P-334: Ixazomib‐Based Maintenance Therapy in Multiple Myeloma Patients Eligible and Ineligible for Transplantation: A Real‐World Study (INFINITE Study)

Introduction: Ixazomib (IXA) is reported to improve the prognosis of multiple myeloma (MM) patients (pts) when used as maintenance therapy, with good safety profile. Due to limited real-world data in China, we aim to explore the effectiveness and safety of IXA maintenance therapy in MM pts eligible and ineligible for transplantation.

Methods: This prospective, non-interventional, multi-center, ongoing study across 28 centers in China from May 2020 included MM pts who have received or were scheduled to be prescribed ≤1 dose of IXA-based treatment regimen, with IXA< 3 months (mo) from initial treatment. Primary endpoint: safety profile of IXA (adverse events [AEs]). Key secondary endpoints: effectiveness of IXA (overall response rate [ORR], duration of treatment [DOT], progression-free survival [PFS].

Results: As of 30 June 2023 (data cut-off), 419 pts were enrolled. Of them, 270 pts underwent IXA-based maintenance therapy. At a median follow-up of 16.6 mo, 153 pts discontinued IXA. Most common reasons for discontinuation were disease progression and AEs (11.8% each). Overall median age was 65 yrs [range 26-89]; Durie-Salmon stage III: 82.4% pts; International staging system (ISS) III: 44% pts; revised-ISS (R-ISS) III: 31% pts; high-risk by Stratification of Mayo mSMART: 49.3% pts. Common concomitant diseases before IXA treatment included hypertension (43.3%) and respiratory thoracic and mediastinal disorders (28.1%, including emphysema, pleural effusion, asthma, bronchitis chronic, pneumonitis, interstitial lung disease). Of the 89 pts who underwent SCT, 66 underwent R-ISS staging (R-ISS stage II/III n=54). Of the 181 pts without SCT, 132 underwent R-ISS staging (R-ISS stage II/III n=110).

At a median follow-up of 16.6 mo, overall median DOT was14.7 mo (95% CI: 11.3, 16.6). For transplant pts, median DOT was 19.5 mo (95% CI: 13.5, 19.8) [20.2 mo (95% CI:4.7, 21.2) for R-ISS stage I vs.19.3 mo (95% CI: 13.2, 19.8) for stage II/III pts]. For non-transplant pts, median DOT was 11.5 mo (95% CI: 8.2, 17.5) [13.2 mo (95% CI:4.2, 20.6) for R-ISS stage I vs.11.3 mo (95% CI: 8.2, 17.7) for stage II/III pts]. Overall, ORR before maintenance therapy was 88%, complete response (CR+sCR) rate was 30% which increased to 40% after maintenance therapy. For transplant pts, CR+sCR rate increased from 38% to 71% after maintenance therapy and from 27% to 41% in non-transplant pts.

Treatment-emergent AEs (TEAEs) related to IXA were 44.1%. Most common hematologic TEAEs were platelet count decreased(all grades 19.3%, ≥G3 5.2%) and anemia (all grades 5.2%, ≥G3 0.7%). Most common non-hematologic TEAEs were diarrhea (all grades 6.7%, ≥G3 0.7%) and nausea (all grades 2.6%, ≥G3 0.0%).

Conclusions:
This real-world study demonstrated favourable DOT and effectiveness profile of IXA as maintenance therapy in transplant-eligible and -ineligible MM pts regardless of R-ISS staging. IXA-based continuous therapy can be a viable treatment option for MM pts in the real world.