Methicillin-resistant Staphylococcus aureus is quite often a causative pathogen in acute bacterial skin and skin structure infections (ABSSSIs), and the infections may be mono- or polymicrobial, with Gram-negative pathogens present.1 In OASIS-1, patients with ABSSSI were treated with intravenous (IV) omadacycline (OMC) or linezolid (LZD), with a possible transition to oral formulation after at least 3 days of IV therapy. OASIS-2 investigated oral-only OMC.
A total of 691 patients receiving OMC and 689 patients receiving LZD were included. Patients in integrated OMC and LZD groups had similar baseline characteristics. The mean age of patients was 45 years, 64% were male, and 83% were enrolled at US sites. Early clinical response in the modified intention-to-treat (mITT) group was the primary end point in both studies and was defined as a ≥20% reduction in lesion size at 48 to 72 hours after treatment initiation. The secondary end point was investigator assessment of clinical response at post-therapy evaluation in the mITT and clinically evaluable populations, 7 to 14 days after treatment initiation.2
Results showed the following2:
- Infection types – Wound infections (46.8%), cellulitis/erysipelas (30.5%), major abscess (22.7%); median lesion size was 316 cm2 and 304 cm2 in the OMC and LZD patients, respectively
- S aureus was detected in 74.6% of patients, of whom 43.4% had methicillin-resistant S aureus
- 71% were monomicrobial Gram-positive infections and 15% were polymicrobial Gram-positive infections
- OMC showed similar efficacy to LZD for the primary and secondary end points, as well as for monomicrobial and polymicrobial infections
- Clinical responses as described above were similar across different infection types, lesion sizes, and baseline pathogens
- At day 3, the mean (standard deviation) reduction from baseline in lesion area was 53.4% (25.8) for OMC-treated patients and 53.0% (24.2) for LZD-treated patients. At the end of treatment, the mean reduction was 93.9% (14.4) and 93.7% (13.5) for OMC- and LZD-treated patients, respectively
- Treatment-emergent adverse events (TEAEs) were reported by 51% and 41% of patients receiving OMC or LZD, respectively. Most were mild or moderate
- The most frequently reported TEAEs were nausea (21.9% OMC and 8.7% LZD) and vomiting (11.4% OMC and 3.9% LZD). The events occurred on both ABSSSI studies; however, higher rates for OMC occurred in the loading dose period on day 1 and day 2 in the oral-only OASIS-2 study. Two OMC patients discontinued treatment for nausea or vomiting
- Serious AEs were reported by 2.3% and 1.9% of patients, respectively.
The integrated analysis of OASIS-1 and OASIS-2 showed IV and oral OMC to be a safe and effective treatment option for ABSSSI that was generally well-tolerated in patients.
- Moran GJ, et al. J Emerg Med. 2013;44:e397-e412.
- Abrahamian FM, et al. IDWeek 2018. Abstract 1347.