Median Radiographic Progression-free Survival Research Articles

177Lu-PSMA-617 versus a change of androgen receptor pathway inhibitor therapy for taxane-naive patients with progressive metastatic castration-resistant prostate cancer (PSMAfore): a phase 3, randomised, controlled trial.

[177Lu]Lu-PSMA-617 (177Lu-PSMA-617) prolongs radiographic progression-free survival and overall survival in patients with metastatic castration-resistant prostate cancer previously treated with androgen receptor pathway inhibitor (ARPI) and taxane therapy. We aimed to investigate the efficacy of 177Lu-PSMA-617 in patients with taxane-naive metastatic castration-resistant prostate cancer. In this phase 3, randomised, controlled trial conducted at 74 sites across Europe and North America, taxane-naive patients with prostate-specific membrane antigen (PSMA)-positive metastatic castration-resistant prostate cancer who had progressed once on a previous ARPI were randomly allocated (1:1) to open-label, intravenous 177Lu-PSMA-617 at a dosage of 7·4 GBq (200 mCi) ± 10% once every 6 weeks for six cycles, or a change of ARPI (to abiraterone or enzalutamide, administered orally on a continuous basis per product labelling). Crossover from ARPI change to 177Lu-PSMA-617 was allowed after centrally confirmed radiographic progression. The primary endpoint was radiographic progression-free survival, defined as the time from randomisation until radiographic progression or death, assessed in the intention-to-treat population. Safety was a secondary endpoint. This study is registered with ClinicalTrials.gov (NCT04689828) and is ongoing. In this primary report of the study, we present primary (first data cutoff) and updated (third data cutoff) analyses of radiographic progression-free survival; all other data are based on the third data cutoff. Overall, of the 585 patients screened, 468 met all eligibility criteria and were randomly allocated between June 15, 2021 and Oct 7, 2022 to receive 177Lu-PSMA-617 (234 [50%] patients) or ARPI change (234 [50%]). Baseline characteristics were mostly similar between groups; median number of 177Lu-PSMA-617 cycles was 6·0 (IQR 4·0-6·0). Of patients assigned to ARPI change, 134 (57%) crossed over to receive 177Lu-PSMA-617. In the primary analysis (median time from randomisation to first data cutoff 7·26 months [IQR 3·38-10·55]), the median radiographic progression-free survival was 9·30 months (95% CI 6·77-not estimable) in the 177Lu-PSMA-617 group versus 5·55 months (4·04-5·95) in the ARPI change group (hazard ratio [HR] 0·41 [95% CI 0·29-0·56]; p<0·0001). In the updated analysis at time of the third data cutoff (median time from randomisation to third data cutoff 24·11 months [IQR 20·24-27·40]), median radiographic progression-free survival was 11·60 months (95% CI 9·30-14·19) in the 177Lu-PSMA-617 group versus 5·59 months (4·21-5·95) in the ARPI change group (HR 0·49 [95% CI 0·39-0·61]). The incidence of grade 3-5 adverse events was lower in the 177Lu-PSMA-617 group (at least one event in 81 [36%] of 227 patients; four [2%] grade 5 [none treatment related]) than the ARPI change group (112 [48%] of 232; five [2%] grade 5 [one treatment related]). 177Lu-PSMA-617 prolonged radiographic progression-free survival relative to ARPI change, with a favourable safety profile. For patients with PSMA-positive metastatic castration-resistant prostate cancer who are being considered for a change of ARPI after progression on a previous ARPI, 177Lu-PSMA-617 may be an effective treatment alternative. Novartis.

TRIUMPH: phase II trial of rucaparib monotherapy in patients with metastatic hormone-sensitive prostate cancer harboring germline homologous recombination repair gene mutations.

The activity of PARP inhibitors (PARPi) in patients with homologous recombination repair (HRR) mutations and metastatic castration-resistant prostate cancer has been established. We hypothesized that the benefit of PARPi can be maintained in the absence of androgen deprivation therapy (ADT) in an HRR-mutated population. We report the results of a phase II clinical trial of rucaparib monotherapy in patients with metastatic hormone-sensitive prostate cancer (mHSPC). This was a multi-center, single-arm phase II trial (NCT03413995) for patients with asymptomatic, mHSPC. Patients were required to have a pathogenic germline mutation in an HRR gene for eligibility. All patients received rucaparib 600 mg by mouth twice daily, without androgen deprivation. The primary endpoint was a confirmed PSA50 response rate. Twelve patients were enrolled, 7 with a BRCA1/2 mutation and 5 with a CHEK2 mutation. The confirmed PSA50 response rate to rucaparib was 41.7% (N = 5/12, 95% CI: 15.2-72.3%, one-sided P = .81 against the 50% null), which did not meet the pre-specified efficacy boundary to enroll additional patients. In patients with measurable disease, the objective response rate was 60% (N = 3/5), all with a BRCA2 mutation. The median radiographic progression-free survival on rucaparib was estimated at 12.0 months (95% CI: 8.0-NR months). The majority of adverse events were grade ≤2, and expected. Rucaparib can induce clinical responses in a biomarker-selected metastatic prostate cancer population without concurrent ADT. However, the pre-specified efficacy threshold was not met, and enrolment was truncated. Although durable responses were observed in a subset of patients, further study of PARPi treatment without ADT in mHSPC is unlikely to change clinical practice.

