A Clinical Trail to Determine the Safety and Efficacy of the Combination of Tislelizumab With Cisplatin and Gemcitabine, With or Without Trilaciclib for Patients With Untreated Unresectable and Metastatic Urothelial Carcinoma.

"Chemoimmunotherapy:~1. Tislelizumab: 200mg, 1x time at d1 each cycle~2. Gemcitabine: 1000mg/ m2, in d1, d8 each cycle~3. Cisplatin: 70 mg/m2, in d2 each cycle~4. Trilaciclib: 240mg/m2, d1, d2, d8 each cycle~Tislelizumab maintenance therapy: after chemoimmunotherapy, 200mg, q3W."

"Chemoimmunotherapy:~1. Tislelizumab: 200mg, 1x time at d1 each cycle~2. Gemcitabine: 1000mg/ m2, in d1, d8 each cycle~3. Cisplatin: 70 mg/m2, in d2 each cycle~Tislelizumab maintenance therapy: after chemoimmunotherapy, 200mg, q3W."