2024 EHA | New Generation BCL-2 Inhibitor Sonrotoclax Expected to Be a New Treatment Option for RRMM

**2024 EHA | New Generation BCL-2 Inhibitor Sonrotoclax Expected to Be a New Treatment Option for RRMM**

RRMM

The 29th Annual Meeting of the European Hematology Association (EHA) was held from June 13-16, 2024, in Madrid, Spain. During this event, the results of the study on the new-generation BCL-2 inhibitor Sonrotoclax (BGB-11417) combined with dexamethasone for the treatment of relapsed/refractory multiple myeloma (RRMM) patients with t(11;14) were presented.

**Ib/II Phase Study of Sonrotoclax (BGB-11417) Combined with Dexamethasone for the Treatment of RRMM with t(11;14)**

The B-cell lymphoma-2 (BCL-2) protein helps multiple myeloma (MM) tumor cells evade apoptosis and promote cell survival. Studies have found that MM cells with t(11;14) have significantly higher BCL-2 protein expression compared to other cells. BCL-2 inhibitors can block anti-apoptotic mechanisms and induce cell apoptosis. Currently, data have shown that BCL-2 inhibitors have significant anti-MM potential in RRMM patients with t(11;14) who have failed multiple lines of treatment. However, to date, no BCL-2 targeted therapy has been approved for MM treatment.

Sonrotoclax (BGB-11417) is a new-generation BCL-2 inhibitor. Preclinical studies have found that it has over ten times the BCL-2 inhibitory ability of the first-generation BCL-2 inhibitors, a shorter half-life, and no dose accumulation. BGB-11417-105 (NCT04973605) is an ongoing Ib/II phase trial aimed at evaluating the efficacy and safety of Sonrotoclax combined with dexamethasone ± carfilzomib/daratumumab/pomalidomide in treating RRMM patients with t(11;14). The latest data from this study were reported at this EHA meeting.

The enrolled patients were all RRMM with t(11;14), who had failed at least three treatments, including proteasome inhibitors (PI), immunomodulatory drugs (IMIDs), and anti-CD38 monoclonal antibodies, and were refractory/relapsed to the most recent treatment. In the first part, dose escalation cohorts, patients took 80, 160, 320, or 640 mg of Sonrotoclax daily, combined with 40 mg of dexamethasone weekly until intolerance, disease progression, or death. The primary endpoints were safety/tolerability, determining the maximum tolerated dose (MTD)/maximum assessed dose (MAD), and recommending the dose for the expansion phase (RDFE). The second part, dose expansion, primarily evaluated the tolerability and antitumor activity of Sonrotoclax combined with dexamethasone ± carfilzomib/daratumumab/pomalidomide.

The initial report at 2023 ASH showed that Sonrotoclax (640 mg) was well tolerated, with no dose-limiting toxicities (DLTs) observed in any patients, establishing 640 mg as the RDFE. The overall response rate (ORR) for this cohort was 70%, and the rate of very good partial response (≥VGPR) was 40%.

Updated in this report: as of March 25, 2024, 32 patients received the RDFE dose of 640 mg Sonrotoclax combined with dexamethasone (10 in the first part and 22 in the second part). The median follow-up time was 4.6 months (0.1-19 months).

The median age of patients was 69 years (48-80 years), with a median of 3 prior lines of treatment (1-12 lines), and 28.1% had high-risk cytogenetic abnormalities. All patients had been exposed to PI and IMiD treatments, and 72% had been exposed to anti-CD38 monoclonal antibody treatments. 56% were PI-refractory, 72% were IMiD-refractory, 56% were anti-CD38 monoclonal antibody-refractory, and 47% were triple-refractory.

No patients experienced DLTs. The most common treatment-emergent adverse events (TEAEs) were fatigue and insomnia (28% each), diarrhea (22%), constipation, and nausea (16% each). Only 4 patients (13%) experienced hematologic TEAEs (grade 3 thrombocytopenia, grade 1 and 3 platelet count decrease, and grade 3 neutropenia). Two patients died, both unrelated to treatment (one due to pancreatic cancer complications and one due to liver cancer and liver failure).

Among the 24 evaluable patients, the ORR was 75%, with a ≥VGPR rate of 50%. The complete response (≥CR) rate was 21% (CR, n=4; sCR, n=1), with two patients achieving minimal residual disease (MRD) negativity (10^-5). The median time to response was 0.7 months, and the median duration of response (DOR) was 8 months. As of the follow-up, the longest DOR was 18 months.

