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).

HOVON 104, long-term follow-up of bortezomib-dexamethasone induction therapy followed by autologous stem cell transplantation in newly diagnosed AL amyloidosis patients.

The HOVON 104 studied bortezomib-dexamethasone induction therapy and autologous stem cell transplantation in 50 patients, of whom 35 received an autologous stem cell transplantation (ASCT). We demonstrate a 5-year overall survival (OS) of 73% and progression-free survival (PFS) of 52% for all 50 patients with a median follow-up of 61.3 months. For the 35 transplanted patients, calculated from the date of ASCT, the 5-year OS and PFS were 91% and 68%, respectively. After ASCT, the rate of organ response improved over time but stabilized around 3 years. A complete cardiac response was seen in around 60% of patients and remained stable from 2 years onward. Reaching complete renal response was slower over time and achieved by 61% of the renal-affected patients at 5 years. We confirm the excellent outcomes after ASCT and demonstrate a 60% complete organ response with longer follow-up.

Mucositis-associated bloodstream infections in adult haematology patients with fever during neutropenia: risk factors and the impact of mucositis severity.

PURPOSE: Haematology patients with high-risk neutropenia are prone to mucosal-barrier injury-associated laboratory-confirmed bloodstream infections (MBI-LCBI). We assessed risk factors for MBI-LCBI including candidaemia in neutropenic haematology patients with fever. METHODS: This prospective observational study was performed in six dedicated haematology units in the Netherlands. Eligible haematology patients had neutropenia < 500/mL for ≥ 7 days and had fever. MBI-LCBIs were classified according to Centers for Disease Control (CDC) definitions and were followed until the end of neutropenia > 500/mL or discharge. RESULTS: We included 416 patients from December 2014 until August 2019. We observed 63 MBI-LCBIs. Neither clinical mucositis scores nor the blood level of citrulline at fever onset was associated with MBI-LCBI. In the multivariable analysis, MASCC-score (odds ratio [OR] 1.16, 95% confidence interval [CI] 1.05 to 1.29 per point decrease), intensive chemotherapy (OR 3·81, 95% CI 2.10 to 6.90) and Pichia kudriavzevii (formerly Candida krusei) colonisation (OR 5.40, 95% CI 1.75 to 16.7) were retained as risk factors for MBI-LCBI, while quinolone use seemed protective (OR 0.42, 95% CI 0.20 to 0.92). Citrulline level (OR 1.57, 95% CI 1.07 to 2.31 per µmol/L decrease), active chronic obstructive pulmonary disease (OR 15.4, 95% CI 1.61 to 14.7) and colonisation with fluconazole-resistant Candida (OR 8.54, 95% CI 1.51 to 48.4) were associated with candidaemia. CONCLUSION: In haematology patients with fever during neutropenia, hypocitrullinaemia at fever onset was associated with candidaemia, but not with bacterial MBI-LCBI. Patients with intensive chemotherapy with a low MASCC-score and colonisation with Pichia kudriavzevii had the highest risk of MBI-LCBI. TRIAL REGISTRATION: ClinicalTrials.gov (NCT02149329) at 19-NOV-2014.

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.

Bortezomib, thalidomide, and dexamethasone with or without daratumumab and followed by daratumumab maintenance or observation in transplant-eligible newly diagnosed multiple myeloma: long-term follow-up of the CASSIOPEIA randomised controlled phase 3 trial.

