Bench to Bedside Development of [18F]Fluoromethyl-(1,2-2H4)choline ([18F]D4-FCH)

Malignant transformation is characterised by aberrant phospholipid metabolism of cancers, associated with the upregulation of choline kinase alpha (CHKα). Due to the metabolic instability of choline radiotracers and the increasing use of late-imaging protocols, we developed a more stable choline radiotracer, [18F]fluoromethyl-[1,2-2H4]choline ([18F]D4-FCH). [18F]D4-FCH has improved protection against choline oxidase, the key choline catabolic enzyme, via a 1H/2D isotope effect, together with fluorine substitution. Due to the promising mechanistic and safety profiles of [18F]D4-FCH in vitro and preclinically, the radiotracer has transitioned to clinical development. [18F]D4-FCH is a safe positron emission tomography (PET) tracer, with a favourable radiation dosimetry profile for clinical imaging. [18F]D4-FCH PET/CT in lung and prostate cancers has shown highly heterogeneous intratumoral distribution and large lesion variability. Treatment with abiraterone or enzalutamide in metastatic castrate-resistant prostate cancer patients elicited mixed responses on PET at 12-16 weeks despite predominantly stable radiological appearances. The sum of the weighted tumour-to-background ratios (TBRs-wsum) was associated with the duration of survival.

Multiplexed live-cell imaging for drug responses in patient-derived organoid models of cancer

Patient-derived organoid (PDO) models of cancer are a multifunctional research system that better recapitulates human disease as compared to cancer cell lines. PDO models can be generated by culturing patient tumor cells in extracellular basement membrane extracts (BME) and plating as three-dimensional domes. However, commercially available reagents that have been optimized for phenotypic assays in monolayer cultures often are not compatible with BME. Herein we describe a method to plate PDO models and assess drug effects using an automated live-cell imaging system. In addition, we apply fluorescent dyes that are compatible with kinetic measurements to simultaneously quantitate cell health and apoptosis. Image capture can be customized to occur at regular time intervals over several days. Users can analyze drug effects in individual Z-plane images or a Z Projection of serial images from multiple focal planes. Using masking, specific parameters of interest are calculated, such as PDO number, area, and fluorescence intensity. We provide proof-of-concept data demonstrating the effect of cytotoxic agents on cell health, apoptosis and viability. This automated kinetic imaging platform can be expanded to other phenotypic readouts to understand diverse therapeutic effects in PDO models of cancer.

First-in-class oral innate immune activator BXCL701 combined with pembrolizumab in patients with metastatic, castration-resistant prostate cancer (mCRPC) of small cell neuroendocrine (SCNC) phenotype: Phase 2a final results

176

Background: BXCL701 (talabostat), oral small molecule inhibitor of dipeptidyl peptidases (DPP)—primarily DPP8/9 & DPP4—triggers inflammasome to alert and prime immune cells, leading to induction of IL-18 & IL-1ß, bridging innate & adaptive immunity. BXCL701 is evaluated in a Phase 2 study in combination with pembrolizumab, in mCRPC patients with SCNC phenotype. SCNC is highly proliferative and aggressive with limited duration of response to platinum-based chemotherapy. Here are reported the results of the Phase 2a after enrollment of 32 patients for the SCNC cohort. The final results will be presented at the Symposium. Methods: Phase 2a patients with any SCNC histopathological features, either de novo or treatment-emergent including mixed SCNC, required to have progression by PCWG3 on ≥1 prior line of cytotoxic chemotherapy (patients who either have refused chemotherapy or are considered unsuitable for chemotherapy also permitted entry with prior approval by sponsor). Patients receive pembrolizumab (200 mg IV q3week) + BXCL701 0.2 mg BID on days 1-7 with step-up to 0.3 mg BID on days 8-14, and 0.3 mg BID on days 1-14 of subsequent cycles. Primary endpoint is Composite Response, either objective response by RECIST 1.1 or PSA50 or CTC count conversion from ≥5/7.5 mL to <5/7.5 mL from baseline. Study uses a Simon 2-stage minimax design with 15 evaluable patients in stage 1 and 13 in stage 2. Baseline markers and changes in relevant immune effector cells also evaluated. Results: As of 10/11/2022, 32 patients have been accrued, 27 of which are evaluable. 16 patients (59%) are treatment-emergent SCNC and 11 (41%) are de novo SCNC. 19 patients (70%) received prior platinum chemotherapy. BXCL701 in combination with pembrolizumab continues to demonstrate acceptable tolerability without evidence of increased immune-related AEs compared to historic controls with checkpoint inhibitors. Adverse Events consistent with cytokine activation were observed (hypotension, fever, fatigue). In the previously reported 15 evaluable SCNC patients, 5 were composite responders, including 4 RECIST responders with a median duration of response of 39 weeks (range 9-45 weeks). 2/5 responders still actively receiving treatment and median duration of follow up is 48.3 weeks (range 1.9-88 weeks). All responders are MSS and/or low TMB. Enrollment is ongoing and 9 patients are actively receiving treatment at abstract submission. Final data for 28 evaluable patients will be presented at the Symposium. Conclusions: Oral BXCL701 in combination with pembrolizumab demonstrates encouraging anti-tumor activity with durability of response in late-line, refractory mCRPC SCNC for which there is currently no standard of care. BXCL701 BID dosing continues to demonstrate an acceptable safety profile. Clinical trial information: NCT03910660 .

Phase 1 efficacy and pharmacodynamic results of exicorilant + enzalutamide in patients with metastatic castration-resistant prostate cancer

145

Background: Metastatic castration-resistant prostate cancer (mCRPC) remains an incurable disease with significant morbidity. Androgen receptor (AR) signaling is a key driver of tumor growth in mCRPC, and AR-targeted therapies are the mainstay for patients (pts) with locally advanced or metastatic disease. Enzalutamide (ENZA) is commonly used, but resistance typically develops within 1–2 years. The glucocorticoid receptor (GR) can substitute for the AR, providing a tumor escape pathway (Arora et al. Cell 2013). In the 22Rv1 CRPC xenograft model, the selective GR modulator exicorilant (EXI) combined with ENZA reduced tumor growth, supporting the hypothesis that dual antagonism of GR + AR may block this escape pathway. Safety and pharmacokinetics from the first study of EXI + ENZA in pts with mCRPC (NCT03437941) were previously presented (Linch et al. ESMO 2022). Here, we report efficacy and pharmacodynamic (PD) results from the same study. Methods: Segment 1 (Seg 1) of this phase 1 study evaluated open-label, fasting, BID dosing of EXI (140 or 180 mg) + ENZA 160 mg QD. Segment 2 (Seg 2) tested QD dosing of EXI with food in a double-blind design: All pts received EXI 240 mg + ENZA and were randomized 3:1 to EXI titration (to 280 mg followed by 320 mg) or to remain on EXI 240 mg + placebo. Efficacy assessments included radiographic response and changes in prostate-specific antigen (PSA) levels. PSA was collected prior to study entry and PSA doubling times were calculated before and during treatment. PD analyses included baseline (BL) tumor GR expression and modulation of GR target genes in whole blood. As not all pts enrolled in Seg 1 were ENZA naïve, efficacy data are reported for Seg 2 only. Data cutoff date: July 7, 2022. Results: 39 pts were enrolled (Seg 1: 14, irrespective of prior ENZA exposure; Seg 2: 25, on a stable ENZA dose with rising PSA, defined as a 25% increase over nadir and absolute value >1 ng/mL). In Seg 2, there were no radiographic responses, 18 pts had a best overall response of stable disease per PCWG3, and 1 pt achieved a PSA response (≥50% PSA reduction from BL). BL tumor GR expression was detectable in all assessed tumors. PD analyses demonstrated EXI modulation of GR target genes, such as CDKN1C. Comparable PD effects were observed across EXI doses (240–320 mg QD). While BL 24-h urinary free cortisol (UFC) for most pts was within the normal range, improvements in PSA doubling times after treatment with EXI + ENZA were predominantly observed in pts with higher BL UFC ( P<0.05). Conclusions: This study did not include an ENZA-alone arm and was thus not designed to assess the contribution of EXI to the efficacy of the EXI + ENZA combination. In heavily pretreated pts with prior ENZA exposure, 1 PSA response and no radiographic responses were observed. PD analysis confirmed systemic GR modulation. Instances of PSA doubling time improvements were observed in pts with relatively higher UFC. Clinical trial information: NCT03437941 .

Tolerability of [177Lu]Lu-PSMA-617 by treatment exposure in patients with metastatic castration-resistant prostate cancer (mCRPC): A VISION study subgroup analysis

5047

Background: In the phase 3 VISION study, lutetium (177Lu) vipivotide tetraxetan ([177Lu]Lu-PSMA-617; 177Lu-PSMA-617) + protocol-permitted standard of care (SoC) improved clinical benefit and was generally well tolerated despite a higher rate of adverse events (AEs) than SoC alone. Here we assess AE incidence by exposure to 177Lu-PSMA-617. Methods: VISION was an international, open-label study of 177Lu-PSMA-617 in adults with PSMA-positive mCRPC previously treated with ≥ 1 androgen receptor pathway inhibitor and 1–2 taxane regimens. Patients received 177Lu-PSMA-617 (7.4 GBq every 6 weeks, ≤ 6 cycles) + SoC or SoC alone. rPFS and OS were primary endpoints; safety was a secondary endpoint. AE analysis by exposure to 177Lu-PSMA-617 was carried out in pre-specified subgroups. 177Lu-PSMA-617 cycle duration was generally ̃6 weeks and cycle 6 duration was until the earliest date of subsequent treatment, and date of last administration of randomized treatment (including SoC) + 30 days. The cycle of onset in which an AE first occurred in a patient at maximum grade was assessed. Results: The median duration of cycle of onset for cycles 1 to 5 was 6 weeks; for cycle 6, it was 26.6 weeks (Table). Of the 529 patients in the 177Lu-PSMA-617 group, 240 (45.4%) received ≤ 4 cycles and 289 (54.6%) received 5–6 cycles of treatment. In patients who received ≤ 4 or 5–6 cycles, 234 (97.5%) and 285 (98.6%) treatment-emergent AEs (TEAEs); 100 (41.7%) and 92 (31.8%) serious TEAEs; 205 (85.4%) and 246 (85.1%) treatment-related AEs; and 13 (5.4%) and 6 (2.1%) fatal TEAEs, respectively, were observed. Number of TEAEs and serious TEAEs by cycle of onset are shown in the Table. Conclusions: Over 50% of patients with mCRPC received 5–6 cycles of 177Lu-PSMA-617. For cycles 1–5, TEAEs occurred at every cycle, with similar frequency. More TEAEs were observed in cycle 6, reflecting its longer median duration than other cycles. Clinical trial information: NCT03511664. [Table: see text]

A first-in-human phase 1 trial of nx-1607, a first-in-class oral CBL-B inhibitor, in patients with advanced solid tumor malignancies

TPS2691

Background: Casitas B-lineage lymphoma proto-oncogene B (CBL-B) is an E3 ubiquitin ligase expressed in multiple immune cell lineages, which in contrast to cell surface immune checkpoints, acts as a regulator of both T and NK cell activation. Inhibition of CBL-B enhances T-cell response, increases response to suboptimal priming, and restores response in exhausted T cells. Thus CBL-B is a promising immune-oncology target and may overcome challenges seen with other T-cell directed therapies. NX-1607 is an oral small molecule inhibitor of CBL-B that has demonstrated anti-tumor activity and long-term survival in murine models as both a single agent and in combination with programmed cell death protein-1 (PD-1) antibodies. Further, NX-1607 elicits dose-dependent increases in cytokine secretion and proliferation in T-cell receptor-stimulated primary human T cells with enhanced tumor antigen-specific T-cell and NK cell anti-tumor responses. Thus, NX-1607 may be effective as a single agent or it may significantly enhance efficacy of other anti-tumor agents. Methods: NX-1607-101 is a first-in-human, multicenter, open-label, Phase 1 dose escalation and expansion trial evaluating NX-1607 in a variety of indications including platinum-resistant epithelial ovarian cancer (EOC), gastric cancer, squamous cell carcinoma of the head and neck (HNSCC), metastatic melanoma, non-small cell lung cancer (NSCLC), metastatic castration-resistant prostate cancer (mCRPC), malignant pleural mesothelioma (MPM), triple-negative breast cancer (TNBC), locally advanced or metastatic urothelial cancer, cervical cancer, microsatellite stable colorectal cancer (MSS CRC), and diffuse large B-cell lymphoma with Richter transformation (DLBCL-RT). The main objective is to establish the safety and tolerability of NX-1607, characterize PK/PD, and determine the recommended Phase 1b dose. NX-1607 will be given orally once daily at doses ranging from 5 to 100 mg in up to 6 dose levels. Dose escalation will proceed using an accelerated modified Fibonacci dose escalation design that transitions to a standard 3 + 3 design based on protocol-specific criteria. Up to 8 expansion cohorts in Phase 1b will be composed of patients with subsets of advanced cancers. Key eligibility criteria include patients with metastatic or unresectable disease that have progressed after prior therapy and for whom standard therapy with proven clinical benefit does not exist, is no longer effective, or is not appropriate. Prior treatment with immune checkpoint inhibitors or CAR-T cells with washout is allowed, but a history of active autoimmune disease is not. Up to 336 patients (60 in Phase 1a, 276 in Phase 1b using a Simon 2-stage design) will be enrolled at approximately 20 sites in the UK and US and treated until disease progression or unacceptable toxicity. Dose escalation is ongoing. Clinical trial information: NCT05107674.

