©© 2009 American College of Clinical Pharmacology, Inc.
The Journal of Clinical Pharmacology, 10.1177/0091270009336735
Single-Dose Administration of MK-0657, an NR2B-Selective NMDA Antagonist, Does Not Result in Clinically Meaningful Improvement in Motor Function in Patients With Moderate Parkinsons Disease
Carol Addy 1*,
Chris Assaid 1,
David Hreniuk 1,
Mark Stroh 1,
Yang Xu 1,
W. Joseph Herring 1,
Aaron Ellenbogen 2,
H. A. Jinnah 3,
Louis Kirby 4,
Mark T. Leibowitz 5,
R. Malcolm Stewart 6,
Daniel Tarsy 7,
James Tetrud 8,
S. Aubrey Stoch 1,
Keith Gottesdiener 1,
and
John Wagner 1
1 Merck Research Laboratories
2 Quest Research Institute
3 Johns Hopkins Hospital
4 Pivotal Research Center
5 California Clinical Trials
6 Radiant Research
7 Beth Israel Deaconess Medical Center
8 The Parkinson's Institute
* To whom correspondence should be addressed. E-mail: carol_addy{at}merck.com.
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Abstract |
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The glutamatergic system is thought to contribute to the motor disturbances observed in Parkinsons disease. Blockade of glutamatergic activity by a selective antagonist of the NR2B subunit of the N-methyl-D-aspartate (NMDA) receptor is associated with improvement in motor symptoms in a preclinical model of Parkinsons disease. A randomized, double-blind, double-dummy, placebo-controlled, 3-period crossover study was conducted in patients with moderate Parkinsons disease to evaluate the pharmacologic activity of MK-0657, an NR2B-selctive NMDA receptor antagonist. Patients (n = 16) received single oral doses of MK-0657 7 mg, carbidopa/levodopa 25/250 mg (LD) as a positive control, and placebo, after which motor function was serially evaluated by means of the Unified Parkinsons Disease Rating Scale–Motor Examination (UPDRS-ME). LD administration resulted in significant improvement in the UPDRS-ME relative to placebo (P = .025), confirming the sensitivity of the test paradigm; however, the UPDRS-ME change following MK-0657 administration showed no improvement compared with placebo (P = .110) despite exceeding the target MK-0657 plasma concentration of 400 nM. Although the administration of MK-0657 was generally well tolerated, it was associated with increases in systolic and diastolic blood pressure relative to placebo. The results of this study do not support ongoing clinical development of MK-0657 as a novel monotherapy for Parkinsons disease.