AZ, Merck's Lynparza narrowly snags FDA panel backing in pancreatic cancer

AstraZeneca and Merck are looking to make Lynparza the first PARP inhibitor approved in pancreatic cancer. (AstraZeneca)

AstraZeneca and Merck’s Lynparza is looking to become the first in its class of PARP inhibitors to break into the pancreatic cancer market. And a majority of FDA advisers thinks it should be—if only a small one.

Tuesday, the agency’s panel of experts voted 7-5 to approve Lynparza in the tough-to-treat disease. They based their decisions on data from the phase 3 Polo trial, which showed the drug could cut the risk of disease worsening or death by 47% in patients with germline BRCA-mutated pancreatic cancer who hadn’t progressed after an initial round of chemo.

It’s common for cancer drugs to win conditional approval based on progression-free survival data, without any evidence that they can extend lives; that often follows later, and, when it does, the FDA converts the approval into a full one.

RELATED: Is AZ, Merck's Lynparza approvable in pancreatic cancer sans survival benefit? FDA's about to decide

But this time, FDA staffers had some concerns, briefing documents revealed earlier this week. For one, they had misgivings about the trial’s small size. They also cited (PDF) the limitations of current imaging tech to accurately measure tumors as “another source of uncertainty.”

But as SVB Leerink analysts predicted earlier this week, the lack of treatment alternatives helped AstraZeneca and Merck’s case. No other approved products bear indications for gBRCA-mutated pancreatic cancer, and none are specifically cleared in the maintenance setting.

"While the positive vote was a narrow majority and several panelists expressed reservations about approving Lynparza based on the existing data, the majority of the panel (including three temporary voting members who specialize in GI diseases) determined that the benefits outweigh the risks, noting particularly durable responses (>2 years) in a subset of patients," SVB Leerink's Andrew Berens wrote in a Wednesday note to clients.

RELATED: ASCO: AZ, Merck's Lynparza fends off pancreatic cancer, cutting progression risk in half

Now, the final decision will be up to the FDA, which has said it’ll hand down a verdict by Dec. 28 after bestowing its priority review tag on Lynparza. While the agency doesn’t always follow recommendations from its committees, it typically does; Berens and his colleagues called a positive decision "more likely than not." 

A green light in pancreatic cancer would mark the third time Lynparza has led its class into a disease area, following its entries into the ovarian and breast cancer markets. And while pancreatic cancer "represents a relatively small fundamental opportunity (we model peak revenue ~$155mn in US and ~$50mn in EU), we believe this favorable AdCom and potential approval could create a 'halo effect' for Lynparza, perhaps making the drug the PARP inhibitor of choice for the majority of medical oncologists," Berens wrote.