Traws Pharma Antiviral Bird Flu Program, Tivoxavir Marboxil, Shows Positive Data in Non-human Primates

Rhea-AI Summary

Traws Pharma (NASDAQ: TRAW) announced positive topline results for their antiviral bird flu treatment, tivoxavir marboxil (TXM), in non-human primates. The study demonstrated that a single dose of TXM significantly reduced lung viremia and prevented weight loss in H5N1 bird flu models.

Key findings include:

• TXM-treated animals showed lung virus levels below 2X103 infectious particles/ml, compared to control group levels of up to 1X107
• Control group lost 4.2% body weight over 10 days, while TXM-treated subjects maintained or gained weight
• Results consistent with previous positive outcomes in ferret and mice studies

The company plans to meet with FDA in H1 2025 to discuss potential accelerated approval through the 'Animal Rule' pathway, supported by safety data from Phase I studies in healthy volunteers completed in January 2025. An Investor Event is scheduled for March 31, 2025, to present TXM data and outline next steps.

Positive

• Significant reduction in lung viremia with single-dose treatment
• Prevention of weight loss in treated subjects
• Consistent positive results across three animal models (primates, ferrets, mice)
• Phase I safety studies in humans already completed
• Potential accelerated FDA approval pathway through Animal Rule

Negative

• Still in preclinical stage for bird flu indication
• FDA approval pathway not yet confirmed
• Efficacy in humans not yet demonstrated

Insights

Biotechnology Analyst

Traws Pharma's latest preclinical data for tivoxavir marboxil (TXM) represents significant progress in their H5N1 bird flu treatment development program. The non-human primate (NHP) study demonstrates two critical efficacy signals: substantial reduction in lung viral load and prevention of weight loss following viral challenge.

These results build strategically on their earlier positive findings in ferrets and mice, creating a comprehensive preclinical package across three mammalian species - a considerable strength for their upcoming FDA discussions. The consistent efficacy across multiple animal models substantiates TXM's mechanism as a CAP-dependent endonuclease inhibitor.

Particularly noteworthy is TXM's single-dose oral administration, which could offer significant advantages over existing influenza treatments that require multiple doses. The robust viral suppression achieved (100% of treated animals maintaining viral loads below quantitation threshold) suggests potent antiviral activity.

The company's pursuit of the FDA's Animal Rule pathway is strategically sound given the ethical impossibility of conducting efficacy trials for bird flu in humans. With Phase I safety data already in hand and briefing documents in preparation, Traws is methodically building their regulatory case. The H1 2025 FDA meeting will be pivotal in determining the development timeline and potential accelerated approval pathway.

Infectious Disease Specialist

The development of TXM arrives at a critical juncture in bird flu surveillance. The mounting evidence of H5N1 spread across wildlife, poultry operations, and dairy farms has created multiple human-animal interfaces where viral adaptation could occur. The identification of nine novel mutations in the virus isolated from a Texas dairy worker - mutations absent in cattle from the same farm - signals concerning viral evolution.

TXM's effectiveness against this precise viral strain in preclinical models is particularly relevant. The drug demonstrated ability to suppress viral replication below quantitation levels (2×10³ infectious particles/ml) compared to control animals reaching 1×10⁷ particles/ml - a 99.98% reduction that would dramatically alter transmission dynamics in an outbreak scenario.

The weight stabilization in treated animals versus 4.2% loss in controls indicates TXM may mitigate clinical symptoms while reducing viral shedding. This dual action would be invaluable for both individual treatment and epidemic control strategies.

While current human H5N1 cases remain sporadic, the public health community recognizes the pandemic potential. Former CDC Director Redfield's involvement adds credibility to the program's public health significance. A single-dose oral antiviral with demonstrated preclinical efficacy represents a potentially valuable addition to pandemic preparedness arsenals, especially as emerging mutations may challenge existing countermeasures.

• Tivoxavir marboxil (TXM), administered as a single dose in non-human primates, significantly reduced lung viremia and prevented weight loss, two key measures of antiviral activity in preclinical bird flu models
• Results build on earlier positive findings of mortality benefit for TXM in ferrets and mice
• FDA briefing documents in preparation for discussion of potential accelerated path to approval
• Data presentation to be provided at Investor Event on March 31, 2025 at 10:00 AM ET

NEWTOWN, Pa., March 24, 2025 (GLOBE NEWSWIRE) -- Traws Pharma, Inc. (NASDAQ: TRAW) (“Traws Pharma”, “Traws” or “the Company”), a clinical-stage biopharmaceutical company developing novel therapies to target critical threats to human health from respiratory viral diseases, today announced positive topline results from a study evaluating the use of tivoxavir marboxil (TXM) as a treatment for non-human primates challenged with a non-lethal dose of H5N1 bird flu. TXM is an investigational oral, small molecule CAP-dependent endonuclease inhibitor designed to be administered as a single-dose for the treatment of bird flu and seasonal influenza.

