West Coast Editor

Cubist Pharmaceuticals Inc. said its Phase III trial with Cubicin (daptomycin) hit its primary endpoints against Staphylococcus aureus endocarditis and bacteremia, and the company has a supplementary new drug application in the works.

The news sent Cubist's stock (NASDAQ:CBST) up $2.39 Tuesday, closing at $13.32, a 21.9 percent hike.

Already approved for infections caused by Gram-positive microorganisms, Cubicin earlier this month passed $100 million in cumulative net product revenues since its launch in November 2003.

Pacific Growth Equities in San Francisco put potential peak sales at $570 million if Cubicin wins approval in the expanded indications, which could happen next year. The firm had modeled peak sales in the U.S. of about $335 million for 2009 in skin and skin-structure infections for which the compound is approved.

"The information that we've seen from Arlington Medical Research, if you're looking at 2004, is that there were about 1 million courses of Staph treatment by existing therapies" such as vancomycin and semi-synthetic penicillins, said David McGirr, chief financial officer of Lexington, Mass.-based Cubist.

"In the in-hospital setting, that probably translates to about 5 million days of therapy," or a total $700 million market, he added. "Then you've got to put on top of that the outpatient market," which is not entirely clear - although current sales of Cubicin for outpatients, including off label, are estimated at about 37 percent of the total.

"We're certainly going to seek priority review" in the new indications, as the company did in the Cubicin first filing, McGirr said. "Our goal is to get the sNDA filed before the end of this year."

In the latest trial, Cubicin met its primary endpoints of non-inferiority in the intent-to-treat (ITT) and per protocol (PP) populations. The study enrolled 235 patients in the ITT population and 139 patients in the PP population (that is, patients who completed the specified treatments and evaluations according to protocol).

In the ITT population, 23 percent of patients were diagnosed with S. aureus endocarditis (heart-valve infections) and 51 percent were diagnosed with complicated bacteremia (blood infections), with balanced representation between the two treatment arms.

Thirty-seven percent of Cubicin-treated patients in that population were infected with methicillin-resistant S. aureus (MRSA) and 38 percent of the patients in the comparator arm were infected with MRSA.

Resistant endocarditis, McGirr noted, is "one of the most challenging of the Staph diseases to treat," with a 27 percent to 45 percent mortality rate.

Overall, Cubicin success in the ITT and PP populations was higher than in the comparator arm, with the greatest contrast observed in the subset of patients with MRSA, although the differences did not reach statistical significance.

Among greater than or equal to 15 percent of patients - in both the Cubicin (at 6 mg/kg/day dose) and comparator arms - the most common adverse events included musculoskeletal symptoms, nausea and vomiting, and edema. Those in the same sector of comparator-treated patients included diarrhea, potassium imbalance, anemia and renal failure or impairment.

Cubist said an abstract covering a more complete review of the study data will be submitted as a late-breaker offering to a scientific event in the fall, either the Interscience Conference on Antimicrobial Agents and Chemotherapy or the Infectious Diseases Society of America meeting.

Meanwhile, "clearly we've got a ways to go, but we are internally looking at what our next indication will be" with Cubicin, McGirr said. Osteomyelitis is a good possibility.

"That's a very difficult disease to treat because the infection is in the bone, and the bone is hard to penetrate," he acknowledged and Cubist will be seeking to determine if a feasible trial could be designed.

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