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Fidaxomicin (Fificid) emerged favorable to vancomycin for the treatment of both initial and recurrent Clostridioides difficile infections in a Medicare population, according to a new retrospective study.
Although fidaxomicin was about 14% more effective than vancomycin in treating the initial infection, a larger difference of 30% was found among people with recurrent C difficile infections.
Lead investigator Erik Dubberke, MD, professor of infectious diseases at the University of Washington in St. Louis, Missouri, and colleagues noted that this real-world evidence of the two agents used to treat C difficile was “strikingly similar” to clinical trial data.
“Oftentimes there is a decrease in efficacy seen in real-world settings. This is due to the need to enroll people able to adhere to the study protocol, so clinical trial populations often are healthier in general to real-world populations,” Dubberke told Medscape Medical News. “This is why it is important to evaluate efficacy in real-world settings.”
Finding no evidence of a decrease in efficacy outside of the phase 3 trials was unexpected, he added.
They said that their findings support the 2021 change in clinical guidelines from the Infectious Diseases Society of America recommending fidaxomicin over vancomycin.
The study was presented May 23 at Digestive Disease Week (DDW) 2022, which was held virtually and in San Diego, California.
Evaluating a High-Risk Population
Because few real-world data exist that compare these two agents for C difficile, “particularly in a high-risk, high-prevalence population like Medicare,” the researchers evaluated Medicare Parts A, B, and D claims from 2016 to 2018 and included patients who had received fidaxomicin or vancomycin for an initial episode of C difficile and for any recurrent episodes.
The researchers compared sustained response and recurrence of C difficile within 4 weeks and 8 weeks after initial treatment with fidaxomicin or vancomycin. Treatment was considered successful if clinical resolution occurred 1 day after finishing therapy and there was no evidence of C difficile recurrence.
Recurrence of C difficile was defined as any evidence of new treatment or hospitalization for the infection within 4 or 8 weeks of when a patient filled the prescription for fidaxomicin or vancomycin.
The treatment groups were similar in age and race. However, the fidaxomicin group was at higher risk for recurrence, owing to risk factors, such as history of C difficile infection and compromised immunity. To reduce bias in comparing the groups, Dubberke and colleagues used propensity score matching. This approach yielded 190 matched pairs in the initial C difficile episode sample and 67 matched pairs in the recurrent episode sample.
Among patients with their first C difficile infection, fidaxomicin had a 13.5% higher rate of 4-week sustained response compared to vancomycin (71.7% vs 58.2%; P = .0058). There was also a 13.2% higher rate for 8-week sustained response with fidaxomicin (63.2% vs 50.0%; P = .0114).
Sustained response at 4 weeks and 8 weeks among the patients who experienced a recurrent episode of C difficile favored fidaxomicin over vancomycin by 30.1% (P = .0002) and 27.6% (P = .0012), respectively.
The rates of C difficile recurrence in patients who experienced their first C difficile infection or who experienced a recurrent bout were lower with fidaxomicin than vancomycin, but the differences were not statistically significant.
A Costly Edge
When asked to comment, Colleen Kelly, MD, a gastroenterologist and associate professor of medicine at Brown University in Providence, Rhode Island, said that the study was “worthwhile” and added that “Eric Dubberke has done a lot of work in this area.”
The study “gives more evidence that fidaxomicin does have a bit of an edge in people who have already had a bout of C diff,” she said.
Kelly added that the cost needs to be considered. Fidaxomicin “is about 30 times more expensive than vancomycin,” she said.
In part because of the cost difference, the American College of Gastroenterology (ACG) 2021 guidelines, which Kelly helped create, recommend that fidaxomicin be held as a second-line agent. The ACG guidance reserved fidaxomicin for people with C difficile for whom initial treatment with vancomycin failed.
“The fidaxomicin question is going to get a lot easier once the cost of the drug comes down,” Kelly said.
The study was funded by Merck. Dubberke is a consultant for Merck. Kelly reports no relevant financial relationships.
Créditos: Comité científico Covid