Dimebon Disappoints in Phase 3 Trial of Huntington's Disease

Megan Brooks

April 12, 2011

April 12, 2011 — Top-line results from a phase 3 study of latrepirdine (Dimebon; Pfizer/Medivation) in patients with mild-to-moderate Huntington's disease show that the drug failed to achieve statistical significance for either of the study's coprimary endpoints.

The 2 endpoints were the Mini-Mental State Examination, which measures cognition (P = .39), and the Clinician's Interview-Based Impression of Change Plus Caregiver Input, which measures global function (P = .84).

"We are disappointed with the results of the HORIZON trial given the high unmet need in this patient population," David Hung, MD, president and chief executive officer of Medivation, which is developing the drug in collaboration with Pfizer, said in a statement.

"At this point," Dr. Hung said, development of latrepirdine in Huntington's disease will be discontinued.

Full results of the HORIZON trial are expected to be presented at an upcoming medical meeting, although the companies did not say which one.

Mixed Results With Latrepirdine

Medivation and Pfizer have been developing latrepirdine for the treatment of Alzheimer's disease (AD) and Huntington's disease. Studies to date with latrepirdine in AD have yielded mixed results. A phase 2 study of the drug in patients with mild-to-moderate AD published in The Lancet in 2008 yielded strongly positive results (Lancet. 2008;372:207-215).

In that trial, patients treated with latrepirdine showed impressive and significant improvements across all domains measured, including cognitive function, memory, ability to perform tasks of daily living, global function, and behavior, which increased and then were sustained over time.

Yet, in the phase 3 CONNECTION trial reported in March 2010, the drug failed to yield any improvements in cognition or global function after 6 months of treatment. Reasons for the sharply contrasting findings are still being debated.

The CONCERT trial may soon provide some answers. This 12-month phase 3 trial of latrepirdine and its open-label extension in patients with mild-to-moderate AD "is continuing," Dr. Hung noted, with top-line data expected in the first part of 2012.

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