Abstract CT087: A phase 1/2, open-label, randomized, dose-finding and dose expansion study of gedatolisib in combination with darolutamide in metastatic castration-resistant prostate cancer (mCRPC)

Abstract Background: Progression to metastatic castration-resistant prostate cancer (mCRPC) occurs in most patients treated with androgen receptor signaling inhibitors (ARSi) for advanced disease. Preclinical studies demonstrate that AR and PI3K - AKT - mTOR (PAM) pathways interact through reciprocal negative feedback, whereby inhibition of one pathway activates the other. Thus, combining a PAM inhibitor with an ARSi may deliver improved anti-cancer activity in patients with mCRPC. A Phase 2 trial in 129 patients with mCRPC who progressed on abiraterone demonstrated improved median radiographic progression-free survival (rPFS) when samotolisib, a dual PI3K-mTOR inhibitor, was added to enzalutamide. These results form the basis for this clinical trial of gedatolisib, a potent PAM inhibitor, in combination with darolutamide in men with mCRPC who have previously progressed on ARSi (NCT06190899). Methods: This open-label, multicenter, Phase 1/2 study will evaluate the safety and efficacy of gedatolisib in combination with darolutamide in men with mCRPC who have progressed on ARSi. In Phase 1, 36 patients will be randomized to one of two dose arms to evaluate dose limiting toxicities (DLTs) and determine the recommended Phase 2 dose (RP2D). Gedatolisib will be administered once weekly for 3-weeks-on/1-week-off: Arm 1 - 120 mg and Arm 2 - 180 mg, with darolutamide 600 mg orally administered twice daily. Arm 2 may be dose de-escalated depending on the number of DLTs observed. In Phase 2, 12 additional patients will be enrolled at the RP2D (n= 30). Key inclusion criteria include adult males (≥ 18 years) with mCRPC who have progressed on or after treatment with one next-generation ARSi. Key exclusion criteria include males with adenocarcinoma with a small cell component and with ≥10% neuroendocrine type cells; prior treatment with PI3K, AKT, or mTOR inhibitor; prior chemotherapy or radiopharmaceutical therapy for mCRPC; uncontrolled type 1/2 diabetes; or active brain or leptomeningeal metastases. Primary endpoints for Phase 1 are safety and tolerability (incidence of DLTs, adverse events, and determination of maximum tolerated dose) determination of the recommended Phase 2 dose (RP2D), PK, and Bayesian Optimal Interval utility score. Primary endpoints for Phase 2 are rPFS rate at 6 months based on Response Evaluation Criteria in Solid Tumors (RECIST) v1.1 with modifications as specified in Prostate Cancer Working Group 3 criteria. Secondary endpoints include rPFS rates at 9 and 12 months, overall rPFS, prostate-specific antigen response of ≥50% decrease from baseline at 4, 8, 12, and 16 weeks, overall response rate, duration of response, clinical benefit rate, overall survival rate at 18 and 24 months, and safety. The trial is currently open for enrollment. Citation Format: Adam Sharp, Alice Bernard-Tessier, Delphine Borchiellini, Johann de Bono, Karim Fizazi, Gwenaelle Gravis, David Lorente, Hakim Mahammedi, Begona Mellado, David Olmos, Simon Pacey, Jose Piulats, Sara P. Ramirez, Igor Gorbatchevsky, Elisabeth Heath. A phase 1/2, open-label, randomized, dose-finding and dose expansion study of gedatolisib in combination with darolutamide in metastatic castration-resistant prostate cancer (mCRPC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT087.

The efficacy and safety of tinengotinib in patients with heavily pretreated metastatic castration-resistant prostate cancer (mCRPC).

133 Background: Tinengotinib is a spectrum-selective multi-kinase inhibitor that targets cell proliferation, angiogenesis, and immune-oncology pathways by inhibiting Aurora kinases A/B, Janus kinases (JAK), and receptor tyrosine kinases (FGFRs, VEGFRs). It has been reported that the activation of JAK/STAT and fibroblast growth factor receptor (FGFR) signaling drives prostate tumor plasticity. Here we present the preliminary safety and efficacy data of tinengotinib in patients with mCRPC from three early phase clinical trials conducted in the US and China. Methods: Eligible mCRPC patients who have no available standard therapeutic treatment options were enrolled to the three studies. Tinengotinib was given as monotherapy at 8 mg QD, 10 mg QD and 12 mg QD. Efficacy tumor assessments were based on RECIST v1.1 for measurable disease and Prostate Cancer Working Group 3 criteria for non-measurable (bone) disease. PSA50 response was also evaluated. CTCAE v5.0 was used for safety assessments. Results: As of 28AUG2023, 30 patients with mCRPC were treated at dose levels of 8 mg QD (n=1), 10 mg QD (n=19) and 12 mg QD (n=10). Median age was 67 years (range 52-82) with ECOG performance status of 1 in 93% of patients. All patients had at least 2 prior therapies including 77% prior docetaxel, 87% prior abiraterone, and 30% prior enzalutamide. The median follow-up time is 5.4 months. Twenty-two (22) patients were efficacy evaluable, of which 13 were evaluable per RECIST v1.1. Fourteen (14) patients were PSA evaluable. The median radiographic progression-free survival (rPFS) was 5.6 months (95% CI, 3.3-7.3). Overall response rate (ORR) was 46% (6/13) and the disease control rate (DCR) was 85% (11/13). Median duration of response (DoR) was 3.0 months. The PSA50 response rate was 50% (7/14). Treatment-related adverse events (TRAEs) occurred in 28 patients (93%). The most common TRAEs (≥20%) included blood thyroid stimulating hormone increase (43%), anemia (37%), hypertension (27%), aspartate aminotransferase increase (23%), electrocardiogram QT prolongation (20%) and white blood cell count decrease (20%). Conclusions: Tinengotinib safety profile was tolerable and manageable. The preliminary efficacy data showed promising clinical benefit of tinengotinib monotherapy in patients with heavily pretreated mCRPC. Further study of tinengotinib in this disease is warranted. Clinical trial information: NCT03654547 , NCT04742959 , NCT05253053 .

