Krishnan, Amrita

Abstract Introduction: Bispecific T-cell engagers (TCE) targeting BCMA (teclistamab, elranatamab) and GPRC5D (talquetamab) are important therapeutic options in relapsed/refractory MM (RRMM). However, data on the independent prognostic impact of individual cytogenetic abnormalities and functional high-risk MM on outcomes with TCEs remains limited. Methods We included RRMM patients treated with BCMA TCEs (teclistamab, elranatamab) and talquetamab across 15 centers in the US. Patients where TCEs were used only as bridging therapy to CAR-T were excluded. High-risk cytogenetic abnormalities (HRCA) included del(17p), t(4;14), t(14;16), 1q gain/amplification (1q21+), del(1p) before initiation of TCE. Functional high-risk disease (FHRMM) was defined as PFS <18 months with frontline therapy. Extramedullary disease (EMD) included visceral or soft tissue disease and excluded paraskeletal disease. Progression-free survival (PFS) was estimated from TCE initiation using the Kaplan–Meier method and compared using the log-rank test. Univariate and multivariable Cox proportional hazards models were used to identify predictors of PFS in the entire cohort and the subcohorts of BCMA TCEs and talquetamab (Talq). Results We analyzed 943 treatment initiations with TCEs in RRMM, comprising 577 BCMA-directed TCEs [teclistamab (n=436) and elranatamab (n=141)] and 366 talquetamab initiations. The median follow-up from TCE initiation was 13.4 months (95% CI: 12.5–14.2) and median age was 68 years (interquartile range 61-75 years). Two ore more HRCAs were noted in 30% of the cohort (34% in Talq vs. 28% in BCMA TCEs, p=0.04), EMD was present in 21% of patients (26% in Talq vs. 18% in BCMA TCEs, p=0.002), and 45.5% of patients had FHRMM (47% in Talq vs. 45% in BCMA TCE, p=0.54). The median prior lines of therapy was 6 (interquartile range: 5-8), with 92% being triple-class refractory (TCR); 60% received prior BCMA-directed therapy (85% in Talq vs. 45% in BCMA TCE, p<0.0001) and 45% had prior CAR-T in 45% (57% in Talq vs. 37% in BCMA TCE, p<0.001). The best overall response rate (ORR) was 67.1 % for the entire cohort (66.4% for BCMA cohort and 68.2% for Talq), with 32.5% patients achieving a ≥ complete response. The median PFS was 7.7 months (95% CI: 6.7–8.6) for the entire cohort, with a median PFS of 10.1 months (95% CI: 7.5-13.4) for teclistamab and 10.1 months (95% CI: 3.9-NR) for elranatamab. In the more heavily pretreated talq cohort, the median PFS was 6.4 months (95% CI: 5.1-7.5). In a univariate analysis (UVA), several HRCAs were associated with inferior PFS−del(17p) (HR 1.59), t(4;14) (HR 1.43), del(1p) (HR 1.54), and ≥2 HRCAs (HR 1.64), all p<0.01. Apart from HRCAs, adverse disease characteristics included FHRMM (HR 1.20) and EMD (HR 1.46); all p<0.05. Among laboratory markers, hemoglobin <9 g/dL (HR 2.10), platelet count <75 ×10⁹/L (HR 1.96), and elevated ferritin (≥600 ng/mL; HR 2.17) (all p<0.01) were prognostic for PFS. ECOG ≥2 (HR 1.62), prior BCMA-directed therapy (HR 1.56), and prior CAR-T (HR 1.44) (all p<0.001) were also associated with inferior PFS. In a multivariable analysis (MVA), prior BCMA therapy (HR 1.72, p<0.0001), ferritin >600 ng/mL (HR 1.68, p<0.0001), hemoglobin <9 g/dL (HR 1.53, p=0.001), ECOG PS ≥2 (HR 1.52, p=0.0009), del(17p) (HR 1.44, p=0.0034) and FHRMM (HR 1.26, p=0.047), were associated with inferior PFS. Within the talq cohort (n=366), EMD (HR 1.64), del(17p) (HR 1.42), del(1p) (HR 1.54), FHRMM (HR 1.34), ECOG ≥2 (HR 1.56), ferritin >600 (HR 1.88), hemoglobin <9 g/dL (HR 1.6), platelet count <75 ×10⁹/L (HR 1.36) and leukopenia <0.25 x 10⁹/L (HR 1.52) were adverse prognostic markers on UVA. A MVA confirmed the independent impact of ferritin >600 ng/mL (HR: 1.77), ECOG ≥2 (HR 1.61) and functional high-risk status (HR 1.52) on PFS, whereas del(17p) and EMD were trending toward significance. Within the BCMA TCE cohort (n=577), prior BCMA therapy (HR 1.9), ferritin >600 (HR 1.79), ECOG ≥2 (HR 1.55), Hb <9 g/dL (HR 1.54), and del(17p) (HR 1.52) were independently associated with inferior PFS on a MVA.Conclusions: In this large real-world cohort of TCE, outcomes varied by fitness, disease biology, and treatment history. The ECOG PS, elevated ferritin, functional high-risk status and del(17p) were consistently associated with inferior PFS. Prior BCMA exposure was an independent risk factor for inferior PFS in the BCMA TCE cohort, but not with talquetamab.

