FDA requests additional efficacy data for Dendreon's Provenge in advanced prostate cancer.

FDA requests additional efficacy data for Dendreon's Provenge in advanced prostate cancer.

Dendreon has received a complete response letter from the FDA requesting additional efficacy data for Provenge in advanced asymptomatic hormone refractory prostate cancer. This is particularly disappointing given the high unmet needs that remain for this indication coupled with the heightened anticipation that surrounds a potential approval of the first therapeutic cancer vaccine.
Provenge (sipuleucel-T) is an investigational product that may represent the first in a new class of active cellular immunotherapies that are uniquely designed to stimulate a patient's own immune system.

The application for Provenge was based on results from a randomized placebo-controlled phase III trial, which showed that patients with asymptomatic metastatic hormone refractory prostate cancer (HRPC) who received Provenge had a median survival time of 4.5 months longer than those in the placebo arm. The vaccine also demonstrated a 41% overall reduction in the risk of death. In addition, 34% of patients receiving Provenge were still alive 36 months after treatment compared to only 11% of patients randomized to receive placebo.

Prostate cancer is the third most common cancer worldwide. In the US alone, more than one million men have the disease, with an estimated 232,000 new cases diagnosed each year. More than 30,000 men die each year from prostate cancer. To date, no therapeutic cancer vaccine has achieved US approval and the fact that Provenge had received priority review status is a reflection of the high unmet need within the prostate cancer market.

The FDA's request was arguably unexpected, having acted against the recommendation of an advisory panel which voted 17-0 that the drug was safe, and 13-4 that the compound was substantially effective and should be approved. However, upon closer inspection, the outcome is less surprising. Much of the support for the drug came from the biologic and vaccine side of the FDA whereas regulators on the drug side of the agency, especially those who oversee review and approval of cancer drugs, were certainly more skeptical about Provenge.

It is difficult to speculate what Dendreon needs to do to get Provenge back on track and the company is currently seeking clarification about what type of data the FDA requires. If new data from an ongoing phase III trial is required, the vaccine may have to wait two to three years before approval is realized. With no precedent for approval of a cancer vaccine, and with increased potential competition from pipeline products, Dendreon is now unlikely to become the first company to bring a therapeutic cancer vaccine to market.