LAS VEGAS, Nevada — Clinicians are prescribing clarithromycin at high rates for Helicobacter pylori infections, despite increasing resistance to this antibiotic, researchers say.
In an analysis of 1 million US prescriptions for H pylori infections, 80% contained clarithromycin, said Carol Rockett, PharmD, associate vice president of RedHill Biopharma in Raleigh, North Carolina.
Rockett presented the findings here at the American College of Gastroenterology (ACG) 2021 Annual Scientific Meeting.
“Multiple talks here this week have suggested that the use of clarithromycin in H pylori is obsolete,” she told Medscape Medical News. “Clarithromycin is particularly ineffective in people with a genetic variant that causes rapid metabolism.”
According to the 2017 ACG clinical guideline for treating H pylori, patients diagnosed with this infection should be asked about their previous antibiotic exposure prior to treatment.
Additionally, clinicians should prescribe clarithromycin triple therapy with a proton pump inhibitor (PPI) and amoxicillin or metronidazole as a first-line treatment only in “regions where H pylori clarithromycin resistance is known to be <15%” and in patients with no previous history of macrolide exposure.
The guideline puts bismuth quadruple therapy, consisting of a PPI, bismuth, tetracycline, and a nitroimidazole, at the top of its list of six alternative first-line therapies. However, three of the six alternatives include clarithromycin.
ERADICATE Hp and ERADICATE Hp2
To understand how US physicians are treating patients with H pylori, Rockett’s colleagues analyzed data from two phase 3 clinical trials of RedHill’s RHB-105 (Talicia): ERADICATE Hp and ERADICATE Hp2.
RHB-105 is an all-in‐one combination of omeprazole (40 mg), amoxicillin (1000 mg), and rifabutin (50 mg) that the US Food and Drug Administration approved for treatment of H pylori in 2019.
The researchers followed 38 subjects from ERADICATE Hp who remained positive for H pylori after the study’s completion. Thirty-three had received a placebo in that trial, while the other 5 had received RHB-105.
The researchers obtained data on 31 of these patients. The overall cure rate was 61.3%. Of the 31 patients, 27 received a regimen including clarithromycin. Their cure rate was 59.3%.
Turning to ERADICATE Hp2, the researchers obtained data on 94 patients whose H pylori infections persisted after the trial. Of those, 67 had received an active comparator (amoxicillin 250 mg and omeprazole 10 mg) and 27 had received RHB-105.
The overall cure rate was 56.2%. For the 48 subjects who received therapies including clarithromycin, the cure rate was 60.4%. For the 22 subjects who received a bismuth-based quadruple regimen, the cure rate was 45.4%.
In another analysis, the researchers crunched 12 months of numbers from IQVIA PharMetrics Plus medical and prescription claim database of over 1 million prescriptions for H pylori. They found that 80% of the prescriptions made by gastroenterologists were for regimens containing clarithromycin. That proportion increased to 84% for physician assistants and internists, 85% for nurse practitioners, 86% for family practitioners, and 89% for general practitioners.
Finally, the researchers also analyzed patients for CYP2C19 gene status. They tested 65 subjects who received RHB-105 in ERADICATE Hp and all 445 subjects in ERADICATE Hp2. They found that 58.5% in ERADICATE Hp and 48.6% in ERADICATE Hp2 were normal metabolizers.
In 20 normal metabolizers who received clarithromycin, the drug eradicated the infection in 16 (80%). Out of 11 rapid metabolizers, clarithromycin eradicated the bacterium in 2 (18.2%). The difference was statistically significant (P = .0017).
“With clarithromycin, you can see that the efficacy is reduced in those patients who are rapid metabolizers,” Rockett said. “We didn’t see that with rifabutin [one of the drugs in RHB-105].”
Jared Magee, DO, MPH, a gastroenterology fellow at the Walter Reed National Military Medical Center in Bethesda, Maryland, said in treating H pylori infections, he checks the patients’ medical records to see what antibiotics they have received in the past and generally begins treatment with the bismuth quadruple therapy.
“There is education needed to get the data out there that clarithromycin-based therapies may not be the right choice for patients,” he said. “There is a subset who will do well with it, but I think where we’re at now, with the frequency of macrolide prescriptions for other conditions, that clarithromycin is going to be a difficult therapy for a lot of people.”
Clinicians who are not gastroenterologists may not be aware of the guideline promulgated by the ACG, he pointed out.
Rockett is an employee of RedHill Biopharma. Magee has disclosed no relevant financial relationships. The study was funded by RedHill Biopharma.
American College of Gastroenterology (ACG) 2021 Annual Scientific Meeting: Abstract P3083. Presented October 26, 2021.
Laird Harrison writes about science, health, and culture. His work has appeared in national magazines, in newspapers, on public radio, and on websites. He is at work on a novel about alternate realities in physics. Harrison teaches writing at the Writers Grotto. Visit him at lairdharrison.com or follow him on Twitter @LairdH
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