08 Jul The Reflux Condition That PPIs Can’t Fix — and the Research That May Change That
MedicalResearch.com Interview with:
Dr. Johnston, Ph.D.
Nikki Johnston, Ph.D.
Professor of Otolaryngology and Communication Sciences & Microbiology and Immunology
Medical College of Wisconsin
Co-founder and Chief Scientific Officer, N-Zyme Biomedical Inc.
MedicalResearch.com: Please provide a summary of your findings in your Modulation of Pepsin-Mediated Inflammatory Responses in Vocal Cord Epithelial Cells by Amprenavir and how that is impacting your future research studies.
Dr. Johnston: In this study, we wanted to know whether pepsin — the key nonacid component of reflux — could trigger inflammatory signaling in vocal cord epithelial cells, and whether a pepsin inhibitor could reverse that response. We found that exposing human vocal cord cells to pepsin at neutral pH, mimicking the nonacidic conditions typical of laryngopharyngeal reflux (LPR), significantly increased the transcription factor HIF-2α along with the downstream inflammatory genes IL8, IL1B, and ICAM1. Co-treatment with amprenavir, a pepsin inhibitor and the active metabolite of fosamprenavir, reduced HIF-2α levels and significantly suppressed IL8, ICAM1, and TNF expression.
Interestingly, when we blocked HIF-2α’s transcriptional activity directly, only IL1B expression was reduced; IL8 and ICAM1 were unaffected or even further increased. This tells us that HIF-2α is one contributor to pepsin-driven inflammation in the vocal cords, but not the whole story — pepsin is very likely activating several parallel stress pathways (NF-κB and MAPK signaling, among others) at the same time. For our future work, this reinforces that a single downstream pathway inhibitor is unlikely to fully quiet pepsin-induced inflammation, whereas a pepsin inhibitor acting further upstream, like amprenavir, has the potential to blunt several of these pathways at once. We are now examining whether similar mechanisms extend to pepsin’s emerging role in pulmonary fibrotic disease and gastro-esophageal reflux disease (GERD).
MedicalResearch.com: What are the key findings of your research on pepsin’s role in laryngopharyngeal reflux, and how does this differ from the current standard of care?
Dr. Johnston: Across our group’s work, and corroborated by other groups, the consistent finding is that pepsin, not acid, is the primary driver of injury and inflammation in LPR. Pepsin is inactive but stable at neutral pH and is only irreversibly inactivated at pH8 or higher. We discovered that pepsin is taken up by epithelial cells via receptor-mediated endocytosis and remains capable of being reactivated inside intracellular compartments of lower pH, causing cellular stress and inflammatory signaling even in nonacid reflux. This distinguishes LPR from typical GERD, where acid exposure is the dominant injurious agent and drug target.
Historically, treatment for LPR was proton pump inhibitor (PPI) acid suppression therapy, largely extrapolated from GERD management. However, placebo-controlled trials have not demonstrated a therapeutic benefit of PPIs for LPR, and both the American College of Gastroenterology and the American Gastroenterology Association now advise against PPI use for LPR in the absence of classic GERD symptoms (heartburn). Roughly 40% of GERD patients and, by some estimates, up to 86% of LPR patients have persistent symptoms despite acid suppression. Impedance-pH monitoring studies have shown that the majority of proximal reflux episodes associated with LPR symptoms are weakly acidic or nonacidic, meaning PPIs, which only reduce acidity, are simply not addressing the pepsin driving the disease. Our research supports a shift toward therapies that target pepsin directly, rather than gastric acid alone.
MedicalResearch.com: Was the clinical response to your LPR study — which drew more than 400 volunteers before the trial formally launched — consistent with your expectations, or were you surprised by the level of unmet need?
