In vivo pharmacokinetic and pharmacodynamic study of co-spray-dried inhalable pirfenidone microparticles in rats

Pirfenidone (PRF) is the first FDA-approved API in the treatment of idiopathic pulmonary fibrosis (IPF). However, PRF induces serious side effects, such as photophobia and gastrointestinal disorder. PRF inhalation can be expected with a lower effective dose and reduced side effects. In this study, PRF was prepared as inhalable co-spray-dried particles for dry powder inhalation. Mannitol, L-leucine (Leu), and NaCl were used as a stabilizer. The kinds and ratios of stabilizers affecting the physicochemical properties of particles were analyzed, including particle size and surface composition, because of the surface enrichment properties of Leu, the most effective stabilizer. The co-spray-dried PRF and Leu microparticle (SD-PL1:1) have the smallest size and highest aerosol performance. The bioavailability was confirmed by in vivo pharmacokinetics (PK) studies. In addition, in vivo pharmacodynamics (PD) experiments were conducted using a bleomycin-induced IPF rat model. In vivo PK experiments demonstrated that pulmonary administration of SD-PL1:1 was 4 times more effective than the oral route. Similar to the PK results, the therapeutic effect was improved when SD-PL1:1 was administered via the pulmonary route compared to the oral route.