-positive breast cancer: a long-term safety and overall survival update from the randomised, double-blind, placebo-controlled, phase 3 trial.

The ACE study previously demonstrated that tucidinostat (chidamide), a subtype-selective histone deacetylase (HDAC) inhibitor, plus exemestane significantly improved progression-free survival (PFS) in advanced hormone receptor-positive (HR+) breast cancer patients with a manageable safety profile. The analysis of long-term safety and overall survival (OS) is presented here. ACE is a randomized, double-blind, placebo-controlled, phase 3 trial comparing tucidinostat 30 mg/twice weekly plus exemestane 25 mg/day versus placebo plus exemestane 25 mg/day in postmenopausal patients with advanced, HR+ breast cancer. The primary endpoint was PFS, and OS was the secondary endpoint. Of the 365 patients enrolled between July 2015, and June 2017, 244 were assigned to tucidinostat plus exemestane (tucidinostat group) and 121 to placebo plus exemestane group (placebo group). Baseline characteristics were well balanced between groups. The median follow-up from randomization to data cut-off (February 25, 2021) of this analysis was 26.5 months (range, 13.9-45.5 months). A total of 231 deaths (63.3%) from 365 patients occurred, including 155 deaths (63.5%) in the tucidinostat group and 76 deaths (62.8%) in the placebo group. The median OS was 30.3 months (95% CI, 26.7-36.7) in the tucidinostat group and 30.3 months (95% CI, 24.8-38.1) in the placebo group. The safety profiles of both tucidinostat and placebo groups remained consistent with those previously reported, and no new safety signals were observed with longer follow-up. Neutropenia of grade 3 or 4 occurred in 51.6% of the patients in the tucidinostat group and 2.5% of the patients in the placebo group. Adverse events (AEs) that led to treatment discontinuations from any cause occurred in 28 (11.5%) patients in the tucidinostat group and 4 (3.3%) in the placebo group. Although tucidinostat in combination with exemestane had produced a clinically meaningful and statistically significant improvement in the primary endpoint PFS, the ACE study did not show a prolongation of the secondary endpoint OS in the tucidinostat combination regimen. Ongoing studies have been considered in terms of potential identification of what patient subpopulations could benefit most from the tucidinostat combination regimens in advanced HR+ breast cancer.

Nivolumab (NIVO) plus relatlimab (RELA) vs NIVO in previously untreated metastatic or unresectable melanoma: 2-year results from RELATIVITY-047.

9502 Background: In RELATIVITY-047 (NCT03470922), NIVO + RELA demonstrated a statistically significant progression-free survival (PFS) benefit vs NIVO; there was an observed improvement in overall survival (OS) although it was not statistically significant. The combination also had a descriptively higher confirmed objective response rate (ORR) assessed by blinded independent central review (BICR) vs NIVO. Here we report updated descriptive analyses (efficacy, safety, and secondary analyses) with longer (~ 2 years) follow-up. Methods: Patients were randomized 1:1 to receive NIVO 480 mg + RELA 160 mg fixed-dose combination or NIVO 480 mg every 4 weeks, as previously described. Primary endpoint of PFS per RECIST v1.1 was assessed by BICR; secondary endpoints included OS and ORR per BICR. Exploratory analyses were performed for melanoma-specific survival (MSS; defined as death due to melanoma, with censoring of deaths due to other causes) and efficacy outcomes on subsequent systemic therapy. Results: Patients received NIVO + RELA (n = 355) or NIVO (n = 359). Median follow-up was 25.3 months in this updated analysis (minimum follow-up, 21.0 months). NIVO + RELA continued to show a benefit over NIVO for PFS, OS and ORR (Table). A similar improvement was also observed in MSS. NIVO + RELA was generally favored over NIVO across key subgroups (consistent with previous reports). Subsequent systemic therapy was received by 131 (36.9%) and 136 (37.9%) patients in the NIVO + RELA and NIVO arms, respectively. Treatment-related adverse events (TRAEs; any grade) leading to treatment discontinuation were observed in 61 (17.2%) and 31 (8.6%) patients on NIVO + RELA and NIVO, respectively. Grade 3–4 TRAEs were observed in 78 (22.0%) patients on NIVO + RELA and 43 (12.0%) patients on NIVO. In total, there were 6 treatment-related deaths (NIVO + RELA, n = 4; NIVO, n = 2); no new treatment-related deaths have been reported since the last analysis. Conclusions: With 12.3 months of additional follow-up, a consistent benefit was observed with NIVO + RELA vs NIVO for PFS, OS and ORR in the ITT population, as well as in key patient subgroups. MSS was longer with NIVO + RELA compared with NIVO. The safety profile of NIVO + RELA remained consistent with previous reports, with no new or unexpected safety signals. Efficacy outcomes on subsequent systemic therapy (by type of subsequent therapy, including PD-L1/CTLA-4) will be presented. Clinical trial information: NCT03470922 . [Table: see text]

