No abstract

Introduction : Daratumumab (DARA) is a novel human CD-38-targeting monoclonal antibody in clinical development for multiple myeloma (MM). In two clinical studies (NCT00574288 [GEN501] and NCT01985126 [Sirius]), DARA monotherapy showed remarkable clinical activity and was well tolerated in heavily treated patients (pts) with relapsed and refractory (RR) MM (Lokhorst HM. J Clin Oncol 2014;32 Suppl:abstr 8513. Lonial S. J Clin Oncol 2015;33 Suppl: abstr LBA8512). A combined analysis of efficacy of 16 mg/kg DARA in these two studies is presented. Methods : GEN501, a first-in-human open-label, two-part (Part 1 dose escalation; Part 2 dose expansion) study, enrolled pts with MM that had relapsed after or were refractory to ≥2 prior therapies. Sirius, an open-label, two-part study, enrolled pts with MM with ≥3 prior therapies, including a PI or IMiD, or were refractory to both a PI and an IMiD. Eligibility criteria included pts with absolute neutrophil count ≥1000/mm3, hemoglobin ≥7.5 g/dL, platelet count ≥75×109/L (GEN501) or ≥50×109/L (Sirius), and alanine aminotransferase ≤3.5 (GEN501) or ≤2.5 (Sirius) times the upper limit of normal. In GEN501 Part 2, the first 16 mg/kg DARA infusion was followed by a 3 week rest period, and then qw for 7 weeks, q2w for 14 weeks, and q4w thereafter. In Sirius, 16 mg/kg DARA was infused qw for 8 weeks, q2w for 16 weeks, and q4w thereafter. The combined analysis comprised pts treated with 16 mg/kg DARA in Sirius and Part 2 of GEN501. In both studies overall response rates (ORR) were assessed according to IMWG response criteria. Results: The combined analysis included 148 pts (42 and 106 pts from GEN501 and Sirius, respectively). The median (range) age was 64 (31-84) years. Median time since initial diagnosis was 5.8 and 4.8 years in GEN501 and Sirius, respectively, and 62% and 82% of pts had received >3 prior therapies, respectively. In GEN501, 76% of pts were refractory to their last therapy and 64% were refractory to both a PI and IMiD; a greater proportion of pts in Sirius were refractory to their last therapy (97%) and double refractory to a PI and IMiD (95%). The ORR was 36% in GEN501 and 29% in Sirius; the ORR for the combined analysis was 31%. Best overall response is shown in Table. Responses deepened over time and the combined rate of very good partial response (VGPR) or better was 11% with 2 pts with complete responses (CR) and 3 with stringent CRs (sCR) across the two studies. In the combined analysis, median duration of response was 7.6 months and 46% of responders remained progression free at 1-year after a median follow-up of 9.3 months. Median overall survival (OS) had not been reached at median follow-up times of 10.2 months (GEN501) and 9.3 months (Sirius). The estimated 1-year OS rate (95% CI) was 77% (58-88), 65% (51-76), and 69% (58-77) for GEN501, Sirius, and the combined analysis, respectively. Forty-four of 46 responders were still alive at the time of the primary analysis. At a subsequent data cutoff for the combined analysis, after a median follow-up of 14.8 months, the estimated median OS was 19.9 months (95% CI, 15.1 - not estimable). ORR was similar across prespecified subgroups which included age, ISS stage, number of prior therapies, and refractory status. Conclusions : Single-agent DARA (16 mg/kg) demonstrated remarkable clinical activity (31% ORR) in a combined analysis of two studies in heavily pretreated MM pts. The quality of the observed responses (11% VGPR or better, 2 CRs, and 3 sCRs) was noteworthy in this highly refractory population. DARA shows promising activity in pts who have exhausted other approved myeloma treatment options. Table. Best Overall Response. 