Sipuleucel-T viable during abiraterone treatment

Data from a phase II study suggest that the potency of sipuleucel-T (Provenge) and immunologic prime-boost responses are maintained when the immunotherapy is administered concurrently or sequentially wth abiraterone acetate (ZYTIGA) plus prednisone.

The study was one of several related to sipuleucel-T presented at the European Cancer Congress in Amsterdam, the Netherlands.

In the phase II study, patients with asymptomatic/minimally symptomatic metastatic castration-resistant prostate cancer were co-administered sipuleucel-T (three infusions at weeks 0, 2, and 4) with concurrent or sequential abiraterone plus placebo (abiraterone, 1,000 mg daily, plus placebo, 5 mg twice daily for ≤26 weeks). Patients were randomized 1:1 to abiraterone plus placebo starting either 1 day (concurrent) or 10 weeks (sequential) after the first sipuleucel-T infusion. The study’s primary endpoint was antigen-presenting cell (APC) activation; additional endpoints included APC and total nucleated cell (TNC) counts (sipuleucel-T product potency measures), immune responses, adverse events, and efficacy.

The authors, led by Eric J. Small, MD, of the University of California, San Francisco, reported that median cumulative APC activation and APC and TNC counts did not differ between the two arms (p>.05). APC activation increased with the second and third sipuleucel-T infusions in both arms, indicating a prime-boost effect. No differences were seen between arms in the robust peripheral antibody and T cell responses observed (p>.05).

Overall adverse event incidence was 96.9% in the concurrent arm and 87.5% in the sequential arm. However, most adverse events were infusion related, occurring within 1 day of infusion (53.1% and 65.6% of total population, respectively).

"These preliminary data are encouraging, and suggest that combining sipuleucel-T and abiraterone acetate plus prednisone is possible. It is not known if the potential for an immunostimulatory effect from low testosterone levels achieved with abiraterone may be offset by the potentially immunosuppressive effects of prednisone," Dr. Small said. "This study demonstrated that the co-administration of sipuleucel-T with abiraterone acetate and prednisone was generally well tolerated, and did not affect the product characteristics of sipuleucel-T nor its capacity to show an immune response."

Dr. Small is an advisory board member for and conducts corporate-sponsored research for Dendreon. Several of his co-authors are advisory board members of; have ownership in; are employees of; and/or have other substantive relationships with Dendreon.

To get weekly news from the leading news source for urologists, subscribe to the Urology Times eNews.