Indirect treatment comparison of first-line CDK4/6-inhibitors in post-menopausal patients with HR+/HER2- metastatic breast cancer.

1071 Background: In phase III studies, the CDK4/6-inhibitors palbociclib, ribociclib, and abemaciclib all have demonstrated similar clinical efficacy in hormone receptor-positive (HR+)/human epidermal growth factor receptor 2 negative (HER2-) metastatic breast cancer (MBC) with regards to the primary endpoint of progression-free survival (PFS). However, the lack of overall survival (OS) benefit in the PALOMA-2 study is inconsistent with the OS benefit seen with the other two CDK4/6-inhibitors. This study sought to elucidate indirect treatment survival outcomes between CDK4/6-inhibitors in this setting. Methods: Phase III randomized controlled trials comparing first-line aromatase inhibitor with or without a CDK4/6-inhibitor in post-menopausal patients with HR+/HER2- MBC. A graphical reconstructive algorithm was utilized to retrieve patient level time-to-event data from reported Kaplan-Meier OS and PFS curves. Survival analyses were conducted with Cox proportional hazards model with a shared-frailty term incorporated to account for inter-study differences. Two-stage indirect treatment comparison model was conducted as a sensitivity analysis. Results: Three randomized phase III trials – PALOMA-2, MONALEESA-2 and MONARCH-3 – comprising 1,827 patients were included. Indirect pairwise comparison of all CDK4/6-inhibitor showed no significant PFS differences across one-stage and two-stage models (all p&gt;0.05). Likewise, indirect treatment comparison between ribociclib vs palbociclib (one-stage: HR=0.903, 95%-CI: 0.746-1.094, p=0.297), abemaciclib vs palbociclib (one-stage: HR=0.843, 95%-CI: 0.690-1.030, p=0.094) and abemaciclib vs ribociclib (one-stage: HR=0.933, 95%-CI: 0.753-1.157, p=0.528) failed to demonstrate a significant OS difference. Conclusions: Findings from this indirect treatment comparison suggest no significant PFS or OS differences between CDK4/6-inhibitor agents when combined with an aromatase inhibitor in post-menopausal patients with HR+/HER- MBC. [Table: see text]

Zotiraciclib (TG02) for newly diagnosed glioblastoma in the elderly or for recurrent glioblastoma: The EORTC 1608 STEAM trial.

2054 Background: Zotiraciclib (TG02) is an oral multi-cyclin dependent kinase (CDK) inhibitor, including CDK-9, that inhibits tumor growth down-stream via depletion of survival proteins such as MCL-1 and MYC. MCL-1 and MYC are frequently overexpressed in glioblastoma. Methods: The EORTC 1608 (NCT03224104) (STEAM) phase 1b trial had a three parallel group (A,B,C) open-label, non-randomized, multicenter design. Groups A and B explored the maximum tolerated dose (MTD) of zotiraciclib in elderly patients (more than 65 years) with IDH1R132H-non-mutant newly diagnosed glioblastoma or anaplastic astrocytoma, in combination with hypofractionated radiotherapy alone (group A) or temozolomide alone (group B), based on O6-methylguanine DNA methyltransferase promoter methylation status determined centrally. Group C explored single agent activity of zotiraciclib in IDH1R132H-non-mutant glioblastoma or anaplastic astrocytoma at first relapse after temozolomide chemoradiotherapy with a primary endpoint of progression-free survival at 6 months. Secondary objectives included efficacy, quality of life, and safety. Results: The MTD was 150 mg in combination with radiotherapy alone (group A, n=12) or temozolomide alone (group B, n=9) in elderly patients. Two dose-limiting toxicities were observed at 150 mg, one in group A (grade 3 seizure) and one in group B (multiple grade 1 events). Main toxicities included neutropenia, gastro-intestinal disorders, and hepatotoxicity. Progression-free survival at 6 months in group C (n=50) was 6.7%. Conclusions: Zotiraciclib exhibits overlapping toxicity with alkylating agents and low clinical activity as a single agent. Larger randomized trials may be required to explore activity in combination with radiotherapy or temozolomide. Clinical trial information: NCT03224104 .

