Yuki Domon

Infantile Pain Episodes Associated with Novel Nav1.9 Mutations in Familial Episodic Pain Syndrome in Japanese Families.

Painful peripheral neuropathy has been correlated with various voltage-gated sodium channel mutations in sensory neurons. Recently Nav1.9, a voltage-gated sodium channel subtype, has been established as a genetic influence for certain peripheral pain syndromes. In this study, we performed a genetic study in six unrelated multigenerational Japanese families with episodic pain syndrome. Affected participants (n = 23) were characterized by infantile recurrent pain episodes with spontaneous mitigation around adolescence. This unique phenotype was inherited in an autosomal-dominant mode. Linkage analysis was performed for two families with 12 affected and nine unaffected members, and a single locus was identified on 3p22 (LOD score 4.32). Exome analysis (n = 14) was performed for affected and unaffected members in these two families and an additional family. Two missense variants were identified: R222H and R222S in SCN11A. Next, we generated a knock-in mouse model harboring one of the mutations (R222S). Behavioral tests (Hargreaves test and cold plate test) using R222S and wild-type C57BL/6 (WT) mice, young (8–9 weeks old; n = 10–12 for each group) and mature (36–38 weeks old; n = 5–6 for each group), showed that R222S mice were significantly (p < 0.05) more hypersensitive to hot and cold stimuli than WT mice. Electrophysiological studies using dorsal root ganglion neurons from 8–9-week-old mice showed no significant difference in resting membrane potential, but input impedance and firing frequency of evoked action potentials were significantly increased in R222S mice compared with WT mice. However, there was no significant difference among Nav1.9 (WT, R222S, and R222H)-overexpressing ND7/23 cell lines. These results suggest that our novel mutation is a gain-of-function mutation that causes infantile familial episodic pain. The mouse model developed here will be useful for drug screening for familial episodic pain syndrome associated with SCN11A mutations.

Role of Angiotensin II Type 1 Receptor on Retinal Vascular Leakage in a Rat Oxygen-Induced Retinopathy Model

Aim: To investigate the role of angiotensin type 1 (AT1) and type 2 (AT2) receptors in hypoxia-induced retinal vascular hyperpermeability. Methods: Brown-Norway rat pups were exposed to hyperoxic conditions from postnatal day 7 (P7) to P12, and to subsequent normal air for 5 days [oxygen-induced retinopathy (OIR) model]. Olmesartan medoxomil (AT1 receptor antagonist; administered orally), PD123319 (AT2 receptor antagonist; administered subcutaneously) or a vehicle was administered once daily during the last 5 days. At P16, the retinal permeability was determined by measuring the leaked fluorescein-conjugated dextran concentration in the retina. The vascular endothelial growth factor (VEGF) and hypoxia-inducible factor 1 (HIF-1) α proteins in the retina were assessed by an ELISA and western blotting, respectively. Results: Olmesartan medoxomil partially, but significantly, inhibited the retinal vascular hyperpermeability induced by hypoxia. In contrast, PD123319 did not show a significant effect. The VEGF and HIF-1α protein levels were significantly elevated in the OIR retina; however, there was no significant effect of olmesartan medoxomil on the expression of either protein. Conclusions: These results suggest that the AT1 receptor is, at least partly, responsible for hyperpermeability in the OIR rat retina via a mechanism independent of HIF-1 and VEGF expression.

Olmesartan medoxomil ameliorates sciatic nerve regeneration in diabetic rats.

To evaluate the effect of angiotensin II type1 receptor blocker on nerve regeneration delay in diabetic rats, nerve regeneration was monitored by a pinch test on the crushed sciatic nerves of streptozotocin-induced diabetic rats. Nerve regeneration was significantly delayed in diabetic rats and was partly ameliorated by treatment with olmesartan medoxomil (3 mg/kg/day, orally). In the ipsilateral dorsal root ganglia, the mRNA level of insulin-like growth factor-1 and ciliary neurotrophic factor (CNTF) was downregulated, whereas the mRNA level of neurotrophin-3 and CNTF receptor was upregulated. Olmesartan medoxomil significantly enhanced the CNTF expression. These results showed that angiotensin II type1 receptor blocker treatment is effective on nerve regeneration delay in diabetic animals and may provide an effective therapy for clinical diabetic neuropathy.

