Ibudilast affects brain atrophy in PPMS, not SPMS

In the randomised phase 2 trial SPRINT-MS, the effect of ibudilast on brain measures of integrity was evaluated in both primary and secondary progressive MS (PPMS and SPMS). Results of a post-hoc analysis suggested that the effect of ibudilast on progression of brain atrophy is driven by patients with PPMS [1].

SPRINT-MS was a randomised, placebo-controlled phase 2 trial that evaluated the effect of 96 weeks of ibudilast on brain measures of integrity in both PPMS (n=134) and SPMS (n=121) patients [2]. Its primary outcome was progression of brain atrophy, measured by brain parenchymal fraction. The post-hoc analysis was performed because little is known about whether PPMS and SPMS differ in terms of treatment response.

There was a marginally significant 3-way interaction between the treatment effect and disease course (P=0.0576), said Dr Andrew Goodman (University of Rochester School of Medicine and Dentistry, USA), who presented the results. The overall treatment effect was primarily driven by patients with PPMS (P=0.005), not by patients with SPMS (P=0.97). The authors suggested this difference may at least in part be explained by faster atrophy progression in the untreated PPMS patients (placebo group) than in the untreated SPMS patients (P=0.016). Backwards selection (P<0.05) retained age, T2 lesion volume, retinal nerve fibre layer thickness, and longitudinal diffusivity as significant baseline covariates. However, the adjusted difference in treatment effect was still marginally significant (P=0.0715) and driven by PPMS (P=0.007).

Two other subanalyses of the SPRINT-MS trial were presented at the AAN 2019 meeting: one showing that ibudilast treatment was not associated with a decline in either serum or CSF NfL [3], the other that ibudilast slowed annual macular volume loss over 96 weeks compared to placebo [4].

  1. Goodman A, et al. AAN 2019, S12.007.
  2. Fox RJ, et al. N Engl J Med 2018;379:846-55.
  3. Fox R, et al. AAN 2019, P3.2-033.
  4. Bermel R, et al. AAN 2019, P3.2-049.