To Evaluate the Safety, Efficacy, and Pharmacokinetics of Intravesical Instiliations of Disitamab Vedotin in Patients With High-risk Non-muscular Invasive Bladder Cancer (NMIBC) That Express HER2

This study is testing disitamab vedotin — a targeted antibody-drug combination (ADC) that is delivered directly into the bladder — in patients with high-risk non-muscle-invasive bladder cancer (NMIBC) whose tumors express a protein called HER2. **You may be eligible if...** - You are between 18 and 75 years old - You have confirmed non-muscle-invasive bladder cancer classified as high-risk or very high-risk (including CIS, T1 stage, tumors larger than 3cm, or multiple/recurrent tumors) - Your tumor has been shown to express HER2 through testing - You have already had tumor removal surgery (TURBT) but still have residual CIS - You are not a candidate for radical bladder removal surgery, or you have declined it **You may NOT be eligible if...** - Your tumor does not express HER2 - Your bladder cancer has invaded the muscle layer - You have not undergone TURBT - You have other conditions that would make treatment unsafe Talk to your doctor to see if this trial is right for you.