Project Summary Most bladder cancer (BC) patients are diagnosed at an early stage. More than 80% of cases are non-muscle invasive BC (NMIBC). The standard treatment involves removing the tumors surgically, followed by intravesical immunotherapy, bacillus Calmette-Guérin (BCG), or intravesical chemotherapy (ITC) to eradicate residual cancer cells. This involves direct instillation of the BCG or drug solution into the bladder via a catheter. However, the cancer recurrence rate is still unacceptably high (50-80%). On the other hand, there is a growing interest in preserving the bladders of muscle invasive BC (MIBC) patients who are ineligible for radical cystectomy with ITC. BCG and ITC have limitations. The treatments are local. The drug solution is unable to reach tumors located in the upper urinary tract. Patients often need to void shortly after drug administration. The catheterization procedure is invasive, which can potentially cause infection and urinary symptoms, resulting in poor patient compliance. Currently, there is also a shortage of BCG. The goal of this project is to develop an approach to counter the significant drug delivery obstacles of BC therapy to improve treatment and survival outcomes. A peptide’s rapid renal clearance can be advantageous for directing treatments to the urinary system (URS). We propose a bio-inert peptide (Bdd) to overcome the drug-delivery barriers. Bdd can be given intravenously rather than intravesically. The use of Bdd as a carrier was shown to promote drugs, such as mertansine (DM1) and doxorubicin (DOX), to be eliminated exclusively via renal clearance, with minimal—if not undetectable— deposition in major organs. We hypothesize that this platform, used as an alternative to ITC, will offer an urgently needed treatment that is more complete and effective. The advantages of such a urinary drug disposing (UDD) system include: (1) continuous drug flow throughout the entire URS, (2) prolongation of bladder-dwelling time (treatment duration), and (3) minimally invasive application. If successful, this approach will also avoid catheterization, improve patient quality of life, and reduce hospitalization costs. Our Specific Aims will focus on preclinical and translational studies to: (Aim 1) investigate the desired physicochemical properties (including functional group, length, and surface charges) and administration parameters (infusion rate and volume) of a newly developed Bdd analogue, Bds, with an improved UDD property, for precision drug delivery to the URS; and (Aim 2) evaluate the therapeutic efficacy and anatomic flexibility of a DM1-Bds conjugate for BC treatment. We will assess DM1-Bds alone or in combination with pembrolizumab, an immune checkpoint inhibitor approved by the Food and Drug Administration, for treating both NMIBC and MIBC. Immune profiling will address the anti- tumor activities. This information will be crucial for significantly improving treatment outcomes. With additional advancements...