Fighting against resistance
The efficacy of PPI-based clarithromycin-based triple therapy has fallen below 80% in the United States and Europe over the past few decades, largely because of antibiotic resistance, said William Chey, MD, during a presentation of the results at the annual meeting of the American College of Gastroenterology. Dr. Chey is a professor of medicine and director of the GI physiology laboratory at Michigan Medicine.
Vonoprazan is more stable in acid than are PPIs, and produces greater and more durable acid reduction, according to Dr. Chey. That’s important for two reasons: One is that some antibiotics are acid-labile, and so may have their efficacy directly impacted in a more acidic environment. The other factor is that most antibiotics work better on bacteria that are actively replicating, and H. pylori reproduces better in a more neutral environment. “So, you increase the replication, you increase the bioavailability of the antibiotics. And therefore, hopefully, that underlies why we see it working better in the patients with [antibiotic] resistance,” Dr. Chey said in an interview.
It remains to be seen whether or not the drug will receive FDA approval, but he pointed to other regimens like bismuth quadruple therapy and rifabutin-based triple therapy that are already available. “If I had the choice, I would never use a PPI-based triple therapy again. People should not be doing that,” said Dr. Chey.
“More successful H. pylori eradication regimens are certainly needed, and these results are particularly relevant and interesting given the increasing failure of initial treatment regimens,” said Kimberly Harer, MD, who moderated the session. She noted that the secondary analysis of patients with clarithromycin-resistant infections was particularly relevant. “The superiority analysis indicating vonoprazan triple therapy resulted in increased H. pylori eradication compared to lanzoprazole triple therapy was especially interesting,” said Dr. Harer, who is a clinical lecturer at University of Michigan Health, Ann Arbor.
One downside to the study is that it didn’t compare vonoprazan combinations to quadruple therapy of a PPI, bismuth, tetracycline, and a nitroimidazole, said Joseph Jennings, MD, who was asked to comment on the study. Other treatment approaches include sequential antibiotics and other combinations. Dr. Jennings also highlighted the findings that the vonoprazan regimens were superior against clarithromycin-resistant strains. “The more different regimens we can add to the armamentarium, the better chance we have because the resistant patterns fluctuate all throughout the world,” said Dr. Jennings, who is an assistant professor of medicine at Georgetown University and director of the center for GI bleeding at MedStar Georgetown University Hospital, both in Washington.
He also pointed out that physicians can face a conundrum when patients fail multiple lines of therapy and have testing done that shows high levels of resistance. Some have allergies that prevent them from turning to other antibiotics. “That’s a market where lots of doctors struggle. Something like this would be a nice add-on,” said Dr. Jennings.
The study was funded by Phathom Pharmaceuticals.** Dr. Chey has consulted and/or received research support from Abbvie, Alfasigma, Allakos, Alnylam, Bayer, Bioamerica, Cosmo, Intrinsic Medicine, Ironwood, Modify Health, My GI Health, My Nutrition Health, Nestle, Phathom Pharmaceuticals, QOL Medical, Redhill, Salix/Valeant, Takeda, Urovant, and Vibrant. Dr. Harer and Dr. Jennings have no relevant financial disclosures.
*Correction, 10/29/21: An earlier version of this article misstated the percentage of patients in the modified intention-to-treat population who achieved eradication with vonoprazan triple therapy.
**Correction, 10/29/21: An earlier version of this article misstated the name of Phathom Pharmaceuticals.