Targeting B-cell Maturation Antigen Research Articles

Bispecific antibody treatment of multiple myeloma: latest updates from the 2022 ASH annual meeting.

Effective novel therapies for multiple myeloma (MM) patients who are unresponsive to conventional treatments (triple-class refractory) are an urgent need. Bispecific antibodies (BsAbs) offer a promising new approach to stimulate T cells and induce tumor cell death by targeting molecules on the surface of malignant plasma cells and CD3 on the surface of T cells. Addressing the issue of improving the prognosis of triple-class refractory MM patients has become a significant clinical challenge. This is a brief report. This article summarizes the latest updates of BsAbs treatment of MM from the 2022 ASH annual meeting. BsAbs that target B-cell maturation antigen and G protein-coupled receptor family C group 5 memberD have demonstrated remarkable clinical activity and favorable safety profiles. Many potential targets for myeloma cells are currently undergoing phase I/II clinical trials, and these off-the-shelf bispecific molecules are likely to become a critical part of the MM treatment landscape. This article provides an overview of the latest advances in BsAbs immunotherapy for refractory and relapsed MM and highlights significant findings from the 2022 ASH annual meeting.

47P Phase I study to assess the safety and efficacy of P-BCMA-ALLO1: A fully allogeneic CAR-T therapy, in patients with relapsed/refractory multiple myeloma (RRMM)

P-BCMA-ALLO1 is an allogeneic Chimeric Antigen Receptor T-cell (CAR-T) targeting B-cell Maturation Antigen (BCMA) being investigated in RRMM. P-BCMA-ALLO1 is manufactured using non-viral transposon-based integration (piggyBac®DNA Delivery System) that introduces a humanized anti-BCMA VH-based CAR producing a highly enriched T stem cell memory product. The Cas-CLOVER™ Site-Specific Gene Editing System eliminates endogenous T cell receptor (TCR) expression via knockout of the TCR beta chain 1 gene to prevent graft-vs-host disease, and the beta-2 microglobulin gene to reduce MHC class I expression to eliminate host-vs-graft responses.

Innovation in BCMA CAR-T therapy: Building beyond the Model T.

Autologous chimeric antigen receptor T-cell (CAR-T) therapies targeting B-cell maturation antigen (BCMA) have revolutionized the field of multiple myeloma in the same way that the Ford Model T revolutionized the original CAR world a century ago. However, we are only beginning to understand how to improve the efficacy and usability of these cellular therapies. In this review, we explore three automotive analogies for innovation with BCMA CAR-T therapies: stronger engines, better mileage, and hassle-free delivery. Firstly, we can build stronger engines in terms of BCMA targeting: improved antigen binding, tools to modulate antigen density, and armoring to better reach the antigen itself. Secondly, we can improve "mileage" in terms of response durability through ex vivo CAR design and in vivo immune manipulation. Thirdly, we can implement hassle-free delivery through rapid manufacturing protocols and off-the-shelf products. Just as the Model T set a benchmark for car manufacturing over 100 years ago, idecabtagene vicleucel and ciltacabtagene autoleucel have now set the starting point for BCMA CAR-T therapy with their approvals. As with any emerging technology, whether automotive or cellular, the best in innovation and optimization is yet to come.

Belantamab Mafodotin in Combination with Pomalidomide and Dexamethasone Demonstrates Durable Responses in Triple Class Exposed/Refractory Multiple Myeloma

Background: Belantamab mafodotin (belamaf) is a first-in-class antibody-drug conjugate (ADC) targeting B-cell maturation antigen (BCMA). Belamaf has shown clinically meaningful activity as a single agent in relapse/refractory multiple myeloma (RRMM). The Algonquin study demonstrated that the anti-myeloma activities of belamaf are significantly increased by the immunomodulatory drug pomalidomide (POM). The Algonquin study is a two part study designed to evaluate the safety and efficacy of different doses and schedules of belamaf in combination with POM and dexamethasone (DEX) (Bela-Pd) in patients (pts) with RRMM. Here we report updated safety and efficacy data for the subgroup of RRMM pts exposed or refractory to lenalidomide (LEN), a proteasome inhibitor (PI) and an anti-CD38 agent (triple class exposed). Methods: Eligibility criteria included > 1 prior lines of treatment (LoT), LEN and PI exposure and refractoriness to the last LoT. POM was administered at 4 mg days 21/28 days, DEX 40 mg (20 mg age > 75 years) weekly in conjunction with IV belamaf administered as a SINGLE dose of 1.92 mg/kg Q4W or 2.5 mg/kg Q4W, Q8W or Q12W, or SPLIT equally (2.5 or 3.4 mg/kg) on days 1 and 8 Q4W. Responses were assessed by International Myeloma Working Group (IMWG) criteria and adverse events (AEs) were graded by CTCAE criteria except for corneal findings which were also graded by the pre-specified keratopathy and visual acuity (KVA) scale. In Part 1 up to 12 pts were enrolled in each cohort to inform the recommended part 2 dose (RP2D). In part 2, 23 patients will be enrolled to provide 35 patients (inclusive of the 12 treated at the RP2D of 2.5 mg/kg Q8W in Part 1) for overall response determination. Results: At data cut-off (April 11, 2022), 54 triple class exposed pts had been enrolled in the following dose levels and schedules: 1.92 mg/kg Q4W (n=6), 2.5 mg/kg (SINGLE and SPLIT) Q4W (n=6), 2.5 mg/kg Q8W (n=26), 2.5 mg/kg Q12W (n=12), and 3.4 mg/kg SPLIT (n=4). The median age was 67.5 years (range 36-85) and median prior LoT was 3 (range 2-5). Prior therapies (exposed/refractory) included stem cell transplant (61.1%), PI (100%/79.6%), LEN (100%/92.6%), anti-CD38 (100%/100%) and 72.2% triple class refractory. The most frequent grade 1-2 AEs reported in all cohorts were keratopathy (an ophthalmologic finding) (68.6%), decreased best-corrected visual acuity (BCVA) (60.8%), fatigue (51.0%), thrombocytopenia (35.3%), and blurred vision (33.3%). Grade 3/4 AEs reported in >20% of pts across all cohorts, were keratopathy (54.9%), neutropenia (37.3%), thrombocytopenia (27.5%), and decreased BCVA (23.5%). Three patients discontinued treatment due to AEs (one G4 decreased visual acuity, one G3 elevated ALT, and one due to myelodysplastic syndrome) and three grade 5 AEs were observed (one from myeloma progression, one from lung infection, and one from myelodysplastic syndrome). At data cut-off, 50/54 patients were evaluable for response. Across all cohorts the ORR was 86.0% (60.0% > VGPR). Responses by dosing cohort are summarized in Table 1. At a median follow-up of 5.7 months, the median PFS (n=49 at a data-cut of March 28, 2022) was 15.6 months (95% CI: 12.9, NYR; across all cohorts). Conclusions: Patients who are triple class exposed/refractory remain challenging to treat and require therapies with novel mechanisms of action. In the recent LocoMMotion study, triple class exposed MM patients who prospectively received real-life standard of care (SOC) therapies demonstrated an overall response rate (ORR) of 29.8% and median PFS of 4.6 months. Thus, the combination of Bela-Pd represents an improvement over widely available SOC treatments for this poor prognosis patient population. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Belantamab Mafodotin in Patients with Relapsed and Refractory Multiple Myeloma Who Have Received at Least One Proteasome Inhibitor, One Immunomodulatory Agent and One Anti-CD38 Monoclonal Antibody: A Retro-Prospective Italian Observational Study

