Background: We designed a first-in-human clinical trial to evaluate safety and immunogenicity of LPV7, administered in vaccine adjuvant combinations of incomplete Freund’s adjuvant (IFA) and agonists for TLR3 (polyICLC, pICLC) and TLR7/8 (resiquimod, resiq). We hypothesized that T cell responses to minimal epitopes would be enhanced compared to prior work with short peptides, and that T cell responses would be improved with TLR agonists, compared to IFA alone. Methods: Patients (pts) with resected stage II-IV melanoma were vaccinated with LPV7 plus a tetanus helper peptide restricted by Class II MHC (Tet). LPV7 is comprised of 29-31-mer peptides from tyrosinase, gp100, MAGE-A1, MAGE-A10, and NY-ESO-1, each containing a minimal epitope for CD8 T cells. Pts received LPV7 in one of 7 adjuvants. Accrual was sequentially initiated to groups with increasing numbers of adjuvants in an adaptive design. Vaccine was given weeks 0, 1, 2, 5, 8, and 11; injection sites were rotated and biopsied d8 and d22. Antibody (Ab) and T cell responses were measured with ELISA and IFNγ ELIspot assay ex vivo, respectively. Results: Fifty eligible pts were adaptively assigned to 7 study groups (4-16 pts per arm, Table). There was one dose limiting toxicity: Group E (grade 3 injection site reaction, ISR). All other AEs were grades 1-2; most common were ISR (90%), fatigue (62%), skin induration (56%), chills (48%), fever, myalgia, and headache (30% each), and were similar across groups, but lower in group C. T cell responses to LPV7 were mostly CD4⁺, and were most prevalent for groups A, B, E, and G, as were responses to tetanus peptide. CD8 responses to minimal peptides were lower than in prior trials with short peptides, but were highest for groups A and E (Table). Ab responses to peptides (not shown) were highest for Groups E and G. Conclusions: The LPV7 vaccine is safe and immunogenic. Immunogenicity is supported more by IFA than by TLR agonists alone, and may be enhanced by pICLC plus IFA, with or without resiq. Clinical trial information: NCT02126579