The Food and Drug Administration gets a lot of information in the marketing applications submitted by drug companies. Most of the data is routine and it's usually the clinical trial data that's the make-or-break issue for the decision. But every so often it's manufacturing issues that trip up the approval.

Unfortunately for Bristol-Myers Squibb (NYSE:BMY) and Eli Lilly's (NYSE:LLY) newly acquired ImClone Systems, the companies' new application for oncology-drug Erbitux seems to be one of those cases. On Friday, they withdrew their application to extend the approval of Erbitux to treat lung cancer. Apparently, the companies are having a hard time convincing the FDA that the version sold in the U.S. is the same as the one used in the lung-cancer clinical trial that was run by ImClone's partner, Merck KGaA, which sells Erbitux outside North America.

Welcome to the club.

Or in Lilly's case, welcome back. Lilly and partner Amylin Pharmaceuticals (NASDAQ:AMLN) have run into related issues over their diabetes drug Byetta. In that case, the companies saw the problem coming and seem to have an alternative solution. Genzyme (NASDAQ:GENZ) has had a similar problem convincing the FDA that its enzyme replacement Myozyme made at a larger scale is the same as the drug that was originally approved. Smaller companies, such as Discovery Labs and AMAG Pharmaceuticals (NASDAQ:AMAG), have also had manufacturing issues hold up approvals of their drugs.

The good news is these things almost always get resolved -- eventually. It's impossible to change clinical trial data, but manufacturing issues can be dealt with.

Bristol-Myers and Lilly didn't say exactly what the issue was or how long the delay might last, but the companies would be smart to get the problem wrapped up and resubmit quickly. With clinical-trial data that was good enough for approval, but not enough to knock the socks off doctors, a delay just makes clinicians more comfortable with using the drugs already on the market, like Genentech's (NYSE:DNA) Avastin, and Genentech and OSI Pharmaceuticals' (NASDAQ:OSIP) Tarceva.

You better get hopping, Bristol-Myers and Lilly.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. The Fool has a disclosure policy.