Autologous Lymphocyte Infusion Supports Tumor Antigen Vaccine-Induced Immunity in Autologous Stem Cell Transplant for Multiple Myeloma.

Autologous stem cell transplant (autoSCT), the standard consolidation therapy for multiple myeloma, improves disease-free survival, but is not curative. This could be an ideal setting for immunologic therapy. However, the immune milieu is impaired after autoSCT. We hypothesized that autologous lymphocyte infusion would restore immune competence, allowing immunotherapies such as cancer vaccines to elicit tumor antigen-specific immunity in the setting of autoSCT. In this pilot study (NCT01380145), we investigated safety, immunologic, and clinical outcomes of autologous lymphocyte infusion combined with peri-autoSCT immunotherapy with recombinant MAGE-A3 (a multiple myeloma-associated antigen) and adjuvant. Thirteen patients with multiple myeloma undergoing autoSCT were enrolled. Autologous lymphocyte infusion and MAGE vaccination were well tolerated. Combination immunotherapy resulted in high-titer humoral immunity and robust, antigen-specific CD4+ T-cell responses in all subjects, and the responses persisted at least one year post-autoSCT. CD4+ T cells were polyfunctional and Th1-biased. CD8+ T-cell responses were elicited in 3 of 13 subjects. These cells recognized naturally processed MAGE-A3 antigen. Median progression-free survival was 27 months, and median overall survival was not reached, suggesting no differences from standard-of-care. In 4 of 8 subjects tested, MAGE-A protein expression was not detected by IHC in multiple myeloma cells at relapse, suggesting therapy-induced immunologic selection against antigen-expressing clones. These results demonstrated that autologous lymphocyte infusion augmentation of autoSCT confers a favorable milieu for immunotherapies such as tumor vaccines. This strategy does not require ex vivo manipulation of autologous lymphocyte products and is an applicable platform for further investigation into combination immunotherapies to treat multiple myeloma. ©2019 American Association for Cancer Research.