Phathom Pharmaceuticals completes enrolment in Phase 2 EoE trial
Phathom Pharmaceuticals has completed patient enrolment ahead of schedule in its Phase 2 pHalcon-EoE-201 study, evaluating vonoprazan (VOQUEZNA) as an investigational treatment for eosinophilic oesophagitis (EoE) in adults. The study enrolled 95 patients across 41 US sites, and the company anticipates topline results from the double-blind 12-week treatment phase in the fourth quarter of 2026.
EoE is a chronic inflammatory condition of the oesophagus driven by eosinophil accumulation, causing symptoms ranging from dysphagia and food impaction to chest pain and regurgitation. Despite its clinical burden, the condition has relatively few approved therapies. Proton pump inhibitors (PPIs) are widely used as first-line acid suppression treatment, but none carry an FDA-approved label for EoE, leaving a meaningful gap in the treatment armamentarium.
Trial design and strategic rationale
The pHalcon-EoE-201 study is a randomised, double-blind, placebo-controlled two-part design. In Part 1, participants were evenly split between vonoprazan 20 mg once daily and placebo for 12 weeks. Completers are eligible to roll into Part 2, a 12-week open-label extension in which all participants receive active treatment. Phathom describes the study as the first large, placebo-controlled trial of an acid suppression therapy in EoE, a framing that, if supported by the data, would give the readout added scientific weight.
Evan Dellon, professor of medicine at the University of North Carolina School of Medicine and principal investigator for the study, noted that completing enrolment "brings us closer to better understanding whether vonoprazan could offer a meaningful new option for patients" with a disease that remains difficult to manage.
If Phase 2 results are positive, Phathom says it intends to open discussions with the FDA on a Phase 3 pathway, including the potential for a paediatric evaluation that could support an extension of regulatory exclusivity for VOQUEZNA.
Market context and competitive positioning
Vonoprazan belongs to the potassium-competitive acid blocker (PCAB) class, which mechanistically differs from PPIs by blocking the potassium-binding site of the gastric proton pump in a reversible, concentration-dependent manner. This translates to a faster onset of acid suppression and activity that is less dependent on meal timing, characteristics that may be relevant in EoE if acid control is a meaningful driver of mucosal healing.
The broader EoE therapy landscape has gained momentum in recent years. Dupilumab, the IL-4/IL-13 inhibitor co-developed by Sanofi and Regeneron, received FDA approval for EoE in 2022, representing the first biologic licensed in the indication. Cendakimab, an oral small-molecule CCR3 antagonist from AbbVie following its acquisition of Receptos-linked assets, has also been in late-stage development for EoE. Phathom's approach is differentiated by positioning vonoprazan as a non-steroidal oral option focused on acid suppression rather than direct immunomodulation, which could suit patients earlier in the treatment pathway or those who are unsuitable for biologics.
For Phathom, EoE represents a potential label expansion for a product already commercially available in the US for erosive GERD and H. pylori eradication. Success in Phase 2 would not guarantee approval but would provide the company with a credible regulatory discussion point and the prospect of broadening its addressable market into a chronic, underserved condition.
Investors will focus on whether the Q4 2026 readout demonstrates histological response, the conventional endpoint in EoE trials, alongside symptom data and the safety profile in this patient population.