Merck & Co., Inc. Throws Its Own Entry Into the Parkinson's Disease Drug Race

Published: Oct 11, 2012

Parkinson's Disease (PD), unlike Alzheimer's, has good therapeutic treatment. The mainstay of treatment involves dopaminergic agonist strategies, (1) Levodopa which is a dopamine precursor, (2) direct dopaminergic agonists, and (3) monoamine oxidase-B (MAO-B) inhibitors. Although treatment options are good, problems with PD therapy remain. Long term use of the most effective drug, Levodopa, is associated with dyskinesias. Also, there is little evidence that any of the drugs are disease modifying drugs. i.e., halt disease progression. There are trials testing whether the MAO-B inhibitors are disease modifying. (For a nice summary of Parkinson's and potential drug development, see this article by another Seeking Alpha contributor.) Another troublesome aspect of PD therapy is that after long term use of Levodopa, patients experience an "off" effect. This is an often unpredictable loss of therapeutic drug effect. Merck (MRK) is developing Preladenant, which is an adenosine 2A (A2A) receptor antagonist. There is promising Phase 2 trial data that suggest Preladenant may reduce "off" time. In preclinical animal models, preladenant monotherapy improves motor function without causing dyskinesia. But more relevant to clinical development, preladenant in combination with levodopa improved motor function without worsening dyskinesia. In a phase 2 trial, preladenant as an adjunct to Levodopa decreased "off" time compared to placebo. All patients in the study were on Levodopa therapy. Phase 3 trials, the first of which may have results in early 2013 are underway; Placebo Controlled Study of Preladenant in Participants With Moderate to Severe Parkinson's Disease (P07037 AM3), A Placebo- and Active Controlled Study of Preladenant in Subjects With Moderate to Severe Parkinson's Disease (Study P04938 AM5), and An Active-Controlled Extension Study to P04938 and P07037 (P06153 AM3).

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