Background: 24-hour urine (24HRU) assessments are a key component of International Myeloma Working Group (IMWG) response criteria for multiple myeloma (MM) and are requested longitudinally in clinical trials even if not routinely used in real-world practice. Several analyses have suggested a limited role for 24HRU if serum immunofixation or free light chain (LC) testing is abnormal (Dejoie Blood 2016, Lahuerta Blood 2023). Adopting urine-free response criteria (with 24HRU removal from every level of IMWG response) may change responses in <5% of patients (Natsuhara et al, Leuk Lymph 2023) but not have been studied in terms of progression-free survival (PFS) in a larger population. Methods: This was a secondary analysis of data from the Phase 3 BMT CTN 0702 (STaMINA) trial (Stadtmauer et al, JCO 2019) studying post-autologous stem cell transplantation (ASCT) strategies. Only patients evaluable for Day +56 response following ASCT were included, and patients with progressive disease (PD, n=8) at this timepoint were excluded. Post-ASCT responses relative to diagnosis were calculated by two sets of criteria. First, traditional responses were calculated per IMWG criteria (Kumar et al, Lancet Onc 2016) as stable disease (SD), partial response (PR), very good PR (VGPR), or complete response (CR, including stringent CR). Second, urine-free response assessments were calculated as follows: negative 24HRU immunofixation no longer required for CR, 24HRU M-protein < 100 milligrams (mg) per day no longer required for VGPR, and no 24HRU M-protein thresholds (e.g., < 200 mg per day or > 90% reduction) required for PR. PFS was estimated (using PD by traditional IMWG criteria or death as events) using proportional hazard models. Results: Of 636 evaluable patients (84% of all BMT CTN 0702 participants), LC-only disease was noted in 18.9% (n=120). Pre-enrollment 24HRU testing at diagnosis was done in 28.9% of patients (n=184). IMWG responses were as follows: CR, 29.4% (n=187) traditional vs 29.7% (n=189) urine-free; VGPR, 37.0% (n=235) traditional vs 36.6% (n=233) urine-free; PR, 30.7% (n=195) for both; SD, 3.0% (n=19) for both. A total of 4 responses (0.6%) changed with urine-free criteria. Three patients were ‘upgraded’ (VGPR to CR, n=2, PR to VGPR, n=1) because 24HRU requirements for CR/VGPR were no longer required. One patient without a measurable serum paraprotein was ‘downgraded’ from a traditional VGPR (with negative 24HRU immunofixation) to a urine-free PR based on LC-only criteria. Among the subset of 184 patients with 24HRU electrophoresis results at diagnosis, there were no differences between traditional and urine-free IMWG responses. Median PFS and 95% confidence intervals (CI) were the same at each depth of both traditional and urine-free criteria: 63.0 months (50.8 - 71.4 months) for CR, 49.6 months (42.6 - 55.1 months) for VGPR, 44.9 months (37.2-54.8 months) for PR, and 34.4 months (14.0-51.5 months) for SD. Urine-free IMWG criteria were highly prognostic for PFS (p = 0.006, 95% CI 1.05-1.36). The achievement of urine-free CR vs urine-free ≤CR was also prognostic (p = 0.005, 95% CI 0.54 - 0.89). Urine-free VGPR vs urine-free ≤VGPR was of borderline significance (p = 0.102, 95% CI 0.66 - 1.04), with median PFS 53.8 months (48.0 - 57.6 months) vs 44.6 months (36.3 - 54.7 months) respectively. Discussion: In this secondary analysis of a Phase 3 trial, omitting 24HRU assessments from IMWG criteria changed <1% of responses and had no impact on PFS prediction at any response depth. 24HRU assessments had been performed for less than a third of patients as standard of care prior to study entry, underscoring its infrequent use outside of trials. Urine-free IMWG assessments would reduce time toxicity and discomfort for patients, particularly for those with limited dexterity. If implemented in trials, they would also simplify study logistics and lower operational costs. Outside of situations such as AL amyloidosis where 24HRU assessments remain critical or for patients with urine as their only measurable MM biomarker, our results support the removal of 24HRU assessments from future iterations of IMWG response criteria. Funding: Grants #U10HL069294 and #U24HL138660 to the BMT CTN from the NHLBI and the NCI; contributions by Celgene Corporation and Millennium Pharmaceuticals, Inc.; funding by The Alliance for Clinical Trials in Oncology, the ECOG-ACRIN Cancer Research Group and SWOG.

