Evaluating the effectiveness of simvastatin in slowing the progression of disability in secondary progressive multiple sclerosis: a synopsis of MS-STAT2, a multicentre, randomised controlled, double-blind, phase 3 clinical trial.

BACKGROUND: Despite the relative success of immuno-modulatory disease-modifying therapy in relapsing remitting multiple sclerosis, progressive worsening of disability remains a major problem, particularly for those with secondary progressive multiple sclerosis. Various underlying mechanisms are likely to contribute, augmented by comorbidities (such as vascular risk) and ageing. In the phase 2b MS-STAT trial, simvastatin (80 mg) (Sandoz Ltd, Camberley, UK) reduced the mean annualised whole brain atrophy rate by 43% compared to placebo in patients with secondary progressive multiple sclerosis (p = 0.003). We now report the phase 3, MS-STAT2 trial, with confirmed progression of disability as the primary outcome.

METHODS: A multicentre, phase 3, randomised, double-blind, placebo-controlled clinical trial was conducted at 31 UK neuroscience centres and district general hospitals. Secondary progressive multiple sclerosis participants aged 18-65 years were randomised 1 : 1 to oral simvastatin (80 mg), or matched placebo, based on a minimisation algorithm that incorporated the following factors: sex (male/female); age (< or ≥ 45 years); Expanded Disability Status Scale baseline score (≤ 5.5 or ≥ 6); whether participants were taking newly licensed (2017 onward) disease-modifying treatments for secondary progressive multiple sclerosis; and trial site. An independent and secure online randomisation service was used. All participants, site investigators and the trial co-ordinating team were blinded to treatment allocation. The Expanded Disability Status Scale was measured every 6 months and was compared to baseline scores, with remote data collection used when enforced by the COVID-19 pandemic. The primary outcome was time to Expanded Disability Status Scale-confirmed disability progression. Progression of disability was defined as an increase of at least one point on the Expanded Disability Status Scale if the baseline score was < 6, or an increase of 0.5 point if the baseline score was ≥ 6. The initial disability progression event was finalised as confirmed if the increase in Expanded Disability Status Scale score persisted at the next assessments ≥ 6 months later. Follow-up was for 36 months, or 54 months, for those without confirmed disability progression at 36 months who agreed to enter an optional blinded extension. An intention-to-treat analysis was carried out.

FINDINGS: The study was conducted between 10 May 2018 and 26 July 2024. There were 964 participants randomised, with 482 in the placebo group and 482 in the simvastatin group. 173 (35.9%) participants in the placebo group and 192 (39.8%) participants in the simvastatin group experienced Expanded Disability Status Scale-confirmed disability progression (adjusted hazard ratio = 1.13, 95% confidence interval 0.91 to 1.39, p = 0.263). No material differences in the secondary outcomes were observed. No major safety issues were seen.

INTERPRETATION: The MS-STAT2 trial did not demonstrate a treatment effect of simvastatin in slowing disability progression in participants with secondary progressive multiple sclerosis. Despite the favourable outcomes of the previous phase 2b trial, simvastatin use in secondary progressive multiple sclerosis should be confined to existing vascular indications.

FUNDING: This synopsis presents independent research funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme as award number 15/57/143.