Pfizer (NYSE:PFE) is an immensely large and complex pharmaceutical company. Last year, the pharma giant posted nearly $50 billion in annual sales across six different core therapeutic areas. 

Its jaw-dropping size can nevertheless act as a major impediment for investors trying to get a handle on the drugmaker's forward-looking prospects. A recent clinical update, for instance, revealed that Pfizer has a staggering 88 ongoing clinical trials in total, and 30 late-stage experimental candidates. 

Source: Pfizer

An unfortunate consequence of this clinical trial frenzy, however, is that many promising clinical candidates fail to get noticed by the investing community. With that in mind, let's take a deeper look at two of Pfizer's experimental therapies for rare diseases that deserve far more attention than they are receiving at present. 

Did you know Pfizer is a leader in the fight against Duchenne muscular dystrophy?
Unbeknownst to many investors, Pfizer is developing a myostatin inhibitor, PF-06252616, indicated as a potential treatment for the rare but devastating muscle wasting disease known Duchenne muscular dystrophy, or DMD. The drugmaker started enrolling patients in a midstage study for the drug late last year, and the trial should be completed in January 2017.  


Even though this experimental drug is a ways off from hitting the market, its staggering commercial potential should hold investors' collective attention for the long haul.

Because there are no approved treatments for DMD in the U.S. and PF-06252616 might help to improve clinical outcomes in a wide swatch of DMD subtypes, there is good reason to believe it could generate sales in the multibillion dollar range upon approval.

After all, BioMarin and Sarepta Therapeutics' most promising competing exon-skipping therapies target only about 13% of the DMD population, and this small fraction of the DMD population is already believed to have the power to generate around $500 million a year in peak combined sales for the two drugs.

Another interesting tidbit is that Pfizer's clinical candidate wouldn't necessarily compete with either of these exon-skipping therapies, if they are approved later this year. In fact, it might be used in conjunction with one of these drugs to further slow the progression of this fatal condition.  

Pfizer is hoping to develop a game-changing drug for Huntington's disease
Huntington's disease is a rare genetic disorder that causes the breakdown of nerves in the brain, leading to a whole host of terrifying symptoms like severe depression, psychosis, and degenerative motor skills.

Source: Wikimedia

Unfortunately, there are no approved treatments specifically for Huntington's, and most current pharmacotherapies used in the clinic today simply aim to alleviate symptoms arising from the disease.

Pfizer is presently exploring the safety and efficacy of its PDE10 Inhibitor, PF-02545920, as a treatment for motor impairment associated with Huntington's. Specifically, the drug is presently in a midstage study that is expected to readout in the third-quarter of 2016. 

Why is PF-02545920 worth keeping tabs on? This clinical candidate has the potential to be a game-changer for this rare condition, given that its therapeutic goal is to improve motor function. And if successful, it would essentially have the market all to itself. 

That said, Huntington's has proven to be extremely resistant to any form of pharmaceutical intervention, which is why numerous companies have completely abandoned their clinical programs for this disease over the years.  

So, PF-02545920 should definitely be considered a long shot. But the high unmet medical need in Huntington's means that any effective new therapy could rapidly turn into a blockbuster -- making PF-02545920 one of the pharma giant's more interesting clinical candidates for rare diseases.

Key takeaways
Pfizer's rare disease products often play second fiddle to the company's higher profile drugs in cardiovascular/metabolic care and oncology. However, they probably shouldn't be overlooked given that orphan drugs are undoubtedly going to be a major growth platform for the drugmaker in the decades to come. 

While the two clinical candidates for rare diseases mentioned above may both ultimately fail in clinical trials, they do demonstrate Pfizer's deep interest in the orphan drug arena. And why investors and the Street alike need to pay more attention to the drugmaker's concerted efforts to combat a diverse range of rare medical conditions.