Purpose: Vaccination with dendritic cell (DC)/multiple myeloma (MM) fusions has been shown to induce the expansion of circulating multiple myeloma–reactive lymphocytes and consolidation of clinical response following autologous hematopoietic cell transplant (auto-HCT). Patients and Methods: In this randomized phase II trial (NCT02728102), we assessed the effect of DC/MM fusion vaccination, GM-CSF, and lenalidomide maintenance as compared with control arms of GM-CSF and lenalidomide or lenalidomide maintenance alone on clinical response rates and induction of multiple myeloma–specific immunity at 1-year posttransplant. Results: The study enrolled 203 patients, with 140 randomized posttransplantation. Vaccine production was successful in 63 of 68 patients. At 1 year, rates of CR were 52.9% (vaccine) and 50% (control; P = 0.37, 80% CI 44.5%, 61.3%, and 41.6%, 58.4%, respectively), and rates of VGPR or better were 85.3% (vaccine) and 77.8% (control; P = 0.2). Conversion to CR at 1 year was 34.8% (vaccine) and 27.3% (control; P = 0.4). Vaccination induced a statistically significant expansion of multiple myeloma–reactive T cells at 1 year compared with before vaccination (P = 0.024) and in contrast to the nonvaccine arm (P = 0.026). Single-cell transcriptomics revealed clonotypic expansion of activated CD8 cells and shared dominant clonotypes between patients at 1-year posttransplant. Conclusions: DC/MM fusion vaccination with lenalidomide did not result in a statistically significant increase in CR rates at 1 year posttransplant but was associated with a significant increase in circulating multiple myeloma–reactive lymphocytes indicative of tumor-specific immunity. Site-specific production of a personalized cell therapy with centralized product characterization was effectively accomplished in the context of a multicenter cooperative group study. See related commentary by Qazilbash and Kwak, p. 4703

Circulating plasma cells (CPCs) have been detected in patients with multiple myeloma (MM) at various stages of disease and associated with worse outcomes. Little data exist regarding the impact of CPCs at the time of autologous peripheral blood stem cell (PBSC) collection on outcomes, and the impact of maintenance therapy after autologous stem cell transplantation (ASCT) on prognosis in patients with CPC-containing collections. All patients with MM who underwent first ASCT at Fred Hutchinson Cancer Research Center from 2012 to 2015 and had evaluation for CPCs at the time of PBSC collection were included in our analysis. Seven-color flow cytometry was used to detect the presence of CPCs. Kaplan-Meier estimates were used to generate overall survival (OS) and progression-free survival (PFS) rates from the time of ASCT. A multivariate analysis, including receipt of maintenance therapy post-ASCT, high-risk cytogenetics, and international staging system (ISS) stage, was included in a Cox proportional hazards regression model for associations with OS and PFS. We identified 227 patients with MM who underwent ASCT; of these, 144 (63.4%) patients had routine assessment of CPCs at the time of PBSC collection. One hundred seventeen (81.3%) patients did not have CPCs and 27 (18.8%) did have CPCs. The presence of CPCs was highly associated with poorer PFS (P = .031 by log-rank analysis), but did not affect OS. The median PFS for those patients without CPCs was 39.4 months (95% confidence interval [CI], 31.1 to not reached), while the median PFS for those patients with CPCs was 16.5 months (95% CI, 13.7 to not reached). A subgroup analysis of patients achieving very good partial response (VGPR) or better at time of collection, showed the median PFS for patients without CPCs was 38.3 months (95% CI, 29 to not reached), as compared with those patients with CPCs, where it was only 16.5 months (95% CI, 12 months to not reached; P = .02). There was no statistically significant difference in PFS or OS among those patients achieving partial response at the time of collection. In a Cox proportional hazards model, adjusting for post-ASCT maintenance therapy, high-risk cytogenetics, and ISS stage at time of initial diagnosis, there was a 43% higher risk of progression or death among the patients with CPCs (P = .04). The presence of CPCs at the time of autologous PBSC collection is a negative prognostic factor for risk of early relapse or death despite the advent of novel agents and maintenance strategies. The impact of CPCs was most significant among patients achieving a VGPR or better at time of collection. The presence of CPCs denotes a unique group of high-risk MM patients for whom alternative treatment strategies are needed to overcome resistance to current standard therapies.