Sonrotoclax (640 mg) combined with dexamethasone was well tolerated in heavily pretreated RRMM patients with t(11;14), with low rates of hematologic toxicity and infection. It provided deep and durable responses: ORR was 75%, ≥VGPR rate was 50%, and ≥CR rate was 21%. This study will continue to explore Sonrotoclax in combination with other novel agents.

The t(11;14) translocation is a common genetic abnormality in MM patients, present in approximately 15%-20% of newly diagnosed MM cases. Before the era of novel drugs, many researchers believed that patients with t(11;14) had favorable treatment outcomes and were classified as a standard-risk group. However, recent studies have found that patients with t(11;14) are less sensitive to bortezomib regimens, and even with the VRd regimen, patients with t(11;14) have significantly lower deep response rates (≥VGPR) and PFS benefits compared to other standard-risk patients. This suggests that t(11;14) may be an influencing factor for poor efficacy of novel drugs, necessitating other therapies to improve prognosis.

Studies have found that tumor cells with t(11;14) often have high BCL-2 expression and high sensitivity to BCL-2 inhibitors. The phase III CANOVA study demonstrated that venetoclax combined with dexamethasone resulted in deeper response rates (ORR 62% vs. 35%, p<0.001; ≥VGPR rate 39% vs. 14%, p<0.001) and longer median PFS (9.1 months vs. 4.9 months, p=0.237) compared to pomalidomide combined with dexamethasone in treating RRMM patients with t(11;14), though without significant statistical difference. The failure to meet the primary endpoint might be due to more patients in the control group not reaching IMWG-defined disease progression and thus being treated with new regimens, resulting in censored data in the initial PFS analysis. In the latest post-hoc analysis, including new treatment as an event in PFS, the analysis showed a significant statistical difference in median PFS (9.4 months vs. 4.0 months, p=0.003).

Therefore, the benefits of BCL-2 inhibitors still warrant further exploration. Sonrotoclax is a second-generation highly selective and potent BCL-2 inhibitor. In preclinical trials, Sonrotoclax had an IC50 for BCL-2 protein over ten times lower than that of the first-generation BCL-2 inhibitors (0.014 nM vs. 0.2 nM). It also showed ≥2000 times selectivity over BCL-XL, BCL-W, MCL-1, and BCL2A1 and stronger cytotoxicity against MM cell lines. Additionally, Sonrotoclax has a shorter half-life (approximately 4.5 hours), allowing more flexible exploration of rapid dose escalation plans without the risk of off-target toxicity due to drug accumulation.

The Ib/II phase study reported at this EHA meeting demonstrated that Sonrotoclax combined with dexamethasone was well tolerated in RRMM patients previously treated with multiple lines of therapy. The 640 mg RDFE dose achieved a 75% ORR, ≥VGPR rate of 50%, and ≥CR rate of 21%. We look forward to the release of more results from Sonrotoclax combination therapies. Additionally, as the proportion of t(11;14) in systemic light chain amyloidosis and plasma cell leukemia is higher than in MM, the exploration of BCL-2 inhibitors in these plasma cell diseases is also ongoing.

Chief Physician, Professor, Ph.D. Supervisor

Peking University People’s Hospital, Peking University Institute of Hematology

Specializes in clinical and laboratory research on multiple myeloma, primary systemic amyloidosis, lymphoma, and cellular immunotherapy.

General Secretary and Standing Committee Member of the Hematology Physician Branch of the Chinese Medical Doctor Association

President of the Hematology Physician Branch of the Beijing Medical Doctor Association

Vice Chairman of the Multiple Myeloma Professional Committee and the Histiocyte Disease Professional Committee of the Chinese Medical Doctor Association

Vice President of the Hematology Branch of the Chinese Society of Geriatrics and Chairman of the Multiple Myeloma Academic Committee

Deputy Leader of the Plasma Cell Group of the Hematology Branch of the Chinese Medical Association

Deputy Leader of the Multiple Myeloma and Related Diseases Professional Group of the Hematology Professional Committee of the Chinese Women Physicians Association

Member of the Chinese and International Primary Systemic Amyloidosis Collaboration Group

Member of the International Myeloma Working Group and the Asia-Pacific Myeloma Working Group