The novel lysophosphatidic acid receptor 1-selective antagonist, ACT-1016-0707, has unique binding properties that translate into effective antifibrotic and anti-inflammatory activity in different models of pulmonary fibrosis.

Pulmonary fibrosis encompasses different chronic interstitial lung diseases, and the predominant form, idiopathic pulmonary fibrosis, remains to have a poor prognosis despite 2 approved therapies. Although the exact pathobiological mechanisms are still incompletely understood, epithelial injury and aberrant wound healing responses contribute to the gradual change in lung architecture and functional impairment. Lysophosphatidic acid (LPA)-induced lysophosphatidic receptor 1 (LPA1) signaling was proposed to be a driver of lung fibrosis, and LPA1 antagonists have shown promising antifibrotic profiles in early clinical development. The novel, potent, and selective LPA1 antagonist, ACT-1016-0707, displayed insurmountable LPA1 antagonism in vitro with slow off-rate kinetics, leading to efficient inhibition of LPA1 signaling even in presence of high concentrations of LPA. This binding property translated into potent and highly efficient prevention of LPA-induced skin vascular leakage by ACT-1016-0707 in vivo, differentiating the compound from surmountable LPA1 antagonists. Furthermore, ACT-1016-0707 attenuated proinflammatory and profibrotic signaling in different lung fibrosis models in vitro and in the bleomycin-induced lung fibrosis model in vivo. Based on these data, ACT-1016-0707 shows potential as best-in-class LPA1 antagonist for treatment of fibrotic diseases. SIGNIFICANCE STATEMENT: ACT-1016-0707 is a potent, selective, and insurmountable lysophosphatidic receptor 1 (LPA1) antagonist demonstrating robust antifibrotic and anti-inflammatory activity in different lung fibrosis models in vitro and in vivo. This study is the first to demonstrate functional in vivo evidence of insurmountable LPA1 antagonist superiority by side-by-side comparison with surmountable LPA1 antagonists in highly controlled conditions, suggesting potential for ACT-1016-0707 as best-in-class LPA1 antagonist for treatment of fibrotic diseases.