Automated quantitative determination of a new polyamine biosynthesis inhibitor (CGP 48 664) and a potential metabolite in human and animal plasma by high-performance liquid chromatography

Detection and separation of the S-adenosylmethionine-decarboxylase inhibitor SAM486A in human plasma and urine by reversed-phase ion-pairing high-performance liquid chromatography

A reversed-phase ion-pairing high-performance liquid chromatography method for the detection and separation of SAM486A in human plasma and urine is described. Precipitation of proteins was used for plasma sample preparation. Enrichment of SAM486A on a 5 micro C18 column using 0.05 M NaH(2)PO(4) and 0.005 M pentan-sulfonic acid (pH 3.0) as eluent was followed by isocratic elution onto a 5 micro C18 analytical column using 0.01 M NaH(2)PO(4) and 0.005 M pentan-sulfonic acid (pH 3.0) as eluent. Analysis time was 23.0 +/- 0.1 min. The separation parameters were: capacacity factor = 6.21; plates/m = 15,002; peak tailing = 2.076. The method is linear between 5 ng/ml (detection limit) and 1000 ng/ml.

A phase I study of a new polyamine biosynthesis inhibitor, SAM486A, in cancer patients with solid tumours

Because tumour cell proliferation is highly dependent upon up-regulation of de-novo polyamine synthesis, inhibition of the polyamine synthesis pathway represents a potential target for anticancer therapy. SAM486A (CGP 48664) is a new inhibitor of the polyamine biosynthetic enzyme S-adenosylmethionine decarboxylase (SAMDC), more potent and specific than the first-generation SAMDC inhibitor methylglyoxal (bis) guanylhydrazone (MGBG). Preclinical testing confirmed promising antiproliferative activity. In this phase I study, SAM486A was given 4-weekly as a 120 h infusion. 39 adult cancer patients were enrolled with advanced/refractory disease not amenable to established treatments, PS </= 2, adequate marrow, liver, renal and cardiac function. Doses were escalated in 100% increments without toxicity in 24 pts from 3 mg m(-2)cycle(-1)up to 400 mg m(-2)cycle(-1). At 550 and 700 mg m(-2)cycle(-1)reversible dose-limiting neutropenia occurred. Other toxicities included mild fatigue, nausea and vomiting. No objective remission was seen. Pharmakokinetic analysis showed a terminal half-life of approximately 2 days. AUC and Cmax were related to dose; neutropenia correlated with AUC. The recommended dose for further phase II studies on this schedule is 400 mg m(-2)cycle(-1).

Automating solid-phase extraction: current aspects and future prospects

This paper reviews current trends and techniques in automated solid-phase extraction. The area has shown a dramatic growth the number of manuscripts published over the last 10 years, including applications in environmental science, food science, clinical chemistry, pharmaceutical bioanalysis, forensics, analytical biochemistry and organic synthesis. This dramatic increase of more that 100% per year can be attributed to the commercial availability of higher throughput 96-well workstations and extraction plates that allow numerous samples to be processed simultaneously. These so-called parallel-processing workstations represent the highest throughput systems currently available. The advantages and limitations of other types of systems, including discrete column systems and on-line solid-phase extraction are also discussed. Discussions of how automated solid-phase extractions can be developed, generic approaches to automated solid-phase extraction, and three noteworthy examples of automated extractions are given. The last part of the review suggests possible near- and long-term directions of automated solid-phase extraction.

Population pharmacokinetics/toxicodynamics (PK/TD) relationship of SAM486A in phase I studies in patients with advanced cancers

SAM486A (previously termed CGP 48664), a potent inhibitor of S-adenosylmethionine decarboxylase, is under clinical development for the treatment of advanced refractory malignancies. Hematological toxicity manifested by dose-dependent neutropenia has been observed in phase I studies. Population methods were used to investigate pharmacokinetics (PK) as a prognostic factor for safety end point (hematological toxicity) in patients with advanced cancers. SAM486A plasma concentrations and neutrophil counts were collected from three ascending-dose tolerability and PK studies (study 1: single 5-day continuous intravenous (IV) infusion with doses ranging from 24-700 mg/m2/cycle; study 2: 10-minute to 3-hour IV infusion once weekly with doses ranging from 16-325 mg/m2/week; study 3: 1-hour IV infusion once daily for 5 days with doses ranging from 3.6-202.8 mg/m2/day). The PK of SAM486A were best estimated by a population linear three-compartment model with NONMEM (version 5) using data from 9 patients in studies 1 through 3. The population pharmacokinetic parameters (SD) were CL = 6.2 (0.4) l/h/m2, Q2 = 15.4 (1.5) l/h/m2, Q3 = 33.6 (5.3) l/h/m2, V1 = 9.5 (1.6) l/m2, V2 = 672 (52) l/m2, and V3 = 39.9 (8.3) l/m2, and the corresponding intersubject variability was 45.4%, 74.0%, 85.3%, 80.1%, 37.0%, and 103%, respectively, where CL is total body clearance, Q2 and Q3 are intercompartmental clearances, and V1, V2, and V3 are the volumes of distribution in central and peripheral compartments, respectively. The intrasubject variability was 24.0%. The cumulative AUC before the onset of neutrophil nadir count (AUC) and the duration of exposure over threshold SAM486A concentrations in the range of 0.05 to 0.1 microM based on Bayesian PK parameter estimates significantly correlated with absolute neutrophil count nadir (< 5 x 10(9)/l). AUC showed the best correlation (R2 = 0.72) with absolute neutrophil count nadir by an inhibitory sigmoid Emax model and also correlated with percent decrease in neutrophil count from baseline to nadir by a simple Emax model (R2 = 0.53). Logistic regression analysis indicated that AUC and the duration of exposure over 0.05 to 0.1 microM, but not Cmax, were strong predictors of grade 4 neutropenia (< 0.5 x 10(9)/l). Drug exposure parameters such as AUC derived from population analysis may be used clinically as a useful predictor of drug-induced neutropenia.