GRI Bio's IPF Drug Shows Potential to Repair Lung, Not Just Slow Damage

LA JOLLA, CA – December 10, 2025 – Biotechnology company GRI Bio, Inc. today announced promising topline results from a Phase 2a clinical trial for its experimental drug, GRI-0621, offering a new ray of hope for patients with Idiopathic Pulmonary Fibrosis (IPF), a relentless and fatal lung disease. The study data suggests the oral therapeutic is not only safe and well-tolerated but may also possess the ability to reverse lung scarring and improve lung function, a potential paradigm shift from current treatments that only slow the disease's progression.

Beyond Slowing Decline: A Glimpse of Fibrosis Reversal

Idiopathic Pulmonary Fibrosis is characterized by the progressive and irreversible scarring of lung tissue, which robs patients of their ability to breathe. With a median survival of just three to five years post-diagnosis, the need for more effective therapies is critical. The current standard of care, including drugs like pirfenidone (Esbriet®) and nintedanib (Ofev®), can slow the decline in lung function but cannot halt or reverse the underlying damage. These treatments are also associated with significant side effects that can impact a patient's quality of life.

GRI Bio's GRI-0621 takes a novel approach by targeting Natural Killer T (NKT) cells, which are key regulators early in the inflammatory cascade that drives fibrosis. The goal is to interrupt the disease process and restore the immune system to a state of balance. The latest trial data provides the first clinical evidence that this approach may be working.

Secondary endpoints of the study revealed significant improvements in serum biomarkers of collagen turnover, which act as molecular signposts for fibrotic activity. In placebo-treated subjects, the rate of type VI collagen remodeling was fibrogenic, indicating continued scarring. In contrast, subjects treated with GRI-0621 showed a shift to a fibrolytic state, suggesting a resolution of fibrosis. Furthermore, biomarkers of type IV collagen, a critical component of the lung's alveolar basement membrane, indicated that GRI-0621 may induce a lung tissue repair mechanism, something current therapies do not achieve.

“Secondary endpoints related to the effect of GRI-0621 on biomarkers associated with disease progression provided evidence that GRI-0621 maintains a net anti-fibrotic effect compared to standard of care,” said Dr. Toby Maher, Professor of Clinical Medicine at the Keck School of Medicine, USC Los Angeles, in a statement. “We look forward to watching the clinical advancement of GRI-0621 as a potential treatment for patients with IPF.”

A Safer Profile and Improved Lung Function

For many IPF patients, the daily burden of treatment can be as challenging as the disease itself. Current anti-fibrotic drugs frequently cause debilitating gastrointestinal side effects, with diarrhea reported in over 60% of patients taking nintedanib, often leading to dose reductions or discontinuation. Chronic cough is another common and distressing symptom of the disease that can be exacerbated by some treatments.

The Phase 2a trial data for GRI-0621 suggests a dramatically improved tolerability profile. The study met its primary safety endpoint, showing the drug was well tolerated over 12 weeks. Crucially, there was no increase in cough in the GRI-0621 arm compared to 25% in the placebo arm. Likewise, diarrhea was reported in only 13% of subjects on the drug versus 33% on placebo, a significant potential advantage, especially since 80% of participants were also taking existing standard-of-care medications.

Beyond its safety, the drug demonstrated a tangible impact on lung function, a key measure for patients. The study tracked changes in Forced Vital Capacity (FVC), the maximum amount of air a person can forcibly exhale. A decline in FVC is a direct marker of disease progression and mortality risk. While placebo-treated subjects predominantly saw their lung function worsen, with 80% experiencing a decline in FVC, the results for the treatment group were starkly different. Nearly 40% of subjects receiving GRI-0621 experienced an increase in FVC over the 12-week period. Overall, the placebo-adjusted change from baseline FVC saw a notable increase of 99 ml in the GRI-0621 arm.

A Promising Candidate in a Competitive Field

The positive results position GRI Bio in an increasingly active and competitive landscape for fibrotic diseases. Other companies, such as Pliant Therapeutics and Boehringer Ingelheim, have also recently reported encouraging mid-stage data for their own novel IPF therapies. However, GRI-0621's distinct mechanism of action and data suggesting true disease modification could set it apart.

The potential for a therapy that not only slows decline but actively repairs tissue and improves lung function, all with a superior safety profile, represents the holy grail in IPF research. “The positive Phase 2a results represent an important milestone for our IPF program and a compelling early signal of GRI-0621’s disease-modifying potential,” commented Marc Hertz, PhD, Chief Executive Officer of GRI Bio. “These results reinforce our belief in GRI-0621’s differentiated mechanism and support its potential to go beyond slowing disease progression by directly impacting core drivers of IPF.”

The Long Road from Trial Data to Treatment

While the Phase 2a results are highly encouraging, it is important to note that they are from a small study of 35 subjects. The path to bringing a new drug to market is long, arduous, and expensive. GRI Bio's next step will be to meet with regulatory bodies like the U.S. Food and Drug Administration to discuss the data and design a much larger, multi-center Phase 3 clinical program. These pivotal trials, which can take several years and cost hundreds of millions of dollars, are required to definitively confirm the drug's safety and efficacy before it can be considered for approval.

According to recent financial filings, GRI Bio's current cash runway is projected to last into the first quarter of 2026. This timeline underscores the urgency for the company to secure substantial additional funding or a strategic partnership with a larger pharmaceutical firm to underwrite the costly next stage of development. However, the strength of this data, which CEO Marc Hertz described as “mechanistic proof-of-biology,” provides a powerful catalyst for attracting that necessary investment. For the thousands of patients and families affected by IPF, these results represent a tangible step forward and a renewed sense of optimism in the fight against this devastating disease.