Famciclovir in Multiple Sclerosis

Treatment tested

• Famciclovir

  Human herpesvirus 1 DNA polymerase inhibitor

Inclusion Criteria: * Diagnosed with MS * Males and females aged over 18 * Taking Natalizumab (Tysabri) for the treatment of MS, * Be able to provide informed consent to take part in this study. * Female patients of childbearing potential (defined in section 13.4) must be willing to follow protocol contraceptive requirements. Exclusion Criteria: * Taking MS disease modifying treatment other than natalizumab (Tysabri) * On no treatment for MS * Taking additional immunomodulatory agents (either for MS treatment or other reasons) * Has received a course of high dose oral or intravenous steroids within 3 months of study entry. The use of low dose (total daily dose \<10mg) and/or the use of topical steroids will not act as an exclusion criteria. * Taking antiviral or antiretroviral medication for any reason * Known allergy to penciclovir, acyclovir, valaciclovir or famciclovir * Taking probenecid * Significant renal (CKD 3 or 4) and/or liver (ALT>3x ULN) impairment * Pregnant, or unwilling to take measures to prevent pregnancy * Breastfeeding

This is a proof-of-concept study in 30 patients with established Relapsing Remitting Multiple Sclerosis (RRMS). IMP is Famciclovir. It is a phase II type A open label study. Each individuals participation in the study will last 36 weeks and will be divided into three phases: pre-treatment (12 weeks), treatment with famciclovir (12 weeks), and post-treatment (12 weeks). During the first 12 week phase patients will remain on their usual treatment alone; this will be followed by three months of co-treatment with famciclovir and then followed by a final three months post-famciclovir treatment where participants will continue to take their usual treatment for RRMS. The primary aim is to explore the effect of famciclovir (500mg BD) on Epstein-Barr virus (EBV) shedding in the saliva of patients with MS