Despite a significant improved outcome in Multiple Myeloma (MM) patients due to introduction of immunomodulatory drugs (IMiDs), proteasome inhibitors (PIs), and monoclonal antibodies (mAbs), occurrence of resistance to these agents results in a poor survival with the need for effective therapies in this setting. Belantamab mafodotin (belamaf) represents the first-in-class antibody-drug conjugate (ADC) targeting B-cell maturation antigen (BCMA) to be approved for treatment of relapsed/refractory MM (rrMM) patients who have previously received at least four lines of therapy after it demonstrated meaningful activity as monotherapy in the phase II DREAMM-2 study. Real-world data of belamaf use is scarce since the number of patients in the study cohorts are low. We carried out a retro-prospective study aiming to evaluate efficacy and safety of belamaf monotherapy in RRMM patients treated according to compassionate use programmes as Named Patient Program (NPP) and Expanded Access Program (EAP) in 60 Italian centers under the aegis of European Myeloma Network (EMN). The primary endpoint of this study was the rate of patients achieving a clinical benefit (at least minimal response according to IMWG criteria). Secondary endpoints were ORR (at least PR), duration of response (DoR), progression-free survival (PFS) and overall survival (OS). Eligible patients must be ≥18 years of age with a MM diagnosis according to IMWG criteria; they must have received at least 4 previous therapies and be refractory to at least one proteasome inhibitor, one immunomodulatory drug, and one anti-CD38 antibody. Moreover, patients had to have an ECOG performance status ≤ 2 and adequate organs function. Overall, 182 patients have been treated with belamaf within the compassionate use programmes, 138 in the NPP program and 44 in the EAP program. In July 2022, 23 patients are still receiving therapy with belamaf (7 are from NPP program). Notably, 2 patients have received 9 belamaf cycles, 8 patients received more than 11 cycles, 8 patients more than 15 cycles and 5 patients at least 20 cycles. Moreover, one patient was given 34 cycles and another 36 ones. This is the largest real-life study on belamaf monotherapy in rrMM. Data on efficacy and safety will be detailed at the meeting.

Rapid Response to Idecabtagene Vicleucel in a Myeloma Patient Refractory to Multiple Prior Lines of Anti-BCMA Directed Therapies

Targeting B-cell maturation antigen (BCMA) with antibody drug conjugates (ADCs), bispecific antibodies, or chimeric antigen receptor (CAR) T-cells is an established strategy in relapsed/refractory multiple myeloma (RRMM). In most European countries, the respective agents are approved after exposure to at least three lines of therapy including a proteasome inhibitor (PI), an immunomodulatory drug (IMiD), and an anti-CD38 antibody. It still needs to be clarified whether sequential treatment with different anti-BCMA directed agents is safe and effective. In some countries, payers do not cover/reimburse CAR T-cell treatment directed against BCMA if the patient was previously exposed to an anti-BCMA ADC or bispecific antibody. To the best of our knowledge, we describe the first case of rapid response to BCMA-directed CAR-T cells (idecabtagene vicleucel; Ide-cel) in a heavily pretreated patient who had already failed two prior lines of anti-BCMA directed therapies. A 54-year-old female with IgG kappa MM harboring chromosomal deletion 17p and gain of 1q21 presented to our department. Initial treatment consisted of PI/IMiD-based induction therapy, high-dose melphalan as part of tandem autologous stem cell transplantations followed by lenalidomide maintenance. Very good partial remission (VGPR) lasted 3 years, and the patient became triple-class (PI, IMiD, anti-CD38)-refractory only two years after first relapse. We enrolled the patient in a phase I/II trial of the anti-BCMA bispecific antibody teclistamab. Cytokine release syndrome (CRS) grade III complicated teclistamab treatment and the patient showed biochemical relapse and progressive osteolytic lesions after being 4 months on study. After failing two subsequent alkylator-based lines of therapy including melphalan flufenamid, the patient was treated with belantamab mafodotin and progressed after two months. Treatment was switched to isatuximab/pomalidomide/dexamethasone. The latter combination represented the 11th line of therapy for this patient. After approval of Ide-cel in Germany in 2021, leukapheresis for successive CAR T-cell production was performed. Since the patient showed a partial response after 1 month, this bridging therapy with isatuximab/pomalidomide/dexamethasone was continued until successful CAR manufacturing. Unfortunately, the patient experienced disease progression prior to lymphodepletion therapy with progressive transfusion-dependent pancytopenia and subtotal infiltration of bone marrow by malignant plasma cells. PET/CT showed no evidence of extramedullary disease. Lymphodepletion with fludarabine/cyclophosphamide according to the phase-II KarMMa protocol was initiated, and 441.5 x 10exp6 CAR T-cells were infused. The inpatient stay was complicated by grade I CRS and septicemia due to gram-negative bacteria requiring vasopressor treatment for 48 hours. Two weeks after infusion of Ide-cel, significant increases of serum uric acid and lactate dehydrogenase levels indicative of tumor lysis syndrome were detected, requiring application of rasburicase and intravenous hydration. After stabilization of serum creatinine values, serological assessment of disease activity three weeks after CAR T-cell infusion already showed decrease of serum kappa free light chains from 3328 mg/l at admission to 4 mg/l and an unprecedented depth of remission (VGPR, see Figure 1). Currently, the patient's state of remission is still improving. Updated follow-up and data on CAR T-cell expansion and persistence will be presented at the meeting. Our case illustrates rapid response to anti-BCMA CAR-T cells (Ide-cel) after failing treatment with an ADC and a bispecific antibody directed against BCMA. This demonstrates that sequential treatment can be effective even after multiple prior lines of anti-BCMA directed therapies. Patients with prior exposure to anti-BCMA agents should have access to anti-BCMA CAR T-cells. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Infectious Complications of B-Cell Maturation Antigen (BCMA)-Targeted Therapies for Relapsed/Refractory Multiple Myeloma

