Investors punished CV Therapeutics Inc. on Friday's announcement that the company will enroll additional patients in its second Phase III trial of ranolazine, treating the news as if it were just another case of a biotech company trying to manipulate a failing study. But in its defense, the company says it had prospectively built in the possibility of adding more patients as a precautionary move to maintain the power of the trial.

The CARISA trial (Combination Assessment of Ranolazine in Stable Angina) is testing ranolazine, a pFOX (partial fatty acid oxidation) inhibitor, in combination with other anti-angina drugs in patients with chronic stable angina. The trial has completed enrollment of the originally planned 462 patients, but an interim assessment, which