With four Phase III trials of its anti-infectives under way, Optimer Pharmaceuticals Inc. is raising $35.9 million through a private placement of 4.6 million shares at $7.80 per share.

The offering price represents a slight discount to Optimer's closing price of $8.37 on Tuesday. The San Diego-based company's shares (NASDAQ:OPTR) rose 20 cents to close at $8.57 on Wednesday.

John Prunty, Optimer's chief financial officer and vice president of finance, said the money should last until mid-2009, considering the company had $38.1 million in cash, equivalents and short-term investments at the end of the second quarter and burns about $8 million per quarter. Optimer's existing cash should be sufficient to complete its four ongoing Phase III trials, but the new money will help the company "maintain a prudent cash balance" and support pre-launch activities, Prunty said.

Two of the ongoing Phase III trials compare Optimer's antibiotic OPT-80 to Exton, Pa.-based ViroPharma Inc.'s Vancocin in the treatment of Clostridium difficile-associated diarrhea (CDAD). The primary endpoint is noninferiority in clinical cure rate, and the secondary endpoint is recurrence within four weeks. Prunty expects data from both trials in the first half of next year, with a new drug application filing targeted for late 2008. (See BioWorld Today, May 2, 2007.)

Vancocin is an oral capsule formulation of the generic antibiotic vancomycin, the only drug approved for CDAD, although the generic antibiotic metronidazole often is used off-label due to its lower cost.

Prunty said OPT-80 offers advantages in its potency, bacteria-killing rather than inhibiting mechanism, narrow-spectrum activity that leaves beneficial bacterial unharmed, and lack of adverse effects.

Other CDAD treatments in development include Oscient Pharmaceuticals Inc.'s Ramoplanin and Genzyme Corp.'s tolevamer, which failed a Phase III trial earlier this year. (See BioWorld Today, July 9, 2007.)

Beyond CDAD, Optimer expects to begin a trial of OPT-80 in the prevention of CDAD next year as well as begin preclinical work on a topical formulation for methicillin-resistant Staphylococcus (MRS) strains. A trial of the drug in the prevention of vancomycin-resistant enterococcal (VRE) bloodstream infections is slated for 2009.

Optimer's other two Phase III trials compare the antibiotic Prulifloxacin to placebo in travelers' diarrhea, with a primary endpoint of the time to last unformed stool. Data are expected in the first half of next year, with a new drug application filing targeted for 2008. Prulifloxacin is marketed by other companies outside the U.S., and Optimer plans to follow its approval with a Phase IV study comparing the drug to ciprofloxacin, the generic antibiotic often used to treat travelers' diarrhea.

Optimer also has two drug candidates outside the field of anti-infectives: OPT-822/821 for breast cancer and OPT-88 for osteoarthritis. Prunty said the plan is to partner both at the "opportunistic" time. Other partnering activity may come within the next nine months, as Optimer looks for an ex-North American partner for OPT-80, he added.

The offering is expected to close Oct. 29. Piper Jaffray & Co. acted as the exclusive placement agent.

In other financing news:

• ARYx Therapeutics, of Fremont, Calif., set the terms for its proposed initial public offering. The company plans to offer 5 million shares priced between $14 and $16 per share, as well as an additional 750,000 shares to cover any overallotments. Proceeds will support clinical trials of ARYx's enhanced reformulations of existing drugs. Morgan Stanley & Co. Inc. is acting as sole bookrunner and lead manager for the offering, with CIBC World Markets Corp., Jefferies & Co. Inc. and Leerink Swann & Co. Inc. acting as co-managers. ARYx intends to trade on Nasdaq under the symbol "ARYX." (See BioWorld Today, Sept. 4, 2007.)

• HistoRx Inc., of New Haven, Conn., raised $6 million in a Series B financing. The round was led by existing investor Brook Venture Partners and included participation by existing investor Navigator Technology Ventures and new investors Roche Venture Fund, Commons Capital and Maven Capital. Proceeds will be used for development and commercialization of tissue-based diagnostic products.

• Phase Bioscience Inc., of Durham, N.C., raised an additional $5.4 million in Series B financing, bringing the company's total round to $6.6 million. New investor Fletcher Spaght Ventures (FSV) co-led the round, joining Series B lead investor, Johnson & Johnson Development Corp., which closed on a first tranche of the financing in December and invested further in this closing. Founding investor Hatteras Venture Partners (HVP) also invested in the round. Phase, which licensed some of its technology from Duke University, aims to reduce the costs and timeline associated with the purification of therapeutic proteins. Guy Fish, of FSV, and Doug Reed, of HVP, joined the company's board.

• XDx Inc., of Brisbane, Calif., filed to raise up to $86.3 million in a proposed initial public offering of its common stock. The number of shares to be offered and price range have not yet been determined, but XDx intends to use proceeds for development and commercialization of its gene expression-based tests for monitoring transplant rejection and autoimmune diseases. J.P. Morgan Securities Inc. and Morgan Stanley & Co. Inc. are acting as joint book-running managers, with Piper Jaffray & Co. and JMP Securities LLC acting as co-managers. XDx intends to list on the Nasdaq under the symbol "XDXI."