Enfortumab vedotin (EV) as monotherapy in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC): Results of stage I of a phase 2 trial.

152 Background: EV is an antibody-drug conjugate consisting of a fully human antibody directed against the extracellular domain of Nectin-4, which is conjugated to a microtubule-disrupting agent, monomethyl auristatin E (MMAE) by a protease-cleavable linker. In animal models of prostate cancer, metastatic lesions showed high membranous Nectin-4 expression (PMID: 30767361). We aimed to investigate EV in pts with mCRPC. Methods: This IRB-approved, investigator-initiated, single-arm, single-center, phase 2 study administered EV at 1.25 mg/kg IV on days 1, 8, and 15 of 28 days cycle. Key eligibility criteria: ≥18 years age, mCRPC with histologically/cytologically confirmed adenocarcinoma without small cell histology, performance status ≤ 1, adequate organ function, prior treatment (Rx) with ≥3 cycles of docetaxel and at least one androgen-receptor pathway inhibitor, received/refused all therapies shown to improve overall survival except cabazitaxel which is exclusionary. Primary objective: To assess antitumor activity of EV as determined by one of the following: 1) objective response by RECIST 1.1 in those with measurable disease, 2) confirmed conversion of circulating tumor cell count (CTC) to &lt;5/7.5 mL blood, 3) PSA decline of ≥ 50%, and 4) stable disease for ≥ 6 months per PCWG3 modified RECIST 1.1. Simon’s two-stage design was used. The null hypothesis (H0) that true response rate (RR) is 25% is tested against a one-sided alternative. In stage I if ≤3 responses were observed of 11 pts, the study will be stopped. Otherwise, 23 additional pts will be accrued (total 34). H0 will be rejected if ≥13 responses are observed in 34 pts (type I error rate 0.046, power 0.854 when true RR is 50%). Results: Herein, we present results of 11 pts treated on stage I of study. All pts were non-Hispanic white with median age of 72 years (range 43-78). Median number of prior systemic therapies in addition to castration: 5 (range 3-8). Median follow-up of the cohort was 9 months (range 1-13). 4/11 had RECIST measurable disease and 7/11 had CTC ≥5 at baseline. Overall 7/11 (64%) pts had protocol-defined response (5/11 PSA 50% responses, 3/4 objective response, 4/7 confirmed CTC response and 2/11 ≥ 6 months on Rx). Of the 9 pts who discontinued Rx, 8 discontinued due to disease progression (1 withdrew consent). Median number of completed cycles were 6 (range: 2-12) and median radiographic progression-free survival was 5.5 months (95% CI 5.3-not reached). Most common grade 3/4 treatment-related adverse events (TRAEs) were anemia, AST increase, dry skin, fatigue, hyperglycemia, rash, leucopenia (1 pt each) and nausea and decrease in neutrophil (2 pts each). 8 pts had dose interruptions and dose reductions. No Grade 5 TRAEs. Conclusions: EV showed promising efficacy and an acceptable safety profile in pts with heavily treated refractory mCRPC. Further enrollment in stage 2 of the trial is ongoing. Clinical trial information: NCT04754191 .

Concomitant antihypertensive medication and outcome of patients with metastatic castration-resistant prostate cancer receiving enzalutamide or abiraterone acetate.

The introduction of novel hormonal therapies represented by enzalutamide (ENZ) and abiraterone acetate (ABI) has reached a great progress in the treatment of metastatic castration-resistant prostate cancer (mCRPC). The majority of mCRPC patients are elderly suffering from chronic co-morbidities requiring use of various concomitant medications. In the present study, we focused on impact of concomitant antihypertensive medication on the outcomes of mCRPC patients treated with ENZ or ABI. In total, 300 patients were included and their clinical data were retrospectively analyzed. Angiotensin-converting enzyme inhibitors (ACEIs) represented the only concomitant medication significantly associated with survival. The median radiographic progression-free survival (rPFS) and overall survival (OS) for patients using ACEIs were 15.5 and 32.3 months compared to 10.7 and 24.0 months for those not using ACEIs (p = 0.0053 and p = 0.0238, respectively). Cox multivariable analysis revealed the use of ACEIs a significant predictive factor for both rPFS (HR = 0.704, p = 0.0364) and OS (HR = 0.592, p = 0.0185). The findings of this study suggest an association between the concomitant use of ACEIs and longer survival of mCRPC patients receiving ENZ or ABI therapy.

