Intra-lymph node prime-boost vaccination against Melan A and tyrosinase for the treatment of metastatic melanoma: results of a phase 1 clinical trial.

Purpose: The goal of this study was to test the safety and activity of a therapeutic vaccine, MKC1106-MT, in patients with metastatic melanoma.

Experimental Design: MKC1106-MT comprises a plasmid (pMEL-TYR) and two peptides (E-MEL and E-TYR), corresponding to Melan A and tyrosinase, administered by intra-lymph node injection in a prime-boost sequence. All 18 patients were HLA-A*0201 positive and received a fixed priming dose of plasmid and a low or a high peptide dose. Enumeration of antigen-specific T cells was done prior to and throughout the treatment. Patients who did not exhibit disease progression remained on study and could receive up to eight cycles of treatment.

Results: The MKC1106-MT regimen was well tolerated and resulted in an overall immune response rate of 50%. The treatment showed disease control, defined as stable disease that lasted for 8 weeks or more in 6 of 18 (33%) of the patients: 14% and 46% in the low and high peptide dose, respectively. Interestingly, four patients, all with tumor burden largely confined to lymph nodes and Melan A-specific T cells at baseline, showed durable disease control associated with radiologic evidence of tumor regression. There was no noticeable correlation between the expansion of antigen-specific T cells in blood and the clinical outcome; yet, there was evidence of active tumor-infiltrating lymphocytes (TIL) in two regressing lesions.

Conclusions: MKC1106-MT showed immunogenicity and evidence of disease control in a defined patient population. These findings support further development of this investigational agent and the concept of therapeutic vaccination in metastatic melanoma.