RecruitingPhase 1Biological interventionNovel RNA-lipid Particle (RNA-LP) Vaccine for Anti-PD-1 Antibody Therapy SensitizationThe goal of this phase I trial is to evaluate the toxicity and feasibility of a tumor-specific RNA-NP vaccine in patients with stage IIB-IV melanoma who have evidence of progressive disease by RECIST 1.1 criteria while receiving adjuvant aPD1 therapy, or those who progress within 6 months of completion of adjuvant treatment, or unresectable stage II soft tissue sarcoma or stage III-IV soft tissue sarcoma.