Sitagliptin

The purpose of this study is to evaluate whether treating glioblastoma patients with sitagliptin can improve immune response against the tumor by targeting specific immune cells called myeloid-derived suppressor cells (MDSCs) that suppress your body's natural immune response against cancer. Sitagliptin is an investigational drug for this condition that works by inhibiting an enzyme called dipeptidyl peptidase 4 (DPP-4), which MDSCs rely on to enter the brain and function. While sitagliptin is FDA-approved for diabetes treatment, its use in glioblastoma is investigational (experimental).

This study is testing whether adding the drug sitagliptin to the standard immunotherapy pembrolizumab is safe and may help people with advanced melanoma or advanced renal cell carcinoma (kidney cancer) whose cancer has stopped responding to prior PD-1 or PD-L1 immunotherapy. The study has two parts. In the first part, small groups of participants will receive different doses of sitagliptin along with a fixed dose of pembrolizumab. This helps researchers find the highest dose of sitagliptin that can be given safely. In the second part, more participants will receive the safest dose to see how well the drug combination works against their cancer.

This is a multicenter, prospective, open-label, Phase II, four-arm parallel study evaluating the efficacy and safety of different sensitization strategies combined with disitamab vedotin and toripalimab in patients with HER2-positive muscle-invasive urothelial carcinoma of the bladder (MIBC). Eligible patients with cT2-4aN0M0 HER2-positive urothelial carcinoma of the bladder will receive neoadjuvant disitamab vedotin plus toripalimab in combination with one of four sensitizing agents: sitagliptin, tazemetostat, tafolecimab, or ursodeoxycholic acid. After six cycles of neoadjuvant treatment, patients will undergo comprehensive response assessment, including imaging, cystoscopy, urine cytology, and complete transurethral resection of bladder tumor (cTURBT). Patients who achieve a clinical complete response (cCR) may enter a bladder-preservation treatment pathway, including additional disitamab vedotin plus toripalimab and subsequent toripalimab maintenance therapy. Patients who do not achieve cCR will be considered for salvage radical cystectomy. The primary objective is to evaluate the cCR rate of each treatment strategy. Secondary objectives include bladder-intact disease-free survival, overall survival, bladder preservation rate, safety, quality of life, treatment costs, and exploratory biomarker analyses.