LC-MS/MS method for quantitation of mycophenolic acid, mycophenolic acid acyl-glucuronide, and 7-O-mycophenolic acid glucuronide in serum

Therapeutic drug monitoring of mycophenolic acid and azole antifungals on two distinct LC-MS/MS instruments

Background

As an active metabolite of a commonly prescribed immunosuppressant, mycophenolic acid (MPA) levels are often monitored to prevent organ rejection following a transplant. Triazoles are often prescribed for treatment of invasive fungal infections in immunocompromised patients. Due to the variability in individual pharmacokinetics and drug-drug interactions, therapeutic drug monitoring is recommended for triazole antifungals. A multiplex LC-MS/MS assay has been developed that can quantify both MPA and triazole drugs in serum.

Methods

A sample preparation procedure was established to spike in internal standard compounds and precipitate proteins. Reversed-phase chromatographic separation was performed on a C18 column with an analysis time of five minutes per sample. The mass spectrometer was operated in multiple reaction monitoring mode. The method was validated on two HPLC systems interfaced with either a Triple Quad 6500 or an API 4000 instrument.

Results

The multiplex assay was linear over a wide dynamic range with analyte measurable ranges of 0.4-48 μg/mL for MPA, 0.1-12 μg/mL for posaconazole, and 0.2-24 μg/mL for voriconazole, itraconazole, hydroxyitraconazole, and isavuconazole. The between-day and intraday imprecisions were less than 10 %. Limits of detection were below 0.04 ug/mL with limits of quantitation below 0.2 μg/mL. Method comparison studies against the current in-house method met acceptance criteria. The instrument comparison study demonstrated a strong correlation between data collected from the two systems.

Conclusion

A robust multiplex LC-MS/MS assay was developed and validated for monitoring MPA and triazoles drug levels in a clinical laboratory. The assay performance on two distinct instruments was acceptable and comparable.

Quantification of Mycophenolic Acid in Plasma by High Performance Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

Mycophenolate mofetil (MMF) and sodium mycophenolate are commonly prescribed immunosuppressive drugs for patients who have undergone solid organ transplant. Therapeutic drug monitoring (TDM) of these drugs is performed by assessing mycophenolic acid (MPA) in plasma. Due to the large inter-individual variability and narrow therapeutic range, the precise determination of systemic MPA concentration carries great clinical significance. We present a rapid, sensitive, specific, and robust liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantitation of MPA in plasma. A Waters Xevo TQ-S Micro mass spectrometer coupled to a Water's Acquity liquid chromatography system was used in positive electrospray ionization (ESI) mode. MPA quantitation was achieved using multiple reaction monitoring (MRM). Mycophenolic acid carboxybutoxy ether (MPAC) was employed as an internal standard. The method is linear from 0.25 to 40.00 mg/L, has intra-assay (N = 24) imprecision of 2.7% at 1.57 mg/L and 3.9% at 4.61 mg/L and inter-assay (N = 20 days) imprecision of 4.0% at 1.62 mg/L and 5.6% at 4.68 mg/L.

Volumetric Absorptive Microsampling to Enhance the Therapeutic Drug Monitoring of Tacrolimus and Mycophenolic Acid: A Systematic Review and Critical Assessment

BACKGROUND

Volumetric absorptive microsampling (VAMS) is an emerging technique that may support multisample collection to enhance therapeutic drug monitoring in solid organ transplantation. This review aimed to assess whether tacrolimus and mycophenolic acid can be reliably assayed using VAMS and to identify knowledge gaps by providing granularity to existing analytical methods and clinical applications.

METHODS

A systematic literature search was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The PubMed, Embase, and Scopus databases were accessed for records from January 2014 to April 2022 to identify scientific reports on the clinical validation of VAMS for monitoring tacrolimus and mycophenolic acid concentrations. Data on the study population, sample sources, analytical methods, and comparison results were compiled.

RESULTS

Data from 12 studies were collected, including 9 studies pertaining to tacrolimus and 3 studies on the concurrent analysis of tacrolimus and mycophenolic acid. An additional 14 studies that provided information relevant to the secondary objectives (analytical validation and clinical application) were also included. The results of the clinical validation studies generally met the method agreement requirements described by regulatory agencies, but in many cases, it was essential to apply correction factors.

CONCLUSIONSS

Current evidence suggests that the existing analytical methods that use VAMS require additional optimization steps for the analysis of tacrolimus and mycophenolic acid. The recommendations put forth in this review can help guide future studies in achieving the goal of improving the care of transplant recipients by simplifying multisample collection for the dose optimization of these drugs.