An orthogonal methods assessment of topical drug concentrations in skin and the impact for risk assessment in the viable epidermis.

Systemic toxicity assessments for oral or parenteral drugs often utilize the concentration of drug in plasma to enable safety margin calculations for human risk assessment. For topical drugs, there is no standard method for measuring drug concentrations in the stratum basale of the viable epidermis. This is particularly important since the superficial part of the epidermis, the stratum corneum (SC), is nonviable and where most of a topically applied drug remains, never penetrating deeper into the skin. We investigated the relative concentrations of a prototype kinase inhibitor using punch biopsy, laser capture microdissection, and imaging mass spectrometry methods in the SC, stratum basale, and dermis of minipig skin following topical application as a cream formulation. The results highlight the value of laser capture microdissection and mass spectrometry imaging in quantifying the large difference in drug concentration across the skin and even within the epidermis, and supports use of these methods for threshold-based toxicity risk assessments in specific anatomic locations of the skin, like of the stratum basale.

A sensitive method for the quantitation of the peptide-based glucagon-like peptide-1 receptor agonist liraglutide in plasma using microfluidics chromatography tandem MS.

AIM: An LC-MS/MS assay for the quantitation of liraglutide, a peptide-based injectable glucagon-like peptide-1 receptor agonist, has been developed as a convenient alternative to the enzyme-linked immunosorbent assay, and used to characterize liraglutide pharmacokinetics in cynomolgus monkeys. RESULTS: Assay calibration curves exhibited a linear dynamic range of 10-5000 ng/ml and correlation coefficient ≥0.98. Following a 30 µg/kg intravenous dose, liraglutide demonstrated low plasma clearance and distribution volume, which led to a terminal half-life of 6.59 h in monkeys. CONCLUSION: The dynamic range of our LC-MS/MS assay provides sufficient coverage of the average efficacious liraglutide concentrations in human plasma, and can be used for pharmacokinetics/pharmacodynamics studies in animals and potentially in humans.

A highly selective and sensitive LC-MS/HRMS assay for quantifying coproporphyrins as organic anion-transporting peptide biomarkers.

AIM: Coproporphyrin-I (CP-I) and coproporphyrin-III (CP-III) in plasma and urine have been proposed as biomarkers for assessing drug-drug interactions involving hepatic drug transporters such as organic anion-transporting peptides (OATP), 1B1 and 1B3. Materials & methods: Plasma and urine extracts were analyzed for CP-I/CP-III using a TripleTOF API6600 mass spectrometer. Results: Previously unreported, CP-I/CP-III doubly charged ions (m/z 328.14) were used as precursor ions to improve the assay sensitivity and selectivity over the singly charged precursor ions (m/z 655.28). Levels of CP-I and CP-III measured ranged 0.45-1.1 and 0.050-0.50 ng/ml in plasma and 5-35 and 1-35 ng/ml in urine, respectively. CONCLUSION: The described highly selective and sensitive CP-I/CP-III LC-HRMS assay offers options for earlier characterization and clinical safety projections for OATP1B1/3-mediated drug-drug interactions along with pharmacokinetic analyses of a new chemical entity as part of first-in-human clinical studies.