Background: Recently, therapeutics targeting B-cell Maturation Antigen (BCMA), including CAR T cells, bispecific antibodies (bsAbs) and antibody-drug conjugates (ADCs), have shown promise in improving outcomes in RRMM patients (pts). However, targeting BCMA can impair natural humoral immunity and increase infection risk. It remains unknown if BCMA-targeted therapies predispose pts to infection at higher frequency or with different characteristics than non-BCMA-targeted therapies in this RRMM population, or if the frequency and characteristics of infections differ amongst the various BCMA-targeted modalities. Methods: We conducted a single-center retrospective study of RRMM pts who started BCMA-targeted therapies (CAR T, bsAb, or ADC) or a selinexor-based treatment between Nov. 2015 and May 2021. We extracted data on patient demographics, MM characteristics, prior lines of therapy, neutrophil and lymphocyte counts, and response to therapy, as well as frequency, type, and severity of infections, quantitative immunoglobulins, and use of intravenous immunoglobulin (IVIG). Pts who had received serial BCMA-targeted therapies, or both a BCMA-targeted therapy and selinexor were excluded from analysis. Results: There were 134 pts included in the analysis: 112 who received a BCMA-targeted treatment (36 CAR T, 29 bsAb, and 47 ADC) and 22 who received selinexor-based treatment. Overall pt characteristics, including age, median lines of therapy, and %triple- and penta-refractory, were similar between the anti-BCMA therapy and selinexor groups, as well as amongst pts receiving the different anti-BCMA modalities. However median duration of therapy differed between groups, longest in the bsAb group and shortest for selinexor (Table 1). Of pts receiving BCMA-targeted treatment, 63 (56%) experienced at least 1 infectious complication (75% of CAR T, 48% of bsAb, and 47% of ADC pts), compared to 6 pts (27%) in the selinexor group. These 69 pts had a total of 146 infections (mean of 2.0, 2.9, 2.1, and 1.0 infections per infected pt in the CAR T, bsAb, ADC, and selinexor groups, respectively) (Table 2). Of the infections in the BCMA-treated pts, 70% were considered low-severity (no treatment or oral treatment alone) and 30% were high-severity (hospitalization, life-threatening, or fatal), with similar frequency of high-severity infections amongst pts getting CAR T, bsAb or ADC. Four of 6 infections (67%) in the selinexor group were high-severity. Most (66%) of the low-severity were upper respiratory tract infections, while most high-severity were lower respiratory tract infections (54%) or bacteremia (22%). Low-severity infections were most commonly viral, while high-severity infections were more likely bacterial. Fungal infections were rare (n=2, both in CAR-T patients). Median time to onset of high-severity infections was 59 days in the CAR T cohort compared to 278 days and 124 days in the bsAb and ADC groups, respectively, and 205 days in the selinexor group. Only 12 of the 146 infections (8%) occurred while pts were neutropenic. Median absolute lymphocyte counts (ALC) were low in all groups pre-treatment; amongst pts still on therapy at 3 months, median ALC had increased in all 3 BCMA-treated groups (Table 1). Regarding hypogammaglobulinemia we focused on pts with non-IgG myeloma to limit confounding effects of the monoclonal IgG protein. Amongst non-IgG pts receiving BCMA-targeted treatments (n=50), 70% had IgG<400 pre-treatment, which increased to 87% by 3 months. For non-IgG selinexor pts (n=9), these numbers were 67% and 71%, respectively. At least 1 dose of IVIG was given in 31% of BCMA-treated pts (22% of CAR T, 59% of bsAb, and 21% of ADC). Conclusions: RRMM pts treated with BCMA-targeted therapies are at high risk of developing an infectious complication, regardless of treatment modality, with many patients having multiple infections, and up to 30% developing high-severity infections. Infection frequency in this study appeared higher for anti-BCMA-treated pts than for selinexor-treated patients, though this finding is confounded by the small numbers and shorter duration of therapy in the selinexor group. Further analyses of the impact of response, ALC, immunoglobulin levels, and IVIG use on infection risk and severity are ongoing. These data demonstrate a need for optimizing strategies to prevent and treat infectious complications in RRMM pts receiving BCMA-targeted therapies. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Hdp-101, an Anti-BCMA Antibody-Drug Conjugate with a Novel Payload Amanitin in Patients with Relapsed Multiple Myeloma, Initial Findings of the First in Human Study

Several antibody-drug conjugates (ADCs) are currently being evaluated in clinical trials in a variety of malignancies. Vast majority of these ADCs are based on a few toxic compounds, largely limited to microtubule- or DNA-targeting toxins targets proliferating cells and have limited efficacy in diseases with a low proliferative fraction such as multiple myeloma. Thus, new compounds with alternative mode of actions and the ability to actively induce cell death in non-proliferating tumor cells could enhance the therapeutic potential of ADCs. We are currently developing amanitin based ADCs. Amanitin specifically inhibits RNA polymerase II thereby inhibiting the cellular transcription process at very low concentrations irrespective of the proliferation status of the target cell. Subsequently tumor cells enter apoptosis and are eliminated. HDP-101 is a new ADC targeting BCMA (B cell maturation antigen) carrying a synthetic version of amanitin as a payload. In vitro cytotoxic potency of HDP-101 was demonstrated on BCMA-positive myeloma cell lines, as well as on non-proliferating primary CD138+ cells isolated from patients with refractory myeloma. Furthermore, the cytotoxic effects of HDP-101 were seen even in non-proliferating myeloma cells with low BCMA density. Toxicity was observed neither in non-BCMA expressing control cells nor in myeloma cells exposed to an amanitin-loaded non-target control antibody. In murine xenograft models of human myeloma, HDP-101 caused dose-dependent tumor regression including complete remissions after a single dose in subcutaneous and as well as in disseminated models. Safety profiling in Cynomolgus monkeys revealed a good therapeutic index after repeated dosing. Our non-clinical studies concluded that this amanitin-based ADC is a novel promising approach in the therapy of multiple myeloma to overcome drug resistance and improve patient outcome. HDP-101-01 is a first-in-human, open label, non-randomized, multicenter, phase 1/2a trial with HDP-101 in patients with multiple myeloma whose disease has progressed. The aim of the Phase 1 dose escalation part is to determine the Maximum Tolerated Dose and/or establish the Recommended phase 2 Dose. The primary objective of the phase 2 dose expansion phase is to assess the preliminary anti-tumor activity of HDP-101. An adaptive Bayesian logistic regression model with overdose control principle is used to guide the dose escalation steps. An Interim Analysis is planned after each cohort is completed. The design of the study ensures a safe and adaptive dose escalation to reach a potential clinical benefit in a patient who have limited or no therapeutic options. The study started enrollment in February 2022. As of 12th of July 2022 four (1 female and 3 male) patients were dosed in 2 consecutive dose cohorts. The median age of the patients was 63.5 years, ranging between 51 and 80. All 4 patients were heavily pre-treated and multidrug-resistant. The median previous lines of treatment were 11 (5 to 16). Three of 4 patients were evaluable for dose limiting toxicities (DLT). The initial 2 cohorts were well tolerated, without any reports on DLTs. No reports of keratopathy or visual acuity loss were observed. Free payload was not detected in any of the available pharmacokinetic samples. In line with our expectation objective responses also were not reported in these initial cohorts. The initial dose cohorts showed good tolerability in late stage relapsed and/or refractory multiple myeloma patients. The study continues to enroll patient to higher dose cohorts. An updated dataset will be presented at the ASH2022 meeting.

Intensity of Cyclophosphamide-Based Bridging Regimens before BCMA-Directed CAR-T Therapy