Introduction: BCMA-directed CAR-T and Bispecific T-cell engager (BiTE) therapies have shown remarkable overall response rates in heavily pretreated patients with relapsed/refractory multiple myeloma (RRMM). This has led to the approval of idecabtagene vicleucel, ciltacabtagene autoleucel and teclistamab by the FDA, EMA and other regulatory agencies. We performed a global survey on accessibility, practice patterns, and toxicity management of commercially available CAR-T and BiTE therapies. Methods: An online survey was completed by clinicians attending the International Myeloma Society's Immune Effector Cell Therapies in Multiple Myeloma Workshop, in-person or virtually, made available for 30 days after the meeting held in March 2023, Boston, MA. Results: 87 clinicians from 16 countries completed the survey, most practicing in an academic practice (86%) and in an urban environment (89%). Sixty-four percent of the respondents practice in North America followed by Europe (25.3%) including Germany, United Kingdom, Ireland, Italy, Netherlands, Spain, France, Greece, and Cyprus, and 6.9% from Asia and 3.4% from Australia. Seventy-seven percent reported CAR-T cell therapy was approved in their country with 44.8% treating 1-5 patients and 14.9% treating >5 patients per month; 67% reported BiTE therapy was approved in their country with 14.9% treating >5 patients per month. Of evaluable responses (n = 40), 62% administered CAR-T therapy inpatient and 15% administered CAR-T therapy outpatient ≥ 50% of the time. Length of time between decision to treat with CAR-T therapy to infusion was 6-12 weeks for 42% of responders and <6 weeks for only 20%. Most (75%) reported inpatient administration of BiTE therapy step-up dosing; 17.5% reported outpatient step-up dosing administered ≥ 50% of the time. Use of institutional or practice SOPs for CAR-T and BiTE therapy patient selection was reported by 85% and 58%, respectively, with the factors influencing SOP outlined in Table 1. Of available CAR-T therapies, 53% prefer cilta-cel and 23% reported CAR-T therapy preference depended most on patients' co-morbidities/frailty (89%), timing of next available apheresis (67%), age (56%), CNS disease (44%) and other factors. Maintenance therapy after CAR-T therapy was reportedly used by 25% and 5% of respondents in 1-10% and 11-50% of their patients, respectively, to “maintain level of response achieved” (50%) or “achieve a deeper level of response” (25%). About half (43%) of the respondents reported using an SOP or particular criteria for secondary Hemophagocytic Lympho-Histiocytosis/Macrophage Activation Syndrome/CAR-related-HLH (sHLH/MAS/CarHLH) management that varied between the use of ASTCT Working Group IEC associated HLH-like syndrome Criteria (47%) (Hines 2023), CARTOX HLH Criteria (24%) (Neelapu 2017) and HLH-2004 criteria (6%). Tocilizumab was used as cytokine release syndrome (CRS) prophylaxis only by one responder. Keppra neurologic prophylaxis was used by 47.5% and 15% of responders for CAR-T and BiTE therapy, respectively. Delayed neurotoxicity with CAR-T was reported in 1-5% of patients by 57.5% of responders and 6-10% of patients by 15% of responders; most common manifestations were other movement/neuromuscular disorder (62%), nerve palsy (55%), and Parkinsonism (45%). Infectious prophylaxis was used to protect against HSV (92.5%), PJP (90%), bacterial pathogens (55%), fungal pathogens (60%), and IVIG (77.5%). However, criteria for infectious prophylaxis use varies widely incorporating IgG levels, infectious history, CD4+ count, B-cell aplasia and cytopenias (48.1 - 88.9%). Most respondents (46.3 - 86.5%) reported completing an infectious work-up including CMV, EBV, Hep B/C, and HIV ( Table 2). Conclusions: Trends of CAR-T and BiTE therapy use and patterns of concurrent prophylactic and supportive care in MM vary widely among academic centers across the globe, demonstrating a need for further understanding of toxicity pathogenesis, toxicity management and consistent guidelines. This survey also demonstrates the great unmet need for access beyond urban centers among the international myeloma community. Prospective studies and claims data analysis should be utilized to evaluate the longitudinal cost of care, quality of life, duration of response and management of infectious disease, neurological or related complications of CAR-T and bispecific TCE therapies.

