Washington Editor

ImaRx Therapeutics Inc., which is working on anti-clotting therapies, filed for an estimated $75 million initial public offering and is seeking the Nasdaq symbol "IMRX."

The number of shares and the price range have not been disclosed, but in an SEC filing, the company said the lion's share of the funds would be used for developing its thrombolytic drugs and SonoLysis therapy. Specifically, about $22 million is tabbed for continuing the clinical development of those two programs for ischemic stroke and other vascular disorders. Another $14 million would be used to fund contract manufacturing.

The clot-dissolving drugs are variants of urokinase, a natural human protein that stimulates the body's clot-dissolving processes. In that portfolio is Prolyse, a recombinant pro-urokinase believed to remain inactive until it reaches a clot, potentially reducing bleeding risks.

A Phase III study showed it to be well tolerated and demonstrated its activity in dissolving cerebral blood clots when administered as long as six hours after the onset of stroke symptoms, and ImaRx plans to begin another Phase III trial next year. The company also has rights to an approved urokinase product, Abbokinase, which it plans to begin selling in the second half of this year for acute massive pulmonary embolism.

ImaRx said worldwide annual sales of thrombolytics total about $500 million. It acquired Prolyse, Abbokinase and related recombinant urokinase drug technologies in the past year from Abbott Laboratories, of Abbott Park, Ill., as well as Open-Cath-R, another form of urokinase being developed to clear blocked intravascular catheters. ImaRx is looking to out-license the latter, which has been in two Phase III trials.

The company's SonoLysis therapy employs a technology to break blood clots apart by applying ultrasound to its submicron-sized SonoLysis bubbles, a mechanism of action that could be used alone for treating clots or in tandem with thrombolytics. A Phase I/II dose-escalation trial for ischemic stroke is scheduled to begin in the first half of next year to test the SonoLysis bubbles on their own, as is a trial to test the combination of SonoLysis with the thrombolytic tPA (tissue plasminogen activator). That latter study potentially could pave the way for a later combination study with Prolyse.

Other IPO-generated funds are projected to be used to pay down existing debt, for working capital and other general corporate purposes.

The company was founded in 1999 and has since funded operations with venture capital backing and debt financing. ImaRx had $6.3 million in cash and cash equivalents as of March 31, after which it added $13 million in private equity financing. There are 42 full-time employees.

Principal stockholders include President and CEO Evan Unger, who controls 12.5 percent; John Moore, former chairman and executive vice president, with 8.6 percent; and Edson Moore Healthcare Ventures Inc., a Wilmington, Del.-based group, with 7 percent.

The IPO's underwriters are CIBC World Markets Corp., Jefferies & Co. Inc. and First Albany Capital Inc., all of which are in New York.