NEW ORLEANS (FRONTLINE MEDICAL NEWS) – An oral antibiotic in development in the United States, fusidic acid (oral formulation, sodium fusidate) was noninferior to linezolid based on early clinical response in a randomized, double-blind, multicenter trial of 716 people with acute bacterial skin and skin structure infections (ABSSSI), including cellulitis, wound infection, and major cutaneous abscesses.

Early clinical response was defined as a 20% or greater reduction from baseline in the surface area of redness, edema, or induration at 48-72 hours after starting treatment with the study drugs. In an intent-to-treat analysis, 87.2% of patients randomized to fusidic acid and 86.6% of the linezolid group met this primary endpoint of the phase 3 study .

At the end of therapy, approximately day 10, investigator-assessed response rates for fusidic acid and linezolid were 91.9% and 89.6%, respectively. In addition, 7-14 days later, at the time of posttherapy evaluation, investigator-assessed response rates were 88.6% and 88.5%, respectively.

“Fusidic acid showed similar efficacy and comparable safety” that persisted through treatment, said Andy Strayer, PharmD, vice president of clinical programs at Cempra Pharmaceuticals, which is developing sodium fusidate as an oral agent to treat ABSSSI patients in the United States. Leo Pharmaceuticals has marketed sodium fusidate outside the United States in various formulations for decades.

Fusidic acid has potent activity against gram-positive aerobic organisms, including methicillin-resistant Staphylococcus aureus (MRSA). “Strikingly, fusidic acid showed 100% success in patients with MRSA in the microbiologically evaluable population at the end of treatment and posttherapy evaluation time points,” Dr. Strayer said at the annual meeting of the American Society for Microbiology. “Fusidic acid may offer an important oral therapy alternative for MRSA infection.”

“Fusidic acid, a drug long used in other parts of the world, has been demonstrated in this first phase 3 trial, to be a potential new option for the treatment of MRSA skin and skin structure infections in the U.S.,” said Carrie Cardenas, MD , lead study author and a principal investigator at eStudySite, San Diego, and an internist in private practice in La Mesa, California.

There was a microbiological diagnosis established in 75% of patients. S. aureus was the most commonly detected pathogen (422 patients; 59%), and the study included 235 patients diagnosed with MRSA infection.

About two-thirds, 65%, of participants were men. Mean age was 45 years. Infections were classified as wounds in 61%, cellulitis in 26%, and abscess in 13%. Notably, 68% of the recruited participants had ABSSSI associated with intravenous drug use, a “sometimes overlooked consequence of the ongoing epidemic of IV drug use in the U.S.,” Dr. Strayer said.

In terms of safety, treatment-emergent adverse event rates were comparable between the two groups (37.9% with fusidic acid versus 36.1% with linezolid). Gastrointestinal events were the most common adverse events, 22.8% versus 18.2%, respectively.

“Considering complicated skin infections are one of the most rapidly growing reasons for hospitalizations and emergency department visits each year, we anticipate that fusidic acid, if approved, may help clinicians decrease the length of inpatient stay or avoid hospitalization altogether,” Dr. Strayer said.

Cempra sponsored the study. Dr. Strayer is a Cempra employee and shareholder. Dr. Carrie Cardenas is a principal investigator at eStudySite, San Diego, and performs research for Cempra, Paratek, Debiopharm, Motif, Durata, MicuRx, Bristol-Myers Squibb, and Bayer.


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