Promising Therapeutic Activity of 177 Lu-PSMA-617 in Synchronous High-Volume Metastatic Hormone-Sensitive Prostate Cancer : A Pilot Experience.

177 Lu-PSMA-617 has been shown to improve survival outcomes in patients with end-stage metastatic castration-resistant prostate cancer. However, data in earlier lines remain limited. In this study, we intended to evaluate the efficacy and safety of 177 Lu-PSMA-617 in patients with synchronous high-volume metastatic hormone-sensitive prostate cancer (mHSPC). Hormone-sensitive prostate cancer patients with synchronous high-volume metastases (defined as ≥4 skeletal metastases with ≥1 extra-axial site or any visceral metastasis) showing high PSMA expression on 68 Ga-PSMA-11 PET/CT and ineligible/unwilling for conventional chemohormonal treatment options were selected. Approximately, ~5.55-7.4 GBq of 177 Lu-PSMA-617 was administered intravenously at 8-12 weeks intervals, up to 6 cycles. All patients underwent concomitant androgen deprivation therapy/orchiectomy. The outcome measures included the proportion of patients achieving an undetectable serum prostate-specific antigen (PSA) (ie, ≤0.2 ng/mL) at any time point after therapy, best PSA response rate, objective radiographic response rate, radiographic progression-free survival, overall survival, and adverse events. Ten patients with high-volume mHSPC received a median cumulative activity of 32.4 GBq (range, 7.4-44.4) of 177 Lu-PSMA-617 over 1-6 cycles. Five patients (50%) achieved an undetectable PSA with 9 patients (90%) showing a ≥50% decline in PSA from baseline. Nine patients underwent radiological follow-up, of which 7 (77.8%) had an objective response. The median radiographic progression-free survival was 24 months (95% confidence interval, 18-30), whereas the median overall survival was not reached. None of the patients had any grade 3/4 adverse event. 177 Lu-PSMA-617 seems to be a promising efficacious and safe treatment option for patients with synchronous high-volume mHSPC.

Phase 2 trial of a DNA vaccine (pTVG-HP) and nivolumab in patients with castration-sensitive non-metastatic (M0) prostate cancer

PurposeWe have previously reported that a plasmid DNA vaccine encoding prostatic acid phosphatase (pTVG-HP) had greater clinical activity when given in combination with pembrolizumab to patients with metastatic, castration-resistant prostate...

Phase II Trial Evaluating Olaparib Maintenance in Patients with Metastatic Castration-Resistant Prostate Cancer Responsive or Stabilized on Docetaxel Treatment: SOGUG-IMANOL Study.

The SOGUG-IMANOL trial was a phase 2, uncontrolled, Spanish multicenter study to assess the effect of maintenance treatment with olaparib on radiographic progression-free survival (PFS) in patients with metastatic castration-resistant prostate cancer (mCRPC) who achieved partial or complete response or disease stabilization on docetaxel treatment and had a documented germline/somatic mutation in any of the homologous recombination repair (HRR) genes. Patients received olaparib 300 mg orally twice daily. From the screened population (n = 134), 26 (19.4%) somatic mutations were found, and 14 patients were included in the study. The median radiographic PFS was 11.1 (95%CI, 5.7 to 16.5) months. The median PSA-PFS was 3.5 (95%CI, 1.0 to 6.0) months, and the median clinical PFS was 14.7 (95%CI, 1.8 to 27.5 months). Clinical benefit was observed in 12 patients (85.7%, 95%CI 67.4% to 100%), including two patients with partial response and 10 with stable disease. Six patients reported grade 3-5 adverse events: asthenia (n = 3), anemia (n = 2) and neutropenia (n = 1). In this setting, olaparib has been shown to be an efficacious maintenance treatment in terms of radiographic PFS and clinical benefit, becoming a therapeutic option for some patients harboring an HRR gene mutation and in scenarios where further investigation is needed.

A Phase Ib, Open-label Study Evaluating the Safety and Efficacy of Ipatasertib plus Rucaparib in Patients with Metastatic Castration-resistant Prostate Cancer.

To report the safety and efficacy of ipatasertib (AKT inhibitor) combined with rucaparib (PARP inhibitor) in patients with metastatic castration-resistant prostate cancer (mCRPC) previously treated with second-generation androgen receptor inhibitors. In this two-part phase Ib trial (NCT03840200), patients with advanced prostate, breast, or ovarian cancer received ipatasertib (300 or 400 mg daily) plus rucaparib (400 or 600 mg twice daily) to assess safety and identify a recommended phase II dose (RP2D). A part 1 dose-escalation phase was followed by a part 2 dose-expansion phase in which only patients with mCRPC received the RP2D. The primary efficacy endpoint was prostate-specific antigen (PSA) response (≥50% reduction) in patients with mCRPC. Patients were not selected on the basis of tumor mutational status. Fifty-one patients were enrolled (part 1 = 21; part 2 = 30). Ipatasertib 400 mg daily plus rucaparib 400 mg twice daily was the selected RP2D, received by 37 patients with mCRPC. Grade 3/4 adverse events occurred in 46% (17/37) of patients, with one grade 4 adverse event (anemia, deemed related to rucaparib) and no deaths. Adverse events leading to treatment modification occurred in 70% (26/37). The PSA response rate was 26% (9/35), and the objective response rate per Response Criteria in Solid Tumors (RECIST) 1.1 was 10% (2/21). Median radiographic progression-free survival per Prostate Cancer Working Group 3 criteria was 5.8 months [95% confidence interval (CI), 4.0-8.1], and median overall survival was 13.3 months (95% CI, 10.9-not evaluable). Ipatasertib plus rucaparib was manageable with dose modification but did not demonstrate synergistic or additive antitumor activity in previously treated patients with mCRPC.

