Direct Demonstration of Tissue Uptake of an Inhaled Drug: Proof-of-Principle Study Using Matrix-Assisted Laser Desorption Ionization Mass Spectrometry Imaging

Abstract

Drug therapy is often directed to specific organ and tissue compartments where the mode of action of the compound affects specifically targeted biological processes. However, the direct measurement of drug uptake in terms of a time kinetic and concentrations attained at the local sites has not been readily available as a clinical index for most drugs. A proof-of-principle study was conducted to test the utility of applying matrix-assisted laser desorption ionization-mass spectrometry imaging (MALDI-MSI) to demonstrate the qualitative distribution pattern of a locally administered drug within tissue sites of targeted action. Here we have measured the occurrence of an inhaled bronchodilator, the muscarinic receptor antagonist ipratropium, within human bronchial biopsies obtained by fiber optic bronchoscopy shortly after dosing exposure. Cryo-preserved biopsy samples from five subjects being evaluated for airway obstruction or potential tumor development were prepared as thin frozen sections. Samples coated with a MALDI matrix were analyzed by a MALDI LTQ Orbitrap XL mass spectrometer at large (100 μm) and small (30 μm) raster sizes. Our results demonstrate that ipratropium is rapidly absorbed into the airway wall. Ipratropium parent ion (m/z 332.332) and daughter ions (m/z 166.2 and 290.2) were coincidently partitioned within submucosal spaces containing targeted airway smooth muscle in four out of five subjects. The signal intensity of ipratropium fragment ions provided estimates that local drug concentrations between 3 and 80 nM were achieved within the airway wall. To our knowledge, this is the first reported study in applying MALDI-MSI to demonstrate the localization of a drug administered at therapeutic levels. The study highlights the potential benefit of MALDI-MSI to provide important measurements of drug efficacy in clinical settings.

New techniques for studying airway drug pharmacokinetics for asthma therapeutics

“…However, although cumbersome, temporal information from in vivo experiments can be collected and, by this, drug-tissue interactions be described in more detail [12]. Several successful attempts have been made in the lung, where the tissue localization of an inhaled anticholinergic was determined in a rodent inhalation model [13,14], as well as in a clinical study in COPD patients inhaling therapeutic doses [12,15]. The above mentioned in situ techniques are explained in an excellent review paper by Solon et al [16].…”

Imaging Techniques for Evaluation of Drug Distribution in Solid Tumor

“…The distribution of the multiple-receptor tyrosine kinase inhibitor AEE788 in rodent prostate cancer models was analyzed by MALDI-MSI (35). The tyrosine kinase inhibitors erlotinib and gefitinib have been analyzed, after depositing single droplets of drugs on tissue slices of planocellular lung carcinoma, adeno-carcinoma and large cell lung carcinoma (36)(37)(38). Yasunaga et al (39) showed that paclitaxel-incorporating micelles deliver more paclitaxel to the tumor and less paclitaxel to normal tissue, as compared with treatment with paclitaxel alone.…”

Drug compound characterization by mass spectrometry imaging in cancer tissue

“…Consequently, quantitative MSI was rapidly applied to evaluate the distribution of drug compounds (Solon et al 2010;Nilsson et al 2010;Koeniger et al 2011;Takai et al 2012;Lietz et al 2013). Recently, high resolution MSI provided a significant advantage of autoradiography from the aspect of the drug metabolites (Fehniger et al 2011;Jirasko et al 2014;Liu et al 2013;Buck et al 2015) and demonstrated the distribution of a confirmed drug metabolite that possibly lead to the drug toxicity (Török et al 2015). The technology is today making important contributions in fields such as PK screening (Castellino et al 2013), novel pro-drug concepts (Nilsson et al 2010;Fehniger et al 2011), drug delivery systems (DDS) by micellar nanoparticle formulation (Swales et al 2014), biomarkers for PD (Yasunaga et al 2013;Shariatgorji et al 2014;Cobice et al 2013) as well as proteomics (Goto et al 2014;Ye et al 2014).…”

“…Patients in feasibility studies in combination with disease models in rodents has been the strategy of our research teams for a number of years (Fehniger et al 2011;Marko-Varga et al 2012;Sugihara et al 2014;Török et al 2015). Further, the correlation in-between a given rodent model with administered drug and the ability to utilize controlled administrations to tissue sections from organs isolated with the intact tumor environment is a valuable tool for drug characterizations.…”

“…MALDI-MSI studies on the clinical status and as risk assessments with respect to disease developments, e.g., cancer states of tumor genesis (Fehniger et al 2011), and drug responders, as well as long-term survival (Marko-Varga et al 2012;Sugihara et al 2014). In addition to our own melanoma studies, studies undertaken by Caprioli et al, was first to present MALDI-MSI data where they used metastatic tumors, identifying calcyclin (Hardesty and Caprioli 2008;Lazova et al 2012).…”