Inclusion Criteria:

          1. Is the age of majority (adulthood) in their country

          2. Has an Eastern Cooperative Oncology Group Performance Status (ECOG PS) of 0 to 1

          3. Has pathologically documented breast cancer or urothelial cancer that is unresectable
             or metastatic, and refractory to or intolerant of existing therapy(ies) known to
             provide clinical benefit, and as specified in each study cohort

          4. Has an adequate archival tumor sample available for the central laboratory to
             determine eligibility to participate

          5. Has at least 1 measurable lesion per RECIST version 1.1

          6. Has cardiac, bone marrow, kidney, liver, blood and clotting test results required per
             protocol

          7. Has had an adequate washout period before enrollment since previous surgery and other
             treatment

          8. If reproduction is possible, agrees to use protocol-defined methods of contraception
             (or completely abstain from heterosexual intercourse) from screening to at least 7
             months for females and males after the last dose of study drug

          9. Agrees to avoid harvesting sperm or ova for any reason from screening to at least 7
             months for females and males after the last dose of study drug

         10. Has a life expectancy of at least 3 months

        Exclusion Criteria:

          1. Has received prior treatment with nivolumab or trastuzumab deruxtecan

          2. Has medical history of myocardial infarction (MI) within 6 months before enrollment,
             symptomatic congestive heart failure (CHF) (New York Heart Association classes II-IV).
             Troponin levels above upper limit of normal (ULN) at screening (as defined by the
             manufacturer) and without any MI-related symptoms should have a cardiologic
             consultation before enrollment to rule out MI.

          3. Has a corrected QT interval by Fredericia (QTcF) prolongation to > 470 ms (females) or
             > 450 ms (males) based on an average of the screening triplicate 12-lead
             electrocardiogram

          4. Has history of non-infectious interstitial lung disease (ILD/pneumonitis) (that
             required steroids), has ILD/pneumonitis currently, or it cannot be ruled out by
             imaging at screening

          5. Has a condition (other than active autoimmune disease) that requires systemic
             treatment with either corticosteroids (>10 mg daily prednisone equivalent) or other
             immunosuppressive medications within 14 days of starting study treatment

          6. Is pregnant or breastfeeding, or planning to become pregnant

          7. Is suspected to have certain other protocol-defined diseases based on past medical
             history, physical exam, blood tests, eye test and imaging at screening period

          8. Has received a live vaccine within 30 days before the first dose of study drug

          9. Is related to the investigator or another employee of the sponsor or the study site

         10. Is pregnant, breastfeeding, or planning to become pregnant

         11. Has or had any disease, psychiatric or medical condition, metastatic condition,
             drug/medication use or other condition that might, per protocol or in the opinion of
             the investigator, compromise:

               1. safety or well-being of the participant or offspring

               2. safety of study staff

               3. analysis of results