TRENTON, N.J. — In a major setback for patients and doctors, drugmakers Pfizer Inc. and Medivation Inc. have halted development of a potential Alzheimer's disease treatment after the drug for a second time yielded disappointing results in a late-stage clinical study.
Dimebon was furthest along in testing among the experimental Alzheimer's drugs being developed to try to stop or even reverse the course of the mind-robbing disease. Dimebon would have been the first such drug, and specialists just a couple of years ago had hoped it would be on the market this year.
Pfizer, the world's largest drugmaker by revenue, and Medivation said on Tuesday that Dimebon failed to significantly improve cognitive ability, as well as self-care and daily functions in patients with mild-to-moderate cases of the disease. The study involved about 1,000 patients who had Dimebon added to their ongoing treatment with Pfizer's former blockbuster Alzheimer's drug donepezil, or Aricept.
Aricept, jointly marketed by Pfizer and Japan's Esai Co. Ltd. and once heavily advertised, had about $3.7 billion in sales in 2009. It lost U.S. patent protection in November 2010, and sales have since plunged.
Dimebon, known chemically as latrepirdine, would have been an even bigger blockbuster if it had panned out. The experimental drug looked promising after it kept Alzheimer's symptoms from worsening for a year in an earlier patient study.
But Dimebon didn't work as hoped in a late-stage trial in which patients took it for six months. After those results, announced in March 2010, the companies said they were continuing three other studies that could prove Dimebon helped patients in combination with other Alzheimer's drugs or when used for a longer period.
Then last April Pfizer and Medivation said Dimebon also failed in another late-stage clinical trial, when it did not improve symptoms of the neurologic disorder Huntington's Disease.
After the latest failure, New York-based Pfizer and Medivation, headquartered in San Francisco, said they are ending development of Dimebon, as well as their agreement to market the potential treatment.
Pfizer still has one Alzheimer's treatment in late-stage testing, bapineuzamab, which it is jointly developing with Johnson & Johnson. It's a biologic drug, grown in living cells rather than made by mixing chemicals, and works differently than Dimebon.
Alzheimer's disease is the most common form of dementia, and drugmakers are trying to find a treatment that does more than temporarily ease the symptoms: memory problems, confusion, aggression and a general decline in ability to function, which together can hasten death. Many drugs have flopped in late-stage testing in recent years, including some that seemed to clear harmful plaque from afflicted brains.
The newest drug for Alzheimer's symptoms, Namenda, was approved back in 2003.
Cases of Alzheimer's disease are expected to triple by 2050, to around 106 million people worldwide. The disease strikes nearly a half million new patients a year, mainly as people hit their 70s or 80s.
In trading Tuesday, Pfizer shares rose 9 cents to $21.93, while Medivation stock dropped $1.82, or 3.3 percent, to $53.90.