Tumor-secreted extracellular vesicles counteract therapy response by triggering inflammatory mesenchymal stem cell development.

PURPOSE: Therapy resistance is a major clinical hurdle in bone cancer treatment and seems to be largely driven by poorly understood microenvironmental factors. Recent evidence suggests a critical role for a unique subpopulation of mesenchymal stem cells with inflammatory features (iMSCs), though their origin and function remained unexplored. We demonstrate that cancer-secreted extracellular vesicles (EVs) trigger the development of iMSCs, which hinder therapy response in vivo, and set out to identify strategies to counteract their function. EXPERIMENTAL DESIGN: The role of iMSCs in therapy resistance was evaluated in an orthotopic xenograft mouse model of osteosarcoma. EV-induced alterations of the MSC transcriptome were analyzed and compared with scRNA-seq data of osteosarcoma and multiple myeloma patient biopsies. Functional assays identified EV components driving iMSC development. We assessed the efficacy of clinical drugs in blocking iMSC-induced resistance in vivo. RESULTS: We found that iMSCs are induced by interaction with cancer EVs and completely abrogate the antimetastatic effect of TGFb signaling inhibition. Importantly, EV-induced iMSCs faithfully recapitulate the inflammatory single-cell RNA signature of stromal cells enriched in multiple myeloma and osteosarcoma patient biopsies. Mechanistically, cancer EVs act through two distinct mechanisms. EV-associated TGFb induces IL6 production, while the EV-RNA cargo enhances TLR3-mediated chemokine production. We reveal that simultaneous blockade of downstream EV-activated pathways with ladarixin and tocilizumab disrupts metastasis formation and overcomes iMSC-induced resistance. CONCLUSIONS: Our observations establish iMSCs as major contributors to drug resistance, reveal EVs as physiological triggers of iMSC development and highlight a promising combination strategy to improve therapy response in bone cancer patients.

T-cell redirecting bispecific antibody treatment in multiple myeloma: current knowledge and future strategies for sustained T-cell engagement.

INTRODUCTION: T-cell redirecting bispecific antibodies (BsAbs), targeting B-cell maturation antigen (BCMA) or G-protein - coupled receptor class C group 5 member D (GPRC5D), are efficacious new agents for the treatment of patients with relapsed or refractory MM. AREAS COVERED: This review discusses the pharmacokinetic properties, efficacy and safety profile of T-cell redirecting BsAbs in MM, with a special focus on their optimal dosing schedule, resistance mechanisms and future strategies to enhance efficacy, reduce toxicity and maximize duration of response. EXPERT OPINION: To further improve the efficacy of BsAbs, ongoing studies are investigating whether combination therapy can enhance depth and duration of response. An important open question is also to what extent response to BsAbs can be improved when these agents are used in earlier lines of therapy. In addition, more evidence is needed on rational de-intensification strategies of BsAb dosing upon achieving a sufficient response, and if (temporary) treatment cessation is possible in patients who have achieved a deep remission (e.g. complete response or minimal residual disease-negative status).

Dose selection of novel anticancer drugs: exposing the gap between selected and required doses.

Historically, dose selection of anticancer drugs has mainly been based on establishing the maximum tolerated dose in phase 1 clinical trials with a traditional 3 plus 3 design. In the era of targeted therapies and immune-modulating agents, this approach does not necessarily lead to selection of the most favourable dose. This strategy can introduce potentially avoidable toxicity or inconvenience for patients. Multiple changes in drug development could lead to more rational dose selection, such as use of better predictive preclinical models, adaptive and randomised trial design, evaluation of multiple dose levels in late-phase development, assessment of target activity and saturation, and early biomarker use for efficacy and safety evaluation. In this Review, we evaluate the rationale and validation of dose selection in each phase of drug development for anticancer drugs approved by the European Medicines Agency and US Food and Drug Administration from Jan 1, 2020, to June 30, 2023, and give recommendations for dose optimisation to improve safety and patient convenience. In our evaluation, we classified 20 (65%) of the 31 recently registered anticancer agents as potential candidates for dose optimisation, which could be achieved either by reducing the dose (n=10 [32%]) or adjusting the dosage regimen (n=10 [32%]). Dose selection seemed to be adequately justified for nine (29%) of the drugs, whereas the reviewed data were inconclusive for formulating a recommendation on dose optimisation for two (6%) of the drugs.

