The number of newly approved antibiotics has declined significantly since the 1980s as large pharmaceutical companies have mostly withdrawn from research and development in this critical market segment. Fortunately, the biotech industry is now stepping up to the plate to develop much-needed antibiotics to fight a rising number of drug-resistant superbugs, such as Clostridium difficile (or C. difficile).
This virulent superbug bacteria strikes 700,000 Americans each year, ravaging the gut lining, causing diarrhea, fever, loss of appetite, nausea, belly pain and sometimes death. Over a year ago, C. difficile infection (CDI) surpassed MRSA as a hospital-acquired infectious disease.
Optimer Pharmaceuticals, Inc. of San Diego, CA recently received FDA approval for Dificid (fidaxomicin), a narrow spectrum antibiotic tablet to treat C. difficile-associated diarrhea. In clinical studies reported in the New England Journal of Medicine, patients treated with Dificid had a high cure rate of 90%, similar to standard vancomycin treatment, but with a significantly lower rate of recurrence: 13.3% versus the vancomycin group who showed a recurrence rate of 24.0%.
Dificid is the first in a new class of antibiotics called macrocycles, engineered to target C. difficile specifically. Sherwood Gorbach, MD, Chief Medical Officer for Optimer and co-author of the studies says, “because fidaxomicin is a narrow spectrum antibiotic, there is less likelihood to produce resistance, a problem we see with vancomycin.” Optimer holds patents for developing the unique fidaxomicin compound from a fungus found in soil.
The elderly and people in hospitals who have been treated with antibiotics are most at risk because C. difficile gets a chance to flourish and produce toxins in the gut after antibiotics have wiped out normal gastrointestinal flora. At any given time, about half of the patients in a hospital are receiving antibiotics.
The spread of infection can be difficult to contain as the spores can live outside the human body for a long time and may be found on hard surfaces such as bed linen or medical equipment. While C. difficile is mainly a hospital-acquired infection, about one-third of cases are found in long-term care facilities such as rehabilitation centers and nursing homes.
Recurrence is a significant problem as the symptoms are often worse than the original bout of infection. Gorbach emphasizes, “the reduction in the rate of recurrence is a significant advancement for patients with CDI. Fidaxomicin showed a sustained clinical response for 25 days, the period following treatment when most recurrences happen, in a greater number of cases vs. vancomycin.”
Another current therapeutic option for treating CDI is the off-label use of metronidazole, recommended by the CDC as an alternative to vancomycin. It has been around since the 1950s and has never been submitted to the FDA for approval for C. difficile treatment. Although not tested in clinical studies, according to Gorbach, Dificid offers a more promising treatment option, “Metronidazole is well absorbed, and so a lot of patients taking it experience side effects, whereas the side effects with fidaxomicin are very rare, because it is not readily absorbed.”
Recently in Canada, there have been more outbreaks of a hypervirulent C. difficile strain, variously referred to in the media as NAP1/BI/027. Over the past summer, that strain was responsible for an outbreak that led to more than 30 deaths in the Niagara, Ontario area. NAP1/BI/027 was the culprit identified between 2002-2004 in Quebec hospitals, where hundreds of patients were infected and several deaths occurred. The CDC also reported outbreaks of NAP1/BI/027 in several states in 2004.
While Dificid is not yet approved for sale in Canada, Optimer is currently in consultation with Health Canada to determine if Dificid can offer some assistance to combat NAP1/BI/027. In the clinical studies, about 35% of the patients had the NAP1/BI/027 strain of C. difficile. Analysis of the data from two of the clinical trials showed that further investigation is required: one study showed Dificid was superior to vancomycin for reducing recurrences of the hypervirulent strain, but the other study showed equal results.
Update: Dificid tablets were approved by Health Canada on July 5, 2012, the first new treatment for C. difficile infection in Canada in over 20 years. “Awareness of the burden of CDI on the Canadian health care system is high with many health care providers, patients, and caregivers impacted by this devastating infection,” said Paulash Mohsen, President and Country Manager for Optimer Canada. “This familiarity with CDI will help us as we make DIFICID available to Canadian patients in need.”
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Find out more about Dificid or watch a video to learn more about this new antibiotic and how it offers an effective treatment for patients. The CDC provides comprehensive information about the current strain of C. difficile, recommended measures to help prevent C. difficile Infection, and the judicious use of antibiotics – Get Smart: Know When Antibiotics Work. Check out our earlier posts “FDA Clears First Rapid Diagnostic Test for Superbug MRSA,” and “FDA Approves INCIVEK to Treat Hepatitis C.”