Outcomes with autologous hematopoietic cell transplantation (auto HCT) for relapsed and/or refractory mantle cell lymphoma (MCL) are typically poor. We hypothesized that certain factors could predict which patients experience a favorable outcome with this approach. We thus developed a predictive score from a cohort of 67 such patients using 3 factors independently associated with progression-free survival (PFS): (1) simplified Mantle Cell Lymphoma International Prognostic Index score before auto HCT (hazard ratio [HR], 2.9; P = .002); (2) B symptoms at diagnosis (HR, 2.7; P = .005); and (3) remission quotient, calculated by dividing the time, in months, from diagnosis to auto HCT by the number of prior treatments (HR, 1.4; P = .02). The estimated 5-year PFS for favorable-risk patients (n = 23) and unfavorable-risk patients (n = 44) were 58% (95% confidence interval [CI], 34% to 75%) and 15% (95% CI, 6% to 28%), respectively. These factors also independently predicted overall survival. In summary, we have defined 3 simple factors that can identify patients with relapsed/refractory MCL who derive a durable benefit from salvage auto HCT.

Autologous stem cell transplantation (ASCT) with subsequent lenalidomide maintenance is standard consolidation therapy for multiple myeloma, and a subset of patients achieve durable progression-free survival that is suggestive of long-term immune control. Nonetheless, most patients ultimately relapse, suggesting immune escape. TIGIT appears to be a potent inhibitor of myeloma-specific immunity and represents a promising new checkpoint target. Here we demonstrate high expression of TIGIT on activated CD8⁺ T cells in mobilized peripheral blood stem cell grafts from patients with myeloma. To guide clinical application of TIGIT inhibition, we evaluated identical anti-TIGIT antibodies that do or do not engage FcγR and demonstrated that anti-TIGIT activity is dependent on FcγR binding. We subsequently used CRBN mice to investigate the efficacy of anti-TIGIT in combination with lenalidomide maintenance after transplantation. Notably, the combination of anti-TIGIT with lenalidomide provided synergistic, CD8⁺ T cell–dependent, antimyeloma efficacy. Analysis of bone marrow (BM) CD8⁺ T cells demonstrated that combination therapy suppressed T cell exhaustion, enhanced effector function, and expanded central memory subsets. Importantly, these immune phenotypes were specific to the BM tumor microenvironment. Collectively, these data provide a logical rationale for combining TIGIT inhibition with immunomodulatory drugs to prevent myeloma progression after ASCT.

Since the introduction of lenalidomide into induction therapy for multiple myeloma (MM), there have been conflicting reports about its impact on autologous peripheral blood stem cell (PBSC) mobilization. We evaluated the impact of prior lenalidomide exposure in a large cohort of MM patients undergoing mobilization and collection at a tertiary stem cell transplant center. We hypothesized that collection of PBSCs is feasible even with prolonged duration of prior lenalidomide therapy. We examined patients with MM who attempted stem cell mobilization and collection, seen at our center between January 2012 and July 2015. The patients were categorized into 3 groups for analysis: 1) Those patients with prior receipt of > 6 cycles lenalidomide, 2) Those patients with prior receipt of ≤ 6 cycles of lenalidomide, and 3) Patients without prior lenalidomide exposure. We compared collection yields and days of apheresis amongst the 3 groups using linear regression analysis. We identified 297 patients with MM who underwent mobilization of PBSCs. Of these, 35 received > 6 cycles of lenalidomide (median of 8 cycles, range of 7 - 25), 156 received ≤ 6 cycles of lenalidomide (median of 4 cycles, range 1 - 6), and 106 had received no lenalidomide (Table 1). Prior lenalidomide exposure did not have a statistically significant impact on the absolute number of CD34+ cells collected, nor the length of collection based on a multivariate linear regression analysis for association between receipt of > 6 cycles of lenalidomide. In this retrospective analysis of MM patients undergoing autologous PBSC, we show that duration of prior lenalidomide exposure does not impact the total number of PBSC collected or the number of days of apheresis. These data suggest that longer courses of induction therapy with lenalidomide-containing regimens to achieve a maximum response can be safe without impairing the ability to collect PBSC, and that limiting lenalidomide use pre-mobilization does not appear warranted in all cases.