Pharmacological, pharmacokinetics and safety profiles of DS-5565, a novel α2δ ligand

OBJECTIVE: To clarify the characteristics of DS-5565 as a novel α 2 δ ligand , we conducted the experiments using pregabalin (PGB) as a reference. BACKGROUND: DS-5565 is an analgesic drug that binds to the α 2 δ subunit (α 2 δ-1 and α 2 δ-2) of voltage-dependent Ca 2+ channels. The α 2 δ-1 is the main target for the analgesic effect of α 2 δ ligands. The contribution of the α 2 δ-2 to the CNS side effects of α 2 δ ligands still remains to be elucidated. DESIGN/METHODS: The binding affinity and dissociation rate were investigated with rat α 2 δ-1 and α 2 δ-2 transfected cells. The analgesic effect was investigated with von Frey test in streptozotocin (STZ)-induced diabetic rats. The CNS side effects were investigated with rota-rod performance (RR) and locomotor activity (LA) in rats.The plasma drug concentration was measured by LC-MS/MS. RESULTS: The binding affinities of DS-5565 for α 2 δ-1 and α 2 δ-2 were comparable to those of PGB. Interestingly DS-5565 showed a slower dissociation rate from α 2 δ-1 than α 2 δ-2, in particular α 2 δ-1 compared to PGB. DS-5565 showed potent and sustained analgesic effects and the ED 50 was ca 2.5 mg/kg (ED 50 for PGB: 29.3 mg/kg). The plasma concentration of DS-5565 in the STZ rats was about 65-fold less than PGB. DS-5565 inhibited RR (ID 50 : 9.4 mg/kg) and LA (ID 50 : 43.9 mg/kg) and the ratios ID 50 /ED 50 (CNS safety margin) were ca 3.8 in RR and ca 18 in LA. The ratios for PGB were 0.4 and 3.9, respectively. CONCLUSIONS: DS-5565 has superior analgesic effects with a wider CNS safety margin relative to PGB. These profiles of DS-5565 are possibly due to its unique binding characteristics to α 2 δ-1 and α 2 δ-2. Disclosure: Dr. Yokoyama has received personal compensation for activities with Daiichi Pharmaceutical Corp. as an employee. Dr. Arakawa has received personal compensation for activities with Daiichi Pharmaceutical Corporation as an employee. Dr. Domon has received personal compensation for activities with Daiichi Pharmaceutical Corp. as an employee. Dr. Matsuda has received personal compensation for activities with Daiichi Pharmaceutical Corp. Dr. Inoue has received personal compensation for activities with Daiichi Pharmaceutical Corp. as an employee. Dr. Kitano has received personal compensation for activities with Daiichi Pharmaceutical Corp. Dr. Takahashi has received personal compensation for activities with Daiichi Pharmaceutical Corp. as an employee. Dr. Yamamura has received personal compensation for activities with Daiichi Sankyo. Dr. has received personal compensation for activities with Daiichi Pharmaceutical Corp. as an employee.

Pharmacokinetics of DS-5565, a novel α2δ ligand, in rats and monkeys and assessment of DDI risk

OBJECTIVE: We elucidated the pharmacokinetic profiles of DS-5565 in animals and drug interaction risk as perpetrator. BACKGROUND: DS-5565 is an oral analgesic drug that binds to the α 2 δ subunit of voltage-dependent Ca 2+ channels. DESIGN/METHODS: DS-5565 is the salt and the free form of DS-5565 is active moiety. Plasma concentration of the active moiety was determined by validated LC-MS/MS method. The profiles were investigated in F344 rats, streptozotocin-induced diabetic BN rats as neuropathic pain model, and cynomolgus monkeys. Distribution was assessed by whole body autoradioluminography following an oral administration of 14 C-labeled active moiety in F344 rats. Induction potential for CYP1A2 and CYP3A4 was assessed using fresh human hepatocytes. Inhibition potential for various CYP isoforms and drug transporters was tested using human liver microsomes and transporter overexpressing cells, respectively. RESULTS: The plasma exposure increased proportionally with the investigated dose in both strain and species. The bioavailability was higher than 85% in both species. The radioactivity was detected in almost tissues at 30 min but was primarily detectable in limited organs at 24 h post-dose. The plasma protein binding in rats, monkeys and humans in vitro was low. A few metabolites, which have not pharmacological activity, were detected qualitatively at low levels in plasma in both after oral administration. The primary excretion route of the radioactivity was urine; 蠅 87% of the dose was recovered within 7 days after an oral administration of the 14 C-labeled compound in rats and monkeys. Renal clearance of DS-5565 was higher than GFR in both animals, suggesting active secretion in the kidney. DS-5565 did not induce CYP1A2/3A4 in human hepatocytes, and not inhibit various CYP isoforms in human liver microsomes and drug transporters in overexpressing cells. CONCLUSIONS: Pharmacokinetics of DS-5565 in animals was favorable. DS-5565 has low potential to be perpetrator in drug-drug interaction. Disclosure: Dr. Yamamura has received personal compensation for activities with Daiichi Sankyo. Dr. Yamada has received personal compensation for activities with Daiichi Sankyo. Dr. Takahashi has received personal compensation for activities with Daiichi Pharmaceutical Corp. as an employee. Dr. Uchiyama has received personal compensation for activities with Daiichi Phamaceutical Corp. Dr. Koda has received personal compensation for activities with Daiichi Pharmaceutical Corp. Dr. Mikkaichi has received personal compensation for activities with Daiichi Pharmaceutical Corp. Dr. Nishiya has received personal compensation for activities with Daiichi Pharmaceutical Corp. as an employee. Dr. Honda has received personal compensation for activities with Daiichi Pharmaceutical Corp. Dr. Arakawa has received personal compensation for activities with Daiichi Pharmaceutical Corporation as an employee. Dr. Domon has received personal compensation for activities with Daiichi Pharmaceutical Corp. as an employee. Dr. Fischer has received personal compensation for activities with Daiichi Pharmaceutical Corp. as an employee. Dr. Mueller has received personal compensation for activities with Daiichi Pharmaceutical Corp.

