Novel Insights for Inhibiting Mutant Heterodimer IDH1wt-R132H in Cancer: An In-Silico Approach.

BACKGROUND: Isocitrate dehydrogenase 1 (IDH1) is a dimeric enzyme responsible for supplying the cell's nicotinamide adenine dinucleotide phosphate (NADPH) reserves via dehydrogenation of isocitrate (ICT) and reduction of NADP+. Mutations in position R132 trigger cancer by enabling IDH1 to produce D-2-hydroxyglutarate (2-HG) and reduce inhibition by ICT. Mutant IDH1 can be found as a homodimer or a heterodimer. OBJECTIVE: We propose a novel strategy to inhibit IDH1 R132 variants as a means not to decrease the concentration of 2-HG but to provoke a cytotoxic effect, as the cell malignancy at this point no longer depends on 2-HG. We aim to inhibit the activity of the mutant heterodimer to block the wild-type subunit. Limiting the NADPH reserves in a cancerous cell will enhance its susceptibility to the oxidative stress provoked by chemotherapy. METHODS: We performed a virtual screening using all US FDA-approved drugs to replicate the loss of inhibition of mutant IDH1 by ICT. We characterized our results based on molecular interactions and correlated them with the described phenotypes. RESULTS: We replicated the loss of inhibition by ICT in mutant IDH1. We identified 20 drugs with the potential to inhibit the heterodimeric isoform. Six of them are used in cancer treatment. CONCLUSIONS: We present 20 FDA-approved drugs with the potential to inhibit IDH1 wild-type activity in mutated cells. We believe this work may provide important insights into current and new approaches to dealing with IDH1 mutations. In addition, it may be used as a basis for additional studies centered on drugs presenting differential sensitivities to different IDH1 isoforms.

Dihydroergotamine mesylate-loaded dissolving microneedle patch made of polyvinylpyrrolidone for management of acute migraine therapy.

Migraine is a widespread neurological disease with negative effects on quality of life and productivity. Moderate to severe acute migraine attacks can be treated with dihydroergotamine mesylate (DHE), an ergot derivative that is especially effective in non-responders to triptan derivatives. To overcome limitations of current DHE formulations in subcutaneous injection and nasal spray such as pain, adverse side effects and poor bioavailability, a new approach is needed for DHE delivery enabling painless self-administration, quick onset of action, and high bioavailability. In this study, we developed a dissolving microneedle patch (MNP) made of polyvinylpyrrolidone, due to its high aqueous solubility and solubility enhancement properties, using a MNP design previously shown to be painless and simple to administer. DHE-loaded MNPs were shown to have a content uniformity of 108±9% with sufficient mechanical strength for insertion to pig skin ex vivo and dissolution within 2min. In vivo pharmacokinetic studies were carried out on hairless rats, and DHE plasma levels were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The area under curve (AUC) value after DHE delivery by MNP (1259±917ng/mL min) was not significantly different (p>0.05) as compared to subcutaneous injection, with a relative bioavailability of 97%. Also, appreciable plasma levels of DHE were seen within 5min for both delivery methods and tmax value of MNPs (38±23min) showed no significant difference (p>0.05) compared to subcutaneous injection (24±13min). These results suggest that DHE-loaded MNPs have promise as an alternative DHE delivery method that can be painlessly self-administered with rapid onset and high bioavailability.

Cyclolization of D-lysergic acid alkaloid peptides.

The tripeptide chains of the ergopeptines, a class of pharmacologically important D-lysergic acid alkaloid peptides, are arranged in a unique bicyclic cyclol based on an amino-terminal α-hydroxyamino acid and a terminal orthostructure. D-lysergyl-tripeptides are assembled by the nonribosomal peptide synthetases LPS1 and LPS2 of the ergot fungus Claviceps purpurea and released as N-(D-lysergyl-aminoacyl)-lactams. We show total enzymatic synthesis of ergopeptines catalyzed by a Fe²âº/2-ketoglutarate-dependent dioxygenase (EasH) in conjunction with LPS1/LPS2. Analysis of the reaction indicated that EasH introduces a hydroxyl group into N-(D-lysergyl-aminoacyl)-lactam at α-C of the aminoacyl residue followed by spontaneous condensation with the terminal lactam carbonyl group. Sequence analysis revealed that EasH belongs to the wide and diverse family of the phytanoyl coenzyme A hydroxylases. We provide a high-resolution crystal structure of EasH that is most similar to that of phytanoyl coenzyme A hydroxylase, PhyH, from human.

Structural basis for molecular recognition at serotonin receptors.