16 mg/kg MMY2002 n (%) GEN501 Part 2 n (%) Total n (%) Combined analysis set 106 42 148 Best response Stringent Complete Response (sCR) 3 (2.8) 0 3 (2.0) Complete response (CR) 0 2 (4.8) 2 (1.4) Very good partial response (VGPR) 10 (9.4) 2 (4.8) 12 (8.1) Partial response (PR) 18 (17.0) 11 (26.2) 29 (19.6) Minimal response (MR) 5 (4.7) 4 (9.5) 9 (6.1) Stable disease (SD) 46 (43.3) 22 (52.4) 68 (45.9) Progressive disease (PD) 18 (17.0) 0 18 (12.2) Not evaluable (NE) 6 (5.7) 1 (2.4) 7 (4.7) Overall response (sCR+CR+VGPR+PR) 31 (29.2) 15 (35.7) 46 (31.1) Disclosures Usmani: Celgene Corporation: Consultancy, Honoraria; Janssen: Research Funding; Onyx: Consultancy, Honoraria, Research Funding. Weiss:Janssen and Millennium: Consultancy; Janssen and Onclave: Research Funding. Bahlis:Johnson & Johnson: Research Funding; Amgen: Consultancy; Johnson & Johnson: Consultancy; Johnson & Johnson: Speakers Bureau; Celgene: Consultancy, Honoraria, Research Funding, Speakers Bureau. Lonial:Celgene: Consultancy, Research Funding; Janssen: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Millennium: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Onyx: Consultancy, Research Funding. Lokhorst:Genmab: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Amgen: Honoraria. Voorhees:Janssen, Celgene, GlaxoSmithKline,Onyx Pharmaceuticals and Oncopeptides: Consultancy, Research Funding; Array BioPharma, Celgene, GlaxoSmithKline, and Oncopeptides: Consultancy; Millennium/Takeda and Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees. Richardson:Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Millennium Takeda: Membership on an entity's Board of Directors or advisory committees; Johnson & Johnson: Membership on an entity's Board of Directors or advisory committees. Axel:Janssen: Employment. Feng:Janssen: Employment. Uhlar:Janssen: Employment. Wang:Janssen: Employment. Khan:Janssen: Employment. Ahmadi:Janssen: Employment. Nahi:Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.

Introduction of new myeloma therapies offers new options for patients refractory to immunomodulatory drugs (IMiDs) and proteasome inhibitors (PIs). In this multicenter study, patients with relapsed multiple myeloma, who have received at least three prior lines of therapy, are refractory to both an IMiD (lenalidomide or pomalidomide) and a PI (bortezomib or carfilzomib), and have been exposed to an alkylating agent were identified. The time patients met the above criteria was defined as time zero (T). Five hundred and forty-three patients diagnosed between 2006 and 2014 were enrolled in this study. Median age at T was 62 years (range 31-87); 61% were males. The median duration between diagnosis and T was 3.1 years. The median number of lines of therapy before T was 4 (range 3-13). The median overall survival (OS) from T for the entire cohort was 13 (95% confidence interval (CI) 11, 15) months. At least one regimen recorded after T in 462 (85%) patients, with a median (95% CI) progression-free survival and OS from T of 5 (4, 6), and 15.2 (13, 17) months, respectively. The study provides the expected outcome of relapsed multiple myeloma that is refractory to a PI and an IMiD, a benchmark for comparison of new therapies being evaluated.