Activation of the AKT pathway and outcomes in patients (pts) treated with or without ipatasertib (ipat) in metastatic castration-resistant prostate cancer (mCRPC): Next-generation sequencing (NGS) data from the phase III IPATential150 trial

5056

Background: Ipat + abiraterone (abi) significantly reduced the risk of radiographic disease progression vs placebo (pbo) + abi in pts with mCRPC and PTEN loss tumors by immunohistochemistry (IHC; HR, 0.77; 95% CI: 0.61, 0.98; P=0.034) but not in ITT pts (HR, 0.84; 95% CI: 0.71, 0.99; P=0.043; Sweeney Lancet 2021). A greater risk reduction was seen in pts with PTEN loss by NGS (HR, 0.65; 95% CI: 0.45, 0.95). We describe the efficacy and safety of pbo + abi vs ipat + abi at the second interim analysis (IA) of overall survival (OS) and explore the impact of AKT pathway alterations. Methods: Pts with mCRPC were randomized 1:1 to ipat (400 mg/d) + abi (1000 mg/d) + prednisone (5 mg bid) or pbo + abi + prednisone. Coprimary endpoints were investigator-assessed radiographic progression-free survival by Prostate Cancer Working Group 3 (PCWG3) criteria in pts with PTEN loss tumors by IHC (PTEN loss in ≥50% of tumor cells) and in ITT pts. Secondary endpoints in both populations included OS, objective response rate (ORR) per RECIST 1.1 and PCWG3 and time to pain progression (TPP). Ad hoc analyses assessed pts with PIK3CA/ AKT1/ PTEN alterations by NGS vs wildtype (WT). Results: Median follow-up was 31 mo (cutoff: 2021 Sept 30). In PTEN loss by IHC pts, median OS was 35.8 mo (n=261) with pbo + abi and 36.8 mo (n=260) with ipat + abi (HR: 0.95; 95% CI: 0.74, 1.21; P=0.665); in ITT pts, median OS was 36.7 mo (n=554) with pbo + abi and 40.3 mo (n=547) with ipat + abi (HR: 0.90; 95% CI: 0.76, 1.07). With longer follow-up, the safety profile was consistent with that of the primary analysis. In the full NGS evaluable population (n=743), ipat + abi was associated with better outcomes in pts with PIK3CA/ AKT1/ PTEN alterations (Table). Among pts with PTEN loss tumors by NGS (205 of the evaluable 518 pts), median OS was 29.8 mo (n=102) with pbo + abi and 35.8 mo (n=103) with ipat + abi (unstratified HR: 0.82; 95% CI: 0.56, 1.19). Conclusions: At the second IA, no significant improvement in OS was observed with ipat + abi in pts with PTEN loss by IHC. Exploratory analyses in pts with PIK3CA/ AKT1/ PTEN alterations by NGS suggest that these patients have poorer prognosis but may derive greater benefit from ipat + abi. Clinical trial information: NCT03072238. [Table: see text]

KEYNOTE-365 cohorts E and F: Phase 1b/2 study of pembrolizumab + lenvatinib combination therapy in patients with adenocarcinoma metastatic castration-resistant prostate cancer (mCRPC) or treatment-emergent neuroendocrine mCRPC (t-NE)

TPS215

Background: Standard of care for noncurative adenocarcinoma mCRPC is docetaxel or the next-generation hormonal agents (NHAs) abiraterone and enzalutamide. However, approximately 20% of patients develop t-NE after treatment for adenocarcinoma mCRPC; t-NE is associated with shorter survival, and it has no standard of care beyond combination platinum chemotherapy. The vascular endothelial growth factor (VEGF)/fibroblast growth factor receptor (FGFR) inhibitor lenvatinib inhibits proliferation and angiogenesis in preclinical models of adenocarcinoma prostate cancer. The phase 2 KEYNOTE-199 trial showed some antitumor activity with pembrolizumab monotherapy in docetaxel-pretreated patients with adenocarcinoma mCRPC. VEGF/FGFR inhibition combined with PD-1 inhibition may have enhanced benefit in mCRPC, for adenocarcinoma and possibly as a new treatment option for t-NE. Methods: KEYNOTE-365 (NCT02861573) is a nonrandomized, open-label, multicohort, phase 1b/2 trial designed to evaluate different pembrolizumab combination therapies in several patient populations with mCRPC. Cohort E will enroll patients with confirmed adenocarcinoma of the prostate without small cell histology, per investigator. Cohort F will enroll patients with t-NE (≥1% neuroendocrine cells in a recent biopsy specimen confirmed by central histology review). Each cohort will include patients who previously received docetaxel treatment for mCRPC. Prior treatment with ≤2 NHAs (for hormone-sensitive metastatic prostate cancer [mHSPC] or mCRPC) and 1 other chemotherapy for mCRPC is permitted. Additionally, enrollment in cohort F requires prostate cancer progression within 6 months of starting an NHA (for mHSPC or mCRPC) and within < 6 cycles of docetaxel for mCRPC. Each cohort will enroll 40-100 patients with Eastern Cooperative Oncology Group performance status score of 0 or 1. Both cohorts will receive pembrolizumab 200 mg IV every 3 weeks + oral lenvatinib 20 mg once daily until disease progression, withdrawal of consent, prespecified alanine aminotransaminase or aspartate aminotransaminase level increase, or other discontinuation event. Primary end points are safety and tolerability, prostate-specific antigen (PSA) response rate, and objective response rate (ORR) per RECIST v1.1 by blinded independent central review (BICR). Secondary end points include time to PSA progression; ORR and radiographic progression-free survival per Prostate Cancer Working Group 3 (PCWG3)–modified RECIST v1.1 by BICR; duration of response and disease control rate per RECIST v1.1 and PCWG3-modified RECIST v1.1 by BICR; and overall survival. These cohorts of KEYNOTE-365 are enrolling in Australia, Germany, New Zealand, Spain, and the United States. Clinical trial information: NCT02861573.

KEYNOTE-365 cohort I: Phase 1b/2 study of pembrolizumab combined with platinum-containing chemotherapy and chemotherapy alone for treatment-emergent neuroendocrine prostate carcinoma (t-NE)

TPS218

Background: In previously treated adenocarcinoma metastatic castration-resistant prostate cancer (mCRPC), approximately 20% of patients develop t-NE PC, which is aggressive with short overall survival (OS). t-NE PC treatment includes platinum-containing chemotherapy because of t-NE’s histologic, biologic, and clinical similarity to small cell/NE lung cancer. In the open-label, multicohort, phase 1b/2 KEYNOTE-365 study (NCT02861573), pembrolizumab, when combined with several agents for treatment of adenocarcinoma mCRPC, showed clinical activity and acceptable safety. To identify new treatment options for t-NE mCRPC, cohort I will help to evaluate platinum-containing chemotherapy alone or combined with pembrolizumab for patients with t-NE. Methods: Cohort I of the KEYNOTE-365 study will enroll patients with t-NE (≥1% neuroendocrine cells in a recent biopsy specimen confirmed by central histology review) and prior docetaxel treatment for mCRPC. Prior treatment with ≤2 next-generation hormonal agents (NHAs) for metastatic hormone-sensitive prostate cancer (mHSPC) or mCRPC and 1 other chemotherapy for mCRPC is permitted. Additionally, enrollment in cohort I requires previous prostate cancer progression within 6 months of starting an NHA (mHSPC or mCRPC) and within < 6 cycles of docetaxel for mCRPC. Each arm will enroll 40-100 patients with Eastern Cooperative Oncology Group performance status (ECOG PS) score of 0 or 1. Eligible patients will be randomly assigned 1:1 to receive pembrolizumab 200 mg IV on day 1 of each cycle every 3 weeks + carboplatin AUC of 5 IV on day 1 + etoposide 100 mg/m2 IV on days 1, 2, and 3 of each 21-day cycle for 4 cycles (arm 1) or the same chemotherapy regimen without pembrolizumab (arm 2). Pembrolizumab treatment will continue for up to 2 years until disease progression, unacceptable toxicity, or withdrawal of consent. Patients will be stratified by ECOG PS score (0 vs 1). Primary end points are safety and tolerability, prostate-specific antigen (PSA) response rate, and objective response rate (ORR) per RECIST v1.1 by blinded independent central review (BICR). Secondary end points include time to PSA progression; duration of response (DOR) and disease control rate (DCR) per RECIST v1.1 by BICR; ORR, DOR, DCR, and radiographic progression-free survival per Prostate Cancer Working Group 3–modified RECIST v1.1 by BICR; and OS. End points will be summarized for each arm without formal hypothesis testing. This cohort of KEYNOTE-365 is enrolling in Australia, Germany, New Zealand, Spain, and the United States. Clinical trial information: NCT02861573.

KEYNOTE-365 cohorts G and H: Phase 1b/2 study of pembrolizumab + vibostolimab combination therapy in patients with adenocarcinoma metastatic castration-resistant prostate cancer (mCRPC) or treatment-emergent neuroendocrine mCRPC (t-NE)

TPS204

Background: Treatment options are limited for patients with mCRPC that progresses after treatment with next-generation hormonal agents (NHAs)—such as enzalutamide and abiraterone acetate—or docetaxel. Approximately 20% of patients with adenocarcinoma mCRPC that progresses on androgen deprivation therapy develop t-NE mCRPC, which is associated with shortened overall survival (OS). The PD-1 inhibitor pembrolizumab showed antitumor activity as monotherapy in docetaxel-pretreated patients with adenocarcinoma mCRPC in the phase 2 KEYNOTE-199 trial. The T-cell immunoreceptor with Ig and ITIM domains (TIGIT) inhibitor vibostolimab showed antitumor activity when combined with pembrolizumab in pretreated patients with several tumor types in a phase 1 dose-escalation study. Combining PD-1 and TIGIT inhibition might have enhanced benefit in mCRPC, potentially both adenocarcinoma and t-NE. Methods: KEYNOTE-365 (NCT02861573) is a nonrandomized, open-label, multicohort, phase 1b/2 trial designed to evaluate the efficacy and safety of several pembrolizumab combination therapies in patients with mCRPC. Patients enrolled in cohort G will have confirmed adenocarcinoma of the prostate without small cell histology, per the investigator. Cohort H will enroll patients with t-NE (≥1% neuroendocrine cells in a recent biopsy specimen confirmed by central histology review). Each cohort will include patients who previously received docetaxel treatment for mCRPC. Prior treatment with ≤2 NHAs (for hormone-sensitive metastatic prostate cancer [mHSPC] or mCRPC) and 1 other chemotherapy for mCRPC is permitted. Enrollment in cohort H requires prostate cancer progression within 6 months of starting an NHA (for mHSPC or mCRPC) and within < 6 cycles of docetaxel for mCRPC. Each cohort will enroll 40-100 patients with Eastern Cooperative Oncology Group performance status score 0 or 1. Both cohorts will receive MK-7684A, a coformulation of pembrolizumab 200 mg and vibostolimab 200 mg, IV every 3 weeks. Treatment will continue until disease progression, withdrawal of consent, or other discontinuation event. Primary end points are safety and tolerability, prostate-specific antigen (PSA) response rate, and objective response rate (ORR) per RECIST v1.1 by blinded independent central review (BICR). Secondary end points include time to PSA progression; ORR and radiographic progression-free survival per Prostate Cancer Working Group 3 (PCWG3)–modified RECIST v1.1 by BICR; duration of response and disease control rate per RECIST v1.1 and PCWG3-modified RECIST v1.1 by BICR; and OS. These cohorts of KEYNOTE-365 are enrolling in Australia, Germany, New Zealand, Spain, and the United States. Clinical trial information: NCT02861573.

PSMAfore: A phase 3 study to compare 177Lu-PSMA-617 treatment with a change in androgen receptor pathway inhibitor in taxane-naïve patients with metastatic castration-resistant prostate cancer

TPS211

Background: [177Lu]Lu-PSMA-617 (177Lu-PSMA-617) is a high-affinity prostate-specific membrane antigen (PSMA)-targeted radioligand therapy that delivers β-particle radiation to PSMA-expressing cells and their surrounding microenvironment. In the phase 3 VISION trial, 177Lu-PSMA-617 significantly prolonged radiographic progression-free survival (rPFS) and overall survival (OS) in patients with metastatic castration-resistant prostate cancer (mCRPC) previously treated with ≥1 androgen receptor pathway inhibitor (ARPI) and 1–2 taxanes. PSMAfore is investigating the effect on rPFS in taxane-naïve patients with mCRPC treated with either 177Lu-PSMA-617 or a change in ARPI. Methods: PSMAfore (NCT04689828) is a multicenter, open-label, randomized phase 3 trial in adults with progressive mCRPC and confirmed PSMA expression by [68Ga]Ga-PSMA-11 PET/CT. Eligible patients are taxane-naïve in the metastatic setting and have: received one prior ARPI and are candidates for a change in ARPI; an Eastern Cooperative Oncology Group performance status of 0 or 1; a castrate level of serum/plasma testosterone ( < 50 ng/dL or < 1.7 nmol/L); and recovered to grade ≤2 from toxicities related to prior therapies. Approximately 450 patients will be randomized 1:1 to receive 177Lu-PSMA-617 (7.4 GBq i.v. every 6 weeks for 6 cycles) or a change in ARPI to either abiraterone or enzalutamide. Best supportive care is allowed in both arms. Stratification factors are prior ARPI use in castration-resistant vs hormone-sensitive prostate cancer settings and pain symptomatology (score 0–3 vs 4–10 on the worst pain intensity item of the Brief Pain Inventory–Short Form). The primary endpoint is rPFS according to PCWG3-modified RECIST v1.1 criteria. Participants with blinded independent centrally confirmed radiographic progression in the ARPI arm can crossover to the 177Lu-PSMA-617 arm. The planned sample size provides 95% power to detect a hazard ratio of 0.56 for rPFS after 156 events with an overall one-sided significance level of 0.025. The key secondary endpoint is OS; other secondary endpoints include safety and tolerability of 177Lu-PSMA-617 and health-related quality of life. Previously presented at the 2021 European Society for Medical Oncology Congress, FPN 942, Morris M et al. Reused with permission. Clinical trial information: NCT04689828.

TALAPRO-1: Talazoparib monotherapy in metastatic castration-resistant prostate cancer (mCRPC) with tumor DNA damage response alterations (DDRm)—Exploration of germline DDR alteration landscape and potential associations with antitumor activity

157

Background: TALAPRO-1 enrolled men with progressive mCRPC with measurable soft-tissue disease and tumor DDRm involved directly or indirectly in homologous recombination repair (HRR) (11 gene panel). These men had received 1–2 taxane chemotherapy and progressed on ≥1 novel hormonal therapy. The primary endpoint was objective response rate ([ORR] per RECIST 1.1; central review). Exploratory ad hoc biomarker analyses assessed germline DDR/HRR (gHRR) alteration landscape and associations with antitumor activity. Methods: Alterations were defined as known/likely pathogenic variants. gHRR alteration (gHRRm) frequency was assessed in the study population evaluable for saliva sequencing (n = 91) using Ambry CustomNext-Cancer (9/11 genes from the tumor panel assessed). Potential associations between gHRRm status and antitumor activity were explored in the HRR-deficient measurable disease population evaluable for gHRRm (n = 70). The potential association of germline vs somatic tumor HRRm and antitumor activity was also assessed in the HRR-deficient measurable disease population (n = 104) using saliva data and somatic-germline-zygosity (SGZ) prediction (when saliva results were unavailable) to annotate tumor alteration origin. This analysis was limited to short variants. Data cutoff was Sept 4, 2020 (primary completion date). Results: Using Ambry saliva results, 19 gHRRm were identified in 18/91 (20%) evaluable patients (pts) ( BRCA2 = 10; ATM = 4; CHEK2 = 4; RAD51C = 1; 1 pt had both ATM and RAD51C). As expected for germline sequencing, all 19 alterations were short variants (12 SNV, 7 InDels). For 17/19 gHRRm, central lab tumor F1CDx records were available: in all 17 cases, identical tumor alterations were found. Of these 17 tumor HRRm, 16 were evaluable for tumor SGZ prediction of origin or zygosity: 15/16 germline, with 1/16 somatic; 9/16 homozygous (incl 7/9 BRCA2), with 7/16 heterozygous (incl 2/9 BRCA2). ORR was 31% (5/16) in men with gHRRm and 26% (14/54) in men without gHRRm ( P = 0.7519, 2-sided Fisher exact test). Based on tumor sequencing results, annotated using saliva results and SGZ predictions, ORR was 25% (10/40) in men with gHRRm and 19% (4/21) in men with only somatic HRRm ( P = 0.7528). Conclusions: Here we report a 20% incidence of gHRRm for this population of men with mCRPC preselected based on tumor HRRm status, which may be impacted by low Ns and assay specific differences in variant calling. In this population, no association with differential antitumor activity was observed with gHRRm status as assessed using germline results alone, or assessed holistically using a combination of tumor and saliva results and SGZ prediction.

