Randomized Phase II Trial of Sipuleucel-T with or without Radium-223 in Men with Bone-metastatic Castration-resistant Prostate Cancer

Catherine H Marshall, Wei Fu, Hao Wang, Jong Chul Park, Theodore L DeWeese, Phuoc T Tran, Daniel Y Song, Serina King, Michaella Afful, Julia Hurrelbrink, Charlotte Manogue, Patrick Cotogno, Nancy P Moldawer, Pedro C Barata, Charles G Drake, Edwin M Posadas, Andrew J Armstrong, Oliver Sartor, Emmanuel S Antonarakis, Catherine H Marshall, Wei Fu, Hao Wang, Jong Chul Park, Theodore L DeWeese, Phuoc T Tran, Daniel Y Song, Serina King, Michaella Afful, Julia Hurrelbrink, Charlotte Manogue, Patrick Cotogno, Nancy P Moldawer, Pedro C Barata, Charles G Drake, Edwin M Posadas, Andrew J Armstrong, Oliver Sartor, Emmanuel S Antonarakis

Abstract

Purpose: To investigate whether radium-223 increases peripheral immune responses to sipuleucel-T in men with bone-predominant, minimally symptomatic metastatic castration-resistant prostate cancer (mCRPC).

Patients and methods: A total of 32 patients were randomized 1:1 in this open-label, phase II multicenter trial. Patients in the control arm received three sipuleucel-T treatments, 2 weeks apart. Those in the combination arm received six doses of radium-223 monthly, with sipuleucel-T intercalated between the second and fourth doses of radium-223. The primary endpoint was a comparison of peripheral antigen PA2024-specific T-cell responses (measured by proliferation index). Secondary endpoints were progression-free survival (PFS), overall survival (OS), and PSA responses.

Results: We enrolled 32 patients, followed for a median of 1.6 years. Six weeks after the first sipuleucel-T dose, participants in the control arm had a 3.2-fold greater change in PA2024-specific T-cell responses compared with those who received combination treatment (P = 0.036). Patients in the combination arm were more likely to have a >50% PSA decline [5 (31%) vs. 0 patients; P = 0.04], and also demonstrated longer PFS [39 vs. 12 weeks; HR, 0.32; 95% confidence interval (CI), 0.14-0.76] and OS (not reached vs. 2.6 years; HR, 0.32; 95% CI, 0.08-1.23).

Conclusions: Our data raise the possibility of greater clinical activity with the combination of sipuleucel-T and radium-223 in men with asymptomatic bone mCRPC, despite the paradoxically lower immune responses observed. Additional study to confirm these findings in a larger trial is warranted.

©2021 American Association for Cancer Research.

Figures

Figure 1.
Figure 1.
Clinical trial schema
Figure 2.
Figure 2.
Consort diagram
Figure 3.
Figure 3.
Immunologic endpoints (at week 6, N = 12 in combination arm with paired data, and N=11 in sipuleucel-T alone arm with paired data). 3A. Fold change in PA2024 proliferation index compared to baseline 3B. Fold change in PAP proliferation index compared to baseline 3C. Fold change in PA2024-specific T cells by ELISPOT 3D. Fold change in PAP-specific T cells by ELISPOT
Figure 4.
Figure 4.
Waterfall plot showing best PSA response rate
Figure 5.
Figure 5.
Clinical endpoints 5A. Progression-free survival of the radium-223 + sipuleucel-T (red) arm compared to sipuleucel-T alone (teal). 5B. Overall survival comparing the two arms

Source: PubMed

Sponsoren und Mitarbeiter

Krankheiten

Drogeninterventionen

3
Abonnieren