Background: Treatment of multiple myeloma has evolved considerably in the past few years with availability of several news drugs as well as increasing use of multidrug combinations. These changes have no doubt led to the improved survival seen among patients with MM. We have previously shown that outcomes of patients intolerant or refractory to one of the IMiDs and bortezomib had a poor outcome. Since that time, other drugs of the same class as well as new classes of drugs have been introduced for the treatment of MM. We designed this retrospective study to estimate the outcomes in patients with relapsed myeloma, who have become refractory to the current generation IMiDs and proteasome inhibitors. Patients and Methods: Patients with relapsed multiple myeloma who have received at least 3 prior lines of therapy, is refractory to both an IMiD (lenalidomide or pomalidomide) AND a proteasome inhibitor (bortezomib or carfilzomib), and has been exposed to an alkylating agent were identified from multiple centers. The time patients met the above criteria was defined as T0, and details of all treatment regimens before and after T0 were collected using electronic CRFs. The study was approved by the IRB at the respective centers. Results: 543 patients were enrolled in this study; median age was 62 years (31-87) and 61% were males. Patients were enrolled from centers in North America (n=181), Europe (n=318), and Asia Pacific (n=44). Patients were diagnosed between 2006 and 2014, the median duration between diagnosis of myeloma and study entry (T0) was 3.1 years (0.3 to 9). The median (95% CI) estimated follow up from diagnosis and from T0 were 61 (57, 66) months and 13 (11, 15) months respectively. The median number of lines of therapy prior to T0 was 4 (3-13), 48% had a prior transplant. The median OS from T0 for the entire cohort was 13 (11, 15) months. For these 462 patients, the median number of recorded regimens was 2 (1-9). The overall response and the depth of response to each line of treatment following T0 are as shown in the table. The median (95% CI) PFS and OS from T0 was 5 (4, 6), and 15.2 (13, 17), respectively. The overall survival for the 81 patients with no treatment post T0 was only 2.1 months. In a multivariate analysis, duration from diagnosis to T0, ISS stage III and number of lines of therapy were all associated with inferior PFS, as well as OS, and in addition, serum creatinine>2 mg/dL at T0 also predicted inferior OS. Conclusions: The study provides the expected outcome following development of myeloma that is refractory to a PI and an IMiD. The outcomes of these patients appear to be better than we had seen historically in patients refractory/ intolerant to bortezomib and IMiDs, highlighting the increased treatment options available for these patients. However, there is decreasing response rate to sequential regimens highlighting the development of drug resistance. The data provides a bench mark for comparison of new therapies that are being evaluated in this disease. Table Table. Disclosures Dimopoulos: Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Genesis: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Kastritis:Takeda: Consultancy, Honoraria; Genesis: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Amgen: Consultancy, Honoraria. Terpos:BMS: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Other: Travel expenses, Research Funding; Celgene: Honoraria; Takeda: Consultancy, Honoraria; Genesis: Consultancy, Honoraria, Other: Travel expenses; Amgen: Consultancy, Honoraria, Other: Travel expenses, Research Funding; Novartis: Honoraria. Hillengass:Sanofi: Research Funding; Novartis: Research Funding; Amgen: Consultancy, Honoraria; BMS: Honoraria; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria. Leleu:TEVA: Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria; LeoPharma: Honoraria; Amgen: Honoraria; Bristol-Myers Squibb: Honoraria; Pierre Fabre: Honoraria; Celgene: Honoraria; Novartis: Honoraria; Takeda: Honoraria. Oriol:Janssen: Honoraria, Other: Expert board committee; Amgen: Honoraria, Other: Expert board committee. Cavo:Celgene: Consultancy, Honoraria; Millennium: Consultancy, Honoraria; Bristol-Myers Squibb: Consultancy, Honoraria; Janssen-Cilag: Consultancy, Honoraria; Amgen: Consultancy, Honoraria. Mateos:Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees. Vij:Shire: Consultancy; Takeda: Consultancy, Research Funding; Jazz: Consultancy; Karyopharma: Consultancy; Janssen: Consultancy; Novartis: Consultancy; Celgene: Consultancy; Bristol-Myers Squibb: Consultancy; Amgen: Consultancy, Research Funding. Lokhorst:Genmab: Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding. van de Donk:Amgen: Research Funding; Janssen: Research Funding; BMS: Research Funding; Celgene: Research Funding. Mark:Onyx: Research Funding, Speakers Bureau; Millenium: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Ludwig:Amgen: Research Funding, Speakers Bureau; Takeda: Research Funding, Speakers Bureau; BMS: Speakers Bureau; Janssen: Speakers Bureau. Jagannath:Novartis: Consultancy; Janssen: Consultancy; Bristol-Myers Squibb: Consultancy; Celgene: Consultancy; Merck: Consultancy. Usmani:Array: Research Funding; Britsol-Myers Squibb: Consultancy, Research Funding; Skyline: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; BioPharma: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Onyx: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics: Research Funding; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Sanofi: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Amgen: Consultancy, Research Funding, Speakers Bureau; Millenium: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Speakers Bureau. Dytfeld:Janssen Poland: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Research Funding; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees. Moreau:Novartis: Honoraria; Amgen: Honoraria; Celgene: Honoraria; Bristol-Myers Squibb: Honoraria; Takeda: Honoraria; Janssen: Honoraria, Speakers Bureau. Lee:Amgen: Membership on an entity's Board of Directors or advisory committees. Shustik:Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Millenium: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees. de la Rubia:Celgene: Consultancy; Bristol Myers: Consultancy; Amgen,: Consultancy; Janssen: Consultancy. Durie:Takeda: Consultancy; Amgen: Consultancy; Janssen: Consultancy.