Preclinical activity of allogeneic SLAMF7-specific CAR T-cells (UCARTCS1) in multiple myeloma.

BACKGROUND: Autologous BCMA-specific CAR T-cell therapies have substantial activity in multiple myeloma (MM). However, due to logistical limitations and BCMAlow relapses, there is a need for alternatives. UCARTCS1 cells are 'off-the-shelf' allogeneic CAR T-cells derived from healthy donors targeting SLAMF7 (CS1), which is highly expressed in MM cells. In this study, we evaluated the preclinical activity of UCARTCS1 in MM cell lines, in bone marrow (BM) samples obtained from MM patients and in an MM mouse model. METHODS: Luciferase-transduced MM cell lines were incubated with UCARTCS1 cells or control (non-transduced, SLAMF7/TCRαß double knock-out) T-cells at different effector to target ratios for 24 hours. MM cell lysis was assessed by bioluminescence. Anti-MM activity of UCARTCS1 was also evaluated in 29 BM samples obtained from newly diagnosed patients (n=10), daratumumab-naïve relapsed/refractory patients (n=10) and daratumumab-refractory patients (n=9) in 24-hour flow cytometry-based cytotoxicity assays. Finally, UCARTCS1 activity was assessed in mouse xenograft models. RESULTS: UCARTCS1 cells induced potent CAR-mediated, and dose-dependent lysis of both MM cell lines and primary MM cells. There was no difference in ex vivo activity of UCARTCS1 between heavily pretreated and newly diagnosed patients. In addition, efficacy of UCARTCS1 was not affected by SLAMF7 expression level on MM cells, proportion of tumor cells, or frequency of regulatory T-cells in BM samples obtained from MM patients. UCARTCS1 treatment eliminated SLAMF7+ non-malignant immune cells in a dose-dependent manner, however lysis of normal cells was less pronounced compared to that of MM cells. Additionally, durable anti-MM responses were observed with UCARTCS1 in an MM xenograft model. CONCLUSIONS: These results demonstrate that UCARTCS1 has potent anti-MM activity against MM cell lines and primary MM cells, as well as in an MM xenograft model and support the evaluation of UCARTCS1 in patients with advanced MM.

Mechanisms of resistance against T-cell engaging bispecific antibodies in multiple myeloma: implications for novel treatment strategies.

Off-the-shelf T-cell-redirecting bispecific antibodies targeting BCMA, GPRC5D, and FcRH5 have high activity in multiple myeloma with a manageable toxicity profile. However, not all patients respond to bispecific antibodies and patients can develop bispecific antibody resistance after an initial response. Mechanisms that contribute to bispecific antibody resistance are multifactorial and include tumour-related factors, such as high tumour burden, expression of T-cell inhibitory ligands, and antigen loss. Resistance due to antigen escape can be prevented by simultaneously targeting two tumour-associated antigens with a trispecific antibody or a combination of two bispecific antibodies. There is also increasing evidence that primary resistance to bispecific antibodies is associated with impaired baseline T-cell function. Long-term exposure to bispecific antibodies with chronic T-cell stimulation further aggravates T-cell dysfunction, which could contribute to failure of disease control. Therapeutic interference with T-cell exhaustion by targeting inhibitory or costimulatory pathways could improve bispecific antibody-mediated antitumour activity. The immunosuppressive microenvironment also contributes to bispecific antibody resistance. CD38-targeting antibodies hold promise as combination partners for bispecific antibodies because of their potential to eliminate CD38+ immune suppressor cells. In conclusion, a better understanding of the mechanisms underlying the absence of disease response has provided novel insights to optimise T-cell activity and bispecific antibody efficacy in multiple myeloma.

Clinical Management of Patients With Relapsed/Refractory Multiple Myeloma Treated With Talquetamab.

