Evaluation of Tumor Vaccine Generation in a Phase II Multicenter Trial of Single Autologous Hematopoietic Cell Transplant (AutoHCT)Followed By Lenalidomide Maintenance for Multiple Myeloma (MM) with or without Vaccination with Dendritic Cell/ Myeloma Fusions (DC/MM fusion vaccine): Blood and Marrow Transplant Clinical Trials Network (BMT CTN) 1401

BMT CTN 1401 is an academically led randomized study of a personalized cancer vaccine in which the combination of DC/MM fusion vaccine and lenalidomide maintenance after autoHCT is compared with maintenance alone as upfront treatment of MM (NCT#02728102). Assessment of the percentage of patients achieving CR and therapy-induced changes in MM-specific immunity are the primary clinical and immunologic endpoints, respectively. The protocol represents a transformative open source approach to cell therapy in MM and required collection of tumor cells prior to treatment initiation and vaccine production at day 60 after autoHCT. The process featured a multi-step approach of procedural standardization, training, and centralized verification of manufactured product/release criteria. Here we present initial analysis of accrual and vaccine manufacturing. Enrollment of 203 patients completed within 26 months with 140 patients randomized. Drop-out rate from enrollment to randomization was 31% (expected 30%). Sixty-eight patients were randomized to the DC/MM fusion vaccine arm, with 63 having products successfully manufactured and approved for release at 14 manufacturing sites. Vaccine products for 5 patients were not approved for release for the following reasons: final TC/DC viability did not meet release criteria (n = 3), product failed to meet sterility release criteria (n = 1), and disease progression prior to manufacture (n = 1). Among 63 participants who received vaccine, mean DC viability and CD86 expression was 79.3% (Standard Deviation = 11.3) and 80.6% (SD = 12.9), respectively. Mean viability and percent cells co-expressing DC and tumor antigens was 78.6% (SD = 13.0) and 47.9% (SD = 11.4), respectively. The process devised for BMT CTN 1401 led to rapid patient accrual and successful point-of-care DC/MM fusion vaccine generation. Feasibility of serial sample collection and performance of immunologic correlates were demonstrated. This multi-center collaboration highlights the development of a personalized tumor vaccine platform that serves as a model for future immunotherapy trials in MM.