73 Background Daratumumab (HuMax™-CD38) is a human CD38 monoclonal antibody with broad-spectrum killing activity and effectively mediates killing of CD38-expressing tumor cells via antibody-dependent cell-mediated cytotoxicity, complement-dependent cytotoxicity and apoptosis. In this present ongoing first-in-human (FIH) dose-escalation study of daratumumab in pts with multiple myeloma (MM) (ClinicalTrials.gov CT00574288), the safety profile has been acceptable and preliminary efficacy data have already been published1,2. Here we present data from the dose escalation part of the study. Objectives The primary objective was to establish the safety profile. The secondary objectives were to establish the maximum tolerated dose (MTD), assessment of efficacy, pharmacokinetics (PK) and immunogenicity – Anti-Drug-Antibodies (ADA). Methods Pts ≥18 years and diagnosed with MM requiring systemic therapy and considered relapsed or refractory to at least two different prior lines of therapy and ineligible for ASCT were enrolled. The study was based on a 3+3 dose-escalation design. Daratumumab was administered over a 9-week period consisting of 2 pre- and 7 full doses. The doses ranged from 0.005 mg/kg to 24 mg/kg. Prednisolone/methylprednisolone was administered to prevent infusion related events (IREs) in a maximum dose equivalent to 27mg dexamethasone per week. Daratumumab plasma concentrations were measured by ELISA. Evaluation of efficacy data was according to IMGW guidelines3. A bridging ElectroChemiLuminesence (ELC) method on the MesoScale Discovery platform was used to detect ADA responses in pts to daratumumab. The results presented are based on data analyzed before database lock. Results Data from 32 pts including 2 pts in the ongoing 24mg/kg cohort were collected until now. Median age was 61 years (42–76). The median number of prior treatment lines was: 6.3 (2–12). PK analysis showed plasma peak levels as expected, but relatively rapid clearance at low dose levels. The clearance rate decreased with increasing dose suggesting an effect of target binding on the PK. At doses ≥ 4 mg/kg, daratumumab trough levels were consistent ≥ 10 μg/ml and observed PK values approximately estimated PK values (Figure 1). Preliminary efficacy evaluation in this abstract was based on best response to paraprotein as reflected by change in serum or urine M-component or free light chains (FLC) according to IMGW guidelines3. For groups ≤ 2 mg/kg, 4/20 pts achieved a reduction in paraprotein (12%, 14%, 19%, 55%); in the 4 mg/kg group, 3/3 pts had a reduction in paraprotein of 49%, 100%, and 64%, respectively. In the 8 mg/kg group, 2/3 pts had a reduction in paraprotein of 39%, and 100%, respectively whereas in the 16mg/kg cohort, 2/3 pts had a reduction in paraprotein of 50%, and 33%, respectively. A reduction of 80%-100% in the bone marrow plasma cells was seen in the 4 mg/kg group and onwards. No detectable ADA responses were found in the pts. No DLTs were reported in the 2, 4, 8 and 16mg/kg cohorts. The most common adverse events reported were infusion related events. The observed IREs occurred predominantly during the initial infusions, 10% of pts reported IREs during the pre-dose, 30% during the first full infusion with a gradual decrease in frequency after the 2nd full infusion. No dose relationship was observed. Most IREs had onset within 3–4 hours of infusion, two of the IREs were grade 3 and the remaining grade 1–2. Four IREs were SAEs; however, since implementation of steroids before all infusions and dilution of trial drug, no serious IREs were reported in the 4, 8 and 16mg/kg cohorts. Conclusion In pts with relapsed or refractory MM treated with daratumumab, a marked reduction in paraprotein and bone marrow plasma cells was observed in the higher dose cohorts. This has not previously been demonstrated with a single-agent monoclonal antibody in MM. No unexpected buildup of daratumumab was seen and in pts treated with 4mg/kg and upwards the observed plasma concentrations were close to those predicted. No ADA responses were detected. The MTD was not yet established and the toxicity was manageable. All data available from part 1 will be presented at the meeting. Disclosures: Plesner: Genmab: Consultancy; Janssen Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Celgene Corporation: Membership on an entity's Board of Directors or advisory committees. Lokhorst:Genmab: Consultancy. Lisby:Genmab: Employment. Richardson:Millenium Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Celgene Corporation: Membership on an entity's Board of Directors or advisory committees; Novartis Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Johnson & Johnson: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees.

