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ImaRx Therapeutics Inc., which to date has focused much of its resources developing its microbubbles-plus-ultrasound SonoLysis therapy for ischemic stroke, is shifting its priorities in an effort to reduce cash flow and alleviate the immediate need for additional financing.

The firm, instead, plans to focus on building the market for urokinase, an approved clot-busting agent initially acquired from Abbott in 2006.

The move came nearly a month after the Tucson, Ariz.-based firm decided to halt enrollment in its dose-escalating Phase I/II study of SonoLysis after interim data from the second cohort indicated a greater incidence of intracranial hemorrhage in patients receiving SonoLysis therapy - comprised of MRX-801 microbubbles plus ultrasound therapy - in combination with tissue-plasminogen activator (tPA).

While further study details are expected later, ImaRx has speculated that the addition of tPA, which, by itself, sometimes is known to cause bleeding, might have attributed to the safety issue. (See BioWorld Today, Jan. 7, 2008.)

"We'd planned to continue the [SonoLysis] program, absent tPA," said Bradford Zakes, ImaRx's president and CEO. But, in order to open an investigational device exemption (IDE) for clinical testing, the company first would have to complete a number of preclinical studies, he added.

"When management and the board sat down to look at that program, we saw the amount of work needed, plus the amount of financing needed" and opted, instead, to seek alternative strategies for further SonoLysis development, Zakes told BioWorld Today, adding that potential alternatives could include a big pharma partnerships or a merger and acquisition opportunity.

Maintaining adequate financing has been a bit of a struggle for ImaRx over the last few years.

The company went public in July with a $15 million initial public offering, despite earlier hopes of raising as much as $75 million. Lack of funding also prompted ImaRx to return rights to two late-stage urokinase candidates, both of which also were acquired in the 2006 transaction with Abbott. (See BioWorld Today, July 26, 2007.)

As of Sept. 30, the firm had about $16 million in cash, equivalents and investments. ImaRx said existing cash would have funded operations under its previous SonoLysis development plan through the third quarter of this year, but continuing SonoLysis trials would have required another financing round before then.

"We made a decision to mitigate that financing," Zakes said, "and we elected to conserve existing cash and focus" on urokinase, which is marketed in acute care hospitals for acute massive pulmonary embolism.

In its deal with Abbott, ImaRx gained all assets related to urokinase, including a four-year supply of inventory, as well as cell lines and manufacturing rights. Overall, the company's got more than "$40 million in urokinase inventory they will begin trying to monetize," Zakes said, and that will necessitate an increase to the company's sales and marketing infrastructure.

Earlier this month, the company signed a letter of intent with Toronto-based Microbix Biosystems Inc. to manufacture urokinase, and the companies also agreed to explore the drug's use in other indications. And the FDA also recently approved ImaRx's lot release request with an extended expiration dating.

To date, annual sales of urokinase have been "north of $12 million," Zakes said. But Abbot had grown sales to $40 million when it last sold the drug in 2002, "so we believe there is substantial opportunity."

Zakes said ImaRx also remains optimistic about the potential of SonoLysis. Though the Phase I/II ended prematurely due to safety concerns seen in the second cohort of patients, earlier data from the first cohort, which tested a smaller dose of the MRX-801 microbubbles plus ultrasound and tPA in 12 patients, showed "encouraging results," with no accompanying safety issues. In that first cohort, patients getting MRX-801 demonstrated signs of increased blood flow in the occluded artery and showed clinical improvements, as measured by the Modified Rankin Scale, 90 days after treatment.

The MRX-801 microbubbles are designed to work by penetrating the blood clot and releasing energy that works with ultrasound to break up the clot. The goal is to create a therapy that can offer patients a wider treatment window than tPA, which requires treatment within three hours of suffering an ischemic stroke.

Shares of ImaRx (NASDAQ:IMRX) lost 21 cents Wednesday, closing at $1.38.