Clemastine Fumarate as Remyelinating Treatment in Internuclear Ophthalmoparesis and Multiple Sclerosis

Rationale: Clemastine fumarate has been identified as potential remyelinating therapy for multiple sclerosis (MS). The (long-term) effects of clemastine need to be confirmed in clinical models for MS. Internuclear ophthalmoparesis (INO) may be used as a clinical model for investigating remyelinating therapies by measuring horizontal eye movements with infrared oculography. Furthermore, infrared oculography combined with a single dose of fampridine may be used to identify individuals with MS that are most likely to benefit from remyelinating therapy. Objective: To assess the (long-term) efficacy of clemastine fumarate in improving dysconjugacy of eye movements in patients with internuclear ophthalmoparesis and multiple sclerosis. Secondly, to assess whether a response to a single dose of fampridine can predict the effects of clemastine treatment. Study design: A single-centre double-blind randomized placebo-controlled trial consisting of a 6 months (180 days) treatment period followed by a 30 months follow-up period. Study population: 80 MS patients, age 18-70 years, with INO. Intervention: The intervention group will receive 4 mg of clemastine fumarate twice daily (8 mg/day) for 6 months (180 days), the control group will receive an equivalent amount of placebo. At baseline all participants will receive a single 10 mg dose of fampridine. Main study parameters/endpoints: The primary outcome measure is the change in versional dysconjugacy index (VDI) of area under the curve (AUC) measured by infrared oculography. Secondary outcome measures include changes in other VDI measures (peak velocity per amplitude (PV/Am) and peak velocity (PV)), changes in VDI after single fampridine dose, other oculography parameters (e.g. saccadic latency, anti-saccades), (peripheral) retinal nerve fibre layer (pRNFL) and (macular) ganglion cell inner plexiform layer (mGCIPL) thickness measured by OCT, SDMT, EDSS, high and low contrast visual acuity, subjective visual functioning (NEI-VFQ-25 and NOV-AU questionnaire), quality of life (EQ5D-5L) and fatigue (CIS20R and NFI-MS questionnaire). Nature and extent of the burden and risks: Participation in the study will consist of a total of 7 study visits. Study visits will include physical/neurological examination, infrared oculography, OCT, visual acuity tests, a cognition test (SDMT), 5 questionnaires and blood samples for safety laboratory tests. Considering both clemastine and fampridine are registered and well-established drugs and have been used in clinical practice, the estimated risk of unexpected adverse reactions is low.