Abstract Background: Fc receptor-homolog 5 (FcRH5) is a type I membrane protein that is expressed exclusively in the B-cell lineage, and at a higher level on myeloma cells than on normal B cells. Cevostamab is a FcRH5xCD3 bispecific antibody (BsAb) that facilitates T cell-directed killing of myeloma cells. Initial data from the dose-escalation phase of the ongoing Phase I study (NCT03275103) of cevostamab monotherapy in patients (pts) with heavily pre-treated RRMM demonstrated promising activity and manageable safety, along with near ubiquitous FcRH5 expression on myeloma cells (Cohen et al. ASH 2020; Sumiyoshi et al. EHA 2021). We present updated safety and efficacy data from a larger cohort of pts, including results comparing Cycle (C) 1 single step-up (SS) and double step-up (DS) dosing for the mitigation of cytokine release syndrome (CRS). Methods: Participants have RRMM for which no established therapy is available or appropriate. Cevostamab (intravenous infusion) is administered in 21-day cycles. In the SS cohorts, the step dose (0.05-3.6mg) is given on C1 Day (D) 1 and the target dose (0.15-198mg) on C1D8. In the DS cohorts, the step doses are given on C1D1 (0.3-1.2mg) and C1D8 (3.6mg), and the target dose (60-160mg) on C1D15. In both regimens, the target dose is given on D1 of subsequent cycles. Cevostamab is continued for a total of 17 cycles, unless progressive disease or unacceptable toxicity occurs. CRS is reported using ASTCT criteria (Lee et al. Biol Blood Marrow Transplant 2019). Results: At data cut-off (18 May 2021), 160 pts had been enrolled (median age: 64 years, range: 33-82 years; male: 58.1%); 21.3% of pts had extramedullary disease. Median number of prior lines of therapy was 6 (range: 2-18). Most pts (85.0%) were triple-class refractory (PI, IMiD, anti-CD38 antibody). 28 pts (17.5%) had received ≥1 prior CAR-T, 13 pts (8.1%) ≥1 prior BsAb, 27 pts (16.9%) ≥1 prior antibody-drug conjugate (ADC), and 54 pts (33.8%) ≥1 prior anti-BCMA targeting agent. Median follow-up in exposed pts was 6.1 months. Almost all had ≥1 adverse event (Table). The most common was CRS (128/160 pts [80.0%]; Grade [Gr] 1: 42.5%; Gr 2: 36.3%; Gr 3: 1.3%). Immune effector cell-associated neurotoxicity syndrome (ICANS) associated with CRS was observed in 21 pts (13.1%) and in 34/211 (16.1%) CRS events (Gr 1: 8.5%; Gr 2: 6.2%; Gr 3: 1.4%). Most CRS events occurred in C1 (87.2%), arose within 24 hours of cevostamab administration (70.5%), and resolved within 48 hours of onset (83.4%). In the pts with CRS, tocilizumab was used for CRS management in 43.8% and steroids in 25.8% (both agents: 18.0%). In SS dose-escalation (68 pts), 3.6mg was chosen as the most effective C1D1 SS dose for limiting CRS in C1, with no target dose-dependent increase in the rate or severity of CRS observed after the C1D8 administration. Likewise, in DS dose-escalation (30 pts), 0.3/3.6mg was identified as the preferred C1D1/C1D8 DS dose for limiting CRS in C1. Notably, the overall rate of CRS was lower in the pts who received the 0.3/3.6mg/target DS regimen than in those who received the 3.6mg/target SS regimen (77.3% [34/44] vs 88.2% [75/85], respectively). The rate of ICANS associated with CRS was also lower in the 0.3/3.6mg/target DS cohort than in the 3.6mg/target SS cohort (4.5% [2/44] vs 21.2% [18/85], respectively). At data cut-off, 158/160 pts were efficacy evaluable. In dose-escalation, responses were observed at the 20-198mg target dose levels, and data suggested a target dose-dependent increase in clinical efficacy. Median time to response was 29 days (range: 20-179 days). Two dose-expansion cohorts were opened: ORR was higher at the 160mg dose level (54.5%, 24/44 pts) than at the 90mg dose level (36.7%, 22/60). At target dose levels >90mg, ORRs in pts with prior exposure to CAR-Ts, BsAbs, ADCs, and anti-BCMA targeting agents were 44.4% (4/9 pts), 33.3% (3/9), 50.0% (7/14), and 36.4% (8/22) respectively. Median follow-up among all responders (n=61) was 8.1 months; estimated median duration of response was 15.6 months (95% CI: 6.4, 21.6). Conclusions: Cevostamab monotherapy continues to show clinically meaningful activity in a large cohort of pts with heavily pre-treated RRMM, with a target dose-dependent increase in ORR, but no increase in CRS rate. Responses appear durable, and are observed in pts with prior exposure to CAR-Ts, BsAbs, and ADCs. Compared with SS dosing, DS dosing at the 0.3/3.6mg level appears to be associated with a trend for an improved C1 safety profile. Figure 1 Figure 1. Disclosures Trudel: Amgen: Honoraria, Research Funding; GlaxoSmithKline: Consultancy, Honoraria, Research Funding; Roche: Consultancy; Genentech: Research Funding; Pfizer: Honoraria, Research Funding; BMS/Celgene: Consultancy, Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Sanofi: Honoraria. Cohen: BMS/Celgene: Consultancy; GlaxoSmithKline: Consultancy, Research Funding; Oncopeptides: Consultancy; Novartis: Research Funding; Genentech/Roche: Consultancy; AstraZeneca: Consultancy; Janssen: Consultancy; Takeda: Consultancy. 