A subnanogram API LC/MS/MS quantitation method for depsipeptide FR901228 and its preclinical pharmacokinetics

Area of Science:

• Analytical Chemistry
• Pharmacokinetics
• Mass Spectrometry

Background:

• Depsipeptide FR901228 (FR) is a naturally occurring antitumor agent.
• Accurate quantitation of FR in biological matrices is crucial for pharmacokinetic studies.
• Existing methods may lack the sensitivity or specificity required for low-dose analysis.

Purpose of the Study:

• To develop and validate a highly sensitive and specific analytical method for FR quantitation in human and rat plasma.
• To apply the validated method for pharmacokinetic profiling of FR following intravenous and oral administration in rats.

Main Methods:

• Extraction of FR and internal standard (t-Boc-Met-Leu-Phe) from plasma using ethyl acetate.
• Separation using a C8 Spherisorb column with isocratic elution (methanol/acetonitrile/ammonium acetate).
• Quantitation by atmospheric pressure ionization (API) liquid chromatography-tandem mass spectrometry (LC/MS/MS) in multiple-reaction monitoring (MRM) mode.

Main Results:

• The LC/MS/MS method demonstrated high sensitivity (LOQ of 0.1 ng/ml in human plasma) and specificity.
• Linear calibration curves were obtained over the range of 0.1-100.0 ng/ml (human) and 0.5-100.0 ng/ml (rat).
• Pharmacokinetic studies in rats showed biexponential decline after i.v. dose (t(1/2) = 187.7 min) and low oral bioavailability (1.6% at 5 mg/kg, 10.6% at 50 mg/kg).

Conclusions:

• The developed API LC/MS/MS method is suitable for sensitive and specific quantitation of FR in plasma.
• The method facilitates pharmacokinetic investigations of FR in preclinical models.
• FR exhibits limited oral bioavailability, suggesting challenges for oral drug delivery.