Biopharmaceutical company CV Therapeutics ( CVTX) was downgraded by Morgan Stanley Wednesday morning on concerns about the market for one of its new drugs. The brokerage firm cut its rating on CV Therapeutics to underweight from overweight, saying it believes the stock has reached its maximum price until the Food and Drug Administration approves the company's angina treatment Ranolazine. Morgan Stanley said it expects FDA approval for the drug in late 2003. Additionally, Morgan Stanley expressed some concerns over the market opportunity for Ranolazine, as the drug might be forced to carry a prominent warning label highlighting risks associated with increases in the QTc interval, a measurement on the electrocardiogram that represents the interval between the contraction and the repolarization of the left ventricle of the heart. QTc prolongation has been associated with arrhythmias in previous studes. CV Therapeutics was recently falling 17.4% to $20.15 on the downgrade after closing at $24.40 Tuesday.