Introduction: Daratumumab (DARA) is a human monoclonal IgG1κ CD38 antibody that functions through multifaceted mechanisms of action, including CDC, ADCC, ADCP, induction of apoptosis and immunomodulatory activity (Krejcik et al, Blood 2016;128:384-394). DARA was added to standard of care (SOC) regimens in two randomized, controlled, phase 3 trials in RRMM: POLLUX (DARA+lenalidomide/dexamethasone [DRd] vs lenalidomide/dexamethasone [Rd]) and CASTOR (DARA+bortezomib/dexamethasone [DVd] vs bortezomib/dexamethasone [Vd]). The addition of DARA to these regimens resulted in significant improvements in PFS (hazard ratio for PFS: 0.37 and 0.39 for POLLUX and CASTOR, respectively) and ORR (POLLUX: 93% DRd vs 76% Rd; CASTOR: 83% DVd vs 63% Vd) (Dimopoulos MA et al, N Engl J Med 2016; in press; Palumbo A et al, N Engl J Med 2016; in press). To determine the ability of DARA to drive deep clinical responses beyond complete response (CR), MRD was assessed in both POLLUX and CASTOR using next-generation sequencing (NGS) of B cell receptor (Ig). This is the first comprehensive and prospective study of MRD to date in randomized phase 3 clinical trials of RRMM patients and investigates the ability of DARA-containing regimens to drive deep responses in this challenging population. Methods: MRD was assessed in POLLUX (blinded to treatment group) at the time of suspected CR, and at 3 and 6 months post-suspected CR for patients who maintained this response. Similarly, in CASTOR, MRD was assessed for patients at the time of suspected CR (blinded to treatment group) and at 6 months and 12 months after first dose (at the end and 6 months after end of Vd background therapy, respectively). MRD was assessed on bone marrow aspirate samples prepared using Ficoll and evaluated by the ClonoSEQTM assay (Adaptive Biotechnologies, Seattle, WA, USA) at sensitivities of 0.01% (1 cancer cell per 10,000 nucleated cells or 10-4), 0.001% (10-5), and 0.0001% (10-6). The MRD negative rate per treatment arm was determined as the proportion of patients with negative MRD at any time point after the first dose and compared using the likelihood-ratio test. To allow for a stringent, unbiased evaluation of MRD in these studies, the entire intent-to-treat population was evaluated where patients were considered MRD positive if they had only MRD positive test result or had no MRD assessment. In POLLUX, 63% in DRd and 87% in Rd did not receive a MRD assessment, and for CASTOR, 76% in DVd and 87% in Vd were not assessed for MRD. Results: Median duration of follow-up was 13.5 months and 7.4 months in POLLUX and CASTOR, respectively. The addition of DARA to SOC regimens (Rd in POLLUX or Vd in CASTOR) resulted in significantly higher MRD negative rates at all three thresholds examined (10-4, 10-5, and 10-6; Table). Additionally, patients who achieved MRD negative status experienced fewer PFS events compared with MRD positive patients at a threshold of 10-5 (Figure). Among pts who achieved CR or better, the rate of MRD negativity was at least 3-fold higher across all sensitivity thresholds in the DARA + SOC treatment groups compared with SOC alone. In MRD positive patients, PFS was significantly longer in the DARA + SOC treatment groups compared with SOC alone treatment arms. Updated data from both studies will be presented at the annual meeting. Conclusion: These two studies represent the first randomized, controlled, prospective evaluation of MRD in the RRMM phase 3 clinical trial setting and demonstrate that DARA-containing therapies are able to drive patients to remarkably deep levels of clinical response. Regardless of the SOC component, DARA-containing regimens consistently demonstrated ≥3-fold increase in MRD negative rate compared with the control groups at all evaluated thresholds. Importantly, since patients who achieved MRD negative status demonstrated low PFS event rates, the deep clinical responses induced by DARA may lead to improved survival. Table MRD negative Rate Based on Threshold Used Table. MRD negative Rate Based on Threshold Used Figure