Citations

Summary: The multiple myeloma treatment landscape has changed dramatically. This change, paralleled by an increase in scientific knowledge, has resulted in significant improvement in survival. However, heterogeneity remains in clinical outcomes, with a proportion of patients not benefiting from current approaches and continuing to have a poor prognosis. A significant proportion of the variability in outcome can be predicted on the basis of clinical and biochemical parameters and tumor-acquired genetic variants, allowing for risk stratification and a more personalized approach to therapy. This article discusses the principles that can enable the rational and effective development of therapeutic approaches for high-risk multiple myeloma.

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.

Abstract Background: Ciltacabtagene autoleucel (cilta-cel) is a novel chimeric antigen receptor T-cell therapy that is being evaluated in the CARTITUDE-1 trial (NCT03548207) in patients with relapsed or refractory multiple myeloma (RRMM) who are triple-class exposed (to immunomodulatory drugs, proteasome inhibitors, and an anti-CD38 monoclonal antibody). As there is no clear standard of care for this patient population, and due to an absence of direct head-to-head trials evaluating cilta-cel and other relevant treatments, indirect treatment comparisons (ITCs) between cilta-cel and treatments used in current clinical practice, ie, physician's choice of treatment (PCT), have been previously conducted. Meta-analyses were performed to derive single summary effect estimates for overall survival (OS) and progression-free survival (PFS) by pooling ITCs evaluating cilta-cel versus PCT in patients with triple-class exposed RRMM. Methods: ITCs examining the comparative effectiveness of cilta-cel versus PCT on OS and PFS were included. Data on cilta-cel corresponded to the February 2021 data-cut for CARTITUDE-1. Data on PCT was leveraged from the following sources: (i) the Flatiron database, a primarily US community-based multiple myeloma registry, (ii) the long-term follow-up results of three global RRMM daratumumab randomized clinical trials (POLLUX [NCT02076009], CASTOR [NCT02136134], and EQUULEUS [NCT01998971]), (iii) the US-based retrospective MAMMOTH study, and (iv) a representative German patient registry maintained by OncologyInformationService (OIs). In each ITC, the PCT group was comprised of patients who satisfied key eligibility criteria for CARTITUDE-1 and was made comparable to CARTITUDE-1 using inverse probability of treatment weighting. Hence, the ITCs were deemed appropriate to meta-analyze. The meta-analyses used a robust variance estimator to account for the use of CARTITUDE-1 in each pairwise ITC. The main meta-analyses considered all participants treated with cilta-cel in CARTITUDE-1 compared with PCT. Sensitivity analyses considered ITC effect estimates based on all enrolled participants in CARTITUDE-1. Pooled summary effect estimates were presented as hazard ratios (HRs) with the corresponding 95% confidence intervals (CIs). Results: Based on availability of data, the main meta-analyses included four ITCs for OS and three ITCs for PFS. Cilta-cel was associated with a statistically significant improvement in OS (HR: 0.21, 95% CI: 0.13 to 0.34; Figure 1) and PFS (HR: 0.20, 95% CI: 0.07 to 0.63; Figure 2) compared to PCT. Sensitivity analyses including all enrolled participants confirmed the results of the main meta-analyses. Conclusions: In the meta-analyses, cilta-cel demonstrated a significant advantage over PCT in terms of OS and PFS, highlighting its potential as an effective therapy in patients with triple-class exposed RRMM. Figure 1 Figure 1. Disclosures Hari: GSK: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding, Speakers Bureau; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding, Speakers Bureau; Celgene-BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding, Speakers Bureau; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding, Speakers Bureau; Karyopharm: Consultancy; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Oncopeptides: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding, Speakers Bureau; Adaptive Biotech: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Millenium: Membership on an entity's Board of Directors or advisory committees, Research Funding. Berdeja: EMD Sorono, Genentech: Research Funding; Celularity, CRISPR Therapeutics: Research Funding; Bluebird bio, BMS, Celgene, CRISPR Therapeutics, Janssen, Kite Pharma, Legend Biotech, SecuraBio, Takeda: Consultancy; Abbvie, Acetylon, Amgen: Research Funding; GSK, Ichnos