BACKGROUND: Talquetamab is a bispecific antibody targeting the multiple myeloma-associated antigen G protein-coupled receptor family C group 5 member D (GPRC5D). In the phase 1/2 MonumenTAL-1 trial (NCT03399799/NCT04634552), overall responses rates were > 71% in patients with triple-class exposed relapsed/refractory multiple myeloma (RRMM). Due to the distribution of the target antigen, a unique pattern of GPRC5D-associated adverse events (AEs) was observed, together with T-cell redirection-associated AEs. Management strategies for talquetamab-associated AEs are described. DISCUSSION: GPRC5D-associated AEs included dermatologic (rash, nonrash, and nail toxicities) and oral AEs (dysgeusia, dysphagia, and dry mouth). The incidence of cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) were consistent with other T-cell redirection therapies. The incidence of high-grade infections was lower than observed with B-cell maturation antigen-targeting bispecific antibodies, with less frequent use of intravenous immunoglobulin required. GPRC5D-associated AEs were mostly low grade and led to few discontinuations. Skin toxicities were managed with emollients, topical corticosteroids, and oral corticosteroids (for high-grade, persistent, or AEs that progress). Nail toxicities were commonly managed with emollients. Based on investigator experience, dose modification may be effective for controlling oral events. Observation for potential weight changes is required. Infections were managed per standard of care. CRS and ICANS were effectively managed, consistent with other trials of T-cell redirection therapies. CONCLUSION: Although talquetamab had a distinct safety profile, AEs were considered clinically manageable and mostly low grade. With appropriate education and support, health care practitioners can ensure patients with RRMM maintain quality of life and treatment adherence.

Pharmacodynamic changes in tumor and immune cells drive iberdomide's clinical mechanisms of activity in relapsed and refractory multiple myeloma.

Iberdomide is a next-generation cereblon (CRBN)-modulating agent in the clinical development in multiple myeloma (MM). The analysis of biomarker samples from relapsed/refractory patients enrolled in CC-220-MM-001 (ClinicalTrials.gov: NCT02773030), a phase 1/2 study, shows that iberdomide treatment induces significant target substrate degradation in tumors, including in immunomodulatory agent (IMiD)-refractory patients or those with low CRBN levels. Additionally, some patients with CRBN genetic dysregulation who responded to iberdomide have a similar median progression-free survival (PFS) (10.9 months) and duration of response (DOR) (9.5 months) to those without CRBN dysregulation (11.2 month PFS, 9.4 month DOR). Iberdomide treatment promotes a cyclical pattern of immune stimulation without causing exhaustion, inducing a functional shift in T cells toward an activated/effector memory phenotype, including in triple-class refractory patients and those receiving IMiDs as a last line of therapy. This analysis demonstrates that iberdomide's clinical mechanisms of action are driven by both its cell-autonomous effects overcoming CRBN dysregulation in MM cells, and potent immune stimulation that augments anti-tumor immunity.

Decline in Smartphone-Assessed Physical Activity Level is Associated With Clinical Outcomes in Phase I/II Clinical Cancer Trials.

BACKGROUND: A decline in physical function may be an early predictor for complications of cancer treatment. This study examined whether repeated objective smartphone measurements of physical activity and exercise capacity in patients with cancer are feasible during early-phase clinical trials (EPCTs) and whether a decline in physical function is associated with clinical outcomes. METHODS: Physical activity (steps/day) and exercise capacity (6-minute walk test [6MWT]) were measured with a smartphone before EPCT start (T0) and after 4 weeks (T1) and 8 weeks (T2). Univariable logistic regression analyzed associations between a decline in step count (≥20%), 6MWT distance (≥10%), or deterioration of ECOG performance status (PS) and trial discontinuation at 8 weeks and 90 days. Cox proportional hazards models were used to examine associations with progression-free survival (PFS) and overall survival (OS), adjusting for trial phase (I vs II), cancer type (hematologic malignancy vs solid tumor), and PS (0 vs ≥1). RESULTS: Among 117 included patients, valid step count and 6MWT measurements were available for 96.6% and 76.7% of patients at T0, 74.4% and 53.3% at T1, and 89.7% and 54.4% at T2, respectively. Patients experiencing step count decline between T0 and T1 had higher odds of trial discontinuation at 8 weeks (odds ratio, 8.67; 95% CI, 1.94-61.43), and decline between T1 and T2 was associated with discontinuation at 90 days (odds ratio, 5.20; 95% CI, 1.43-21.14). Step count decline was significantly associated with shorter PFS (hazard ratio, 3.54; 95% CI, 2.06-6.08) and OS (hazard ratio, 2.31; 95% CI, 1.26-4.23). Declines in 6MWT distance or deterioration in ECOG PS were not associated with trial discontinuation or survival. CONCLUSIONS: Repeated smartphone measurements of physical activity are feasible in patients participating in EPCTs. Additionally, physical activity decline is significantly associated with trial discontinuation, PFS, and OS. Hence, we envision that objective smartphone measurements of physical activity will contribute to optimal treatment development for patients with cancer.