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. Fonseca: Kite: Consultancy; Juno: Consultancy; Merck: Consultancy; Sanofi: Consultancy; Pharmacyclics: Consultancy; Novartis: Consultancy; OncoTracker: Consultancy, Membership on an entity's Board of Directors or advisory committees; Aduro: Consultancy; Caris Life Sciences: Membership on an entity's Board of Directors or advisory committees; Patent: Prognosticaton of myeloma via FISH: Patents & Royalties; AbbVie: Consultancy; GSK: Consultancy; Scientific Advisory Board: Adaptive Biotechnologies: Membership on an entity's Board of Directors or advisory committees; Bayer: Consultancy; Amgen: Consultancy; Mayo Clinic in Arizona: Current Employment; Celgene: Consultancy; BMS: Consultancy; Takeda: Consultancy; Janssen: Consultancy. Spencer: Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees. Berdeja: Bluebird bio, BMS, Celgene, CRISPR Therapeutics, Janssen, Kite Pharma, Legend Biotech, SecuraBio, Takeda: Consultancy; Abbvie, Acetylon, Amgen: Research Funding; EMD Sorono, Genentech: Research Funding; Celularity, CRISPR Therapeutics: Research Funding; GSK, Ichnos Sciences, Incyte: Research Funding; Lilly, Novartis: Research Funding; Poseida, Sanofi, Teva: Research Funding. Lesokhin: Serametrix, Inc: Patents & Royalties; Behringer Ingelheim: Honoraria; Genetech: Research Funding; Iteos: Consultancy; Janssen: Honoraria, Research Funding; pfizer: Consultancy, Research Funding; bristol myers squibb: Research Funding; Trillium Therapeutics: Consultancy. Forsberg: University of Colorado: Current Employment; Karyopharm, Sanofi, Genentech: Research Funding. Costa: Karyopharm: Consultancy, Honoraria; BMS: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria, Speakers Bureau; Amgen: Consultancy, Honoraria, Research Funding, Speakers Bureau. Rodriguez-Otero: Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene-BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; GSK: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees; Kite: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria; Regeneron: Honoraria; Clínica Universidad de Navarra: Current Employment. Kaedbey: Takeda, Sanofi: Honoraria; Celgene/BMS, Janssen: Honoraria; Royal Victoria Hospital Lakeshore Hospital: Ended employment in the past 24 months; Jewish General Hospital - McGill University: Current Employment. Richter: Janssen, Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Adaptive biotechnologies: Speakers Bureau; BMS, Karyopharm, Antengene: Membership on an entity's Board of Directors or advisory committees; Tisch Cancer Institute: Icahn School of Medicine at Mount Sinai: Current Employment. Mateos: Takeda: 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; Regeneron: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: 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; Amgen: 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; Sea-Gen: 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; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Honoraria; Bluebird bio: Honoraria; GSK: Honoraria; Oncopeptides: Honoraria. Thomas: Pharmacyclics: Membership on an entity's Board of Directors or advisory committees; Genentech: Research Funding; Acerta Pharma: Research Funding; X4 Pharma: Research Funding; Ascentage Pharma: Research Funding; BeiGene: Membership on an entity's Board of Directors or advisory committees; BMS: Research Funding. Wong: Genentech: Current Employment; CTMX, UBX, BMRN: Current equity holder in publicly-traded company. Li: Genentech/Roche: Current Employment, Current equity holder in publicly-traded company. Choeurng: Genentech: Current Employment, Current equity holder in publicly-traded company. Vaze: Roche/Genentech: Current Employment, Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company. Samineni: Genentech: Current Employment, Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company. Sumiyoshi: Genentech: Current Employment, Current equity holder in publicly-traded company, Divested equity in a private or publicly-traded company in the past 24 months. Cooper: Genentech: Current Employment; Roche: Current holder of individual stocks in a privately-held company. Harrison: Haemalogix: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Roche/Genentech: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen Cilag: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene/ Juno/ BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; GSK: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Eusa: Consultancy, Honoraria, Speakers Bureau; Terumo BCT: Consultancy, Honoraria. OffLabel Disclosure: Cevostamab is a FcRH5xCD3 bispecific antibody that facilitates T cell-directed killing of myeloma cells. Cevostamab is an investigational agent.

8009 Background: Measuring response among patients with multiple myeloma is essential for the care of patients. Deeper responses have been associated with better progression free survival (PFS) and overall survival (OS). Serum (SIFE) and urine immunofixation are the currently used markers for biochemical documentation of CR after which marrow is tested for plasma cell clearance. Next generation flow cytometry and sequencing are used to document the presence of minimal residual disease (MRD). Mass spectrometry of blood by MALDI (Mass-Fix) is a new simple, inexpensive, sensitive, and specific means of detecting monoclonal immunoglobulins. To better test the hypothesis that Mass-Fix is superior to existing methodologies to predict for survival outcomes—especially SIFE-- samples from the STAMINA trial (NCT01109004), a