Pfizer and Medivation reported results from the phase III HORIZON trial of the investigational drug dimebon (latrepirdine) in patients with Huntington disease. Dimebon did not achieve statistical significance for either of the co-primary endpoints, the Mini-Mental State Examination (MMSE), which measures cognition (p=0.39), or the Clinician's Interview-Based Impression of Change, plus caregiver input (CIBIC-plus), which measures global function (p=0.84).

The double-blind, placebo-controlled phase 3 HORIZON trial enrolled 403 patients with Huntington disease at 64 sites in North America, Europe and Australia. The trial included patients who had cognitive impairment, based on investigator judgment and verified by MMSE score. Patients were randomized to receive either 20 mg of dimebon three times daily or placebo for six months.

No statistically significant improvements were achieved for the dimebon group relative to placebo on either of the co-primary endpoints. Dimebon was generally well-tolerated in the study. The overall incidence of adverse events was equivalent between the treatment groups: 69% in the dimebon group and 68% in the placebo group. Adverse events occurring in at least 5% of dimebon treated patients and more frequently than in placebo treated patients were chorea (8% vs. 4%), headache (6% vs 3 %) and fatigue (5% vs 0 %).