The results were published in the journal npj Parkinson’s Disease in the study, “Safety and tolerability of IRL790 in Parkinson’s disease with levodopa-induced dyskinesia—a phase 1b trial.”
Parkinson’s disease is a central nervous system disorder characterized by low levels of dopamine, causing tremors, stiffness, or slowing of movement.
Levodopa, a medication that helps counteract the shortage of dopamine in the brain, is the gold standard for treatment of Parkinson’s patients. But more than half the patients who use levodopa experience abnormal, involuntary movements — dyskinesia — within the first five years of treatment.
Studies have shown that long-term treatment with levopoda increases levels of a dopamine receptor, called dopamine D3 receptor, that seems to correlate with levodopa-induced dyskinesia.
IRL790 is a central nervous system medication that mainly targets the dopamine D3 receptor. In rat models of Parkinson’s disease, the treatment reduced involuntary movements caused by levodopa treatment without compromising the animals’ locomotion. Also, IRL790 showed anti-psychotic properties, suggesting its potential for treating both dyskinesia and psychosis in Parkinson’s patients.
In a prior Phase 1 trial, researchers tested ascending doses of IRL790 in healthy male volunteers. The treatment had a very good safety profile, with no serious adverse events reported, even at doses higher than those planned for patients.
Now, a team at the Karolinska Institutet in Sweden conducted a Phase 1b trial to determine the treatment’s safety and efficacy in Parkinson’s patients experiencing levodopa-induced dyskinesia.
The study (NCT03531060) included 15 Parkinson’s patients (nine men and six women) who randomly received oral capsules of IRL790 (11 patients) or an oral placebo (four patients) for four weeks. During the trial, all patients continued receiving their regular medication.
The study’s main objective was to assess the treatment’s safety — measured through the number of adverse events, physical examination, electrocardiogram, heart rate, blood pressure, and other laboratory measurements — after four weeks.
Secondary measures included changes from baseline in dyskinesia, measured with the Unified Dyskinesia Rating Scale (UDysRS), and Parkinson’s scores, measured with the Unified Parkinson’s Disease Rating Scale (UPDRS) and Parkinson’s Kinetigraph.
Thirteen patients completed the 4-week study, with IRL790 given at an average daily dose of 18 mg.
Overall, 14 patients (93.3%) reported 62 adverse effects. Most were reported during the first two weeks — when the dose of IRL790 was adjusted to each patient — and were mild to moderate, easily mitigated by dose adjustments. No serious adverse effects were reported in any of the groups.
Patients taking IRL790 had a mean reduction of 8.2 percent in dyskinesia scores compared to those taking a placebo.
“Among patients treated with IRL790, 55.5% were assessed as having an improved global clinical condition, as compared with baseline (much improved/minimally improved),” researchers stated.
There were no changes in symptoms relating to parkinsonism, either in the UPDRS or in measurements from the Parkinson’s Kinetigraph, a wrist-worn device that evaluates bradykinesia (slowness of movement) and dyskinesia during activities of daily living.
The results show that “IRL790 can be safely administered to patients with advanced PD, which will now “be of guidance for the design of phase 2 studies,” researchers said.
IRL790 is already being tested in a Phase 2 trial (NCT03368170), which will assess whether the treatment can reduce dyskinesia in a larger population (74 patients). The trial will also help establish the optimal dose for further testing.