YONSA (abiraterone acetate) In Metastatic Castration-Resistant Prostate Cancer

MedicalResearch.com Interview with:


Paul Nemeth, Ph.D.
Sr. Vice President, Regulatory Affairs, Clinical Development & Quality Assurance
Churchill Pharmaceuticals LLC
King of Prussia, PA 19406

MedicalResearch.com: What is the background for this study?

Response: In the STAAR study, 53 patients with metastatic castration-resistant prostate cancer (mCRPC) were randomized to receive YONSA, an abiraterone acetate fine particle formulation 500 mg once daily in combination with 4 mg of methylpresnisolone twice daily or 1,000 mg daily of the originator abiraterone acetate (OAA) in combination with 5 mg of prednisone twice daily for a period of 84 days.  Previous studies in healthy volunteers under fasted conditions had shown that single oral doses of 500 mg of YONSA are bioequivalent to single oral doses of 1,000 mg OAA and that a background of 4 mg of methylprednisolone twice daily on a single oral dose of 500 mg of YONSA results in the same extent of absorption as a background of 5 mg of prednisone twice daily on a single oral dose of 1,000 mg of OAA. 

MedicalResearch.com: What are the main findings? 

Response: The main findings of the STAAR study were: that based on serum testosterone levels, therapeutic equivalence between YONSA 500 mg daily and OAA 1,000 mg daily was demonstrated in patients with mCRPC on days 9 and 10. Durability of the effect on serum testosterone and PSA was confirmed during the study through day 84.  The safety profiles for YONSA and OAA were similar and consistent with previously reported adverse events for abiraterone acetate.  Across the duration of the study, trough plasma concentrations were not different at study days 9, 28, 56 and 84.  These findings have been previously reported (Stein CA Urologic Oncology, 2017).

The abstract presentation at ASCO GU, reported on the 24-hour pharmacokinetic profile in a subgroup of 12 of the 53 patients who had enrolled in the STAAR study who had received YONSA (n = 4) or OAA (n = 8);  pharmacokinetic parameters were not significantly different between the two treatment groups of patients. 

MedicalResearch.com: What should readers take away from your report?

Response:  In totality, the studies with YONSA demonstrate that it is therapeutically equivalent to OAA. 

MedicalResearch.com: What recommendations do you have for future research as a result of this work?

Response: An extension study, STAAR-E (NCT02962284) that allows for an additional year of treatment with YONSA and methylprednisolone for patients who successfully completed the STAAR study is on-going.  20 patients have enrolled in the trial (9 previously treated with YONSA and 11 previously treated with OAA in the STAAR study).

MedicalResearch.com: Is there anything else you would like to add?

Response: Both the STAAR study and the on-going STAAR-E study were sponsored by Churchill Pharmaceuticals LLC and several of the authors are employees of Churchill. 

Citations: ASCO 2018 symposium Urol Oncol. 2018 Feb;36(2):81.e9-81.e16. doi: 10.1016/j.urolonc.2017.10.018. Epub 2017 Nov 14.

Stein CA1, Levin R2, Given R3, Higano CS4, Nemeth P5, Bosch B6, Chapas-Reed J6, Dreicer R7.

Randomized phase 2 therapeutic equivalence study of abiraterone acetate fine particle formulation vs. originator abiraterone acetate in patients with metastatic castration-resistant prostate cancer: The STAAR study

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