On the heels of a $15 million Series C financing, Adnexus Therapeutics Inc. filed for an initial public offering, hoping to raise as much as $86 million to fund ongoing work with its anti-angiogenic drug, Angiocept, and other early stage Adnectin-based products.

The Waltham, Mass.-based firm has not yet set the price or number of shares to be offered. Upon completion of the offering, its shares would trade under the symbol "ADNX."

The IPO filing is another big step for the relatively young biotech. Adnexus, which was founded as Compound Therapeutics Inc. in September 2002, spent its first few years quietly identifying lead Adnectins, protein drugs that are similar in shape to antibodies, using its PROfusion protein design engine before signing a splashy deal with New York-based Bristol-Myers Squibb Co. earlier this year to develop up to six oncology compounds.

In addition to $30 million in up-front and research funding, Adnexus could end up getting up to $211 million in development milestones for the first compound, and up to $141 million per program for each subsequent product. On top of that, the firm retains a co-promotion option for the first compound, could get substantial sales-based milestones and double-digit royalties. (See BioWorld Today, Feb. 27, 2007.)

In its prospectus, Adnexus said proceeds from the proposed IPO would be used to fund ongoing development of its lead internal program, Angiocept, a drug designed to block the vascular endothelial growth factor receptor (VEGFR)-2, the pathway for tumor angiogenesis. To date, Angiocept has completed most of its Phase I testing, and Adnexus plans to move into Phase II early next year, with the initial focus on glioblastoma multiforme.

Though marketed cancer drugs Avastin (bevacizumab, Genentech Inc.), Sutent (sunitinib, Pfizer Inc.) and Nexavar (sorafenib, Onyx Pharmaceuticals Inc. and Bayer Pharmaceuticals Corp.) already target the VEGF pathway, Adnexus said its candidate, as an Adnectin, might prove advantageous to antibodies. Adnectins, which consist of the natural amino acid sequence of certain human fibronectins, are shaped like the targeting domain of an antibody, but early research indicates that they might have greater affinity and better penetration. Adnectins also can be manufactured easily in a process involving E. coli.

The company also believes that Adnectins are distinctive enough to avoid the entanglements of antibody patent estates. Adnexus holds sole rights to intellectual property surrounding Adnectins.

Along with Angiocept work, IPO proceeds also would be used to support other research and development activities and for general corporate purposes. Adnexus, which reported a net loss of $9.8 million for the first half of 2007, had $22.7 million in cash as of June 30. The company added another $15.5 million in a Series C round completed earlier this month. (See BioWorld Today, Aug. 10, 2007.)

Lehman Brothers and UBS Securities LLC will serve as book-running managers for the offering, with Cowen and Co. and Lazard Freres & Co. LLC acting as co-managers.

Prior to the IPO, Adnexus' principal shareholders were: Flagship Ventures, of Cambridge, Mass., which holds 136.4 million shares, or 23 percent of the company; Atlas Venture, of Waltham, Mass., with 134.4 million shares, or 22 percent; Polaris Venture Partners, also of Waltham, with 134.4 million shares, or 22 percent; Venrock Associates, of Menlo Park, Calif., with 127.9 million shares, or 21.6 percent; and HBM BioVentures (Cayman) Ltd., with 37.5 million shares, or 6.3 percent.

In other financings news:

• Proteros biostructures GmbH, of Martinsried, Germany, said the BayBG Bayerische Beteiligungsgesellschaft mbH in Munich invested €1 million (US$1.4 million) in Proteros as a silent partner, and that equity capital permitted the acquisition of an additional €4.2 million in financing and research funds. Proteros, which specializes in structure-based lead optimization by X-ray protein structure analysis, intends to use the capital to increase service capacity and to expand the fragment screening and protein production areas.