By Randall Osborne

Two months after the FDA decided to regulate ultrasound contrast agents as drugs rather than medical devices, causing a U. S. District Court to lift the injunction that had kept the FDA from reviewing them, Sonus Pharmaceuticals Inc. has scored a vote of confidence from the agency.

Sonus, of Bothell, Wash., has been notified by the FDA that a meeting of the Medical Drug Imaging Advisory Committee will not be necessary to continue the review of the company's new drug application filed in September 1996 for EchoGen, an emulsion designed to improve ultrasound images.

The decision means the FDA is satisfied with EchoGen trial data presented by Sonus and will not ask outside advisors for their evaluation, but Terry Willard, vice president of marketing and business development for Sonus, declined to speculate on when the FDA might approve the product.

EchoGen is a stable, liquid emulsion that changes from microscopic liquid droplets of dodecafluoropentene to gas microbubbles during administration. "It's drawn up into a syringe, activated and injected into a peripheral vein," said Willard.

The emulsion's bubbles are smaller than red blood cells, allowing them to pass easily through capillaries of the lungs and other organs, providing more precise sound-wave reflectivity, hence better images. EchoGen is "a blood flow tracer, effectively," Willard said. It is the first fluorocarbon-based ultrasound contrast agent to complete clinical trials for cardiology and radiology applications in the U.S.

Sonus' stock (NASDAQ:SNUS) closed Thursday at $44.375, up $3.375. *