Remote Ischemic Conditioning in PPMS

Remote Ischemic conditioning (RIC): Ischemic-preconditioning entails inducing short periods of cyclical tissue ischemia that confers subsequent protection against ischemia-reperfusion-injury. The rationale is that short periods of ischemia do not cause irreversible injury, but instead induce an endogenous protective environment. This short period of ischemia is not injurious, and it triggers endogenous protective signals (such as anti-inflammatory and antioxidant molecules) that reach distant organs, such as the heart, liver or the CNS. As an endogenous, non-specific response, the mechanisms involved in RIC are complex and include inflammation, oxidative stress, changes in endothelial function, cell survival etc. Current treatments for progressive Multiple Sclerosis (the immune-modulators Siponimod and Ocrelizumab) are only modestly effective and primarily benefit people with active inflammatory disease activity (recent relapses and/or enhancing lesions on MRI). Progression free of inflammatory activity is characterized by slow accumulation of disability, greatly affecting quality of life in people with Multiple Sclerosis (MS). The investigators believe RIC is ideally suited to be tested as a therapy for progression in MS. Recent clinical trials in vascular disease have shown that daily RIC can be performed for up to a year and suggested an all-cause mortality benefit. In a recent (RICAMIS trial, 2022) multicenter, randomized trial of people with acute ischemic stroke (\> 1,000 participants), 14-day RIC treatment led to improved functional outcomes at 6-months. No serious side effects were reported, and tolerability was good. This important study was the first phase III trial to find a "protective" effect for RIC in neurological disease, and highlights the timeliness and potential for re-purposing RIC as a therapy for MS. In this trial, the investigators will investigate whether RIC treatment can prevent disability worsening in people with Primary Progressive MS (PPMS). The primary objective of this trial is to demonstrate non-futility of RIC for reducing progression of disability, as measured with the timed 25-foot walk (T25FW), in people with PPMS. This is a phase II open-label, single-center, single-arm futility trial. The study will follow the Simon-2-stage MiniMax design for futility studies.