During the screening phase, the participant’s initial eligibility will be established a nd written informed consent w ill be ob tained. Tumor biopsies collected for all participants w ill be centr ally evaluated for ICOS expression by Revised Protocol No.: 04 Date: 31-May-2019 15 Approved 5.0 v Approved 1.0 v Clinical Protocol CA021002 BMS-986226 anti-ICOS immunohistochemistry (IHC). Stool samples will be collected for baseline microbiota composition analysis. All participants will receive the tetanus booster vaccine 3-7 days prior to Cycle 1 Day 1 of first administration of study treatment. Parti cipants will be allocated to treatment groups using the Interactive Response Technology (IRT). Treatment Phase: •Preliminary Safety Cohorts: The planned dose levels of BMS-986226 in th e Preliminary Safety Cohorts w ill be 2 mg and 8 mg Q4W for 24 weeks. Following each treatment cycle, the decision to tr eat a par ticipant with additional cycles of study treatment (up to a maximum of 24 weeks), will be based on safety and tolerability and tumor assessments pe rformed every 8 weeks ( ±1 week). •Part A: The initial dose level of BMS- 986226 in Part A will be 25 mg Q4W for 24 weeks. Planned dose levels for dose escalation ar e 80, 200, 400, and 800 mg. Participants may be treated for up to 24 weeks.