BACKGROUND: CASSIOPEIA part 1 demonstrated superior depth of response and prolonged progression-free survival with daratumumab in combination with bortezomib, thalidomide, and dexamethasone (D-VTd) versus bortezomib, thalidomide, and dexamethasone (VTd) alone as an induction and consolidation regimen in transplant-eligible patients newly diagnosed with myeloma. In CASSIOPEIA part 2, daratumumab maintenance significantly improved progression-free survival and increased minimal residual disease (MRD)-negativity rates versus observation. Here, we report long-term study outcomes of CASSIOPEIA. METHODS: CASSIOPEIA was a two-part, open-label, phase 3 trial of patients done at 111 European academic and community-based centres. Eligible patients were aged 18-65 years with transplant-eligible newly diagnosed myeloma and an Eastern Cooperative Oncology Group performance status of 0-2. In part 1, patients were randomly assigned (1:1) to pre-transplant induction and post-transplant consolidation with D-VTd or VTd. Patients who completed consolidation and had a partial response or better were re-randomised (1:1) to intravenous daratumumab maintenance (16 mg/kg every 8 weeks) or observation for 2 years or less. An interactive web-based system was used for both randomisations, and randomisation was balanced using permuted blocks of four. Stratification factors for the first randomisation (induction and consolidation phase) were site affiliation, International Staging System disease stage, and cytogenetic risk status. Stratification factors for the second randomisation (maintenance phase) were induction treatment and depth of response in the induction and consolidation phase. The primary endpoint for the induction and consolidation phase was the proportion of patients who achieved a stringent complete response after consolidation; results for this endpoint remain unchanged from those reported previously. The primary endpoint for the maintenance phase was progression-free survival from second randomisation. Efficacy evaluations in the induction and consolidation phase were done on the intention-to-treat population, which included all patients who underwent first randomisation, and efficacy analyses in the maintenance phase were done in the maintenance-specific intention-to-treat population, which included all patients who were randomly assigned at the second randomisation. This analysis represents the final data cutoff at the end of the study. The trial is registered with ClinicalTrials.gov, NCT02541383. FINDINGS: Between Sept 22, 2015 and Aug 1, 2017, 1085 patients were randomly assigned to D-VTd (n=543) or VTd (n=542); between May 30, 2016 and June 18, 2018, 886 were re-randomised to daratumumab maintenance (n=442) or observation (n=444). At the clinical cutoff date, Sept 1, 2023, median follow-up was 80·1 months (IQR 75·7-85·6) from first randomisation and 70·6 months (66·4-76·1) from second randomisation. Progression-free survival from second randomisation was significantly longer in the daratumumab maintenance group than the observation-alone group (median not reached [95% CI 79·9-not estimable (NE)] vs 45·8 months [41·8-49·6]; HR 0·49 [95% CI 0·40-0·59]; p<0·0001); benefit was observed with D-VTd with daratumumab maintenance versus D-VTd with observation (median not reached [74·6-NE] vs 72·1 months [52·8-NE]; 0·76 [0·58-1·00]; p=0·048) and VTd with daratumumab maintenance versus VTd with observation (median not reached [66·9-NE] vs 32·7 months [27·2-38·7]; 0·34 [0·26-0·44]; p<0·0001). INTERPRETATION: The long-term follow-up results of CASSIOPEIA show that including daratumumab in both the induction and consolidation phase and the maintenance phase led to superior progression-free survival outcomes. Our results confirm D-VTd induction and consolidation as a standard of care, and support the option of subsequent daratumumab monotherapy maintenance, for transplant-eligible patients with newly diagnosed multiple myeloma. FUNDING: Intergroupe Francophone du Myélome, Dutch-Belgian Cooperative Trial Group for Hematology Oncology, and Janssen Research & Development.

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.

Consensus guidelines and recommendations for the management and response assessment of chimeric antigen receptor T-cell therapy in clinical practice for relapsed and refractory multiple myeloma: a report from the International Myeloma Working Group Immunotherapy Committee.

Chimeric antigen receptor (CAR) T-cell therapy has shown promise in patients with late-line refractory multiple myeloma, with response rates ranging from 73 to 98%. To date, three products have been approved: Idecabtagene vicleucel (ide-cel) and ciltacabtagene autoleucel (cilta-cel), which are approved by the US Food and Drug Administration, the European Medicines Agency, Health Canada (ide-cel only), and Brazil ANVISA (cilta-cel only); and equecabtagene autoleucel (eque-cel), which was approved by the Chinese National Medical Products Administration. CAR T-cell therapy is different from previous anti-myeloma therapeutics with unique toxic effects that require distinct mitigation strategies. Thus, a panel of experts from the International Myeloma Working Group was assembled to provide guidance for clinical use of CAR T-cell therapy in myeloma. This consensus opinion is from experts in the field of haematopoietic cell transplantation, cell therapy, and multiple myeloma therapeutics.

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.

