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 Parkinson's disease.

The glutamatergic system is thought to contribute to the motor disturbances observed in Parkinson's 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 Parkinson's disease. A randomized, double-blind, double-dummy, placebo-controlled, 3-period crossover study was conducted in patients with moderate Parkinson's disease to evaluate the pharmacologic activity of MK-0657, an NR2B-selective 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 Parkinson's 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 Parkinson's disease.

Methodological Extensions of Phase 2 Trial Designs Based on Program-Level Considerations: Further Development of a Case Study in Neuropathic Pain.

BACKGROUND: Traditionally, sample size considerations for Phase 2 (Ph2) trials are based on the desired properties of the design and response information from the trials. METHODS: This work extends that of Patel et al (2012) to design Ph2 trials based on program-level optimization (ie, optimizing the entire Ph2/3 trial design strategy). It describes a framework to evaluate the impact that several Ph2 design features have on the probability of Phase 3 (Ph3) success and the expected net present value (eNPV) of the product. These factors include the Ph2 sample size, decision rules to select Ph3 dose(s) and sample sizes, as well as number of Ph3 trials. Using neuropathic pain as an example, simulations illustrate the framework and show the benefit of including these factors in the overall decision process. Patel et al considered one dose of test drug in each of exactly two Ph3 trials. This work extends that to consider 1 or 2 doses in each of 2 Ph3 trials and, if needed, 1 or 2 additional Ph3 trials to substantiate the usefulness of the second dose. RESULTS: We found that employing a quantitative algorithmic strategy to choose 1 or 2 doses for Ph3 based on trial results does not substantially alter the eNPV compared to a strategy of always taking 2 doses to Ph3, if appropriate. Similar to the findings by Patel et al, for 1 Ph3 dose, we found that Ph2 sample size can be optimized at small to modest sizes when allowing for the possibility of taking 2 doses to Ph3. We found that choice of number of Ph2 doses depends on the magnitudes and shapes of the true underlying efficacy and safety dose-response curves. CONCLUSION: Simulating a sequence of clinical trials can inform trial design and drug development strategy.