Thrombolytic drug developer Imarx Therapeutics Inc. priced its initial public offering lower than expected, selling 3 million shares at $5 apiece for gross proceeds of $15 million, while Archemix Corp., a firm specializing in aptamer-based therapeutics, filed for a public listing, with hopes of raising $69 million.

For Tucson, Ariz.-based Imarx, which late last week cut the price target for its IPO from between $6.50 and $7.50 to $5, the offering falls dramatically short of the $75 million the company had anticipated in its May 2006 filing. At that time, Imarx was working on two late-stage urokinase drug candidates acquired from Abbott, of Abbott Park, Ill., but a lack of adequate funding prompted the return of those programs to Abbott, and Imarx, instead, focused the majority of its resources on its earlier-stage internal programs for ischemic stroke. The company withdrew the first IPO filing in May, only to refile a month later. (See BioWorld Today, May 23, 2006.)

In its prospectus, Imarx said the company expects to receive net proceeds of $12.3 million - or $14.4 million if underwriters Maxim Group LLC and I-Bankers Securities Inc. exercise the full 450,000-share overallotment option. About $8 million of that is earmarked to support ongoing development of the SonoLysis programs, which combine the company's MRX-801 microbubble technology and ultrasound, with or without tPA (tissue plasminogen activator), to clear blood clots and treat the resulting ischemia. Smaller than red blood cells, MRX-801 microbubbles are designed to penetrate a blood clot so that when ultrasound is applied, the clot is broken into small particles.

The company started a Phase I/II study in January, expected to enroll about 72 patients, to test SonoLysis therapy with tPA in ischemic stroke patients. That study should complete enrollment in the first half of 2008, and a Phase II trial likely will begin thereafter. A program testing SonoLysis without the addition of tPA also is expected to begin Phase II testing about the same time.

If SonoLysis alone succeeds in demonstrating positive results, the product could expand the treatment window for stroke patients - with tPA, patients must receive treatment within three hours of stroke onset - and eliminate the cardiovascular risks associated with tPA treatment.

Imarx is testing SonoLysis tPA therapy in preclinical studies in additional indications, including myocardial infarction, peripheral arterial occlusive disease and deep-vein thrombosis. A research program is investigating the targeted delivery of MRX-803 microbubbles to treat angiogenic tumors.

Other funds from the IPO will be spent on commercialization activities surrounding Abbokinase, an approved urokinase product for acute massive pulmonary embolism. That product was acquired from Abbott, and Imarx has sold it since October. As of June 30, aggregate net proceeds from Abbokinase sales totaled about $13.8 million.

Imarx expects the proceeds from the IPO, along with Abbokinase revenue and existing cash - about $2.7 million, as of June 30 - to sustain the company until September 2008.

The company's shares had not yet begun trading Wednesday. Its stock will be listed on Nasdaq under the ticker "IMRX." Following the offering, Imarx will have about 10 million shares outstanding.

Archemix Aiming For Listing

Hoping to gain access to public markets, while raising $69 million to boost its pipeline, Cambridge, Mass.-based Archemix filed for an IPO, though it has not yet determined share price or the number of shares to be offered. Upon successful completion of the offering, the firm would trade on Nasdaq under "ARCH."

Archemix, which develops drugs based on aptamers, synthetically derived oligonucleotides, using its SELEX (Systematic Evolution of Ligands by EXponential expression) technology, said in its prospectus that funds from the IPO would go toward ongoing clinical development of ARC1779, which is set to begin a Phase IIa study next quarter in acute coronary syndrome and a Phase Ib trial in thrombotic thrombocytopenic purpura (TTP). ARC1779 is designed to inhibit the function of von Willebrand factor, which, when activated, causes the aggregation of platelets on the blood vessel wall.

Other funds will be used to expand preclinical studies and move into the clinic with additional aptamer product candidates, including those anticipated to be co-developed with partner Geneva-based Merck Serono SA in a cancer collaboration signed last month. The company has a similarly structured deal with Dublin, Ireland-based Elan plc for anti-IL-23 aptamers against multiple sclerosis, psoriasis, rheumatoid arthritis and inflammatory bowel disease. (See BioWorld Today, June 12, 2007.)

Other partnered products are in or near the clinic, including AS1411 (nucleolin) with London-based Antisoma plc, which expects to begin Phase II studies later this year in acute myeloid leukemia and renal-cell carcinoma, and REG1 (Factor IXa) with Durham, N.C.-based Regado Biosciences Inc., which is set to start Phase II in the fourth quarter in coronary artery bypass graft (CABG) surgery patients.

Archemix also has an ongoing deal with Nuvelo Inc., of San Carlos, Calif., to develop NU172, a short-acting, second-generation direct thrombin inhibitor that is expected to start Phase I testing late this year or early next year in CABG patients.

In connection with that collaboration, Nuvelo will purchase shares from Archemix in a private placement concurrent with the IPO, with the number of shares equal to either the lesser of $10 million or 15 percent of the aggregate gross proceeds from the offering.

Archemix, which reported a net loss of $4.5 million for the first quarter of 2007, had, as of March 31, a cash position of $39.4 million.

Banc of America Securities LLC, Bear, Stearns & Co. Inc. and Cowen and Co. are serving as underwriters for the proposed offering.

In other financings news:

• Cyntellect Inc., of San Diego, completed a private financing of $15.1 million, and investors can choose to commit an additional $8.3 million investment. Funds will be used to hire personnel, expand operations, accelerate development and commercialization of products and explore new applications of the company's laser-based live-cell manipulation technology. The round was led by Third Security LLC's investment fund under New River Management V LP, and one of Cyntellect's existing major shareholders participated as well. Third Security now gains the right to elect a majority of the company's board.

• Dyax Corp., of Cambridge, Mass., said underwriters exercised in full their overallotment option to purchase an additional 1.6 million shares of common stock at the public offering price of $3.67 each, bringing the aggregate net proceeds of the offering to about $41.3 million. Proceeds will be used to fund ongoing trials of DX-88 (ecallantide) in hereditary angioedema and for the prevention of blood loss during on-pump cardiothoracic surgery. UBS Investment Bank acted as sole book-running manager, with Deutsche Bank Securities Inc., J.P. Morgan Securities Inc. and Lazard Capital Markets LLC serving as co-managers. (See BioWorld Today, July 16, 2007.)