trial comparing 3 transplant approaches among patients who have already received induction, were employed. Methods: Five-hundred and seventy-five patients were included. Samples from enrollment post-induction (post-I) and 1-year post enrollment (1YR) were tested when available. Four response parameters were assessed univariately: Mass-Fix, SIFE, complete response, and MRD by next generation flow cytometry. Mass spectrometry spectra were evaluated in a blinded fashion. Complete response was according to the 2006 International Myeloma Working Group criteria. Multivariate Cox proportional hazard models using stepwise regression were developed to explore the independent effect of the different response parameters on PFS and OS and interactions with other risk factors. Results: Of the 4 response measures, only MRD and Mass-Fix predicted for PFS and OS at multiple testing points on multivariate analyses (Table). Of the 4 post-I measurements, only MRD predicted for PFS; however, Mass-Fix was the only post-I measurement to predict for OS. Of all the 1-year measures, both 1YR Mass-Fix and 1YR MRD positivity predicted for inferior PFS and OS. In models including MRD and Mass-Fix, SIFE and CR were not prognostic for PFS or OS. Conclusions: Mass-Fix is a powerful means to track monoclonal proteins. The full utility of Mass-Fix was not exploited given the absence of a diagnostic sample and the fact that only serum (and not urine) was tested. Despite these limitations, it performed well at pre-induction and at 1 year. Mass-Fix provides a convenient and non-invasive means of predicting for myeloma outcomes. Clinical trial information: NCT01109004. [Table: see text]

Introduction: New targets and treatment modalities are needed for multiple myeloma (MM). Fc receptor-homolog 5 (FcRH5) is a type I membrane protein that is expressed on B cells and plasma cells, and is found on myeloma cells with near 100% prevalence. BFCR4350A, a humanized immunoglobulin G-based T-cell-engaging bispecific antibody (bsAb), targets the most membrane-proximal domain of FcRH5 on myeloma cells and CD3 on T cells. Dual binding facilitates efficient immunological synapse formation, resulting in T-cell activation and potent killing of myeloma cells (Li et al. Cancer Cell 2017). GO39775 (NCT03275103) is an ongoing, multicenter Phase I trial evaluating the safety, activity, pharmacodynamics, and pharmacokinetics of BFCR4350A monotherapy in pts with relapsed/refractory (R/R) MM. We present dose-escalation data from the single step-up dosing cohort (Arm A). Methods: All pts have R/R MM for which no established therapy is available, appropriate, or tolerated. Prior exposure to CAR-T cells, T-cell engaging bsAbs, and antibody-drug conjugates (ADCs), including those targeting BCMA, is allowed. In dose-escalation, pts receive BFCR4350A by IV infusion in 21-day cycles (Q3W). In Arm A, a single step-up dose is used in Cycle (C) 1 to mitigate the risk for cytokine release syndrome (CRS), with the step dose (0.05-3.6mg) given on C1 Day (D) 1 and the target dose (0.15-132mg) given on C1D8, and on D1 of each subsequent cycle. Results: At cut-off (April 13, 2020), 51 pts (median age: 62.0 years [range: 33-80]; high-risk [HR] cytogenetics [1q21, t(4;14), t(14;16), or del(17p)]: 28 pts) had been enrolled into Arm A. Median number of prior lines of therapy was 6 (range: 2-15). Prior treatments included: proteasome inhibitors (PIs), 100% (94.1% refractory); immunomodulatory drugs (IMiDs), 100% (98.0% refractory); anti-CD38 mAbs, 78.4% (92.5% refractory); autologous stem cell transplant, 86.3%. Overall, 66.7% of pts were triple-class refractory (≥1 PI, ≥1 IMiD, and ≥1 anti-CD38 mAb), and 94.1% of pts were refractory to their last therapy. At cut-off, 46/51 pts were evaluable for efficacy. Responses were observed at the 3.6/20mg dose level and above, in 15/29 pts (51.7%) (Table). Responses included 3 stringent CRs, 3 CRs, 4 VGPRs, and 5 PRs (Table). At the 3.6/20mg dose level and above, responses were observed in pts with HR cytogenetics (9/17), triple-class refractory disease (10/20), and prior exposure to anti-CD38 mAbs (11/22), CAR-Ts (2/3), or ADCs (2/2). Duration of response data are evolving, with 6/15 pts in response for >6 months at cut-off. Median follow-up for safety was 6.2 months (range: 0.2-26.3 months). Almost all pts (49/51) had ≥1 treatment-related AE. The most common treatment-related AE was CRS (Lee et al. 2014 criteria; 38/51 pts, 74.5%). CRS was Grade (Gr) 1 in 20 pts (39.2%), Gr 2 in 17 pts (33.3%), and Gr 3 in 1 pt (2%) (due to Gr 4 transaminase elevation). CRS was most common in C1 (38 pts) and was uncommon or absent in subsequent cycles (4 pts). Most CRS events (49/58, 84.5%) resolved within 2 days. 18/38 (47.3%) pts with CRS received tocilizumab and/or steroids. Other treatment-related AEs in ≥5 pts were neutropenia and lymphocyte count decreased (6 pts each, 11.8%), aspartate aminotransferase increased and platelet count decreased (5 pts each, 9.8%). Treatment-related Gr 3-4 AEs (20 pts, 39.2%) in ≥3 pts were lymphocyte count decreased (6 pts, 11.8%), neutropenia (5 pts, 9.8%), anemia and platelet count decreased (3 pts each, 5.9%). No treatment-related Gr 5 (fatal) AEs were observed. Treatment-related AEs leading to withdrawal of treatment were uncommon (1 pt, 2.0%). One DLT (Gr 3 