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44 - POS-03
Effect of Prior Abiraterone (ABI) or Enzalutamide (ENZ) on Sipuleucel-T (Sip-T) Manufacture in PROCEED Patients (pts)

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EFFECT OF PRIOR ABIRATERONE (ABI) OR ENZALUTAMIDE (ENZ)
ON SIPULEUCEL-T (SIP-T) MANUFACTURE IN PROCEED PATIENTS (PTS)

Celestia S. Higano, MD1, Nicholas J. Vogelzang, MD2, Jeffrey Vacirca, MD, FACP3, Philip W. Kantoff MD4,
Mark Scholz, MD5, Shaker R. Dakhil, MD6, Luke T. Nordquist, MD7, Oliver Sartor, MD8,
Matthew R. Cooperberg, MD, PhD9, Andrew Sandler, MD1, Candice McCoy, MD1, James B. Whitmore, PhD1,
Robert C. Tyler, PhD1, Andrew J. Armstrong, MD, MSc10*

1Seattle, WA; 2Las Vegas, Nevada; 3East Setauket, NY; 4Boston, MA; 5Marina del Rey, CA;
6Wichita, KS; 7Omaha, NE; 8New Orleans, LA; 9San Francisco, CA; 10Durham, NC

Presentation to be made by Dr. Higano

Background: Sip-T is an autologous cellular immunotherapy indicated for asymptomatic or minimally symptomatic metastatic castration-resistant prostate cancer (mCRPC). PROCEED is an ongoing phase 4 registry, enrolling pts receiving commercial sip-T. There are no exclusions based on prior prostate cancer treatments, so sip-T product parameters can be evaluated in pts receiving prior hormonal agents such as ABI or ENZ.

 

Methods: Pts treated with sip-T within ≤6 mo were eligible to provide informed consent. Prior anticancer interventions were recorded at baseline. Sip-T product parameters were assessed.

 

Results: Of 1376 pts (as of May 2013), 108 (7.8%) received prior ABI and 58 (4.2%) received ENZ. Patients with ABI or ENZ generally had more advanced disease vs. pts without prior ABI or ENZ (WPT) and a greater proportion of the ABI and ENZ pts received prior docetaxel. There were slight differences in some sip-T product parameters in the ABI and ENZ groups, but neither manufacture nor receipt of sip-T were inhibited, as indicated by the percentage of pts with 3 successful infusions. All groups showed evidence of immune prime boost (Table 1).

 

Conclusions: A subset of patients in PROCEED have received ABI or ENZ prior to sip-T.  We observed no impact of prior ABI/ENZ on sip-t manufacturing or delivery, despite these men having more advanced disease. These results are consistent with prior analyses demonstrating a positive sip-T treatment immune effect in patients who have received prior therapies, including chemotherapy. These data are also consistent with preliminary data from ongoing studies with sip-T and concurrent use of ABI plus prednisone (STAMP) or ENZ (STRIDE), which suggest that sip-T can be successfully manufactured with similar product potency, compared with sip-T alone. Further immune monitoring and outcome studies are currently ongoing in the pre-docetaxel mCRPC setting where these agents will likely be used clinically.