Pfizer Inc research chief Mikael Dolsten said the company's experimental treatment for is the drug industry's "best chance" to delay progression of the memory-robbing illness.
Dolsten, speaking at the BIO CEO and investor conference in New York, stopped short of predicting whether the drug being developed with Johnson & Johnson would meet that goal.
"This is so far the best chance the industry has for disease modification in Alzheimer's," he said. Dolsten said Pfizer's drug, bapineuzumab, had far more complete and compelling data from already finished mid-stage clinical trials than Eli Lilly and Co's solanezumab.
Both companies plan to release Phase III data in the second half of this year from their respective large trials. The drugs are meant to be the first to slow progression of Alzheimer's, a disease that affects an estimated 5 million Americans and more than 35 million people worldwide.
"Bapineuzumab was the only one of these two that had significant Phase II data," Dolsten said, referring to the relatively brief 12-week trials Lilly conducted on solanezumab before moving it into large late-stage studies.
By contrast, Pfizer's Phase II studies of bapineuzumab lasted 18 months, better enabling Pfizer to pick appropriate doses of the medicine in far larger ongoing Phase III studies.
But mixed results were seen among patients receiving bapineuzumab in those smaller earlier studies. Patients in one mid-stage trial had an almost 25 percent lower accumulation in the brain of amyloid plaques -- a suspected cause of Alzheimer's disease -- than those receiving placebo injections. But they achieved no cognitive benefits. And patients receiving high doses of the Pfizer drug in another mid-stage study had worrisome brain swelling.
Asked in a recent interview if Lilly's short Phase II studies might hurt its drug's chance of succeeding in bigger Phase III trials, Dr. Eric Siemers, head of Lilly's Alzheimer's program, said, "The jury's still out; we don't know if it was the right choice."
But Siemers told Reuters the shorter trials enabled Lilly to get solanezumab into late-stage trials far more quickly and at far less expense, hopefully without compromising future results.
Many investors consider bapineuzumab and Lilly's rival injectable drug long shots because they treat patients that already have developed mild to moderate symptoms, such as memory loss and inability to perform daily chores, and therefore may have suffered irreversible damage to neurons and brain tissue.
Dolsten cautioned that would probably need to be treated at earlier stages of the disease to produce the most beneficial results, a prospect he sees likely within the next five years.
Pfizer is counting on newer drugs to deliver revenue needed to offset plunging sales of its Lipitor cholesterol fighter, which has faced cheaper generics since November.
They include Prevnar 13, an improved form of its Prevnar vaccine to prevent infections with streptococcus bacteria. The U.S. Food and Drug Administration in December approved its use for adults aged 50 and older, greatly widening the market for the product, which had been approved only in children.
Dolsten said Pfizer expects data by next year from late-stage trials testing whether Prevnar 13 prevents pneumonia in adults. The $3.3 billion-a-year vaccine could get a big commercial boost if the trials succeed, especially in preventing pneumonia among the elderly, he said.
The world's biggest drugmaker also has high hopes for tofacitinib, an experimental pill that treats rheumatoid arthritis through a new approach and is awaiting U.S. approval.