Drug Delivery Systems, Everolimus Eluting Coronary Stent

Challenge

A client requested LC-MS/MS bioanalysis to support a medical device study targeting the drug delivery of an anti-angiogenic agent, Everolimus, to the site of a pre-implanted cardiovascular stent, specifically an Everolimus-eluting coronary stent. Everolimus is an immunosuppressant macrolide compound commonly indicated to prevent in-stent restenosis. The study focused on evaluating the effectiveness of drug delivery systems, particularly Everolimus-eluting stents, in precisely delivering Everolimus to the targeted site, highlighting the importance of an Everolimus assay in assessing drug distribution and accumulation. Since this drug has a narrow therapeutic window and exhibits frequent toxicity in oral administration, it is essential to monitor its concentration, distribution, and accumulation in the body to ensure the safety and efficacy of the Everolimus stent for precision-targeted drug delivery. An additional challenge is introduced by the well-documented tendency for Everolimus to accumulate in erythrocytes, making whole blood analysis more representative than the standard plasma matrix analysis in Everolimus testing. The study was performed in a porcine model and involved analysis of Everolimus concentrations in 9 different complex matrices (8 tissue types and whole blood). The Everolimus test targeted a lower concentration range than commonly observed for this compound, necessitating minimal sample sizes for some matrices. Such tailored drug delivery devices, exemplified by the Everolimus-eluting coronary stent, aim to enhance therapeutic outcomes while minimizing systemic toxicity, thus underscoring the importance of precise bioanalytical methods, including Everolimus testing, in evaluating efficacy.

Solution

To overcome the challenges of the Everolimus assay in porcine whole blood and tissue homogenates/extracts, our scientists developed and validated a bioanalytical LC-MS/MS method that is simple, sensitive, and specific. This Everolimus test is crucial for assessing drug delivery and efficacy in drug delivery systems or drug delivery devices. This method was particularly tailored for evaluating Everolimus-eluting coronary stents, commonly called Everolimus-eluting stents or Everolimus stents.

The presence of whole cells in the matrix was addressed by the protein precipitation extraction method using a combination cell lysing buffer/organic solvent, ensuring an accurate assessment of drug delivery kinetics in Everolimus testing. We improved accuracy and reproducibility in the presence of complex matrices pertinent to drug delivery systems by utilizing a deuterated internal standard in the Everolimus assay. This minimized matrix effect variability between the analyte and internal standard, thus ensuring precision in the Everolimus testing measurements.

Improved sensitivity was achieved with reverse-phase LC-MS using positive ion mode electrospray ionization (ESI) on a Sciex 6500 mass spectrometer. This allowed for a precise evaluation of drug delivery efficacy in the Everolimus assay. The optimal mass pairing for Everolimus tracked the ammonium adduct of the parent mass, and the LC mobile phase solutions were further adjusted for ammonium content to maximize sensitivity, particularly considering drug delivery devices. According to the FDA guidelines, the Everolimus test method was initially validated at a concentration range of 0.1-20 ng/mL for sensitivity, accuracy, precision, extraction recovery, matrix effect, and stability in porcine whole blood, providing valuable insights into drug delivery dynamics. Tissue homogenates were also prepared in a buffer solution, and further experiments were then performed to validate the Everolimus testing method for a concentration range of 0.5-100 ng/mL in each tissue type.

Outcome

This LC-MS/MS method, specifically tailored for Everolimus assay, was applied to multiple bioanalytical studies to quantify porcine whole blood and tissues with an Everolimus-eluting coronary stent, particularly focusing on drug delivery systems. The results showed high concentrations of Everolimus localized to the arteries where the Everolimus-eluting stent was deployed. This indicated effective drug delivery at the target site. Some additional drug accumulation in lung tissue, with much lower levels in all other tissue matrices. These results indicate that the medical device delivers sirolimus effectively to the target site and additionally demonstrate the reliability and applicability of the LC-MS/MS method for assessing drug distribution in drug delivery devices.

We are well-equipped to conduct Everolimus testing across a broad range of studies and complex matrices, including end-of-study tissue sample analysis that may be key for confirming drug distribution and accumulation in drug delivery systems. Our LC-MS/MS and sample preparation expertise supports reliable and efficient method development for various drugs, routes of administration, and sample types. This capability ensures precise and adaptable Everolimus test solutions tailored to the specific requirements of each study, particularly those involving drug delivery devices like Everolimus stents.