pneumonia) was observed in the 3.6/90mg cohort, but the MTD was not reached. BFCR4350A PK was linear across the active dose levels tested and the estimated half-life was supportive of the Q3W dosing regimen. Conclusions: BFCR4350A monotherapy demonstrates promising activity in heavily pre-treated R/R MM, with deep and durable responses observed in pts with HR cytogenetics, triple-class refractory disease, and/or prior exposure to anti-CD38 mAbs, CAR-Ts, or ADCs. Toxicity was manageable, with C1 single step-up dosing effectively mitigating the risk for severe CRS and allowing escalation to clinically active doses. Updated data will be presented. Disclosures Cohen: Novartis: Other: Patents/Intellectual property licensed, Research Funding; Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees; Takeda,: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; GlaxoSmithKline: Membership on an entity's Board of Directors or advisory committees; Kite Pharma: Membership on an entity's Board of Directors or advisory committees; Oncopeptides: Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Membership on an entity's Board of Directors or advisory committees; Genentech/Roche: Membership on an entity's Board of Directors or advisory committees. Harrison:Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; GSK: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; F. Hoffmann-La Roche: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Patents & Royalties: wrt panobinostat; BMS: Consultancy, Honoraria; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Haemalogix: Consultancy; Janssen: Honoraria; CRISPR Therapeutics: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen-Cilag: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Krishnan:Sutro: Membership on an entity's Board of Directors or advisory committees; Z Predicta: Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy; Regeneron: Consultancy; Takeda: Speakers Bureau; Amgen: Speakers Bureau; BMS/Celgene: Consultancy, Other: Stock BMS, Speakers Bureau; Sanofi: Consultancy. Fonseca:Amgen: Consultancy; BMS: Consultancy; Celgene: Consultancy; Takeda: Consultancy; Bayer: Consultancy; Janssen: Consultancy; Novartis: Consultancy; Pharmacyclics: Consultancy; Sanofi: Consultancy; Merck: Consultancy; Juno: Consultancy; Kite: Consultancy; Aduro: Consultancy; OncoTracker: Consultancy, Membership on an entity's Board of Directors or advisory committees; Oncopeptides: Consultancy; GSK: Consultancy; AbbVie: Consultancy; Adaptive Biotechnologies: Membership on an entity's Board of Directors or advisory committees. Forsberg:Celgene: Speakers Bureau; Genentech, Inc., Sanofi, Karyopharm, Abbvie: Research Funding. Spencer:AbbVie, Celgene, Haemalogix, Janssen, Sanofi, SecuraBio, Specialised Therapeutics Australia, Servier and Takeda: Consultancy; Amgen, Celgene, Haemalogix, Janssen, Servier and Takeda: Research Funding; AbbVie, Amgen, Celgene, Haemalogix, Janssen, Sanofi, SecuraBio, Specialised Therapeutics Australia, Servier and Takeda: Honoraria; Celgene, Janssen and Takeda: Speakers Bureau. Berdeja:BMS: Consultancy, Research Funding; Glenmark: Research Funding; Genentech, Inc.: Research Funding; Bioclinica: Consultancy; Teva: Research Funding; Vivolux: Research Funding; Abbvie: Research Funding; Cellularity: Research Funding; Acetylon: Research Funding; CURIS: Research Funding; Legend: Consultancy; Lilly: Research Funding; Constellation: Research Funding; EMD Sorono: Research Funding; Celgene: Consultancy, Research Funding; Novartis: Research Funding; Janssen: Consultancy, Research Funding; Prothena: Consultancy; Poseida: Research Funding; Amgen: Consultancy, Research Funding; Servier: Consultancy; Takeda: Consultancy, Research Funding; Bluebird: Research Funding; Karyopharm: Consultancy; Kite Pharma: Consultancy; CRISPR Therapeutics: Consultancy, Research Funding; Kesios: Research Funding. Li:Genentech, Inc./ F. Hoffmann-La Roche: Current Employment. Choeurng:Genentech, Inc.: Current Employment, Current equity holder in publicly-traded company. Vaze:Genentech, Inc./ F. Hoffmann-La Roche: Current Employment, Current equity holder in publicly-traded company. Samineni:Genentech, Inc.: Current Employment, Current equity holder in publicly-traded company. Sumiyoshi:Genentech, Inc.: Current Employment, Current equity holder in publicly-traded company, Divested equity in a private or publicly-traded company in the past 24 months. Cooper:Genentech, Inc./ F. Hoffmann-La Roche: Current Employment, Current equity holder in publicly-traded company. Fine:Genentech, Inc.: Current Employment; F. Hoffmann-La Roche: Current equity holder in publicly-traded company. Trudel:Janssen: Honoraria, Research Funding; Sanofi: Honoraria; GSK: Consultancy, Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Karyopharm: Honoraria; AstraZeneca: Honoraria; BMS: Consultancy, Honoraria, Research Funding; Genentech, Inc.: Research Funding; Amgen: Consultancy, Research Funding; Takeda: Honoraria. OffLabel Disclosure: BFCR4350A is a humanized IgG-based T-cell-engaging bispecific antibody that targets the most membrane-proximal domain of FcRH5 on myeloma cells and CD3 on T cells. Dual binding facilitates efficient immunological synapse formation, resulting in T-cell activation and killing of myeloma cells. BFCR4350A is an investigational agent.

