Drug development is a risky enterprise on its own. Advancing a safe and effective therapy for Alzheimer's disease (AD) is like trying to shoot the moon with a slingshot, blindfolded. The exact mechanism behind the formation of memories isn't entirely clear, and the exact cause of their destruction is even cloudier. Flush with cash from the successful launch of Tecfidera, Biogen Idec (BIIB 0.38%) is taking a shot at one of the largest unmet needs in medicine.
There are no drugs that can effectively prevent the progression of AD. Attempts to develop the first have been met with one expensive failure after another. Partners Pfizer and Johnson & Johnson lost big when bapineuzumab failed a Phase 3 trial with mild-to-moderate patients. Few were surprised when Eli Lilly (LLY -0.01%) announced a similar Phase 3 failure with solanezumab.
Undaunted, Biogen Idec has recently upped its commitment in the AD field. The neuroscience specialists inked a collaboration pact with Japan's Eisai over the development of several compounds. The most notable is E2609, an oral BACE inhibitor. After the failure of high-profile antibodies like bapineuzumab and solanezumab, these small-molecule drugs are getting all the attention in the race to treat AD.
Leading the race
Despite the trail of wasted R&D resources AD has left in its wake, there is no shortage of companies making attempts. Leading the charge is Merck (MRK 0.15%) with its BACE inhibitor MK-8931.
The candidate is in a Phase 2-3 study with mild to moderate AD patients. Late last year, an independent data monitoring committee finished a planned interim safety analysis of the trial. Merck and its competitors breathed a collective sigh of relief when the committee gave the green light. The trial can now continue recruiting patients without changing its design.
Any safety analysis is stressful in mid to late-stage development, but Merck's was more of a nail-biter than most. Last June, Eli Lilly voluntarily terminated a mid-stage study with its BACE inhibitor, LY2886721, due to "abnormal liver biochemical tests," although the same press release indicated that Lilly "believes that the abnormal liver biochemical tests...are not related to the BACE mechanism." Last fall, Roche quietly terminated development of a BACE inhibitor it had in early stage clinical trials as well. Unlike Lilly's BACE dismissal, Roche cut its program silently without giving any clues as to why. Hot on the heels of Lilly's announcement, some probably feared that Roche's withdrawal, and in turn all BACE inhibitors, might cause liver damage.
Now that Merck's BACE inhibitor has shed safety concerns, confidence in this promising class of AD therapies should get a nice boost. The race to win the first approval should heat up as well. Luckily Biogen Idec won't be starting from zero. Eisai's, and now Biogen's, E2609 was "undergoing preparations to enter Phase 2 clinical trials" when the companies announced their collaboration.
Clearing a path
Also boosting confidence for this therapy class, and AD in general, is a new attitude from regulators. Previously the FDA insisted on measurement of a patient's ability to function. If patients without AD symptoms are treated, however, changes in their functional ability might be nearly impossible to measure. Just over a year ago, the agency issued a new draft guidance for the industry. It has gone a long way to define a path to approval for drugs that slow the progression of AD before patients show any symptoms of the disease. The pathway isn't so well defined yet, but the agency is clearly willing to accept new approaches for measuring efficacy.
What to look for
Personally, I wouldn't be surprised if Merck's late-stage trial with MK-8931 doesn't result in an approval. I don't think there's anything that's anything inherently wrong with the drug, but I worry that the patients with "moderate" AD symptoms may not improve, and that result would mar the trial's efficacy data. That would put Biogen not so far behind with E2609, which is now entering a Phase 2 trial.
Keep your eyes open for a long-term pivotal trial involving subjects that are at risk but not yet displaying AD symptoms. The first to enter such a trial, with endpoints developed according to FDA guidance, may win the BACE race.