First-in-human, phase 1 study of PF-06753512, a vaccine-based immunotherapy regimen (VBIR), in non-metastatic hormone-sensitive biochemical recurrence and metastatic castration-resistant prostate cancer (mCRPC)

BackgroundThis phase 1 study evaluated PF-06753512, a vaccine-based immunotherapy regimen (PrCa VBIR), in two clinical states of prostate cancer (PC), metastatic castration-resistant PC (mCRPC) and biochemical recurrence (BCR).MethodsFor dose escalation,...

Enzalutamide or Abiraterone Acetate With Prednisone in the Treatment of Metastatic Castration-resistant Prostate Cancer in Real-life Clinical Practice: A Long-term Single Institution Experience.

Enzalutamide (ENZ) and abiraterone acetate with prednisone (AAP) represent novel hormonal therapies used in the treatment of metastatic castration-resistant prostate cancer (mCRPC). The aim of the study was to assess the long-term outcome of mCRPC patients treated with ENZ or AAP in real-life clinical practice. The outcomes of 337 mCRPC patients treated with ENZ or AAP were retrospectively analysed. Median radiographic progression-free (rPFS) and overall survival (OS) of patients treated in the first line (pre-chemotherapy) was 13.89 (95% CI=12.40-16.80) and 31.02 (95% CI=24.27-37.44) months vs. 10.97 (95% CI=8.97-14.82) and 26.57 (95% CI=15.97-33.92) months for those treated in the second line (post-chemotherapy). We found inferior survival for patients with synchronous metastases, high Gleason score (GS) and visceral metastases. The efficacy of both ENZ and AAP in mCRPC patients is herein confirmed. Synchronous metastases, high GS and visceral metastases were identified as significant adverse prognostic factors.

Abstract 4133: High prevalence and heterogeneity of emergence of BRCA reversion mutations at progression on niraparib treatment in BRCA-mutant metastatic castration-resistant prostate cancer (mCRPC) patients

Abstract In the phase 2 GALAHAD study (NCT02854436), the PARP inhibitor (PARPi) niraparib, was evaluated in heavily pre-treated patients with mCRPC and DNA-repair gene defects (DRD) who progressed after androgen-receptor (AR) targeted therapy and taxane-based chemotherapy. The results showed that objective response rate (ORR) was 34.2% for patients with measurable disease having biallelic BRCA1/2 alterations (n=76). The development of BRCA reversion mutations, a type of secondary mutation that restores protein function, has been proposed as a key resistance mechanism to PARP inhibition. We aimed to evaluate the relationship between reversion mutations and treatment response in BRCA1/2 altered patients treated with niraparib in the GALAHAD study. Thirty-three patients with biallelic BRCA alterations (excluding patients with homozygous deletions) had donated an end-of-treatment (EOT) ctDNA sample. We performed sequencing to detect reversion mutations using the Resolution Bioscience ctDx-HRD assay. Mutation patterns at baseline included splice site, nonsense, missense, and frameshift mutations, with the latter being the most common (24/33; 73%). No reversions were detected at baseline and the baseline BRCA alterations were detected at EOT for every patient. Most BRCA patients (28/33; 85%) had at least 1 reversion mutation (range: 1-38 different BRCA alterations) at EOT. Of the 28 patients with reversions, 5 were classified as low reversions: 3 patients had only one reversion mutation, 1 patient had 2 reversions at low allele frequency and 1 patient had 4 reversions at low allele frequency. Patients with reversion mutations showed better composite response (defined as ORR by RECIST 1.1, or CTC conversion to &amp;lt;5/7.5 mL blood, or ≥50% decline in prostate specific antigen) (74.2% vs 25.8%, p=0.01) and longer duration on treatment (median 6.9 vs 3.7 mo, p&amp;lt;0.05) compared to those without or low reversions. Additionally, patients with reversions trended to have longer median radiographic progression-free survival compared to those without or low reversions (8.1 vs 5.5 mo, p=0.12). In conclusion, the high prevalence of patients with BRCA reversion mutations and the displayed longer benefit from niraparib underscores the dependence of these tumors on BRCA mutation as an oncogenic driver and reversion mutations as a marker of secondary resistance to niraparib treatment. Citation Format: Karen Urtishak, Gerhardt Attard, Tokuwa Kanno, Shibu Thomas, Gary E. Mason, Byron Espina, Eugene Zhu, Natalie Hutnick, Mary Guckert, Adam del Corral, Mark Li, Angela Lopez-Gitlitz, Kim Chi, William Kevin Kelly, Evan Y. Yu, Karim Fizazi, Matthew Smith. High prevalence and heterogeneity of emergence of BRCA reversion mutations at progression on niraparib treatment in BRCA-mutant metastatic castration-resistant prostate cancer (mCRPC) patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4133.

