ESMO18: Clovis' Rubraca achieves 44 percent objective response rate in prostate cancer study

Clovis Oncology on Friday announced initial data from a Phase II study of Rubraca (rucaparib) in men with metastatic castration-resistant prostate cancer with BRCA gene alterations, with the PARP inhibitor achieving a 44 percent confirmed objective response rate (ORR). Results from the TRITON2 trial were presented at the European Society for Medical Oncology (ESMO) congress.

The study includes patients who had received prior treatment with at least one androgen receptor (AR)-directed therapy and taxane-based chemotherapy and were screened for a deleterious germline or somatic alteration in BRCA1, BRCA2 or one of 13 other pre-specified homologous recombination genes. Based on the type of gene alteration and disease status, subjects were grouped into three cohorts, with patients all receiving Rubraca twice daily.

The trial's primary endpoints include confirmed ORR in patients with measurable disease at baseline and prostate specific antigen (PSA) response in patients with no measurable disease at baseline. Meanwhile, secondary goals include overall survival, clinical benefit rate, and safety and tolerability.

As well as the confirmed ORR, which came from 25 response-evaluable patients with a BRCA1/2 alteration, results also showed that Rubraca was associated with a 51 percent confirmed PSA response rate in 45 PSA response-evaluable patients with a BRCA1/2 alteration. Findings from the study were used to support the FDA's recent decision to award the drug breakthrough therapy designation as a monotherapy treatment for adults with BRCA1/2-mutated metastatic castration-resistant prostate cancer who have received at least one prior AR-directed therapy and taxane-based chemotherapy.

"We are very encouraged by these initial findings," remarked CEO Patrick Mahaffy, confirming to FirstWord that the company plans to seek accelerated FDA approval of Rubraca based on Phase II results.

Rubraca gained FDA accelerated approval in 2016 for the treatment of patients with deleterious BRCA mutation associated advanced ovarian cancer who have been treated with two or more prior chemotherapies. Earlier this year, the agency expanded authorisation to include the maintenance treatment of adults with recurrent epithelial ovarian, fallopian tube, or primary peritoneal cancer who are in a complete or partial response to platinum-based chemotherapy. Rubraca was also cleared in Europe in May.

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