Determination of Lekethromycin, a Novel Macrolide Lactone, in Rat Plasma by UPLC-MS/MS and Its Application to a Pharmacokinetic Study

Abstract

Lekethromycin, a new macrolide lactone, exhibits significant antibacterial activity. In this study, a reliable analytical ultrahigh-performance liquid chromatography electrospray ionization quadrupole Orbitrap high-resolution mass spectrometry (UPLC-ESI-Orbitrap-MS) method was established and validated for the detection of lekethromycin in rat plasma. After a simple acetonitrile (ACN)-mediated plasma protein precipitation, chromatographic separation was performed on a Phenomenex Luna Omega PS C18 column (30 × 2.1 mm i.d. particle size = 3 μm) conducted in a gradient elution procedure using 0.5% formic acid (FA) in ACN and 0.5% FA in water as the mobile phase pumped at a flow rate of 0.3 mL/min. Detection was carried out under positive electrospray ionization (ESI+) conditions in parallel reaction monitoring (PRM) mode with observation of m/z 804.5580 > 577.4056 for lekethromycin and 777.5471 > 619.4522 for gamithromycin (internal standard, IS). The linear range was 5–1000 ng/mL (r2 > 0.99), and the lower limit of quantification (LLOQ) was 5 ng/mL. The intra- and inter-day precision (expressed as relative standard deviation, RSD) values were ≤7.3% and ≤6.3%, respectively, and the accuracy was ≥90% ± 5.3%. The mean extraction recovery RSD valWeue was <5.1%. Matrix effects and dilution integrity RSD values were <5.6% and <3.2%, respectively. Lekethromycin was deemed stable under certain storage conditions. This fully validated method was effectively applied to study the pharmacokinetics of lekethromycin after a single intravenous administration of 5 mg/kg in rats. The main pharmacokinetic parameters were T1/2λz, CL_obs and VZ_obs were 32.33 ± 14.63 h, 0.58 ± 0.17 L/h/kg and 25.56 ± 7.93 L/kg, respectively.

Plasma Protein Binding Rate and Pharmacokinetics of Lekethromycin in Rats

“…Similar to tulathromycin, tulathromycin was metabolized at a lower level and was primarily eliminated in pigs [ 14 ]. Low clearance of LKMS in rats is consistent with LKMS being insignificantly degraded and behaving with high metabolic stability [ 16 ]. It was therefore hypothesized that LKMS does not interact with metabolic enzymes and undergoes extensive metabolism.…”

“…Our lab has developed and validated a reliable and sensitive method to determine LKMS plasma concentration in rats [ 16 ], and the method was thoroughly verified for specificity, linearity, accuracy, precision, matrix effect, extraction recovery, dilution integrity, and storage stability, which was still employed to examine the LKMS concentration in this work.…”

Inhibitory Mechanisms of Lekethromycin in Dog Liver Cytochrome P450 Enzymes Based on UPLC-MS/MS Cocktail Method

“…Lekethromycin (LKMS), a derivative synthetic novel macrolide compound, has been used in veterinary medicine to treat respiratory disease. Pharmacokinetic and distribution studies have been completed on healthy and infected rats with different administration methods and doses, respectively [1][2][3], suggesting that LKMS exhibits widely distributed effects and has a high plasma protein binding rate and low clearance. A high plasma protein binding rate typically means that there is less drug in the free state in plasma, and a DDI should be considered when co-administrating [4].…”