Image source: Eli Lilly & Company.

Eli Lilly & Company (NYSE:LLY) will host an investor day on Dec. 8 and its Alzheimer's drug pipeline is one of the topics the company plans to cover in its presentation. Because there's a huge need for new Alzheimer's disease therapies, any insight into a timeline for Eli Lilly's therapies could move its shares higher or lower.

First, a bit of background
Unfortunately, Alzheimer's disease is the only one of the top 10 leading causes of death in America that can't be prevented, delayed, or cured.

Treatment of Alzheimer's disease is typically palliative and drugs like Aricept, the most commonly prescribed therapy, lose their efficacy over time.

Making matters more pressing is the fact that an estimated 5.2 million people suffer from Alzheimer's disease and as many as 7.1 million Americans will be diagnosed with it by 2025, according to the Alzheimer's Association.

The problem is even greater globally given that there are about 7.7 million new cases of dementia diagnosed every year and 60% to 70% of them are cases of Alzheimer's disease, according to the World Health Organization.

Advancing treatment
Major drug companies like Eli Lilly and Biogen (NASDAQ:BIIB) are investing heavily in Alzheimer's disease research in hopes of tapping into what is undeniably going to be a multibillion-dollar market.

Solanezumab is the most advanced drug in Eli Lilly's Alzheimer's disease program and investors should pay attention to whether Eli Lilly's management offers up an update on solanezumab's ongoing phase 3 trial because solanezumab, which binds to and destroys amyloid plaque buildups thought to be a cause of Alzheimer's disease, has had its share of setbacks in the past, including late stage trial failures.

After solanezumab failed to outperform placebo in boosting cognition in previous phase 3 studies, Eli Lilly conducted a post-hoc analysis that determined that solanezumab may work in mild to moderate cases of Alzheimer's disease.

That revelation led to the company designing its current phase 3 trial to include 2,100 patients who score between 20 and 26 at baseline on the Mini-Mental State Examination (MMSE), a cognitive impairment test. For comparison, patients in solanezumab's prior failed studies were allowed to participate if they scored between 16 and 26 on the MMSE.  

We won't find out whether narrowing the patient population down in this manner will allow solanezumab to demonstrate cognitive benefits this time around until next year, but data presented earlier this year was mixed.

At the 28-week mark, patients with mild to moderate Alzheimer's disease who participated in previous trials and newly enrolled patients were evaluated and Eli Lilly found that the group that began taking solanezumab more recently hadn't caught up to the prior group of solanezumab patients on cognition and brain function -- a finding that may indicate solanezumab alters disease progression, rather than simply treats the symptoms of the disease.

However, Eli Lilly also reported that solanezumab patients had yet to demonstrate improvement in cognition and function versus placebo and if that continues throughout the study, then it could derail solanezumab's chances for approval.

Image source: Biogen.

Racing ahead
If Eli Lilly's phase 3 data is solid, it could give it an edge in reaching the market over Biogen's Alzheimer's drug, BIIB-037 (aducanumab), which also targets beta amyloid plaques.

Earlier this year, Biogen reported that 166 aducanumab patients were outperforming placebo on cognition after one year in a phase 1b trial and that first-in-class finding caused Biogen's shares to soar.

However, enthusiasm for Biogen slipped after investors realized the benefit was achieved on the highest 10 mg dose of the drug and that the 10 mg dose was associated with worrisome adverse events, including brain swelling.

In an attempt to find a safer but equally efficacious dose, Biogen tested a 6 mg dose that, unfortunately, failed to produce the same benefit as the 10 mg version.

Biogen's trial remains ongoing and as data matures anything could happen, including positive efficacy for lower doses, but we won't get a definitive answer on aducanumab's efficacy and safety until 2018 and that means that Eli Lilly has a chance for a multi-year head start in this market.

Foolworthy takeaway
Because a staggering 99% of Alzheimer's drugs entering human trials have failed, the bar is set pretty high for both Eli Lilly and Biogen. However, if Eli Lilly can overcome those odds and finally prove that solanezumab works, it could win FDA approval for solanezumab in 2017, and if so, solanezumab could be in the pole position to catch a big chunk of what industry watchers believe will be a megabillion-dollar market. For that reason alone, investors might want to tune into Eli Lilly's presentation next week.