Drug delays can torpedo the share prices of many development-stage pharmaceutical companies. Now Medarex (Nasdaq: MEDX) finds its own stock sinking, after it and partner Bristol-Myers Squibb (NYSE: BMY) announced a delay for its lead drug, ipilimumab.

Medarex shares fell 10% following the late Friday press release that broke the news. The company originally planned to file an FDA marketing application for ipilimumab in the first half of this year, as a potential treatment for late-stage melanoma. That timeline's now off the table, with no new one provided, after the FDA requested more overall survival data for the drug.

In conjunction with the FDA's request, Medarex is also changing the primary endpoint of an ongoing ipilimumab phase 3 study, which previously measured progression-free survival (PFS). This criterion combines survival with other disease measurements, and it can significantly speed up a drug candidate's progress through clinical testing, since its results can be measured much more quickly than overall survival data.

Medarex has financial interests in a whole slew of drugs in development, from its in-house developed compounds to drugs being worked on by partners or licensees of its technology. The company claims to have "over 40 compounds" based on its technology platform in human clinical trials at the very least. Its lineup includes Johnson and Johnson's (NYSE: JNJ) CNTO-1275 (ustekinumab), currently awaiting an FDA marketing decision, and drugs from other large pharmas like Novo Nordisk (NYSE: NVO).

Even with all these potential revenue-generating compounds in development, Medarex's near-term fortunes remain highly tied to ipilimumab. It's the company's most developed pipeline candidate, and its only in-house compound in late-stage phase 3 testing. Given those facts, it's impossible to put this extra delay in any positive light.

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Fool contributor Brian Lawler does not own shares of any company mentioned in this article. Johnson and Johnson is an active Income Investor pick. The Fool has an A+ disclosure policy.