Study protocol for a multicentre, randomised, double-blinded, placebo-controlled, multi-arm, multi-stage, trial of SpironolacTone and famciclOovir in the treatment of Progressive Multiple Sclerosis to prevent disability progression: the STOP-MS trial

Introduction: Targeting progressive multiple sclerosis (MS) addresses the current single biggest unmet need in the MS therapeutic landscape and anti-Epstein-Barr virus (EBV) therapy potentially strikes at the root cause. The SpironolacTone and famciclOvir in the treatment of Progressive MS to prevent disability progression (STOP-MS) trial has been developed to assess anti-EBV therapies in the treatment of progressive MS. Methods and analysis: STOP-MS is a multi-arm, multi-stage, randomised, double-blind, placebo-controlled trial testing spironolactone and famciclovir to prevent disability progression in MS. Australians with progressive forms of MS, aged 25 to 70 years with established disability, are eligible. Recruitment commenced in March 2025 and the first participant was enrolled on 15 April 2025. The sample size for STOP-MS is 150 in stage 1 and 300 in stage 2. In stage 1, the composite primary outcome measures will be reduction of EBV DNA in saliva and serum EBV nuclear antigen-1 antibody titres. Minimum criteria for consideration of progression to stage 2 will be a 10% reduction in the composite outcome measure. In stage 2, the primary outcome measure will be 6-month confirmed disability progression analysed using Cox-proportional hazards. Trial registration number: The STOP-MS trial has been acknowledged by the Therapeutics Goods Administration under the Clinical Trial Notification scheme (CT-2023-CTN-03 505-1) and is registered with the Australian and New Zealand Clinical Trial Registry (ACTRN12623000849695).