B cell maturation antigen (BCMA) target loss is considered to be a rare event that mediates multiple myeloma (MM) resistance to anti-BCMA chimeric antigen receptor T cell (CAR T) or bispecific T cell engager (TCE) therapies. Emerging data report that downregulation of G-protein-coupled receptor family C group 5 member D (GPRC5D) protein often occurs at relapse after anti-GPRC5D CAR T therapy. To examine the tumor-intrinsic factors that promote MM antigen escape, we performed combined bulk and single-cell whole-genome sequencing and copy number variation analysis of 30 patients treated with anti-BCMA and/or anti-GPRC5D CAR T/TCE therapy. In two cases, MM relapse post-TCE/CAR T therapy was driven by BCMA-negative clones harboring focal biallelic deletions at the TNFRSF17 locus at relapse or by selective expansion of pre-existing subclones with biallelic TNFRSF17 loss. In another five cases of relapse, newly detected, nontruncating, missense mutations or in-frame deletions in the extracellular domain of BCMA negated the efficacies of anti-BCMA TCE therapies, despite detectable surface BCMA protein expression. In the present study, we also report four cases of MM relapse with biallelic mutations of GPRC5D after anti-GPRC5D TCE therapy, including two cases with convergent evolution where multiple subclones lost GPRC5D through somatic events. Immunoselection of BCMA- or GPRC5D-negative or mutant clones is an important tumor-intrinsic driver of relapse post-targeted therapies. Mutational events on BCMA confer distinct sensitivities toward different anti-BCMA therapies, underscoring the importance of considering the tumor antigen landscape for optimal design and selection of targeted immunotherapies in MM.

Chimeric antigen receptor (CAR) T-cell therapies are highly effective for multiple myeloma (MM) but their impressive efficacy is associated with treatment-related neurotoxicities in some patients. In CARTITUDE-1, 5% of patients with MM reported movement and neurocognitive treatment-emergent adverse events (MNTs) with ciltacabtagene autoleucel (cilta-cel), a B-cell maturation antigen-targeted CAR T-cell therapy. We assessed the associated factors for MNTs in CARTITUDE-1. Based on common features, patients who experienced MNTs were characterized by the presence of a combination of at least two variables: high tumor burden, grade ≥2 cytokine release syndrome (CRS) or any grade immune effector cell-associated neurotoxicity syndrome (ICANS) after cilta-cel infusion, and high CAR T-cell expansion/persistence. Strategies were implemented across the cilta-cel development program to monitor and manage patients with MNTs, including enhanced bridging therapy to reduce baseline tumor burden, early aggressive treatment of CRS and ICANS, handwriting assessments for early symptom detection, and extended monitoring/reporting time for neurotoxicity beyond 100 days post-infusion. After successful implementation of these strategies, the incidence of MNTs was reduced from 5% to <1% across the cilta-cel program, supporting its favorable benefit–risk profile for treatment of MM.

Despite treatment advances, patients with multiple myeloma (MM) often progress through standard drug classes including proteasome inhibitors (PIs), immunomodulatory drugs (IMiDs), and anti-CD38 monoclonal antibodies (mAbs). LocoMMotion (ClinicalTrials.gov identifier: NCT04035226) is the first prospective study of real-life standard of care (SOC) in triple-class exposed (received at least a PI, IMiD, and anti-CD38 mAb) patients with relapsed/refractory MM (RRMM). Patients (N = 248; ECOG performance status of 0–1, ≥3 prior lines of therapy or double refractory to a PI and IMiD) were treated with median 4.0 (range, 1–20) cycles of SOC therapy. Overall response rate was 29.8% (95% CI: 24.2–36.0). Median progression-free survival (PFS) and median overall survival (OS) were 4.6 (95% CI: 3.9–5.6) and 12.4 months (95% CI: 10.3–NE). Treatment-emergent adverse events (TEAEs) were reported in 83.5% of patients (52.8% grade 3/4). Altogether, 107 deaths occurred, due to progressive disease (n = 74), TEAEs (n = 19), and other reasons (n = 14). The 92 varied regimens utilized demonstrate a lack of clear SOC for heavily pretreated, triple-class exposed patients with RRMM in real-world practice and result in poor outcomes. This supports a need for new treatments with novel mechanisms of action.

Immuno‐oncology therapies engage the immune system to treat cancer. BiTE (bispecific T‐cell engager) technology is a targeted immuno‐oncology platform that connects patients' own T cells to malignant cells. The modular nature of BiTE technology facilitates the generation of molecules against tumor‐specific antigens, allowing off‐the‐shelf immuno‐oncotherapy. Blinatumomab was the first approved canonical BiTE molecule and targets CD19 surface antigens on B cells, making blinatumomab largely independent of genetic alterations or intracellular escape mechanisms. Additional BiTE molecules in development target other hematologic malignancies (eg, multiple myeloma, acute myeloid leukemia, and B‐cell non‐Hodgkin lymphoma) and solid tumors (eg, prostate cancer, glioblastoma, gastric cancer, and small‐cell lung cancer). BiTE molecules with an extended half‐life relative to the canonical BiTE molecules are also being developed. Advances in immuno‐oncology made with BiTE technology could substantially improve the treatment of hematologic and solid tumors and offer enhanced activity in combination with other treatments.

Bispecific antibodies (BsAbs) are emerging as an important novel class of immunotherapeutic agents for the treatment of multiple myeloma (MM), and are set to be more widely used in clinical practice. However, this new class of therapies is associated with a distinct adverse event (AE) profile that includes cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome, as well as AEs leading to increased infection risk such as cytopenias and hypogammaglobulinemia, and infections themselves. As preliminary data with this class of agents shows an increased risk of infections as compared with conventional MM treatment regimens, such as immunomodulatory drugs, proteasome inhibitors, and anti-CD38 monoclonal antibodies (mAbs), guidance on infection monitoring, prophylaxis and treatment is required. This review provides consensus recommendations from a panel of 13 global experts, following a meeting in August 2022. The meeting objective was to review existing literature and identify relevant information on infections with all BsAbs in patients with MM, as well as to discuss clinical experience of experts in managing these infections. The recommendations outlined here can be used to guide management of infection risk factors, such as hypogammaglobulinemia and neutropenia. In addition, they can be used to guide the monitoring, prophylaxis, and treatment of bacterial, viral and fungal infections, including emerging infections of interest, such as coronavirus 2019 (COVID-19), and the use of vaccinations prior to and during BsAb treatment. The recommendations have been graded by the panel based on level of data available. Key recommendations include universal herpes simplex and varicella zoster virus prophylaxis, screening for hepatitis B virus reactivation risk in all patients, monthly intravenous immunoglobulin treatment for immunoparesis and in the absence of life-threatening infectious manifestations, use of colony-stimulating factors in patients with Grade 3 neutropenia, universal pneumocystis jirovecii pneumonia prophylaxis and no routine anti-fungal prophylaxis.