Not all of big pharma's drug approvals or rejections get much public notice. For instance, yesterday Sanofi-Aventis' (NYSE:SNY) and partner Bristol-Myers Squibb's (NYSE:BMY) attempts to bring a new version of lead drug Plavix to market in the European Union got shot down.

Sanofi and Bristol wanted to gain approval for a combination treatment of aspirin and their blockbuster heart-disease drug. Patients commonly take both of these compounds separately; by combining them, Sanofi and Bristol hoped to reduce pill burden and improve patient convenience and compliance.

Technically, Sanofi and Bristol withdrew their marketing applications (PDF) for their Plavix-and-aspirin combination. This commonly occurs in the EU whenever the European Medicines Agency requests new information that a drugmaker either doesn't have at the time, or knows would lead to an eventual EU rejection. In this case, the agency wants proof that the addition of aspirin doesn't change the amount of Plavix in the bloodstream. The drugmakers plan to provide it -- eventually.

This marketing application was likely part of a strategy to extend the sales life cycle of Plavix, differentiating it from potential upcoming generic versions of the drug that could reach EU markets this year. Every large-cap pharma develops combination therapies or extended-release versions of their soon-to-be genericized drugs, hoping to eke out some incremental sales. Witness Pfizer's (NYSE:PFE) combination treatment for high cholesterol and high blood pressure, Caduet, which combines its lead drug Lipitor with its recently genericized Norvasc, or GlaxoSmithKline's (NYSE:GSK) introduction of an extended-release version of its Coreg heart drug last year to fight generic competition for the immediate-release version.

With so many moving parts, large-cap pharmas can sometimes be very difficult to value. They don't have to report on all the happenings with their compounds if they deem those events immaterial -- even if investors think otherwise. Thankfully, the European Medicines Agency provides investors another outlet to help track the latest news on both the most important and lesser compounds in a drugmaker's pipeline.