Xoma Ltd announced preliminary results of a Phase II trial with XMP.629 gel, a novel topical peptide formulation, for the treatment of mild-to-moderate acne. The results were inconclusive in terms of clinical benefit of XMP.629 compared to vehicle gel. There was no discernable dose response and the vehicle response was higher than anticipated. The drug appeared safe and well-tolerated, a company release said.

The double-blind, randomized, controlled clinical study enrolled 253 patients and was designed to evaluate safety, tolerability and efficacy. Patients were dosed with either vehicle gel or one of three dosages of an XMP.629 gel (0.01%, 0.05% and 0.1%), administered nightly for 12 weeks. The primary endpoint of this study was to compare the percentage change from baseline at Week 12 in inflammatory lesion counts, non-inflammatory lesion counts and total lesion counts between patients applying XMP.629 gel and those receiving vehicle gel. The study also evaluated the percentage of patients who were clear or almost clear after 12 weeks of treatment.

"We plan to analyze the data more closely and will continue to review the results with leading dermatology experts," said John L Castello, chairman, president and chief executive officer. "At this point in time, however, XOMA does not plan to initiate additional clinical trials with XMP.629," he added.

XMP.629 is a synthetic peptide compound derived from bactericidal/permeability-increasing protein (BPI) - a human host-defense protein that is part of the body's early lines of defense against invading micro-organisms. The compound kills acne-causing bacteria.

In preclinical studies, XOMA scientists evaluated antibacterial activity of XMP.629 against P. acnes and other skin flora. They found that the compound, in a proprietary formulation buffer, showed bactericidal activity against P. acnes, including strains resistant to other antibiotics such as erythromycin or clindamyacin.

Acne is a multi-factorial disease that affects the sebaceous (oil-producing) hair follicles (pores) of the skin, primarily in the face and neck, but often on the back and chest as well, where hairs grow most densely. The current understanding of the disease is that increasing levels of androgen sex hormones at puberty lead to increased production of oils and epidermal cells lining the follicles.