Binding Characteristics and Analgesic Effects of Mirogabalin, a Novel Ligand for the α2δ Subunit of Voltage-Gated Calcium Channels

Mirogabalin ([(1R,5S,6S)-6-(aminomethyl)-3-ethylbicyclo[3.2.0]hept-3-en-6-yl]acetic acid), a novel ligand for the α2δ subunit of voltage-gated calcium channels, is being developed to treat pain associated with diabetic peripheral neuropathy and postherpetic neuralgia. In the present study, we investigated the in vitro binding characteristics and in vivo analgesic effects of mirogabalin compared with those of pregabalin, a standard α2δ ligand. Mirogabalin showed potent and selective binding affinities for the α2δ subunits, while having no effects on 186 off-target proteins. Similar to pregabalin, mirogabalin did not show clear subtype selectivity (α2δ-1 vs. α2δ-2) or species differences (human vs. rat). However, in contrast to pregabalin, mirogabalin showed greater binding affinities for human α2δ-1, human α2δ-2, rat α2δ-1, and rat α2δ-2 subunits; further, it had a slower dissociation rate for the α2δ-1 subunit than the α2δ-2 subunit. Additionally, in experimental neuropathic pain models, partial sciatic nerve ligation rats and streptozotocin-induced diabetic rats, mirogabalin showed more potent and longer lasting analgesic effects. In safety pharmacological evaluations, mirogabalin and pregabalin inhibited rota-rod performance and locomotor activity in rats; however, the safety indices of mirogabalin were superior to those of pregabalin. In conclusion, mirogabalin shows potent and selective binding affinities for the human and rat α2δ subunits, and slower dissociation rates for the α2δ-1 subunit than the α2δ-2 subunit. It shows potent and long-lasting analgesic effects in rat models of neuropathic pain, and wider safety margins for side effects of the central nervous system. These properties of mirogabalin can be associated with its unique binding characteristics.

Discovery of (phenoxy-2-hydroxypropyl)piperidines as a novel class of voltage-gated sodium channel 1.7 inhibitors

A novel class of NaV1.7 inhibitors has been identified by high-throughput screening followed by structure activity relationship studies. Among this series of compounds, piperidine 9o showed potent human and mouse NaV1.7 inhibitory activities with fair subtype selectivity over NaV1.5. Compound 9o successfully demonstrated analgesic efficacy in mice comparable to that of the currently used drug, mexiletine, but with an expanded central nervous system safety margin.

Alkylsulfanyl analogs as potent α 2 δ ligands

We identified novel (3R, 5S)-3-aminomethyl-5-methanesulfanyl hexanoic acid (5a: DS75091588) and (3R, 5S)-3-aminomethyl-5-ethanesulfanyl hexanoic acid (6a: DS18430756) as sulfur-containing γ-amino acid derivatives that were useful for the treatment of neuropathic pain. These two compounds exhibited a potent analgesic effect in animal models of both type I diabetes and type II diabetes, and good pharmacokinetics.

Contents Vol. 41, 2009

Anatomy, Pathology and Cell Biology A. Prescott, Dundee Biochemistry, Molecular Biology and Molecular Genetics J. Graw, Neuherberg Clinical and Epidemiological Research M. Kojima, Kahoku Clinical Retina P. Wiedemann, Leipzig Cornea and Ocular Surface C. Marfurt, Gary, Ind. Glaucoma C. Erb, Berlin Immunology and Microbiology U. Pleyer, Berlin Lens and Cataract S. Varma, Baltimore, Md. Miscellaneous U. Pleyer, Berlin Neuro-Ophthalmology and Vision Sciences P. Aydin, Ankara Ocular Oncology M. Jager, Leiden Physiology, Pharmacology and Toxicology A. Wegener, Bonn Retina and Retinal Cell Biology M. Boulton, Gainesville, Fla. P. Wiedemann, Leipzig Editorial Board