West Coast Editor

Arpida Ltd.'s success with its second pivotal Phase III trial with its antibiotic for complicated skin and skin structure infection (cSSSIs) boosted the stock and puts the firm on better footing in the race to find a drug that works against methicillin-resistant Staphylococcus aureus (MRSA).

The Basel, Switzerland-based firm's shares, trading on the Swiss Stock Exchange, closed Monday at CHF41.05 (US$34.15), up CHF6.30, more than 18 percent.

In a study known as ASSIST-2, iclaprim - an intravenous new member of the diaminopyrimidine class - again met the primary endpoint of non-inferiority to New York-based Pfizer Inc.'s market leader Zyvox (linezolid).

Arpida disclosed results of the first trial, ASSIST-1, in December, and expects to file a new drug application with the FDA this year.

Not only did iclaprim perform well, but it also did so with just one serious adverse event noted Khalid Islam, president and CEO of Arpida, in a conference call with investors.

"This was a change in some serum chemistry values," he said. "The patient had to go to a specialized clinic," and the changes "were resolved within a couple of days. There was no requirement for intervention of any other type, as far as I remember."

Of 494 patients in ASSIST-2, most had extensive cellulitis, abscesses, ulcers, burns or wounds. The cure rates for the intent-to-treat population were 84.9 percent iclaprim and 87.2 percent for linezolid. S. aureus was the most common baseline pathogen (about 60 percent) and up to 50 percent of the isolates were the so-called "superbug" MRSA, an epidemic in hospitals - much more than were seen in ASSIST-1, Islam noted. Phase II trials used vancomycin as the comparator, but since the Pfizer drug has proven superior to vancomycin, it's "more relevant in today's setting," Islam said.

The microbiological eradication rates for methicillin-susceptible S. aureus (MSSA) were 83.5 percent for iclaprim and 84.7 for linezolid. For MRSA, the rates were 77 percent and 80 percent respectively - very similar to the results from ASSIST-1.

For the modified intent-to-treat population (patients with an infecting Gram-positive baseline pathogen), the clinical cure rates were 83.3 percent for iclaprim and 85.9 percent for linezolid.

The cSSSI space is busy. South San Francisco-based Theravance Inc. expects an FDA decision on telavancin, a once-daily injectable lipoglycopeptide, in cSSSI in the second half of this year.

Targanta Therapeutics, of Cambridge, Mass., anticipates filing a new drug application early next year for its once-daily glycopeptide antibiotic, oritavancin, in cSSSI. In May, Targanta filed for an initial public offering to raise $86.25 million.

Also in May, another Swiss firm, Basilea Pharmaceutica Ltd., said partner Johnson & Johnson Pharmaceutical Research and Development LLC, of New Brunswick, N.J., submitted a new drug application for ceftobiprole, a broad-spectrum cephalosporin antibiotic, for cSSIs. Janssen-Cilag International NV, a Johnson & Johnson company, asked overseas regulators to approve ceftobiprole for marketing against complicated skin and soft tissue infections (cSSTIs), including diabetic foot infections.

Arpida is testing iclaprim in other diseases. In June 2007, the firm got the go-ahead from the FDA to start Phase II trials with the drug for hospital-acquired pneumonia, ventilator-associated pneumonia or health care-associated pneumonia, an oral version has completed three Phase I trials.

Islam said he was particularly proud that Arpida developed iclaprim from the preclinical stage to Phase III. The firm plans to market the drug in the U.S., but is seeking a partner elsewhere.

"Our aims have not changed," he said, but determining when such a deal might be disclosed is "rather difficult" to comment about.