ASCO 2022: Phase 3 VERACITY Clinical Study of Sabizabulin in Men With Metastatic Castration-Resistant Prostate Cancer Who Have Progressed on an Androgen Receptor Targeting Agent

( At the 2022 American Society of Clinical Oncology Annual Meeting held in Chicago and virtually, the poster session focused on Prostate, Testicular, and Penile cancers on Monday afternoon included a presentation from Dr. Robert Dreicer describing the rationale, design, and protocol of the VERACITY trial examining sabizabulin in men with metastatic castration-resistant prostate cancer who have progressed on an androgen receptor targeting agent.

Treatment approaches in mCRPC have evolved substantially over the past decades, beginning with the introduction of docetaxel and transformed with subsequent data from trials of novel hormonal agents including abiraterone and enzalutamide. However, most patients still progress and die of disease so further treatment approaches have been sought.

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Sabizabulin is a first-in-class, oral agent that inhibits microtubule polymerization disrupting the cytoskeleton and arresting cellular proliferation. In a Phase 1b/2 clinical study establishing the MTD and preliminarily evaluating efficacy in men with metastatic castrate resistant prostate cancer (mCRPC) who progressed on at least one androgen receptor targeting agent (ARTA), treatment was relatiavely well tolerated. The most common AEs reported were mild to moderate diarrhea, fatigue, nausea, and vomiting with no clinically relevant neurotoxicity or neutropenia. In terms of efficacy, in this Phase 1b/2 study, the median radiographic progression free survival was 11.4 months (range 6-36+ months) for patients receiving a 63mg dose formulation (n = 55). Treatment has subsequently been reformulated with improved bioavailability. Thus, the Phase 3 is 32mg PO daily.

At this dosage, sabizabulin is being assessed in the treatment of patients with mCRPC who have progressed on at least one ARTA in the ongoing VERACITY trial, a Phase 3 multicenter, randomized, active-control study (NCT04844749). To be eligible for inclusion, patients must have received at least one ARTA for mCRPC but not have received chemotherapy. Enrolled patients are being randomized in a 2:1 fashion 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 a number of characteristics including RECIST measurable disease vs bone-only disease and by prior exposure to ARTA (progressed on one vs more than one prior ARTA).

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The primary efficacy endpoint of the study is median rPFS with a number of secondary endpoints including objective response rate (ORR), duration of objective response, overall survival, and time to intravenous (IV) chemotherapy.

The target enrollment is 245 patients and this trial is currently ongoing in approximately 45 clinical sites with enrollment anticipated to be completed in 2022 and with unblinded results presented in 2023.

The authors conclude that, sabizabulin is an exciting first-in-class agent that may add to the armamentarium for the treatment of mCRPC following progression on ARTAs, a disease space which remains an urgent unmet medical need.

Presented by: Robert Dreicer, MD, MS, MACP, FASCO is the Associate Director for Clinical Research and the Deputy Director of the University of Virginia Cancer Center. He serves as Section Head of Medical Oncology and Co-Director of the Paul Mellon Urologic Institute. He is a Professor of Medicine and Urology at the University of Virginia School of Medicine.

Written by: Christopher J.D. Wallis, University of Toronto, Twitter: @WallisCJD during the 2022 American Society of Clinical Oncology (ASCO) Annual Meeting, Chicago, IL, Fri, June 3 – Mon, June 7, 2022.

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