INTRODUCTION: Patients receiving autologous chimeric antigen receptor T-cell (CAR-T) therapies targeting B-cell maturation antigen (BCMA) for multiple myeloma (MM) may require bridging therapy before CAR-T infusion to maintain some level of disease control. Many bridging regimens used in MM include alkylating agents such as cyclophosphamide (Cy), for example V(T)D-PACE, DCEP, or modified hyperCVAD. However, there is no consensus around the optimal choice or chemotherapy dose intensity of such bridging regimens. METHODS: We performed a single-center analysis of all instances of bridging therapy before planned autologous BCMA CAR-T during a 5-year period ending March 2022. We classified bridging regimens into three cohorts: (1) IV dose-dense Cy (IV_ddCy) with inpatient IV Cy every 12-24 hours and mesna support per modified hyperCVAD protocol (Narayan 2020); (2) Weekly_Cy, with weekly oral/IV Cy; and (3) No_Cy, where Cy was not used in bridging. Demographic and disease-related characteristics at time of T-cell collection, as well as post-CAR-T outcomes for patients who received CAR-T, were compared using Fisher's and Kruskal-Wallis testing. Progression-free survival (PFS) and overall survival (OS) were estimated using the Kaplan-Meier method. RESULTS: There were 69 discrete instances of bridging therapy among 63 unique patients, 89% of whom were previously Cy-exposed. Of these 69 instances, 38% involved IV_ddCy (n=26), 33% involved Weekly_Cy (n=23), and 29% involved No_Cy (n=20). Dexamethasone was used in most instances (88%, n=61) while 12% of instances incorporated radiation (n=8). Age, number of prior lines, triple-class refractory status, presence of high-risk cytogenetics, serum levels of paraprotein or involved light chains, bone marrow plasma cell burden, presence of renal dysfunction, rates of ≥PR to bridging, and rates of PD to bridging were similar between cohorts. However, extramedullary disease (EMD) was borderline more common with IV_ddCy (26%, n=6) than with Weekly_Cy (5%, n=1) (p=0.06). IV_ddCy bridging was associated with a higher total Cy exposure than Weekly_Cy: median 2100 vs 615 mg/m2 (p<0.01). All 10 instances of bridging without subsequent CAR-T were due to manufacturing failures. Among 59 instances of bridging followed by CAR-T, there were no significant differences in vein-to-vein intervals: 45 days with IV_ddCy, 39 days with Weekly_Cy, and 46 days with No_Cy. There were no differences in rates of CRS or ICANS. However, platelet recovery took longer with IV_ddCy than Weekly_Cy (median 64.0 vs 40 days, p=0.02). Median progression-free survival (PFS) was 5.0 months (95% confidence interval [CI] 3.3-not reached [NR]) with IV_ddCy versus 12.5 months (95% CI 9.4-NR) with Weekly_Cy (Figure 1A, p = 0.19). Median overall survival (OS) was 15.3 months (95% CI 9.2-NR) with IV_ddCy versus 29.5 months (95% CI 28.6-NR) with Weekly_Cy (Figure 1B, p = 0.01). DISCUSSION: In our retrospective analysis, patients bridged with IV_ddCy versus Weekly_Cy had comparable measures of MM burden. IV_ddCy bridging did not significantly prolong vein-to-vein intervals but was associated with delayed platelet recovery, perhaps related to a total median Cy exposure over 3 times that of Weekly_Cy. Importantly, IV_ddCy was associated with worsened OS despite comparable values for most markers of disease aggressiveness (apart from EMD). Study limitations include small sample size as well as confounding from unmeasured markers of MM aggressiveness among patients who were deemed to have required IV_ddCy bridging. However, our analysis suggests that intensive inpatient chemotherapy-based bridging regimens may not offer advantages over weekly Cy-containing regimens for most patients with MM who require pre-CAR-T bridging therapy. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Belantamab Mafodotin in Patients with Relapsed/Refractory Multiple Myeloma, a Real-World Single Center Experience

Introduction Belantamab mafodotin is an antibody drug conjugate targeting B-cell maturation antigen (BCMA) with single agent activity around 32% in the DREAMM2 phase II trial (Lonial et al, Cancer 2021). Side effects, including keratopathy and reduced best corrected visual acuity (BCVA), often necessitate dose reduction and dose delays which may limit efficacy. The aim of this study was to assess response rates, dose modifications, and frequency of ocular adverse events in patients treated with belantamab mafodotin in a real-world setting and in relation to prior treatment with BCMA targeted therapies. Methods All patients treated with at least one dose of commercial belantamab mafodotin at Memorial Sloan Kettering Cancer Center between October 1, 2020 and July 11, 2022 were included in the study. Descriptive statistics were used to assess patient characteristics, response rates, and rate of adverse events. Kaplan Meier curves were used to assess progression free survival (PFS) and overall survival (OS). Results Eighty-two relapsed/refractory multiple myeloma patients were included; 40 (49%) were women median age was 68 years, and 50 patients (61%) had high risk cytogenetics. Twelve patients were treated on the Expanded Access Program with belantamab mafodotin prior to receiving commercial drug. Patients had a median of 6 (range 2-14) prior lines of therapy, all had received an immunomodulatory agent, a proteasome inhibitor, and an anti-CD38 antibody. Sixteen patients (20%) had received one or more BCMA-targeted agents including a bi-specific antibody (N=5), chimeric antigen receptor (CAR) T cell (N=12), and trial therapy with belantamab mafodotin (N=1). Patients received a median of 4 cycles (range 1-31) of belantamab mafodotin. The majority, 96% (N=79), as single agent, while 3 patients were received belantamab mafodotin in combination with other anti-myeloma agents. The overall response rate (ORR) in all patients was 45%; 37/82 patients. Of these, 10 achieved a partial response (PR); 14 patients achieved a very good partial response (VGPR), and 13 patients achieved a complete response (CR) (Table). The median duration of response for patients in the ORR cohort was 11 months. Eighteen patients had stable disease (SD) and 27 patients had progressive disease (PD). The median PFS was 6 months and median OS was not reached. At the end of follow up, 19 patients continued belantamab mafodotin therapy and 28 patients had died. In a separate analysis of patients not included in the Expanded Access Program, the ORR was 43%; 8 had a PR, 13 had a VGPR, and 8 patients had a CR. Of the 16 patients who had prior exposure to BCMA targeted therapy, 5 patients had a PR or better (3 VGPR, 2 CR), 2 patients were in a VGPR/CR at start and continued to respond, 3 patients had SD while 6 patients had PD. The median PFS was similar in patients that were BCMA exposed and those that were BCMA naïve (Figure). Fifty-six patients (68%) had any grade of ocular toxicity per the Keratopathy and Visual Acuity (KVA) scale; 26 patients had grade 1, 15 grade 2, 12 grade 3, and 2 patients had grade 4 keratopathy, respectively. Twenty-six patients had presence of corneal microcysts (information missing in 11 patients). Forty-five patients experienced a decline in BCVA; 22 patients had grade 1, 13 had grade 2, 3 had grade 3, and 1 patient had grade 4 decline in BCVA, respectively (grade missing in 4 patients). The dose of belantamab mafodotin was reduced from 2.5 mg/kg to 1.92 mg/kg in 36 patients while 29 patients had dose delays, the majority due to ocular adverse events but also due to baseline cytopenia, infection, and patient preference. Most patients who had dose modifications due to ocular events were able to continue therapy on a lower dose with maintained response. Nine patients discontinued treatment due to keratopathy, 3 of whom had ongoing grade 1 keratopathy at the end of follow up. Conclusion In this heavily pre-treated multiple myeloma patient population, the ORR was 43-45% which is similar or better than the DREAMM2 phase II trial. The rate of ocular toxicity (68% keratopathy) was comparable to previous reports. Importantly, 5 of 16 patients with exposure to prior BCMA exposure achieved a PR or better while 5 had SD. The PFS was similar in BCMA exposed and BCMA naïve patients. These are encouraging outcomes for belantamab mafodotin in the real-world setting with responses and toxicities comparable to those reported in clinical trials. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Effectiveness and Safety of Belantamab Mafodotin in Patients with Relapsed or Refractory Multiple Myeloma in Real-Life Setting: The ALFA Study

