Dendreon researchers have presented data from the PROTECT (PROvenge Treatment and Early Cancer Treatment) or P-11 Phase 3 trial suggesting that sipuleucel-T (Provenge) induces durable responses that can be maintained following an immune boost. These early data from the PROTECT trial were presented Sunday at the annual meeting of the American Association for Cancer Research in Denver.
The PROTECT or P-11 study is a randomized, double-blind, placebo-controlled trial designed to evaluate the safety and biologic activity of sipleucel-T in men with non-metastatic, androgen-dependent prostate cancer who have had a PSA recurrence following surgical removal of the prostate. A total of 176 patients have been randomized to this study at 19 sites in the USA. Patients have been randomized two to one to receive sipleucel-T or placebo following a 3-month course of hormonal therapy.
Sipleucel-T or placebo was administered to patients at week 0, week 2, and week 4. A treatment booster infusion of sipluecel-T or placebo was offered after a confirmed PSA level ≥ 3.0 ng/ml following the initial three doses. Immune responses were measured pre-treatment, at week 4, at week 13, and at 4 and 13 weeks following the booster infusion.
All patients are followed with serial PSA measurements. Patients continue to be followed for the clinical endpoints of time to distant failure, which typically would be the appearance of a positive bone scan, and for overall survival.
According to a media release from Dendreon, the results announced at the AACR meeting are as follows:
- At the time of the week 0 dose of sipleucel-T, the expression of CD54 was upregulated 5.8-fold.
- At the time of the week 2 dose, it was upregulated 10.1-fold, significantly increased from week 0.
- The increase in CD54 upregulation persisted at week 4 (10.7-fold) and at the time of the booster infusion (12.0-fold).
- The booster infusions of sipleucel-T and placebo occurreda median of 1.1 years after the week 4 dose (range 0.2 to 5.5 years).
It is reasonable to assume that if sipleucel-T can be used to extend patient survival in patients with hormone-refractory prostate cancer (and we will know the results of the IMPACT trial next Tuesday afternoon), then it may also have significant effects on patients with earlier stages of prostate cancer.