BXCL701: First-in-class oral activator of systemic innate immunity combined with pembrolizumab, in patients with metastatic castration-resistant prostate cancer (mCRPC) of adenocarcinoma phenotype—Phase 2a results

125

Background: BXCL701 (talabostat), oral small molecule inhibitor of dipeptidyl peptidases (DPP)—primarily DPP 8/9 & DPP 4—triggers inflammasome to alert and prime immune cells, leading to induction of IL-18 & IL-1ß, bridging innate & adaptive immunity. BXCL701 is evaluated in a phase 1b/2 study in combination with pembrolizumab, in mCRPC patients with adenocarcinoma phenotype (and in small-cell neuroendocrine carcinoma). Most prostate cancers are classified as adenocarcinomas, characterized by expression of androgen receptor (AR) and PSA. The initial results on the phase 2a adenocarcinoma cohort were reported at ESMO 2021. Here are reported the updated safety and efficacy analyses after enrollment of 40 patients for the adenocarcinoma cohort. Methods: Phase 2a patients with adenocarcinoma required to have progression by PCWG3 on 1 or 2 androgen signaling inhibitor and ≥1 prior line of taxane chemotherapy. Patients received pembrolizumab (200 mg IV q21-days) + BXCL701 0.2 mg BID for a week with step-up to 0.3 mg BID on days 8-14, and 0.3 mg BID on days 1-14 of subsequent cycles. Primary endpoint is Composite Response defined as RECIST 1.1 ± PSA50 ± CTC count conversion. Study uses a Simon 2-stage minimax design with 15 evaluable patients in stage 1 and 13 in stage 2. Baseline markers and changes in relevant immune effector cells also evaluated. Results: As of 9/27/21, 40 adenocarcinoma patients were enrolled (26 evaluable, 12 in active treatment). All had previously received taxane chemotherapy and first and/or second generation Androgen Deprivation Treatments and a median of 5 prior lines of therapy (range 1-11); 44% have bone only disease. Median follow-up duration is 12 weeks (range 1-54)/ 4+ cycles. Although follow-up was short, anti-tumor activity was observed. Composite Response rate was 23% (6/ 26 evaluable patients): 2 RECIST-defined confirmed PR + 1 unconfirmed PR (16%) and 63% disease control rate (defined as PR + SD + non-CR/ non-PD) in 19 patients with measurable disease; 16% PSA50 (3 patients had ̃90% PSA decrease) in 31 patients with ≥1 post-baseline PSA measurement; 25% CTC conversion in 8 CTC evaluable patients. All responders showed decrease in tumor burden, 5/ 6 responders were Micro Satellite Stable. BXCL701 + pembrolizumab demonstrated acceptable tolerability without evidence of increased immune-related AEs compared to historic controls with checkpoint inhibitors. AEs consistent with cytokine activation were observed (hypotension, oedema, fever, fatigue). Conclusions: Oral BXCL701 in combination with pembrolizumab demonstrates encouraging anti-tumor activity in very late-line, refractory mCRPC adenocarcinoma. BXCL701 BID dosing continues to demonstrate an acceptable safety profile. Final phase 2a study results will be presented. Clinical trial information: NCT03910660.

PSMAddition: A phase 3 trial to compare treatment with 177Lu-PSMA-617 plus standard of care (SOC) versus SOC alone in patients with metastatic hormone-sensitive prostate cancer

TPS210

Background: [177Lu]Lu-PSMA-617 (177Lu-PSMA-617) is a high-affinity prostate-specific membrane antigen (PSMA)-targeted radioligand therapy that delivers β-particle radiation to PSMA-expressing cells and the surrounding microenvironment. Androgen receptor pathway inhibitors (ARPI) may alter PSMA expression and radiosensitivity. PSMAddition will assess the efficacy and safety of 177Lu-PSMA-617 plus standard of care (SOC) versus SOC alone in adults with metastatic hormone-sensitive prostate cancer (mHSPC). Methods: PSMAddition ( NCT04720157 ) is an international, prospective, open-label, randomized, phase 3 trial in adults with mHSPC. Eligible patients are treatment-naïve or minimally treated candidates for hormonal therapy, with PSMA-positive disease (determined by [68Ga]Ga-PSMA-11 PET/CT), Eastern Cooperative Oncology Group performance status of 0 to 2 and adequate major organ function. Patients are excluded if they have rapidly progressing tumors that require chemotherapy. Approximately 1126 patients will be randomized 1:1 to receive 177Lu-PSMA-617 (7.4 GBq i.v. every 6 weeks, ≤6 cycles) plus SOC or SOC alone (control arm). SOC is ARPI and androgen deprivation therapy. Stratification factors are tumor volume (high/low), age (≥70/ < 70 years) and previous/planned prostatectomy or radiation treatment of the primary prostate tumor (yes/no). The primary endpoint is radiographic progression-free survival (rPFS), as assessed by blinded independent centralized review. Upon centrally confirmed radiographic progression, participants in the control arm can cross over to the 177Lu-PSMA-617 arm. The planned sample size provides 95% power to detect a hazard ratio of 0.7 for rPFS after 418 events with an overall one-sided significance level of 0.025. The key secondary endpoint is overall survival. Other secondary endpoints are the proportion of patients with a prostate-specific antigen (PSA) decline of ≥90% from baseline, time to development of metastatic castration-resistant prostate cancer, composite progression-free survival (radiographic, clinical or PSA progression), safety and tolerability, and health-related quality of life. Previously presented at the 2021 European Society for Medical Oncology Congress, FPN 3035, Tagawa S et al. Reused with permission. Clinical trial information: NCT04720157.

Pembrolizumab (pembro) plus abiraterone acetate (abi) and prednisone (p) in patients with chemotherapy-naive metastatic castration-resistant prostate cancer (mCRPC): Results from KEYNOTE-365 cohort D

118

Background: Abi + p is a standard of care for mCRPC. Cohort D of the phase 1b/2 KEYNOTE-365 study (NCT02861573) was used to evaluate safety and efficacy of the PD-1 inhibitor pembro + abi and p in patients (pts) who had not received chemotherapy for mCRPC. Methods: Chemotherapy-naive pts who had not previously used next-generation hormonal agents (NHAs) for mCRPC or were intolerant to enzalutamide or for whom enzalutamide was ineffective for mCRPC, whose disease progressed ≤6 months before screening, and who had ECOG PS score 0/1 were eligible. Enrolled pts received pembro 200 mg IV Q3W + abi 1000 mg PO QD and p 5 mg PO BID. Primary end points were PSA response rate (PSA decrease ≥50% from baseline), confirmed ORR per RECIST v1.1 by blinded independent central review, and safety. Secondary end points included rPFS per PCWG3-modified RECIST v1.1, DCR (CR + PR + SD or non-CR/non-PD ≥6 mo), DOR, OS, time to symptomatic skeletal-related event, radiographic bone progression, and radiographic soft tissue progression. Results: Of 103 treated pts, 35.9% had RECIST-measurable disease and 26.2% had previously received enzalutamide. Median (range) time from enrollment to data cutoff was 17.6 (9.7-27.0) months. Confirmed PSA response rate in all 103 pts was 56.3%. Overall, 78.6% of pts had a reduction in PSA level from baseline (confirmed and unconfirmed). For 37 pts with RECIST-measurable disease, ORR was 16.2% (1 CR; 5 PRs) overall, 7.7% for those who previously received enzalutamide (n = 13) and 21.7% for those who had not previously received NHAs (n = 23). Two pts with RECIST-nonmeasurable disease had a CR. DOR was not reached (NR; range, 2.1+ to 19.4+ mo); 4 pts had a response ≥12 months. DCR was 44.7% overall, 11.1% in pts who previously received enzalutamide (n = 27), and 57.3% in pts who had not previously used NHAs (n = 75). Additional analyses are listed in the table. Treatment-related AEs (TRAEs) were experienced by 90.3% of pts; 36.9% experienced grade 3-5 TRAEs. Overall, 18.4% of pts had a grade 3/4 ALT laboratory elevation and 12.6% had a grade 3/4 AST elevation. Five pts died of AEs; 1 was treatment-related (myasthenic syndrome). Conclusions: Pembro + abi and p showed antitumor activity in chemotherapy-naive pts with mCRPC. Safety was generally consistent with individual profiles of each agent, although there was an increased incidence of grade 3/4 ALT/AST laboratory elevations than reported for the individual treatments. Clinical trial information: NCT02861573. [Table: see text]

BXCL701: First-in-class oral activator of systemic innate immunity combined with pembrolizumab, in patients with metastatic castration-resistant prostate cancer (mCRPC) of small-cell neuroendocrine carcinoma (SCNC) phenotype—Phase 2a interim results

126

Background: BXCL701 (talabostat), oral small molecule inhibitor of dipeptidyl peptidases (DPP)—primarily DPP 8/9 & DPP 4—triggers inflammasome to alert and prime immune cells, leading to induction of IL-18 & IL-1ß, bridging innate & adaptive immunity. BXCL701 is evaluated in a phase 1b/2 study in combination with pembrolizumab, in mCRPC patients with SCNC phenotype (and in adenocarcinoma). SCNC is highly proliferative and aggressive and does not express androgen receptor or PSA. Here are reported the interim results of the phase 2a after enrollment of 16 patients for the SCNC cohort. Methods: Phase 2a patients with any SCNC histopathological features, either de novo or treatment-emergent including mixed SCNC, required to have progression by PCWG3 on ≥1 prior line of cytotoxic chemotherapy (patients who either have refused chemotherapy or are considered unsuitable for chemotherapy may be eligible following discussion with the sponsor). Patients received pembrolizumab (200 mg IV q21-days) + BXCL701 0.2 mg BID for a week with step-up to 0.3 mg BID on days 8-14, and 0.3 mg BID on days 1-14 of subsequent cycles. Primary endpoint is Composite Response defined as RECIST 1.1 ± PSA50 ± CTC count conversion. Study uses a Simon 2-stage minimax design with 15 evaluable patients in stage 1 and 13 in stage 2. Baseline markers and changes in relevant immune effector cells also evaluated. Results: As of 9/27/21, 16 patients with SCNC were enrolled (10 evaluable, 6 in active treatment): at the 7/08/21 data extract, 9 of the evaluable patients had prior chemotherapy and a median of 2 prior lines of therapy (range 1-4); 33% have bone only disease. Median follow-up duration is 9 weeks (range 1-27)/ 3 cycles. Although follow-up was short, anti-tumor activity was observed. 3/ 10 evaluable patients showed responses—1 RECIST-defined confirmed PR + 1 unconfirmed PR (both 18 weeks/ 6 cycles) + 1 CTC conversion—amounting to a 30% Composite Response rate, meeting protocol-defined expansion criteria from stage 1 to stage 2. BXCL701 + pembrolizumab demonstrated acceptable tolerability without evidence of increased immune-related AEs compared to historic controls with checkpoint inhibitors. AEs consistent with cytokine activation were observed (hypotension, fever, fatigue). Conclusions: Oral BXCL701 in combination with pembrolizumab demonstrates encouraging anti-tumor activity in very late-line, refractory mCRPC SCNC for which there is currently no standard of care. BXCL701 BID dosing continues to demonstrate an acceptable safety profile. Additional interim phase 2a study results will be presented. Clinical trial information: NCT03910660.

A Wolf in Sheep's Clothing: Systemic Immune Activation Post Immunotherapy

Introduction

Immune checkpoint inhibitors (ICIs) are increasingly a standard of care for many cancers; these agents can result in immune-related adverse events (irAEs) including fever, which is common but can rarely be associated with systemic immune activation (SIA or acquired HLH).

Methods

All consecutive patients receiving ICIs in the Drug Development Unit of the Royal Marsden Hospital between May 2014 and November 2019 were retrospectively reviewed. Patients with fever ≥ 38°C or chills/rigors (without fever) ≤ 6 weeks of commencing ICIs were identified for clinical data collection.

Results

Three patients met diagnostic criteria for SIA/HLH with median time to onset of symptoms of 10 days. We describe the clinical evolution, treatment used, and outcomes for these patients. High-dose steroids are used first-line with other treatments, such as tocilizumab, immunoglobulin and therapeutic plasmapheresis can be considered for steroid-refractory SIA/HLH.

Conclusion

SIA/HLH post ICI is a rare but a potentially fatal irAE that presents with fever and a constellation of nonspecific symptoms. Early recognition and timely treatment are key to improving outcomes.

Abstract CT019: A phase I trial of the combination of the dual RAF-MEK inhibitor VS-6766 and the FAK inhibitor defactinib: Evaluation of efficacy in KRAS mutated NSCLC

Background

KRAS is a known oncogenic driver in non-small cell lung cancer (NSCLC), with KRAS G12C and G12V mutations occurring in ~13% and ~7% of the of NSCLC ( adenocarcinoma subtype). The dual RAF-MEK inhibitor VS-6766 has shown single agent activity against G12V KRAS mutated NSCLC (Guo C et al Lancet Oncology 2020, 21:1478-88). Based on pre-clinical data, we hypothesised that augmented focal adhesion kinase (FAK) signalling is a mechanism of resistance to MEK inhibition and devised the current clinical trial. We have previously reported the safety of an intermittent schedule of the combination of VS-6766 and the FAK inhibitor defactinib and its efficacy in low grade serous ovarian cancer (Shinde et al., AACR 2020). We now report the activity of the combination in KRAS mutated NSCLC.

Methods

Patients were treated with an intermittent dose of drugs VS-6766 at 3.2 - 4 mg twice a week and defactinib 200 mg twice daily in the dose escalation and expansion cohorts of the study. Both drugs were administered three weeks on/one week off in 28-day cycles. We aim to recruit 20 patients with KRAS mutated NSCLC in an expansion cohort.

Results

To date, 19 patients with KRAS mutated NSCLC have been treated in the dose escalation and expansion cohorts. All patients had been previously treatment with a PD-1 or PDL-1 targeting immune checkpoint inhibitor. The median age was 64 years (22 - 73), M/F ratio was 7/12, and the median prior lines of treatment was 3. Currently, 17 of 19 patients have had at least one re-staging assessment, 2/17 (12%) patients had a partial response and 10/17 (59%) had stable disease as their best response. Of note, 11/17 (65%) patients had a degree of reduction in size of their tumours and 5/17 (29%) have been treated for 6 months or more with 3 patients still on treatment. Interestingly, 2/2 (100%) of the KRAS G12V NSCLC patients showed a partial response.

Conclusions

Developing new treatments for non-G12C KRAS mutated NSCLC is an area of unmet need. The combination of VS-6766 and defactinib treatment in cohorts of patients with NSCLC pre-treated with chemotherapy and immunotherapy has shown anti-tumour activity in subsets of patients with KRAS mutated NSCLC, in particular those with tumours harbouring KRAS G12V mutations. A registration-directed study evaluating VS-6766 ± defactinib for treatment of recurrent NSCLC with KRAS G12V mutation (NCT04620330) has been initiated

Citation Format: Matthew G. Krebs, Rajiv Shinde, Rozana Abdul Rahman, Rafael Grochot, Martin Little, Jenny King, Joseph Kitchin, Mona Parmar, Alison Turner, Muneeb Mahmud, Christina Yap, Nina Tunariu, Juanita Lopez, Johann S. De Bono, Udai Banerji, Anna Minchom. A phase I trial of the combination of the dual RAF-MEK inhibitor VS-6766 and the FAK inhibitor defactinib: Evaluation of efficacy in KRAS mutated NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT019.

Results of an ongoing phase 1/2a dose escalation study of HPN424, a tri-specific half-life extended PSMA-targeting T-cell engager, in patients with metastatic castration-resistant prostate cancer (mCRPC)

5013

Background: HPN424 is a prostate-specific membrane antigen (PSMA)-targeting T cell engager designed to redirect T cells to kill PSMA-expressing prostate cancer cells; engineered with three binding domains: anti-PSMA for tumor cell engagement, anti-albumin for half-life extension and anti-CD3 for T cell engagement. HPN424 is optimized for small size and increased stability compared to other bispecific platforms. Methods: This Ph1/2a study is evaluating HPN424 in mCRPC patients (pts) who have received > 2 prior systemic therapies. Primary endpoints are safety, tolerability and determination of MTD/RP2D. Secondary objectives are pharmacokinetics (PK), pharmacodynamics, immunogenicity and preliminary anti-tumor activity. HPN424 is administered IV once weekly. Tumor assessments include PSA, CT and bone scans every 9-weeks. Results: As of 2/8/21, 80 pts were dosed in 15 cohorts with target doses ranging from 1.3 to 160ng/kg fixed dose, and up to 300ng/kg with step dosing to the target dose after initial priming dose. Pts had received a median of 6 prior systemic regimens, 75% received prior chemotherapy for mCRPC. Median age was 70 (43 – 91). Most common grade > 3 TEAEs were AST increase (18%), anemia (11%) and ALT increase (11%). DLTs include CRS G3 (n = 3), elevated lipase G3 (n = 1) and seizure G3 (n = 1). These events did not limit escalation, MTD has not been reached and escalation continues. All grade CRS occurred in 63% of pts, 4% grade 3 per ASTCT and no Grade 4/5 CRS. CRS G3 events occurred after first administration of target dose (n = 2 fixed dose, n = 1 step dose). Transaminase elevation occurred predominantly during Cycle 1, was transient and had no clinical sequelae. Disease progression was the primary reason for drug discontinuation; 2 pts (3%) discontinued due to TRAE. Reduction in circulating tumor cells (CTC) was seen in 32 of 56 pts (57%) with measurable CTC at baseline. Fifteen of 62 pts (24%) with > 24 weeks follow-up remained on treatment ≥ 24 weeks. Thirteen of 63 pts (21%) with post-baseline levels had PSA declines from baseline, including 3 PSA50, 2 PSA30 responses. In chemo-naïve pts, 5 of 15 (33%) showed PSA declines post-baseline. In the highest fixed dose cohort (160ng/kg) tested to-date, 3 of 7 evaluable pts had PSA declines from baseline and 1 had a confirmed partial response per RECIST. Conclusions: HPN424, a novel half-life extended PSMA-targeting T cell engager, was well tolerated when administered once weekly. AEs were transient, manageable and consistent with class of agent. Grade 3 CRS was observed in 4% of patients, occurring with first administration of target dose. Evidence of antitumor activity included PSA and CTC reductions and treatment duration > 24 weeks in 15/62 pts. Encouraging signals were seen at the highest fixed dose cohort including a confirmed RECIST partial response. NCT03577028 Clinical trial information: NCT03577028.

