On April 7, 2024 Regeneron Pharmaceuticals, Inc. (NASDAQ: REGN) reported the oral plenary session presentation of positive pivotal data from the Phase 1/2 LINKER-MM1 trial of linvoseltamab in patients with relapsed/refractory (R/R) multiple myeloma (MM) at the American Association for Cancer Research (AACR) (Free AACR Whitepaper) Annual Meeting 2024 in San Diego (Press release, Regeneron, APR 7, 2024, View Source [SID1234641838]). Linvoseltamab is an investigational bispecific antibody designed to bridge B-cell maturation antigen (BCMA) on multiple myeloma cells with CD3-expressing T cells to facilitate T-cell activation and cancer-cell killing.

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"The presentation of these pivotal results in an oral plenary session at AACR (Free AACR Whitepaper) recognizes the exciting potential of linvoseltamab to advance the treatment of multiple myeloma," said Sundar Jagannath, M.D., Director of the Multiple Myeloma Center of Excellence at Tisch Cancer Center at Mount Sinai in New York City and a trial investigator. "In clinical trials, linvoseltamab treatment led to responses that occurred early, were durable and deepened over time – all critical efficacy measures for this heavily pre-treated patient population. Further, among patients who had at least 24 weeks of treatment, the majority achieved a very good partial response, enabling them to transition from every two-week to every four-week dosing. This is an important accomplishment that I’ve seen firsthand in my trial patients, and I eagerly anticipate the FDA decision expected this August."

With an 11-month median duration of follow up, the linvoseltamab data among 117 patients presented at AACR (Free AACR Whitepaper) reinforce the strength of previously shared findings and included a:

71% objective response rate (ORR), with 46% of patients achieving a complete response (CR) or better and 62% achieving a very good partial response (VGPR) or better, as determined by an independent review committee.
1-month median time to response (range: <1-6 months). In responders, the median time to a VGPR or better was 3 months (range: <1-13 months) and to a CR or better was 8 months (range: 2-14 months).
Median duration of response (DoR), median progression-free survival (PFS) and median overall survival (OS) were not reached. At 12 months, the estimated probability of maintaining a response was 78%, being progression free was 69% and survival was 75%.
Among patients who had a CR or better and were minimum residual disease (MRD) evaluable, 93% (25 of 27 patients) were MRD negative at 10-5.
The trial included a response-adapted regimen that enabled linvoseltamab patients to shift to every four-week dosing if they achieved a VGPR or better and completed at least 24 weeks of therapy. In the dose expansion portion of the trial (n=105), of the patients who had at least 24 weeks of therapy at data cutoff, 90% (56 of 62) achieved a VGPR or better and were able to transition to every four-week dosing. Of the 29 patients who transitioned to the extended dosing regimen prior to achieving a CR, 48% (14 of 29) subsequently experienced a deepening of response to CR or better.

In addition, high ORRs were observed across prespecified subgroups – including high-risk and high-disease burden populations – as follows:

85% among Black or African American patients (17 of 20 patients)
71% among those aged 75 years or older (22 of 31 patients)
67% among those with high cytogenetic risk (31 of 46 patients)
62% among those with International Staging System stage III disease (13 of 21 patients)
53% among those with extramedullary plasmacytomas (10 of 19 patients)
Cytokine release syndrome (CRS) was the most commonly occurring treatment-emergent adverse event (TEAE) and was observed in 46% of patients; 35% were Grade 1, 10% were Grade 2 and one case (1%) was Grade 3. Adjudicated immune effector cell-associated neurotoxicity syndrome (ICANS) events of any grade occurred in 8% of patients, including three cases that were Grade 3 and no cases that were ≥Grade 4. Infections occurred in 73% of patients, with their frequency and severity decreasing after 6 months; 34% were Grade 3 or 4. The most common Grade 3 or 4 TEAEs (≥20%) were neutropenia (40%) and anemia (31%). Six deaths occurred on treatment or within 30 days of the last treatment dose due to TEAEs; five were due to infection, and one was due to renal failure.

Linvoseltamab has been granted Fast Track Designation and was accepted for Priority Review for the treatment of R/R MM by the FDA, with a target action date of August 22, 2024. In addition, linvoseltamab is being reviewed by the EMA. Linvoseltamab is currently under clinical development, and its safety and efficacy have not been fully evaluated by any regulatory authority.

The Phase 3 confirmatory trial for linvoseltamab in patients with R/R MM (LINKER-MM3) is underway.

About Multiple Myeloma
As the second most common blood cancer, there are over 176,000 new cases of MM diagnosed globally, and 35,000 cases are diagnosed in the U.S. every year. In the U.S., there are approximately 8,000 people who have MM that has progressed after three lines of therapy, and 4,000 whose disease has progressed after four or more therapies. The disease is characterized by the proliferation of cancerous plasma cells (MM cells) that crowd out healthy blood cells in the bone marrow, infiltrate other tissues and cause potentially life-threatening organ injury. Despite treatment advances, MM is not curable and while current treatments are able to slow progression of the cancer, most patients will ultimately experience cancer progression and require additional therapies.

About the Linvoseltamab Phase 1/2 Trial and Clinical Development Program
The ongoing, open-label, multicenter Phase 1/2 dose-escalation and dose-expansion LINKER-MM1 trial is investigating linvoseltamab in 282 enrolled patients with relapsed/refractory MM. The Phase 1 dose-escalation portion of the trial – which is now complete – primarily assessed safety, tolerability and dose-limiting toxicities across nine dose levels of linvoseltamab and explored different administration regimens. The ongoing Phase 2 dose expansion portion is assessing the safety and anti-tumor activity of linvoseltamab, with the primary endpoint of ORR. Key secondary endpoints include DoR, PFS, rate of MRD negative status and OS.

Eligibility in the Phase 2 portion requires patients to have received at least three prior lines of therapy or have triple-class refractory MM. Linvoseltamab is administered with an initial step-up dosing regimen followed by the full 200 mg dose administered weekly. At week 16, all patients transition to every two-week dosing. A response-adapted regimen further enables patients to shift to every four-week dosing if they achieve a VGPR or better and have completed at least 24 weeks of therapy. The regimen requires a total of two 24-hour hospitalizations for safety monitoring.

The broader linvoseltamab clinical development program includes additional trials in earlier lines of therapy and stages of disease that are planned or underway. They include a Phase 1/2 trial in first-line MM, a Phase 2 trial in high-risk smoldering MM, and a Phase 2 trial in monoclonal gammopathy of undetermined significance. A Phase 1 trial of linvoseltamab in combination with a Regeneron CD38xCD28 costimulatory bispecific in MM is also planned. For more information, visit the Regeneron clinical trials website, or contact via [email protected] or 844-734-6643.