Analysis of: FDA approves Dendreon's Provenge (sipuleucel-T)

Yesterday (29th April 2010), the FDA approved Dendreon's Provenge (sipuleucel-T) for the treatment of asymptomatic or minimally symptomatic, metastatic, castrate-resistant Prostate Cancer. Provenge is the first therapeutic vaccine to be approved for any oncology indication within the seven major markets. Although therapeutic vaccines have been notoriously challenging to develop in oncology, the approval of Provenge represents considerable opportunity and potential for other therapeutic vaccines in oncology indications.  Provenge will become the market sales leader in Prostate cancer owing to the high price and anticipated high patient demand.

Dendreon's Provenge has demonstrated a significant improvement in overall survival for asymptomatic or minimally symptomatic, metastatic, castrate-resistant prostate cancer patients a patient population with considerable unmet need because of the lack of currently available suitable therapies. This proven efficacy (although slight), coupled with a minimal toxicity profile, means that Provenge is a clinically attractive agent and is now the first targeted, personalized agent to be approved in Prostate Cancer.

The road to approval for Provenge has been turbulent and fraught with difficulty. Provenge was originally submitted to the FDA for approval in 2007 and gained a positive opinion from the Tissue and Gene Therapies Advisory Committee but was rejected for approval by the FDA. Positive overall survival data from the pivotal trial known as IMPACT (IMmunotherapy for Prostate AdenoCarcinoma Treatment) were required for the FDA to reconsider approval. In April 2009, Dendreon announced that Provenge had exceeded the requirements stipulated by the FDA in the IMPACT study. Provenge significantly improved overall survival by a median of 4.1 months compared with patients receiving a deactivated (freeze-thawed) version of Provenge and reduced the risk of death by 22.5%.

Despite significant improvements in overall survival, the median time to progression was not significantly improved. However, this lack of improvement may be a peculiarity of the mechanism of action of Provenge and other therapeutic vaccines. Provenge relies on activating patients immune systems; mounting of an immunological response against prostate cells does not result in an immediate clinical response, unlike some traditional cytotoxic chemotherapeutic approaches.  Nevertheless, Provenge improves overall survival and demonstrates the potential application of other therapeutic vaccines in prostate cancer.

Currently, asymptomatic, metastatic, castrate-resistant Prostate Cancer patients do not typically receive cytotoxic chemotherapy (specifically Taxotere [Sanofi-Aventis docetaxel]) unless they are progressing to symptomatic disease quickly. Therefore, Provenge will enter a patient population with minimal competition.

However, Provenge still faces challenges to widespread uptake in the United States. The high cost of this approach ($93,000 per course) and constraints of individualizing the manufacturing process will restrict blanket adoption. Several other therapeutic vaccines are also in development for Prostate Cancer, but remain in earlier stages of development. Based on the success of Provenge, these follow-on vaccines also have the potential to improve overall survival, although mature robust clinical data are currently lacking. Other competition to Provenge may lie in the novel hormonal agent, abiraterone (Johnson & Johnson), which is also being positioned as a potential therapy for asymptomatic or minimally symptomatic, metastatic, castrate-resistant Prostate Cancer.  Despite these challenges, owing to the high incidence of Prostate Cancer, the high price, reported efficacy, minimal toxicity, and anticipated high patient demand, we forecast that Provenge will become the market leading agent in Prostate cancer through 2019.

The pipeline of emerging therapies in Prostate Cancer is particularly rich, the approval of Provenge is just one therapy that will contribute to the dramatic change the treatment landscape of Prostate Cancer over the next decade.

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