Progression-free survival by MRD status in POLLUX and CASTOR Figure. Progression-free survival by MRD status in POLLUX and CASTOR Disclosures Avet-Loiseau: Celgene: Honoraria, Research Funding, Speakers Bureau; Amgen: Honoraria, Speakers Bureau; BMS: Honoraria, Speakers Bureau; Sanofi: Honoraria, Speakers Bureau; Janssen: Honoraria, Research Funding, Speakers Bureau. Casneuf:Janssen R&D, Beerse, Belgium: Employment; Johnson & Johnson: Equity Ownership. Chiu:Janssen: Employment. Moreau:Janssen: Honoraria, Speakers Bureau; Amgen: Honoraria; Novartis: Honoraria; Takeda: Honoraria; Bristol-Myers Squibb: Honoraria; Celgene: Honoraria. Plesner:Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding. Khokhar:Janssen: Employment. Qi:Janssen: Employment. Schecter:Janssen: Employment, Equity Ownership. Carlton:Adaptive Biotechnologies: Employment, Equity Ownership. Qin:Janssen: Employment. Liu:Janssen: Employment; J&J: Equity Ownership; Merck: Equity Ownership. Wu:Janssen: Employment. Zhuang:Janssen: Employment. Ahmadi:Janssen: Employment. Sasser:J&J: Equity Ownership; Janssen: Employment. San-Miguel:Amgen: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Onyx: Membership on an entity's Board of Directors or advisory committees; Millennium: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; MSD: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees.

Introduction: Teclistamab (JNJ-64007957) is a T-cell redirecting, bispecific IgG4 antibody that targets both B-cell maturation antigen (BCMA) and CD3 receptors to induce T-cell mediated cytotoxicity of BCMA-expressing myeloma cells. Teclistamab is under investigation in MajesTEC-1, an ongoing phase 1/2 study in patients (pts) with heavily pretreated relapsed/refractory multiple myeloma (RRMM). Results from the phase 1 study (parts 1 and 2; NCT03145181) indicated that teclistamab is well tolerated at the recommended phase 2 dose (RP2D) and has encouraging efficacy, with an overall response rate (ORR) of 65% and very good partial response or better (≥VGPR) rate of 58% in 40 pts after a median of 6.1 mo of follow-up. Here we report for the first time initial data from the phase 2 portion of MajesTEC-1 (part 3; NCT04557098) and updated results for phase 1 pts treated at the RP2D. Methods: Pts (aged ≥18 years) were diagnosed with MM per International Myeloma Working Group (IMWG) criteria, had measurable disease and were exposed to a proteasome inhibitor, immunomodulatory drug, and anti-CD38 antibody. In phase 1, pts were relapsed, refractory or intolerant to established therapies. In phase 2, pts received ≥3 prior lines of therapy. The primary objectives in phase 1 were to identify the RP2D and to characterize safety and tolerability of teclistamab at the RP2D. The primary objective in phase 2 is to evaluate the efficacy of teclistamab at the RP2D (primary endpoint: ORR). Pts treated at the RP2D received a weekly dose of subcutaneous teclistamab 1500 µg/kg following step-up doses of 60 and 300 µg/kg. Responses reported here were investigator-assessed per IMWG criteria. Adverse events (AEs) are graded according to CTCAE v4.03. Cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) were graded according to ASTCT criteria. Results: As of June 14, 2021, 159 pts (median age 64.0 y [range 33-84]; 15% ≥75 y; 59% male) were treated at the RP2D (phase 1: 40 pts; phase 2: 119 pts). Pts received a median of 5 prior lines of therapy (range: 2-15); 100% were triple-class exposed, 69% were penta-drug exposed, 77% were triple-class refractory, and 29% were penta-drug refractory. As of the clinical cutoff, no new safety signals were identified in phase 2. The most common nonhematologic AEs in all 159 pts treated at the RP2D were CRS (67%; grade 1/2: 99%; 1 pt had a transient grade 3 event; median time to onset 2 days [range 1-6]; median duration 2 days [range 1-9]), injection site erythema (23%; all grade 1/2), and fatigue (22%; grade 3/4: 2%). The most common hematologic AEs were neutropenia (53%; grade 3/4: 45%), anemia (41%; grade 3/4: 27%), and thrombocytopenia (33%; grade 