Enhanced anticancer efficacy of histone deacetyl inhibitor, suberoylanilide hydroxamic acid, in combination with a phosphodiesterase inhibitor, pentoxifylline, in human cancer cell lines and in-vivo tumor xenografts.

Vorinostat [suberoylanilide hydroxamic acid (SAHA)], a histone deacetylase inhibitor, shows limited clinical activity against solid tumors when used alone. The methyl xanthine drug, pentoxifylline (PENT), has been described to have antitumor properties. The aim of this study was to look for the enhanced anticancer activities of both agents when used in combination at doses lower than their respective efficacy dose when used alone. We investigated the antitumor potential of this novel combination in vitro and in vivo. The combination index was assessed for these two drugs to look for synergistic antiproliferative activity against a broad spectrum of human cancer cell lines. Consistent additive to synergistic interactions were observed in HCT116 cells when PENT was combined with SAHA at all drug tested concentrations. The combination of SAHA and PENT induces chromatin condensation and apoptosis downstream of the pan histone deacetylase inhibition and phosphodiesterase regulation, leading to subsequent cell cycle arrest at their lower tested concentrations. Further, the ability of this combination to inhibit angiogenesis, both in vitro and in vivo, was examined and a significant inhibition in tube formation in HUVEC cells and neovascularization of Matrigel plug was observed. A significant inhibition in tumor growth was observed in severe combined immunodeficient mice bearing HCT116 (colon) and PC3 (prostate) human xenografts treated with SAHA (30 mg/kg, intraperitoneal) in combination with PENT (60 mg/kg, intraperitoneal), with no loss in body weight and 100% survival. In conclusion, these findings indicate the enhanced anticancer activity of SAHA in combination with PENT both in vitro and in vivo.

Method development and validation of almotriptan in human plasma by HPLC tandem mass spectrometry: application to pharmacokinetic study.

A simple, sensitive and selective method has been developed for quantification of Almotriptan (AL) in human plasma using Almotriptan-d(6) (ALD6) as an internal standard. Almotriptan and Almotriptan-d(6) were detected with proton adducts at m/z 336.1→201.1 and 342.2→207.2 in multiple reaction monitoring (MRM) positive mode, respectively. The method was linear over a concentration range of 0.5-150.0 ng/mL. The limit of detection (LOD) and limit of quantification (LOQ) for Almotriptan were 0.2 pg/mL and 0.5 ng/mL, respectively. Liquid-liquid extraction was used followed by MS/MS (ion spray). The method was shown to be precise with an average within-run and between-run variation of 0.68 to 2.78% and 0.57 to 0.86%, respectively. The average within-run and between-run accuracy of the method throughout its linear range was 98.94 to 102.64% and 99.43 to 101.44%, respectively. The mean recovery of drug and internal standard from human plasma was 92.12 ± 4.32% and 89.62 ± 6.32%. It can be applied for clinical and pharmacokinetic studies.

Development and validation of a stability-indicating liquid chromatographic method for determination of emtricitabine and related impurities in drug substance.

A novel stability-indicating high-performance liquid chromatographic (HPLC) method was developed and validated for assay and determination of impurities of emtricitabine in drug substance. Emtricitabine was found to be degraded under acidic, alkaline, and oxidative stress conditions and to be more labile under oxidative conditions. The drug proved to be stable to dry heat and photolytic degradation. Resolution of major and minor degradation impurities was achieved on an Intersil ODS-3V column utilizing 10 mM sodium phosphate buffer and methanol (85:15) as mobile phase. Detection was at 280 nm. Validation studies were performed as per ICH recommended conditions. The developed method was found to be linear, accurate, specific, selective, precise, and robust.