Assistant Managing Editor

Pfizer Inc.'s antibiotic dalbavancin, which had advanced all the way to FDA review before getting hung up in the agency's shifting guidelines regarding noninferiority studies, is ready to head back to the clinic with start-up Durata Therapeutics Inc.

Five venture investors - Domain Associates LLC, New Leaf Venture Partners, Aisling Capital, Sofinnova Ventures and Canaan Partners - worked with New York-based Pfizer to structure a stock-purchase deal under which they would acquire the assets of Vicuron Pharmaceuticals Inc., which Pfizer bought in 2005 for $1.9 billion. The big pharma firm is hanging on to Eraxis (anidulafungin), a marketed antifungal agent, but the rest of Vicuron's pipeline, consisting of dalbavancin and two preclinical antibiotic programs, was transferred to Durata. (See BioWorld Today, June 17, 2005.)

That kind of spinout, especially one involving a late-stage asset, can be tricky, said Ron Hunt, managing director at New York-based New Leaf Ventures. "But we had a unique set of circumstances here," he told BioWorld Today. "We had a group of investors and a pharma firm willing to work collaboratively to fund a win-win [agreement]."

The VCs had been looking for a promising candidate in the antibiotic space, which is "still quite an interesting field to invest in," Hunt said, pointing to clinical development plans that require shorter trials than drugs in other indications such as cancer and a handful of recent successful deals involving antibiotic firms.

Last month, Cubicin (daptomycin) maker Cubist Pharmaceuticals Inc., of Lexington, Mass., agreed to pay $92 million for San Diego-based Calixa Therapeutics Inc., in a deal that could bring up to an additional $310 million in milestones to Calixa shareholders. Cubist will gain rights to a Phase II-stage antibiotic for Gram-positive Pseudomonas aeruginosa infections. (See BioWorld Today, Dec. 15, 2009.)

In October, Boston-based Paratek Pharmaceuticals Inc.'s late-stage antibiotic for drug-resistant infections scored a potential $485 million deal with Novartis AG, of Basel, Switzerland. And, a month later, Trius Therapeutics Inc., of San Diego, joined the list of biotech firms hoping to go public, filing for an $86 million initial public offering to fund Phase III studies of torezolid in complicated skin and skin structure infections (cSSSIs). (See BioWorld Today, Oct. 9, 2009, and Nov. 10, 2009.)

But for Hunt and Durata's other investors, Pfizer's glycopeptide antibiotic dalbavancin stood out.

For starters, the drug is backed by a wealth of clinical data, having been tested in more than 1,000 patients.

Results have shown "very nice Gram-positive coverage, including MRSA," he said. And, importantly, its pharmacokinetic profile allows for once-a-week dosing vs. the twice-daily dosing regimens required by other antibiotics, and could limit hospital stays for patients and even offer the possibility of outpatient treatment.

"So it lends itself to a very interesting health economics story," Hunt said.

It also helps that two of the VCs - and now board members - had formerly been execs at King of Prussia, Pa.-based Vicuron. Dov A. Goldstein, of Aisling, had served as vice president and chief financial officer, while George Horner, of Sofinnova, was CEO.

Pfizer, which already markets Zyvox (linezolid) for cSSSIs, received an approvable letter for dalbavancin in 2007 as a once-weekly, two-dose treatment in cSSSIs, including those caused by MRSA (methicillin-resistant Staphylococcus aureus). At that time, Pfizer said the FDA, which had recently published draft guidance on noninferiority studies as the basis for approval of antibacterial products, had requested additional data.

Dalbavancin wasn't the only antibiotic to stumble at the regulatory level. Cambridge, Mass.-based Targanta Therapeutics Corp. (later acquired by The Medicines Co.) received a complete response letter for oritavancin, as did ceftobiprole from Basel, Switzerland-based Basilea Pharmaceutica AG. And the agency informed another Swiss firm, Arpida A/S (now merged with Evolva SA), that another trial would be needed for approval of its antibiotic, iclaprim, in cSSSI. (See BioWorld Today, Jan. 21, 2009.)

South San Francisco-based Theravance Inc. and partner AstraZeneca plc, of London, finally won approval for Vibativ (telavancin) in September, nearly three years after first submitting its new drug application. (See BioWorld Today, Sept. 15, 2009.)

Durata has not yet released details for its clinical plan for dalbavancin. Hunt said the firm anticipates initiating another trial in the second half of 2010.

The good news is that Durata should be funded through to dalbavancin approval. The amount of investment by the five venture firms was not disclosed, but Hunt called it a "significant amount of capital," most of which will go directly to dalbavancin work.

After approval, the company will have to decide how to proceed with commercialization, but taking the drug to market on its own "could be one of the scenarios," Hunt said.

Durata has started putting together a management team. Its board consists of Hunt, Goldstein and Horner, as well as Nicole Vitullo, of Domain Associates; James Healy, of Sofinnova; and Brent Ahrens, of Canaan.