Background: Cancer cells contain unique DNA mutations that result in altered amino acid sequences known as neoantigens. Growing evidence supports a central role for neoantigens as targets for tumor directed immune responses. Tumor mutational burden as well as neoantigen load have been associated with anti-tumor activity of checkpoint inhibitors. Vaccines targeting neoantigens offer a highly specific way to induce de novo T cell reactivity and to expand existing T cell responses against neoantigens. Here, we describe NEO-PV-01, a personalized, neoantigen vaccine designed specifically for the molecular profile of each individual’s tumor. Methods: NT-001 is a single-arm, phase IB study designed to evaluate the safety of administering NEO-PV-01 + adjuvant (Poly-ICLC) with nivolumab in patients with advanced melanoma, smoking-associated non-small cell lung carcinoma, or transitional cell carcinoma of the bladder who have received no more than one prior systemic treatment. Patients undergo a baseline tumor biopsy and HLA typing. DNA and RNA sequencing is performed on the tumors as well as peripheral blood to serve as normal DNA controls. On Day 1, patients begin treatment with nivolumab at a dose of 240 mg IV while their customized vaccine is being generated. Each vaccine is custom designed for the individual patient and contains up to 20 peptides 14-35 amino acids in length. The peptides are pooled into four groups and mixed with Poly-ICLC at the time of administration. Beginning at Week 12, patients receive five priming immunizations over a three-week period followed by booster vaccinations at Weeks 19 and 23. The primary endpoint is safety. Secondary endpoints are ORR, CBR, PFS, and assessment of response conversion between Week 12 and Week 24. Exploratory endpoints include extensive immune monitoring. Clinical trial information: NCT02897765