International Myeloma Working Group immunotherapy committee consensus guidelines and recommendations for optimal use of T-cell-engaging bispecific antibodies in multiple myeloma.

Multiple myeloma remains an incurable disease, despite the development of numerous drug classes and combinations that have contributed to improved overall survival. Immunotherapies directed against cancer cell-surface antigens, such as chimeric antigen receptor (CAR) T-cell therapy and T-cell-redirecting bispecific antibodies, have recently received regulatory approvals and shown unprecedented efficacy. However, these immunotherapies have unique mechanisms of action and toxicities that are different to previous treatments for myeloma, so experiences from clinical trials and early access programmes are essential for providing specific recommendations for management of patients, especially as these agents become available across many parts of the world. Here, we provide expert consensus clinical practice guidelines for the use of bispecific antibodies for the treatment of myeloma. The International Myeloma Working Group is also involved in the collection of prospective real-time data of patients treated with such immunotherapies, with the aim of learning continuously and adapting clinical practices to optimise the management of patients receiving immunotherapies.

T-Cell Characteristics Impact Response and Resistance to T-Cell-Redirecting Bispecific Antibodies in Multiple Myeloma.

PURPOSE: Bispecific antibodies (BsAb) directed against B-cell maturation antigen (teclistamab) or the orphan G protein-coupled receptor GPRC5D (talquetamab) induce deep and durable responses in heavily pretreated patients with multiple myeloma. However, mechanisms underlying primary and acquired resistance remain poorly understood. EXPERIMENTAL DESIGN: The anti-multiple myeloma activity of teclistamab and talquetamab was evaluated in bone marrow (BM) samples from patients with multiple myeloma. T-cell phenotype and function were assessed in BM/peripheral blood samples obtained from patients with multiple myeloma who were treated with these BsAb. RESULTS: In ex vivo killing assays with 41 BM samples from BsAb-naive patients with multiple myeloma, teclistamab- and talquetamab-mediated multiple myeloma lysis was strongly correlated (r = 0.73, P < 0.0001). Both BsAb exhibited poor activity in samples with high regulatory T-cell (Treg) numbers and a low T-cell/multiple myeloma cell ratio. Furthermore, comprehensive phenotyping of BM samples derived from patients treated with teclistamab or talquetamab revealed that high frequencies of PD-1+ CD4+ T cells, CTLA4+ CD4+ T cells, and CD38+ CD4+ T cells were associated with primary resistance. Although this lack of response was linked to a modest increase in the expression of inhibitory receptors, increasing T-cell/multiple myeloma cell ratios by adding extra T cells enhanced sensitivity to BsAb. Further, treatment with BsAb resulted in an increased proportion of T cells expressing exhaustion markers (PD-1, TIGIT, and TIM-3), which was accompanied by reduced T-cell proliferative potential and cytokine secretion, as well as impaired antitumor efficacy in ex vivo experiments. CONCLUSIONS: Primary resistance is characterized by a low T-cell/multiple myeloma cell ratio and Treg-driven immunosuppression, whereas reduced T-cell fitness due to continuous BsAb-mediated T-cell activation may contribute to the development of acquired resistance.

Practical Aspects of Immunotherapy: A Report from the 20th International Myeloma Society (IMS) Annual Meeting.

Immunotherapeutic strategies, specifically T-cell-redirected therapies, have been transformative in the context of multiple myeloma (MM). With the approval of two chimeric antigen receptor T-cell (CAR-T) drug products and three bispecific antibodies/T-cell engagers (bsAbs/TCEs) in relapsed/refractory MM (RRMM), the 20th annual IMS meeting dedicated a session to the practical aspects of these therapies. Here, we highlight the discussion during this session, including the role of CAR-T and bsAb therapies in frontline MM treatment, management of acute toxicities, prevention and management of infections, and finally treatment sequencing of T-cell redirected therapies.

Correlation of immune fitness with response to teclistamab in relapsed/refractory multiple myeloma in the MajesTEC-1 study.

