2754 - Preliminary results from the TRITON2 study of rucaparib in patients (pts) with DNA damage repair (DDR)-deficient metastatic castration-resistant prostate cancer (mCRPC): updated analyses

Background

Rucaparib has shown antitumour activity in pts with mCRPC and a deleterious DDR gene alteration. We present here updated analyses.

Methods

TRITON2 (NCT02952534) is an ongoing phase 2 study evaluating rucaparib 600 mg BID in pts with mCRPC and a deleterious germline or somatic alteration in BRCA1, BRCA2, ATM, CDK12, or other prespecified DDR gene. Eligible pts have progressed on 1–2 lines of androgen receptor–directed therapy and 1 line of taxane-based chemotherapy for mCRPC.

Results

As of 15 Feb 2019 (visit cutoff), 136 pts had received rucaparib and had ≥16 weeks of follow-up: 62 with a BRCA2 and 7 with a BRCA1 alteration (BRCA pts), 41 with an ATM alteration (ATM pts), 14 with a CDK12 alteration (CDK12 pts), and 12 with another DDR gene alteration (other DDR pts). Median duration of follow-up was 11.4 mo (range 4.0–24.0). PSA and objective response rates (ORR) were 53.6% and 47.5% in BRCA pts (Table). ORR in BRCA pts with somatic alterations was 56.5% (95% CI, 34.5–76.8; 13/23) and 40.0% (95% CI, 16.3–67.7; 6/15) in pts with germline alterations. Some ATM and CDK12 pts had a reduction in target lesion diameter (≥30% decrease in 3 ATM pts) or PSA level (≥50% decrease in 3 ATM pts and 2 CDK12 pts); however, no objective responses were observed in ATM or CDK12 pts, and only 1 ATM pt and 1 CDK12 pt had a confirmed PSA response. Median (95% CI) time to PSA progression was 6.5 (5.7–7.5) mo, 3.1 (2.8–4.6) mo, and 3.5 (2.8–4.6) mo in BRCA, ATM, and CDK12 pts. The most common grade ≥3 treatment-emergent adverse event was anaemia/decreased haemoglobin (16.2%).Table:

846PD

Includes 2 pts each with an alteration in FANCA, NBN, or PALB2 and 1 each with an alteration in BRIP1, BRIP1/CHEK2, CDK12/CHEK2, CHEK2, RAD51, or RAD51B.

Defined as confirmed complete or partial response per modified RECIST/PCWG3. Includes pts who had measurable disease at baseline per the investigator and ≥16 weeks of follow-up.

Responders include 1 pt each with a BRIP1, FANCA, PALB2, or RAD51B alteration.

Defined as ≥ 50% reduction in PSA from baseline. Includes pts who had ≥16 weeks of follow-up.

Responders include 2 pts with a PALB2 alteration and 1 pt each with a BRIP1, FANCA, or RAD51B alteration. CI, confidence interval; PSA, prostate-specific antigen.

Conclusions

Consistent with prior reports, rucaparib demonstrates promising efficacy in pts with mCRPC and a germline or somatic BRCA or other DDR gene alteration. No objective responses have been observed in pts with an ATM or CDK12 alteration. The safety profile of rucaparib is consistent with prior reports in ovarian and prostate cancer. Updated data will be presented.

Clinical trial identification

NCT02952534.

Editorial acknowledgement

Nathan Yardley, PhD, and Shannon Davis of Ashfield Healthcare Communications (Middletown, CT, USA), funded by Clovis Oncology, Inc. (Boulder, CO, USA).

Legal entity responsible for the study

Clovis Oncology, Inc.

Funding

Clovis Oncology, Inc.

Disclosure

W. Abida: Advisory / Consultancy, Research grant / Funding (institution), Travel / Accommodation / Expenses: Clovis Oncology, Inc.; Advisory / Consultancy: Janssen; Advisory / Consultancy: MORE Health; Advisory / Consultancy: ORIC Pharmaceuticals; Research grant / Funding (institution), Travel / Accommodation / Expenses: GlaxoSmithKline; Honoraria (self): Caret Healthcare; Research grant / Funding (institution): AstraZeneca; Research grant / Funding (institution): Zenith Epigenetics. A. Patnaik: Advisory / Consultancy: Janssen; Research grant / Funding (institution): Bristol-Myers Squibb; Research grant / Funding (institution): GlaxoSmithKline. J. Shapiro: Advisory / Consultancy, Travel / Accommodation / Expenses: Amgen; Advisory / Consultancy, Travel / Accommodation / Expenses: Merck; Advisory / Consultancy: Astellas Pharma, Inc.; Advisory / Consultancy: Ipsen; Advisory / Consultancy: Roche. N.J. Vogelzang: Advisory / Consultancy: Astellas Pharma, Inc.; Advisory / Consultancy: AstraZeneca; Advisory / Consultancy: Bayer; Advisory / Consultancy, Shareholder / Stockholder / Stock options: Caris; Advisory / Consultancy: Janssen; Advisory / Consultancy: Pfizer; Advisory / Consultancy: Sanofi Aventis. J. Zhang: Advisory / Consultancy, Speaker Bureau / Expert testimony, Research grant / Funding (institution): AstraZeneca; Advisory / Consultancy, Speaker Bureau / Expert testimony: Sanofi; Research grant / Funding (institution): Astellas Pharma, Inc.; Research grant / Funding (institution): Bayer. A.D. Simmons: Shareholder / Stockholder / Stock options, Employee: Clovis Oncology, Inc. D. Despain: Shareholder / Stockholder / Stock options, Employee: Clovis Oncology, Inc. M. Dowson: Shareholder / Stockholder / Stock options, Employee: Clovis Oncology, Inc. T. Golsorkhi: Shareholder / Stockholder / Stock options, Employee: Clovis Oncology, Inc. S. Chowdhury: Advisory / Consultancy, Speaker Bureau / Expert testimony, Research grant / Funding (institution): Clovis Oncology, Inc.; Advisory / Consultancy, Speaker Bureau / Expert testimony: Astellas Pharma, Inc.; Advisory / Consultancy, Speaker Bureau / Expert testimony, Research grant / Funding (institution): Janssen; Advisory / Consultancy, Speaker Bureau / Expert testimony: Pfizer; Advisory / Consultancy, Speaker Bureau / Expert testimony, Research grant / Funding (institution): Sanofi. All other authors have declared no conflicts of interest.