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292 Initial Clinical Activity and Safety of BFCR4350A, a FcRH5/CD3 T-Cell-Engaging Bispecific Antibody, in Relapsed/Refractory Multiple MyelomaClinically Relevant Abstract

Program: Oral and Poster Abstracts
Type: Oral
Session: 653. Myeloma/Amyloidosis: Therapy, excluding Transplantation: Bispecific T Cell Engager Therapies and Novel Targeting Agents
Hematology Disease Topics & Pathways:
multiple myeloma, Biological, antibodies, Diseases, Therapies, Plasma Cell Disorders, immunotherapy, Lymphoid Malignancies
Saturday, December 5, 2020: 2:30 PM

Adam D. Cohen, MD1, Simon J Harrison, MBBS MRCP (UK) PhD FRCPath (UK) FRACP2, Amrita Krishnan, MD3, Rafael Fonseca, MD4, Peter A Forsberg, MD5, Andrew Spencer6, Jesus G. Berdeja, MD7, Jacob P. Laubach, MD8, Mengsong Li9*, Voleak Choeurng9*, Anjali Vaze9*, Divya Samineni9*, Teiko Sumiyoshi9*, James Cooper9*, Bernard M Fine9* and Suzanne Trudel10

1University of Pennsylvania, Abramson Cancer Center, Philadelphia, PA
2Peter MacCallum Cancer Centre and Royal Melbourne Hospital, Melbourne, Australia
3City of Hope, Duarte, CA
4Mayo Clinic in Arizona, Phoenix, AZ
5University of Colorado School of Medicine, Aurora, CO
6Department of Clinical Haematology, Alfred Hospital, Melbourne, VIC, Australia
7Sarah Cannon Research Institute, Nashville, TN
8Dana-Farber Cancer Institute, Boston, MA
9Genentech, Inc., South San Francisco, CA
10Princess Margaret Cancer Centre and University of Toronto, Toronto, ON, Canada

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: Prothena: Consultancy; Genentech, Inc.: Research Funding; CURIS: Research Funding; EMD Sorono: Research Funding; Lilly: Research Funding; Amgen: Consultancy, Research Funding; Kesios: Research Funding; Cellularity: Research Funding; Glenmark: Research Funding; Teva: Research Funding; Legend: Consultancy; Celgene: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Karyopharm: Consultancy; Servier: Consultancy; Kite Pharma: Consultancy; Bioclinica: Consultancy; Acetylon: Research Funding; Bluebird: Research Funding; Takeda: Consultancy, Research Funding; Abbvie: Research Funding; Vivolux: Research Funding; Novartis: Research Funding; Poseida: Research Funding; Janssen: Consultancy, Research Funding; CRISPR Therapeutics: Consultancy, Research Funding; Constellation: 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.

*signifies non-member of ASH