Establishing measurable residual disease trajectories for patients on treatment for newly diagnosed multiple myeloma as benchmark for deployment of T-cell redirection therapy

Autologous stem cell transplantation (ASCT) has been the prime consolidative strategy to increase the depth and duration of response in newly diagnosed multiple myeloma (NDMM), albeit with short- and long-term toxicities. Minimal residual disease (MRD) is an important early response endpoint correlating with clinically meaningful outcomes and may be used to isolate the effect of ASCT. We report the impact of ASCT on MRD burden and generate a benchmark for evaluation of novel treatments as consolidation. We collected MRD by next generation sequencing (NGS; clonoSEQ®) post induction and post-ASCT in consecutive patients (N = 330, quadruplet, N = 279; triplet, N = 51). For patients receiving quadruplets, MRD < 10^-5 post-induction was 29% (MRD < 10^-6 15%) increasing to 59% post-ASCT (MRD < 10^-6 45%). Among patients with MRD > 10^-5 post-induction, ASCT lowered the MRD burden>1 log₁₀ for 69% patients. The use of quadruplet induction (vs. triplet) did not reduce the effect of ASCT on MRD burden. Reduction in MRD burden with ASCT was most pronounced in patients with high-risk chromosome abnormalities.This dataset provides granular data to delineate the impact of ASCT on MRD as legacy consolidative strategy in NDMM and provides an important benchmark for evaluation of efficacy of TCRT as experimental consolidative strategy.