Sciences, Incyte: Research Funding; Lilly, Novartis: Research Funding; Poseida, Sanofi, Teva: Research Funding. Gay: Bluebird Bio: Membership on an entity's Board of Directors or advisory committees; Oncopeptides: Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees; GlaxoSmithKline: Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Honoraria; Takeda: 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; Celgene: 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: Consultancy, Honoraria. Hooper: Eversana: Current Employment; Janssen: Consultancy. Haltner: Eversana: Current Employment; Janssen: Consultancy. Kumar: Carsgen: Research Funding; Novartis: Research Funding; Merck: Research Funding; Bluebird Bio: Consultancy; Roche-Genentech: Consultancy, Research Funding; Oncopeptides: Consultancy; Astra-Zeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Antengene: Consultancy, Honoraria; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Beigene: Consultancy; KITE: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Tenebio: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Adaptive: Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Research Funding; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Consultancy, Research Funding; Sanofi: Research Funding. Martin: Sanofi: Research Funding; Janssen: Research Funding; GlaxoSmithKline: Consultancy; Amgen: Research Funding; Oncopeptides: Consultancy. Mateos: AbbVie: Honoraria; Oncopeptides: 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; Amgen: 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; Celgene - Bristol Myers Squibb: 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; Bluebird bio: Honoraria; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Oncopeptides: Honoraria; 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; GSK: Honoraria; Sanofi: 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. Moreau: Sanofi: Honoraria; Janssen: Honoraria; Celgene BMS: Honoraria; Oncopeptides: Honoraria; Amgen: Honoraria; Abbvie: Honoraria. Rosta: EVERSANA: Current Employment; Janssen Inc.: Consultancy. Samjoo: EVERSANA: Current Employment; Janssen Inc.: Consultancy. Usmani: GSK: Consultancy, Research Funding; Abbvie: Consultancy; Array BioPharma: Consultancy, Research Funding; Celgene/BMS: Consultancy, Research Funding, Speakers Bureau; EdoPharma: Consultancy; Seattle Genetics: Consultancy, Research Funding; Janssen Oncology: Consultancy, Research Funding; SkylineDX: Consultancy, Research Funding; Takeda: Consultancy, Research Funding, Speakers Bureau; Janssen: Consultancy, Research Funding, Speakers Bureau; Merck: Consultancy, Research Funding; Sanofi: Consultancy, Research Funding, Speakers Bureau; Pharmacyclics: Consultancy, Research Funding; Bristol-Myers Squibb: Research Funding; Amgen: Consultancy, Research Funding, Speakers Bureau. Weisel: Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: 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; Karyopharm: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol Myers Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria; Oncopeptides: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: 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, Research Funding; Abbvie: Consultancy; Novartis: Honoraria; Pfizer: Honoraria. Jackson: Janssen: Current Employment; Memorial Sloan Kettering Cancer Center: Consultancy. Olyslager: Janssen: Current Employment. Schecter: Janssen: Current Employment, Current holder of stock options in a privately-held company. Vogel: Janssen Global Services, LLC: Current Employment, Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company, Divested equity in a private or publicly-traded company in the past 24 months. Garrett: Legend Biotech USA: Current Employment. Lee: Legend Biotech: Current Employment, Current equity holder in publicly-traded company. Nesheiwat: Legend Biotech USA: Current Employment. Pacaud: Legend Biotech: Current Employment. Valluri: Janssen: Current Employment, Current equity holder in publicly-traded company. Costa: Amgen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Sanofi: Consultancy, Honoraria, Speakers Bureau; BMS: Consultancy, Honoraria, Research Funding; Karyopharm: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria. Lin: Merck: Research Funding; Bluebird Bio: Consultancy, Research Funding; Juno: Consultancy; Takeda: Research Funding; Legend: Consultancy; Sorrento: Consultancy; Gamida Cell: Consultancy; Vineti: Consultancy; Novartis: Consultancy; Celgene: Consultancy, Research Funding; Janssen: Consultancy, Research Funding; Kite, a Gilead Company: Consultancy, Research Funding.

