Traws Pharma Challenges Paxlovid, Aims for Monthly Flu Prevention Pill

By Alexander Harris

NEWTOWN, PA – January 26, 2026 – Clinical-stage biopharmaceutical company Traws Pharma announced significant progress on two fronts today, advancing its pipeline of antiviral drugs aimed at major respiratory threats. The company has completed enrollment in a key Phase 2 study for its COVID-19 treatment, ratutrelvir, and unveiled ambitious plans for a once-monthly pill to prevent seasonal influenza.

The dual announcements position the company as a contender in the multi-billion dollar antiviral market, seeking to address critical gaps left by current therapies for both COVID-19 and influenza. The news signals a strategic push to develop more convenient and accessible treatments that could reshape public health approaches to these persistent viral diseases.

A New Contender in the COVID-19 Arena

Traws Pharma's primary COVID-19 candidate, ratutrelvir, is an oral Mpro/3CL protease inhibitor, the same class of drug as Pfizer's highly successful PAXLOVID®. However, ratutrelvir is being developed with a crucial distinction: it is designed to be administered without ritonavir, the boosting agent used in PAXLOVID®.

This ritonavir-free profile is the cornerstone of the drug's potential. While ritonavir effectively increases the concentration of PAXLOVID®'s active ingredient in the body, it does so by inhibiting a key liver enzyme, CYP3A4. This mechanism is responsible for numerous and often serious drug-drug interactions with common medications, including certain statins, blood thinners, and immunosuppressants. Consequently, a significant portion of the patient population, particularly older adults and those with multiple chronic conditions, are ineligible for PAXLOVID® or require complex medication management to take it safely. This has created a substantial unmet need for effective, oral antivirals with a cleaner safety profile.

"From a clinical perspective, the ongoing data analysis confirms previous reports that ratutrelvir may provide a meaningful benefit across a broader range of patients, including those who are unable to receive ritonavir-boosted therapy," commented Robert R. Redfield, MD, Chief Medical Officer of Traws Pharma, in the company's press release.

The Phase 2 study, which enrolled 90 patients, directly compares ratutrelvir to PAXLOVID® in one arm, while also studying its effects in a separate group of patients who are ineligible for PAXLOVID®. According to the company, early results from the study are encouraging. Traws reported a favorable tolerability profile with fewer adverse events, a faster time to sustained symptom resolution, and, notably, no instances of viral rebound to date. This "rebound" phenomenon, where patients' symptoms and viral load return after completing treatment, has been a documented issue for some PAXLOVID® users and has fueled the search for next-generation alternatives.

Furthermore, Traws is exploring ratutrelvir's potential to combat Long COVID. The company hypothesizes that the drug's ability to maintain high plasma levels over a longer, 10-day treatment course—without the limitations of ritonavir—could lead to more complete viral clearance, potentially reducing the risk of post-acute sequelae. "By enabling earlier and potentially more complete viral clearance... ratutrelvir may offer a differentiated approach to both acute COVID-19 treatment and prevention of longer-term complications," Dr. Redfield added.

Revolutionizing Influenza Prevention

In a significant strategic expansion, Traws Pharma also announced it is advancing tivoxavir marboxil (TXM) as a potential first-of-its-kind prophylactic for seasonal influenza. The goal is a single, once-monthly oral tablet that could provide 28 days of protection.

This would represent a paradigm shift in flu prevention. Currently, the primary defense is the annual flu vaccine, whose effectiveness varies season to season depending on the match with circulating strains. For post-exposure prevention, antivirals like oseltamivir (Tamiflu®) require daily dosing for up to 10 days. The more modern baloxavir marboxil (Xofluza®), which shares the same mechanism of action as TXM—a CAP-dependent endonuclease inhibitor—is administered as a single dose for prophylaxis but is intended for short-term post-exposure use, not season-long prevention.

A convenient, once-monthly pill could offer an additional layer of protection for vulnerable populations, healthcare workers, or anyone seeking to avoid seasonal illness. "A new compressed tablet formulation may provide 28 day coverage, enabling a once-a-month prophylactic treatment," stated C. David Pauza, PhD, Chief Science Officer of Traws Pharma.

The company's confidence is based on prior Phase 1 data showing that an earlier formulation provided protective blood levels for up to 22 days. The new tablet is expected to extend this coverage. The drug has also demonstrated potent activity against a wide range of influenza strains in preclinical studies, including the highly pathogenic H5N1 avian flu, positioning it as a potential tool for both seasonal control and pandemic preparedness.

The Path Forward: Human Challenge and Market Strategy

To validate its ambitious claims for tivoxavir marboxil, Traws Pharma has secured a time slot for a human influenza prophylaxis challenge study in June 2026. This type of trial, in which healthy, consenting volunteers are intentionally exposed to a virus in a controlled quarantine environment, can rapidly generate clear data on a drug's effectiveness.

The study will be conducted by hVIVO, a contract research organization renowned for its expertise in human challenge models. While ethically complex, such studies are considered a powerful tool for accelerating antiviral development and are conducted under strict regulatory and ethical oversight. "Positive results will enable progression into registration studies," Dr. Pauza noted, highlighting the trial's critical role in the drug's development path.

For a clinical-stage company like Traws Pharma, these advancements represent crucial value inflection points. The antiviral market, supercharged by the COVID-19 pandemic, remains a high-stakes arena. Successfully developing a superior alternative to PAXLOVID® and a novel flu prophylactic would target two multi-billion dollar opportunities.

The company's dual-pronged strategy of tackling both COVID-19 and influenza with differentiated candidates appears designed to maximize its impact and appeal to potential investors and larger pharmaceutical partners. The completion of the ratutrelvir trial enrollment and the scheduling of the hVIVO challenge study are key milestones that demonstrate tangible progress, moving these promising therapies from theoretical concepts closer to potential real-world applications.

"Collectively, the advancement of our antiviral portfolio provides a number of significant value inflection points and could provide needed treatment and prevention options for clinically important viral diseases," concluded Iain Dukes, MA, DPhil, Chief Executive Officer of Traws Pharma. If successful in late-stage trials, these programs could not only secure a major position for the company in the respiratory disease market but also equip the public with powerful new tools to manage enduring viral threats.