Predictors of early morbidity and mortality in newly diagnosed multiple myeloma: data from five randomized, controlled, phase III trials in 3700 patients.

Early morbidity and mortality affect patient outcomes in multiple myeloma. Thus, we dissected the incidence and causes of morbidity/mortality during induction therapy (IT) for newly diagnosed multiple myeloma (NDMM), and developed/validated a predictive risk score. We evaluated 3700 transplant-eligible NDMM patients treated in 2005-2020 with novel agent-based triplet/quadruplet IT. Primary endpoints were severe infections, death, or a combination of both. Patients were divided in a training (n = 1333) and three validation cohorts (n = 2367). During IT, 11.8%, 1.8%, and 12.5% of patients in the training cohort experienced severe infections, death, or both, respectively. Four major, baseline risk factors for severe infection/death were identified: low platelet count (<150/nL), ISS III, higher WHO performance status (>1), and age (>60 years). A risk score (1 risk factor=1 point) stratified patients in low (39.5%; 0 points), intermediate (41.9%; 1 point), and high (18.6%; ≥2 points) risk. The risk for severe infection/death increased from 7.7% vs. 11.5% vs. 23.3% in the low- vs. intermediate- vs. high-risk groups (p < 0.001). The risk score was independently validated in three trials incorporating quadruplet IT with an anti-CD38 antibody. Our analyses established a robust and easy-to-use score to identify NDMM patients at risk of severe infection/death, covering the latest quadruplet induction therapies. Trial registrations: HOVON-65/GMMG-HD4: EudraCT No. 2004-000944-26. GMMG-MM5: EudraCT No. 2010-019173-16. GMMG-HD6: NCT02495922. EMN02/HOVON-95: NCT01208766. GMMG-HD7: NCT03617731.

Teclistamab impairs humoral immunity in patients with heavily pretreated myeloma: importance of immunoglobulin supplementation.

ABSTRACT: Teclistamab and other B-cell maturation antigen (BCMA)-targeting bispecific antibodies (BsAbs) have substantial activity in patients with heavily pretreated multiple myeloma (MM) but are associated with a high rate of infections. BCMA is also expressed on normal plasma cells and mature B cells, which are essential for the generation of a humoral immune response. The aim of this study was to improve the understanding of the impact of BCMA-targeting BsAbs on humoral immunity. The impact of teclistamab on polyclonal immunoglobulins and B cell counts was evaluated in patients with MM who received once-weekly teclistamab 1.5 mg/kg subcutaneously. Vaccination responses were assessed in a subset of patients. Teclistamabinduced rapid depletion of peripheral blood B cells in patients with MM and eliminated normal plasma cells in ex vivo assays. In addition, teclistamab reduced the levels of polyclonal immunoglobulins (immunoglobulin G [IgG], IgA, IgE, and IgM), without recovery over time while receiving teclistamab therapy. Furthermore, response to vaccines against Streptococcus pneumoniae, Haemophilus influenzae type B, and severe acute respiratory syndrome coronavirus 2 was severely impaired in patients treated with teclistamab compared with vaccination responses observed in patients with newly diagnosed MM or relapsed/refractory MM. Intravenous immunoglobulin (IVIG) use was associated with a significantly lower risk of serious infections among patients treated with teclistamab (cumulative incidence of infections at 6 months: 5.3% with IVIG vs 54.8% with observation only [P < .001]). In conclusion, our data show severe defects in humoral immunity induced by teclistamab, the impact of which can be mitigated by the use of immunoglobulin supplementation. This trial was registered at www.ClinicalTrials.gov as #NCT04557098.

Monoclonal Antibodies in the Treatment of Multiple Myeloma.

The incorporation of monoclonal antibodies into backbone regimens has substantially improved the clinical outcomes of patients with newly diagnosed and relapsed/refractory multiple myeloma (MM). Although the SLAMF7-targeting antibody elotuzumab has no single- agent activity, there is clinical synergy between elotuzumab and immunomodulatory drugs in patients with relapsed/refractory disease. Daratumumab and isatuximab are CD38-targeting antibodies which have single-agent activity and a favorable safety profile, which make these agents an attractive component of combination regimens. Monoclonal antibodies may cause infusion-related reactions, but with subcutaneous administration these are less frequently observed. All therapeutic antibodies may interfere with assessment of complete response. Next-generation Fc-engineered monoclonal antibodies are in development with the potential to further improve the outcome of patients with MM.

