A Study of Tbo-Filgrastim (Granix) to Disrupt the Bone Marrow Microenvironment in Patients with Multiple Myeloma Undergoing Autologous Stem Cell Transplantation

Multiple myeloma is the second most common hematologic malignancy in the US. The current standard of care for transplant eligible patients is therapy with high-dose melphalan (HDM) followed by autologous stem cell transplant (ASCT). Although ASCT improves progression-free (PFS) and overall survival (OS), it is not curative and virtually all patients will relapse. Attempts to improve upon HDM by adding other agents to transplant protocols have largely resulted in unacceptable increases in toxicity. Preclinical studies performed by our group suggest that granulocyte-stimulating factor (G-CSF) disrupts the bone marrow microenvironment, resulting in a striking loss of plasmablasts, plasma cells, and decreased expression of chemokine/cytokines contributing to plasma cell maintenance. Tbo-filgrastim (Granix, Teva Pharmaceuticals) is a recombinant methionyl human granulocyte colony-stimulating factor. We hypothesized that tbo-filgrastim treatment may provide a potent and well-tolerated method to disrupt the ‘myeloma cell niche’, rendering patients more sensitive to HDM. Methods: Here, we report results from an open label, single center, phase II randomized study to test the efficacy and safety of tbo-filgrastim plus HDM (tbo-filgrastim arm) versus HDM alone (SOC arm) prior to ASCT (NCT02112045). Patients were randomized 1:1 to tbo-filgrastim on Day -7 through Day -2 (480 or 960 mcg/day, based on weight) and melphalan on Day -2 prior to ASCT (140 or 200 mg/m2, based on age) or melphalan alone. The primary objective was to compare CR rate at day 100. Secondary objectives included comparison of the toxicity, overall response rate, PFS, OS, and rate of neutrophil and platelet engraftment between the two arms. Eligible patients were ≥18 years with symptomatic multiple myeloma enrolled within 12 months of receiving at least 2 cycles of any systemic therapy, were undergoing their first ASCT, and had an adequate ASCT collection product (at least 2 million CD34+ cells/kg). Target enrollment was 176 patients, with an interim analysis of efficacy and futility planned after 88 patients reached Day 100 post-ASCT. Early stopping rules for unacceptable toxicity were in place. Responses were evaluated by IMWG criteria. Results: Ninety patients were enrolled (median age 59.5, range 33 to 77) and 89 were evaluable for response. The early stopping rules for toxicity were not met. The planned interim analysis showed that the proportion of patients in CR at Day 100 was similar betwee