ORKAMBI (ivacaftor-lumacaftor [LUMA]) and KALYDECO (ivacaftor; IVA) are two new 
breakthrough cystic fibrosis (CF) drugs that directly modulate the activity and 
trafficking of the defective CFTR underlying the CF disease state. Currently, no 
therapeutic drug monitoring assays exist for these very expensive, albeit, 
important drugs. In this study, for the first time HPLC and LC-MS methods were 
developed and validated for rapid detection and quantification of IVA and its 
major metabolites hydroxymethyl-IVA M1 (active) and IVA-carboxylate M6 
(inactive); and LUMA in the plasma and sputum of CF patients. With a mobile 
phase consisting of acetonitrile/water:0.1% formic acid (60:40v/v) at a flow 
rate of 1mL/min, a linear correlation was observed over a concentration range 
from 0.01 to 10μg/mL in human plasma (IVA R2>0.999, IVA M1 R2>0.9961, IVA M6 
R2>0.9898, LUMA R2>0.9954). The assay was successfully utilized to quantify the 
concentration of LUMA, IVA, M1 and M6 in the plasma and sputum of CF patients 
undergoing therapy with KALYDECO (IVA 150mg/q12h) or ORKAMBI (200mg/q12h 
LUMA-125mg/q12h IVA). The KALYDECO patient exhibited an IVA plasma concentration 
of 0.97μg/mL at 2.5h post dosage. M1 and M6 plasma concentrations were 0.50μg/mL 
and 0.16μg/mL, respectively. Surprisingly, the ORKAMBI patient displayed very 
low plasma concentrations of IVA (0.06μg/mL) and M1 (0.07μg/mL). The M6 
concentrations (0.15μg/mL) were comparable to those of the KALYDECO patient. 
However, we observed a relatively high plasma concentration of LUMA (4.42μg/mL). 
This reliable and novel method offers a simple and sensitive approach for 
therapeutic drug monitoring of KALYDECO and ORKAMBI in plasma and sputum. The 
introduction of the assay into the clinical setting will facilitate 
pharmacokinetics/pharmacodynamic analysis and assist clinicians to develop more 
cost effective and efficacious dosage regimens for these breakthrough CF drugs.