PT - JOURNAL ARTICLE AU - M. Begg AU - R. Wilson AU - J.N. Hamblin AU - M. Montembault AU - J. Green AU - A. Deans AU - A. Amour AU - S. Worsley AU - K. Fantom AU - Y. Cui AU - G. Dear AU - S. Ahmad AU - A. Kielkowska AU - J. Clark AU - M. Boyce AU - A. Cahn AU - E.M. Hessel TI - Relationship between Pharmacokinetics and Pharmacodynamic Responses in Healthy Smokers Informs a Once-Daily Dosing Regimen for Nemiralisib AID - 10.1124/jpet.118.255109 DP - 2019 Jun 01 TA - Journal of Pharmacology and Experimental Therapeutics PG - 337--344 VI - 369 IP - 3 4099 - http://jpet.aspetjournals.org/content/369/3/337.short 4100 - http://jpet.aspetjournals.org/content/369/3/337.full SO - J Pharmacol Exp Ther2019 Jun 01; 369 AB - Nemiralisib (GSK2269557), a potent inhaled inhibitor of phosphoinositide 3-kinase δ (PI3Kδ), is being developed for the treatment of respiratory disorders including chronic obstructive pulmonary disease. Determining the pharmacokinetic (PK) and pharmacodynamic (PD) responses of inhaled drugs early during drug development is key to informing the appropriate dose and preferred dose regimen in patients. We set out to measure PD changes in induced sputum in combination with drug concentrations in plasma and bronchoalveolar lavage (BAL) taken from healthy smokers (n = 56) treated for up to 14 days with increasing doses of inhaled nemiralisib (0.1–6.4 mg). Induced sputum analysis demonstrated a dose-dependent reduction in phosphatidylinositol-(4,5)-trisphosphate (PIP3, the product of PI3K activation), with a maximum placebo-corrected reduction of 23% (90% confidence interval [CI], 11%–34%) and 36% (90% CI, 11%–64%) after a single dose or after 14 days of treatment with nemiralisib, respectively (2 mg, once daily). Plasma analysis suggested a linear PK relationship with an observed accumulation of ∼3- to 4.5-fold (peak vs. trough) in plasma exposure after 14 days of nemiralisib treatment. The BAL analysis at trough confirmed higher levels of the drug in the lungs versus plasma (32-fold in the BAL fluid component, and 214-fold in the BAL cellular fraction). A comparison of the drug levels in plasma and the reductions in sputum PIP3 showed a direct relationship between exposure and PIP3 reduction. These results demonstrated target engagement upon treatment with inhaled nemiralisib and provide confidence for a once-daily dosing regimen.