Phase 3 VERACITY clinical study of sabizabulin in men with metastatic castration-resistant prostate cancer who have progressed on an androgen receptor targeting agent.

TPS5102 Background: Sabizabulin is a first-in-class, oral agent that inhibits microtubule polymerization disrupting the cytoskeleton and arresting cellular proliferation. A Phase 1b/2 clinical study was conducted to establish the MTD and evaluate the preliminary efficacy in men with metastatic castrate resistant prostate cancer (mCRPC) who progressed on at least one androgen receptor targeting agent (ARTA). The most common AEs reported were mild to moderate diarrhea, fatigue, nausea, and vomiting with no clinically relevant neurotoxicity or neutropenia. In the Phase 1b/2, the median radiographic progression free survival for the 63mg dose (n = 55) was 11.4 months (range 6-36+ months) in the Phase 1b portion including responses &gt; 2.75 years. The Phase 3 reformulation which had improved bioavailability is 32mg PO qd. Methods: VERACITY is an ongoing Phase 3 multicenter, randomized, active-control study designed to evaluate sabizabulin in the treatment of mCRPC who have progressed on at least one ARTA. Patients on the study will be chemotherapy naive. Subjects (n = 245) are being randomized in a 2:1 ratio to receive sabizabulin (32 mg/d oral) or active control (alternative ARTA) and will remain on study until radiographic progression-free survival (rPFS). Randomization will be stratified by: measurable disease vs bone-only disease and by prior exposure to ARTA (progressed on one vs more than one prior ARTA). The primary efficacy endpoint of the study is median rPFS. Secondary endpoints include: objective response rate (ORR), duration of objective response, overall survival and time to intravenous (IV) chemotherapy. The Phase 3, VERACITY registration clinical trial is current ongoing in approximately 45 clinical sites with enrollment anticipated to be completed in 2022 and with unblinded results presented in 2023 Based upon the Phase 1b/2 clinical trial, sabizabulin daily chronic oral dosing has a favorable safety profile, is feasible to administer chronically, and has significant and durable antitumor activity. mCRPC that has progressed following ARTAs and prior to taxane chemotherapy, remains an urgent unmet medical need for patients with advanced disease. Sabizabulin is an exciting first-in-class agent that may add to the armamentarium for the treatment of mCRPC following progression on ARTA’s. Clinical trial information: NCT04844749.

Tolerability of abiraterone (abi) combined with olaparib (ola) in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC): Further results from the phase III PROpel trial.

5019 Background: The Phase III PROpel (NCT03732820) trial demonstrated at interim analysis a statistically significant clinical benefit from combining ola + abi in the first-line (1L) mCRPC setting vs placebo (pbo) + abi. Benefit was seen irrespective of a pt’s homologous recombination repair mutation (HRRm) status; median radiographic progression-free survival (rPFS) 24.8 for ola + abi vs 16.6 months for pbo + abi (hazard ratio [HR] 0.66, 95% confidence interval [CI] 0.54–0.81; P&lt;0.0001). The safety profile of ola + abi was shown to be consistent with that for the individual drugs. We report additional interim safety analysis from PROpel. Methods: Eligible pts were ≥18 years with mCRPC, had received no prior chemotherapy or next-generation hormonal agent treatment at mCRPC stage, and were unselected by HRRm status. Pts were randomized 1:1 to abi (1000 mg qd) plus prednisone/prednisolone with either ola (300 mg bid) or pbo. Primary endpoint was investigator-assessed rPFS. Safety was assessed in all pts receiving ≥1 dose of study treatment by adverse event (AE) reporting (CTCAE v4.03). Results: 398 pts received ola + abi and 396 pbo + abi (safety analysis set). At data cut-off (July 30, 2021), median total duration of exposure for ola was 17.5 vs 15.7 months for pbo, and for abi 18.2 months in the ola + abi arm and 15.7 in the pbo + abi arm. Anemia (n=183) was the most common AE in the ola + abi arm, and 34% of these 183 events were managed by dose interruption, 23% by dose reduction, and 8% resulted in treatment discontinuation. Anemia and pulmonary embolism (PE) were the only Grade ≥3 AEs in ≥5% of pts (anemia: ola + abi, 15.1% vs pbo + abi, 3.3%; PE: 6.5% vs 1.8%, respectively). Most PEs were detected incidentally on radiographic imaging (69.2% and 71.4% in the ola + abi and pbo + abi arms, respectively) and no pts discontinued. More pts in the ola + abi arm experienced venous thromboembolism (Table). Arterial thromboembolism and cardiac failure AEs were balanced between the treatment arms. No AE of myelodysplastic syndrome/acute myeloid leukemia was reported in either treatment arm. COVID-19 was reported more frequently with ola + abi (8.3% vs 4.5%). Conclusions: PROpel demonstrated a predictable safety profile for ola + abi given in combination to pts with 1L mCRPC unselected by HRRm status. AEs of cardiac failure and arterial thromboembolism were reported at similar frequency in both treatment arms. The majority of PEs were asymptomatic. The safety profile of abiraterone was not adversely impacted by its combination with olaparib. Clinical trial information: NCT03732820. [Table: see text]

Final analysis of the phase 1b/2 study of sabizabulin in men with metastatic castration-resistant prostate cancer who progressed on an androgen receptor targeting agent.

