A pharmacokinetics study to evaluate drug–drug interactions between fipaxalparant and concomitant medications in healthy participants

Fipaxalparant, a small molecule and negative allosteric modulator of lysophosphatidic acid receptor 1, is being evaluated in phase 2 clinical trials of idiopathic pulmonary fibrosis (IPF) and diffuse cutaneous systemic sclerosis. This phase 1, open-label, crossover, 3-cohort study in healthy adults evaluated mutual drug-drug interactions (DDIs) between fipaxalparant and the IPF medications pirfenidone and nintedanib, as well as the effects of itraconazole (P-glycoprotein inhibitor) and rifampin (potent organic anion transporting polypeptide [OATP] inhibitor) on fipaxalparant. Participants received a single oral dose of fipaxalparant 300 mg. Overall, 16, 20, and 15 participants completed the study in cohorts 1, 2, and 3, respectively. The study demonstrated no relevant mutual DDIs between fipaxalparant and pirfenidone/nintedanib at clinical doses. There was no effect of itraconazole 400 mg on fipaxalparant exposure. A single rifampin 600 mg dose caused 1.48-fold and 1.86-fold increases in fipaxalparant C_max and AUC_0-∞, respectively. Treatment-emergent adverse events were mild/moderate with fipaxalparant alone or with the other study drugs. Overall, fipaxalparant absorption in vivo occurs independently of the P-glycoprotein-mediated gut efflux pathway, and fipaxalparant is a clinically relevant OATP substrate. Results of this DDI study will inform the management of concomitant medications of ongoing/future trials of fipaxalparant.