A first-in-human phase I study of ATR inhibitor M1774 in patients with solid tumors

TPS3153

Background: Ataxia telangiectasia and Rad3-related (ATR) protein kinase plays a critical role in the DNA damage response by sensing and responding to DNA replication stress, and by inducing cell cycle arrest to prevent aberrant replication and mitotic catastrophe. Based on extensive preclinical and limited clinical evidence, ATR inhibition is a promising treatment strategy as monotherapy for patients with advanced tumors harboring synthetically lethal conditions, such as alternative lengthening of telomeres (ALT) and inactivating mutations in ARID1A and ATM. M1774 is a potent, selective, orally administered ATR inhibitor that has been shown to exert antitumor activity in patient-derived xenograft tumors and acute myeloid leukemia xenograft tumors that express the ATR inhibition sensitizing mixed lineage leukemia fusion protein. This study (NCT04170153) aims to evaluate the safety and tolerability, maximum tolerated dose, recommended dose for expansion (RDE) and pharmacokinetics (PK) of M1774 (part A1), the effect of food on M1774 PK (part A2), and the efficacy of M1774 in patients with tumors harboring selected mutations (part A3). An additional objective is to assess the pharmacodynamics of M1774 by measuring relative changes in baseline p-CHK1 and γ-H2AX expression in paired tumor biopsies and serial blood samples. Methods: Patients aged ≥18 years, with an Eastern Cooperative Oncology Group performance status ≤1, adequate baseline hematological, renal and hepatic function, and with locally advanced or metastatic disease refractory to standard therapy are eligible. Patients with tumors bearing loss-of-function (LoF) mutations (determined by site testing or a central trial assay) in ARID1A, ATM, or ATRX and/or DAXX as ALT status surrogate markers; and measurable disease according to Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1, will be enrolled in part A3. In the dose escalation phase (part A1 [open]), 18–24 patients are due to receive M1774 at a starting dose of 5 mg once daily. Dose escalation is determined by the safety monitoring committee and guided by a Bayesian 2-parameter logistic regression model. The preliminary food assessment (part A2) will follow a randomized two-sequence two-period crossover design in which ≤12 patients will be randomized (1:1) to receive a single dose of M1774 on Day –7 at the RDE (determined in part A1) in either a fed or fasted condition. After the food assessment, patients will subsequently receive M1774 according to the part A1 dosing schedule. In the preliminary efficacy study (part A3), patients (n = 20–24 for each of the three planned cohorts) with tumors harboring LoF mutations in the genes for ARID1A, ATM, ATRX and/or DAXX, will receive M1774 at the RDE. The primary efficacy endpoint is overall response (RECIST). The study is open and currently recruiting. Patients have been enrolled to seven cohorts in part A1 with no DLTs observed; dose escalation is ongoing. Clinical trial information: NCT04170153.

Phase III study of lutetium-177-PSMA-617 in patients with metastatic castration-resistant prostate cancer (VISION)

LBA4

Background: Despite recent therapeutic advances, metastatic castration-resistant prostate cancer (mCRPC) remains invariably fatal. Prostate-specific membrane antigen (PSMA) is highly expressed in mCRPC lesions. 177Lu-PSMA-617 is a targeted radioligand therapy that delivers ß-particle radiation to PSMA-expressing cells and surrounding microenvironment. Method: VISION was an international, randomized, open-label phase III study evaluating 177Lu-PSMA-617 in men with PSMA-positive mCRPC previously treated with next-generation androgen receptor signaling inhibition and 1–2 taxane regimens. PSMA positivity (threshold greater than liver) was determined by central review of 68Ga-PSMA-11 scans. Patients were randomized 2:1 to 177Lu-PSMA-617 (7.4 GBq every 6 weeks x 6 cycles) plus standard of care (SOC) versus SOC alone. SOC was investigator determined but excluded cytotoxic chemotherapy and radium-223. The alternate primary endpoints were radiographic progression-free survival (rPFS) using PCWG3 criteria by independent central review (ICR) and overall survival (OS). Under the null hypothesis, median rPFS was assumed to be 4 months and OS 10 months for 177Lu-PSMA-617 + SOC for a hazard ratio (HR) of 1.00. Under the alternative hypothesis, median rPFS was assumed to be 6 months for a HR of 0.67 and median OS was assumed to be 13.7 months for a HR of 0.7306. Key secondary endpoints were objective response rate (ORR; RECIST v1.1), disease control rate (DCR), and time to first symptomatic skeletal event (SSE). Results: Between 4 June 2018 and 23 October 2019, 831 of 1179 screened patients were randomized 2:1 to receive 177Lu-PSMA-617 + SOC (n = 551) or SOC only (n = 280). Median study follow-up was 20.9 months at the data cut-off (27 January 2021). Treatment groups were balanced in terms of demographics and baseline characteristics. 177Lu-PSMA-617 + SOC significantly improved rPFS versus SOC alone (median rPFS, 8.7 vs 3.4 months; HR, 0.40 [99.2% CI: 0.29, 0.57]; p < 0.001, one-sided). The alternate primary endpoint of OS was also significantly improved versus SOC alone (median OS, 15.3 vs 11.3 months; HR, 0.62 [95% CI: 0.52, 0.74]; p < 0.001, one-sided). All key secondary endpoints were statistically significant between the treatment arms in favor of 177Lu-PSMA-617 + SOC, including ICR-determined ORR (29.8% vs 1.7%), ICR-determined DCR (89.0% vs 66.7%) and time to first SSE (median time, 11.5 vs 6.8 months; HR, 0.50). While a higher rate of high-grade treatment-emergent adverse events was observed with 177Lu-PSMA-617 (52.7% vs 38.0%), therapy was well tolerated. Conclusions: 177Lu-PSMA-617 plus SOC treatment is a well-tolerated regimen that improves rPFS and prolongs OS compared with SOC alone in men with advanced-stage PSMA-positive mCRPC, supporting its adoption as a standard of care. Clinical trial information: NCT03511664.

Safety and efficacy of AMG 160, a half-life extended BiTE immune therapy targeting prostate-specific membrane antigen (PSMA), and other therapies for metastatic castration-resistant prostate cancer (mCRPC)

TPS5088

Background: Lesions in mCRPC are typically immunologically cold. AMG 160 binds to PSMA on cancer cells and CD3 on T cells, leading to T-cell infiltration, activation, expansion, and tumor cell killing. In a first-in-human study, AMG 160 has demonstrated a manageable safety profile with preliminary efficacy in heavily pretreated patients. Enzalutamide and abiraterone are novel hormonal therapies (NHTs) that improve survival in mCRPC and may enhance T-cell responses, but resistance occurs. Combination therapy with AMG 160 may help overcome hormonal therapy resistance and broaden use for earlier line mCRPC. Preclinical data have demonstrated enhanced activity when AMG 404, an anti-PD-1 that can overcome T-cell exhaustion, and AMG 160 are combined. The safety and efficacy of AMG 160 combinations will be evaluated. Methods: NCT04631601 will enroll ∼100 men with histologically or cytologically confirmed adenocarcinoma of the prostate. The protocol consists of 3 subprotocols. Subprotocols A and B are phase 1b, multicenter, open-label studies; subprotocol C is a phase 1b/2 study. Therapeutic combinations include AMG 160 + enzalutamide (A), AMG 160 + abiraterone (B), and AMG 160 + AMG 404 vs AMG 404 monotherapy (C). Patients who received prior PSMA radionuclide therapy may be eligible. Patients must not have received prior PSMAxCD3 bispecific therapy, prior taxane treatment (unless approved by the sponsor) across subprotocols, and prior NHT specific to the subprotocol. In subprotocol C, patients must have progressive disease on an NHT to be eligible. Patients with CNS metastases, leptomeningeal disease, or active autoimmune disease will be excluded. AMG 160 will be administered intravenously (IV). Dexamethasone (or other corticosteroids) will be administered before AMG 160 administration in cycle 1 and possibly subsequent cycles. Enzalutamide or abiraterone will be administered per label. AMG 404 will be administered IV. Primary objectives are to evaluate safety and tolerability and determine the maximum tolerated dose (MTD) or recommended phase 2 dose (RP2D) of AMG 160 combinations. Subprotocol C will also evaluate the preliminary antitumor activity of AMG 404 monotherapy. Secondary objectives are to assess preliminary antitumor activity and characterize pharmacokinetics. MTD/RP2D will be established in the dose-escalation phase, and the safety and tolerability of the MTD/RP2D will be confirmed in the expansion phase. Evaluation of preliminary antitumor activity will be based on RECIST 1.1 with Prostate Cancer Working Group 3 modifications, prostate-specific antigen (PSA) response, circulating tumor cell response, progression-free survival (radiographic, PSA, clinical), overall survival, and 68Ga-PSMA-11 and 18F-FDG PET/CT imaging. The study is currently recruiting patients. Clinical trial information: NCT04631601.

Talazoparib (TALA), an oral poly (ADP-ribose) polymerase (PARP) inhibitor for men with metastatic castration-resistant prostate cancer (mCRPC) and DNA damage response (DDR) alterations: Detailed safety analyses from TALAPRO-1 trial

5047

Background: PARP inhibitors have recently been approved for the treatment of mCRPC. In this Phase 2 study, we explore the safety profile of TALA in men with mCRPC with the aim of understanding how patients (pts) with adverse events (AEs) were managed during the trial. Methods: TALAPRO-1 (NCT03148795) is a single-arm, open-label, phase 2 study of TALA in pts with progressive mCRPC, measurable soft tissue disease, and DDRm likely to sensitize to PARPi ( ATM, ATR, BRCA1/2, CHEK2, FANCA, MLH1, MRE11A, NBN, PALB2, RAD51C), who received ≥1 taxane-based chemotherapy and progressed on ≥1 novel hormonal therapy (enzalutamide/abiraterone). The primary objective was confirmed objective response by central independent review; the assessment of safety included AEs, incidence of dose modifications and of permanent treatment discontinuation due to AEs, and clinical laboratory tests. Results: In the TALA-treated population (1 mg/daily; n=127), 95.3% (121/127) experienced all-causality AEs. The most common (≥15%) hematologic AEs were anemia (any grade, 48.8%; G3, 30.7% [no G4 events]), thrombocytopenia (all grade, 18.9%; G3/4, 8.7%), and neutropenia (all grade, 16.5%, G3, 7.9% [no G4]). Median time from first dose of TALA to onset of first episode of G≥3 anemia, neutropenia, and thrombocytopenia was 56, 48, and 17 days, respectively. G3 anemia lasted a median of 7 days, G3 neutropenia lasted a median of 12 days, G3 and G4 thrombocytopenia lasted a median of 8 and 11 days, respectively. Hematologic AEs typically occurred during the first 4–5 months of TALA treatment and were managed by dose modifications and supportive care. 34.6% of pts received a blood transfusion product, and most transfusions occurred when hemoglobin was between 7.0–10.0 g/dL. Overlapping G3/4 hematologic AEs were infrequent on TALA (anemia + neutropenia 4.7%; anemia + thrombocytopenia 5.5%; neutropenia + thrombocytopenia 1.6%). In pts who had anemia, 12.6% also had fatigue; in those with thrombocytopenia, 4.7% had a subsequent bleeding event; in those with neutropenia, 1.6% had an overlapping infection. The most common non-hematologic AEs (≥15%) were nausea (any grade, 33.1%; G3/4, 2.4%), decreased appetite (any grade, 28.3%; G3/4, 3.1%), and asthenia/fatigue (any grade, 23.6%/19.7%; G3/4, 3.9%/1.6%). In the treated population, dose reduction of TALA due to all-causality AE occurred in 33 pts (26.0%). Treatment discontinuation due to all-causality AEs was low and occurred in 15 pts (11.8%); the most frequent (≥2 pts) AEs leading to discontinuation of TALA were back pain and platelet count decrease (each, 1.6% [2/127 pts]). There were no treatment-related deaths. Conclusions: A manageable safety profile and durable antitumor effects were observed with TALA in men with heavily pretreated mCRPC in this phase 2 study. Clinical trial information: NCT03148795.

Pembrolizumab plus enzalutamide for enzalutamide-resistant metastatic castration-resistant prostate cancer (mCRPC): Updated analyses after one additional year of follow-up from cohorts 4 and 5 of the KEYNOTE-199 study

5042

Background: KEYNOTE-199 (NCT02787005) is a multicohort phase 2 study to evaluate pembrolizumab (pembro) in mCRPC. A previous analysis of patients with RECIST-measurable (cohort 4 [C4]) or bone-predominant nonmeasurable (cohort 5 [C5]) disease who were chemotherapy-naive and had progression while on enzalutamide (enza) found that pembro + enza showed antitumor activity and manageable safety. Long-term outcomes are of interest with immunotherapy; hence, updated efficacy and safety data after an additional 1 year of follow-up are presented. Methods: Pts were eligible if they had resistance to enza after prior response. Prior treatment with abiraterone was allowed. Pts received pembro 200 mg Q3W for up to 35 cycles + enza QD until progression, unacceptable toxicity, or withdrawal. Primary end point was ORR per RECIST v1.1 by blinded independent central review (BICR) in C4. Secondary end points were DOR (C4), and DCR, rPFS, OS and safety (both cohorts). Results: 126 pts (C4, 81; C5, 45) were treated. Median age was 72 years (range 43-92), 32.5% had visceral disease and 87.3% previously received ≥6 mo of enzalutamide; 121 pts (96.0%) discontinued, most because of progressive disease. Median (range) time from enrollment to data cutoff was 31.7 mo (23.1-37.1) in C4 and 35.5 mo (22.9-37.3) in C5. In C4, confirmed ORR was 12.3% (95% CI 6.1-21.5) (2 CRs, 8 PRs); median (range) DOR was 8.1 mo (2.5+ to 15.2), and 62.5% had a response ≥6 mo (Kaplan-Meier estimate). Additional efficacy analyses are outlined in the table. A total of 27.2% and 28.9% of pts in C4 and C5, respectively, experienced grade ≥3 treatment-related adverse events. Two pts in C4 died of immune-related AEs (Miller Fisher syndrome and myasthenia gravis). Incidence of any-grade (34.1%) and grade 3 or 4 (5.6%) rash, regardless of relatedness to treatment, was higher than previously reported for individual agents but manageable with standard-of-care treatments; 2 pts discontinued because of rash. Conclusions: After an additional 1 year of follow-up, pembro + enza continued to show antitumor activity and a manageable safety profile in pts with mCRPC who became resistant to enza. The treatment combination is being further evaluated in the ongoing phase 3 KEYNOTE-641 trial (NCT03834493). Clinical trial information: NCT02787005. [Table: see text]

