The ability to develop game-changing new drugs that revolutionize patient care could cause shares in Axovant Sciences (NASDAQ:AXGT), Celldex Therapeutics (NASDAQ:CLDX), and Esperion Therapeutics (NASDAQ:ESPR) to soar. However, success may be tough to come by, and that makes investing in these stocks a boom or bust proposition.

Overcoming the odds?

Axovant is trying to do something that most biopharma companies have failed to accomplish: develop a new Alzheimer's disease drug. Alzheimer's disease is notoriously tough to tackle, and the success rate for developing drugs targeting it is absolutely disheartening. Historically, over 99% of Alzheimer's disease drugs entering clinical trials end up in the dustbin.

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Odds like that make investing in Alzheimer's disease drug developers like Axovant risky business, but there are two reasons why investors might want to lean optimistic. First, Axovant's C-suite includes Lawrence Friedhoff, who led the development of Aricept, one of the best-selling Alzheimer's disease drugs of all time. Second, Axovant's lead drug in development -- intepirdine -- is being studied for use alongside Aricept, rather than on its own.

In trials, Friedhoff's team successfully proved that Aricept can prevent the breakdown of acetylcholine, a neurotransmitter that's lacking in Alzheimer's disease patients, and now he hopes his team can prove that intepirdine boosts acetycholine production. If successful, then a combination approach of these drugs that increases acetylcholine levels and allows acetylcholine to last longer in the brain could become standard care.

According to, the estimated completion date for this combination study is October, so we should have data to examine before the end of this year. To be considered a success, the approach will need to meet primary endpoints measuring the change in baseline at 24 weeks on two Alzheimer disease measurement scales: the ADAS-Cog-11 and the ADCS-ADL.

Undeniably, the history of drug development in Alzheimer's disease suggests that Axovant's chances for success are small. However, the potential payoff could be tremendous. Axovant's market cap is only $1.1 billion, and prior to losing patent protection, Aricept's peak sales were $2.4 billion per year.

A big bet on a new way to tackle cancer

Celldex is developing glembatumumab vedotin, or glemba, a drug that could offer new hope to patients with a tough-to-treat type of breast cancer known as triple negative.

Triple negative breast cancer isn't the most common form of this cancer, but tens of thousands of patients are still diagnosed with it, and unfortunately, current treatments often fall short in tackling it.

Glemba hopes to change that by delivering a toxic drug payload directly to cancer cells. It does that by targeting a protein commonly over-expressed by cancer cells, binding to it, and then releasing chemotherapy that can kill the cell. It works similarly to Seattle Genetics' Adcetris, a drug that's already won FDA approval for use in a rare form of blood cancer. Celldex acquired licensing rights to Seattle Genetics' intellectual property when it bought CuraGen for $94.5 million in 2009.

Celldex hasn't said exactly when it expects to report data from its triple-negative breast cancer trial, but it has said that enrollment in its trial is continuing, and that results could be available this year.

If glemba is proven to be effective and safe, then it could gain approval pretty quickly, and if so, it could become a commercial success. A win like that would be a nice change for Celldex investors, many of whom lost money when a trial evaluating another one of its drugs fell short in brain cancer last year. Guess-timating peak sales is probably a fool's errand, especially since glemba's being studied in other indications that could significantly alter any projections, but industry watchers have said they think glemba could be a billion-dollar blockbuster. 

Catching lightning in a bottle (again)

Roger Newton isn't just Esperion Therapeutics' founder; he's also the person who developed Lipitor, the world's best selling cholesterol-busting drug, and the person behind the original Esperion Therapeutics, which got bought by Pfizer for $1.3 billion in 2003.

Nowadays, Newton's reassembled a lot of the "old" Esperion team at the current Esperion Therapeutics to see if they can knock bad cholesterol levels lower. The company's only drug in development is bempedoic acid, a phase 3 stage oral drug that can be used alongside traditional statins, like Lipitor, to reduce bad cholesterol levels. In phase 2 studies, adding bempedoic acid to statin therapy lowered bad cholesterol by about an additional 20%. 

Esperion Therapeutics is conducting a large phase 3 efficacy trial to confirm the phase 2 findings, and it's also running a cardiovascular outcome study that it hopes will prove that bempedoic acid improves patient outcomes. Earlier this week, management told investors that enrollment in the efficacy trial was completed in January, and that suggests that it will be able to report data sometime in 2018. The company continues to enroll patients in its outcomes study.

If the company delivers a win in its efficacy trial, its still a bit unclear whether or not FDA regulators will hold off on approval until the outcomes study is complete. In 2015, the FDA originally said bempedoic acid could win approval without the outcome data, however, the regulator later changed its tune, suggesting it would be required for it to win approval in anything but genetically caused cases of high cholesterol.

Nevertheless, any eventual approval of bempedoic acid could make it the biggest seller of all three of the drugs I've highlighted. Over 70 million Americans have high cholesterol, and despite widespread use of statins in tens of millions of Americans, heart disease remains the most common cause of death in the United States. At its peak, Lipitor was hauling in about $13 billion in sales annually, and if bempedoic acid ends up being prescribed alongside statins in most patients, Esperion Therapeutics could end up with a megablockbuster on its hands. 

However, there's no guarantee that the efficacy and outcomes data will be strong enough to convince regulators to approve bempedoic acid, and an outright failure in these trials could prove disastrous to investors because it's the company's only clinical-stage drug. Because this stock is a long shot, risk-averse investors might be better off looking elsewhere.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.