3/4: 18%). Four pts (2.5%) developed ICANS (all grade 1/2; all resolved). Pharmacokinetic and pharmacodynamic data from phase 2 support earlier phase 1 findings. Teclistamab exposure at the RP2D was sustained across the dosing interval and exceeded target exposure levels. Pharmacodynamic data for phase 1/2 pts treated at the RP2D showed induction of proinflammatory cytokines and T-cell activation, consistent with teclistamab's mechanism of action. At clinical cutoff for this abstract, efficacy data for the phase 2 study are immature. At a median follow-up of 8.2 mo (range 1.2-15.2), response rates in the 40 phase 1 pts treated at RP2D were consistent with previously presented data (ORR: 65% [95% CI 48-79]; ≥VGPR rate: 60% [95% CI 43-75]; complete response or better rate: 40% [95% CI 25-57]). Responses deepened over time, and with longer follow-up of responders compared with previously presented data (median follow-up of 9.5 mo vs 7.1 mo) remained durable (Figure). No additional responders had disease progression, and 85% (22/26) of responders are continuing on treatment, including 1 pt with 15.2 mo of follow-up. Median duration of response (DOR) has not been reached; the 6-month DOR rate is 90% [95% CI 63-97]. The efficacy data will be updated at the time of congress to include a minimum follow-up of ~6 mo for 150 pts treated at the RP2D (prior to March 19, 2021). Conclusions: Evaluation of teclistamab at the RP2D in 159 pts provides robust data to support safety; inclusion of phase 2 pts at the time of presentation will provide more robust efficacy data. Data from MajesTEC-1 continue to show that teclistamab monotherapy induces deep and durable responses in heavily pretreated pts with RRMM with a manageable safety profile. Figure 1 Figure 1. Disclosures Moreau: Celgene BMS: Honoraria; Sanofi: Honoraria; Janssen: Honoraria; Abbvie: Honoraria; Amgen: Honoraria; Oncopeptides: Honoraria. Usmani: Janssen Oncology: Consultancy, Research Funding; Takeda: Consultancy, Research Funding, Speakers Bureau; SkylineDX: Consultancy, Research Funding; Seattle Genetics: Consultancy, Research Funding; Pharmacyclics: Consultancy, Research Funding; Merck: Consultancy, Research Funding; Sanofi: Consultancy, Research Funding, Speakers Bureau; Janssen: Consultancy, Research Funding, Speakers Bureau; EdoPharma: Consultancy; GSK: Consultancy, Research Funding; Celgene/BMS: Consultancy, Research Funding, Speakers Bureau; Array BioPharma: Consultancy, Research Funding; Abbvie: Consultancy; Amgen: Consultancy, Research Funding, Speakers Bureau; Bristol-Myers Squibb: Research Funding. Garfall: Amgen: Honoraria; Tmunity Therapeutics: Research Funding; Novartis: Research Funding; GSK: Honoraria; Janssen: Honoraria, Research Funding. van de Donk: BMS/Celgene: Consultancy, Honoraria; Janssen: Consultancy, Research Funding; Amgen: Consultancy, Research Funding; Cellectis: Research Funding; Takeda: Consultancy; Roche: Consultancy; Novartis /bayer/servier: Consultancy. Nahi: XNK Therapeutics AB: Consultancy. San-Miguel: AbbVie, Amgen, Bristol-Myers Squibb, Celgene, GlaxoSmithKline, Janssen, Karyopharm, Merck Sharpe & Dohme, Novartis, Regeneron, Roche, Sanofi, SecuraBio, and Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees. Oriol: GSK: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Karyopharm: Consultancy, Membership on an entity's Board of Directors or advisory committees; Oncopeptides: Consultancy, Membership on an entity's Board of Directors or advisory committees; BMS/Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Nooka: GlaxoSmithKline: Consultancy, Other: Travel expenses; Bristol-Myers Squibb: Consultancy; Sanofi: Consultancy; Oncopeptides: Consultancy; Janssen Oncology: Consultancy, Research Funding; Takeda: Consultancy, Research Funding; Amgen: Consultancy, Research Funding; Adaptive technologies: Consultancy; Karyopharm Therapeutics: Consultancy. Martin: Amgen: Research Funding; Sanofi: Research Funding; Janssen: Research Funding; GlaxoSmithKline: Consultancy; Oncopeptides: Consultancy. Rosinol: