a. Participants with bone-only disease should have progression confirmed as per PCWG3 criteria and require confirmatory scans. iv) Participants must have received abiraterone or enzalutamide. v)“Not applicable as per revised protocol 02” Progression during hormonal treatment. For eligibility purposes, progressi ve disease is defined as: (1).Rising prostate-specific antigen values at a minimum of 1-week intervals and a 2.0- ng/mL minimum starting value OR; (2).Progression per bone scan: the appearance of 2 or more new lesions, OR; (3).Progre ssion per target lesions/measurable disease: nodal progression, per modified RECIST v1.1. Only lymph nodes > 2 cm will be considered to assess a change in size qualifying for disease progression. vi) Anti-androgens (bicalutamide, flutamide, nilutamide) or adrenal androgen production inhibitors (aminoglutethamide or ketoconazole) should be discontinued 28 days prior to starting study treatment. Note: bicalutamide or nilutamide must be discontinued within 6 weeks of study arm assignment. (1).Participants with a history of res ponse to an anti-androgen or adrenal androgen production inhib itor and subsequent progression while on that anti-androgen should be assessed for anti-androgen withdrawal response for 4 weeks, and must demonstrate progression. (2).For participants who ha ve never responded to anti-androgens, observation for anti- androgen withdrawal response is not necessary; however, a 2-week washout period is required prior to start of study treatment. vii) Evidence of M1 metastatic disease on previous bone, CT, and/or MRI scan. viii) Ongoing ADT with a gonadotropin-releasing hormone (GnRH) anal ogue or bilateral orchiectomy (ie, surgical or medical castration) confirmed by testosterone levels of 1.73 nmol/L ( ≤50 ng/dL) at the screening visit. Castrate levels of testosterone must be maintained by surgical or med ical means (leu teinizing Revised Protocol No.: 04 Date: 31-May-2019 73 Approved 5.0 v Approved 1.0 v Clinical Protocol CA021002 BMS-986226 anti-ICOS hormone-releasing hormone (LHRH / GnRH analogues) throughout the conduct of the study. ix) Documented prostate cancer progression as per PCWG3 criteria39(see Appendix 11 ) with one of the following: (1).PSA progression* defined by a minimum of 2 rising PSA levels with an interval of ≥1 week between each determination with either (a) soft tissue disease progression or (b) bone disease progression or both (a) and (b).