Efficacy and Safety of Anti-PD-1/PD-L1 Treatment +/- UV1 Vaccination in Patients With Non-small Cell Lung Cancer

This study is testing whether adding a personalized cancer vaccine called UV1 (which targets telomerase, a protein highly active in cancer cells) to standard pembrolizumab immunotherapy improves outcomes for patients with advanced non-small cell lung cancer (NSCLC). **You may be eligible if...** - You have stage IIIB/IIIC or stage IV non-small cell lung cancer that cannot be treated with curative intent - Your tumor shows high PD-L1 expression (≥50%) and you are eligible for pembrolizumab as first-line treatment - You have not previously received immunotherapy - You have at least one measurable tumor lesion on imaging **You may NOT be eligible if...** - Your PD-L1 expression is below 50% - You have active autoimmune disease or are on immunosuppressive medications - You have brain metastases that are untreated or unstable - You have received prior immunotherapy Talk to your doctor to see if this trial is right for you.