On Friday, drug maker Alexion Pharmaceuticals (NASDAQ:ALXN) announced that the European Union drug regulatory body had recommended its lead compound, the blood disorder treatment Soliris, for marketing approval in the EU countries.

Soliris already has marketing approval to treat this blood disorder, paroxysmal nocturnal hemoglobinuria (PNH), in the U.S.; the Food and Drug Administration gave the drug the thumbs-up in March. The drug approval process in the EU differs slightly than in the U.S., but the positive EU recommendation virtually guarantees that Soliris will receive formal marketing approval when a final decision is rendered in two to three months.

It will probably take about a year for Soliris to negotiate reimbursement in the more than a dozen EU countries and for meaningful sales to start coming in. But now that Soliris has marketing approval in the major pharmaceutical markets, Alexion has finally overcome the pharmaceutical development-stage phase.

Alexion is going to market Soliris by itself in the EU and U.S. The market opportunity for Soliris will be relatively tiny, at an estimated 8,000 to 10,000 patients in Western Europe and North America with PNH -- but Alexion won't have any competitors for this indication.

With no other compounds in clinical-stage development, an investment in Alexion is all about the market potential for Soliris. So now investors will be watching if Alexion's management team can prove to be as adept at marketing and cost control as they are at the drug development process in order to justify the company's $1.5 billion valuation.

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Fool contributor Brian Lawler does not own shares of any company mentioned in this article. The Fool has a disclosure policy.