(AP) A closely watched experimental Alzheimer's treatment has failed to slow the disease in one late-stage study, a big disappointment for doctors and patients but not the end of the road for the drug. Pfizer Inc. said Monday that it will continue to study its effect on a different group of patients.
Pfizer, which is testing bapineuzumab with partner Johnson & Johnson, said the injected drug didn't slow mental or functional decline in patients with mild or moderate Alzheimer's disease. The study included about 1,100 patients who carry a gene called ApoE4, which gives people a higher risk of developing the memory-robbing disorder.
About half the population does not carry that gene, however, and studies in patients without the gene continue. Results of one trial are set to be announced later this summer.
Johnson & Johnson spokeswoman Ellen Rose said scientists who conducted mid-stage tests on bapineuzumab had seen "a hint that the people who are carriers of the ApoE4 gene might not have as good a chance as people who are not carriers."
New York-based Pfizer and Johnson & Johnson, based in New Brusnwick, New Jersey, are each running two studies of the experimental drug. The other three studies two in patients without the ApoE4 gene and one in patients with it are all continuing, after review by an independent safety monitoring committee.
There's no known cure for Alzheimer's disease. Current medicines, including Pfizer's Aricept and Forest Laboratories' Namenda, temporarily ease symptoms such as memory loss, confusion and agitation. But they do nothing to slow, stop or reverse mental decline, leaving patients and their loved ones desperate for a new treatment.
Alzheimer's experts were disappointed by the news and said they still hope the drug will prove effective in other studies of people without the ApoE4 gene.
"I remain hopeful that we might see a more positive clinical result in the ApoE non-carriers, as they may have less brain pathology to reverse at the stage of mild-to-moderate dementia," said Dr. Reisa Sperling, a neurologist at Harvard-affiliated Brigham and Women's Hospital in Boston who is one of the leaders of the bapineuzumab studies.
However, the basis for hoping bapineuzumab works in people without the gene "unfortunately is pretty slim," said analyst Erik Gordon, a professor at University of Michigan's Ross School of Business. "Fortunately, Pfizer is carrying on despite the slimness of the hope for bapineuzumab because slim hopes are all the hope we have at this point for Alzheimer's."
Finding a drug that could at least slow the disease has become a sort of Holy Grail in the pharmaceutical industry. A successful medicine would be guaranteed to generate billions in annual sales, given the world's aging population.
Successful Alzheimer's drugs "could be the next Lipitors in terms of their size should they work ," says Bernstein Research analyst Dr. Timothy Anderson. But he noted that bapineuzumab and similar drugs have been viewed as "highly likely to fail and so far this assumption has been correct." In a note to investors Monday, Anderson pegged the probability of success at around 20 percent for the entire category, adding, "these initial results will naturally make investors more skeptical than they already are."
Lipitor, Pfizer's cholesterol fighter, was the world's top-selling prescription drug until it got generic competition in December. It had peak global sales of $13 billion several years ago.
Worldwide, about 35 million people already have dementia, and Alzheimer's is the most common type. In the U.S., about 5 million have Alzheimer's. Bapineuzumab is one of three experimental Alzheimer's drugs undergoing late-stage patient tests. All are being closely watched by doctors, patients, investors and analysts. The other experimental medicines are solanezumab, developed by Eli Lilly & Co., and Gammagard, made by Baxter International Inc.
Last Tuesday, Baxter reported at the Alzheimer's Association International Conference that a tiny study indicated its drug might help stabilize Alzheimer's for up to three years. Four patients who got the highest dose of Gammagard for three years showed no decline on memory and cognition tests, but a dozen others on different doses or shorter treatment times didn't fare as well.
Meanwhile, J&J last week said that detailed results of its two studies testing bapineuzumab will be presented at a neurology conference in Sweden in September.
Pfizer said in a statement that the test results from what's called Study 302 have been shared with government regulators and doctors conducting the study so that patients participating in all the studies can be notified.
"While we are disappointed in the topline results of Study 302, a more complete understanding of bapineuzumab and its potential utility in mild-to-moderate Alzheimer's disease will be gained following the availability of additional data," Dr. Steven J. Romano, Pfizer's head of primary care medicines development, said in a statement.
Bapineuzumab is an antibody-based drug that targets the beta-amyloid protein, the sticky plaque that clogs patients' brains and is believed to play a central role in development of Alzheimer's disease. Researchers are still analyzing the study's data on biomarkers spinal fluid and brain imaging to see if bapineuzumab had any effect on clearing amyloid. If so, that might lend support to trying the drug earlier in the course of the disease, before people have so much plaque that it causes symptoms. The biomarker results will be presented at scientific conferences this fall, Sperling said.
Biomarkers are genes or measurable characteristics that indicate a normal biologic process, a disease or a response to a treatment.
"I would defer complete judgment on the drug until I see some biomarker data," said Dr. Ronald Petersen, director of the Mayo Clinic's Alzheimer's Disease Research Center. "It still may leave the door open for some positive news if there are any biomarker movements."
Many scientists believe the drugs are being tried too late, "like lowering the cholesterol after the heart attack," said Petersen.
He had no role in these studies but consults for Pfizer on other potential Alzheimer's treatments.
Explore further: Key results coming on 3 drugs against Alzheimer's