Phase 1 trial of the adenosine A2A receptor antagonist inupadenant (EOS-850): Update on tolerability, and antitumor activity potentially associated with the expression of the A2A receptor within the tumor

2562

Background: Tumors produce high levels of extracellular adenosine which suppress anti-tumor immune responses. Blocking A2A receptors, predominantly expressed on tumor-infiltrating immune cells, can reverse the immunosuppressive effect of adenosine. Inupadenant is a non brain-penetrant, potent and highly selective small molecule antagonist of the A2A receptor that remains active even at the high adenosine concentrations found in tumors. Methods: This is the phase I portion of an ongoing first-in-human, clinical trial (NCT02740985) to evaluate safety/tolerability, pharmacokinetic, pharmacodynamic and anti-tumor activity of inupadenant in adult patients with solid tumors who have exhausted standard treatment options. In addition, tumor biomarkers, including adenosine-pathway markers by immunohistochemistry (IHC), are being evaluated. We present updated results of the dose escalation, new results from the monotherapy expansion and new analysis of tumor biomarkers. Results: Overall, 42 patients (21 patients in the dose escalation and an additional 21 patients in a monotherapy expansion) with a median of 3 prior regimens were treated as of the data cut off (DCO, 30Nov20).The dose levels investigated, along with the most frequent (>20%) treatment-emergent adverse events (TEAEs) across all dose levels are presented in the table. 7 AEs led to discontinuation; 2 (atrial fibrillation and myocardial infarction) were considered possibly study drug-related by the investigator. No dose reductions were required. Two partial responses (PRs) were reported: melanoma (NRAS-mutant; received prior immunotherapy), and prostate cancer (received antiandrogen and chemotherapy). At the DCO, both PRs were ongoing with a duration of response >230 days. 12 patients had stable disease (SD) as best response and SD >6 months was observed in 3 patients. Response and stable disease were associated with a higher number of cells expressing the A2A receptor within the tumor at baseline, as measured by IHC. Conclusions: Inupadenant monotherapy was generally well-tolerated as of the DCO at a dose of 80 mg twice daily with initial evidence of clinical benefit, including 2 durable PRs in patients who have exhausted standard treatment options. Analysis of pre-treatment tumor biopsies has identified the A2A receptor as a biomarker which may be associated with clinical benefit. Clinical trial information: NCT03873883. [Table: see text]

Preliminary clinical and biologic results of GB1275, a first-in-class oral CD11b modulator, alone and with pembrolizumab, in advanced solid tumors (KEYNOTE A36)

2505

Background: GB1275 is a first-in-class, oral CD11b modulator that reduced myeloid-derived suppressor cells (MDSCs) and tumor associated macrophages (TAMs), repolarized M2 immunosuppressive TAMs to an M1 phenotype, resulting in increased tumor infiltration of activated CD8+ T cells and antitumor efficacy in preclinical models. Here, we report preliminary results from an ongoing, first-in-human dose-escalation study in specific advanced tumors using GB1275 alone or with pembrolizumab. (NCT04060342) Methods: Phase 1 comprises dose escalation and expansion. During dose escalation, cohorts of 3 to 6 subjects were sequentially assigned to ascending dose levels of GB1275 from 100 mg to 1200 mg BID in one of two dosing regimens: Regimen A [GB1275 monotherapy orally (PO) twice a day (BID)] and Regimen B [GB1275 PO BID plus pembrolizumab 200 mg IV every 3 weeks (q3wks)]. Dose escalation was based on safety including dose-limiting toxicities (DLTs). Following dose escalation, up to 40 subjects with specific tumor types are to be treated in expansion with the selected GB1275 dose plus pembrolizumab to assess safety, pharmacokinetics, and preliminary clinical and biomarker activity. Results: As of January 8, 2021, 45 subjects were treated [44 in dose escalation: 23, Regimen A; 21, Regimen B. 1 in expansion, Regimen B], with median (range) GB1275 exposure of 42.0 days (4-263). No DLTs were reported. GB1275-related adverse events occurred in 24/45 (53.3%) subjects; photosensitivity reaction (20.0%), dysesthesia (13.3%) and pruritus (13.3%) were most frequent (≥10%). Stable disease was reported in 6/19 (31.6%) response-evaluable subjects in Regimen A and 9/16 (56.3%) in Regimen B. In Regimen B (800 mg), one partial response was reported in a subject with MSS-CRC treated for 263 days, and one prolonged stable disease (227 days) was reported in a gastric cancer (GC) subject previously treated with pembrolizumab plus bavituximab for less than 3 months due to progression; both subjects are continuing study treatment. A dose-dependent increase in GB1275 systemic exposure was observed up to 800 mg BID. Down-regulation of peripheral MDSCs was seen with both regimens. Regimen-dependent gene clusters in whole blood were noted. An increase in tumor infiltrating lymphocyte (TIL) counts was noted in both Regimens A and B. Conclusions: Dose escalation of GB1275, up to 1200 mg in Regimens A and B, demonstrated tolerability as monotherapy and combined with pembrolizumab in subjects with advanced cancers. Encouraging antitumor activity in Regimen B (800 mg) was observed in subjects with MSS-CRC and GC. Biological activity reflected by MDSC modulations in blood and TIL Increases in tumor biopsies with GB1275 alone and with pembrolizumab supports the mechanism of GB1275. GB1275 800 mg BID plus pembrolizumab 200 mg IV q3wks was selected for evaluation in the expansion phase. Clinical trial information: NCT04060342.

First-in-human study of TAS3681, an oral androgen receptor (AR) antagonist with AR and AR splice variant (AR-SV) downregulation activity, in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) refractory to abiraterone (ABI) and/or enzalutamide (ENZ) and chemotherapy (CT)

5031

Background: Second-generation AR signaling inhibitors have improved outcomes from mCRPC; drug resistance, however, invariably evolves with AR overexpression, AR mutation, or AR-SVs and continued AR signaling. TAS3681 is an oral and selective AR antagonist with AR and AR-SV down-regulation and has antitumor efficacy in AR-SV+, ENZ-resistant CRPC models. We report the dose escalation part of the first-in-human trial of TAS3681 in pts with mCRPC (NCT02566772). Methods: mCRPC pts with progressing disease after ABI and/or ENZ, and ≥1 additional CT, received TAS3681 in a 3+3 dose escalation design; QD or BID tablets were given in 28-day cycles; BID dosing at ≤600 mg was introduced to increase daily exposure while limiting Cmax. Primary endpoints: incidence of dose limiting toxicities (DLTs) and adverse events (AEs); other endpoints: pharmacokinetics (PK), and antitumor activity per Prostate Cancer Clinical Trials Working Group 3 (PCWG3). Results: As of January 22, 2021, 56 pts in 10 cohorts were dosed (QD: 25, 50, 100, 200, 400, 600, 800, and 1000 mg; and BID: 300 and 400 mg). Median age was 66 (56–79) yrs; pts had a median of 6 prior lines of systemic therapy. Of 41 pts evaluable for DLTs, 3 had confirmed DLTs: 1/10 DLT evaluable pts at 600 mg QD (QT prolongation >480 ms) and 2/3 DLT evaluable pts at 400 mg BID (1 pt with QT prolongation >480 ms, 1 pt with G3 hypertension). The most common treatment-related AEs (TRAEs) were: nausea (32 pts, 57.1%), hyperbilirubinemia (21 pts, 37.5%), fatigue (18 pts, 32.1%), vomiting (17 pts, 30.4%) and diarrhea (16 pts, 28.6%); AEs of QT prolongation were seen in 11 pts (19.6%). TRAEs ≥G3 were reported in 12 pts (21.4%). TAS3681 exposure increased dose-dependently up to 600 mg QD and then plateaued. Steady state was reached by Day 8 and accumulation ratios of AUC were approximately 2 to 6 times. Confirmed PSA declines of >50% from baseline were seen in the 600 mg QD (2 pts) and 300 mg BID cohorts (1 pt). Antitumor activity was observed; tumor response rate was 23.1% in the 600 mg QD cohort (3 confirmed partial responses (cPRs) in 13 dosed pts), 22.2% in the 300 mg BID cohort (1 cPR and 1 unconfirmed complete response in 9 dosed pts), and 14.3% in the 400 mg BID cohort (cPR in 1/7 dosed pts). Responses occurred after 2–4 cycles of treatment. The longest duration of response (DoR) to date is 16.2 mo. The 5 pts with cPR had DoR >6 mo with the exception of 1 pt who had a short follow-up period. 300 mg BID was found to be the best tolerated dose with antitumor activity. Conclusions: The recommended phase 2 dose is 300 mg BID. TAS3681 has a manageable safety profile and has antitumor activity against heavily pretreated, multi-drug resistant mCRPC. The study expansion phase is enrolling pts who have progressed on ABI or ENZ +/- taxane CT. Clinical trial information: NCT02566772.

Exploratory gene-by-gene analysis of olaparib in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC): PROfound

126

Background: The Phase 3 PROfound trial (NCT02987543) met its primary endpoint and key secondary endpoints, including improved overall survival (OS) for olaparib in men with mCRPC with alterations in BRCA1, BRCA2, or ATM (Cohort A). We report gene-by-gene analysis of olaparib antitumor activity among the 15 prespecified homologous recombination repair (HRR) genes. Methods: Pts were randomized to olaparib (300 mg bid; n=256) or physician’s choice of enzalutamide or abiraterone (control; n=131). Exploratory analyses in pts with alterations in BRCA1 and/or BRCA2 (BRCA, regardless of co-occurring alterations with other HRR genes) or in single genes were conducted. Results: Evidence of olaparib antitumor activity was observed in subgroups with >10 pts (table). Data for pts with alterations in only BRCA1, BRCA2, PPP2R2A, RAD51B, RAD54L, PALB2, BRIP1, CHEK1, BARD1, and RAD51D will be reported (no FANCL or RAD51C enrolled). Conclusions: Small subgroups limit interpretation for some genes. Olaparib antitumor activity is greatest in pts with BRCA alterations, with a spectrum of clinical sensitivity to olaparib as defined by rPFS and OS across the broader population with alterations in other HRR genes. Clinical trial information: NCT02987543. [Table: see text]

Olaparib efficacy in patients with metastatic castration-resistant prostate cancer (mCRPC) carrying circulating tumor (ct) DNA alterations in BRCA1, BRCA2 or ATM: Results from the PROfound study

27

Background: ctDNA testing offers additional opportunities for homologous recombination repair (HRR) gene alteration determination in patients who are not able to access tumor tissue testing. Alteration testing in ctDNA, for BRCA1, BRCA2 and ATM alterations was performed retrospectively in the PROfound study (phase 3 trial of olaparib versus physician’s choice of abiraterone or enzalutamide in men with HRR gene-mutated mCRPC [NCT02987543]). Methods: ctDNA samples were sequenced at FMI, using the FoundationOne Liquid CDx assay for alterations in BRCA1, BRCA2 (BRCA) and ATM, using plasma samples collected during screening in PROfound. Only patients who consented and provided plasma samples from Cohort A (BRCA/ ATM alteration positive by tissue testing) were tested for ctDNA alterations. Radiographic progression-free survival (rPFS) assessed by blinded independent central review (BICR) in patients positive for alterations in ctDNA was analysed via stratified log-rank test. Additional efficacy endpoints (Objective Response Rate [ORR], Overall Survival[OS]) were also assessed. Results: In total, 181/245 (73.9%) Cohort A patients consented and provided a plasma sample for ctDNA testing, of which 139/181 (76.8%) had a ctDNA result reported (either mutation positive or mutation negative) and 42 patient samples failed testing due to insufficient DNA yield or a technical failure of the test.BRCA/ ATM alterations were identified in111/139 (79.9%) patients and 28/139 patients did not report a BRCA/ATM mutation either due to lack of ctDNA shedding from the tumour or ctDNA levels below the sensitivity of the assay. Patients who carried BRCA/ ATM ctDNA alterations had comparable demography, baseline characteristics and proportions of BRCA1, BRCA2 and ATM mutated patients to the overall Cohort A patients. rPFS by BICR results, in patients with BRCA/ ATM alterations in ctDNA, are presented in the Table. Key secondary efficacy endpoints (ORR, OS) will also be reported for ctDNA alteration positive patients. Conclusions: ctDNA testing in patients with mCRPC is feasible and most, but not all patients have concordant results. Patients who were positive for alterations in BRCA1, BRCA2 or ATM showed a consistent rPFS improvement (hazard ratio [HR] 0.33 [0.21, 0.53]) when compared with the ITT population identified by tumor tissue testing (HR 0.34 [0.25, 0.47]). This suggests that using ctDNA to identify patients carrying BRCA1, BRCA2 or ATM alterations who will benefit from olaparib may be beneficial. Clinical trial information: NCT02987543. [Table: see text]

TALAPRO-1: Phase II study of talazoparib (TALA) in patients (pts) with DNA damage repair alterations (DDRm) and metastatic castration-resistant prostate cancer (mCRPC)

93

Background: Poly(ADP-ribose) polymerase (PARP) inhibitors (PARPi) show antitumor activity in mCRPC/DDRm pts treated with novel hormonal therapy (NHT). TALAPRO-1 is an open-label study evaluating TALA (a potent PARP inhibitor/trapper) in men with mCRPC/DDRm. We report a planned interim analysis (IA; Dec 2019). Updated results at a Sep 4 2020 cut-off, available in November 2020, will be presented at the meeting. Methods: TALAPRO-1 (NCT03148795) is enrolling pts (N ≈ 100) with measurable soft tissue disease, progressive mCRPC, and DDRm likely to sensitize to PARPi ( ATM, ATR, BRCA1/2, CHEK2, FANCA, MLH1, MRE11A, NBN, PALB2, RAD51C), who received 1–2 chemotherapy regimens (≥1 taxane-based) for metastatic disease and progressed on ≥1 NHT (enzalutamide/abiraterone acetate) given for mCRPC. DDRm are defined as known/likely pathogenic variants or homozygous deletions. Pts receive oral TALA 1 mg/day (moderate renal impairment 0.75 mg/day) until radiographic progression, unacceptable toxicity, consent withdrawal, or death. Primary endpoint is objective response rate (ORR). Secondary endpoints: time to objective response; response duration; prostate-specific antigen (PSA) decrease ≥50%; circulating tumor cell (CTC) count conversion (to CTC = 0 and <5 per 7.5 mL blood); time to PSA progression; radiographic progression-free survival (rPFS); overall survival; safety. A planned efficacy/safety IA was done when 60 pts with DDRm and measurable disease completed ≥6 months of TALA/no longer followed. Radiographic responses are based on investigator assessments. Results: 113 pts received TALA (cut-off Dec 12 2019); 75 pts were evaluable for IA, with DDRm, had measurable disease, received ≥16 weeks’ treatment, and were assessed for ORR (54.7% BRCA1/2, 4.0% PALB2, 22.7% ATM; 18.7% other DDRm).All pts evaluable for IA had prior docetaxel; 45.3% cabazitaxel. Confirmed ORR, rPFS, and composite response (investigator-assessed) in pts who received TALA for ≥16 weeks are in the table. Most common treatment-emergent adverse events: anemia (42.5%); nausea (32.7%). Conclusions: TALA monotherapy has encouraging antitumor activity in docetaxel-pretreated mCRPC pts with BRCA1/2 alterations and was generally well tolerated. Funding: Pfizer Inc. Clinical trial information: NCT03148795. [Table: see text]

Putative biomarkers of response to anti-PD-1 therapy in metastatic castration-resistant prostate cancer (mCRPC)

