The antifolates.

Department of Medicine and the Albert Einstein Cancer Center, The Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
Hematology/oncology clinics of North America (Impact Factor: 2.07). 06/2012; 26(3):629-48, ix. DOI: 10.1016/j.hoc.2012.02.002
Source: PubMed

ABSTRACT This article focuses on the cellular, biochemical, and molecular pharmacology of antifolates and how a basic understanding of the mechanism of action of methotrexate, its cytotoxic determinants, mechanisms of resistance, and transport into and out of cells has led to the development of a new generation of antifolates, a process that continues in the laboratory and in the clinics. New approaches to folate-based cancer chemotherapy are described based on the targeted delivery of drugs to malignant cells.

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    ABSTRACT: Structure-activity relationships for cellular uptake and inhibition of cell proliferation were studied for 2-amino-4-oxo-6-substituted pyrrolo[2,3-d]pyrimidine thienoyl antifolates in which the terminal l-glutamate of the parent structure (7) was replaced by natural or unnatural amino acids. Compounds 7 and 10-13 were selectively inhibitory toward folate receptor (FR) α-expressing Chinese hamster ovary (CHO) cells. Antiproliferative effects of compounds 7 and 9-13 toward FRα- and FRβ-expressing CHO cells were only partly reflected in binding affinities to FRα and FRβ or in the docking scores with molecular models of FRα and FRβ. Compounds 7 and 11 were potent inhibitors of glycinamide ribonucleotide formyltransferase in de novo purine biosynthesis in KB human tumor cells. These studies establish for the first time the importance of the α- and γ-carboxylic acid groups, the length of the amino acid, and the conformation of the side chain for transporter binding and biological activity of 6-substituted pyrrolo[2,3-d]pyrimidine thienoyl antifolates.
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    ABSTRACT: Abstract In the present study, we report the structure of the free and drug-bound Fab fragment of a high affinity anti-methotrexate antibody and perform a thermodynamic analysis of the binding process. The anti-methotrexate Fab fragment features a remarkably rigid tunnel-like binding site that extends into a water channel serving as the specialized route to move solvent out and into the site upon ligand binding and dissociation. This new finding in antibody structure-function relationships directly relates to the fast association (1107 M-1s-1) and slow (410-5 s-1) dissociation rates determined for mAb ADD056, resulting in a very strong binding with a KD ~ 3.6 pM at 20°C. As follows from the X-ray data analysis, the methotrexate-antibody complex is stabilized by an extended network of hydrogen bonds and stacking interactions. The analysis also shows structural involvement of the CDR H3 in formation of the water channel revealing another important role of this hypervariable region, which suggests a new direction in natural affinity maturation and opens a new possibility in antibody engineering. Methotrexate is a widely used therapeutic agent for many malignant diseases and inflammatory disorders. Unfortunately, it may also interfere with central aspects of metabolism and thereby cause inevitable side effects. Therefore, methotrexate therapy requires careful monitoring of drug blood levels, which is traditionally done by immunoassays. An understanding of the structure-function properties of antibodies selected for drug monitoring substantiates the performance and robustness of such tests.
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    ABSTRACT: The liver is one of the most commonly involved extrapulmonary sites in sarcoidosis. Hepatic sarcoidosis has a broad range of presentations from scattered, asymptomatic noncaseating granulomas with normal liver enzymes, which are very common in patients with known pulmonary sarcoidosis, to portal hypertension and cirrhosis, which are relatively uncommon. Diagnosis is based on a combination of clinical, laboratory and histological manifestations. The authors' protocol for management of patients with suspected sarcoidosis of the liver without focal lesions includes a transjugular liver biopsy with portal pressure measurements to confirm the diagnosis, rule out coexisting liver diseases and to identify select patients with fibrosis or portal hypertension for consideration of immunosuppression. Steroids and azathioprine are the preferred agents and methotrexate is not recommended.
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