In the study, ten non-human primates (NHP, five treated, five control) received a non-lethal challenge dose of H5N1 bird flu at time zero and 12 hours later received a one-time treatment of TXM, dosed at the equivalent of a human dose of 480 mg. Key assessments included body weight and lung viremia. Since flu can cause weight loss, it is an important endpoint to assess the efficacy of interventions. Lung viremia is a standard endpoint in antiviral influenza studies.

• TXM-treated animals had significantly lower lung viremia – Lung viremia in control NHPs rose to be as high as 1X10⁷ infectious particles per ml whereas lung virus levels in NHPs treated with TXM were consistently below the level of quantitation (2X10³ infectious particles per ml)
• TXM-treated animals did not experience flu-induced weight loss – Control NHPs lost an average of 4.2% of their body weight over a 10-day period following viral challenge, whereas the body weight of NHPs treated with TXM remain stable or increased slightly (p<0.004)
• Consistent therapeutic effects of TXM across NHPs, ferrets and mice – As previously reported, TXM-treatment increased the proportion of surviving ferrets and lowered the viral burden in lung and nasal tissues following a lethal H5N1 bird flu challenge. In addition, TXM treatment resulted in complete survival and undetectable lung viremia in mice following a lethal H5N1 challenge, as detailed in a presentation at ICAR2025¹. Ferrets and mice are well-validated preclinical influenza models
  

“Bird flu continues to be a threat to human health. In addition to the ongoing plague of bird flu in wild birds and mammals, extensive spread in poultry and dairy farms has increased the exposure risk for agricultural workers. Every contact between humans and infected animals increases the risk that bird flu will evolve and spread in the human population,” said Robert R. Redfield, MD, Chief Medical Officer for Traws Pharma and former Director of the U.S. Centers for Disease Control and Prevention (CDC). “With positive results from three animal models, and acknowledging the substantial risk to human health, we are committed to seeking FDA feedback on the regulatory path for TXM in H5N1 bird flu.”

Reports of nine mutations found in the bird flu virus isolated from a Texas dairy worker and not in cattle from the same farm² validated concerns about the rapid pace of viral mutation and pandemic risk. We used that same virus in our preclinical studies and showed that TXM treatment suppressed bird flu disease and increased survival in several mammalian species, as noted above,” said C. David Pauza, PhD, Chief Science Officer for Traws Pharma. “Our studies focus on evaluating a one-time oral TXM dose. TXM’s safety is supported by data from Phase I studies in healthy volunteers reported in January 2025.”

“The Company intends to meet with the FDA in H1 2025 to align on a path forward, including the potential for accelerated approval utilizing the “Animal Rule”, wherein safety studies in healthy human volunteers plus effectiveness data in animal models are used to support drug approval. The Animal Rule is intended to provide a path to approval in cases where it would be unethical or impractical to conduct controlled human clinical trials,” said Werner Cautreels, PhD, Chief Executive Officer for Traws Pharma. “We will host an Investor Event on Monday, March 31, 2025 at 10:00 AM ET to present an overview of preclinical and human data on TXM and potential next steps towards approval.”

To register for the virtual Investor Event, click here.

About Tivoxavir Marboxil
Tivoxavir marboxil (TXM) is an investigational oral, small molecule CAP-dependent endonuclease inhibitor designed to be administered as a single-dose for the treatment of bird flu and seasonal influenza. It has demonstrated potent in vitro activity against a range of influenza strains in preclinical studies, including the highly pathogenic avian flu H5N1 (bird flu). Consistent, positive preclinical data from three species indicate that a single dose of TXM demonstrated a therapeutic effect against H5N1 bird flu. Seasonal influenza represents an estimated multi-billion dollar antiviral market opportunity, largely driven by global health organizations, practice guidelines and government tenders³, with upside potential from potential pandemic flu outbreaks including H5N1 bird flu. We believe that these data support further development of tivoxavir marboxil as a treatment for bird flu.

