Final Overall Survival Results from TOURMALINE-MM3 and MM4 Trials of Ixazomib Maintenance in NDMM
Overview
The final overall survival (OS) analyses from the TOURMALINE-MM3 and MM4 phase 3 trials showed no statistically significant OS benefit with ixazomib maintenance therapy compared to placebo in newly diagnosed multiple myeloma (NDMM) patients post-ASCT or in transplant-ineligible patients. Despite significant improvements in progression-free survival (PFS) with ixazomib, OS outcomes were similar between treatment arms after extended follow-up.
Background
Multiple myeloma treatment options have expanded, improving progression-free and overall survival, but tolerable maintenance therapies remain needed, especially for elderly and high-risk patients. Lenalidomide is standard post-ASCT maintenance, but increasing lenalidomide exposure and resistance highlight the need for alternatives. Ixazomib, an oral proteasome inhibitor, offers a convenient maintenance option and has been approved in several countries based on the TOURMALINE-MM3 and MM4 trials demonstrating PFS benefits. However, interim OS analyses did not show significant differences, prompting final OS evaluation.
Data Highlights
Study
Population
Median PFS (Ixazomib vs Placebo)
Hazard Ratio (PFS)
Median OS (Ixazomib vs Placebo)
Hazard Ratio (OS)
TOURMALINE-MM3
Post-ASCT NDMM with ≥PR
26.5 vs 21.3 months
0.72 (95% CI, 0.58–0.89; p=0.002)
NR vs NR (5-year OS: 74% vs 73%)
1.008 (95% CI, 0.744–1.367; p=0.958)
TOURMALINE-MM4
Transplant-ineligible NDMM with ≥PR
17.4 vs 9.4 months
0.66 (95% CI, 0.54–0.80; p<0.001)
NR vs NR (5-year OS: 55% vs 56%)
1.136 (95% CI, 0.853–1.514; p=0.382)
Key Findings
Ixazomib maintenance significantly improved progression-free survival compared to placebo in both post-ASCT (MM3) and transplant-ineligible (MM4) NDMM patients.
Final overall survival analyses showed no statistically significant difference between ixazomib and placebo arms in either study after extended follow-up (64 months MM3, 36 months MM4).
Five-year OS rates were comparable between treatment arms: 74% vs 73% in MM3 and 55% vs 56% in MM4.
Sensitivity analyses adjusting for confounding factors and subsequent therapies did not reveal significant OS benefit with ixazomib.
The evolving treatment landscape with effective salvage therapies likely impacts OS endpoints in maintenance trials.
Clinical Implications
While ixazomib maintenance provides a meaningful PFS benefit with convenient oral dosing, clinicians should recognize that this does not translate into an OS advantage in the current treatment context. The availability of multiple effective salvage options may mitigate OS differences, emphasizing the importance of PFS and quality of life in maintenance therapy decisions. Ixazomib remains a viable maintenance option, particularly for patients unsuitable for lenalidomide or parenteral proteasome inhibitors.
Conclusion
Ixazomib maintenance therapy significantly prolongs progression-free survival in newly diagnosed multiple myeloma patients but does not confer a statistically significant overall survival benefit after extended follow-up. These findings highlight the complexity of interpreting OS in the era of multiple effective subsequent therapies.
References
Moreau et al. 2019 -- TOURMALINE-MM3 Study Results
Dimopoulos et al. 2020 -- TOURMALINE-MM4 Study Results
by Meletios A. Dimopoulos, Sagar Lonial, Wee-Joo Chng, Shinsuke Iida, María-Victoria Mateos, Gareth J. Morgan, Cong Li, Catriona Byrne, Kaveri Suryanarayan, Richard Labotka, S. Vincent Rajkumar