Abstract BACKGROUND: Our group recently reported on the results of Blood and Marrow Transplant (BMT) Clinical Trials Network (CTN) 1101 a randomized comparison between double umbilical cord blood (dUCB) and haploidentical bone marrow (haplo) with post-transplant cyclophosphamide (ptCy) in the nonmyeloablative setting that showed similar progression free survival (PFS) between the two treatment groups, but lower non-relapse mortality (NRM) and better of overall survival (OS) in the haplo arm. In this secondary analysis we sought to investigate if transplant center experience with haplo and or cord blood HCT had an impact on outcomes. PATIENTS AND METHODS: All patient randomized in BMT CTN 1101 were included. In order to determine the transplant center experience with either haplo or dUCB we queried the Center for International Blood and Marrow Transplant Research (CIBMTR) for number of transplants with each platform in the year prior to initiation of the study. Centers were then grouped as dUCB center (> 10 dUCB, n=117, 10 centers), Haplo center (>10 haplo and ≤10 dUCB, n=110, 2 centers), and ≤10 haplo and ≤10 dUCB HCTs (other center, n=140, 21 centers). Further analysis considered the alternative cut-off for haplo (> 5 vs ≤ 5) experience, and considered the outcomes based on the donor experience vs. others (e.g. dUCB > 10 vs. ≤ 10; haplo > 5 vs. ≤ 5). RESULTS: The effect of center experience on HCT outcomes shown in Figure, below . After adjusting for age, Karnofsky performance score and, disease risk index we found that there was no difference in outcomes between haplo and dUCB for centers that were experienced with dUCB or had limited to no experience with either dUCB or haplo. In contrast, in centers that were primarily experienced with haplo had better outcomes with this donor type, as compared to dUCB. The higher risk of treatment failure (relapse or death) and overall mortality in dUCB in haplo experienced centers was driven by significantly higher risk of relapse. We then considered the transplant experience with each of the donor types separately. In transplant centers that had performed > 10 dUCB, there were similar outcomes for recipients of both dUCB and haplo. Similarly, centers that had ≤ 5 haplo HCTs had no difference in outcomes between donor types suggesting an overlap with centers that had performed > 10 dUCB HCTs. Overall mortality was higher among dUCB recipients in centers that had performed ≤ 10 dUCB. Notably, the hazard ratio of non-relapse mortality favored haplo in all four donor experience type of transplant center, albeit not statistically significant. CONCLUSION: Except for dUCB recipients in centers with < 10 dUCB/year had worse overall mortality, primarily driven by relapse, the transplant center experience in the year prior to the initiation of BMT CTN 1101 had limited impact on the outcomes of this randomized clinical trial. Figure 1 Figure 1. Disclosures Brunstein: NANT: Research Funding; FATE: Research Funding; GamidaCell: Research Funding; BlueRock: Research Funding; AlloVir: Consultancy. Costa: Amgen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Research Funding; Sanofi: Consultancy, Honoraria, Speakers Bureau; Pfizer: Consultancy, Honoraria; BMS: Consultancy, Honoraria, Research Funding; Karyopharm: Consultancy, Honoraria. Cutler: Deciphera: Consultancy; Cimeio: Consultancy; Editas: Consultancy; Kadmon: Consultancy; Pfizer: Consultancy; Mallinckrodt: Consultancy; CareDx: Consultancy; Incyte: Consultancy; Omeros: Consultancy; Syndax: Consultancy; Mesoblast: Consultancy; Jazz: Consultancy. Horowitz: Sobi: Research Funding; Regeneron: Research Funding; Orca Biosystems: Research Funding; Tscan: Research Funding; Xenikos: Research Funding; Miltenyi Biotech: Research Funding; Stemcyte: Research Funding; Medac: Research Funding; Vor Biopharma: Research Funding; Kite/Gilead: Research Funding; Janssen: Research Funding; Pharmacyclics: Research Funding; Kiadis: Research Funding; Seattle Genetics: Research Funding; Mesoblast: Research Funding; GlaxoSmithKline: Research Funding; Sanofi: Research Funding; Pfizer, Inc: Research Funding; Omeros: Research Funding; Magenta: Consultancy, Research Funding; Jazz Pharmaceuticals: Research Funding; Vertex: Research Funding; Genentech: Research Funding; Takeda: Research Funding; Novartis: Research Funding; Shire: Research Funding; Gamida Cell: Research Funding; Daiicho Sankyo: Research Funding; CSL Behring: Research Funding; Chimerix: Research Funding; Bristol-Myers Squibb: Research Funding; bluebird bio: Research Funding; Astellas: Research Funding; Amgen: Research Funding; Allovir: Consultancy; Actinium: Research Funding. Horwitz: Gamida Cell: Research Funding. McGuirk: Novartis: Research Funding; Magenta Therapeutics: Consultancy, Honoraria, Research Funding; EcoR1 Capital: Consultancy; Pluristem Therapeutics: Research Funding; Novartis: Research Funding; Bellicum Pharmaceuticals: Research Funding; Astelllas Pharma: Research Funding; Gamida Cell: Research Funding; Fresenius Biotech: Research Funding; Allovir: Consultancy, Honoraria, Research Funding; Juno Therapeutics: Consultancy, Honoraria, Research Funding; Kite/ Gilead: Consultancy, Honoraria, Other: travel accommodations, expense, Kite a Gilead company, Research Funding, Speakers Bureau. Rezvani: US Department of Justice: Consultancy; Kaleido: Other: One-time scientific advisory board; Nohla Therapeutics: Other: One-time scientific advisory board; Pharmacyclics-Abbvie: Research Funding. Rybka: Spark Therapeutics: Consultancy; Merck: Consultancy. Vasu: Kiadis, Inc.: Research Funding; Boehringer Ingelheim: Other: Travel support; Seattle Genetics: Other: travel support; Omeros, Inc.: Membership on an entity's Board of Directors or advisory committees.