In vivo, in vitro, and in silico data indicate vapendavir, the only clinical stage, direct-acting
antiviral for rhinovirus, works against Rhinovirus C (RV-C)

PRAGUE, May 12, 2026 /PRNewswire/ — Altesa BioSciences presented new research at the 2026 International Conference on Antiviral Research (ICAR) demonstrating that vapendavir, a rhinovirus capsid inhibitor, exhibits clinically meaningful activity against Rhinovirus C (RV-C) – challenging longstanding assumptions about the treatability of this viral species by a capsid inhibitor.

The presentation, delivered by Katherine Squires, PhD, in the session “Coronaviruses, Influenza, RSV, and Other Respiratory Viruses II,” outlined evidence spanning clinical, computational, and laboratory research. Using newly developed RV-C culture models, Altesa confirmed that both vapendavir and its active metabolite ALT-001 dose-dependently inhibited RV-C at clinically relevant concentrations. In silico modeling indicated a potential mechanism of direct entry inhibition at the virus-host receptor junction.

“We are encouraged by the consistency of the clinical and preclinical data indicating vapendavir, contrary to prevailing opinion, inhibits RV-C, and in silico modeling provides a potential mechanism of action,” said Katherine Squires, Ph.D., Altesa BioSciences’ Vice President of Research & Development.

“Vapendavir’s developmental journey in parallel with the identification of RV-C runs counter to the conventional path of drug development in that clinical signals preceded mechanistic understanding; in silico and in vitro data have been generated to explain what was evident in the prior clinical studies,” Dr. Squires said. “The robust convergence of evidence is compelling and provides significant momentum as we move into our CARDINAL Phase 2b, multinational, randomized, placebo-controlled study in COPD patients experiencing rhinovirus infections.”

Dr. Katharine Knobil, M.D. Chief Medical Officer of Altesa BioSciences and former Chief Medical Officer of GSK notes that rhinovirus is responsible for roughly half of all acute COPD exacerbations, yet current standard of care is unable to target this underlying cause. “Care has largely focused on managing symptoms after the inflammatory cascade has already begun,” Dr. Knobil observed. “Vapendavir was developed to target rhinovirus to interrupt this cycle earlier directly. This potentially transformational approach to the treatment status quo represents an opportunity to provide a preemptive treatment option for respiratory infections in vulnerable patients who want and need better options.”

Dr. Knobil is leading the Phase 2b CARDINAL study, which builds on Altesa’s recently completed rhinovirus Phase 2a Challenge Study in COPD patients. The Challenge study data demonstrated vapendavir improved upper and lower airway symptoms, reduced illness duration and better maintained small airway lung function compared to placebo.

About Vapendavir
Vapendavir, taken orally in pill form, is a broad-spectrum, antiviral, investigational drug—preventing the virus from both entering human cells as well as reproducing. It exhibits potent clinical activity across all three types of rhinoviruses, including RV-C, and other respiratory enteroviruses. While the immediate focus is on evaluating vapendavir as a treatment for patients with COPD, vapendavir has potential for broader application in other high-risk respiratory populations, including people with asthma and other chronic lung diseases.

About the CARDINAL Study
The CARDINAL clinical trial is a Phase 2b, multinational, randomized, placebo-controlled study in COPD patients experiencing rhinovirus infections that will enroll 900 people with COPD in the US and UK. The trial was designed to reflect real-world care models, proactively identifying and supporting those at greatest risk. Participants will be closely monitored over time and, upon development of rhinovirus infection, will be randomized to receive one of two doses of vapendavir or placebo. The trial’s primary objective is to assess improvement in respiratory symptoms using established patient-reported outcomes, with additional endpoints evaluating time to symptom resolution, quality of life, healthcare resource utilization, and lung function.

About Altesa BioSciences, Inc.
Altesa BioSciences is a clinical-stage pharmaceutical company led by global experts in respiratory medicine and infectious diseases. Altesa is dedicated to improving the lives of people with chronic lung diseases like COPD and asthma, by treating the principal cause of exacerbations and pathological inflammation–viral respiratory infections. www.altesa.com

Press Inquiries: Mia Heck

210.284.0388

MHeck@altesa.com

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SOURCE Altesa Biosciences Inc.