Dean, Robert M.

Abstract Background: MCL is a B-cell non-Hodgkin lymphoma for which auto-HCT is often employed in first CR, based on non-randomized phase 2 trials, and a randomized trial (Dreyling et al, Blood 2005) conducted before the advent of more effective induction and maintenance regimens. The TRIANGLE trial (Dreyling et al, Lancet 2024) suggested that auto-HCT may not add benefit to more effective induction and maintenance regimens containing high-dose cytarabine, rituximab and BTK inhibitors. E4151 explored whether auto-HCT benefits pts achieving deep first remission, as measured by a highly sensitive immunoglobulin high throughput sequencing minimal residual disease (MRD) assay. Methods: EA4151 is a four arm trial conducted through the U.S. National Clinical Trials Network (NCTN) and Blood and Marrow Transplant Clinical Trials Network (BMT-CTN). Pts with MCL between the ages of 18 and 70 and in first remission were eligible. After induction, pts underwent PET/CT, bone marrow biopsy, and the clonoSEQ® MRD assay from peripheral blood. Pts in CR with uMRD at 1 in 10-6 sensitivity (uMRD6) were randomized 1:1 to Arm A (auto-HCT + 3 years of maintenance rituximab [MR]) or Arm B (3 years of MR alone), stratified by MIPI-c score and intensive vs non-intensive induction. Pts with either MRD-positive (MRD+) CR or MRD-indeterminate CR (Arm C and Arm D, respsectively) both received auto-HCT + 3 years of MR. Pts who were MRD+ pre-transplant had MRD repeated at day 100. Primary endpoint was to compare overall survival (OS) in Arms A and B, with secondary endpoints including progression-free survival (PFS). Primary analysis population included all randomized pts. As some pts refused their assigned treatment (N=65 [25.3%] for arm A and N=2 [0.8%] for arm B), a “treated as assigned” analysis was also performed. Stratified logrank test was used to compare survival distributions. P-values are two-sided. Results: From Aug 2017 to July 2024, 650 pts were assigned to a treatment arm with 257, 259, 49, and 85 pts enrolled on Arms A, B, C, and D, respectively. Pts were 79% male and 92% white race. Median age was 60 years (range 27-70). MIPI-c was low/low-intermediate (LI) in 63% and high/ high-intermediate (HI) in 37%. Induction was intensive (defined as high-dose cytarabine-containing) in 73% and non-intensive in 27%. A BTK inhibitor was given during induction in 7.2% of pts, and during maintenance in 0.3% of pts. The third pre-planned interim analysis was based on data as of 7/15/24, with median follow up of 2.7 years. The futility boundary was an OS hazard ratio (HR) of 0.984 for Arm A vs B. The estimated OS HR for Arm A vs B in all randomized (n=516) and pts treated as assigned (n=375) were 1.11 (CI 0.71-1.74, p=0.66) and 1.00 (CI 0.58-1.74, p=0.99), respectively and crossed the futility boundary. The 3 year (yr) OS for Arms A and B were 82.1% and 82.7% in all randomized pts, and 86.2% and 84.8% in pts treated as assigned. The estimated PFS HR for Arm A vs B in all randomized and pts treated as assigned were 1.05 (CI 0.71-1.56, p=0.79) and 0.95 (CI 0.59-1.54, p=0.84), respectively. The 3 yr PFS for Arms A and B were 76.6% and 77.4% in all randomized pts, and 81.5% and 80.4% in pts treated as assigned. For Arm C, 3 yr OS and PFS were 81.9% (CI 69.6-96.4%) and 76.9% (CI 64.4-91.7%), respectively. For Arm D, 3 yr OS and PFS were 85.1% (CI 76.0%-95.4%) and 73.4% (62.7-85.9%), respectively. For the MIPI-c low/LI group, 3 yr OS was 84.6% vs 85.7% for Arm A vs B (p=0.96), while in the MIPI-c high/HI group, 3 yr OS was 77.4% vs 77.6% for Arm A vs B (p=0.71). For the intensive induction group, 3 yr OS was 83.0% vs 86.2% for Arm A vs B (p=0.30), while in the non-intensive induction group, 3 yr OS was 79.5% vs 72.8% for Arm A vs B (p=0.48). Exploratory analysis of MRD+ pts (Arm C) showed that pts who converted to uMRD6 post auto-HCT (n=17) had 3 yr OS of 100% and PFS of 100%, whereas those who remained MRD+ (n=13) post auto-HCT had 3 yr OS of 63.6% and PFS of 48.8%. Causes of death (COD) in Arm A were 4.7% lymphoma, 5.1% COVID-19, and 5.0% other/unknown. COD in Arm B were 3.5% lymphoma, 6.6% COVID-19, and 4.6% other/unknown. In Sept 2024, the DSMC recommended termination of accrual and release of trial findings based on these results. Conclusion: In this interim analysis, in the era of highly effective induction and maintenance regimens, MCL pts in first CR with uMRD6 did not benefit from consolidative auto-HCT. Pts who remain MRD+ after induction may benefit from auto-HCT. Longer follow-up will be important to confirm these findings.

Abstract Abstract 5045 Observation remains the standard approach to patients with monoclonal gammopathy of undetermined significance (MGUS) and asymptomatic multiple myeloma (AMM) who lack end-organ impairment characteristic of symptomatic MM. Institution of early MM therapy has not been shown to improve survival or alter the natural progression of the disease. Cyclooxygenase-2 (COX2) inhibitors inhibit proliferation and induce apoptosis in drug resistant MM cell lines. 23 asymptomatic adult patients with a serum monoclonal protein >1g/dL, from Cleveland Clinic, Mayo Clinic, or University of Arkansas Medical Center between August 2005 and April 2008 were randomized to either celecoxib or placebo in a double-blind, 1:1 fashion. The primary end point was change in the monoclonal protein concentration after 6 months. Correlative biomarkers, including IL6 and IL-6R, CD4/CD8+ T-cell ratios, and beta-2 microglobulin, were examined before and after treatment. Celecoxib had no significant effect on the median monoclonal protein concentration, which went from a median of 1. 44 to 1. 65 g/dL with placebo and 2. 42 to 2. 24 g/dL with Celecoxib (p=0. 36), or on any of the analyzed correlative markers (all p-values >0. 34). One patient's monoclonal protein concentration increased on placebo, but he did not require treatment for symptomatic MM. There were no adverse events of Grade 2 or higher. Celecoxib was well tolerated in contrast to previous reports when given in higher doses and in combination with thalidomide. Although accrual was limited we conclude that celecoxib has no clinical or immunologic effect on high risk asymptomatic plasma cell disorders. This study does not support using celecoxib for preventing progression to symptomatic MM. Future studies on progression of MGUS to symptomatic MM would require more patients and a longer follow-up period. Disclosures: Off Label Use: Celecoxib for chemoprophylaxis. Hussein:Celgene: Employment. Reu:Celgene: Research Funding.