Cubist might stay clear of Ph3 for antibiotic, analyst says

While Cubist Pharmaceuticals ($CBST) is mulling over whether to advance its antibiotic against C. difficile infections into late-stage development, an analyst says the developer might not pursue the studies after Phase II data didn't show the drug could be clearly differentiated from the growing number of such treatments.

Cubist reported yesterday it would decide later this year whether to conduct further trials of the antibiotic, classified as CB-183,315, while the firm moves ahead with late-stage development of a separate antibiotic, CXA-201. With CB-183,315, the Lexington, MA-based firm's Phase II study showed the treatment's ability to treat diarrhea associated with C. diff bugs on par with vancomycin, the long-used antibiotic for such infections.

Yet the experimental antibiotic didn't show it was superior to vancomycin in treating a particularly dangerous strain of C. diff called NAP-1, something that might have separated Cubist's drug from the latest crop of similar treatments--including Optimer Pharmaceuticals' recently approved antibiotic Dificid, Needham analyst Alan Carr wrote in a note to investors yesterday.

"Cubist had previously indicated that efficacy against NAP-1 may be a key area of potential differentiation from Dificid," Carr said. "Hence, we believe there is a possibility that Cubist may not pursue further development of (CB-183,315)."

Of course, Cubist has found a way to share in Optimer's ($OPTR) recent win with Dificid, with its deal to co-promote the drug with the San Diego-based company to U.S. hospitals, where C. diff often camps out and can spread to patients. Yet the future of its internal candidate against the bug seems awfully uncertain right now.

- here's Cubist's release
- check out the AP's report

Related Aricles:
UPDATED: FDA gives Optimer key antibiotic approval
Cubist shares spike on fresh rumors of a $2B buyout

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