WEST PALM BEACH, FLORIDA — An over-the-counter antihistamine that had shown potential for treatment of multiple sclerosis (MS) in animal studies was linked to significant worsening of symptoms in humans, new trial data suggested.
,” investigators said.
The inexpensive antihistamine had been touted as a potential MS treatment following promising early findings, and some patients are reportedly taking it on an off-label basis. It was one of four approved drugs in an ongoing trial led by the National Institute of Allergy and Infectious Diseases (NIAID) to investigate the drugs’ efficacy in the treatment of MS.
“Most patients on the other drugs progressed much slower compared to their baseline,” said senior investigator Bibi Bielekova, MD, with NIAID. “When we compare the results in clemastine arm with all other patients treated with the remaining drugs, the probability that our patients progressed by chance is lower than 0.01%.”
The findings were presented at the annual meeting held by the Americas Committee for Treatment and Research in Multiple Sclerosis (ACTRIMS).
TRAP-MS Trial
The OTC antihistamine clemastine has been available for decades under the brand names Tavist and Dayhist. In addition to findings from mouse studies, results from a small clinical trial reported in 2017 suggested that clemastine may promote myelin repair. Other animal studies and another small study with healthy volunteers also suggested the drug may reduce immune activity.
Clemastine fumarate is one of four drugs in the ongoing TRAP-MS phase 1/2 trial, which is sponsored by NIAID. The study is designed to determine what effects, if any, the drugs have on MS biomarkers either alone or in combination.
Other drugs in the study include the diabetes drug pioglitazone (Actos), the muscle relaxant dantrolene (Ryanodex, Revonto, and Dantrium), and the idiopathic pulmonary fibrosis drug pirfenidone (Pirespa).
An estimated 250 adults with MS were expected to be enrolled in the trial, which began in 2017 and is scheduled to reach its primary completion in 2025.
Per the study protocol, nine patients in the clemastine arm were assigned to receive 8 mg/d (divided into three doses of 2, 2, and 4 mg). Cerebrospinal fluid samples were collected at baseline and 6 months after clemastine treatment began.
Worsening Symptoms
The three patients whose worsening symptoms triggered stopping criteria when they demonstrated increased disability five times faster than their 18-month baseline, researchers reported.
These participants had increased levels of C-reactive protein and erythrocyte sedimentation rate and gained weight, which study authors said were “suggestive of systemic pro-inflammatory state.”
“We found that clemastine treatment causes significant changes in purinergic metabolism,” lead author Joanna Kocot, PhD, a NIAID fellow, said during the ACTRIMS presentation. “We also confirmed that this toxic effect of clemastine was because of pyroptosis,” a form of cell death.
None of the remaining 55 patients treated with other TRAP-MS therapies triggered safety criteria, which study authors said offered “evidence for clemastine toxicity.”
Demographic information was not provided, but the patients on clemastine with worsening symptoms were older, more disabled, and more obese than the other six patients in the clemastine arm, Dr. Bielekova said during the conference presentation.