GRI Bio’s lead candidate, tazarotene, has exhibited disease-modifying potential in a mid-stage study in idiopathic pulmonary fibrosis (IPF).
In the US-based Phase IIa study (NCT06331624), tazarotene demonstrated a favourable safety and tolerability profile, meeting the study’s primary endpoint. The most common treatment-emergent adverse events (TEAEs) were dry skin and lips, as well as joint pain.
There were no increases in coughing or gastrointestinal issues reported in the treatment arm compared with placebo across the 12-week treatment period.
The retinoic acid receptor beta and gamma (RAR-βɣ) dual agonist also triggered biomarker-related changes, as patients on the treatment arm experienced a -3% improvement in PRO-C6 compared with the 12% increase observed in the placebo group.
PRO-C6 is a biomarker of type VI collagen synthesis, so its reduced prevalence signals diminished collagen turnover.
GRI Bio suggested a drop in PRO-C6 indicates “fibrosis resolution”, as well as the induction of alveolar repair.
This impact on type VI collagen remodelling was also seen through a treatment-associated increase in the type VI collagen degradation biomarker, C6M. In the GRI-0621 treatment group, C6M levels were 6% higher than baseline while the figures were 3% lower than baseline in patients receiving placebo.
Alongside its impact on type VI collagen-associated biomarkers, the drug, also known as GRI-0621, caused an uptick in type IV collagen synthesis. This is commonly associated with repair of the basement membrane within the lung’s alveoli.
Through treatment with the small molecule, serum measures of type IV collagen synthesis biomarker, PRO-C4, increased 9% from baseline, while patients receiving placebo plus standard of care (SoC) experienced a 2% decline.
Alongside its impacts on fibrosis and alveolar repair, 39% of patients treated with tazarotene demonstrated an improvement in forced vital capacity (FVC) at the 12-week mark while 80% of those in the placebo arm experienced a FVC decline at the same time point.
80% of patients enrolled onto the study were taking background standard of care (SoC) therapies such as Ofev (nintedanib) or Esbriet (pirfenidone), so GRI-0621’s effects were cumulative across this patient group.
In a 10 December statement, GRI Bio CEO Marc Hertz noted that the positive outcome of the Phase IIa study leaves the company “well positioned” to advance to the next stage of development for GRI-0621.
IPF treatment landscape shifts
Before 2025, the IPF treatment landscape had remained stagnant, with the approvals of SoC medicines such as Roche-owned Genentech’s Esbriet and Boehringer Ingelheim’s Ofev being the last major developments in this disease.
However, this changed when Boehringer’s next-generation IPF therapy, Jascayd (nerandomalist), received clearance from the US Food and Drug Administration (FDA) in October 2025 – making it the first drug to secure an approval in this indication for more than a decade.
More companies are now looking to enter the IPF market, including GRI Bio with tazarotene. Analysts at GlobalData forecast that tazarotene could launch in 2029, bringing in $283m for GRI Bio in 2031.
Meanwhile, United Therapeutics is seeking FDA approval for Tyvaso (inhaled treprostinil) in IPF, which has been on the market for the treatment of pulmonary arterial hypertension since 2009. In the Phase III TETON-1 study, the drug demonstrated a positive impact on both quality of life and FVC.
Admilparant, another investigational IPF therapy by Bristol Myers Squibb, is currently in Phase III trials within the indication.
