Cubist Pharmaceuticals Inc. plans to go forward with a new drug application filing by year’s end for its investigational antibiotic Cidecin for complicated skin and soft tissue infections.

The Lexington, Mass., company made the decision after being notified by the FDA this week that the Cidecin NDA package would be accepted for filing as proposed.

Thomas Dietz, analyst at Pacific Growth Equities Inc. in San Francisco, liked the news, and raised his rating on Cubist to “Strong Buy.”

“We believe the potential for approval is in [the second half of 2003] with a standard one-year review,” Dietz wrote in a research note.

Cubist’s stock (NASDAQ:CBST) rose $4.15 Thursday, or 26 percent, to close at $20.13.

The indication of complicated skin and soft tissue (cSST) infections includes those that are both susceptible and resistant to Gram-positive organisms. Cubist reported positive results from a Phase III trial in March 2001 for that indication, as well as in October in a trial named Study 9801. The study demonstrated that Cidecin, or daptomycin for injection, was equivalent to the comparator agents vancomycin and semi-synthetic penicillins per the protocol reviewed and approved by the FDA. (See BioWorld Today, March 15, 2001, and Oct. 5, 2001.)

Cubist also has a Phase III trial of Cidecin ongoing in vancomycin-resistant Enterococcal infections and is set to begin another Phase III trial looking at its effect on endocarditis (infections of the heart valves) and bacteremia (infections of the bloodstream).

Jennifer LaVin, senior director of corporate communications, said Cubist would file supplemental NDAs in those indications if the initial NDA is approved.

Cidecin is the first in a new class of antibiotics called lipopeptides. Cidecin is daptomycin, a novel cyclic lipopeptide antibiotic derived from a fermentation product of Streptomyces roseosporous.

Cubist also recently completed a Phase II feasibility study of Cidecin in complicated urinary tract infections. A Phase III trial is not planned, LaVin said.

In January, Cubist reported disappointing results from CAP1, the first of two Phase II trials of the drug in community-acquired pneumonia. Cidecin failed to meet its primary endpoint demonstrating non-inferiority to the comparator agent Rocephin (ceftriaxone sodium). When the results were reported, Cubist Chairman and CEO Scott Rocklage pointed out that the endpoint was not achieved in the overall international study, which was conducted in North America, Europe, Eastern Europe and South Africa. In the North American and Western European populations, however, the endpoint was achieved in the intent-to-treat and clinically evaluable cohorts. Rocklage said he could not explain the difference. Due to the results, enrollment in a CAP2 study was halted pending further review. (See BioWorld Today, Jan. 18, 2002.)

On Thursday, Cubist said based on a reanalysis of results of the CAP1 study, it determined that a review by independent medical consultants was needed.

“We thought we could get additional value from the data having external experts examine the patient data from the trial,” LaVin said.

The company’s internal analysis will be used to help determine its strategy going forward, she said specifically, whether it should pursue trials in nosocomial pneumonia or continue with community-acquired pneumonia.

If Cidecin is approved for cSST, the marketing plan still is being decided, LaVin said.

“We’ve not made a final decision as how we will be marketing this product,” LaVin said. “Regardless of what we choose, we will be building a Cubist sales force.”

LaVin said Cubist would continue to entertain partnership discussions, but the “economics would have to be favorable [to Cubist] given the late stage of Cidecin.” She said Cubist wants to retain control of the NDA filings and clinical development of Cidecin.

“To date, none of our partnership discussions have resulted in agreements, because we felt that they didn’t add value beyond what we could do ourselves,” she said.

Regardless of any other decisions, Cubist “wants to control the launch in North America,” she said.

Cubist has a strategic alliance with Gilead Sciences Inc., of Foster City, Calif., for marketing the product in Europe, covering all of the European Union and Switzerland. The agreement was entered into in January 2001. (See BioWorld Today, Jan. 9, 2001.)

Pacific Growth’s Dietz estimated Cidecin sales of $55 million in 2004 and up to $212 million in 2006 and wrote that he did not believe the failed CAP study would affect sales estimates.