Janssen, Celgene, Amgen and Takeda: Honoraria. Chari: Seattle Genetics: Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS/Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Oncopeptides: Consultancy, Membership on an entity's Board of Directors or advisory committees; Karyopharm: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Shattuck Labs: Consultancy, Membership on an entity's Board of Directors or advisory committees; Millenium/Takeda: Consultancy, Research Funding; Secura Bio: Consultancy, Membership on an entity's Board of Directors or advisory committees; Sanofi Genzyme: Consultancy, Membership on an entity's Board of Directors or advisory committees; GlaxoSmithKline: Consultancy, Membership on an entity's Board of Directors or advisory committees; Antengene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Research Funding; Novartis: Consultancy, Research Funding; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Research Funding; Janssen Oncology: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Karlin: Abbvie: Honoraria; Amgen: Honoraria, Other: travel support and advisory board ; GSK: Honoraria, Other: member of advisory board; Janssen: Honoraria, Other: member of advisory board, travel support; Takeda: Honoraria, Other: member of advisory board; Celgene-BMS: Honoraria, Other: member of advisory board; Sanofi: Honoraria; oncopeptide: Honoraria. Mateos: Regeneron: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Honoraria; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene - Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bluebird bio: Honoraria; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Oncopeptides: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sea-Gen: Honoraria, Membership on an entity's Board of Directors or advisory committees; GSK: Honoraria; Oncopeptides: Honoraria. Bahlis: Janssen: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Genentech: Consultancy; Sanofi: Consultancy, Honoraria; GlaxoSmithKline: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; BMS/Celgene: Consultancy, Honoraria; Karyopharm: Consultancy, Honoraria. Popat: Takeda: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES; AbbVie, BMS, Janssen, Oncopeptides, and Amgen: Honoraria; GlaxoSmithKline: Consultancy, Honoraria, Research Funding; Abbvie, Takeda, Janssen, and Celgene: Consultancy; Janssen and BMS: Other: travel expenses. Besemer: GSK: Honoraria; Janssen: Honoraria; Takeda: Honoraria. Martínez-López: Janssen, BMS, Novartis, Incyte, Roche, GSK, Pfizer: Consultancy; Roche, Novartis, Incyte, Astellas, BMS: Research Funding. Sidana: Allogene: Research Funding; Janssen: Consultancy, Research Funding; Magenta Therapeutics: Consultancy, Research Funding; BMS: Consultancy. Pei: Janssen: Current Employment, Current holder of individual stocks in a privately-held company. Trancucci: Janssen: Current Employment, Current holder of individual stocks in a privately-held company. Verona: Janssen: Current Employment. Girgis: Janssen: Current Employment, Current holder of individual stocks in a privately-held company. Olyslager: Janssen: Current Employment. Jaffe: Janssen: Current Employment. Uhlar: Janssen: Current Employment, Current holder of individual stocks in a privately-held company. Stephenson: Janssen: Current Employment, Current holder of individual stocks in a privately-held company. Van Rampelbergh: Janssen: Current Employment. Banerjee: Janssen: Current Employment, Current holder of individual stocks in a privately-held company. Goldberg: Janssen: Current Employment, Current holder of individual stocks in a privately-held company. Kobos: Janssen: Current Employment, Current holder of individual stocks in a privately-held company. Krishnan: MAGENTA: Consultancy; BMS: Consultancy, Current equity holder in publicly-traded company, Speakers Bureau; JANSSEN: Consultancy, Research Funding; City of Hope Cancer Center: Current Employment; REGENERON: Consultancy; SANOFI: Consultancy; GSK: Consultancy; Amgen: Speakers Bureau.

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