Dr. Johnston: The interest and response highlight the significant unmet clinical need. Our phase 2 trial only requires 104 participants, and we had over 500 people reach out to volunteer before we had even formally opened enrollment — and we continue to hear from people suffering from LPR on a daily basis. We are humbled by the level of interest. Many patients we hear from have struggled with LPR symptoms for years without relief from standard therapy, including physicians who have personal experience with LPR and volunteered to participate. People have offered to travel both nationally and internationally to participate in this trial.
One of the most humbling parts of this journey has been the support from people living with LPR themselves. These people have not only shared their stories and volunteered to participate in the trial but also offered to help in any way they can. Some have even offered professional services for free simply because they believe in the mission and want to help move the field forward. That level of trust is both humbling and motivating. It underscored something we already believed from the clinical literature and from patients’ laryngologists see in clinic — that a substantial number of people with LPR are not helped by PPIs and are actively looking for an alternative. It reinforced our sense of urgency in completing this trial carefully and rigorously, so that we can give the field a clear, well-powered answer about whether pepsin-targeted therapy is effective.
MedicalResearch.com: What should practicing clinicians take away from this research, particularly those managing patients who have not responded to PPI therapy?
Dr. Johnston: The most important takeaway is that a lack of response to PPI therapy should not automatically be interpreted as a lack of reflux disease, nor should it prompt reflexive dose escalation. In LPR specifically, PPI non-response is common and expected, because much of the disease-relevant refluxate is weakly acidic or nonacidic, and pepsin, not acid, appears to be the principal driver of tissue injury and inflammation and thus symptoms and disease.
For these patients, clinicians may want to consider mucosal protectant and alginate-based strategies, together with dietary and lifestyle modification, which recent studies show can meaningfully reduce pepsin burden and symptoms. Where available, referrals for impedance-pH monitoring or other objective reflux testing can help clarify whether nonacid reflux is contributing to symptoms. And as pepsin-targeted pharmacologic options move through clinical trials, I would encourage clinicians to keep an eye on this evolving area, since PPI-refractory LPR will likely be better served by a fundamentally different therapeutic approach than by acid suppression.
MedicalResearch.com: What does the Phase 2 trial aim to establish, and what further research will be needed following its completion?
Dr. Johnston: Our phase 2 trial, sponsored by N-Zyme Biomedical Inc., is a 12-week, randomized, double-blind, placebo-controlled study of oral fosamprenavir, the prodrug of amprenavir, in adults with LPR (FDA/IND 179956; MCW IRB PRO 56069; ClinicalTrials.gov Protocol Record: PRO00037954). Its primary aim is to establish whether directly inhibiting pepsin translates into meaningful symptomatic and objective improvement in LPR, which would represent the first clinical evidence for a pepsin-targeted pharmacologic therapy in this disease, rather than one aimed at acid suppression.
After the trial confirms efficacy, several important next steps will follow. We will need a larger, multicenter phase 3 trial to confirm the findings and refine dosing. We are also developing a sustained-release oral formulation and a fosamprenavir dry-powder inhaler designed for local laryngeal delivery, which is expected to improve efficacy while lowering systemic exposure. We also have a parallel trial in PPI-refractory GERD planned.
Beyond the drug itself, my team has submitted an application to the Centers for Disease Control for a dedicated ICD-10-CM diagnostic code for LPR/EER and are validating a fit-for-purpose clinical outcomes tool, both of which are necessary to support regulatory marketing approval and broader clinical adoption of pepsin-targeted therapies going forward. We are very excited to start the phase 2 trial. Preclinical and epidemiological data, as well as reports of “life changing” benefit after off-label use, are all very encouraging that this drug will help millions of people suffering with reflux and aspiration.
Citation:
P. Ergun, T. L. Samuels, and N. Johnston, “Modulation of Pepsin-Mediated Inflammatory Responses in Vocal Cord Epithelial Cells by Amprenavir,” The Laryngoscope (2026): 1–7, https://doi.org/10.1002/lary.70490.
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Last Updated on July 8, 2026 by Marie Benz MD FAAD