Skin microbiome therapy to protect against Staphylococcus aureus in patients with atopic dermatitis (AD) proved safe in a phase 1 randomized clinical trial that also demonstrated “encouraging clinical and mechanistic results,” Richard L. Gallo, MD, PhD, and his coinvestigators have reported in Nature Medicine.
Findings from the 1-week, 54-patient trial of a topical formulation containing Staphylococcus hominis A9 (ShA9) offer evidence that the strain directly kills S. aureus, inhibits the production of S. aureus–generated toxins, and enables expansion of a healthy bacterial community, “allowing the rest of the microbiome to start to recover to normal,” Gallo, professor and chairman of the department of dermatology at the University of California, San Diego, said in an interview.
“And perhaps most exciting,” Gallo added, is the finding that the subset of patients with AD who were most responsive to the ShA9 compound – approximately two-thirds of the participants who were randomized to receive it – showed improvement in local EASI (Eczema Area and Severity Index) and SCORAD (Scoring Atopic Dermatitis) scores used to assess inflammation. Plans are underway for a larger and longer trial, he said.
S. aureus commonly colonizes patients with AD and exacerbates disease by causing inflammation. In recent years, Gallo and other investigators have come to believe that AD is a cyclic disease in which the skin’s microbiome affects the host, and the host affects the microbiome. The goal of bacteriotherapy is to break the cycle of S. aureus colonization and improve the skin immune and barrier dysfunction characteristics of AD, Gallo said.
ShA9, a bacterium isolated from healthy human skin, was chosen as a potential topical therapy for AD based on its capacity both to selectively kill S. aureus and to inhibit toxin production by S. aureus. Gallo’s team’s preclinical work involved screening thousands of isolates of coagulase-negative staphylococci for gene products that perform these two functions by expressing both antimicrobial peptides (AMPs) and autoinducing peptides (AIPs), the latter of which inhibit the S. aureus quorum-sending system that leads to toxin production. Most patients with AD lack protective strains of coagulase-negative staphylococci, including S. hominis, prior research has found.
The double-blind phase 1 trial randomized 54 adults with moderate-severe AD affecting the ventral forearms in a 2:1 fashion to receive the proprietary lyophilized preparation of ShA9 or an ShA9-free formulation twice daily for 1 week. All participants were culture positive for S. aureus.
Clinical assessments and skin swabs were obtained before and within an hour after the first application of day 1, and swabs were collected on days 4 and 7 within 4 hours of the first application.
Blinded physician assessments and skin swabs were also obtained at 24, 48, and 96 hours after the final dose on day 7.
Based on structured daily diaries, there were no serious adverse events, and significantly fewer adverse events in those treated with ShA9, compared with the vehicle alone; 55.6% versus 83.3%, respectively, were considered to have adverse events.
The adverse event–reporting system captured the normal fluctuation of eczema and considered any report of fluctuation above baseline to be an adverse event. “Patients treated with the [placebo formulation] had the expected high frequency of itching, burning, and pain that you see with AD but it was encouraging that the frequency of reporting these events was significantly less in those treated with the active [formulation],” Gallo said in the interview.
Their report describes a decrease in S. aureus in participants treated with ShA9, and increases in ShA9 DNA. Not all S. aureus strains were directly killed by ShA9, but all strains had reduced expression of mRNA for psm-alpha, an important virulence factor. That reduced expression correlated with ShA9 AIPs and improved EASI scores, the latter of which was observed in a post-hoc analysis. “Participants with S. aureus not killed by ShA9 were still sensitive to inhibition of toxin production, a mechanistic outcome that predicted clinical improvement in mice and may require longer therapy to observe clinical improvement in humans,” the investigators wrote.
Local eczema severity was not significantly different between the bacteriotherapy and control groups. But the post-hoc analysis showed that after 7 days of treatment, and up to 4 days after treatment was discontinued, the patients with S. aureus that was sensitive to killing by ShA9 (21 out of 35 total who received the bacteriotherapy) showed improvement in EASI and SCORAD scores, compared with control patients.
Future research will assess the compound in both S. aureus culture-positive and culture-negative patients, and in patients with mild disease, Gallo said.
The trial was conducted at USCD and the National Jewish Health General Clinical Research Center in Denver, and was sponsored by the National Institute of Allergy and Infectious Diseases. The ShA9 formulation and related technology are licensed to MatriSys Bioscience, of which Gallo is the cofounder and an advisory board member. Gallo holds equity interest in the company.
This article originally appeared on MDedge.com, part of the Medscape Professional Network.
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