Serotonin or 5-hydroxytryptamine (5-HT) regulates a wide spectrum of human physiology through the 5-HT receptor family. We report the crystal structures of the human 5-HT1B G protein-coupled receptor bound to the agonist antimigraine medications ergotamine and dihydroergotamine. The structures reveal similar binding modes for these ligands, which occupy the orthosteric pocket and an extended binding pocket close to the extracellular loops. The orthosteric pocket is formed by residues conserved in the 5-HT receptor family, clarifying the family-wide agonist activity of 5-HT. Compared with the structure of the 5-HT2B receptor, the 5-HT1B receptor displays a 3 angstrom outward shift at the extracellular end of helix V, resulting in a more open extended pocket that explains subtype selectivity. Together with docking and mutagenesis studies, these structures provide a comprehensive structural basis for understanding receptor-ligand interactions and designing subtype-selective serotonergic drugs.

Dihydroergotamine, ergotamine, methysergide and sumatriptan - basic science in relation to migraine treatment.

The 5-hydroxytryptamine (5-HT) receptor family mediates the effects of several drugs highly effective in migraine primarily by activating 5-HT(1B) , 5-HT(1D) , and 5-HT(1F) receptors. Ergotamine, dihydroergotamine, and methysergide, as well as the "triptan" sumatriptan, are all agonists for these receptors. The receptor profile and degree of selectivity of these four drugs differ, which is reflected by their side effects that limit their use in the acute and prophylactic treatment of migraine. The acute antimigraine efficacy of these remedies is very much dependent on the formulation used where, in general, parenteral formulations are more effective in reliving the symptoms of a migraine attack.

Pharmacology of dihydroergotamine and evidence for efficacy and safety in migraine.

Dihydroergotamine mesylate (DHE), an ergot alkaloid, has been extensively utilized and studied in the treatment of episodic and chronic migraine. This article reviews the pharmacokinetics, pharmacodynamics, and clinical efficacy and safety of DHE, particularly in comparison to ergotamine tartrate (ET), a similar ergot alkaloid with a long history of use in the treatment of migraine. Structural differences between these 2 compounds account for clinically important distinctions in their pharmacokinetic, pharmacodynamic, and adverse event profiles. DHE is a significantly less potent arterioconstrictor than is ET, which makes it a potentially much safer drug. In addition, DHE is associated with a markedly lower incidence of medication-withdrawal headache, nausea, and vomiting than is ET. The safety and efficacy data presented here are derived from clinical trials and case series involving DHE administered by intravenous infusion, intramuscular or subcutaneous injection, or intranasal spray.

Continuous intravenous dihydroergotamine in the treatment of intractable headache.

We reviewed data on 171 patients with refractory headache treated by continuous intravenous dihydroergotamine mesylate (i.v. DHE 45) and repetitive i.v. DHE and compared the efficacy of continuous i.v. DHE to repetitive i.v. DHE. One hundred (58.5%) patients had refractory chronic daily headache. Seventy-one (42%) had drug rebound headache. One hundred thirty-eight (81%) had refractory migraine without aura, and 28 (16%) had migraine with aura. Treatment consisted of either continuous i.v. DHE by infusion pump or repetitive i.v. DHE and withdrawal of excessively used analgesics, analgesic narcotics, ergotamines, or benzodiazepines. Eighty-nine (92.5%) patients treated with continuous i.v. DHE became headache-free; the majority, 62 (64.5%), within 3 days. Sixty-five (86.5%) patients treated by repetitive i.v. DHE became headache-free, 50 (66.5%) within three days. The average hospital stay for both treatment groups was 4 days. Twelve (12.5%) of the continuous group and 12 (16%) of the repetitive group were headache-free within 24 hours. The average length of time to become headache-free was similar for the two groups, 3.06 days for continuous i.v. DHE and 2.94 days for repetitive i.v. DHE. The most common side effect was nausea, followed by diarrhea, vomiting, and leg cramps. We conclude that DHE can be accurately and easily administered by continuous i.v. infusion pump, and that continuous i.v. DHE is a safe and efficacious mode of treatment producing results similar to repetitive i.v. DHE.

The pharmacology of ergotamine and dihydroergotamine.

The ergot alkaloids are a family of chemical entities that have many pharmacologic effects. Their diversity results from their interaction with multiple receptors, their variable receptor affinity and intrinsic activity, and their variable organ-specific receptor access. Ergotamine tartrate (ET) was one of the first ergot alkaloids to be isolated. Dihydroergotamine (DHE) is synthesized by reducing an unsaturated bond in ergotamine (E); this modification results in a changed pharmacologic profile. Dihydroergotamine exhibits greater alpha-adrenergic antagonist activity and much less potent arterial vasoconstriction and emetic potential. Both E and DHE are 5-HT1A, 5-HT1B, 5-HT1D, and 5-HT1F receptor agonists. The vasoconstrictor activities of these ergot compounds have long been believed to be the basis of their clinical effects, but recent evidence suggests that their antimigraine action may result in part from their inhibitory effects on neurogenic inflammation and neuronal transmission and not from vasoconstriction. Improvements in assay methodology have provided more accurate determination of the pharmacokinetics of E and DHE. The long duration of action appears to result from active metabolites and tight tissue binding. Intranasal (IN) administration of DHE delivers adequate plasma concentrations of the drug without the need for parenteral administration and should further expand its role in migraine pharmacotherapy.