Impact of prior docetaxel (D) on sipuleucel-T (sip-T) product parameters in PROCEED patients (pts).

Abstract

5034 Background: Sip-T is an autologous cellular immunotherapy indicated for asymptomatic or minimally symptomatic mCRPC. The IMPACT trial excluded pts who received D ≤3 months prior to registration. PROCEED is an ongoing, phase IV registry, enrolling pts treated with commercial sip-T. Use of D prior to sip-T is not restricted, so prior D affect on sip-T immune manufacturing parameters can be evaluated. Methods: Pts treated with sip-T ≤ 6 mo were eligible to provide informed consent. Sip-T parameters assessed included: total nucleated cell (TNC) count, antigen presenting cell (APC) count (CD54+large cells) and APC activation (upregulation of CD54). Results: By Nov. 2012, 108/761 (14%) received D prior to sip-T and had similar median cumulative APC counts (1.83 [Q1, Q3: 1.16, 2.71] vs. 1.82 [1.27, 2.70] x 109) and TNC counts (10.16 [7.30, 13.69] vs. 11.47 [8.56, 15.31] x 109) vs. D naïve, whereas median cumulative APC activation appeared slightly lower (32.39 [25.05, 41.02] vs. 34.84 [28.71, 42.83]), but was well above the release criterion for each infusion (2.6 fold). The group was then split by Eastern Cooperative Oncology Group Performance Status (ECOG PS) and Gleason scores (Table). Conclusions: Pts with D prior to sip-T appeared to have product parameters comparable to pts without prior D, albeit with a slightly lower APC activation. Further analysis showed that pts receiving D within 3 months of sip-T had higher Gleason and ECOG scores. The clinical significance of these findings is unclear, but suggests that APC activation is not impaired following docetaxel. Clinical trial information: NCT01306890. [Table: see text]