WASHINGTON The investigative antibiotic PTK 0796 appears to be comparable to linezolid in terms of efficacy against skin and skin structure infections and safety, based on the results of a phase II study of more than 200 patients.
Clinical success for the intention-to-treat population (those randomized, who received at least one dose) was 88% for the PTK 0796 group and 76% for the linezolid group, according to a poster presented at the jointly held annual Interscience Conference on Antimicrobial Agents and Chemotherapy and the annual meeting of the Infectious Diseases Society of America.
Clinical success was defined as the blinded evaluator's assessment that the infection was sufficiently resolved, such that no additional antibiotic therapy was required, at the test-of-cure visit. Patients who were not evaluated at a test-of-cure visit were considered clinical failures.
PTK 0796 is the first of a new class of antibioticsthe aminomethylcyclineswhich are semisynthetic compounds that are related to tetracycline. The drug is being developed by Paratek Pharmaceuticals, which carried out the study.
Patients with complicated skin and skin structure infections were randomized to receive either intravenous PTK 0796 or linezolid (Zyvox) and could be switched to oral therapy at the investigator's discretion. Intravenous dosing was 100 mg PTK 0796 every 24 hours or 600 mg linezolid every 12 hours. Oral dosing was 200 mg PTK 0796 every 24 hours or 600 mg linezolid every 12 hours. If the investigator considered that a patient might require gram-negative coverage, patients on linezolid could receive aztreonam (Azactam) infusions and those on PTK 0796 could receive placebo infusions.
In all, 118 patients were randomized to receive PTK 0796 and 116 patients, to linezolid. Patients in both groups were similar in terms of demographics, type of infection, severity of infection, and comorbidities. Major abscesses were the most common type of infection in both groups73 patients in the PTK 0796 group and 72 in the linezolid group.
Duration of treatment was similar for both groups. Intravenous duration was 4 days for the PTK 0976 group and 3 days for the linezolid group. Overall antibiotic duration was 10 days for both the PTK 0796 and linezolid groups.
In terms of microbiology, the primary pathogen was known for 84 patients in the PTK 0796 group and for 78 patients in the linezolid group. MRSA was the most common primary pathogen isolated in both the PTK 0796 and linezolid group52% and 49%, respectively. Clinical efficacy against MRSA was 96% in the PTK 0796 group and 79% in the linezolid group.
There were no drug-related serious adverse events in either group. No patient discontinued PTK 0796 because of adverse events, compared with two patients in the linezolid group. The most common adverse events in both groups were gastrointestinal21 in the PTK 0796 group and 18 in the linezolid group.