The polyamine-biosynthetic pathway represents an inviting target for the development of agents inhibiting carcinogenesis and tumor growth. Polyamines play an essential role in the proliferation and development of mammalian cells. Deranged polyamine metabolism may be an important factor in carcinogenesis. Depletion of polyamines inhibits growth of neoplastic cells in vitro and in animal models. Several different classes of other anticancer agents may under some conditions exert enhanced effects when polyamine levels are depleted. Some suitable inhibitors of polyamine production are currently available and other promising compounds are presently being tested. It should soon prove possible to block polyamine biosynthesis at every step in the pathway. The use of these inhibitors alone and combined either with each other or with other antitumor agents will enable a full examination of the potential of this approach.

https://cancerres.aacrjournals.org/content/canres/48/4/759.full.pdf

Polyamine Metabolism and Its Importance in Neoplastic Growth and as a Target for Chemotherapy

Although no randomized studies have demonstrated a positive impact of therapeutic drug monitoring (TDM) on clinical outcome in epilepsy, evidence from nonrandomized studies and everyday clinical experience does indicate that measuring serum concentrations of old and new generation antiepileptic drugs (AEDs) can have a valuable role in guiding patient management provided that concentrations are measured with a clear indication and are interpreted critically, taking into account the whole clinical context. Situations in which AED measurements are most likely to be of benefit include (1) when a person has attained the desired clinical outcome, to establish an individual therapeutic concentration which can be used at subsequent times to assess potential causes for a change in drug response; (2) as an aid in the diagnosis of clinical toxicity; (3) to assess compliance, particularly in patients with uncontrolled seizures or breakthrough seizures; (4) to guide dosage adjustment in situations associated with increased pharmacokinetic variability (e.g., children, the elderly, patients with associated diseases, drug formulation changes); (5) when a potentially important pharmacokinetic change is anticipated (e.g., in pregnancy, or when an interacting drug is added or removed); (6) to guide dose adjustments for AEDs with dose-dependent pharmacokinetics, particularly phenytoin.

/pdf/antiepileptic-drugs-best-practice-guidelines-for-therapeutic-2fvwrwdstw.pdf

Antiepileptic drugs—best practice guidelines for therapeutic drug monitoring: A position paper by the subcommission on therapeutic drug monitoring, ILAE Commission on Therapeutic Strategies

Trypanosomatids differ from all other organisms in their ability to conjugate the sulfur-containing tripeptide, glutathione, and the polyamine, spermidine, to form trypanothione [N1,N8-bis(glutathionyl)spermidine]. Together with the NADPH-dependent flavoprotein, trypanothione reductase, the dithiol form of trypanothione provides an intracellular reducing environment in these parasites, substituting for glutathione and glutathione reductase found in the mammalian host. Trypanothione and its related enzymes are involved in defense against damage by oxidants, certain heavy metals, and possibly xenobiotics. Trypanothione and its metabolic precursor, glutathionylspermidine, are also implicated in the modulation of spermidine levels during growth. Several existing trypanocidal drugs interact with the trypanothione system, suggesting that trypanothione metabolism may be a good target for the development of new drugs. The purification and properties of three key enzymes (glutathionylspermidine synthetase, trypanothione synthetase, and trypanothione reductase) are discussed, and the catalytic mechanism, substrate-specificity, and the three-dimensional structure of trypanothione reductase are compared to that of glutathione reductase.

Metabolism and functions of trypanothione in the kinetoplastida

Polyamine transport in mammalian cells

Polyamine transport in mammalian cells. an update

16 – Clinical Aspects of Inhibition of Ornithine Decarboxylase with Emphasis on Therapeutic Trials of Eflornithine (DFMO) in Cancer and Protozoan Diseases

MDL 72,222 (1aH, 5aH-tropan-3a-yl 3,5-dichlorobenzoate), a novel agent with antagonist activity at neuronal 5-HT receptors, was tested as an acute treatment for migraine pain under double-blind, placebo-controlled conditions. Forty-seven patients with common (n = 29) or classical (n = 8) migraine or mixed type with or without a psychogenic component (n = 10) received 20–40 mg MDL 72,222 (n = 24) or placebo (n = 23) intravenously during the headache phase of a migraine attack. MDL 72,222 was consistently superior to placebo in rapidly alleviating the migraine pain. The treatment was remarkably well tolerated. The results are consistent with the hypothesis that the pain of migraine is related to activation of neuronal 5-HT receptors and suggest that compounds such as MDL 72,222, which block neuronal 5-HT receptors, could be useful new therapeutic agents for the management of migraine.

Effects on migraine headache of MDL 72,222, an antagonist at neuronal 5-HT receptors. Double-blind, placebo-controlled study.

1. Selective inhibitors of the monoamine oxidase (MAO) isoenzymes, types A and B, are of potential therapeutic utility. Brain selectivity would overcome the risk of tyramine interactions which have been shown to occur with selective MAO-A but not MAO-B inhibitors. 2. (E)-3-Fluoroallylamines of general structure, FHC = C(R)CH2NH2 have been designed as enzyme-activated, irreversible inhibitors of these enzymes. Two compounds, MDL 72145 (R = 3,4 dimethoxyphenyl) and MDL 72974 (R = 4-fluorophenethyl), are selective and irreversible inhibitors of MAO type B which in vivo show high inhibitory potency against the rat brain enzyme (ED50 0.35 and 0.18 mg/kg p.o., respectively). In animals, these inhibitors do not potentiate the cardiovascular effects of tyramine and have no amphetamine-like effects. However, they do potentiate the central effects of L-Dopa and prevent the neurotoxic effects of MPTP in both mice and monkeys. 3. In early clinical studies, MDL 72145 has been shown to be a potent, long-acting inhibitor of MAO type B. Doses of 16 mg per patient totally inhibit platelet enzyme without potentiating the cardiovascular effects of oral tyramine. Compounds of this type should prove useful in Parkinson's disease. 4. Selective inhibition of brain MAO-A can be achieved by using the bioprecursor amino acid MDL 72394 (E-beta-fluoromethylene-m-tyrosine). This amino acid is decarboxylated by aromatic L-amino acid decarboxylase (AADC) to liberate MDL 72392 (R = 3-hydroxyphenyl), a potent irreversible inhibitor of MAO-A. Combination of MDL 72394 with a peripherally selective inhibitor of AADC (e.g., carbidopa) restricts MAO inhibition to the brain. Consequently, under these conditions, there is a greatly reduced propensity to potentiate the cardiovascular effects of tyramine. 5. This has been confirmed in human volunteers; MDL 72394 (8 mg), combined with carbidopa, substantially decreased urinary MHPG and plasma DHPG concentrations with minimal potentiation of the cardiovascular effects of i.v. tyramine. These results predict that such therapy has potential in the treatment of affective disorders.

Paul J. Schechter

Papers

16 – Clinical Aspects of Inhibition of Ornithine Decarboxylase with Emphasis on Therapeutic Trials of Eflornithine (DFMO) in Cancer and Protozoan Diseases

Effects on migraine headache of MDL 72,222, an antagonist at neuronal 5-HT receptors. Double-blind, placebo-controlled study.

Design and early clinical evaluation of selective inhibitors of monoamine oxidase.

Assay of γ-vinyl-γ-aminobutyric acid (4-amino-hex-5-enoic acid) in plasma and urine by automatic amino acid analysis

14 – therapeutic utility of selected enzyme-activated irreversible inhibitors