On December 5, 2020 Regeneron Pharmaceuticals, Inc. (NASDAQ: REGN) reported updated data for REGN5458, a BCMAxCD3 bispecific antibody, from the Phase 1 portion of a Phase 1/2 trial in patients with relapsed or refractory (R/R) multiple myeloma. The results were shared in an oral presentation at the virtual 2020 American Society of Hematology (ASH) (Free ASH Whitepaper) Annual Meeting. BCMA (B-cell maturation antigen) is a protein that is typically over-expressed on multiple myeloma cells. REGN5458 is designed to bind to BCMA on multiple myeloma cells and the CD3 receptor on T-cells in order to bridge them together and activate T-cells to kill the cancer cells.

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"REGN5458 continues to show early, deep and durable anti-tumor responses in patients with relapsed and refractory multiple myeloma across all dose levels. This is particularly encouraging given that a majority of patients were heavily pretreated and had few options remaining. All patients were triple-refractory, with 57% being penta-refractory," said Deepu Madduri, M.D., Assistant Professor of Medicine at the Icahn School of Medicine at Mount Sinai in New York and a trial investigator. "As these data continue to mature, we look forward to assessing whether responses will further deepen and remain durable with ongoing REGN5458 treatment."

In the trial, the 49 patients evaluated had a median of five prior lines of therapy (range: 2-17) with 100% being triple-refractory and 57% being penta-refractory; all patients were refractory to anti-CD38 therapy. With a median follow up of 2.6 months (range: 1-13), responses generally occurred by week 4 and deepened over time. Exploratory analyses suggest that patient-reported global health status/quality of life (per EORTC QLQ-C30) also improved meaningfully at week 4 and was maintained through week 24, with assessment ongoing.

*As of data cut-off, dose level 6 patients had been followed for a median of 2 months, and responses may deepen over time.

Among all patients who responded to treatment (n=19) as of data cut-off:

95% (n=18) achieved a VGPR or better
42% (n=8) had a CR or sCR
57% of evaluable patients (4 of 7 patients) were minimal residual disease (MRD) negative
Tumor response was not correlated with BCMA expression as assessed by immunohistochemistry
In assessing durability among patients who responded to treatment and with data continuing to mature at the time of analysis:

Among responding patients with ≥6 months of follow-up, 83% (10 of 12 patients) have ongoing responses for up to 13 months at the time of analysis
74% of responders (n=14) remain on treatment
The observed median duration of response was 6 months (range: 1-13)
The most common adverse events (AEs) were cytokine release syndrome (CRS; 39%; n=19), anemia (37%; n=18), fatigue (35%; n=17), nausea (31%; n=15), pyrexia (31%; n=15) and back pain (27%; n=13). Grade ≥3 AEs occurred in 69% (n=34) of patients with the most common being anemia (22%; n=11), neutropenia (14%; n=7) and lymphopenia (12%; n=6). There were no reports of Grade ≥3 CRS or neurotoxicity. Dose-limiting toxicity was reported in 2 patients with 1 patient experiencing acute kidney injury and 1 patient experiencing elevated alanine aminotransferase (ALT)/raised aspartate aminotransferase (AST). Both cases were resolved with supportive care, and the patient that experienced elevated ALT/AST remains on REGN5458 and has since achieved a VGPR.

"REGN5458 is the second CD3 bispecific in our oncology portfolio to show clinically meaningful results. Alongside our CD20xCD3 bispecific odronextamab, REGN5458 offers additional evidence to support the potential of our bispecific platform to transform the treatment of diverse blood cancers for patients," said L. Andres Sirulnik, M.D., Ph.D., Senior Vice President, Translational & Clinical Sciences, Hematology at Regeneron. "Regeneron continues to drive increasing momentum across our oncology and non-oncology hematology programs. We are currently enrolling patients in a potentially registrational Phase 2 portion of this REGN5458 trial. We are also expanding our odronextamab program with multiple pivotal trials in 2021."

In addition to the REGN5458 data, updated results from the Phase 1 odronextamab trial in R/R follicular lymphoma, diffuse large B-cell lymphoma and other B-cell non-Hodgkin lymphomas will also be shared in an oral presentation (Abstract 400) at ASH (Free ASH Whitepaper) and will include patient follow-up data of up to 3 years.

REGN5458 and odronextamab were invented using Regeneron’s proprietary VelocImmune technology and created using the company’s Veloci-Bi platform. These allow for the creation of bispecific antibodies that closely resemble natural human antibodies with no linkers or artificial sequences. Additionally, Regeneron bispecifics are manufactured using similar approaches used for human monoclonal antibody medicines, yielding similar properties and pharmacokinetics.

REGN5458 and odronextamab are currently under clinical development, and their safety and efficacy have not been evaluated by any regulatory authority.

About the Phase 1/2 Dose-escalation Trial
REGN5458 monotherapy is being investigated in an open-label, Phase 1/2 dose-escalation trial in patients with R/R multiple myeloma who are at least triple refractory to existing therapeutic options, including proteasome inhibitors, immunomodulatory drugs and CD38 antibody treatments. The Phase 1 portion of the trial is primarily assessing safety, tolerability, and dose-limiting toxicities of REGN5458, with efficacy as secondary endpoints. The Phase 2 portion is currently enrolling patients and will further assess REGN5458 anti-tumor activity and safety.

Among the patients being enrolled are those with heavily pre-treated, triple refractory and penta-exposed multiple myeloma, including those with extra-medullary (outside of the bone marrow) and non-secretory (do not secrete detectable myeloma proteins) disease.

About Multiple Myeloma
Multiple myeloma is the second most common blood cancer with approximately 30,192 and 168,765 new diagnoses in the U.S. and the world, respectively, in 2020. It is characterized by the proliferation of cancerous plasma cells (multiple myeloma cells) that crowd out healthy blood cells in the bone marrow, infiltrate other tissues and cause potentially life-threatening organ injury. Multiple myeloma is not curable despite treatment advances. While current treatments are able to slow progression of the cancer, most patients will ultimately experience cancer progression and require additional therapies.