In the drug development world, no partnership is "until death do us part." Yesterday, specialty drugmaker AtheroGenics (NASDAQ:AGIX) announced that its development and commercialization partner AstraZeneca (NYSE:AZN) was ending the collaboration between the two companies on AGIX's lead compound, AGI-1067.

AstraZeneca decided to break up with AGIX and stop funding any future pre-commercialization development of AGI-1067 after negative clinical trial results from a pivotal phase 3 study were announced back in March.

Just in 2005 and 2006 alone, AtheroGenics spent over $150 million in research and development expenditures. Although AstraZeneca was not directly supporting clinical trials of AGI-1067, it would have been responsible for marketing and sales expenses had the drug made it through the FDA.

The loss of AstraZeneca does not bode well for AGI-1067's approvability, considering that continuing the small back-ended deal would be of minimal cost to a huge pharma like AstraZeneca. It's always possible that AGI-1067 is not dead in the water and could still potentially make it to market.

AtheroGenics is pinning its hopes on subgroup analyses from the AGI-1067 phase 3 trial that showed the drug candidate might be effective for certain patient populations. The problem with this is that the evidence of AGI-1067's effects is still very inconclusive (at best) even after the large phase 3 study. Waiting around for years on more clinical trial results for a drug with such unproven efficacy is not something that is a recipe for success with specialty pharma stock investing.

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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.