Ixazomib, daratumumab and low-dose dexamethasone in intermediate-fit patients with newly diagnosed multiple myeloma: an open-label phase 2 trial.

Background: The outcome of non-transplant eligible newly diagnosed multiple myeloma (NDMM) patients is heterogeneous, partly depending on frailty level. The aim of this study was to prospectively investigate the efficacy and safety of Ixazomib-Daratumumab-low-dose dexamethasone (Ixa-Dara-dex) in NDMM intermediate-fit patients. Methods: In this phase II multicenter HOVON-143 study, IMWG Frailty index based intermediate-fit patients, were treated with 9 induction cycles of Ixa-Dara-dex, followed by maintenance with ID for a maximum of 2 years. The primary endpoint was overall response rate on induction treatment. Patients were included from October 2017 until May 2019. Trial Registration Number: NTR6297. Findings: Sixty-five patients were included. Induction therapy resulted in an overall response rate of 71%. Early mortality was 1.5%. At a median follow-up of 41.0 months, median progression-free survival (PFS) was 18.2 months and 3-year overall survival 83%. Discontinuation of therapy occurred in 77% of patients, 49% due to progression, 9% due to toxicity, 8% due to incompliance, 3% due to sudden death and 8% due to other reasons. Dose modifications of ixazomib were required frequently (37% and 53% of patients during induction and maintenance, respectively), mainly due to, often low grade, polyneuropathy. During maintenance 23% of patients received daratumumab alone. Global quality of life (QoL) improved significantly and was clinically relevant, which persisted during maintenance treatment. Interpretation: Ixazomib-Daratumumab-low-dose dexamethasone as first line treatment in intermediate-fit NDMM patients is safe and improves global QoL. However, efficacy was limited, partly explained by ixazomib-induced toxicity, hampering long term tolerability of this 3-drug regimen. This highlights the need for more efficacious and tolerable regimens improving the outcome in vulnerable intermediate-fit patients. Funding: Janssen Pharmaceuticals, Takeda Pharmaceutical Company Limited.

Treatment of primary plasma cell leukaemia with carfilzomib and lenalidomide-based therapy (EMN12/HOVON-129): final analysis of a non-randomised, multicentre, phase 2 study.

