Though the company isn't releasing the numbers yet, Texas Biotechnology Corp. said it achieved statistically significant efficacy results after enrolling just 24 patients in a three-armed Phase IIa trial of its congestive heart failure drug, TBC11251.

"We think [the news] is very good," said David McWilliams, president and CEO. The compound "performed very much as we expected it would."

The Houston firm called an early halt to the double-blind, randomized trial, which pitted high and low doses against placebo. The study was designed to recruit up to 45 patients with severe CHF, but met a key endpoint with just over half that number by significantly improving central hemodynamics, particularly pulmonary artery pressure.

Texas Biotechnology now will move on to different intravenous dosing regimens, and also plans to study an oral version of the drug in the same model.

A synthetic small molecule blocker of endothelin A receptors, TBC11251 is the first such compound to demonstrate efficacy in heart failure patients. If it succeeds, it will provide a complement to the standard therapy of angiotensin-converting enzyme (ACE) inhibitors.

ACE inhibitors work on the left side of the heart, while the company's endothelin blocker is designed to relieve pressure on the right side.

"Based on this initial data, the drug should be very synergistic with ACE inhibitors," said McWilliams.

TBC11251 is one of several small molecule drugs targeted against vascular diseases under development at Texas Biotechnology. The program's most advanced drug candidate is the anticoagulant Novastan, now under review for marketing approval at the FDA.

Texas Biotechnology's shares (AMEX:TXB) closed Wednesday at $6.312, up $0.375. — Debbie Strickland