Will FDA advisers shoot down Amgen's cancer vaccine?

Amgen ($AMGN) has high hopes for its new cancer vaccine, barreling toward global approvals with positive data in melanoma. But a narrow miss on one key endpoint could present a major hurdle, and Amgen will soon get a chance to defend the treatment before a panel of FDA advisers.

Two of the agency's independent expert committees are slated to review talimogene laherparepvec (nicknamed T-Vec) on April 29, voting whether to recommend the vaccine for full approval. The FDA isn't required to follow the opinions of its advisers, but it most commonly does. The agency has promised to hand down a final decision on Amgen's candidate by Oct. 27.

Across its expansive Phase III program, T-Vec proved it could shrink tumors, keep them from regrowing and improve median survival. However, in late-stage results unveiled last year, the vaccine hit its primary endpoint of durable response in patients with metastatic melanoma but missed its second goal of boosting overall survival. But it was close, the company noted, pointing to a "trend" toward statistical significance with a p value of 0.051.

That's sure to come up when the agency's Cellular, Tissue and Gene Therapies and the Oncologic Drugs advisory committees pore over T-Vec's data. And while the issue is unlikely to derail Amgen's ambitions--the FDA has a well-established penchant for approving cancer treatments with much less supporting data than T-Vec--it could have a trickle-down effect on the drug's eventual value if and when it hits the market.

For its part, Amgen has stayed upbeat about the treatment's potential, standing by its results in monotherapy trials and heralding its promise as part of a cancer-killing cocktail. To that end, Amgen has launched a combo study pairing the virus with Bristol-Myers Squibb's ($BMY) top-selling melanoma treatment Yervoy, and the company has teamed up with Merck ($MRK) to study how well its drug can complement Keytruda, a PD-1 checkpoint inhibitor approved last year.

Amgen R&D chief Sean Harper

"The incidence of melanoma has continued to rise in recent years, and even with recent additional options in treatment, there is an important unmet medical need," Amgen R&D chief Dr. Sean Harper said in a statement. "We look forward to discussing the efficacy and safety profile of talimogene laherparepvec with the advisory committees, and we are committed to working closely with the FDA during its review of the BLA."

Amgen picked up T-Vec in its $1 billion deal for 2009 Fierce 15 honoree BioVex. The vaccine, a re-engineered herpes simplex virus, is designed to replicate itself within tumor cells until they burst, all the while stimulating an immune response against the cancer cells.

- read the statement

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