Rasagiline is a new selective monoamine oxidase B (MAO-B) inhibitor that has a significantly enhanced effect on MAO-B inhibition compared to the first-generation MAO-B inhibitors, Slegiline (Midolpir, Kingspin). In addition to having some degree of symptom relief in Parkinson’s disease, these drugs have been suggested to have neuroprotective effects and may be able to delay the course of Parkinson’s disease. The results of a clinical trial to determine whether resagiline has the ability to delay the course of Parkinson’s disease were recently published (September 24, 2009) in the New England Journal of Medicine, a leading international medical journal. The study adopted a new trial design (“delayed initiation therapy”, designed to eliminate as much as possible the interference of the drug’s symptom-relieving effects with its possible prolonging effects). In the double-blind trial, a total of 1,176 untreated Parkinson’s patients were randomized to two groups: one group received resagiline (at a dose of 1 mg/day or 2 mg/day) for 72 weeks (the early start group), and the other group received placebo for 36 weeks followed by resagiline (at a dose of 1 mg/day or 2 mg/day) for 36 weeks (the delayed start group). RESULTS: During the 72-week treatment period, patients treated with resagiline 1 mg/day had a significantly slower rate of progression in the early-start group compared with the delayed-start group (all 3 pre-defined endpoints met expectations). However, the resagiline 2 mg/day treatment group did not show similar results to those described above for 1 mg/day. The final conclusion was that early initiation of treatment with resagiline at a dose of 1 mg/day may have a delaying effect while improving the disease. 2 mg/day resagiline was not found to have a delaying effect on the disease course. Given the inconsistency between the 1 mg/day and 2 mg/day results, the interpretation of the neuroprotective effects of resagiline still requires some caution. It should be added that the drug is already available in Hong Kong and the United States (trade name Azilect, costing about US$10/day for 1 mg/day) and is not yet available in mainland China.