Potent, Metabolically Stable 2-Alkyl-8-(2H-1,2,3-triazol-2-yl)-9H-adenines as Adenosine A2A Receptor Ligands.

Inhibition of adenosine A2A receptors has been shown to elicit a therapeutic response in preclinical animal models of Parkinson's disease (PD). We previously identified the triazolo-9H-purine, ST1535, as a potent A(2A)R antagonist. Studies revealed that ST1535 is extensively hydroxylated at the ω-1 position of the butyl side chain. Here, we describe the synthesis and evaluation of derivatives in which the ω-1 position has been substituted (F, Me, OH) in order to block metabolism. The stability of the compounds was evaluated in human liver microsomes (HLM), and the affinity for A(2A)R was determined. Two compounds, (2-(3,3-dimethylbutyl)-9-methyl-8-(2H-1,2,3-triazol-2-yl)-9H-purin-6-amine (3 b) and 4-(6-amino-9-methyl-8-(2H-1,2,3-triazol-2-yl)-9H-purin-2-yl)-2-methylbutan-2-ol (3 c), exhibited good affinity against A(2A)R (Ki =0.4 nM and 2 nM, respectively) and high in vitro metabolic stability (89.5% and 95.3% recovery, respectively, after incubation with HLM for two hours).

Development and validation of a liquid chromatography-tandem mass spectrometry method for the determination of ST1926, a novel oral antitumor agent, adamantyl retinoid derivative, in plasma of patients in a Phase I study.

E-3-(4'-Hydroxy-3'-adamantylbiphenyl-4-yl) acrylic acid (ST1926) is a novel oral synthetic adamantyl retinoid derivative, now under early clinical investigation in patients with ovarian cancer. To investigate the pharmacokinetics of this new antitumor agent in human plasma, we developed and validated a high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method based on the addition of ST2222 as internal standard and simple protein precipitation with methanol. The method requires a small volume of sample (100microL); it is rapid and selective, allowing a good resolution of peaks from the plasma matrix in 9min. The method offers high recovery (>90%), it is sensitive, precise and accurate with overall precision expressed as CV% less than 8.2%. We set the lower limit of quantitation at 20.0ng/mL and validated the assay up to the concentration of 1000.0ng/mL. The present method has been successfully applied to study ST1926 pharmacokinetics in patients with advanced ovarian cancer in a Phase I trial, administering the drug orally for five consecutive days. During analysis of the study samples, it became evident the presence of glucuroconjugates of the parent compound, established by LC-Orbitrap MS. Preliminary results show low and variable drug absorption in patients, with extensive glucuroconjugation influencing the bioavailability of ST1926.

Determination of total and lactone form of a new camptothecin derivative gimatecan (ST1481) and its metabolite ST1698 in human plasma by high-performance liquid chromatography with fluorimetric detection.

A new sensitive high-performance liquid chromatographic (HPLC) method for the determination of gimatecan (ST1481), a new camptothecin derivative, and its metabolite (ST1698) in plasma sample has been developed. The method consisted of on-line column solid phase extraction of analytes from human plasma, chromatographic separation by isocratic elution, then fluorimetric detection. The limits of quantitation were 0.25 ng/mL for both the analytes. The recovery of the extraction procedure was in the range of 62.8-71.1% for all the compounds. Good linearity (R(2)>0.999) was observed within the calibration ranges studied: 0.25-25 ng/mL for both ST1481 and ST1698. Precision was in the range 1.2-4.3%, and accuracy was always lower than 4.7%. Surprisingly, after administration of ST1481 to humans, plasma concentrations found were higher than expected, while metabolite plasma concentrations were negligible. For this reason, a second calibration curve range was validated to quantify ST1481 in human plasma, ranging from 5 to 200 ng/mL. A good accuracy and precision were obtained, confirming the usefulness of the procedure. By using neutral analytical condition the intact lactone form was estimated in plasma samples from a patient. The lactone form amounted to 80-100% of the total ST1481.