There are basically two times in a drug's development when biotech investors can expect to see some huge volatility in the value of their shares. One occurs whenever pivotal phase 3 trial results are released, and the other happens whenever a drug is up for regulatory review and possible approval.

Palo Alto, Calif.-based biopharmaceutical company CV Therapeutics (NASDAQ:CVTX) just moved a step closer toward both of these periods today, with the announcement that a pivotal trial for its lead drug, Ranexa, to treat chronic angina is nearing completion, and that the trial results will be released in the first quarter of 2007.

Ranexa was approved earlier this year to treat angina if and when other standard therapies prove effective. CVT has been running another trial with the drug, code-named Merlin, to hopefully expand Ranexa's label as a front-line treatment for angina, and possibly as a treatment for other acute coronary syndromes.

CVT smartly negotiated a special protocol assessment with the FDA for this Ranexa trial. If patients taking the drug show no elevated risk of death compared to placebo, then the FDA will most likely give Ranexa the sought-after label to treat first-line angina.

The Merlin trial is not a timed trial ending on a specific date, but rather one that is event-driven. When a certain number of deaths and cardiovascular events are reached, the trial will end. It was previously expected to be completed and unblinded earlier this year, but trial participants are taking longer than expected to reach these events.

Whether the postponed unblinding of the study results is a good omen or bad one is really just speculation. The extended time of the trial could be due to the placebo patients being much healthier than expected, thereby giving Ranexa a higher hurdle to overcome to show a survival advantage, or it could be due to the drug improving outcomes so much so that only placebo patients are having the cardiovascular events. It makes sense that the longer trial could be due to either of these theories, a combination of the two, or something else completely.

Ranexa sales for the most recent quarter were only $1.2 million, but these results were particularly affected by the drug's launch late in the quarter. Unfortunately, prescription trends for Ranexa have not been growing quickly lately, which doesn't bode well for the drug's success -- unless it can get that improved label from Merlin as a front-line treatment for angina.

CV Therapeutics does have more drugs in its pipeline than just Ranexa, but none of the company's other drugs has the potential to become a blockbuster. Barring some unforeseen drug development at CVT, I'll be biding my time counting down the days until the company releases the Merlin results -- and meets its date with destiny.

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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.