Additional highlights from mouse and ferret studies:

• In a mouse study using a lethal dose of bird flu, TXM treatment prevented death and body weight loss, and reduced lung viremia by > 10⁵ times.
• In a ferret study using a lethal dose of bird flu, all untreated animals died within 4 days of challenge, while TXM-treated animals had a slower course of disease. 100% of animals survived for 8 days, with an overall survival rate of 50% after 14 days.
• Data regarding lung viremia show that, consistent with the mouse and nonhuman primate studies, TXM-treated ferrets had between 10⁴ and 10⁶ -times lower levels of virus in lungs compared to untreated animals.
  

Source information:

1. ICAR2025 = the International Conference on Antiviral Research held in 2025
2. Mostafa, A., Barre, R.S., Allue-Guardia, A., et al. (2025) Emerging Microbes and Infections, https://doi.org/10.1080/22221751.2024.2447614;
3. TRAW data on file
   

About Traws Pharma, Inc.
Traws Pharma is a clinical stage biopharmaceutical company dedicated to developing novel therapies to target critical threats to human health in respiratory viral diseases. We are advancing novel investigational antiviral agents that have potent activity against difficult to treat or resistant virus strains that threaten human health. Our product candidates are intended to be safe, with simple dosing regimens. We strive to utilize accelerated clinical trial strategies with a commitment to patients who are especially vulnerable.

The Company’s two antiviral programs are investigational oral small molecules targeting bird flu and seasonal influenza, and COVID-19. Tivoxavir marboxil is in development as a single dose treatment for bird flu and seasonal influenza, targeting the influenza cap-dependent endonuclease (CEN). Ratutrelvir is in development as a COVID treatment, targeting the Main protease (Mpro or 3CL protease), without the need for co-administration of ritonavir.

For more information, please visit www.trawspharma.com and follow us on LinkedIn.

Forward-Looking Statements
Some of the statements in this release are forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, Section 21E of the Securities Exchange Act of 1934, as amended, and the Private Securities Litigation Reform Act of 1995, and involve risks and uncertainties including statements regarding the Company, its business and product candidates, including the potential opportunity, benefits and the regulatory plans for tivoxavir marboxil. The Company has attempted to identify forward-looking statements by terminology including “believes”, “estimates”, “anticipates”, “expects”, “plans”, “intends”, “may”, “could”, “might”, “will”, “should”, “preliminary”, “encouraging”, “approximately” or other words that convey uncertainty of future events or outcomes. Although Traws believes that the expectations reflected in such forward-looking statements are reasonable as of the date made, expectations may prove to have been materially different from the results expressed or implied by such forward looking statements. These statements are only predictions and involve known and unknown risks, uncertainties, and other factors, including the success and timing of Traws’ clinical trials, Traws’ interactions with and guidance from the FDA, collaborations, market conditions, regulatory requirements, the extent of the spread and threat of the bird flu, and those discussed under the heading “Risk Factors” in Traws’ filings with the U.S. Securities and Exchange Commission (SEC). Any forward-looking statements contained in this release speak only as of its date. Traws undertakes no obligation to update any forward-looking statements contained in this release to reflect events or circumstances occurring after its date or to reflect the occurrence of unanticipated events, except to the extent required by law.

Traws Pharma Contact:
Nora Brennan
Traws Pharma, Inc.
nbrennan@trawspharma.com
www.trawspharma.com

Investor Contact:
Bruce Mackle
LifeSci Advisors, LLC
646-889-1200
bmackle@lifesciadvisors.com

FAQ

What are the key results of TRAW's tivoxavir marboxil (TXM) bird flu treatment in primate studies?

TXM showed significant reduction in lung viremia (below 2X103 infectious particles/ml) and prevented weight loss in treated primates, while control groups showed high viremia (1X107 particles/ml) and 4.2% weight loss.

When will Traws Pharma (TRAW) meet with FDA for TXM approval discussion?

Traws Pharma plans to meet with FDA in H1 2025 to discuss potential accelerated approval through the 'Animal Rule' pathway.

What is the dosing protocol for TRAW's tivoxavir marboxil in bird flu treatment?

TXM is designed as a single-dose oral treatment, administered at 480mg human equivalent dose, given 12 hours after viral exposure in the study.

How did TRAW's TXM perform across different animal studies for H5N1 bird flu?

TXM showed consistent positive results across primates, ferrets, and mice, with increased survival rates and lower viral burden in lung and nasal tissues.

When will TRAW present detailed investor data for their bird flu treatment?

Traws Pharma will host an Investor Event on March 31, 2025, at 10:00 AM ET to present TXM data and development plans.