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PolyMedix's investigational antibiotic demonstrates efficacy in midstage trial

Monday, April 23 2012 | Comments
Evidence Grade 0 What's This?
PolyMedix Inc.'s PMX-30063, a potential first-in-class defensin-mimetic antibiotic, met the primary endpoint of a Phase II trial in which the drug was being evaluated as a treatment for patients with acute bacterial skin and skin structure infections (ABSSSIs).

The double-blind, proof-of-concept trial included 215 patients with ABSSSIs caused by Staphylococcus aureus. The participants were randomized to receive one of three dosing regimens of PMX-30063 (0.4 mg/kg of body weight on day one followed by 0.3 mg/kg for four days, 0.75 mg/kg on day one followed by 0.35 mg/kg for four days or 1 mg/kg on day one followed by 0.35 mg/kg for four days), with each regimen lasting a total of five days followed by two days of placebo, or Cubist Pharmaceuticals Inc.'s Cubicin (daptomycin), which was administered for seven days as per the label instructions.

PolyMedix noted that the study objectives were met, with all three doses demonstrating clinical efficacy and a favorable safety profile.

The study participants were first evaluated at day three for a clinical response. In the intent-to-treat population, which included all randomized participants, the response rate at day three was 79.6 percent with the low dose of PMX-30063, 68.5 percent with the mid dose and 75.9 percent with the high dose compared with 75.5 percent with Cubicin.

Similarly, in the per protocol population, which included 161 patients who received at least 80 percent of the study drug and had culture-confirmed S. aureus infections, the response rates were 85 percent, 71.4 percent and 89.7 percent with the low, mid and high doses of PMX-30063, respectively, compared with 74.5 percent with Cubicin.

All three dosing regimens of the investigational drug induced "early, high and sustained clinical responses," suggesting the possibility that shorter dosing regimens might be effective. The firm plans to initiate another trial later this year that will explore ways to optimize dosing of the compound, including shorter courses of therapy and administration of a single dose.

In addition, PMX-30063 was safe and generally well-tolerated. As observed in previous trials, the participants who received the drug commonly reported sensations of numbness and tingling that were generally characterized as mild. This side effect resolved following treatment and did not cause any of the participants to discontinue the study drug.

Other treatment-related adverse events occurred at similar rates in all study arms. In each PMX-30063 dosing group, there was one treatment-related serious adverse event that was considered at least possibly related to the study drug.

PMX-30063 is PolyMedix's lead infectious disease compound. The firm explained that the drug is designed to imitate the mechanism of natural human immunity, the host defense proteins. This unique mechanism of action is expected to reduce the risk of bacterial resistance observed with other antibiotics.

This information concerns a use that has not been approved by the Food and Drug Administration.

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