Antigen escape as a shared mechanism of resistance to BCMA-directed therapies in multiple myeloma

B-cell maturation antigen (BCMA)-targeting therapeutics have dramatically improved outcomes in relapsed/refractory multiple myeloma (RRMM). However, whether the mechanisms of resistance between these therapies are shared and how the identification of such mechanisms before therapy initiation could refine clinical decision-making remains undefined. We analyzed outcomes for 72 RRMM patients treated with teclistamab, a CD3 x BCMA bispecific antibody (BsAb), 42% (30/72) of whom had prior BCMA-directed therapy exposure. Malignant plasma cell BCMA expression was present in all BCMA therapy-naïve patients. Prior therapy-mediated loss of plasma cell BCMA expression before teclistamab treatment, measured by immunohistochemistry, was observed in 3 patients, none of whom responded to teclistamab, and one of whom also did not respond to ciltacabtagene autoleucel. Whole exome sequencing of tumor DNA from one patient revealed biallelic loss of TNFRSF17 following treatment with belantamab mafodotin. Low-to-undetectable peripheral blood soluble BCMA levels correlated with the absence of BCMA expression by bone marrow plasma cells. Thus, although rare, loss of BCMA expression following TNFRSF17 gene deletions can occur following any BCMA-directed therapy and prevents response to subsequent anti-BCMA-directed treatments, underscoring the importance of verifying the presence of a target antigen.

Unscheduled healthcare interactions in multiple myeloma patients receiving T cell redirection therapies

Outcomes for relapsed/refractory multiple myeloma (RRMM) patients have dramatically improved following the development and now growing utilization of B cell maturation antigen targeted chimeric antigen receptor (CAR) T cell therapy and bispecific antibody (BsAb) therapy. However, healthcare utilization as a quality-of-life metric in these growing populations has not been thoroughly evaluated. We performed a retrospective cohort study evaluating the frequency and cause of unscheduled healthcare interactions (UHIs) among RRMM patients responding to B-cell maturation antigen targeted BsAbs and CAR T cell therapies (N = 46). This included analysis of remote UHIs including calls to physicians' offices and messages sent through an online patient portal. Our results showed that nearly all (89%) RRMM patients receiving these therapies required a UHI during the first 125 days of treatment, with a mean of 3.7 UHIs per patient. RRMM patients responding to BsAbs were significantly more likely to remotely contact their physicians' offices (1.8-fold increase, p = 0.038) or visit an urgent care center (>3-fold increase, p = 0.012) than RRMM patients responding to CAR T cell therapies. This was largely due to increased reports of mild upper respiratory tract infections in BsAb patients. Our results underscore the need to develop preemptive management strategies for commonly reported symptoms that RRMM patients experience while receiving CAR T cell or BsAb therapies. This preemptive management may significantly reduce unnecessary healthcare utilization in this vulnerable patient population.

Patterns of CRS with Teclistamab in Relapsed/Refractory Multiple Myeloma patients with Prior T-Cell Redirection Therapy

Teclistamab (Tec) is a first-in-class BCMA X CD3 bispecific T-cell engager antibody approved for treating multiple myeloma progressing after at least 4 lines of therapy. The objective of this study was to evaluate the rate of cytokine release syndrome (CRS) in patients who were treated with commercial Tec and had prior exposure to other T-cell redirection therapies. A retrospective chart review was performed to identify patients who completed the Tec step-up dosing phase between November 2022 and November 2023. Patients were divided into 2 cohorts based on prior exposure to T-cell redirection therapy (cohort 1: T-cell redirection therapy experienced; cohort 2: T-cell redirection therapy naïve). The primary objective was to compare the differences in the rates of CRS between the two cohorts. Univariate and multivariate logistic regression analyses were performed to assess the association between CRS rates with Tec and prior treatment with T-cell redirection therapy. A total of 72 patients were included in the analysis (27 in cohort 1 and 45 in cohort 2). The CRS rates were significantly lower in cohort 1 (37%, n=10) compared to cohort 2 (80%, n=36; p=0.0004). Based on multivariate logistic regression analysis, patients without prior exposure to T-cell redirection therapy (cohort 2) had about a 4-fold increase in the incidence of CRS (95% CI: 1.40-14.90, p=0.0002) with Tec. In our study, prior exposure to T-cell redirection therapy reduced the risk of CRS with Tec during the step-up dosing phase. This observation will allow for the optimization of CRS prophylactic strategies for Tec.

Accelerated single cell seeding in relapsed multiple myeloma

Multiple myeloma (MM) progression is characterized by the seeding of cancer cells in different anatomic sites. To characterize this evolutionary process, we interrogated, by whole genome sequencing, 25 samples collected at autopsy from 4 patients with relapsed MM and an additional set of 125 whole exomes collected from 51 patients. Mutational signatures analysis showed how cytotoxic agents introduce hundreds of unique mutations in each surviving cancer cell, detectable by bulk sequencing only in cases of clonal expansion of a single cancer cell bearing the mutational signature. Thus, a unique, single-cell genomic barcode can link chemotherapy exposure to a discrete time window in a patient′s life. We leveraged this concept to show that MM systemic seeding is accelerated at relapse and appears to be driven by the survival and subsequent expansion of a single myeloma cell following treatment with high-dose melphalan therapy and autologous stem cell transplant.

In multiple myeloma, disease progresses via seeding to different anatomic sites and clonal expansion. Here, utilising autopsy material, the authors show that systemic seeding accelerates at relapse following treatment.