The screening assessments are shown in Table 2-1 . 5.1.2 Treatment Phase The treatment phase in the Preliminary Safety Cohor t and Part A consists of up to six 4-week treatment cycles (1 cycle = 28 days). In the Preliminary Safety C ohort and Part A, each treatment cycle will consist of BMS-986226 monotherapy for a total of 24 weeks. Dose levels for Parts B and C will be determin ed based on all available safety (clinical and laboratory) and PK data, as w ell as changes in peripheral ta rget engagement markers (eg, ICOS Revised Protocol No.: 04 Date: 31-May-2019 54 Approved 5.0 v Approved 1.0 v Clinical Protocol CA021002 BMS-986226 anti-ICOS downregulation on T cells and ICOS + B cells) from previous and comp leted portion of current cohorts, and will be guided by the BLRM/BLRM-Copula model whenever applicable. In Parts B1 and C1, 4 week cycles will be used, such that BMS986226 + nivolumab or ipilimumab will be administered starting on Cy cle 1 Day 1. Nivolumab and ipilimumab will be administered on Day 1 of each cycle. BMS-986226 will be administered Q12W , or on Day 1 of every third cycle (Cycle 1 Day1, Cycle 4, Day1, Cycle 7 Day1, etc.). Part icipants on Parts B1 and C1 may continue treatment for up to a total of 2 years. The treatment phase in Parts B2 and C2 w ill consist of BMS- 986226 + nivolumab or ipilimumab administered on Day 1 of each cycle and will be enrolled if additional safety, PK, or PD data is required to optimize dose and/or schedule s election. In parts B2 and C2 BM S-986226 w ill be administered Q4W and participants may continue treatment for a total of 2 years. Following each treatment cycle, the decision to treat a par ticipant with additional cy cles of study treatment w ill be based on tumor assessment evaluations performed every 8 weeks (Q8W ± 1 week) and completed before the first dose in the next cycle. Tumor progression or response endpoints will be assessed using Response Evaluation Criteria In Solid Tumors (RECIST) v1.1 (Appendix 5) or PCWG3, for prostate only ( Appendix 11). Treatment beyond progression with additional cycles of study treatment may be allowed for up to a maximum of 24 weeks for Part A and 2 years for Parts B, C, D, and E i n select pa rticipants with initial RECIST v1.1 or PCWG3 (prostate only) defined progressive disease after discussion and agreement between the Principal Investigator and the BMS Medical Monitor/Study Director (or designee) that the benefit/risk assessment favors continued administration of the study treatment (eg, participants are continuing to experience clinical benefit as assessed by the investigator, tolerating treatment, and meeting other criteria specified in Section 8.1.2 ). Participants with a response of unconfirmed progressive disease, SD, PR, or CR at the end of a given cycle will continue to the next treatment cycle. Participants will genera lly be allowed to continue study treatment until the first occurren ce of 1) completion of the maximum number of cycles, 2) confirmed progressive disease, 3) clinical deterioration suggesting that no further benefit from treatment is likely, 4) intolerabili ty to therapy, or 5) a participant meeting criteria for discontinuation of study treatment as outlined in Section 8.1 . Individual participants with confirmed CR will be given the option to discon tinue study tr eatment on a case-by-c ase basis after specific consultation and agreement between the investigator and BMS Medical Monitor/Study Director (or designee) in settings where benefit/risk justify discontinuation of study treatment. 5.1.2.1 Monotherapy Dose Escalation (Preliminary Safety Cohorts and Part A) Up to approximately 34 par ticipants may be treated during the monotherapy dose escalation (Preliminary Safety Cohorts and Part A). Expected dose levels for monotherapy dose escalati on (Preliminary Safety Cohorts and Part A) are provided in Table 5.1.2.1-1 . All participants treated with BMS-986226 monotherapy are recommended to receive premedications, as described in Section 7.1 , in order to reduce the risk of infusion-rel ated reactions. Revised Protocol No.: 04 Date: 31-May-2019 55 Approved 5.0 v Approved 1.0 v Clinical Protocol CA021002 BMS-986226 anti-ICOS Preliminary Safety Cohorts The Preliminary Safety Cohorts will evaluate the safety of BMS-986226 following monotherapy administration of 2 dose levels, 2 mg and 8 mg. A single new participant per cohort will be administered an IV BMS-986226 as follows: •BMS-986226 2 mg Q4W in 4-week cycles for up to 24 weeks of study treatment •BMS-986226 8 mg Q4W in 4-week cycles for up to 24 weeks of study treatment For the purpose of guiding dose escalation, dose-limiting toxicities (DLTs) will be defined based on the incidence, intensity, and duration of AEs for which no clear alternative cause is identified. The DLT period will be 28 days (4 weeks) in th e Preliminary Safety Cohorts.