ABSTRACT: Teclistamab, an off-the-shelf B-cell maturation antigen (BCMA) × CD3 bispecific antibody that mediates T-cell activation and subsequent lysis of BCMA-expressing myeloma cells, is approved for the treatment of patients with relapsed/refractory multiple myeloma (R/RMM). As a T-cell redirection therapy, clinical outcomes with teclistamab may be influenced by patient immune fitness and tumor antigen expression. We correlated tumor characteristics and baseline immune profiles with clinical response and disease burden in patients with R/RMM from the pivotal phase 1/2 MajesTEC-1 study, focusing on patients treated with 1.5 mg/kg of teclistamab (N = 165). Peripheral blood samples were collected at screening, and bone marrow samples were collected at screening and cycle 3. Better clinical outcomes to teclistamab correlated with higher baseline total T-cell counts in the periphery. In addition, responders (partial response or better) had a lower proportion of immunosuppressive regulatory T cells (Tregs), T cells expressing coinhibitory receptors (CD38, PD-1, and PD-1/TIM-3), and soluble BCMA and a T-cell profile suggestive of a more cytolytic potential, compared with nonresponders. Neither frequency of baseline bone marrow BCMA expression nor BCMA-receptor density was associated with clinical response to teclistamab. Improved progression-free survival was observed in patients with a lower frequency of T cells expressing exhaustion markers and immunosuppressive Tregs. Overall, response to teclistamab was associated with baseline immune fitness; nonresponders had immune profiles suggestive of immune suppression and T-cell dysfunction. These findings illustrate the importance of the contribution of the immune landscape to T-cell redirection therapy response. This trial was registered at www.ClinicalTrials.gov as #NCT03145181/NCT04557098.

GPRC5D as a novel target for the treatment of multiple myeloma: a narrative review.

Multiple myeloma is a genetically complex and heterogenous malignancy with a 5-year survival rate of approximately 60%. Despite advances in therapy, patients experience cycles of remission and relapse, with each successive line of therapy associated with poorer outcomes; therefore, therapies with different mechanisms of action against new myeloma antigens are needed. G protein-coupled receptor class C group 5 member D (GPRC5D) has emerged as a novel therapeutic target for the treatment of multiple myeloma. We review the biology and target validation of GPRC5D, and clinical data from early phase trials of GPRC5D-targeting bispecific antibodies, talquetamab and forimtamig, and chimeric antigen receptor T cell (CAR-T) therapies, MCARH109, OriCAR-017, and BMS-986393. In addition to adverse events (AEs) associated with T-cell-redirection therapies irrespective of target, a consistent pattern of dermatologic and oral AEs has been reported across several trials of GPRC5D-targeting bispecific antibodies, as well as rare cerebellar events with CAR-T therapy. Additional studies are needed to understand the underlying mechanisms involved in the development of skin- and oral-related toxicities. We review the strategies that have been used to manage these GPRC5D-related toxicities. Preliminary efficacy data showed overall response rates for GPRC5D-targeting T-cell-redirecting therapies were ≥64%; most responders achieved a very good partial response or better. Pharmacokinetics/pharmacodynamics showed that these therapies led to cytokine release and T-cell activation. In conclusion, results from early phase trials of GPRC5D-targeting T-cell-redirecting agents have shown promising efficacy and manageable safety profiles, including lower infection rates compared with B-cell maturation antigen- and Fc receptor-like protein 5-targeting bispecific antibodies. Further clinical trials, including those investigating GPRC5D-targeting T-cell-redirecting agents in combination with other anti-myeloma therapies and with different treatment modalities, may help to elucidate the future optimal treatment regimen and sequence for patients with multiple myeloma and improve survival outcomes. Video Summary.

Comparative Efficacy of Talquetamab vs. Current Treatments in the LocoMMotion and MoMMent Studies in Patients with Triple-Class-Exposed Relapsed/Refractory Multiple Myeloma.

