Background Transforming growth factor-β1 (TGF-β1) contributes to more severe pulmonary disease in people with cystic fibrosis (pwCF). Our preclinical in vitro and in vivo studies demonstrated that losartan could reverse TGF-β1-mediated mucociliary dysfunction, albeit at doses difficult to achieve by oral administration. This study therefore examined airway losartan concentrations after oral and inhaled dosing to evaluate if oral losartan could be even expected to improve mucociliary clearance. Methods We conducted comparative pharmacokinetics studies in sheep assessing airway surface liquid (ASL) concentrations of losartan and its metabolites, EXP3179 and EXP3174, after oral and inhaled administration. Another pharmacokinetic study used oral losartan to compare serum levels in pwCF on and off CFTR modulators and healthy volunteers. Finally, an open-label clinical trial evaluated effects of oral losartan (50 mg twice daily for 14 weeks) on mucociliary and cough clearance (MCC/CC) in pwCF off CFTR modulators as they have a need for novel therapies (NCT03435939). Results In sheep, oral losartan (50 mg twice daily for 4 days) did not achieve ASL levels expected to improve CF-associated mucociliary dysfunction based on our previous data. In humans, single dose pharmacokinetics of oral losartan showed differential results in pwCF and healthy volunteers, with pwCF off CFTR modulators achieving the lowest serum levels of losartan and EXP3174 with a complete absence of EXP3179, the anti-inflammatory metabolite of losartan. The open label study included seven participants. Serum concentrations of losartan and EXP3174 at week 14 matched levels observed in pwCF not on modulators in the pharmacokinetic study. As expected, no improvements in whole-lung or peripheral MCC/CC were found in participants with complete datasets. PpFEV1 remained unchanged, but nasal TGF-β1 levels significantly decreased with treatment, although systemic inflammatory markers were unaffected (C-reactive protein, calprotectin, and serum amyloid A). Conclusion Reduced drug exposure compared to healthy volunteers reflects altered pharmacokinetics in pwCF. Nevertheless, oral losartan at clinically approved doses does not achieve airway concentrations needed to restore mucociliary function in any individual, and especially not in pwCF off modulators. Future studies should consider inhaled drug delivery to achieve therapeutically meaningful airway exposure to losartan and its metabolites.
Bengtson et al. (Mon,) studied this question.