Treated participants showed preservation of alveolar epithelial type II progenitor cells, which are essential for lung repair and regeneration.
Inhaled LTI-03 has shown the potential to reduce lung scarring and preserve cells critical for repair in idiopathic pulmonary fibrosis (IPF), according to a recent press release from Rein Therapeutics.
The dose-escalation study described both safety and biological activity consistent with LTI-03’s proposed dual mechanism of attenuating fibrosis while protecting alveolar epithelial type II progenitor cells. These early data support the drug’s advancement into global phase 2 evaluation under the RENEW trial.
In the investigation, participants with IPF received inhaled LTI-03 to assess pharmacokinetics, safety, and target engagement. Across dose cohorts, the drug was widely tolerable, and treated patients showed declines in several circulating biomarkers associated with fibrotic activity and inflammation.
Investigators noted that these biomarker changes were accompanied by preservation of alveolar epithelial type II progenitor cells, which play a key role in alveolar regeneration. Unlike current therapies that primarily decelerate disease progression, LTI-03 aims to maintain or restore these regenerative cells. The results suggest pharmacologic engagement of Caveolin-1–linked pathways that modulate fibrosis and epithelial injury responses.
Read more about IPF experimental therapies
LTI-03, made by Rein Therapeutics, is a first-in-class, investigational inhaled peptide therapy derived from the Caveolin-1 protein, a regulator of fibrotic signaling. By targeting this pathway, the agent is intended to disrupt the signaling cascade leading to extracellular matrix deposition while sustaining epithelial progenitor populations. This mechanistic profile positions LTI-03 as a potential disease-modifying therapy rather than merely palliative.
“This new data adds to a growing body of evidence supporting LTI-03’s potential as a differentiated therapy for IPF,” said Brian Windsor, PhD, CEO of Rein Therapeutics. “We’re encouraged to see consistent signals across preclinical and clinical work showing that LTI-03 may not only reduce fibrosis but also help protect the lung cells required for healing. IPF patients urgently need better options, and this work reinforces why we are advancing LTI-03 through our phase 2 RENEW trial.”
These preliminary results highlight a therapeutic strategy that may both mitigate fibrotic remodeling and safeguard lung regenerative capacity. If confirmed in subsequent trials, LTI-03 could represent a meaningful advance in IPF management.
Reference
Rein Therapeutics announces new scientific publication demonstrating LTI-03 may reduce lung scarring and protect cells needed for lung repair in IPF. News release. Rein Therapeutics; Novemmber 6, 2025.