Overall Survival (OS) is defined as the time between the date of randomization and the date of death. For participants without documentation of death, OS will be censored on the last date the subject was known to be alive.

Progression-free survival (PFS) is defined as the time from randomization to the date of the first documented progressive disease (PD) per Blinded Independent Central Review (BICR) or death due to any cause. Participants who die without a reported prior PD per BICR (and die without start of subsequent therapy) will be considered to have progressed on the date of death. Participants who did not have documented PD per BICR per RECIST1.1 criteria and who did not die, will be censored at the date of the last evaluable tumor assessment on or prior to initiation of the subsequent anti-cancer therapy. Participants who did not have any on-study tumor assessments and did not die (or died after initiation of the subsequent anti-cancer therapy) will be censored at the randomization date. Participants who started any subsequent anti-cancer therapy without a prior reported PD per BICR will be censored at the last tumor assessment on or prior to initiation of the subsequent anti-cancer therapy.

The time between the date of randomization and the date of first documented recurrence (local urothelial tract, local non-urothelial tract or distant), or death due to any cause, whichever occurs first.

The time between the date of randomization and the date of first documented recurrence (local urothelial tract, local non-urothelial tract or distant), or death due to any cause, whichever occurs first.

A dose-limiting toxicity (DLT) is defined as a drug-related AE occurring in the first 6 weeks of study treatment. A participant was considered evaluable for a DLT if study treatment was delayed \> 2 weeks or was discontinued due to a related Adverse Event (AE), or if planned study treatment (3 doses of nivolumab in Module A, 2 doses of nivolumab plus ipilimumab in Module B) was administered and safety evaluation after 6 weeks on study is available to the study steering committee (SSC).

The number of Safety Lead-In Participants who experienced a Serious Adverse Event (SAE) during the course of the study.

The number of Safety Lead-In Participants who experienced an Adverse Event (AE) during the course of the study that lead to discontinuation of study therapy.

Overall survival (OS) is defined as the time between the date of diagnosis and the date of death in Cohort 1.

Progression-free survival (PFS) is defined as the time from first dose to the date of the first documented tumor progression or death due to any cause.

Progression-free survival (PFS) is defined as the time from first dose to the date of the first documented tumor progression or death due to any cause.

Objective Response Rate (ORR) was defined as the number of participants with a best overall response of confirmed Complete Response (CR) or Partial Response (PR) (per RECIST 1.1 criteria) divided by the number of all treated participants. RECIST 1.1 = Response Evaluation Criteria in Solid Tumors. CR= Disappearance of all target lesions. Any pathological lymph nodes (whether target or non-target) must have reduction in short axis to \< 10 mm. PR= At least a 30% decrease in the sum of diameters of target lesions, taking as reference the baseline sum diameters. BIRC= blinded independent review committee

Objective Response Rate (ORR) was defined as the number of participants with a best overall response of confirmed Complete Response (CR) or Partial Response (PR) (per RECIST 1.1 criteria) divided by the number of all treated participants. RECIST 1.1 = Response Evaluation Criteria in Solid Tumors. CR= Disappearance of all target lesions. Any pathological lymph nodes (whether target or non-target) must have reduction in short axis to \< 10 mm. PR= At least a 30% decrease in the sum of diameters of target lesions, taking as reference the baseline sum diameters. BIRC= blinded independent review committee PD-L1 expression level= membranous staining in greater than or equal to 5% and greater than or equal to 1% tumor cells. n = Number of participants in each category

TTR is defined as the time from first dosing date to the date of the first confirmed complete response (CR) or partial response (PR), as assessed by the Blinded Independent Review Committee (BIRC). Complete response is defined as the disappearance of all target lesions. Any pathological lymph nodes (whether target or non-target) must have reduction in short axis to \< 10 mm. Partial response is defined as at least a 30% decrease in the sum of diameters of target lesions, taking as reference the baseline sum diameters.

DOR is defined as the time from first confirmed response, complete response (CR) or partial response (PR) to the date of the first documented tumor progression as determined using RECIST 1.1 criteria or death due to any cause, whichever occurs first. Participants who start subsequent therapy without a prior reported progression will be censored at the last evaluable tumor assessments prior to initiation of the subsequent anticancer therapy. Participants who die without a reported prior progression will be considered to have progressed on the date of their death. Participants who neither progress nor die will be censored on the date of their last evaluable tumor assessment.

Number of participants with any grade of drug-related select adverse events (AEs) including endocrine, gastrointestinal, hepatic, pulmonary, renal, skin, and hypersensitivity AEs in Neoadjuvant cohort

Number of participants with any grade of drug-related serious adverse events (SAEs) in Neoadjuvant cohort

Rate of surgery delay is defined as the percentage of participants in the neoadjuvant cohort with surgery delayed \> 4 weeks from the planned surgery date or planned start date for chemoradiation due to a drug-related adverse event. Participants with the following diseases will be assessed: 1. HPV positive squamous cell carcinoma of the Head and Neck (SCCHN); 2. HPV negative SCCHN; 3. Cervical Carcinoma; 4. Vaginal/Vulvar Carcinoma; 5. Merkel Cell Carcinoma

Objective response rate (ORR) is defined as the percentage of participants with a best overall response (BOR) of confirmed complete response (CR) or partial response (PR) using RECIST 1.1 criteria. An ORR in excess of 10% will be considered of clinical interest, and an ORR of 25% or greater will be considered of strong clinical interest. Complete Response (CR): Disappearance of all target lesions. Any pathological lymph nodes (whether target or non-target) must have reduction in short axis to \< 10 mm. Partial Response (PR): At least a 30% decrease in the sum of diameters of target lesions, taking as reference the baseline sum diameters. Participants with the following diseases will be assessed: 1. EBV positive related gastric cancer; 2. HPV positive SCCHN; 3. Other anogenital HPV associated cancers; 4. GYN (Cervical, Vaginal, Vulvar) carcinoma; 5. Merkel cell carcinoma (MCC); 6. Nasopharyngeal carcinoma (NPC)