An experimental vaccine called Provenge (sipuleucel-T) met is primary goal of extending survival compared to placebo in a phase 3 trial on men with advanced prostate cancer, according to a news release from its maker, the biotech company Dendreon Corp, which is based in Seattle, Washington, USA.

Provenge (sipuleucel-T) is intended to treat men with with androgen-independent prostate cancer, and according to the drug company, “may represent the first product in a new class of active cellular immunotherapies (ACIs)”. ACIs use live human cells to recruit the patient’s own immune system against the cancer.

Prostate cancer is the third most common cancer worldwide, with more than one million men affected in the US where every year there are about 186,000 new cases and over 28,000 men die because of the disease. There are very few treatments for advanced, metastatic prostate cancer.

Shares in the company soared ahead of the news, said a Reuters report, which described how analysts were caught unawares, since other vaccines have stumbled at the phase 3 stage.

The phase 3 trial was done after the Food and Drug Administration (FDA), against the recommendation of its advisory committee who recommended approval, said it would not approve the vaccine because there was not enough information on whether it prolonged survival, said a report in WebMD.

Dendreon are not releasing the results of the IMPACT study until a plenary session at the American Urological Association’s Annual Meeting in Chicago on Tuesday, 28th April, they said in a press statement.

At least one analyst remains sceptical and said his company is sticking with its bearish “sell” rating until the full results are revealed.

Jonathan Aschoff, an analyst at Brean Murray Carret & Co said in a research note that “we remain unconvinced until details are provided,” according to a Reuters news report.

The company’s press statement reported that:

“The magnitude of the survival difference observed in the intent to treat population resulted in the study successfully achieving the pre-specified level of statistical significance defined by the study’s design. The safety profile of PROVENGE appeared to be consistent with prior trials.”

The common adverse events reported for the vaccine in controlled trials included fever, chills, fatigue, shortness of breath, headache, vomiting and tremor. The effects were mostly low grade and lasted about 1 or 2 days after the vaccine was infused, said the statement.

IMPACT stands for IMmunotherapy for Prostate AdenoCarcinoma Treatment. The phase 3, multi-center, randomized, double blind, placebo controlled trial involved 512 men with metastatic, androgen-independent prostate cancer, and was carried out under a Special Protocol Assessment agreement with the FDA, said the company statement.

Company president and CEO, Dr Mitchell H Gold said the positive results of the trial confirm that Provenge prolongs survival and validates the long sought goal of getting the patient’s own immune system to fight the cancer.

“We are immensely grateful to our clinical investigators and the more than 1,000 men with advanced prostate cancer who have participated in our studies over the last decade and whose courage and contribution have significantly advanced the understanding and treatment of prostate cancer and the potential role of cancer immunotherapies,” said Gold.

The company said that in line with FDA requirements, it will amend its license application and file for approval in the fourth quarter of this year.

Sources: Dendreon news release, Reuters, WebMD.

Written by: Catharine Paddock, PhD