About 37 fewer minutes of uncontrolled symptoms each day: Parkinson’s drug solengepras meets Phase 3 trial endpoint

For patients with Parkinson’s disease who experience motor fluctuations, the day is often divided into periods by the effects of medication: sometimes movement is easier; at other times, stiffness and slowness return to daily life. Reducing these periods of inadequate symptom control, known as “OFF time,” is an important treatment challenge. On October 7, Cerevance announced that its investigational drug solengepras met the primary endpoint in the Phase 3 ARISE trial. After 12 weeks of treatment, daily OFF time in the 150 mg group was 0.61 hours shorter than in the placebo group, equivalent to about 37 minutes.

ARISE was a randomized, double-blind, placebo-controlled trial that enrolled 341 patients who continued to experience motor fluctuations despite their existing treatment; 311 completed the 12-week study. Participants continued their existing Parkinson’s medications while receiving the study treatment. According to the company’s announcement, OFF time decreased from baseline by 1.56 hours in the 150 mg group and by 0.95 hours in the placebo group, with a statistically significant difference between the groups (p=0.035). The approximately 37 minutes represents the average difference after accounting for improvement in the placebo group; individual patients’ experiences and responses may differ.

Solengepras is a once-daily oral GPR6 inhibitor. The company explained that the drug acts on the indirect motor pathway in the striatum without directly acting on dopamine receptors, seeking to improve symptom control through a different mechanism. This trial provides evidence of short-term symptom improvement; it does not yet establish whether the drug can slow neurodegeneration or alter the course of the disease.

Signals of efficacy also extended to some aspects of daily functioning. The same company announcement, distributed through GlobeNewswire, reported that “ON time without troublesome dyskinesia” increased by 0.60 hours in the 150 mg group compared with placebo (p=0.0468). The MDS-UPDRS Part II score, which measures the impact of motor symptoms on daily living, improved by 1.91 points compared with placebo (p=0.0008). There were also signals of improvement in daytime sleepiness and exploratory quality-of-life measures, but these analyses used nominal p-values. Multiple comparisons must therefore be considered when interpreting them, and each result cannot be regarded as equally established evidence of efficacy.

Regarding safety, the proportion of patients who discontinued treatment because of adverse events was 3.5% in both the 150 mg and placebo groups; the incidence of dyskinesia was 4.4% and 1.8%, respectively. The identical discontinuation rates offer an indication of short-term tolerability, but a 12-week study remains insufficient to characterize the risks of long-term use. These figures alone also cannot establish that the drug is safer than other add-on treatments.

### Background Context

Research into Parkinson’s treatments is addressing symptom fluctuations and walking difficulties from different directions: one involves adapting deep brain stimulation to individual neural signals and gait, while another seeks new pathways for drug action. Solengepras belongs to the latter approach. Drug and device studies address different questions, enroll different patients, and differ in the maturity of their evidence, so they cannot be compared directly. Both, however, point to the same practical need: extending the time each day during which patients can move consistently.

The publicly available data currently remain a summary of the main results released by the company; the announcement published by GlobeNewswire is the same company release, rather than independent verification. The official program of the International Parkinson and Movement Disorder Society lists Robert Hauser as presenting the ARISE results, confirming the conference scheduling but providing no efficacy or safety figures. Cerevance plans to discuss a potential path to a marketing application with the U.S. Food and Drug Administration. This progress does not yet mean that an application has been submitted or approval obtained; full analyses and longer-term data will determine how far this new mechanism can advance.