Go ahead and call me crazy. If I were of sound mind, wouldn't I give reasons to sell Alexion Pharmaceuticals (Nasdaq: ALXN) rather than buy? After all, the stock is trading at a triple-digit P/E. The company has been described as a "one-trick pony." Its one commercial product targets diseases that affect only one to three people per million annually.

I might be crazy, but I actually think there is a good case to be made for buying Alexion now. Here are three reasons.

1. Blue ocean of rarity
Several years ago, the book Blue Ocean Strategy hit the business best-seller lists. The main premise of the book was that organizations should focus on "blue oceans" -- markets with no competition.

Alexion swims in the blue ocean of rarity. The company focuses on treatments for ultra-rare diseases where no other drug treatments exist. Alexion's Soliris currently targets two of these diseases -- paroxysmal nocturnal hemoglobinuria (PNH) and atypical hemolytic uremic syndrome (aHUS).

PNH is a disease where red blood cells break down earlier than normal. The exact number of people with PNH is unknown, but estimates range from 10,000 to 21,000 in North America and Europe.

aHUS is a life-threatening genetic disease affecting the immune system. The number of aHUS cases in the U.S. is believed to only be around 300.

With such low customer bases, you might think Alexion operates in a blue mud puddle rather than an ocean. An estimated additional 1,700 people are diagnosed with PNH each year in North America and Europe. That perhaps promotes the market to blue pond status.

However, keep in mind that Soliris is the world's most expensive drug. Alexion reportedly makes over $400,000 per year per patient taking the drug.

If the low end of the estimated range of patients suffering from PNH is accurate, the disease represents a $4 billion market potential in North America and Europe alone. And that potential market grows by around $680 million each year. Alexion's 2011 total revenue was only $783 million.

2. Ponies can learn new tricks
Sure, Alexion can legitimately be called a one-trick pony right now. Its only commercial product is Soliris. But ponies can learn new tricks.

Clinical trials are currently under way for potential use of Soliris in treating several other diseases beyond PNH and aHUS. Alexion has already received orphan drug designation in Europe for treating STEC-HUS. It also points to encouraging preliminary results from a phase 2 trial of Soliris in treating myasthenia gravis (MG).

Another new, less-positive trick for Alexion could be facing direct competition in one of the markets it is hoping to enter with Soliris. Regeneron Pharmaceuticals (Nasdaq: REGN) makes Eylea, a drug used for treating age-related macular degeneration (AMD). Eylea received FDA approval in late 2011 and chalked up sales topping $317 million in the first six months of 2012.

Alexion is expanding via acquisitions also. Earlier this year, it bought Enobia Pharma. Enobia's primary drug targets patients suffering from hypophosphatasia (HPP). There are currently no approved treatments for HPP.

The company clearly has its sights set on moving into other rare-disease markets. While these efforts could prove to be unsuccessful, they present very feasible added growth paths for the company.

3. Shopping for drugs
Pharmaceutical companies love to go shopping. The Pharma Letter tallied 129 mergers and acquisitions in 2011, up from 117 in 2010. While Alexion has done some shopping of its own in the past couple of years, the company could be on the wish list for larger pharmaceutical companies.

Goldman Sachs added Alexion to its list of potential acquisition candidates earlier this year, calling it "one of the most attractive stories in biotech." Louis Navellier, investor and author of The Little Book That Makes You Rich, also says that the company would be a good acquisition target.

Several major pharmacy companies face expiration of drug patents and have plenty of cash to beef up their portfolio. Pfizer (NYSE: PFE) is one potential buyer that comes to mind. Pfizer's cash and equivalents top $24 billion, putting the company in good shape to make an acquisition.

Merck (NYSE: MRK) is another company facing the patent cliff that might look to make an acquisition. It has a cash stockpile totaling more than $17 billion. Amgen (Nasdaq: AMGN) also could be in the market. The company's cash and equivalents currently stand at $22.48 billion.

Go crazy
Am I crazy to think that buying Alexion makes sense? Maybe.

On the other hand, the company could very likely continue its core growth and expand into treatments for other rare diseases largely unfettered by competition. That would fuel its continued momentum. A bid from another major player would really turbocharge the stock.

If these scenarios play out, Alexion stockholders will be the ones going crazy.

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