155

Background: Metastatic castration resistant prostate cancer (mCRPC) is a heterogeneous disease in which molecular stratification is needed to improve clinical outcomes. Targeting programmed cell death protein 1 (PD-1) elicits durable antitumor responses in multiple cancer types. Putative biomarkers predictive of response to anti-PD-1 therapies include programmed death-ligand-1 (PD-L1), tumour mutational burden (TMB), T cell-inflamed 18-gene expression profile (GEP), and DNA repair defects. Objective: To study potential biomarkers of response in mCRPC to anti-PD-1 therapy (PD-L1, GEP, mismatch repair (MMR) protein), other biomarkers of interest including BRCA2, PALB2, CDK12, PTEN, TP53, SOX2, and to determine association with clinical outcomes. Methods: The study population included 100 men with mCRPC treated at the Royal Marsden Hospital with available fresh mCRPC biopsy tissue. All men had received at least one line of therapy with a next generation hormonal agent and one line of taxane-based chemotherapy. Clinical characteristics and outcomes were extracted from medical records. mCRPC biopsies were assayed by whole exome sequencing (WES), targeted next generation sequencing (NGS), RNA sequencing (RNAseq), GEP score (Nanostring), PD-L1 immunohistochemistry (IHC; DAKO 22C3 assay), SOX2 IHC, ATM IHC. Correlations among these biomarkers and clinical outcomes were assessed. Results: The median age of patients was 68.0 years; 46/84 (54.8%) had de novo metastatic disease at diagnosis and 24/100 (24.0%) patients had visceral disease. Median follow-up from mCRPC biopsy was 56.2 months. The prevalence of loss of protein expression by IHC and/or pathogenic mutation by NGS of MMR was 7/100 (7%). Loss of PTEN and ATM by IHC was 29/100 (29%) and 13/100 (13%) respectively. SOX2 expression (defined as expression in >5% of cells) was 27/100 (27%). The prevalence of TP53 mutation was 25/100 (25%); deleterious alterations of BRCA2 was 9/100 (9%), CDK12 3/100 (3%) and PALB2 1/100 (1%). PDL1 and GEP results were available for 70 and 93 samples respectively. PD-L1 was expressed (combined positive score ≥1) in 24 (33%) mCRPC biopsies; 23 (26%) had high GEP scores (> -0.318). PD-L1 and GEP expression were positively correlated (Phi 0.63). No other biomarkers showed strong correlations. Of 5 samples with MMR loss for which PD-L1 was available, 1 (20%) had PD-L1 ≥1; one of the CDK12 samples had PD-L1 ≥1 (33%). 0/6 BRCA2 mutated biopsies expressed PD-L1 (0%). Based on univariate analysis, PD-L1 expression [HR: 1.75 (1.00;3.06), p=0.045], high GEP score [HR: 2.00 (1.18;3.39), p=0.0083] and SOX2 expression [HR: 1.81 (1.12;2.94), p=0.015] were associated with worse overall survival (OS). No other biomarkers associated with OS. Conclusions: PD-L1 IHC expression was detected in 33% of mCRPC patients and associated with high GEP score. Higher PD-L1, GEP, and SOX2 expression were associated with poor prognosis.

PI3K/AKT pathway biomarkers analysis from the phase III IPATential150 trial of ipatasertib plus abiraterone in metastatic castration-resistant prostate cancer

13

Background: In IPATential150 (NCT03072238), ipatasertib (ipat) + abiraterone (abi) as first-line treatment for metastatic castration-resistant prostate cancer (mCRPC) significantly reduced the risk for disease worsening or death vs placebo (pbo) + abi in patients (pts) with tumors with PTEN loss by immunohistochemistry (IHC; HR, 0.77 [95% CI: 0.61, 0.98]; P = 0.0335) but not in the intention-to-treat population (de Bono, ESMO 2020). In patients with PTEN loss tumors by IHC, median radiographic progression-free survival (rPFS) was 16.5 mo (95% CI: 13.9, 17.0) with pbo + abi and 18.5 mo (95% CI: 16.3, 22.1) with ipat + abi. Here, we present exploratory analyses evaluating putative biomarker associations with rPFS. Methods: Before randomization, tumor samples ( > 90% archival) were tested for PTEN loss by VENTANA PTEN (SP218) IHC assay (N = 1101). PTEN loss was pre-defined as ≥ 50% of tumor cells with no specific cytoplasmic IHC staining. Exploratory analysis evaluated different IHC staining cutoffs. Tumor genomic alterations were profiled with next-generation sequencing (NGS) using the Foundation Medicine FoundationOne CDx NGS assay (Shi, ASGO-GU 2020; n = 743 evaluable by NGS, of which n = 518 were PTEN evaluable). rPFS was determined by the investigator. Results: Consistent benefit with the combination arm vs pbo + abi was observed when PTEN loss by IHC was defined more stringently (rPFS at ≥ 60% tumor cells with PTEN loss: HR, 0.72 [95% CI, 0.56, 0.92]; ≥ 70%: HR, 0.72 [95% CI, 0.56, 0.93]; ≥ 80%: HR, 0.71 [95% CI, 0.54, 0.92]; ≥ 90%: HR, 0.72 [95% CI, 0.53, 0.97]; 100%: HR, 0.65 [95% CI, 0.39, 1.08]). In contrast, ipat + abi was not associated with improved rPFS in pts with PTEN intact by IHC tumors ( < 50% no staining; stratified HR, 0.91 [95% CI: 0.72, 1.16]); the median rPFS was 19.1 mo (95% CI: 16.4, 21.9) with pbo + abi and 19.7 mo (95% CI: 16.4, 26.3) with ipat + abi. By NGS assessment, pts with tumors with PTEN loss and with genomic alterations in PIK3CA/AKT1/PTEN had a larger magnitude of rPFS benefit with ipat + abi than pts with no detectable alterations (Table). Conclusions: Analyses of more-stringent biomarkers associated with activation of the PI3K/AKT pathway further support ipat + abi as a treatment option for first-line mCRPC with PI3K/AKT pathway alterations, a mCRPC subtype with a worse prognosis. Clinical trial information: NCT03072238. [Table: see text]

CTC counts as a biomarker of prognosis and response in metastatic castration-resistant prostate cancer (mCRPC) from the CARD trial

161

Background: In the prospective CARD trial (NCT02485691), cabazitaxel significantly improved radiographic progression-free survival (rPFS) and overall survival (OS) versus abiraterone or enzalutamide in patients with metastatic castration-resistant prostate cancer who had received docetaxel and progressed within 12 months with the alternative androgen-signaling-targeted inhibitor. Here we analyzed circulating tumor cell (CTC) counts as a biomarker of prognosis and response to therapy. Methods: Blood samples collected at screening (SC), Cycle 2 (C2) Day 1, and end of therapy were sent to Epic Sciences for CTC analysis. The association between CTC counts, defined as any cytokeratin-positive, CD45-negative cell, and clinical outcomes were pre-specified and analyzed using a multivariate Cox model for time-to-events (rPFS, OS) or a Χ2 test for categorical outcomes (objective tumor response). Results: Of the 255 patients randomized, 237 (92.9%) had evaluable samples at SC and 213 (83.5%) at C2. CTCs ≥ 1 were detected in 204 samples at SC (86%) and 178 samples at C2 (84%), with a median (interquartile range) count per mL of blood of 4.1 (1.3–14.2) and 5.2 (1.5–17.3), respectively. At baseline, higher CTC counts were associated with higher values of lactate dehydrogenase (P = 0.014), alkaline phosphatase (P < 0.001), and prostate-specific antigen (P < 0.001). High CTC counts, measured as a continuous variable at SC (all arms combined) were associated with a shorter OS (P = 0.03), but not rPFS (P = 0.7). However, favorable changes in absolute CTC count from SC to C2, all arms combined, were associated with longer rPFS (P = 0.03). Conversion from high (≥ 3) to low (< 3) CTC count at C2 or maintenance of a low CTC count at C2 was associated with objective tumor response (P = 0.007). Analysis of the associations of CTC androgen receptor variant 7, chromosomal instability, heterogeneity status (Shannon Index), single-cell genotypes (e.g. retinoblastoma/phosphatase and tensin homolog copy-loss), and the presence of CTCs with small-cell/neuroendocrine morphology is ongoing. Conclusions: This preplanned analysis of the CARD trial confirms that baseline CTC counts, measured by Epic Sciences platform, are prognostic. Moreover, early favorable changes in CTC counts from baseline to C2 are associated with response to therapy. Funding: Sanofi. Clinical trial information: NCT02485691.

SAPROCAN: Saracatinib (AZD0530) and docetaxel in metastatic,castrate-refractory prostate cancer (mCRPC)—A phase I/randomized phase II study by the United Kingdom National Cancer Research Institute Prostate Group

107

Background: Saracatinib is an orally-available, highly selective inhibitor of Abl and Src family members. It is an ATP-competitive tyrosine kinase inhibitor. Preclinical data suggested that the combination of a Src kinase inhibitor and docetaxel is synergistic, and Src kinase activity was also implicated in the bone’s metabolic response to cancer metastases. Methods: Patients with mCRPC were initially enrolled in an open-label, dose escalation phase I trial of oral saracatinib (cohorts of 50mg, 125mg and 175mg daily) with docetaxel (75mg/m2) in a 3+3 design. Subsequent patients were randomised 1:1 between saracatinib 175mg and placebo once daily. Pharmacokinetics (PK) of docetaxel were explored in phase I to exclude significant drug-drug interaction. The primary endpoint of phase II was biochemical or radiographic progression free survival (PFS). Secondary endpoints included overall survival (OS), safety and tolerability. Changes in circulating tumour cell (CTC) counts were also measured. The phase II was designed with a 1-sided alpha of 0.2 with 90% power to detect a hazard ratio (HR) for PFS of 0.67. Results: 10 patients were enrolled in phase I and 142 in the randomised phase II. No dose limiting toxicities or PK interactions were observed and the recommended dose for phase II was 175mg saracatinib daily and 75mg/m2docetaxel every 21 days. In phase II, the HR for PFS was 1.35 (80% confidence interval (CI) 1.07 to 1.70). The HR for OS was 1.42 (1.08 – 1.81). 41/71 and 29/71 experienced treatment related toxicities of grade 3 or above in the saracatinib and placebo arms respectively. 10/19 (53%) and 14/27 (52%) evaluable patients demonstrated a reduction in CTCs from ≥5 to < 5 /7.5ml blood at 6 weeks after starting saracatinib and placebo respectively. Conclusions: Saracatinib, in combination with docetaxel, adds toxicity and not efficacy in mCRPC. This combination should not be developed further in combination with docetaxel in the treatment of mCRPC. Clinical trial information: ISRCTN22566729.

KEYNOTE-365 cohort B: Pembrolizumab (pembro) plus docetaxel and prednisone in abiraterone (abi) or enzalutamide (enza)–pretreated patients with metastatic castration-resistant prostate cancer (mCRPC)—New data after an additional 1 year of follow-up

10

Background: For men with mCRPC, systemic therapies such as docetaxel and cabazitaxel improve survival, but more effective treatments are needed. KEYNOTE-365 (NCT02861573) is a phase 1b/2 study to examine the safety and efficacy of pembro in combination with 4 different study medications (cohorts A, B, C, D) in mCRPC. Previous data from cohort B with a median of 20 months of follow-up showed that pembro + docetaxel and prednisone was well tolerated and had antitumor activity in patients (pts) with mCRPC previously treated with abi or enza. New efficacy and safety data after an additional year of follow-up are presented. Methods: Cohort B enrolled pts who did not respond to or were intolerant to ≥4 weeks of abi or enza in the prechemotherapy mCRPC state and whose disease progressed within 6 months of screening (determined by PSA progression or radiologic bone/soft tissue progression). Pts received pembro 200 mg IV every 3 weeks (Q3W), docetaxel 75 mg/m2 IV Q3W, and oral prednisone 5 mg twice daily. Primary end points were safety, PSA response rate (PSA decrease >50% from baseline), and ORR per RECIST v1.1 by blinded independent central review. Efficacy and safety were assessed in all pts as treated. Results: Of the 104 treated pts, median age was 68.0 years (range, 50-86), 23.1% had PD-L1–positive tumors (combined positive score ≥1), 25.0% had visceral disease, and 50.0% had measurable disease. Median time from enrollment to data cutoff was 32.4 months (range 13.9-40.3); 101 pts discontinued, primarily because of disease progression (77.9%). Efficacy outcomes are reported in the table below. Treatment-related adverse events (TRAEs) occurred in 100 pts (96.2%); the most frequent (≥30%) were diarrhea (41.3%), fatigue (41.3%), and alopecia (40.4%). Grade 3-5 TRAEs occurred in 46 pts (44.2%). Five pts (4.8%) died of AEs; 2 were treatment-related pneumonitis. Conclusions: After another year of follow-up, pembro + docetaxel and prednisone showed improved ORR and PSA response rates compared to the prior dataset in pts with mCRPC previously treated with abi or enza. Safety was consistent with known profiles of each agent and will be further evaluated in a phase 3 study (KEYNOTE-921). Clinical trial information: NCT02861573. [Table: see text]

Abstract LB-075: CDK12-mutated lethal prostate cancers: How hot are these tumors

Background: Genomic analyses describing the molecular landscape of primary prostate cancer (PCa) and metastatic castration-resistant prostate cancer (mCRPC) have identified recurrent CDK12 alterations in 2-4% of primary PCa and 4-11% of mCRPC. These aberrations, as well as high lymphocyte tumor infiltration, could be clinically relevant as putative biomarkers of response to immunotherapies. However, there are few studies looking into whether CDK12 biallelic mutant cases are immune ‘hot'. Here, we describe a cohort of patients with CDK12 aberration and studied the tumor infiltration of those cancers.

Methods: Patients with mCRPC and available diagnostic archival and/or CRPC tumor samples were evaluated. Mutation analysis involved custom designed targeted sequencing on MiSeq sequencer. Loss of heterozygosity (LOH) was assessed for the CDK12 cases from exome sequencing using ASCAT, which include single copy lost or copy neutral LOH. Tumor infiltrating lymphocytes were assessed initially with CD3 IHC, using a deep learning-based AI analysis approach. We then subtyped the TILs using a multiplex IF approach, classifying lymphocytes using CD4, CD8 and FOXP3 positivity.

Results: Overall 913 samples (between Feb/15 and Oct/19) were sequenced by targeted NGS, 42 patients presented with pathogenic alterations in CDK12 (4.6%), 27 had bi-allelic alterations, 14 mono-allelic, 1 likely biallelic. In these cases, we identified 39 frameshift alterations, 10 missense mutations mainly involving the kinase domain; with 5 having concomitant LOH. One case showed deep deletion of CDK12 and five presented with additional aberrations in other DNA repair related genes. CDK12 biallelic alterations were present in all 3 cases with both diagnostic and matched mCRPC samples available. We studied T cell infiltration in 100 (23 CDK12 biallelic alterations, 7 monoallelic, 70 controls) samples selected from within the initial targeted NGS cohort. Median intratumoral CD3+ cell density was significantly higher in CDK12 biallelic loss samples compared to matched controls in diagnostic biopsies (271.4 vs 104.683 cells/mm2, p=0.026). A similar trend was seen in mCRPC samples (142.130 vs 51.75 cells/mm2, p=0.36). Intratumoral CD4+ cell infiltration was again significantly higher in CDK12 biallelic loss samples compared to controls (98.864 vs 6.188 cells/mm2, p=0.014).

Conclusions: In our analysis we show that a proportion of mCRPC patients harbor defects in CDK12, these are often alterations involving both alleles, likely present from the time of diagnosis. A majority of these CDK12 altered cancers has high CD3 infiltration compared to controls. We envision that these CDK12 aberrant ‘hot' tumors could represent a subset of mCRPC likely to respond to immune-checkpoint inhibition.

Citation Format: Bora Gurel, Pasquale Rescigno, Wei Yuan, Rita Pereira, Mateus Crespo, Mattia Rediti, Ines Figueiredo, Maialen Barrero, Diletta Bianchini, Maria D. Fenor de la Maza, Khobe Chandran, Juliet Carmichael, Alec Paschalis, Adam Sharp, George Seed, Ruth Riisnaes, Claudia Bertan, Suzanne Carreira, Johann S. De Bono. CDK12-mutated lethal prostate cancers: How hot are these tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr LB-075.

