This is a Phase 2a, double-blind, placebo-controlled, multi-center, randomized study of LSTA1 when added to SoC versus SoC alone in subjects with advanced solid tumors. The study will consist of a screening period, a run-in period, a treatment period, an end-of-treatment follow-up visit, and a long-term follow up period. Survival and subsequent anti-cancer therapies will be assessed during the long-term follow-up. The study will include 3 cohorts of subjects which include advanced head and neck squamous cell carcinoma, esophageal squamous cell carcinoma, and cholangiocarcinoma.