A Study to Evaluate Safety, Efficacy, Pharmacokinetics, and Pharmacodynamics of Erdafitinib Plus JNJ-63723283, an Anti-PD-1 Monoclonal Antibody, in Participants With Metastatic or Surgically Unresectable Urothelial Cancer With Selected FGFR Gene Alterations

This open-label (all people know identity of intervention) and multicenter (when more than
one hospital or medical school team work on a medical research study) study of erdafitinib
plus JNJ-63723283 in participants with advanced urothelial cancer with selected fibroblast
growth factor receptor (FGFR) gene alterations who have progressed on or after one or more
prior lines of systemic therapy, will consists of 2 parts. Part 1 (Phase 1b: Dose Escalation)
will establish recommended Phase 2 dose (RP2D) for erdafitinib in combination with
JNJ-63723283, and Part 2 (Phase 2: Dose Expansion) will evaluate safety and efficacy of RP2D.
The study will be conducted in 3 phases: screening phase, treatment phase, and follow-up
phase. Study evaluations include efficacy, pharmacokinetics, pharmacodynamics,
immunogenicity, biomarkers, and safety.

Inclusion Criteria:

- Histologic demonstration of transitional cell carcinoma of the urothelium. Minor
components (less than [<] 50 percent [%] overall) of variant histology such as
glandular or squamous differentiation, or evolution to more aggressive phenotypes such
as sarcomatoid or micropapillary change are acceptable

- Stage IV disease

- Documented progression of disease per Response Evaluation Criteria in Solid Tumors
(RECIST) 1.1, defined as any progression that requires a change in treatment, prior to
randomization

- Prior systemic therapy: (a) Phase 1b: Any number of lines of prior therapy; (b) Phase
2: Progressed after 1 or 2 lines of prior chemotherapy

- Eastern Cooperative Oncology Group (ECOG) performance status (PS) grade of: 0 or 1

Exclusion Criteria:

- Treatment with any other investigational agent or participation in another clinical
study with therapeutic intent within 30 days prior to Cycle 1 Day 1. For Phase 1b,
participants who have received the following prior antitumor therapy: received
nitrosoureas and mitomycin C within 6 weeks

- Chemotherapy within 3 weeks of Cycle 1 Day 1

- Prior anti-programmed death receptor-1 (PD-1), anti-programmed death ligand-1 (PD-L1),
or anti-programmed death ligand-2 (PD-L2) therapy

- Active malignancies (that is, requiring treatment change in the last 24 months) other
than urothelial cancer (except skin cancers within the last 24 months that are
considered completely cured)

- Symptomatic central nervous system metastases