SAN DIEGO – New Zealand researchers halted a small trial that was testing the use of the antipsychotics clozapine and risperidone to treat progressive multiple sclerosis because significant side effects caused participants to withdraw.
The adverse events appeared even though the doses were much smaller than those routinely given to patients with psychiatric illnesses. “The neurologists realized it was in the participants’ best interest to stop,” said study lead author Anne Camille La Flamme, PhD, of Victoria University of Wellington (New Zealand). “Adverse events included dizziness, muscle weakness, and falls.”
Dr. Anne Camille La Flamme
The researchers launched the study – a blinded, randomized, placebo-controlled trial – to learn whether the two antipsychotic drugs, also known by the brand names Clozaril and Risperdal, have potential as treatments for progressive multiple sclerosis.
Previous in-vitro research had linked the drugs to anti-inflammatory effects in the central nervous system, Dr. La Flamme said, and researchers believed that the progressive form of MS might be especially vulnerable to their effects because of high immune system involvement.
The researchers planned to randomly assign three groups of 12 patients per arm to placebo, clozapine, and risperidone.
For clozapine, “the doses were very low, much lower than you’d expect for psychiatric use,” Dr. La Flamme said. A typical dose for psychiatric disorders is about 350 mg/day, she said, and the trial aimed to use 100-150 mg/day with an eye toward preventing dose-dependent side effects.
As for risperidone, a typical dose is about 4 mg/day, and the trial began at 2 mg/day and would increase to 3.5 mg/day, she said.
Three subjects in the clozapine group had to withdraw within 2 weeks when their doses had only reached an average of 35 mg/day. Two of three in the risperidone group withdrew within 4 months.
In light of the adverse effects, “it was deemed not wise to continue,” Dr. La Flamme said.
The placebo group, meanwhile, completed the trial at 178 days and had adverse effects that were more indicative of MS, she said.
What happened? One possibility is that disability from MS made the adverse events more evident, Dr. La Flamme said. Another possible explanation is that the underlying MS physiology changed the targets of the medications, she said.
“We have no conclusive evidence that would suggest one over the other,” she said. “But a lot of the evidence supports the idea that it’s a change in the physiology, that something about those pathways has been altered.”
It’s clear, she said, that the doses of the drugs in the trial were not appropriate. However, a big question remains: “We do not know whether these medicines are effective at reducing neuroinflammation.”
It’s possible, she said, that a “whisper of a dose” could still be effective. “It may get back to how these agents metabolize and become an active form.”
The study was funded by New Zealand’s Ministry of Business, Innovation and Employment. Dr. La Flamme disclosed that the study team has a patent for repurposing of clozapine and risperidone to treat MS.
SOURCE: La Flamme A et al. ACTRIMS Forum 2018, abstract P031.