Tenofovir Alafenamide for Treatment of Symptoms and Neuroprotection in Relapsing Remitting Multiple Sclerosis

As the in vivo reservoir of the Epstein-Barr virus, B cells play an important role in the perpetuation of MS disease activity. B cell depletion therapy with medications like ocrelizumab or rituximab have proved very successful in preventing clinical relapses and MRI activity in MS, but incomplete in terms of neuroprotection and symptomatic outcomes. Ocrelizumab and rituximab only target naïve and memory B cells expressing the CD20 marker but do not deplete the wide spectrum of B cell lineages including plasmablasts and plasma cells, which are also key reservoirs for EBV. This is particularly relevant to the mechanism of action of TAF, since EBV lytic reactivation occurs in coordination with B-cell differentiation. In vivo, the initiation of plasma cell differentiation provides the physiological trigger for EBV lytic reactivation, and EBV utilizes the plasma cell differentiation program to replicate. As these cells are ineffectively depleted by anti-CD20 treatment, the use of TAF would be highly complementary as an add-on treatment to anti-CD20 therapy. Anti-EBV therapy with TAF in combination with ocrelizumab or rituximab will therefore provide a synergistic approach to cover the whole EBV reservoir. The primary aims of the proposed trial are to determine if TAF, at the standard dose of 25 mg/day administered for 12 months: i) is safe and well-tolerated by individuals with RRMS over a period of treatment of 12 months; ii) leads to an overall improvement in fatigue, as assessed by the Modified Fatigue Impact Scale by 12 months; and iii) causes a reduction in serum concentrations of neurofilament light chain (NfL), a marker of neuronal damage in MS.