Introduction: Although the therapeutic landscape for multiple myeloma (MM) has expanded, MM is an incurable disease and treatment of patients (pts) with relapsed or refractory multiple myeloma (RRMM) remains challenging. Pts triple refractory to immunomodulators (IMIDs), proteasome inhibitors (PIs), and anti-CD38 antibodies have few therapeutic alternatives and poor prognosis. Belantamab mafodotin (blmf) is a first-in-class antibody-drug conjugate targeting B-cell maturation antigen (BCMA) and showed promising results in the DREAMM-2 trial. The aim of the ALFA study is to describe blmf effectiveness and safety in pts with RRMM in a real-life setting. Methods: ALFA is a non-interventional, retrospective study of pts with RRMM initiating blmf in 46 centers in France during early access programs from April 27, 2020, to June 30, 2021. Pts characteristics, overall response rate (ORR, ≥partial response [PR]), clinical benefit rate (CBR, ≥minimal response [MR]), ≥very good PR (VGPR) rate, progression-free survival (PFS), overall survival (OS), and safety were assessed. Subgroup analyses for PFS and OS were performed according to best response, CBR, cytogenetic risk, renal failure, age at blmf initiation, previous penta-exposition (at least 2 PIs, 2 IMIDs, and 1 anti-CD38 exposition), and number of prior lines of treatment. Results: Between April 2020 and June 2021 (median duration of follow-up 7.8 months [mo]), 184 pts initiated blmf. Median time from MM diagnosis to initiation of blmf was 6 years, and 107 pts (58%) had received ≥5 prior lines of therapy. At initiation, 53% were male, median age was 70 years with 30% of pts aged of 75 years or older; 49% had renal failure; 79% were penta-exposed; and 8% had extramedullary disease. Among pts with available data (n=156), 36.5% had an ECOG PS ≥2. Cytogenetic profiles at initial diagnosis were available for 87 pts (47%), among whom 27 (33%) had high cytogenetic risk defined as pts presenting either t(4;14) or del(17p) or t(14;16); 40% had ophthalmological history (cataract in 53%). Blmf was delivered by intravenous infusion in 21-days cycles according to SmPC. Median dose at initiation was 2.5 mg/kg (min max 1.6-3.0). The median number of blmf cycles received was 3 (Q1-Q3 2-7). The ORR was 35% (≥VGPR 21%, PR 14%) and 59 pts (39%) achieved clinical benefit; 25% had stable disease (SD) and 37% had progressive disease (PD). The median PFS (mPFS) for the whole population was 2.7 mo (95 CI% 1.9-3.3), and median OS (mOS) was 9.5 mo (95 CI% 7.2-11.9). For both OS and PFS, no differences were found in subgroups according to cytogenetic risk, renal failure, age at blmf initiation, penta-exposition, and number of prior lines. According to best response, mPFS was 20.6 mo (95 CI% 13.1 to not reached) in pts with ≥VGPR, 6.6 mo (95 CI% 5.1-7.7) in pts with PR or MR and 2.8 mo (95 CI% 2.1-3.7) in pts with SD; P<0.01 (Figure 1). mOS was not reached in pts with ≥VGPR (1-year survival rate 96.7% [95 CI% 90.2-100.0]), 17.5 mo (95 CI% 9.8 to not reached) in pts with PR or MR, 9.5 mo (95 CI% 5.4-12.2) in pts with SD, and 3.3 mo (95 CI% 2.5-5.8) in pts with PD; P<0.01 (Figure 2). In pts with a clinical benefit, mPFS was 9.7 mo (95 CI% 7.5-14.9) and mOS was not reached. Safety findings were consistent with the known profile of blmf. Adverse events (AEs) were reported in 159 pts (86.4%). Most frequent reported AEs were ocular AEs in 56.0% of pts (n=103), among whom 70 pts had keratitis/keratopathy, and thrombocytopenia in 13.0% of pts. Infusion reaction was reported in 2.7% of pts. Permanent discontinuation due to AEs occurred in 12.5% of pts. Ocular AEs led to dose modification, temporary interruption, and permanent discontinuation in 19.6%, 11.4%, and 12.0% of pts, respectively. Conclusions: The ALFA study confirms the results of belantamab mafodotin as reported in the DREAMM-2 trial. In the overall population, the ORR was 35% (21% with ≥VGPR), CBR was 39%, mPFS was 2.7 mo, and mOS was 9.5 mo. In patients with a clinical benefit, mPFS was 9.7 mo and mOS was not reached. No new safety concerns were identified. These data presented from the largest real-life study conducted to our knowledge confirm previous results. Funding: GSK (214820) Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Interim Phase I Clinical Data of FT576 As Monotherapy and in Combination with Daratumumab in Subjects with Relapsed/Refractory Multiple Myeloma

Introduction: Despite the recent FDA approval of autologous chimeric antigen receptor (CAR) T-cell therapies targeting B-cell maturation antigen (BCMA), multiple myeloma (MM) remains incurable and relapsed/refractory (R/R) disease remains an area of high unmet medical need. Additionally, patient access to autologous CAR T-cell therapies is currently limited due to manufacturing constraints, the need for bridging therapy, and potentially life-threatening toxicities including cytokine release syndrome and neurologic toxicities (Munshi et al. 2021). Off-the-shelf natural killer (NK) cell therapies may offer an improved therapeutic profile and broader patient access than autologous CAR T-cell therapies. FT576 is a first-of-kind, multiplexed-engineered BCMA CAR NK cell therapy generated from a clonal master engineered induced pluripotent stem cell line, which can be used as a renewable source for the mass production of off-the-shelf NK cells of uniform composition. FT576 is engineered with 4 modalities to combine multifaceted innate immunity with multi-antigen-targeting capability: (1) high-affinity 158V, non-cleavable CD16 (hnCD16) Fc receptor for augmented antibody-dependent cellular cytotoxicity; (2) IL-15/IL-15 receptor fusion that promotes NK cell persistence; (3) CD38 knockout to mitigate NK cell fratricide by CD38-directed monoclonal antibodies (mAbs) and that provides improved metabolic fitness and resistance to oxidative stress within the tumor microenvironment; and (4) a BCMA-directed CAR to target plasma cells. These modalities are designed to enhance the potency and persistence of FT576 and to enable multi-antigen targeting when combined with tumor-targeting mAbs. In preclinical studies, FT576 combined with the anti-CD38 mAb daratumumab demonstrated highly effective tumor control compared to either treatment alone or to primary CAR T cells in a disseminated MM xenograft model (Goodridge et al. 2021), suggestive that limitations in MM treatment confounded by clonal heterogeneity and antigen loss can be overcome with a dual antigen-targeting approach. Methods: This is a Phase I trial of FT576 in patients with R/R MM. The primary objectives are to assess safety and tolerability and to determine the recommended Phase II dose of FT576, given as single or multiple doses, as monotherapy and in combination with daratumumab in R/R MM. Key secondary objectives include anti-tumor activity and pharmacokinetics. The dose-escalation stage of the trial has the following 4 arms: single-dose FT576 monotherapy on Day 1 (Regimen A); multi-dose FT576 monotherapy on Days 1 and 15 (Regimen A1); single-dose FT576 + daratumumab on Day 1 (Regimen B); and multi-dose FT576 + daratumumab on Days 1 and 15 (Regimen B1). Dose levels of FT576 starting from 100 million cells/dose are being evaluated using a modified toxicity probability interval dose-escalation design. Daratumumab is administered per approved dose and schedule. Outpatient conditioning chemotherapy consists of 3 consecutive days of fludarabine and cyclophosphamide administered prior to the first dose of FT576. Results: As of a data cutoff date of 18 Jul 2022, 9 patients with R/R MM were treated and evaluable for safety and efficacy, in the first 2 dose levels of Regimen A (n = 6) and in the first dose level of Regimen B (n = 3). No dose-limiting toxicities, and no events of any grade of cytokine release syndrome (CRS), immune effector cell-associated neurotoxicity syndrome, or graft-versus-host disease (GvHD), were observed. Conclusions: Administration of a single dose of FT576 at 100 or 300 million cells/dose alone or in combination with daratumumab is safe and well tolerated thus far without CRS, neurotoxicity, or GvHD. Interim clinical data, including safety and tolerability and initial anti-tumor activity, from the ongoing Phase I dose-escalation study of FT576 will be presented at the conference.