Outcomes in multiple myeloma (MM) have improved dramatically in the last two decades with the advent of novel therapies including immunomodulatory agents (IMiDs), proteasome inhibitors and monoclonal antibodies. In recent years, immunotherapy for the treatment of MM has advanced rapidly, with the approval of new targeted agents and monoclonal antibodies directed against myeloma cell-surface antigens, as well as maturing data from late stage trials of chimeric antigen receptor (CAR) T cells. Therapies that engage the immune system to treat myeloma offer significant clinical benefits with durable responses and manageable toxicity profiles, however, the appropriate use of these immunotherapy agents can present unique challenges for practicing physicians. Therefore, the Society for Immunotherapy of Cancer convened an expert panel, which met to consider the current role of approved and emerging immunotherapy agents in MM and provide guidance to the oncology community by developing consensus recommendations. As immunotherapy evolves as a therapeutic option for the treatment of MM, these guidelines will be updated.

TPS8551 Background: Multiple myeloma (MM) remains an incurable disease, with estimated median survival of 8–9 months in patients with relapsed or refractory (R/R) disease (Kumar et al. 2014; Usmani et al. 2016). There is no uniform standard of care for R/R MM, and combinations used in later lines have diminishing responses, especially after re-exposure to previously received classes of therapy (Gandhi et al. 2019). New targets and treatment modalities are needed. Fragment crystallizable receptor-like 5 (FcRH5) is expressed on myeloma cells across lines of therapy, and is overexpressed by myeloma cells with 1q21 gain; expression in healthy tissue is restricted to the B-cell lineage, and is retained in plasma cells (Li et al. 2017). BFCR4350A is an IgG-based T-cell-dependent bispecific antibody that was specifically engineered to target the most membrane-proximal domain of FcRH5 on myeloma cells and cluster of differentiation 3 (CD3) on T cells, with dual binding resulting in efficient immune synapse formation and T-cell killing of myeloma cells. BFCR4350A demonstrates potent killing of plasma cells and patient-derived myeloma cells (including those with low levels of FcRH5 expression) in vitro, and complete depletion of bone marrow plasma cells in primates, without severe or prolonged cytokine release (Li et al. 2017). GO39775 (NCT03275103) is an open-label, multicenter Phase I dose-escalation and dose-expansion trial evaluating the safety, pharmacokinetics (PK), and activity of BFCR4350A monotherapy in patients with R/R MM. Methods: Patients must be aged ≥18 years and must have R/R MM for which no established therapies are available or appropriate, or be intolerant to those therapies. Patients with prior CAR-T therapy and/or prior BCMA-directed therapy are not excluded. BFCR4350A is administered by intravenous infusion, and q3w dosing with Cycle 1 single-step or multi-step dosing is being investigated in dose-escalation (Arms A and B, respectively). Enrolment into both arms is ongoing, with patients receiving up to 17 cycles of treatment until disease progression or unacceptable toxicity. Primary objectives are to evaluate safety (including the maximum tolerated dose and dose-limiting toxicities) and to identify a recommended Phase II dose. Secondary objectives include assessment of PK, activity, immunogenicity, and pharmacodynamic biomarkers. Clinical trial information: NCT03275103 .

TPS8057 Background: Multiple myeloma (MM) is the second most prevalent blood cancer, representing approximately 1% of all cancers. Although overall survival has improved in recent years due to new approved agents, the vast majority of MM patients (pts) ultimately stop responding to treatment. Moreover, about a quarter of MM pts characterized as “high risk” experience limited benefit from existing treatments. Seminal genomic sequencing research efforts, such as the MMRF CoMMpass study, have highlighted that a large number of MM cases harbor potentially actionable oncogenic molecular alterations and published reports on small numbers of cases suggest that Precision Medicine (PM) interventions clinically targeting such actionable drivers may benefit MM pts. These results suggest that PM approaches in MM are possible and should be further studied clinically. To that end, we have launched MyDRUG, a master protocol aimed at developing new myeloma regimens based on individual pt’s genomics. Methods: This study is a Phase I-II, multicenter master protocol in functional high risk MM patients (i.e patients having progressed from baseline treatment within 18 months without maintenance or 3 years on maintenance) with 1-3 prior lines of therapy. Patients are screened for actionable genomic alterations on the CLIA-grade MI-ONCOSEQ platform. Patients with actionable alterations are assigned to the appropriate targeted agent used in combination with a backbone regimen ixazomib, pomalidomide and dexamethasone (IPd), whereas patients without such alterations go on an immune arm (see Table). Inclusion criteria include measurable disease (as measured by M-protein and FLC) and acceptable hematologic and metabolic functions. A maximum of 12 evaluable pts will be accrued onto the phase I portion of each arm and an additional 21 evaluable phase II pts will be accrued onto each arm for a total of 27 evaluable pts at the MTD combination dose. The primary objective of the study is to evaluate ORR per IMWG consensus criteria. Secondary objectives are to assess adverse events (AEs), progression-free survival, and overall survival (OS). Experimental correlative aims include assessing molecular or clonal response, molecular and immune signatures of resistance/response, MRD. Clinical trial information: NCT03732703. [Table: see text]