• Clovis Oncology’s shares have fallen by roughly 15% since the biotech disclosed the halting of a Phase 2 study of Rubraca in recurrent, metastatic bladder cancer. 
• The trial’s termination followed an independent committee’s review of preliminary data from the open-label monotherapy study, dubbed ATLAS, according to an April 12 company filing. The objective response rate failed to meet the protocol-defined continuance criteria in the intent-to-treat population, suggesting that Rubraca as a monotherapy might not provide a meaningful clinical benefit.
• Rubraca studies in combination with other agents are ongoing in advanced bladder cancer. A pan-tumor study of the PARP inhibitor in cancers with specific mutations is planned for the second half of 2019, which will include patients with advanced bladder cancer.

Clovis’ Rubraca (rucaparib) was given an accelerated approval in December 2016 for advanced and pretreated ovarian cancer. However, the Colorado-based biotech still lags behind the PARP inhibitor class leader, AstraZeneca.

The British pharma’s drug, Lynparza (olaparib), is approved for a number of indications in advanced ovarian cancer and metastatic breast cancer, helping its sales more than double in 2018 to $647 million. In comparison, Rubraca’s sales for last year came in at slightly below $100 million.

And while the drug found some success earlier this month in certain pancreatic cancer patients as a maintenance therapy, this discontinuation shows the limits of PARP inhibitors in unselected patient populations. Initial approvals for the drugs were for BRCA-mutated cancers. 

Clovis executives discussed the ATLAS study on the company’s last earnings call, following observations elsewhere that platinum-resistant ovarian cancer patients hadn’t responded to Rubraca treatment. 

“As far as I know, this is the first study of any decent size,” said Lindsey Rolfe, Clovis’ chief medical officer. “Indeed, the first study that’s fully devoted to bladder cancer and monotherapy PARP inhibition. So, in that respect, it’s a proof-of-concept study.”

Despite the discontinuation in bladder cancer, Clovis is pushing Rubraca forward. Enrollment is ongoing for trial in ovarian, breast and prostate cancer, among others.

The biotech is also conducting three combination studies with Bristol-Myers Squibb, combining the PARP inhibitor with Bristol-Myers Squibb’s immunoptherapy Opdivo (nivolumab).