T Cells Expressing a Fully-Human Anti-BCMA Chimeric Antigen Receptor with a Heavy-Chain-Only Antigen-Recognition Domain Exhibit Rapid and Durable Activity Against Multiple Myeloma

Chimeric antigen receptor (CAR)-expressing T cells targeting B-cell maturation antigen (BCMA) are effective multiple myeloma therapy, but improvement in durability of responses is needed. We incorporated a fully-human heavy-chain-only anti-BCMA binding domain (FHVH33) into a CAR. Since it is only a heavy chain domain with no linker or artificial junctions, FHVH33 should be less immunogenic than a scFv. The CAR containing FHVH33 is called FHVH33-CD8BBZ. FHVH33-CD8BBZ contains CD8α hinge and transmembrane domains, a 4-1BB domain, and a CD3ζ domain; it was encoded by a γ-retroviral vector (Lam et al. Nature Communications 2020). T cells expressing FHVH33-CD8BBZ (FHVH-T) were produced from unsorted blood mononuclear cells in 7 days. Twenty-five patients received 300 mg/m2 of cyclophosphamide and 30 mg/m2 of fludarabine on days -5 to -3 followed by infusion of FHVH-T on day 0. Five dose levels were assessed, and 6x106 CAR+ T cells/kg was selected for an expansion cohort based on efficacy and manufacturing factors (Table). Patients had received a median of 6 lines of therapy (range 3 to 10) prior to enrollment. Twenty-three of 25 patients (92%) obtained partial response (PR) or better. Eighteen patients (72%) attained best responses of stringent complete response (sCR) or very good partial response (VGPR). Median progression-free survival (PFS) of all treated patients is 65 weeks to date; eleven patients have ongoing responses. One striking feature of the anti-myeloma activity of FHVH-T was the rapidity of myeloma elimination. Some myeloma markers including serum free light chains, urine monoclonal light chains, and bone marrow plasma cells decrease rapidly after any type of effective therapy while intact immunoglobulin monoclonal proteins decrease slowly due to long serum half-lives, which are 20-25 days for most types of IgG. Following rapidly changing myeloma markers such as free light chains shows the actual tempo of myeloma elimination without the confounding factor of long serum half-lives of intact immunoglobulins. Among the 12 patients with rapidly changing main myeloma markers, most anti-myeloma activity occurred within the first month after FHVH-T infusion since myeloma markers underwent a 99-100% reduction in all 12 patients by 1 month after FHVH-T infusion. In 10/12 patients with rapidly changing main myeloma markers, a 99-100% decrease had occurred by 14 days after FHVH-T infusion. We assessed FHVH-33 T early after infusion during the time of most anti-myeloma activity. Blood CAR+ cell levels were assessed by quantitative PCR (qPCR). The median peak blood CAR+ cell number was 121 (range 3 to 3414) cells/μL. Peak CAR+ cell levels occurred a median of 12 (range 7 to 15) days after FHVH-T infusion. One month after infusion, the median blood CAR+ cell number was 11 (range 0 to 305) cells/μL. Median blood CAR+ cell levels one month after infusion were 20 cells/μL in patients with a PFS of 12 months or more versus 4 cells/μL in patients with PFS less than 12 months (P=0.0273). The CD4/CD8 ratio of CAR+ T cells decreased from the time of infusion until the time of peak blood CAR+ cells (P=0.0004). From the time of infusion until the time of peak blood CAR+ cells, there was an increase the percentage of T cells with an effector memory phenotype (C-C-chemokine receptor-7 (CCR7)-negative and CD45RA-negative), (P<0.001). Expression of CCR7 on infusion CD4+ FHVH-T correlated with peak CAR+ cell level (P=0.0018). Frequency of infusion CD4+ FHVH-T with a central memory phenotype (CCR7+, CD45RA-negative) correlated with peak and 1-month post-infusion CAR+ cell levels. Peak interferon (IFN)γ and interleukin (IL)-6 levels were associated with Grade 3 or 4 CRS (P=0.0034). Peak serum levels of IFNγ, IL2, IL6, IL8, IL10, and IL15 were higher (P<0.003 for all) in patients with neurologic toxicity. Single-cell RNA sequencing revealed extensive changes in FHVH-T gene expression between infusion and the time of peak blood CAR+ cell levels. Surprisingly, humoral immune responses against the fully-human CAR expressed by FHVH-T were detected in 4/12 evaluated patients after one FHVH-T infusion. In one patient who received 2 FHVH-T treatments, a humoral anti-CAR response was associated with lack of efficacy and absence of blood FHVH-T. FHVH-T therapy led to durable responses with most anti-myeloma activity occurring within 14 days after FHVH-T infusion. Blood levels of FHVH-T correlated with CD4+CCR7+ infusion cells. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Bispecific antibodies in multiple myeloma treatment: A journey in progress.

The incorporation of novel agents and monoclonal antibody-based therapies into the treatment of multiple myeloma (MM) has significantly improved long-term patient survival. However, the disease is still largely incurable, with high-risk patients suffering shorter survival times, partly due to weakened immune systems. Bispecific molecules, including bispecific antibodies (BisAbs) and bispecific T-cell engagers (BiTEs), encourage immune cells to lyse MM cells by simultaneously binding antigens on MM cells and immune effector cells, bringing those cells into close proximity. BisAbs that target B-cell maturation antigen (BCMA) and GPRC5D have shown impressive clinical activity, and the results of early-phase clinical trials targeting FcRH5 in patients with relapsed/refractory MM (RRMM) are also promising. Furthermore, the safety profile of these agents is favorable, including mainly low-grade cytokine release syndrome (CRS). These off-the-shelf bispecific molecules will likely become an essential part of the MM treatment paradigm. Here, we summarize and highlight various bispecific immunotherapies under development in MM treatment, as well as the utility of combining them with current standard-of-care treatments and new strategies. With the advancement of novel combination treatment approaches, these bispecific molecules may lead the way to a cure for MM.

Ciltacabtagene autoleucel in patients with relapsed/refractory multiple myeloma: CARTITUDE-1 (phase 2) Japanese cohort.