5049 Background: Sabizabulin is a novel oral cytoskeleton disruptor being developed for use in metastatic castration resistant prostate cancer (mCRPC). A Phase 1b/2 clinical study was conducted to establish the maximum tolerated dose (MTD) and evaluate the preliminary efficacy in men with mCRPC resistant to androgen receptor targeting agents. Methods: The Phase 1b portion of the study in 39 men utilized escalating and expanding dose and duration. The Phase 2 portion studied 41 men with mCRPC at the recommended Phase 2 dose of 63 mg daily. Efficacy was assessed by bone/CT scans. A final analysis of the safety and efficacy data including the primary endpoint, the median progression-free survival was conducted. Results: Although the MTD was not reached in the Phase 1b, the recommended Phase 2 dose was set at 63 mg/day to maximize GI tolerability. The most common adverse events (&gt; 10% frequency) at the 63 mg oral daily dosing (combined Phase 1b/2 data) were predominantly Grade 1-2. Grade ³3 events included diarrhea (7.4%), fatigue (5.6%) and ALT/AST elevations (5.6% and 3.7%, respectively). Neurotoxicity and neutropenia were not observed. Preliminary efficacy data in patients treated with ≥1 continuous cycle (21 days) of 63 mg or higher (n = 55) included an objective response rate of 6/29 (20.7%) in patients with measurable disease (1 complete, 5 partial). 14/48 (29.2%) of the patients had PSA declines. The Kaplan-Meier median radiographic progression-free survival was estimated to be 11.4 months (95% C.I. 29.63-65.79) (n = 55). Durable responses lasting &gt; 2.75 years were observed with 14.5% (8/55) demonstrating a response greater than 12 months. Conclusions: This clinical trial demonstrated that chronic oral daily dosing of sabizabulin has a favorable safety profile with significant preliminary cytotoxic and cytostatic antitumor activity. These data support the ongoing Phase 3 VERACITY trial of sabizabulin in men with mCRPC who have progressed on an androgen receptor targeting agent. Clinical trial information: NCT03752099.

Molecular and Clinical Characterization of Patients With Metastatic Castration Resistant Prostate Cancer Achieving Deep Responses to Bipolar Androgen Therapy.

Bipolar androgen therapy (BAT) is an emerging treatment strategy for men with metastatic castration resistant prostate cancer (mCRPC) whereby serum testosterone is cycled from supraphysiologic to near-castrate levels each month. BAT has been shown to induce clinical responses in a significant proportion of patients, some of which are extreme. We explored the clinical and molecular characteristics of patients with mCRPC who achieved deep responses to BAT. We conducted a retrospective analysis of patients with mCRPC treated with BAT at Johns Hopkins. We identified 22 of 114 (19%) patients with mCRPC who achieved ≥70% PSA reductions upon treatment with BAT. All patients were treated using 400 mg testosterone cypionate intramuscularly every 28 days, together with continuous LHRH agonist therapy. Clinical-grade DNA sequencing was obtained using commercially available assays. Somatic next-generation sequencing was obtained for 15 of 22 (68%) patients. Of these 15 extreme PSA responders with sequencing data available, All 15 of 15 (100%) harbored a pathogenic mutation in TP53 and/or a homologous recombination DNA repair (HRD) gene. Among the subset of patients with measureable disease (N=15), 10 patients (67%) achieved an objective response including one patient with a complete response. The median radiographic progression-free survival of these deep PSA responders was 11.3 months (95% CI, 7.9-25.0 months). We observed an enrichment of TP53 and HRD mutations in mCRPC patients with extreme PSA responses to BAT, with durability lasting about a year. These data support the hypothesis that BAT may most benefit patients with DNA repair-deficient mCRPC. Further studies of BAT in biomarker-selected mCRPC populations (ie, TP53/HRD-mutated) are warranted.

Phase 3 VERACITY clinical study of sabizabulin in men with metastatic castrate resistant prostate cancer who have progressed on an androgen receptor targeting agent.

