Bhutani, Manisha

Abstract Background B-cell maturation antigen (BCMA)-targeting immunotherapies represent a promising class of treatment for the management of immunoglobulin light chain (AL) amyloidosis, a disease that is related to clonal plasma cells. Etentamig is a 2nd generation, off-the-shelf, fully human BMCA X CD3 bispecific antibody with bivalent BCMA domain and low CD3 affinity that targets both BCMA-expressing plasma cells and CD3-expressing T cells. Etentamig monotherapy is being studied in multiple myeloma (MM) in an ongoing phase 3 study (NCT06158841). Here, we report the first safety and efficacy results from M24-209, an open-label phase 1/2 study evaluating etentamig monotherapy in patients (pts) with relapsed/refractory (RR) AL amyloidosis from dose level 1 (DL1). Methods The phase 1 dose escalation (ESC) portion of the study (NCT06158854) with etentamig enrolled pts with RR AL amyloidosis with ≥1 prior lines of therapy (LOT), including a proteasome inhibitor and an anti-CD38 monoclonal antibody with no prior BCMA exposure. Eligible pts were required to have a difference in involved and uninvolved serum free light chain (dFLC) of ≥50 mg/L, and pts with Mayo Clinic 2004 cardiac risk stage IIIb with NT-proBNP ≥8500 pg/ml were excluded. Three dose groups were explored in dose ESC (etentamig dose levels [DL] 1, 2, and 3). In all cohorts, pts will receive up to 24 cycles of treatment and will be followed until disease progression. In dose ESC, the primary objectives are to determine safety/tolerability, pharmacokinetic/pharmacodynamic, and recommended phase 2 dose. The secondary objectives include evaluation of efficacy as measured by hematologic response and organ response. Responses are investigator assessed per consensus guidelines (Comenzo, et al. Leukemia. 2012. 26[11]:2317-25; Palladini G, et al. Amyloid. 2021 [Epub];28[1]:1-2). Results As of 17 July 2025, all DLs in dose ESC have been fully enrolled, and 12 pts have been treated with etentamig at DL1. Due to short follow-up, this initial report only includes data from DL1, with further follow-up data from ESC to be included at the time of presentation. Median duration of follow up in DL1 was 9.4 months (8.3–13.8) with 83% of pts continuing treatment. Median age for pts was 72 years (range, 56–85 years). Median number of prior LOT was 2 (range, 1–6), and median time from initial diagnosis was 3.6 years. Thirty-three percent have received a prior stem cell transplant and 50% previously received the regimen of daratumumab with cyclophosphamide, bortezomib, and dexamethasone in combination. Median dFLC at study baseline was 110. 5 mg/L (range, 56.6–617.5). At baseline, 83% of pts had cardiac involvement, 25% had renal involvement, and 8% had hepatic involvement. Eighty-three percent of pts had lambda AL amyloidosis. Treatment-emergent adverse events were reported in 100% (42% Grade ≥3) of pts at DL1. Cytokine release syndrome (CRS) occurred in 2 pts (17%, all Grade 1), with no instances of any grade immune effector cell-associated neurotoxicity syndrome (ICANS). CRS occurring after the first dose had median time to onset of 6.8 hours (range, 6.7–6.9). Grade ≥3 infections occurred in 1 pt (8%, all Grade 3). Grade ≥3 neutropenia also occurred in 1 pt (8%, all Grade 3), and no Grade ≥3 events of thrombocytopenia or anemia occurred. No Grade 5 events have occurred. Within the dose ESC DL1 cohort, the overall hematologic response rate was 100%, with all pts achieving ≥VGPR and 83% of pts achieving complete response (CR). The median time to CR was 0.9 months (0.3–9.3). The median duration of response has not yet been reached and 100% of pts remain in their best overall response by investigator assessment. To date, no pts have experienced hematologic progression on study. Cardiac response was observed in 30% of evaluable pts. Renal response was seen in 67% of evaluable pts. Conclusions In the DL1 cohort, etentamig showed a manageable safety profile in AL amyloidosis with low incidence and severity of CRS, no ICANS, and limited Grade ≥3 cytopenia events. Deep and rapid hematologic responses were observed with 100% ≥VGPR rate and 83% hematologic CR rate. Additional dose-level data will be presented at the time of the meeting. All pts remain in ongoing follow-up and evaluation, and the study will begin the dose expansion (EXP) portion after dose selection.