Chimeric antigen receptor (CAR) T cells targeting B-cell maturation antigen have shown positive responses in patients with multiple myeloma (MM). The phase 2 portion of the CARTITUDE-1 study of ciltacabtagene autoleucel (cilta-cel) included a cohort of Japanese patients with relapsed/refractory MM. Following a conditioning regimen of cyclophosphamide (300 mg/m2 ) and fludarabine (30 mg/m2 ), patients received a single cilta-cel infusion at a target dose of 0.75 × 106 (range, 0.5-1.0 × 106 CAR-positive viable T cells/kg). The primary endpoint was overall response rate (ORR; defined as partial response or better) by International Myeloma Working Group criteria. A key secondary endpoint was the rate of very good partial response (VGPR) or better (defined as VGPR, complete response, stringent complete response). This first analysis was performed at 6months after the last patient received cilta-cel. Thirteen patients underwent apheresis, nine of whom received cilta-cel infusion. Eight patients who received cilta-cel at the target dose responded, yielding an ORR of 100%. Seven of eight (87.5%) patients achieved a VGPR or better. One additional patient who received a below-target dose of cilta-cel also achieved a best response of VGPR. MRD negativity (10-5 threshold) was achieved in all six evaluable patients. Eight of nine (88.9%) patients who received cilta-cel infusion experienced a grade 3 or 4 adverse event, and eight (88.9%) patients experienced cytokine release syndrome (all grade 1 or 2). No CAR-T cell neurotoxicity was reported. A positive benefit/risk profile for cilta-cel was established for heavily pretreated Japanese patients with relapsed or refractory MM.

620O CART-ddBCMA for multiple myeloma: Interim results from phase I study

Chimeric Antigen Receptor (CAR) T cell therapies targeting B-cell maturation antigen (BCMA) have demonstrated benefit in patients (pts) with relapsed/refractory Multiple Myeloma (RRMM). CART-ddBCMA is an autologous anti-BCMA CAR T cell therapy that utilizes a novel, synthetic binding domain, called a D-Domain, instead of a typical scFv binder. The objective of this first-in-human trial is to assess the safety & efficacy of CART-ddBCMA.

Abstract 6251: Evaluation of a dual-targeting BCMA-CS1 HLE BiTE® molecule for multiple myeloma

Abstract Multiple myeloma (MM) is a cancer of the antibody-producing plasma cells (PC). MM is invariably fatal due to frequent disease relapse and/or treatment refractoriness, and therapies that provide deeper and more durable responses are needed. BiTE® (Bispecific T Cell Engager) molecules are immunotherapy agents that redirect a patient’s T cells to lyse tumor cells by simultaneously engaging a tumor associated antigen (TAA) on cancer cells and CD3ε on T cells. Clinical activity has been observed in MM using BiTE® molecules and other T cell engagers that target B-cell maturation antigen (BCMA). BCMA is an attractive MM TAA due to its broad prevalence and restricted normal tissue profile, mainly PCs and plasmablasts. However, heterogenous expression in MM cancer cells, potential antigen loss, and the presence of high levels of soluble BCMA in MM patient sera present challenges that may prevent BCMA-only-targeted therapies from achieving their full potential. To address these issues, we generated a BiTE® molecule capable of engaging BCMA and a second MM TAA, CS1 (also known as SLAMF7). This BiTE® molecule also contains an Fc-based domain to provide half-life extension (HLE). Here, we evaluated the in vitro and in vivo properties of this BCMA-CS1 HLE BiTE® molecule. The BCMA-CS1 HLE BiTE® molecule had nanomolar binding affinity for human BCMA, CS1, and CD3ε and the non-human primate (NHP) orthologues. In vitro, we observed picomolar activity against human MM cell lines with a range of BCMA and CS1 expression in a T cell dependent cellular cytotoxicity (TDCC) assay using human T cells or NHP peripheral blood mononuclear cells. The BCMA-CS1 HLE BiTE® molecule retained TDCC activity in the presence of soluble BCMA up to 2500 ng/mL as well as against human MM cells engineered to express only BCMA or CS1. In vivo, this BiTE® molecule inhibited tumor growth in a MM xenograft model. We also evaluated the BCMA-CS1 HLE BiTE® molecule in NHP over 15 days (IV dosing; intra-animal dose escalation from 60→240 μg/kg or 180→540 μg/kg on days 1 and 8). We observed hallmarks of BiTE® molecule activity in all groups, including transient decreases in circulating lymphocytes and moderate increases in cytokines like MCP-1. We measured the PC-specific transcripts BCMA and J-chain in NHP bone marrow and blood as surrogates for PC levels using ddPCR. These transcripts were reduced in both treatment groups (≥90%) with the strongest effects occurring in the 180→540 μg/kg group. Lastly, we showed that CS1 is highly and broadly expressed in MM patient samples and is restricted to a few normal hematopoietic cell types including PCs, NK cells, T cells, and some monocytes. These data suggest that the BCMA-CS1 HLE BiTE® molecule has potent in vitro and in vivo activity and may provide therapeutic benefit for MM patients by expanding the population of MM cancer cells that can be eliminated by a BiTE® molecule while overcoming common mechanisms that can impair BCMA-only-targeted MM therapies. Citation Format: Elizabeth T. Andrews, Stephanie C. Casey, Mohammad Farhad Amani, Grit Lorenczewski, Mozhgan Farshbaf, Lisa Winkel, Matthias Klinger, John M. Harrold, Famke Aeffner, Ana Goyos, Matthias Friedrich, Tara Arvedson, Matthew G. Chun. Evaluation of a dual-targeting BCMA-CS1 HLE BiTE® molecule for multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6251.

Abstract 2814: Anti-CAIX Immune Restoring (IR) CAR-T cells display superior antitumor activity and reverse immunosuppressive TME in a humanized ccRCC orthotopic mouse model

Abstract Chimeric Antigen Receptor (CAR) T cell therapy is a new type of “living drug” that has proven to be a powerful, clinically translatable immunotherapy for hematologic malignancies. To date, there are five CAR-T products approved by FDA, four CD19 targeted CAR-T cells, and one targeting B-cell maturation antigen (BCMA). However, this success has not yet been transferred to solid tumors. A major challenge is the immunosuppressive tumor microenvironment (TME). Development of immunotherapies has traditionally been hampered by discrepancies observed between in vitro and in vivo studies and actual clinical trial outcomes. The lack of clinically relevant mouse models for human immunotherapy testing is often seen as the primary cause. Existing clear cell renal cell carcinoma (ccRCC) in vivo models poorly recapitulate the tumor microenvironment (TME). Here we report a ccRCC orthotopic humanized NSG-SGM3 mouse model (ccRCC-hNSG-SGM3) with reconstituted human lymphocytes and bearing human ccRCC skrc-59 cells under the kidney capsule. Human leukocyte antigen (HLA) matched CD34+ human stem cells were used for the humanization to reduce T cell alloreactivity against skrc-59 human ccRCC cells. Tumors were harvested, sorted for CD45+ tumor infiltrating leukocytes (TILs) and single cell RNA sequencing (scRNAseq) was performed to profile the TME in ccRCC-hNSG-SGM3. By comparing to patient data from prospective clinical trials of the anti-PD-1 monoclonal antibody (mAb) nivolumab in advanced ccRCC, the results demonstrated that CD45+ TILs from ccRCC-hNSG-SGM3 reconstitute most CD45+ cell types, including dendritic cells, exhausted CD8 T cells, and regulatory T cells (Tregs), that are observed in advanced ccRCC patient TME. Furthermore, we generated HLA matched Immune Restoring (IR) CAR-T cells which can secrete anti-PD-L1 monoclonal antibody (mAb) locally to restore active antitumor immunity, and we assessed the efficacy and safety of IR CAR-T cells in this model. Anti-CAIX CAR-T cells armored with anti-PD-L1 mAb showed superior efficacy in tumor regression and significantly decreased TIL exhaustion compared to irrelevant CAR or irrelevant payload in this model. In addition, in situ hybridization (ISH) results showed CAR-T cells infiltration in tumor but no CAR-T cells were observed in normal tissues. In summary, the ccRCC-hNSG-SGM3 system is able to model the advanced ccRCC TME and provides a powerful tool for ccRCC TME study and immunotherapy assessment. IR CAR-T cells exhibited superior tumor regression and reversed immunosuppressive TME in humanized mice. Citation Format: Yufei Wang, Alicia Buck, Marion Grimaud, Aedin Culhane, David Braun, Sreekumar Kodangattil, Cecile Razimbaud, Matthew Chang, Atef Fayed, Audrey Apollon, Gabriella Kastrunes, Luann Zerefa, Brandon Piel, Elena Ivanova, Dennis Bonal, Kristen Jones, Quang-De Nguyen, Zhu Zhu, Kevin Wei, Nicholas Hayden, Madison O'Donnell, Ying Huang, Rebecca Jenning, Miriam Ficial, Maura Aliezah Sticco-Ivins, Sabina Signoretti, Catherine Wu, Toni Choueiri, Jon Wee, Cloud Paweletz, David A. Barbie, Gordon Freeman, Wayne A. Marasco. Anti-CAIX Immune Restoring (IR) CAR-T cells display superior antitumor activity and reverse immunosuppressive TME in a humanized ccRCC orthotopic mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2814.