INTRODUCTION: Talquetamab, a bispecific antibody targeting GPRC5D × CD3, is approved for the treatment of patients with triple-class -exposed (TCE) relapsed/refractory multiple myeloma (RRMM) on the basis of the results from the phase I/II MonumenTAL-1 trial. The relative effectiveness of talquetamab vs. real-world physician's choice of therapy (RWPC) was assessed using adjusted comparisons. METHODS: An external control arm for MonumenTAL-1 (subcutaneously administered talquetamab 0.4 mg/kg weekly [QW] and 0.8 mg/kg every other week [Q2W]) was created from two observational real-world studies: LocoMMotion and MoMMent. Imbalances in baseline covariates were adjusted using inverse probability weighting. The relative effectiveness of talquetamab vs. RWPC was estimated for overall response rate (ORR), ≥ very good partial response (VGPR), and ≥ complete response (CR); odds ratios and relative response ratios (RRs) were derived from weighted logistic regression. Hazard ratios (HRs) for duration of response (DOR), progression-free survival (PFS), time to next treatment (TTNT), and overall survival (OS) were estimated using a weighted Cox proportional hazards model. RESULTS: After reweighting, baseline characteristics were balanced across cohorts. In adjusted comparisons, patients treated with talquetamab QW (n = 143) had significantly improved outcomes vs. RWPC; RRs were ORR 2.67, p < 0.0001; ≥ VGPR 4.70, p < 0.0001; ≥ CR 78.05, p = 0.0002; and HRs were PFS 0.52, p < 0.0001; TTNT 0.48, p < 0.0001; OS 0.36, p < 0.0001. Patients treated with talquetamab Q2W (n = 145) also had significantly improved outcomes vs. RWPC; RRs were ORR 2.62, p < 0.0001; ≥ VGPR 5.04, p < 0.0001; ≥ CR 101.14, p = 0.0002; and HRs were PFS 0.40, p < 0.0001; TTNT 0.39, p < 0.0001; OS 0.37, p < 0.0001. CONCLUSION: Effectiveness of talquetamab for both schedules was significantly better than RWPC for ORR, ≥ VGPR, ≥ CR, PFS, OS, and TTNT, highlighting its clinical benefit for patients with TCE RRMM. TRIAL REGISTRATION: MonumenTAL-1, ClinicalTrials.gov identifier NCT03399799/NCT04634552; LocoMMotion, ClinicalTrials.gov identifier NCT04035226; MoMMent, ClinicalTrials.gov identifier NCT05160584.

Incidence, timing, and management of infections in patients receiving teclistamab for the treatment of relapsed/refractory multiple myeloma in the MajesTEC-1 study.

BACKGROUND: Patients with relapsed/refractory multiple myeloma are at increased risk of infection. Infections during treatment with teclistamab, the first B-cell maturation antigen-directed bispecific antibody approved for triple-class-exposed relapsed/refractory multiple myeloma, was examined in the phase 1/2 MajesTEC-1 study. METHODS: Patients (N = 165) received subcutaneous teclistamab 1.5 mg/kg weekly after a step-up dosing schedule (0.06 mg/kg and 0.3 mg/kg, each separated by 2-4 days). Patients were monitored frequently for infections; prophylaxis and management were per institutional guidelines. RESULTS: At a median follow-up of 22.8 months (range, 0.3-33.6), infections were reported in 132 patients (80.0%). Grade 3/4 infections occurred in 91 patients (55.2%), including COVID-19 (21.2%), respiratory infections (19.4%), Pneumocystis jirovecii pneumonia (4.2%), viral infections (4.2%), and gastrointestinal infections (1.2%). Twenty-one patients died from infections (18 from COVID-19). Median time to first onset of any-grade and grade 3 to 5 infections was 1.7 and 4.2 months, respectively. Overall, 70.9% of patients had ≥1 postbaseline immunoglobulin G (IgG) level <400 mg/dL; median time to IgG <400 mg/dL was 1.2 months (range, 0.2-19.8) and 46.1% received ≥1 dose of IgG replacement. Grade 3/4 neutropenia occurred in 65.5% of patients (median time to grade ≥3 neutropenia/febrile neutropenia was 2.3 months [range, 0-18.1]). CONCLUSION: Based on the infection profile of B-cell maturation antigen-targeted bispecific antibodies such as teclistamab, it is recommended that clinicians and patients remain vigilant for a range of infection types throughout treatment to facilitate prompt intervention. Appropriate screening, prophylaxis, and management of infections, hypogammaglobulinemia, and neutropenia are important. CLINICAL TRIAL REGISTRATION: NCT03145181/NCT04557098 (ClinicalTrials.gov) PLAIN LANGUAGE SUMMARY: Before starting teclistamab, patients should be up to date with vaccinations (including COVID-19) and screened for hepatitis B and C and HIV. Teclistamab should not be given to patients with any active infections. Prophylactic antimicrobials should be administered per institutional guidelines. Prophylaxis for Pneumocystis jirovecii pneumonia and herpes simplex/varicella zoster virus is recommended during teclistamab treatment. Close monitoring of infections and immunoglobulin G (IgG) levels should continue throughout teclistamab treatment. IgG replacement (administered every 3-6 weeks) should be used to maintain IgG ≥400 mg/dL. Growth factors should be considered for grade ≥3 neutropenia with infection/fever and grade 4 neutropenia.