TALAPRO-1: Phase II study of talazoparib (TALA) in patients (pts) with DNA damage repair alterations (DDRm) and metastatic castration-resistant prostate cancer (mCRPC) – updated interim analysis (IA)

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Background: PARP inhibitors (PARPi) show antitumor activity in mCRPC/DDRm pts treated with novel hormonal therapy (NHT). TALAPRO-1 is an open-label study evaluating TALA (potent PARP inhibitor/trapper) in men with mCRPC/DDRm. We report a planned IA (Dec 2019). Methods: TALAPRO-1 (NCT03148795) is enrolling pts (N ≈ 100) with measurable soft tissue disease, progressive mCRPC, and DDRm likely to sensitize to PARPi ( ATM, ATR, BRCA1/2, CHEK2, FANCA, MLH1, MRE11A, NBN, PALB2, RAD51C), who received 1–2 chemotherapy regimens (≥1 taxane-based) for metastatic disease and progressed on ≥1 NHT (enzalutamide/abiraterone acetate) given for mCRPC. DDRm are defined as known/likely pathogenic variants or homozygous deletions. Pts receive oral TALA 1 mg/day (moderate renal impairment 0.75 mg/day) until radiographic progression, unacceptable toxicity, consent withdrawal or death. Primary endpoint is objective response rate (ORR). Secondary endpoints: time to OR; response duration; PSA decrease ≥50%; circulating tumor cell (CTC) count conversion (to CTC = 0 and <5 per 7.5 mL blood); time to PSA progression; radiographic PFS (rPFS); overall survival; safety. A planned efficacy/safety IA was done when 60 pts with DDRm and measurable disease completed ≥6 months of TALA/no longer followed (DDR population [DDRp]). Radiographic responses are based on investigator assessments. Results: 113 pts received TALA (cutoff Dec 12, 2019); 75 pts were DDRp, had measurable disease, received ≥16 wk treatment, and were evaluable for ORR (54.7% BRCA1/2, 4.0% PALB2, 22.7% ATM; 18.7% other DDRm).All DDRp pts had prior docetaxel; 45.3% cabazitaxel. Confirmed ORR, rPFS, and composite response (investigator-assessed) in pts who received TALA for ≥16 weeks are in the table. Most common treatment-emergent adverse events: anemia (42.5%); nausea (32.7%). Conclusions: TALA monotherapy has encouraging antitumor activity in docetaxel-pretreated mCRPC pts with BRCA1/2 alterations and was generally well tolerated. Clinical trial information: NCT03148795 . [Table: see text]

First-in-human phase I study of HPN424, a tri-specific half-life extended PSMA-targeting T-cell engager in patients with metastatic castration-resistant prostate cancer (mCRPC)

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Background: HPN424 is a first-in-class, prostate-specific membrane antigen (PSMA)-targeting T-cell engager designed as a small, globular protein to enable efficient solid-tumor penetration with prolonged half-life. HPN424 is derived from the TriTAC platform (Tri-specific T-Cell-Activating Construct) and engineered with three binding domains: anti-PSMA for tumor cell engagement, anti-albumin for half-life extension and anti-CD3 for T-cell engagement. Methods: This Ph I study is evaluating HPN424 in progressing mCRPC patients (pts) who have received >2 prior systemic therapies. Primary endpoints are safety, tolerability and determination of MTD/RP2D. Secondary objectives are pharmacokinetics (PK), pharmacodynamics, immunogenicity, and preliminary anti-tumor activity. HPN424 is administered IV once weekly. Tumor assessments include PSA, CT, and bone scans every 9 weeks. Results: As of 1/17/20, 27 pts were dosed in 8 cohorts ranging from 1.3 to 72ng/kg. Pts received a median of 6 prior systemic regimens, including >1 novel AR therapy, and 59% received prior chemotherapy for mCRPC. Median PSA at baseline was 251 ng/mL (range: 0.05 – 5000). No DLTs have been observed. The most common grade >3 TRAEs were cytokine release syndrome (CRS) (3 pts) and transient elevated liver transaminases (2 pts) that occurred concurrently with CRS. All CRS events resolved and pts were successfully re-treated. Short-term steroid premedication was effective in limiting CRS and allowing long-term weekly treatment. HPN424 demonstrated dose proportional increase in Cmax and AUC with a geometric mean T1/2 of 30.5 hours. Dose-dependent, transient increases in peripheral cytokine and chemokine levels were observed. Reduction in circulating tumor cells (CTCs) was seen in 11 of 19 pts with measurable CTC at baseline. Six pts had PSA decreases from baseline ranging from -3.8% to -76%, including 2 pts with PSA decline ≥50%. Ten of 20 pts (50%) with > 18 weeks follow-up remained on study beyond week 18 and includes 8 pts on study > 24 weeks. Conclusions: HPN424 represents a novel half-life extended PSMA-targeting T-cell engager that can be safely administered once weekly. AEs have been transient and manageable. Cytokine increases indicate T-cell activation. CTC reductions in subset of pts suggest target engagement. Early signs of clinical activity include PSA reductions and time on study, including 8 pts on study > 24 weeks. Dose escalation is ongoing, including exploration of step dosing. Clinical trial information: NCT03577028 .

Pembrolizumab (pembro) plus olaparib in patients (pts) with docetaxel-pretreated metastatic castration-resistant prostate cancer (mCRPC): KEYNOTE-365 cohort A efficacy, safety, and biomarker results

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Background: Pembro + olaparib has shown antitumor activity and acceptable safety in docetaxel-pretreated pts with mCRPC enrolled in cohort A of the phase I/II KEYNOTE-365 study (NCT02861573). Updated results with new biomarker data are reported. Methods: Pts with docetaxel-pretreated mCRPC who progressed within 6 mo of screening received pembro 200 mg IV Q3W + olaparib 400-mg capsule or 300-mg tablet PO BID. Pts might have received 1 other chemotherapy and ≤2 second-generation androgen-receptor targeted therapies. Primary end points: PSA response rate (decrease ≥50% from baseline, confirmed by a second value ≥3 wks later), ORR per RECIST v1.1, and safety. Key secondary end points: DCR, DOR, rPFS, and OS. Biospecimens (eg, blood, tissue) were collected for biomarker analysis (tissue PD-L1 expression, androgen receptor variant 7 [AR-v7] expression in circulating tumor cells [CTCs], and a T-cell–inflamed gene expression profile [GEP]). ctDNA was analyzed by Guardant Health 360 (GH360) and Omni (GH Omni) assays. FFPE tissue was analyzed by FoundationOne CDx (F1CDx) assay. Results: 84 of 87 enrolled pts were treated; 48/84 (57.1%) had measurable disease. Median (range) time from enrollment to data cutoff was 3.6 mo (0.0-29.2) for all pts and 26.7 mo (21.2-29.2) for 41 pts with ≥27 wks’ follow-up. Confirmed PSA response rate was 9% (95% CI, 3.5-16.8) in 82 pts with a baseline PSA assessment. Median time to PSA progression: 3.8 mo (95% CI, 2.9-4.4). In 24 pts with measurable disease and ≥27 wks’ follow-up, ORR was 8.3% (95% CI, 1.0-27.0; 2 PRs) and DCR ≥6 mo was 20.8% (95% CI, 7.1-42.2). Median (range) DOR was NR (12.0+ to 21.4+ mo); 2 pts had DOR ≥12 mo. In all pts, median rPFS was 4.3 mo (95% CI, 3.4-7.7) and median OS was 14.4 mo (95% CI, 8.1-18.5). Grade ≥3 TRAEs occurred in 29 pts (35%); 2 pts died of TRAEs (1 myocardial infarction, 1 unknown). Overall, 26% had PD-L1+ tumors (combined positive score ≥1). Of 31 pts with CTC data, 12.9% were AR-v7+. No BRCA1/2 mutation was detected by GH360 (n=42). Of 57 pts analyzed by GH Omni, 2 had BRCA2 mutations, 1 had a BRCA1 mutation, 4 had ATM mutations, 1 had a CHEK1 mutation, and 6 had CDK12 mutations. Of 49 pts analyzed by F1CDx, 4 had BRCA mutations; 1 pt had a copy number loss mutation not detected by ctDNA analysis. GEP was not associated with ORR or PSA response. Conclusions: Pembro + olaparib continued to show activity and acceptable safety in pts with docetaxel-pretreated mCRPC. A phase III study of this combination is ongoing (KEYLYNK-010, NCT03834519). Clinical trial information: NCT02861573 .

Phase 1b study of BXCL701, a novel small molecule inhibitor of dipeptidyl peptidases (DPP), combined with pembrolizumab (pembro), in men with metastatic castration-resistant prostate cancer (mCRPC)

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Background: BXCL701 (talabostat previously PT100) is an oral small molecule inhibitor of DPP4, DPP8 and DPP9, which trigger macrophage cell death via pyroptosis resulting in proinflammatory stimulation of the innate immunity pathway. Expression of PD-L1 correlates with amplification of DPP8 and DPP9. In syngeneic animal models, significant tumor responses were observed when BXCL701 was used with checkpoint inhibition. In a prior clinical study, BXCL701 at a total daily dose of 0.6mg (as 0.3mg BID) demonstrated single agent activity in 2 pts with Stage IV melanoma (unpublished). Methods: In this multi-center study, eligible patients (pts) had progressing mCRPC (PCWG3), at least 1 line of systemic therapy and ≤ 2 lines of cytotoxic chemotherapy for mCRPC, no prior anti-PD-1/PD-L1 or other T-cell directed anti-cancer therapy, and an ECOG PS of ≤ 2. Pts received fixed dose pembro (200mg IV q21 days) with escalating doses of BXCL701 (0.4mg and 0.6mg PO QD days 1-14 of 21-day cycles) using a 3X3 design. The key endpoints were safety and identification of the recommended phase 2 dose (RP2D) for the combination. Composite response (RECIST, PSA, CTC), plasma drug concentration and change in relevant immune effector cytokines were also evaluated. Results: Six pts were treated at 2 BXCL701 dose levels of 0.4mg qd (n = 3) and 0.6mg qd (n = 3), with 5 pts having adeno, 1 pt having mixed adeno and SC-NEPC. Prior tx included ADT (n = 6), 2nd generation androgen signaling inhibitors (n = 4), chemo (n = 4), RT (n = 5). Among 3 pts at the BXCL701 dose level of 0.6mg, 1 pt had a DLT of Grade 3 syncope (C1D6) and 1 pt had fatal acidosis (C3D8). A dose-dependent increase in pts with low-grade on-target clinical effects was observed. In the 0.4mg qd cohort 1 pt had lower extremity (LE) edema. Whereas in the 0.6mg qd cohort, all pts had events consistent with cytokine release: 3 had hypotension and 2 pts each had dizziness and LE edema. The 0.6mg/day dose level was expanded using a split dose strategy to improve tolerability while maintaining the daily dose previously associated with objective responses. BXCL701 was quantifiable in plasma. Conclusions: BXCL701 0.4 mg QD on days 1 to 14 of 21-day cycle plus pembrolizumab 200 mg IV on day 1 every 21 days was well tolerated in pts with mCRPC. A dose-dependent increase in on-target clinical effects expected with cytokine upregulation was seen. The final dose expansion using the split dose for the RP2D, plasma drug concentrations and relevant biomarkers will be presented. Clinical trial information: NCT03910660 .

Pembrolizumab (pembro) plus enzalutamide (enza) in patients (pts) with abiraterone acetate (abi)-pretreated metastatic castration-resistant prostate cancer (mCRPC): KEYNOTE-365 cohort C efficacy, safety, and biomarker results

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Background: Pembro + enza (cohort C) has shown antitumor activity and acceptable safety in abi-pretreated pts with mCRPC in the phase I/II KEYNOTE-365 study (NCT02861573). Updated results with new biomarker data from cohort C are reported. Methods: Pts who became intolerant to or for whom ≥4 weeks of abi failed in the prechemotherapy mCRPC state and who progressed within 6 mo of screening were enrolled. Pts received pembro 200 mg IV Q3W + enza 160 mg/day orally. Primary end points were PSA response rate (PSA decrease ≥50%; confirmed by a second value ≥3 weeks later), ORR per RECIST v1.1 by blinded independent central review, and safety. Key secondary end points were DCR per RECIST v1.1 (CR+PR+SD or non-CR/non-PD ≥6 mo), DOR per RECIST v1.1, radiographic PFS (rPFS) per PCWG-modified RECIST v1.1, and OS. Biospecimens (eg, blood, tissue) were collected at baseline and during the study for biomarker analysis, including tissue PD-L1 expression, androgen receptor variant 7 (AR-v7) expression in circulating tumor cells (CTCs), and a T-cell-inflamed gene expression profile (GEP). Results: Of 103 enrolled pts, 102 were treated; 39% of treated pts had measurable disease. Median (range) time from enrollment to data cutoff was 19.1 mo (1.1-28.8) for all pts and 21.4 mo (15.1-28.8) for pts with ≥27 wks’ follow-up (n=69). Confirmed PSA response rate was 22% in 101 pts with a baseline PSA assessment. Median time to PSA progression was 3.5 mo (95% CI, 2.9-4.0). In pts with measurable disease and ≥27 wks’ follow-up (n=25), confirmed ORR was 12% (2 CRs, 1 PR) and DCR was 32%. Median DOR was not reached (range, 0.0+ to 24.4+ mo); 2 pts had a response for ≥6 mo. In all pts, median (95% CI) rPFS was 6.1 mo (4.4-6.5) and median OS was 20.4 mo (15.5-NR). At 6 mo, rPFS rate was 55.1% and OS rate was 88.2%. Treatment-related AEs occurred in 92 pts (90%); most frequent (≥20%) were fatigue (38%), nausea (22%), and rash (20%). Grade 3-5 treatment-related AEs occurred in 40 pts (39%). Three pts died of AEs (1 AE was treatment related [cause unknown]). Of all pts, 29% had PD-L1+ tumors (combined positive score ≥1). Of 51 pts with AR-v7 data, 13.7% were AR-v7+ and 86.3% were AR-v7−. GEP was not significantly associated with ORR or PSA response. Conclusions: Pembro + enza continued to show activity in pts with abi-pretreated mCRPC. Safety of the combination was consistent with the known profiles of pembro and enza. A phase III study of this combination is ongoing (KEYNOTE-641, NCT03834493). Clinical trial information: NCT02861573 .

