Narrow-Spectrum Antibiotic for C. Difficile Fails to Show Treatment Benefit Over Vancomycin

The results of a phase 3 trial assessing the efficacy and safety of surotomycin (CB-183,315), a novel bactericidal cyclic lipopeptide, versus oral vancomycin in the treatment of Clostridium difficile infection (C. difficile) have shown that surotomycin failed to show benefit over vancomycin.

The randomized, double-blind, active-controlled, international multicenter trial, enrolled 608 subjects with C. difficile infection—confirmed by a positive toxin result. Of those initially enrolled, 285 participants were randomized to receive, 250 mg oral surotomycin twice daily, alternating with placebo twice daily, while 292 patients received vancomycin, 125 mg 4 times daily, orally for 10 days.

“Surotomycin has a narrow spectrum of activity, demonstrating low resistance rates and rapid activity against C. difficile with similar dose- and time-dependent pharmacodynamics to vancomycin in resolving C. difficile infection in a hamster model,” Sahil Khanna MBBS, division of gastroenterology and hepatology, Mayo Clinic, said.

Surotomycin however, did not demonstrate superiority for key secondary endpoints including sustained clinical response and clinical response over time, failing to show benefit over vancomycin. The clinical response over time and sustained clinical response were monitored until the end of the trial through a follow-up period of 30—40 days with a maximum of 100 days.

At the end of the treatment, the clinical response for those taking surotomycin (83.4%) was non-inferior to vancomycin (82.1%) with a difference of 1.4%. Through follow-up days, clinical response was no superior to surotomycin, nor sustained a clinical response, 63.3% versus 59% difference. Both treatments were generally well tolerated.

Surotomycin demonstrated non-inferiority to vancomycin for C. difficile clinical response at the end of the trial. It did not demonstrate superiority to vancomycin for the clinical response over time or sustained clinical response rate.

To be included in the study, participants were required to sign a consent form, be 18 years or older and 90 or younger, have diarrhea at least 3 times throughout 1 day, or 200 mL or liquid stool if using a rectal device, test positive for C. difficile, and if female, must not be pregnant or nursing.

Based on the trial results, the development program of surotomycin has been discontinued.

This follows previously reported results of a parallel phase 3 trial in which surotomycin failed to meet non-inferiority criteria relative to vancomycin for primary and key secondary endpoints.

The primary outcomes in the parallel study included the proportion of subjects with a clinical outcome of cure 2 days after the last dose of study drug, while the secondary outcome measures were to demonstrate a clinical response over time based on the length of time it takes for subjects to fail treatment, recur, die or become lost to follow-up day until day 40 to 30 days after the last dose of study drug—and the proportion of subjects who sustain a clinical outcome of cure until day 50, 30 days after the last dose of study drug.

In this second phase 3 trial, surotomycin demonstrated non-inferiority to vancomycin for C. difficile clinical response at end of treatment, similarly to vancomycin for a sustained clinical cure.

A version of this article originally appeared on MD Magazine.com.