Phathom Pharmaceuticals (PHAT) Phase 3 Trial of Vonoprazan in Helicobacter pylori (H. pylori) Infection Met All Primary and Secondary Endpoints

Phathom Pharmaceuticals, Inc. (Nasdaq: PHAT), a late clinical-stage biopharmaceutical company focused on developing and commercializing novel treatments for gastrointestinal diseases, announced today that in PHALCON-HP, its pivotal Phase 3 clinical trial for the eradication of H. pylori infection, both vonoprazan-based regimens successfully met their primary endpoints and met all secondary endpoints. The trial studied vonoprazan in combination with amoxicillin and clarithromycin (“vonoprazan triple therapy”) and vonoprazan in combination with amoxicillin (“vonoprazan dual therapy”) compared to lansoprazole in combination with amoxicillin and clarithromycin (“lansoprazole triple therapy”). PHALCON-HP is the largest Phase 3 registration trial ever conducted in H. pylori infection, randomizing 992 patients with confirmed H. pylori infection.

Phase 3 Topline Results

Primary endpoint analysis The primary endpoints in the PHALCON-HP study were non-inferiority of the H. pylori eradication rate for each of vonoprazan triple and dual therapy compared to lansoprazole triple therapy. Based on U.S. Food and Drug Administration (FDA) feedback, the primary endpoint excluded patients with amoxicillin or clarithromycin resistant strains of H. pylori.

Both vonoprazan-based regimens successfully met their primary endpoints. In the modified intent-to-treat (mITT) population, H. pylori eradication rates were 84.7% with vonoprazan triple therapy and 78.5% for vonoprazan dual therapy compared to 78.8% with lansoprazole triple therapy (p<0.0001 and p=0.0037, respectively, for non-inferiority).

Additional efficacy analyses were conducted using the pre-specified per protocol population, a subset of the mITT population comprised of patients who were protocol compliant as defined by FDA draft Guidance for Industry1. In the per protocol population, H. pylori eradication rates were 90.4% with vonoprazan triple therapy and 81.2% with vonoprazan dual therapy compared to 82.1% with lansoprazole triple therapy (p<0.0001 and p=0.0077, respectively, for non-inferiority).

Secondary endpoint analysis Vonoprazan triple therapy and vonoprazan dual therapy also met all secondary endpoints, demonstrating superior eradication rates versus lansoprazole triple therapy in all patients and patients with clarithromycin resistant strains of H. pylori. Patients with clarithromycin resistant strains comprised 20.3% of the PHALCON-HP study population.

Vonoprazan triple therapyThe H. pylori eradication rate of vonoprazan triple therapy was superior to that of lansoprazole triple therapy among all patients in both the mITT population (80.8% vs. 68.5%; p=0.0001) and the per protocol population (85.7% vs. 70.0%; p<0.0001).

The H. pylori eradication rate with vonoprazan triple therapy was superior to that of lansoprazole triple therapy in the subset of patients with H. pylori strains resistant to clarithromycin in both the mITT population (65.8% vs. 31.9%; p<0.0001) and the per protocol population (67.2% vs. 29.0%; p<0.0001).

Vonoprazan dual therapyThe H. pylori eradication rate of vonoprazan dual therapy was superior to that of lansoprazole triple therapy among all patients in both the mITT population (77.2% vs. 68.5%; p=0.0063) and the per protocol population (81.1% vs. 70.0%; p=0.0013).

The H. pylori eradication rate of vonoprazan dual therapy was superior to that of lansoprazole triple therapy in the subset of patients with H. pylori strains resistant to clarithromycin in both the mITT population (69.6% vs. 31.9%; p<0.0001) and the per protocol population (79.5% vs. 29.0%; p<0.0001).

“Acid suppression is a key factor in addressing shortcomings associated with currently available H. pylori treatments, especially in light of increased resistance to antibiotics, including clarithromycin,” said Professor William D. Chey, M.D., AGAF, FACG, FACP, Professor of Medicine and Director of the GI Physiology Laboratory at the University of Michigan. “I am very impressed with the results of PHALCON-HP which demonstrate that replacing a PPI with vonoprazan in H. pylori treatment regimens has the potential to meaningfully enhance eradication rates that have been declining over the last two decades. Further, the potential to limit the use of clarithromycin with a dual therapy regimen has the potential to transform clinical practice.”

Safety profileBoth vonoprazan-based regimens were generally well tolerated with a safety profile comparable to lansoprazole triple therapy. The most common adverse events (>2.0%) reported in the vonoprazan triple therapy, vonoprazan dual therapy, and lansoprazole triple therapy arms, respectively, were diarrhea (4.0%, 5.2%, and 9.6%), dysgeusia (4.3%, 0.6%, and 6.1%), nausea (1.7%, 1.7% and 2.6%), headache (2.6%, 1.4%, 1.4%) and vaginal infections (2.3%, 0.9%, 0.3%). Overall rates of discontinuation due to adverse events were 2.3% for vonoprazan triple therapy-treated patients, 0.9% for vonoprazan dual therapy-treated patients, and 1.4% for lansoprazole triple therapy-treated patients.

Full results from the PHALCON-HP study will be presented at a future medical meeting and submitted for publication in a peer-reviewed journal.

“We believe the topline results of our PHALCON-HP study support the potential of vonoprazan-based therapies to change H. pylori treatment,” said Terrie Curran, Phathom’s President and Chief Executive Officer. “There are estimated to be over 200 million people infected with H. pylori in the United States and Europe, and our market research among patients and physicians show antibiotic resistance, coupled with complexity of treatment, as leading causes of eradication failure. Based on these results, which further build on the robust data previously reported from clinical studies of vonoprazan-based regimens in Japan, we plan to submit NDAs with the FDA for vonoprazan dual and triple therapy in H. pylori before the end of the year. Phathom thanks all the patients, physicians, and clinical sites for their role in the PHALCON-HP trial and for helping in our efforts to advance the treatment landscape for the millions of patients suffering with H. pylori infection.”

Conference call on the PHALCON-HP trial resultsPhathom will host a webcasted conference call today, Thursday, April 29, 2021 at 4:30 pm ET to discuss the PHALCON-HP study results.

To view the live webcast, visit https://investors.phathompharma.com/news-events/events-and-presentations. Please join approximately 10 minutes prior to the scheduled start time.

A replay of the webcast and the slide presentation will be available after the meeting on the News & Events section of the Phathom website at https://investors.phathompharma.com/news-events/events-and-presentations.

You May Also Be Interested In

• Mainz Biomed (MYNZ) Reports Positive Topline Results from Pooled Study Evaluating Novel mRNA Biomarkers and Proprietary AI Algorithm
• Acrivon Therapeutics (ACRV) Reports Initial Positive Clinical Data for ACR-368 and Pipeline Program Progress Today at Corporate R&D Event
• Mangoceuticals (MGRX) Acquires Global Preventive Care Patent Portfolio