12 Jun 2007

See also treatment stories for other phase 2 results: 1, 3, 4, and 5.

At the second Alzheimer’s Association International Conference on Prevention, which concludes today in Washington, D.C., the statistical woes of the first phase 3 trial of an anti-amyloid drug (see related story) have left a vacuum that other therapeutic approaches were only too happy to fill. With an explicit reminder to take good news from phase 2 trials with the appropriate caution that they inevitably raise hope without offering an actual drug to most people for a few more years to come, here’s one summary.

Dimebon Still Going Strong
A drug that was definitely NIH (i.e., not invented here) is delivering basically the same strong effect in a blinded 6-month continuation that was already reported for the initial 6-month treatment period at recent conferences. Alzforum has published a detailed story of the prior data on this Russian drug (see ARF related news story), so today’s update merely summarizes the news since last month.

At the Prevention Conference, Rachelle Doody of Baylor College of Medicine in Houston, Texas, reported that at 12 months, the researchers still noted a clinical improvement above baseline in the treated group on the ADAS-Cog and the MMSE. This was a net improvement, not a slowing of decline. It was smaller than at the 6-month point, but still present. On activities of daily living and behavior problems, the treated patients had returned to baseline after an initial improvement at 6 and 9 months, but the placebo group deteriorated. Global function as measured by the CIBIC-plus scale stayed stable or improved in 69 percent of treated patients by 12 months. On all five endpoints measured, Dimebon maintained an improvement over placebo, Doody reported. (This trial included no biomarker readouts.) The drug’s good safety profile was unchanged. Whether the drug effect is symptomatic or also modified aspects of the underlying disease is unclear as yet, though mechanistic studies are ongoing, Doody added. Other scientists at the conference, on the whole, were puzzled as to how this drug could possibly have such a strong effect given that it is not linked to any of the major AD hypothesis.

The buzz among scientists was that this drug actually shows a more robust effect than either of the approved drugs do, but data for direct side-by-side comparisons are not available. When asked if Dimebon is better than the combination of an acetylcholinesterase inhibitor plus memantine, Doody said that she believed it might be but could only speculate at this point. According to Medivation Chief Medical Officer Lynn Seely, the patients are now on an open-label extension. Continuing the blinded phase further would have been unethical to the placebo group, who declined for a year while their fellow trial participants improved or stayed stable. As happens after positive phase 2 data, shares of the sponsoring company Medivation, Inc. in San Francisco rose after the news was disclosed even before Doody gave the formal scientific presentation on Tuesday morning. This flow of cash helps the company finance future trials, but no U.S. or European trial has begun yet or is scheduled for 2007. It’s important to note that this was a small trial with only 183 patients . Even if Dimebon survived phase III in the U.S., it would be years before the drug could hit the market.—Gabrielle Strobel.