Abstract OT2-16-05: Safety Analyses of NRG BR004: A Randomized, Double-blind, Phase III Trial of Taxane/Trastuzumab/Pertuzumab with Atezolizumab or Placebo in First-line HER2-Positive Metastatic Breast Cancer (MBC)

Abstract Background: The CLEOPATRA trial established trastuzumab, pertuzumab and a taxane (THP) as a standard of care for first line metastatic, HER2-positve breast cancer with median progression-free survival (PFS) of 18.7 months and median OS of 57 months. NRG BR004 was a phase III, placebo-controlled trial designed to determine whether the addition of the PD-L1 inhibitor, atezolizumab, to THP would improve progression-free survival (PFS), relative to THP/placebo in patients with newly documented HER2-positive measurable metastatic breast cancer. Methods: BR004 was designed to detect an improvement in the primary endpoint of PFS in patients with measurable disease from 16.5 to 22.5 months with addition of atezolizumab (HR 0.733). A sample size of 600 would provide 80% power with a type I error rate of 0.05 to detect such an improvement when 326 PFS events had been reported. Monthly accrual was projected at 30 patients per month with completion of accrual in 24 months. In addition to routine monitoring of safety data by the IDMC every 6 months, a formal analysis of the toxicity data was to be performed 16 weeks after the 100th patient had been randomized with review by the IDMC. Results: First patient was randomized on May 1, 2019, and after 37 months 190 patients had been randomized. Several amendments were not successful in addressing the low accrual rate. The IDMC began regular monitoring of safety and accrual data in July 2020 and reviewed the formal safety analysis in February 2022. As of the February 2022 IDMC meeting, four Grade 5 adverse events (AEs) had been reported (2 occurring in 2020 and 2 in 2021), one of which occurred in a patient with evolving liver failure due to rapid disease progression at the start of therapy. The recommendation was to continue without modification, but notice was given the Grade 5 AEs had occurred on the same treatment arm without unblinding. When additional Grade 5 AEs occurred on 3/4/2022 and 4/27/2022 both on the same study arm with none reported on the other arm, accrual was held until the IDMC could review updated safety data, narratives of the Grade 5 AEs and the overall context of the trial. There was no evidence of clinically important imbalances between Grade 3 and Grade 4 AEs between the arms., Based on an uncertain but material safety signal, the ongoing accrual challenges, and determination that the clinical question being addressed was no longer sufficiently compelling, the IDMC recommended that the trial should be permanently closed to further enrollment. Summary safety data from 187 treated patients are provided in the Table. A decision was made to discontinue atezolizumab/placebo in patients receiving the investigational component of the trial therapy and unblind investigators and patients. The study will continue to collect information on PFS events, deaths and late immune AEs through April of 2024 when PFS and OS will be analyzed. Conclusions: The imbalance in Grade 5 AEs which occurred on BR004 coupled with continued poor accrual and the changing landscape in HER2+ MBC resulted in early closure of enrollment and unblinding of patients. Follow-up continues to assess PFS, OS and monitor for delayed immune AEs. Support: U10CA180868, -189867, -180822; U24CA196067; and Genentech. Citation Format: Charles E. Geyer, Jr, Gong Tang, Priya Rastogi, Vicente Valero, Stephen K. Chia, Erin F. Cobain, Elias Obeid, David B. Page, Andrew S. Poklepovic, William J. Irvin, Jr., Adam M. Brufsky, Irene L. Wapnir, Jennifer M. Suga, Eleftherios (Terry) Mamounas, Norman Wolmark. Safety Analyses of NRG BR004: A Randomized, Double-blind, Phase III Trial of Taxane/Trastuzumab/Pertuzumab with Atezolizumab or Placebo in First-line HER2-Positive Metastatic Breast Cancer (MBC) [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT2-16-05.