Abstract 6347: Immunotherapeutic application of induced pluripotent stem cell technology: Rejuvenated BCMA-specific CD8+T cells for multiple myeloma

Abstract T cell regenerative medicine represents an immunotherapeutic approach using antigen-specific induced Pluripotent Stem Cells (iPSC) to rejuvenate CD8+ cytotoxic T lymphocytes (CTL). Here, we report an iPSC-derived therapeutic strategy targeting B-Cell Maturation Antigen (BCMA) to overcome exhaustion of antigen-specific CTL and revitalize them to fully functional antigen-specific memory T cells to target multiple myeloma (MM). First, we established the iPSC by reprogramming IFN-γ producing heteroclitic BCMA72-80 (YLMFLLRKI) peptide-specific CD8+ CTL via Sendai virus transduction of transcription factors, OCT3/4, SOX2, KLF4 and c-MYC. The BCMA-specific iPSC demonstrated high pluripotency potential and ability to differentiate into three key germ layers, as evidenced by expression of stem cell markers (SSEA-4, TRA1-60), germ differentiation markers (SOX-17 on Endoderm, Brachyury on Mesoderm, and Pax-6 on Ectoderm) and alkaline phosphatase. The polarization of iPSC was followed during embryoid body formation into mesoderm development, evidenced by activation of transcriptional regulators SNAI2, TBX3, PLVAP, HAND1 and CDX2. Furthermore, hematopoietic progenitor cells (HPC; CD34+ CD43+/CD14- CD235a-) were sorted and induced to undergo T cell development under feeder-free culture conditions in the presence of rectonectin. Upon differentiation, phenotypic characterization revealed fully mature T cells with high expression (&amp;gt; 95%) of CD3, CD45, TCRαβ and CD8αβ, which were predominantly CD45RO+ memory T cells with high activation (CD38) and costimulatory (CD28) molecule expression, while lacking immune checkpoints (CTLA4, PD1, LAG3, Tim3). This phenotype was aligned with their high proliferative (1,800-fold increase) capacity and effective anti-tumor cytotoxicity and Th1 cytokine (IFN-γ, IL-2, TNF-α) production against MM patients’ tumor cells in antigen-specific and HLA-A2-restricted manner. Their anti-MM activities were specifically directed against the parent heteroclitic BCMA72-80 peptide via a distinct sole T cell receptor clonotype. RNAseq analyses identified specific transcriptional pathways utilized by BCMA-specific HPC during their differentiation into CD8+ CTL, which include upregulation of transcriptional regulators determining CD4/CD8 T cell differentiation ratio, memory CTL formation, NF-kappa-B/JNK pathway activation, as well as downregulation of regulators controlling B and T cell interactions or CD4+ Th cells and inhibitory receptor development. In summary, these results highlight the processes and pathways mediating somatic T cell epigenetic reprogramming and differentiation into rejuvenated BCMA-specific CD8+ CTL with high proliferation and functional anti-MM activities, providing the framework for regenerative medicine as an adoptive immunotherapy to improve patient outcome in MM. Citation Format: Jooeun Bae, Shuichi Kitayama, Zach Herbert, Laurence Daheron, Nikhil Munshi, Shin Kaneko, Jerome Ritz, Kenneth Anderson. Immunotherapeutic application of induced pluripotent stem cell technology: Rejuvenated BCMA-specific CD8+T cells for multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6347.

Abstract 1761: Treatment with antibody-targeted amanitin conjugates induces tolerability in preclinical models without triggering tolerance

Abstract Background: Amatoxin-based antibody-drug conjugates (ATACs) are a new class of ADCs using amanitin, a specific inhibitor of RNA polymerase II, as toxic payload. A first ATAC targeting B-cell maturation antigen (BCMA) is currently being tested in phase I/II clinical trials in multiple myeloma patients. During the clinical trials, the effect of repeated dosing on safety as well as anti-tumor efficacy of the ATAC will be assessed. In preclinical studies a reduction of toxicity was observed after repeated dosing with ATACs regardless of the target or antibody. In the present study, we demonstrate the effect of ATAC pre-treatment on tolerability in pre-clinical models. Material and Methods: Antibody: Engineered monoclonal antibodies produced at Heidelberg Pharma Toxic warhead: Cysteine reactive amanitin-linker constructs were synthesized at Heidelberg Pharma and conjugated site-specifically to the antibody. Animal models: Tolerability in CB17 Scid mice and Cynomolgus monkeys; Efficacy in a subcutaneous LNCaP prostate cancer model; Treatment: ADC (ATAC): escalating dosing i.v. q21d (tolerability) or repeated dosing i.v. q7dx4 (efficacy). Results: The impact of repeated dosing on the tolerability of a non-targeting ATAC was tested in CB17 Scid mice. The mice were initially treated with the maximal tolerated dose (MTD) of an ATAC, or PBS followed by a second higher dose 21 days after the first dose. Pre-treatment improved the tolerability of a second, higher dose of the same non-targeting ATAC from 12.5% to 80% survival. As ATAC toxicity is mainly caused by liver toxicity, the liver damage markers AST, ALT and LDH are used as toxicity markers in non-human primate studies. The induction of liver damage markers observed after repeated or escalated dosing was significantly lower than the induction after single or first dose treatment. Taken together, these data indicate that ATAC treatment can induce tolerability in animal models. Furthermore, in a subcutaneous LNCaP prostate cancer model, multiple ATAC dosing did improve the anti-tumor efficacy as compared to single dose treatment, indicating that the induced tolerability is not associated with reduced anti-tumor efficacy. Conclusions: ATAC pre-treatment induces tolerability in preclinical animal models without a loss in efficacy. Since this effect of ATAC pre-treatment was observed across different animal species, it likely translates also into humans. Consequently, if reduced liver toxicity and less adverse effects after repeated dosing with ATACs are also observed in the upcoming clinical trials, it might have a significant impact on treatment regimen and clinical success of ATACs. Citation Format: Kristin Decker, Marisa Schmitt, Can Araman, Franziska Ebeling, Irina Dranova, Torsten Hechler, Anikó Pálfí, Andreas Pahl, Michael Kulke. Treatment with antibody-targeted amanitin conjugates induces tolerability in preclinical models without triggering tolerance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1761.