BACKGROUND: Primary plasma cell leukaemia is a rare and aggressive plasma cell disorder with a poor prognosis. The aim of the EMN12/HOVON-129 study was to improve the outcomes of patients with primary plasma cell leukaemia by incorporating carfilzomib and lenalidomide in induction, consolidation, and maintenance therapy. METHODS: The EMN12/HOVON-129 study is a non-randomised, phase 2, multicentre study conducted at 19 academic centres and hospitals in seven European countries (Belgium, Czech Republic, Denmark, Italy, Norway, The Netherlands, and the UK) for previously untreated patients with primary plasma cell leukaemia aged 18 years or older. Inclusion criteria were newly diagnosed primary plasma cell leukaemia (defined as >2 ×109 cells per L circulating monoclonal plasma cells or plasmacytosis >20% of the differential white cell count) and WHO performance status 0-3. Patients aged 18-65 years (younger patients) and 66 years or older (older patients) were treated in age-specific cohorts and were analysed separately. Younger patients were treated with four 28-day cycles of carfilzomib (36 mg/m2 intravenously on days 1, 2, 8, 9, 15, and 16), lenalidomide (25 mg orally on days 1-21), and dexamethasone (20 mg orally on days 1, 2, 8, 9, 15, 16, 22, and 23). Carfilzomib-lenalidomide-dexamethasone (KRd) induction was followed by double autologous haematopoietic stem-cell transplantation (HSCT), four cycles of KRd consolidation, and then maintenance with carfilzomib (27 mg/m2 intravenously on days 1, 2, 15, and 16 for the first 12 28-day cycles, and then 56 mg/m2 on days 1 and 15 in all subsequent cycles) and lenalidomide (10 mg orally on days 1-21) until progression. Patients who were eligible for allogeneic HSCT, could also receive a single autologous HSCT followed by reduced-intensity conditioning allogeneic HSCT and then carfilzomib-lenalidomide maintenance. Older patients received eight cycles of KRd induction followed by maintenance therapy with carfilzomib and lenalidomide until progression. The primary endpoint was progression-free survival. The primary analysis population was the intention-to-treat population, irrespective of the actual treatment received. Data from all participants who received any study drug were included in the safety analyses. The trial was registered at www.trialregister.nl (until June 2022) and https://trialsearch.who.int/ as NTR5350; recruitment is complete and this is the final analysis. FINDINGS: Between Oct 23, 2015, and Aug 5, 2021, 61 patients were enrolled and received KRd induction treatment (36 patients aged 18-65 years [20 (56%) were male and 16 (44%) female], and 25 aged ≥66 years [12 (48%) were male and 13 (52%) female]). With a median follow-up of 43·5 months (IQR 27·7-67·8), the median progression-free survival was 15·5 months (95% CI 9·4-38·4) for younger patients. For older patients, median follow-up was 32·0 months (IQR 24·7-34·6), and median progression-free survival was 13·8 months (95% CI 9·2-35·5). Adverse events were most frequently observed directly after treatment initiation, with infections (two of 36 (6%) younger patients and eight of 25 (32%) older patients) and respiratory events (two of 36 [6%] younger patients and four of 25 [16%] older patients) being the most common grade 3 or greater events during the first four KRd cycles. Treatment-related serious adverse events were reported in 26 (72%) of 36 younger patients and in 19 (76%) of 25 older patients, with infections being the most common. Treatment-related deaths were reported in none of the younger patients and three (12%) of the older patients (two infections and one unknown cause of death). INTERPRETATION: Carfilzomib and lenalidomide-based therapy provides improved progression-free survival compared with previously published data. However, results remain inferior in primary plasma cell leukaemia compared with multiple myeloma, highlighting the need for new studies incorporating novel immunotherapies. FUNDING: Dutch Cancer Society, Celgene (a BMS company), and AMGEN.

Specific Targeting of Multiple Myeloma by Dual Split-signaling Chimeric Antigen Receptor T cells Directed against CD38 and CD138.

PURPOSE: The success of B-cell maturation antigen (BCMA)-specific chimeric antigen receptor (CAR) T cells illustrates the potential of this novel therapy for multiple myeloma. Nonetheless, broadening CAR T-cell therapy beyond BCMA requires inventive strategies as there are only a few multiple myeloma- or plasma cell-specific target antigens. We investigated the feasibility of achieving multiple myeloma specificity by dual-split CD38/CD138 CAR targeting, whereby the stimulatory and costimulatory signals for T-cell activation are split into two separate stimulatory (sCAR) and costimulatory CARs (cCAR). EXPERIMENTAL DESIGN: Using various combinations of CD38 and CD138 sCARs and cCARs with different affinities, we generated several dual-split CAR T cells and analyzed them for multiple myeloma-specific effector functions in vitro. The best-functioning CAR T cells were tested in vivo in a murine xenograft model. RESULTS: We found optimal designs of both CD38sCAR/CD138cCAR and CD138sCAR/CD38cCAR combinations, that effectively lysed multiple myeloma cells but spared single CD38- or CD138-positive healthy hematopoietic cells. While the CD38sCAR/CD138cCAR T cells achieved multiple myeloma-specific activity solely due to the low affinity of the CD38sCARs, the multiple myeloma-specific cytotoxicity, cytokine release, and proliferation of CD138sCAR/CD38cCAR T cells were established through a true combinatorial stimulatory and costimulatory effect. The most optimal combination comprised a low-affinity CD138sCAR combined with a high-affinity CD38cCAR. These CD138sCAR/CD38cCAR T cells also showed dual-antigen specific anti-multiple myeloma effects in vivo. Importantly, they were also effective against multiple myeloma cells from daratumumab pretreated patients with decreased CD38 expression levels. CONCLUSIONS: We demonstrate the possibility to specifically target multiple myeloma cells, even after CD38 targeted therapy, with carefully-designed dual-split CARs directed against CD38 and CD138.