A new approach to fighting C. difficile appears to reduce significantly the likelihood the superbug will recur -- good news for patients prone to repeated bouts of the dreaded infection.
The treatment involves using antibiotics to fight Clostridium difficile, along with two new drugs, called monoclonal antibodies, which help to neutralize toxins produced by the bacteria.
The results of a small Phase 2 study suggest the medications cut the likelihood of a return of C. difficile by 72 per cent.
Clostridium difficile is a common bacterium that often lives in the gastrointestinal tract. For most people, it causes no problems, but when patients are treated with antibiotics for other infections, C. difficile can then grow unchecked. the bacteria produces two toxins, called toxin A and toxin B, which can then cause severe diarrhea and damage the lining of the large intestine.
C. difficile infects thousands of hospitalized patients and residents of long-term care facilities each year, and has even been known to infect otherwise healthy people. Many patients, particularly seniors, fail to develop antibodies after infection, and because the bacteria can survive on surfaces for long periods, infections can recur repeatedly in the same facility.
An epidemic strain of the bug, dubbed NAP-1, has led to severe outbreaks in a number of Canadian hospitals and killed an estimated 2,000 patients in Quebec in the last 10 years. That strain seems particularly efficient at producing toxins A and B, causing more severe illness. It also has a higher rate of relapse.
For the study, published in this week's New England Journal of Medicine, researchers compared 200 patients with C. difficile in 30 centres across the United States and Canada, from July 2006 through April of 2008.
Half received the standard antibiotics used to fight C. difficile (either metronidazole or vancomycin), plus a single injection of monoclonal antibodies developed by Medarex and MassBiologics, a company created at the University of Massachusetts Medical School. The other half was treated with antibiotics and a shot containing a placebo. Patients were then monitored for about three months.
While the Phase 2 study was conducted to determine safety of the drugs and the best dosing, the researchers noticed a significant difference in how the two groups fared.
Only 7 per cent of those patients who received the antibodies suffered a recurrence within 84 days, compared to 25 per cent among those who received the placebo. That works out to a 72 per cent reduction in recurrence.
Of the 44 patients infected with the epidemic strain of C. difficile, only 8 per cent who received the antibodies suffered a recurrence, compared with 32 per cent among those receiving the placebo. But the number of patients studied was too small for the difference to be considered statistically significant.
"We are pleased that this new treatment had such a significant impact for these patients," said Dr. Donna Ambrosino, the senior author of the study who is also executive director of MassBiologics.
Dr. Lorraine Kyne of University College Dublin, who wrote an NEJM editorial accompanying the paper's publication, called the results "impressive."
"This novel non-antibiotic approach to secondary prevention is likely to offer hope to physicians and patients battling C. difficile infection," she said.
The rights to commercialize the two new antibodies against C. difficile toxins have been licensed to Merck & Co. The company will now decide whether to do larger studies and seek government approval to market the medications.
