Ixazomib Versus Lenalidomide or Ixazomib and Lenalidomide Combination As Maintenance Regimen for Patients with Multiple Myeloma: Interim Analysis of a Multi-Center Prospective Study in China

Background Maintenance therapy (MT) deepens response and prolongs progression free survival (PFS) in patients with newly diagnosed multiple myeloma (NDMM) after frontline regimens. Ixazomib, a 2 nd generation oral proteasome inhibitor (PI), has been approved for MT because of the convenience and tolerability. Aims We conducted this prospective multi-center study to compare the efficacy and safety of Ixazomib (I-MT) or Ixazomib plus Lenalidomide (IL-MT) to Lenalidomide (L-MT) as maintenance regimens in NDMM patients. Methods This study was approved by the Institutional Review Board of Peking Union Medical College Hospital and registered (NCT04217967). NDMM patients were enrolled from 10 centers of North China MM Registry since September 2019. After 4 cycles of front-line induction therapy, patients who reached partial response (PR) would receive autologous stem cell transplantation (ASCT) if eligible, or keep up to 5 cycles of front regimens if ineligible, then start maintenance therapy. Patients did not reach PR would switch to a 2nd-line induction for 2-5 cycles and start MT once PR was achieved. For MT, 4mg of Ixazomib was given on day 1,8,15, and 25mg of Lenalidomide every other day on days 1-21 of a 28-day cycle. Patients in dual drug group were administrated with both Ixazomib and Lenalidomide, dose as listed above. The primary endpoint was PFS from MT. Results A total of 149 patients were enrolled, including 54 in I-MT, 65 in L-MT and 30 in IL-MT. The demographic and clinical characteristics were comparable among three groups at baseline (Table 1), including gender ratio, age, paraprotein isotype, ISS, R-ISS, response status before MT, and ASCT rate. The proportions of patients with high-risk cytogenetic abnormalities (HRCAs), defined as amplification 1q21, deletion 17p, t(4,14) and t(14,16), were comparable. The median follow-up duration since MT was 6.1, 11.1, and 5.9 months in I-MT, L-MT and IL-MT group, respectively. Disease progression developed in 9.3%, 12.3% and 10% (N=5, 8, 3, respectively) patients. The median PFS was not reached (NR) in all groups. Only one death occurred in I-MT group. There were 84%, 72.3% and 83.3% of the patients reached very good partial response (VGPR) or better before MT, while the best response rates rose to 93%, 82.3% and 90% during maintenance. The prevalence of peripheral neuropathy was 18.5% on I-MT, 10.8% on L-MT and 30% on IL-MT. Grade 2 PN occurred in 3, 1, and 0 patients, respectively. The incidence of gastrointestinal events was 11.1%, 1.5% and 20%, respectively. Grade 3-4 hematologic toxicities was 3.7%, 4.6%, and 3.3%. Infection rates were 7.4%, 6.2% and 3.3%. Skin rashes were more common in lenalidomide containing regimens (3.7%, 7.3% and 6.7%). No drug withdrawal was related to adverse events. Conclusions Due to inadequate access to melphalan and low rate of ASCT in China, there is still a gap of PFS in NDMM patients with those in western countries. We herein design this multi-centered prospective study to evaluate if dual drug MT will further strengthen response and make up the gap. Though the primary endpoint--PFS has not been reached in all treatment groups, dual MT improves response most and is quite tolerable. Figure 1. Baseline Characteristics in three groups. Abbreviations: ISS: international staging system; R-ISS: revised-ISS; HRCAs: high risk cytogenetic abnormalities. sCR: stringent complete remission. CR: complete remission. VGPR: very good partial remission. PR: partial remission. * p ＜ 0.05. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.