Introduction: Systemic amyloid light chain (AL) amyloidosis is a rare disease with severe sequelae, including cardiac and renal dysfunction and failure. Various biomarker-based staging systems have been established to inform prognosis and treatment. However, a single International Classification of Diseases, Tenth Revision (ICD-10) diagnosis code collectively applies to all stages of the disease, and while several studies have reported disease costs using healthcare claims data, stage-specific costs are not well understood. The current study aimed to estimate the healthcare utilization and costs of prevalent patients with AL amyloidosis by Mayo 2012 stage (I, II, III, IV). Methods: A multi-center medical chart review of patients with AL amyloidosis was conducted across six hematology clinics in the United States. Enrolled patients were ≥18 years old with a diagnosis of AL amyloidosis, documentation of Mayo 2012 stage at diagnosis, ≥1 office visit during the 6 months prior to the site's IRB approval date, and ≥1 year of available medical records. We collected 1 year of healthcare utilization data for each patient, in addition to clinical characteristics at diagnosis, which was prior to the 1-year observation period for most patients. Observation periods ranged from 11/2020 to 6/2023. Demographics, AL amyloidosis clinical history (e.g., organ involvement, lines of therapy, treatment response), laboratory values, and AL amyloidosis-related healthcare utilization (e.g., office visits, laboratory tests, procedures, medications, emergency department visits, inpatient stays) were collected. Patients were stratified by Mayo 2012 stage at diagnosis. Patients' 1-year healthcare costs were calculated by combining abstracted utilization data with the Centers for Medicare and Medicaid Services 2023 Physician Fee Schedule for procedures, Medi-Span® Price Rx® Pro for pharmacy and drug administration costs, and published literature for costs unavailable in these sources. Costs were adjusted to 2023 USD using the Consumer Price Index inflation calculator from the US Bureau of Labor Statistics. Results: The study included 61 patients: 15 stage I, 16 stage II, 17 stage III, and 13 stage IV. Overall, patients had a mean age at diagnosis of 62.4 years (standard deviation ([SD] 10.1), 39.3% were female (n=24), and 67.2% (n=41) of patients were non-Hispanic White, 14.8 % (n=9) Non-Hispanic Black, 6.6% (n=4) Asian, 1.6% (n=1) Hispanic, and 9.8% (n=6) other race/ethnicity. Most patients had Medicare (45.9%, n=28) or private health insurance (34.4%, n=21). The average duration of disease (i.e., time from diagnosis to date of last office visit prior to their site's IRB approval date) was 4.5 years (SD 3.5). All patients had involvement of ≥1 organ system and 45.9% (n=28) had involvement of ≥2 organ systems at diagnosis. More than half of patients had renal (55.7%, n=34) or cardiac (52.5%, n=32) involvement. Nearly all patients completed first-line therapy at any point prior to their last office visit (93.4%, n=57); a minority of patients (9.8%, n=6) initiated first-line therapy, and 3 patients (4.9%) had a hematopoietic stem cell transplantation, one each in stages I, II, and III, during the study period. The median estimated AL amyloidosis-related healthcare costs (USD) during the 1-year study period were $95,253 (interquartile range [IQR] $2,869-497,504) for stage I, $190,796 ($5,249-499,470) for stage II, $414,677 ($28,365-533,081) for stage III, and $523,504 ($191,830-526,596) for stage IV. Discussion: This is the first study of AL amyloidosis that reports costs of care stratified by Mayo 2012 stage. In a prevalent population with AL amyloidosis, we found that overall, patients with AL amyloidosis have significant ongoing costs of care after completion of initial therapy at each Mayo 2012 stage, with stage IV patients having the highest AL amyloidosis-related costs. The percent of patients with cardiac or renal organ involvement is possibly higher than represented in this study; given the rapid progression and high early mortality rate seen with stage III and IV disease, some of these patients may not have fulfilled the 1-year observation period requirement and thus were excluded from the study. These data describe the significant and continued burden faced by patients with AL amyloidosis and the health care system for the years beyond initial diagnosis and completion of front-line treatment.