Quantitative determination of CGP 53,437, a new HIV protease inhibitor, in plasma by high-performance liquid chromatography and fluorescence detection

Simple high-performance liquid chromatographic determination of the protease inhibitor indinavir in human plasma

Indinavir is a member of a class of protease inhibitors that actively prevent the acquired immunodeficiency syndrome virion from maturing. A high-performance liquid chromatographic (HPLC) assay was developed and validated for the determination of indinavir in human plasma. Indinavir and the internal standard were isolated from the plasma by ether extraction. The residue after evaporation of ether was reconstituted with buffer and injected onto a C4 reversed-phase column eluted isocratically with a mobile phase consisting of 35:65 (v/v) of acetonitrile and buffer. A wavelength of 210 nm was found to be optimum for detection. The calibration range of this assay was from 10 to 5000 ng/ml and coefficients of variation for the assay ranged from 4.6% to 11.0% for three different drug concentrations and the limit of quantitation was 10 ng/ml. During the validation, short-term stability of the drug in plasma, stability during heat deactivation and on repeated freezing and thawing of plasma was evaluated. The overall recovery of indinavir by the ether extraction method was 91.4%. This HPLC assay was found to be a simple and reproducible method for monitoring indinavir levels in human plasma obtained during clinical trials of the drug.

Quantitative determination of CGP 61755, a protease inhibitor, in plasma and urine by high-performance liquid chromatography and fluorescence detection

A liquid chromatographic assay for the determination of CGP 61755 (I) in plasma and urine is described. A similar method for CGP 53437, another HIV-1 protease inhibitor, has been developed and reported previously. After a deproteinization step, a liquid-liquid extraction is performed. Compound I and the internal standard CGP 55749 (II) are hydrolyzed and the primary amine group derivatized using fluorescamine. Chromatography is achieved by isocratic elution with a mobile phase of 30 mM borax buffer (pH 9)-acetonitrile (58:42, v/v). The derivatives of the compounds I and II fluoresce at 480 nm, on excitation at 395 nm and the retention times under these conditions were approximately 6 and 8 min, respectively. The limit of quantitation (LOQ) which is the lowest concentration of the analyte that can be measured with a coefficient of variation and a deviation from theory of less than 20%, was 15 ng/ml plasma and 20 ng/ml urine. The analyte is stable for at least four months in human plasma and sixteen months in dog plasma samples. Different human plasma sources and three different species (rat, rabbit and dog) were tested and no interference between analyte and plasma constituents was observed.

Ex Vivo anti-HIV Activity of Human Serum Obtained from Normal Volunteers Following Oral Administration of the HIV-1 Protease Inhibitor CGP 53437: Value as Predictor of Antiviral Efficacy

The aim of the study was to determine whether the concentration of CGP 53437 measured in the sera of normal volunteers following oral administration of a single dose, had retained its anti-HIV activity; and whether such results could be of predictive value for future clinical antiviral efficacy studies. CGP 53437 is an inhibitor of HIV-1 protease that suppresses HIV-1 replication in human lymphocytes in vitro at 100 nM. The in vitro anti-HIV activity of human sera obtained from CGP 53437-treated individuals was compared with that of sera spiked with known concentrations of CGP 53437 (in the presence or absence of α-1 acid glycoprotein). It was found that the concentration of the compound measured in the sera from treated individuals provided the expected in vitro anti-HIV activity. These results not only validate our analytical method for detection of CGP 53437, but also support the notion that interaction of CGP 53437 with plasma proteins does not significantly affect its antiviral activity (shift of the ED90 by a factor of three). In conclusion, ex vivo anti-HIV activity determinations of sera containing an HIV protease inhibitor, in conjunction with the pharmacokinetic evaluation during Phase I clinical studies, can provide valuable information regarding the suitability of such inhibitors for further clinical studies.