TPS217 Background: Sabizabulin is a first-in-class, oral agent that inhibits microtubule polymerization disrupting the cytoskeleton and arresting cellular proliferation. In prostate cancer, targeted inhibition of microtubule polymerization further blocks the transport of the androgen receptor into the nucleus. A phase 1b/2 clinical study was conducted to establish the MTD and evaluate the preliminary efficacy in men with metastatic castrate resistant prostate cancer (mCRPC) who progressed on at least one androgen receptor targeting agent (ARTA). The most common AEs reported were mild to moderate diarrhea, fatigue, nausea, and vomiting with no clinically relevant neurotoxicity or neutropenia. In the phase 1b/2, in all evaluable patients that would qualify for the VERACITY study (n=26), the ORR was 23.1%. Median radiographic progression free survival was &gt;12 months (range 6-28+ months) in the phase 1b portion including responses &gt;two years. The revised formulation for use in the Phase 3 study, with improved bioavailability, is 32mg PO qd. Methods: VERACITY is an ongoing phase 3 multicenter, randomized, active-control study designed to evaluate sabizabulin in the treatment of mCRPC who have progressed on at least one ARTA. Patients on the study will be chemotherapy naive. Subjects (n=245) are being randomized in a 2:1 ratio to receive sabizabulin (32 mg/d oral) or active control (alternative ARTA) and will remain on study until radiographic progression-free survival (rPFS). Randomization will be stratified by: measurable disease vs. bone-only disease and by prior exposure to ARTA (progressed on one vs more than one prior ARTA). The primary efficacy endpoint of the study is median rPFS. Secondary endpoints include: objective response rate (ORR), duration of objective response, overall survival and time to intravenous (IV) chemotherapy. The phase 3, VERACITY registration clinical trial is current ongoing in approximately 45 clinical sites with enrollment anticipated to be completed in 2022 and with unblinded results presented in 2023. Based upon the phase 1b/2 clinical trial, sabizabulin daily chronic oral dosing has a favorable safety profile, is feasible to administer chronically, and has significant and durable antitumor activity. Metastatic prostate cancer that has become refractory to newer generation ARTAs and prior to IV chemotherapy, remains an urgent unmet medical need for patients with advanced disease. Sabizabulin is an exciting first-in-class agent that will add to the armamentarium for the treatment of metastatic castration and ARTA resistant prostate cancer. Clinical trial information: NCT04844749.

Nivolumab plus docetaxel in patients with chemotherapy-naïve metastatic castration-resistant prostate cancer: results from the phase II CheckMate 9KD trial

BackgroundDocetaxel has immunostimulatory effects that may promote an immunoresponsive prostate tumour microenvironment, providing a rationale for combination with nivolumab (programmed death-1 inhibitor) for metastatic castration-resistant prostate cancer (mCRPC). MethodsIn the non-randomised, multicohort, global phase II CheckMate 9KD trial, 84 patients with chemotherapy-naive mCRPC, ongoing androgen deprivation therapy and ≤2 prior novel hormonal therapies (NHTs) received nivolumab 360 mg and docetaxel 75 mg/m2 every 3 weeks with prednisone 5 mg twice daily (≤10 cycles) and then nivolumab 480 mg every 4 weeks (≤2 years). The co-primary end-points were objective response rate (ORR) and prostate-specific antigen response rate (PSA50-RR; ≥50% decrease from baseline). ResultsThe confirmed ORR (95% confidence interval [CI]) was 40.0% (25.7–55.7), and the confirmed PSA50-RR (95% CI) was 46.9% (35.7–58.3). The median (95% CI) radiographic progression-free survival (rPFS) and overall survival (OS) were 9.0 (8.0–11.6) and 18.2 (14.6–20.7) months, respectively. In subpopulations with versus without prior NHT, the ORR was 38.7% versus 42.9%, the PSA50-RR was 39.6% versus 60.7%, the median rPFS was 8.5 versus 12.0 months and the median OS was 16.2 months versus not reached. Homologous recombination deficiency status or tumour mutational burden did not appear to impact efficacy. The most common any-grade and grade 3–4 treatment-related adverse events were fatigue (39.3%) and neutropenia (16.7%), respectively. Three treatment-related deaths occurred (1 pneumonitis related to nivolumab; 2 pneumonias related to docetaxel). ConclusionsNivolumab plus docetaxel has clinical activity in patients with chemotherapy-naïve mCRPC. Safety was consistent with the individual components. These results support further investigation in the ongoing phase III CheckMate 7DX trial. ClinicalTrials.gov registrationNCT03338790.

177Lu-PSMA Radioligand Therapy Is Favorable as Third-Line Treatment of Patients with Metastatic Castration-Resistant Prostate Cancer. A Systematic Review and Network Meta-Analysis of Randomized Controlled Trials.

In this systematic review and network meta-analysis (NMA), we aimed to assess the benefits and harms of third-line (L3) treatments in randomized controlled trials (RCTs) of patients with metastatic castration-resistant prostate cancer (mCRPC). Two reviewers searched for publications from 1 January 2006 to 30 June 2021. The review analyzed seven RCTs that included 3958 patients and eight treatments. Treatment with prostate-specific membrane antigen (PSMA)-based radioligand therapy (PRLT) resulted in a 1.3-times-higher rate of median PSA decline ≥50% than treatment with abiraterone, enzalutamide, mitoxantrone, or cabazitaxel (p = 0.00001). The likelihood was 97.6% for PRLT to bring about the best PSA response, out of the examined treatments. PRLT resulted in a 1.1-times-higher six-month rate of median radiographic progression-free survival. Treatment with PRLT in the VISION trial resulted in 1.05-times-higher twelve-month median overall survival than L3 treatment with cabazitaxel in other RCTs. PRLT more often resulted in severe thrombocytopenia and less often in severe leukopenia than did cabazitaxel. In conclusion, for patients with mCRPC, L3 treatment with PRLT is highly effective and safe.