BL-M07D1 (Trastuzumab Brengitecan T-bren) vs Standard of Care Platinum-based Chemotherapy (PBC) for HER2-expressing Metastatic Urothelial Cancer After Progression on Anti-PD-(L)1-based Therapy

Inclusion Criteria:

* Histologically or cytologically documented metastatic or surgically unresectable transitional cell carcinoma (TCC) of the urothelium involving the renal pelvis, ureter, bladder, or urethra. Minor histologic variants (ie, \<50% overall) are acceptable, provided that TCC is the dominant histology.
* Disease progression or recurrence during or following anti-PD-(L)1-based therapy.
* Fresh biopsy or archival tumor samples.
* Documented HER2 expression by central laboratory testing.
* Eligible to receive carboplatin or cisplatin in combination with gemcitabine.
* At least 1 measurable lesion based on RECIST v1.1.
* An Eastern Cooperative Oncology Group performance status (ECOG PS) of 0 to 1.
* Adequate organ function.
* Adequate coagulation parameters.

Exclusion Criteria:

* Prior topoisomerase inhibitor-based ADC therapy.
* Primary tumors in the central nervous system (CNS), active or untreated CNS metastases, or carcinomatous meningitis.
* Bladder cancers with small cell histology.
* Other prior or concurrent malignancies except for certain localized cancers or low-grade prostate cancer (if approved by sponsor), or other malignancy treated with curative intent with a disease-free interval of at least 3 years.
* Prior history of clinically significant bleeding, or perforation of the gastrointestinal tract within 6 months of randomization.
* Active autoimmune diseases and inflammatory diseases.
* History of noninfectious interstitial lung disease (ILD)/pneumonitis that required treatment with steroids, have current ILD/pneumonitis, or where suspected ILD/pneumonitis cannot be ruled out by imaging at Screening.
* Advanced/clinically significant lung disease (eg, poorly controlled chronic obstructive pulmonary disease or asthma, restrictive lung disease, or pulmonary hypertension) within 6 months prior to randomization.
* Known human immunodeficiency virus infection.
* Active hepatitis B virus (HBV) infection.
* Active hepatitis C virus (HCV) infection.
* Active or latent tuberculosis.
* Other protocol-specified inclusion/ exclusion criteria apply