The importance of considering differences in study and patient characteristics before undertaking indirect treatment comparisons: a case study of siponimod for secondary progressive multiple sclerosis

A Critical Appraisal of Matching-Adjusted Indirect Comparisons in Spinal Muscular Atrophy

In the absence of head-to-head trials, indirect treatment comparisons (ITCs) are often used to compare the efficacy of different therapies to support decision-making. Matching-adjusted indirect comparison (MAIC), a type of ITC, is increasingly used to compare treatment efficacy when individual patient data are available from one trial and only aggregate data are available from the other trial. This paper examines the conduct and reporting of MAICs to compare treatments for spinal muscular atrophy (SMA), a rare neuromuscular disease. A literature search identified three studies comparing approved treatments for SMA including nusinersen, risdiplam, and onasemnogene abeparvovec. The quality of the MAICs was assessed on the basis of the following principles consolidated from published MAIC best practices: (1) justification for the use of MAIC is clearly stated, (2) the included trials with respect to study population and design are comparable, (3) all known confounders and effect modifiers are identified a priori and accounted for in the analysis, (4) outcomes should be similar in definition and assessment, (5) baseline characteristics are reported before and after adjustment, along with weights, and (6) key details of a MAIC are reported. In the three MAIC publications in SMA to date, the quality of analysis and reporting varied greatly. Various sources of bias in the MAICs were identified, including lack of control for key confounders and effect modifiers, inconsistency in outcome definitions across trials, imbalances in important baseline characteristics after weighting, and lack of reporting key elements. These findings highlight the importance of evaluating MAICs according to best practices when assessing the conduct and reporting of MAICs.

Indirect comparisons of siponimod with fingolimod and ofatumumab in multiple sclerosis: assessing the feasibility of propensity score matching analyses

OBJECTIVE

Head-to-head trials comparing siponimod with fingolimod or ofatumumab in patients with multiple sclerosis (MS) are lacking. Instead, the comparative efficacy of siponimod can be derived from indirect treatment comparisons (ITCs). We assessed the suitability of ITCs leveraging individual patient data from relevant phase III trials across different MS phenotypes.

METHODS

One siponimod trial in patients with secondary progressive MS (SPMS), four fingolimod trials (three in relapsing-remitting MS [RRMS], and one in primary progressive MS [PPMS]), and two ofatumumab trials in relapsing MS (RMS) were considered. The suitability of ITCs was evaluated based on trial design, patient eligibility criteria, baseline patient characteristics, placebo response, and outcome definitions for each trial. Analyses deemed feasible were conducted using one-to-one propensity score matching (PSM).

RESULTS

An ITC between siponimod in SPMS and either fingolimod in RRMS or ofatumumab in RMS was not feasible because of insufficient overlap in key patient characteristics (e.g. disability level and relapse history) and differences in placebo response. However, a comparison between siponimod in SPMS and fingolimod in PPMS was feasible because of sufficient overlap in eligibility criteria and baseline characteristics. One-to-one PSM demonstrated siponimod was favored relative to fingolimod for time to 6- and 3-month confirmed disability progression though not significantly different (hazard ratio 0.76 [95% confidence interval 0.48-1.20; p-value = .240] and hazard ratio 0.80 [95% confidence interval 0.52-1.22; p-value = .300], respectively).

CONCLUSIONS

For trials in MS, clinical phenotype is an important determinant of ITC feasibility. An ITC between siponimod in SPMS and either fingolimod in RRMS or ofatumumab in RMS was not feasible. The only feasible comparison was between siponimod in SPMS and fingolimod in PPMS.

Matching-adjusted indirect treatment comparison of siponimod and other disease modifying treatments in secondary progressive multiple sclerosis

Background: Siponimod, interferon beta-1a (IFNβ-1a), IFNβ-1b and natalizumab have been evaluated as treatments for secondary progressive multiple sclerosis (SPMS) in separate randomized controlled trials (RCTs), but not head-to-head. These trials included heterogeneous patient populations, which limits the use of standard network meta-analysis (NMA) for indirect treatment comparison (ITC) of relative efficacy. Matching-adjusted indirect comparison (MAIC) aims to correct these cross-trial differences. We compared siponimod to other disease modifying treatments (DMTs) in SPMS using MAIC.Methods: Individual patient data (IPD) were available for siponimod (EXPAND), while only published summary data were available for IFNβ-1a (Nordic Study, SPECTRIMS, IMPACT), IFNβ-1b (North American Study, European Study) and natalizumab (ASCEND). MAICs were conducted between siponimod and the other DMTs by re-weighting patients in EXPAND based on logistic regression.Results: Siponimod was determined to be statistically significantly more effective for the outcome of time to 6 month confirmed disability progression (CDP) compared with 22 µg IFNβ-1a and 250 µg IFNβ-1b, and for the outcome of time to CDP-3 compared with 60 µg IFNβ-1a. Siponimod was numerically but not statistically superior for CDP in all other comparisons. For annualized relapse rate (ARR), with the exception of natalizumab, siponimod was numerically but not statistically superior to all comparators.Conclusions: EXPAND provides evidence of the efficacy of siponimod compared with placebo, and these MAICs complement this by demonstrating improved efficacy of siponimod relative to DMTs. Siponimod offers a significant therapeutic advance that may slow disease progression compared to other DMTs in an EXPAND-like population with secondary progressive disease.