SAN FRANCISCO, CA—In patients treated for acute bacterial skin and skin structure infections (ABSSSI), a similar, early reduction of >20% in lesion size was noted between oritavancin and vancomycin at 48 and 72 hours, reported Kenneth T. LaPensee, PhD, MPH, from The Medicines Company, Parsippany, NJ, at IDWeek 2013.

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The Biomarkers Consortium of the Foundation for the National Institutes of Health recommend that success in ABSSSI in registration trials be defined as achieving >20% reduction in lesion size at 48 to 72 hours after randomization.

“In light of this recommendation, this analysis sought to compare the incidences in achieving this end point between patients who received oritavancin or vancomycin in the SOLO 1 trial at hours 48 and 72 post the initiation of study medication,” Dr. LaPensee noted.

This Phase 3 multicenter, double-blind trial randomized patients to receive oritavancin (n=475) or vancomycin (n=479) in adults with ABSSSI comprising of wound infection, cellulitis, or major cutaneous abscess. SOLO 1 is the first of two studies to evaluate the efficacy and safety of single-dose IV oritavancin (1200mg) vs. 7–10 days of IV vancomycin (1g or 15mg/kg twice daily) for the treatment of patients with ABSSSI infection.

The primary endpoint was a composite outcome at 48–72 hours after initiation of study drug infusion that comprised cessation of spread or reduction in size of baseline lesion, absence of fever, and no rescue antibiotic medication. The secondary efficacy outcomes included lesion size decreased by ≥20% at 48–72 hours as well as investigator-assessed and sustained clinical cure at post-therapy evaluation (eg, 7–14 days after the end of therapy visit [Day 7–10] and a safety follow-up at 60 days).

Clinical response was monitored and assessed at regular intervals following treatment initiation. Both treatment groups had similar baseline characteristics. Mean age was 46.2 years in the oritavancin arm and 44.3 years in the vancomycin arm; 63.4% and 62.8% of the patients, respectively, were male.

Overall, 86.9% of patients who received oritavancin and 82.9% of those who received vancomycin achieved ≥20% lesion size reduction, respectively. “The patients with cellulitis/erysipelas, major cutaneous abscess, or wound infection had similar rates between the two treatment groups,” Dr. LaPensee stated. “MRSA patients achieved 90.4% and 84.0% of ≥20% lesion size reduction for oritavancin patients and vancomycin patients, respectively.” He added that patients who were treated completely in the ambulatory setting had similar rates as those treated as inpatients.

At least a 60% reduction in lesion size at 48–72 hours was observed in 52.9% of patients in the oritavancin arm and 46.9% of patients in the vancomycin arm. “Oritavancin patients seems to have a numerically higher percentage of lesion size reduction than vancomycin patients at an early treatment period,” he noted.

Dr. LaPensee concluded that achievement of 20% reduction in lesion size was strongly correlated with clinical cure at the end of treatment assessment. In addition, “achievement of 20% reduction is correlated with shorter length of hospital stay when a patient is hospitalized. This indicates that achieving the FDA early end point may be associated with earlier hospital discharge and shorter length of stay, particularly in the US.”