- Clovis Oncology, trailing PARP inhibitor rivals AstraZeneca and Tesaro, aims to jump ahead in a new market for the targeted therapies, announcing Friday positive early data for its drug Rubraca in metastatic castration-resistant prostate cancer.
- Results from Clovis' TRITON2 study showed 11 of 25 previously treated patients responded to Rubraca, a finding that at least one analyst indicated exceeded initial expectations. Markets, however, seemed less sure, pushing Clovis stock down by nearly 2% Friday morning.
- AstraZeneca's Lynparza has so far outpaced Rubraca and Tesaro's Zejula in commercial sales, locking up a lead in the still-emerging PARP inhibitor drug class. All three drugs are approved in ovarian cancer, although Lynparza recently added an indication in breast cancer as well.
With positive data in hand, Clovis could have a shot at beating AstraZeneca and Tesaro in moving PARP inhibitor treatment into prostate cancer.
The results Clovis unveiled Friday supported the Food and Drug Administration's recent designation of Rubraca (rucaparib) as a Breakthrough Therapy in prostate cancer, and the biotech says it's committed to "rapid development" moving forward.
Leerink analyst Andrew Berens wrote in a Oct. 19 note that Clovis' data "suggest that an accelerated pathway in BRCA patients could be a possibility, if the duration of the responses at later analyses are compelling," referring to patients with a mutation in the BRCA gene.
Clovis won't be alone in reaching for a new indication, though. Tesaro confirmed on a second quarter earnings call that partner Janssen plans to advance its drug Zejula (niraparib) toward a regulatory filing in metastatic castration-resistant prostate cancer (mCRPC) next year.
AstraZeneca, meanwhile, is testing Lynparza (olaparib) for mCPRC in a Phase 3 trial called PROfound. Results are expected as early as 2019, with a supplemental New Drug Application slated to follow.
Clovis enrolled in the trial men with mCRPC and alterations in the BRCA gene or one of 13 other homologous recombination genes.
PARP inhibitors have found success in BRCA-mutated cancers by knocking out tumor cells' remaining DNA damage repair mechanism, thereby triggering cell death.
In the Clovis trial, while 85 patients have been treated to date, only 25 with BRCA 1/2 mutations were evaluable for tumor response assessment. Among all 45 patients in the study with those genetic alterations, 51% showed a prostate-specific antigen response — suggesting a lowered risk of disease progression.
Patients with BRCA 1/2 mutations represent about 13% of the prostate cancer market, Leerink's Berens estimates.
The analyst did note, however, that data wasn't available in patients with another type of genetic alteration called ATM.
"No quantitative efficacy data were provided for the 40 patients with ATM mutations, which are fundamentally important to assess the size of the opportunity," he wrote.
Clovis' results were announced ahead of their presentation this Sunday at the annual meeting of the European Society for Medical Oncology, taking place in Munich.
Earlier this week, U.S. regulators approved Pfizer's PARP inhibitor Talzenna for patients with BRCA-mutated HER2-negative locally advanced or metastatic breast cancer.