Health-related quality of life (HRQoL) for olaparib versus enzalutamide or abiraterone in metastatic castration-resistant prostate cancer (mCRPC) with homologous recombination repair (HRR) gene alterations: PROfound

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Background: In the randomized Phase III PROfound trial (NCT02987543), olaparib significantly prolonged radiographic progression-free survival compared with physician’s choice of new hormonal agent (pcNHA, enzalutamide or abiraterone) in men with mCRPC and HRR gene alterations, whose disease had progressed on prior NHA. Olaparib significantly improved time to pain progression in Cohort A. We report additional patient reported outcome measures of HRQoL in the overall study population (Cohorts A+B). Methods: HRQoL was assessed in the overall study population using the Functional Assessment of Cancer Therapy-Prostate (FACT-P) questionnaire, comprising 5 subscales: physical wellbeing (PWB), functional wellbeing (FWB), emotional wellbeing, social wellbeing, and prostate cancer subscale (PCS). The Trial Outcome Index (TOI; PWB+FWB+PCS) and FACT Advanced Prostate Symptom Index (FAPSI-6: derived from 6 FACT-P items) were also calculated. Adjusted mean change and time to deterioration in scores were statistically analyzed. Results: Baseline FACT-P total score was similar for both treatment arms. FACT-P total and subscale scores during treatment were all higher for olaparib vs pcNHA, with clinically meaningful differences between treatment arms in the adjusted least square (LS) mean changes from baseline in all but FWB and FAPSI-6 (Table). The time to deterioration in FACT-P total and TOI, FAPSI-6, PWB and PCS scores favored olaparib but were not statistically significant, with hazard ratios ranging from 0.68 to 0.94. Further HRQoL results for cohort A will also be presented. Conclusions: Olaparib delayed deterioration in HRQoL scores vs pcNHA and was associated with better HRQoL functioning over time compared with pcNHA in men with mCRPC and HRR gene alterations. Clinical trial information: NCT02987543 . [Table: see text]

Biomarker analysis from the KEYNOTE-199 trial of pembrolizumab in patients (pts) with docetaxel-refractory metastatic castration-resistant prostate cancer (mCRPC)

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Background: In the phase II KEYNOTE-199 study (NCT02787005), pembrolizumab monotherapy demonstrated antitumor activity in pts with docetaxel-refractory mCRPC (n = 258). Here we evaluated the association between prespecified molecular biomarkers and clinical outcomes. Methods: Cohorts 1 (C1) and 2 (C2) enrolled pts with RECIST-measurable PD-L1–positive (combined positive score [CPS] ≥1 using immunohistochemistry) and PD-L1–negative (CPS <1) disease, respectively. C3 enrolled pts with nonmeasurable, bone-predominant disease, irrespective of PD-L1 status. Biomarkers evaluated in this analysis were tumor mutational burden ([TMB; mutations/exome] n = 155), PD-L1 CPS (n = 255), tumor microenvironment–based 18-gene RNA expression profile ([GEP] n = 196), and microsatellite instability ([MSI] as determined by Promega PCR analysis; n = 147). Outcomes evaluated for C1 and C2 (n = 200) were ORR, disease control rate (DCR), and radiographic PFS (rPFS) per blinded, independent central review per PCWG-modified RECIST v1.1. Outcomes evaluated for C1-C3 (n = 258) were prostate-specific antigen (PSA) response, time to PSA progression, and OS. Significance of continuous biomarkers (CPS; TMB; GEP) was prespecified at 0.05 for one-sided P values from logistic (ORR; DCR; PSA response) and Cox proportional hazard regression (rPFS; OS; PSA progression) adjusted for Eastern Cooperative Oncology Group performance status. Binary biomarkers (MSI) were analyzed using Fisher’s exact test (ORR; DCR; PSA response). Clinical data cutoff date: Jun 24, 2019. Results: Median TMB was 53.0 (interquartile range [IQR], 40.5 to 78.0), median CPS was 1 (IQR, 0 to 5), and median GEP was –0.64 (IQR, –0.88 to –0.46); 6 pts (2.3%) had MSI-high tumors. In C1-C3, TMB was associated with PSA response (one-sided nominal P = 0.0016) and time to PSA progression (one-sided nominal P = 0.00092). In C1-C3, PD-L1 CPS was associated with PSA response (one-sided nominal P = 0.046) and time to PSA progression (one-sided nominal P = 0.021). In C1-C3, GEP was not significantly associated with response. In C1-C3, MSI was associated with PSA response (one-sided nominal P = 0.019). Conclusions: In this biomarker analysis from KEYNOTE-199 C1-C3, TMB and PD-L1 CPS were associated with better PSA response; however, small pt numbers limit definitive conclusions on ORR, DCR, and OS. Further evaluation of molecular biomarkers in pts with mCRPC treated with pembrolizumab is warranted. Clinical trial information: NCT02787005 .

Impact of olaparib vs physician’s choice of new hormonal agent (pcNHA) on burden of pain in metastatic castration-resistant prostate cancer (mCRPC): PROfound

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Background: In the Phase III PROfound study (NCT02987543) olaparib significantly improved radiographic progression-free survival (primary endpoint) vs pcNHA (enzalutamide or abiraterone) in patients (pts) with mCRPC and homologous recombination repair (HRR) gene alterations. In pts with alterations in BRCA1, BRCA2 and/or ATM (cohort A), time to pain progression was also significantly improved by olaparib vs pcNHA. We report additional pain analyses evaluated in the overall study population (cohort A and B). Methods: Pts were randomized to olaparib tablets (300 mg bid; n=256) or pcNHA (n=131). Pts completed the Brief Pain Inventory-Short Form (BPI–SF) questionnaire (electronic administration) every 4 weeks up to 6 months after progression or treatment crossover. Responses were analysed to determine time to progression to worst pain, pain severity and first opiate use for cancer-related pain (Kaplan-Meier), and also pain interference in daily activity (mixed model for repeated measures). Results: 85% and 76% of olaparib pts were free of pain progression (worst pain item) compared with 75% and 51% in the pcNHA arm, respectively at 6 and 12 months. The proportion of pts without pain progression (overall pain severity) also favoured olaparib (Table). Median time to first opiate use was significantly prolonged in olaparib arm compared with pcNHA arm; 18 months for olaparib vs 9 months for pcNHA (Table). BPI-SF pain interference scores were also more favourable for olaparib than pcNHA; difference in overall adjusted mean change from baseline score −0.75 (95% CI: −1.14, −0.36) P=0.0002. Further pain burden results for cohort A will also be presented. Conclusions: Olaparib reduced the burden of pain and time to first opiate use in pts with mCRPC and HRR gene alterations vs pcNHA, demonstrating a clinical and symptomatic patient benefit. Clinical trial information: NCT02987543 . [Table: see text]

Phase II study of pembrolizumab in docetaxel-pretreated patients with metastatic castration-resistant prostate cancer (mCRPC): Updated follow-up of cohorts (C) one to three from KEYNOTE-199

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Background: Pembrolizumab monotherapy has shown antitumor activity and acceptable safety in patients with mCRPC previously treated with a next-generation hormone agent (NHA) and docetaxel. Presented herein are updated results from KEYNOTE-199 (NCT02787005), a multicohort phase 2 study, in patients with RECIST-measurable PD-L1+ disease (C1), RECIST-measurable, PD-L1− disease (C2), and bone-predominant disease, irrespective of PD-L1 (C3). Methods: Patients who previously received ≥1 NHA and 1 or 2 chemotherapies, including docetaxel, received pembrolizumab 200 mg Q3W for 35 cycles or until progression/toxicity. The primary end point was ORR per RECIST v1.1 by blinded independent central review (BICR). Key secondary end points were DCR, PSA response rate (≥50% decrease from baseline), time to PSA progression, rPFS, OS, DOR, and safety. rPFS and OS were evaluated using the Kaplan-Meier method. Results: Of 258 treated patients (C1, 133; C2, 67; C3, 58), 6 completed therapy (C1, 4; C3, 2) and 252 discontinued (C1, 129; C2, 67; C3, 56), primarily due to progression (C1, 106; C2, 61; C3, 45). Median (range) time from enrollment to data cutoff was 31.3 mo (26.7-34.7) in C1, 30.6 mo (28.0-34.1) in C2, and 32.6 mo (27.4-34.4) in C3. Efficacy results are displayed in the table. ORR (95% CI) for patients with measurable disease was 6% (2.6-11.5) in C1 and 3% (0.4-10.4) in C2. Of 10 responders, 6 had a DOR ≥18 mo. Median time to PSA progression was 4 mo across cohorts. Any grade treatment-related AEs (TRAEs) occurred in 57-60% of patients across C1-3. Grade ≥3 TRAEs occurred in 16% of patients in C1, 15% in C2, and 17% in C3; 1 patient in each cohort died of a TRAE (C1, sepsis; C2, unknown; C3, immune-related pneumonitis). Conclusions: Pembrolizumab monotherapy was well tolerated and showed durable, antitumor activity and disease control with survival up to 24 mo in 3 cohorts of docetaxel and NHA-pretreated patients with RECIST-measurable or bone-predominant mCRPC. Clinical trial information: NCT02787005 . [Table: see text]

Circulating tumor DNA (ctDNA) dynamics associate with treatment response and radiological progression-free survival (rPFS): Analyses from a randomized phase II trial in metastatic castration-resistant prostate cancer (mCRPC)

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Background: ctDNA can inform on prognosis, treatment response and survival. We evaluated ctDNA in serial plasma samples from patients enrolled in A.MARTIN (NCT01485861), a randomized phase II study of abiraterone with or without ipatasertib in patients with mCRPC. Methods: Blood was collected in cell-free DNA Streck tubes from 216 patients at 3 time points; baseline, C3D1 and end of treatment. Cell-free DNA (cfDNA) was extracted from plasma using a Circulating DNA Kit (Qiagen) on a QIASymphony machine (Qiagen). 25ng of extracted cfDNA was used in library preparation, constructed with a custom designed, 58 gene, QIAseq Targeted DNA panel (Qiagen) enriched for PI3K/AR pathway genes. Samples were sequenced to mean depth of 3394x on a NextSeq500 machine. Unless otherwise noted, all analyses combine patients across the 3 study arms, and reported p-values are unadjusted. Results: Baseline (BL) ctDNA positivity correlated with radiological progression-free survival (rPFS; HR: 1.8 [95% CI 1.3-2.6], p < 0.01); this association with rPFS was maintained in a multivariate cox model with > 5 baseline clinical variables (HR: 1.6 [95% CI 1.1-2.4]; p = 0.011). Patients with a C3D1 reduction in ctDNA had superior rPFS compared to patients with a C3D1 increase in ctDNA (HR: 2 [95% CI 1.3-3.2], p < 0.01). The rate of ctDNA clearance at C3D1 was higher in the Ipatasertib 400mg arm compared to placebo (56.3% versus 24.4%, p < 0.01). We find that changes in ctDNA associated with best confirmed overall response (p = 0.024); CR patients had the greatest reduction in ctDNA (mean of -23.4%), followed by PR (-16.3%), then SD (-4.1%), and lastly PD patients (-1.3%). Changes in ctDNA levels correlated with SLD changes (rs = 0.289, p = 0.05), and also PSA changes (rs = 0.33, p < 0.01). Changes in ctDNA were associated with rPFS in a multivariate cox analysis that included PSA change (p < 0.01), as well as in a separate multivariate analysis that included SLD change (p < 0.01). Lastly, we explored CNVs and observed emerging resistance mutations in progression samples, including alterations in TP53, AR, FOXA, PTEN, and PI3K/AKT pathway genes. Conclusions: ctDNA analyses may help (i) identify poorer prognosis disease at baseline, (ii) inform on treatment response (CR/PR/SD/PD) and radiological progression free survival (rPFS) in on-treatment (C3D1) samples, and (iii) can elucidate emerging resistance mechanisms at disease progression. Clinical trial information: NCT01485861 .

Pembrolizumab (pembro) plus docetaxel and prednisone in patients (pts) with abiraterone acetate (abi) or enzalutamide (enza)-pretreated metastatic castration-resistant prostate cancer (mCRPC): KEYNOTE-365 cohort B efficacy, safety and, biomarker results

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Background: Pembro + docetaxel and prednisone (cohort B) has shown antitumor activity in pts with mCRPC in the phase I/II KEYNOTE-365 study (NCT02861573). Updated efficacy and safety and new biomarker data from cohort B are reported. Methods: Pts who received at least 4 wk of abi or enza in the prechemotherapy mCRPC setting and whose disease progressed within 6 mo of screening were eligible. Pts received pembro 200 mg IV + docetaxel 75 mg/m2 IV Q3W and prednisone 5 mg orally twice daily. Primary end points were PSA response rate (PSA decrease ≥50%; confirmed by a second value ≥3 weeks later), ORR per RECIST v1.1 by blinded independent central review, and safety. Key secondary end points were DCR per RECIST v1.1 (CR+PR+SD or non-CR/non-PD ≥6 mo), DOR per RECIST v1.1, radiographic PFS (rPFS) per PCWG-modified RECIST, and OS. Biospecimens (blood, tissue) were collected for biomarker analysis, including tissue PD-L1 expression, androgen receptor variant 7 (AR-v7) expression in circulating tumor cells, and a T-cell-inflamed gene expression profile (GEP). Results: Of 105 enrolled pts, 104 were treated, and 50% had measurable disease. Median (range) time from enrollment to data cutoff was 19.9 mo (1.4-27.8) for all pts and 21.8 mo (17.9-27.8) for pts with ≥27 wks follow-up (n=72). Confirmed PSA response rate was 28% in 103 pts with a baseline PSA assessment. Median time to PSA progression was 6.2 mo (95% CI, 3.7-7.4). In pts with measurable disease and ≥27 wks follow-up (n=39), ORR was 18% (7/39, all PRs) and DCR was 51%. Median DOR was 6.7 mo (range, 3.4-9.0+ [+ indicates ongoing responder]); 5 pts had a response for ≥6 mo. In all pts, median rPFS was 8.3 mo (95% CI, 7.6-10.1) and OS was 20.4 mo (16.9-NR). At 6 mo, the rPFS rate was 72.8% and OS rate was 95.3%. Treatment-related AEs (TRAEs) occurred in 96% of all pts; most frequent were alopecia (39%), diarrhea (38%), and fatigue (38%). Grade 3-5 TRAEs occurred in 40% of pts; 2 pts died of TRAEs (pneumonitis). Overall, 24% of pts were PD-L1+ (combined positive score ≥1). Of 57 pts with AR-v7 data, 17.5% were AR-v7+, 77% were AR-v7−, and 5% were undetermined. GEP was not significantly associated with ORR or PSA response. Conclusions: Pembro + docetaxel and prednisone showed activity in pts with abi or enza-pretreated mCRPC. Safety of the combination was consistent with the known profiles of the individual agents. A phase 3 study of this combination is ongoing (KEYNOTE-921, NCT03834506). Clinical trial information: NCT02861573 .

Efficacy and safety in older patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) receiving cabazitaxel (CBZ) versus abiraterone (ABI) or enzalutamide (ENZ) in the CARD study

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Background: In the CARD (NCT02485691) study, radiographic PFS (rPFS), PFS and OS were significantly improved with CBZ vs. androgen-signaling-targeted agents (ARTA; ABI or ENZ) in pts with mCRPC who had received docetaxel (DOC) and progressed within 12 months (mo) on an alternative ARTA. This analysis evaluated the impact of age (< 70 vs. ≥ 70 years) on the efficacy and safety of CBZ and ARTAs in CARD. Methods: 255 pts with mCRPC were randomized 1:1 to CBZ (25 mg/m2 IV Q3W + prednisone [P] + G-CSF) vs. ABI (1000 mg PO + P) or ENZ (160 mg PO) until disease progression, unacceptable toxicity or pt request. Pts were eligible if they had received ≥ 3 cycles of DOC and progressed ≤ 12 mo on the previous alternative ARTA. Primary endpoint was rPFS. Subgroup analysis of older (≥ 70 years; n = 135) and younger (< 70 years; n = 120) pts was pre-specified for rPFS; others were post hoc. Results: rPFS was significantly improved vs. ARTA in both older (median 8.2 vs. 4.5 mo; HR 0.58; 95% CI 0.38–0.89) and younger pts (median 7.4 vs. 3.2 mo; HR 0.47; 95% CI 0.30–0.74). Median OS for CBZ vs. ARTA was 13.9 vs. 9.4 mo (HR 0.66; 95% CI 0.41–1.06) in older pts and 13.6 vs. 11.8 mo (HR 0.66; 95% CI 0.41–1.08) in younger pts. PFS, tumor, PSA and pain responses also favored CBZ, regardless of age. Grade ≥ 3 adverse events (AEs) occurred in 57.8% vs. 49.3% of older pts receiving CBZ vs. ARTA and 48.4% vs. 42.1% in younger pts. AEs leading to death were more frequent with ARTA, mainly due to disease progression. Conclusions: CBZ had improved efficacy outcomes vs. ARTA in pts with mCRPC previously treated with DOC and the alternative ARTA, regardless of age. Grade ≥ 3 cardiac AEs were more frequent in older pts treated with ARTA. A higher rate of AEs was reported in older vs. younger pts, for ARTA and CBZ. CBZ and ARTA had different safety profiles in older compared with younger pts. Clinical trial information: NCT02485691 . Funding: Sanofi. [Table: see text]