In an interview with Real Money, Biogen says its next step is to talk to regulators and bring the drug to patients.
"We're going to start these conversations (with regulators) as soon as reasonably possible, and we can't comment on any launch timing after that," says Samantha Budd Haeberlein, VP Clinical Development Late Stage Alzheimer's.
In an interview with CNBC, Biogen Chairman Stelios Papadopoulos said "we need to do a lot more" and it might be "two to three years" until an approved treatment reaches patients.
Biogen's BAN-2401 trial was an unusual breakthrough in the development of drugs to battle Alzheimer's disease, a field marked by a high failure rate.
"There has been a very determined effort, but we didn't have all the puzzle pieces in place to do the right clinical trial with the right molecule," says Haeberlein, who has been in the field for 18 years. "Now, with two molecules delivering these results, we feel we're getting closer."
Shares of Biogen jumped nearly 20%, to $357.48, on Friday. The NASDAQ Biotechnology Index Biotech Index gained 3.7% on the day.
When it comes to Phase III of the separate Aducanumab program, which also relies on an amyloid-reduction antibody, Biogen plans to complete recruitment for this phase in 2018, the company said. It will be an 18-month duration study.
Biogen relies on amyloid hypothesis in both trials. The company said "there are also other pathways of importance and we're working towards those" in its research into tackling Alzheimer's disease.
Development of the drug commenced in 2014, but the drug seemed on the verge of being scrapped at the end of 2017 when no significant clinical improvement emerged after a 12-month review.
Research for Alzheimer's drugs is marked by failure much more than other arenas of clinical trials, according to Dr. Thomas Wisniewski, head neurologist at NYU Langone Medical Center in Manhattan.
The second phase trial is encouraging because results indicate a "proof of concept" that correlates Biogen's long focus on amyloid proteins as a cause of the disease and improvement among patients.
"There have been a lot of issues in design of clinical trials: it is hard to know what the best targets are in amyloid treatments and at what point in the disease to begin a treatment," Wisniewski says.
What Biogen Got Right
One of the reasons previous trials have failed is because they have included patients at a later stage of disease development, Biogen's Haeberlein explains.
A crucial component of getting this right, according to Biogen's VP of Clinical Development, was "including patients at early stage, before the brain had too much destruction."
All the patients were tested for the presence of amyloid plaque, which is also something that wasn't always done in previous trials, according to Haeberlein, commenting on previous failures.
"They had patients in the trial who were not responding to the drug because they weren't actually Alzheimer's patients," she says. "The earliest symptoms of Alzheimer's disease might actually not be accurately diagnosed as Alzheimer's disease. You need to confirm that they have the presence of amyloids."
'This Gives Us Hope'
Nobody outside the company has seen the full set of data, Biogen confirms, noting the full results of the study will be announced at future academic conferences.
Eisai did not respond to an email or phone number requesting comment.
"The scientific community does need to see the full set of data, and one needs to be cautious in interpretation," says Wisniewski, noting the trial used a small number of patients. "We are eager to find a disease-modifying agent for Alzheimer's disease, so this gives us hope."
-- Martin Cassidy and Alexander Nicoll contributed to writing this article
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