Pharmacological Profile of MP-101, a Novel Non-racemic Mixture of R- and S-dimiracetam with Increased Potency in Rat Models of Cognition, Depression and Neuropathic Pain.

The racemic mixture dimiracetam negatively modulates NMDA-induced glutamate release in rat spinal cord synaptosomal preparations and is orally effective in models of neuropathic pain. In this study, we compared the effects of dimiracetam, its R- or S-enantiomers, and the R:S 3:1 non-racemic mixture (MP-101). In vitro, dimiracetam was more potent than its R- or S-enantiomers in reducing the NMDA-induced [3H]D-aspartate release in rat spinal cord synaptosomes. Similarly, acute oral administration of dimiracetam was more effective than a single enantiomer in the sodium monoiodoacetate (MIA) paradigm of painful osteoarthritis. Then, we compared the in vitro effects of a broad range of non-racemic enantiomeric mixtures on the NMDA-induced [3H]D-aspartate release. Dimiracetam was a more potent blocker than each isolated enantiomer but the R:S 3:1 non-racemic mixture (MP-101) was even more potent than dimiracetam, with an IC50 in the picomolar range. In the chronic oxaliplatin-induced neuropathic pain model, MP-101 showed a significantly improved anti-neuropathic profile, and its effect continued one week after treatment suspension. MP-101 also performed better than dimiracetam in animal models of cognition and depression. Based on the benign safety and tolerability profile previously observed with racemic dimiracetam, MP-101 appears to be a novel, promising clinical candidate for the prevention and treatment of several neuropathic and neurological disorders.

A rat model of FOLFOX-induced neuropathy: effects of oral dimiracetam in comparison with duloxetine and pregabalin.

BACKGROUND AND AIM: The FOLFOX family of chemotherapy regimens are hampered by the development of a painful neuropathy. Current clinical treatments are inadequate, and furthermore, the research of innovative drugs is strongly disadvantaged by the absence of a preclinical model based on the complete mixture of FOLFOX components. The aim of this study was to set up a rat model of FOLFOX-induced neuropathy in rats, validate its predictability by reference drugs, and evaluate the effectiveness of the new anti-neuropathic compound dimiracetam. METHODS: Male Sprague-Dawley rats were treated intraperitoneally with the FOLFOX components (6 mg kg-1 oxaliplatin, 50 mg kg-1 5-FU, 90 mg kg-1 leucovorin calcium salt) or oxaliplatin alone (6 mg kg-1) on days 0, 7, 14, and 21, whereas a separate group received one more injection of FOLFOX on day 28. Pain behavioural measurements (paw pressure, cold plate, and electronic Von Frey tests) and motor coordination (Rota-rod test) were assessed before and after treatments. Behavioural, motor, neurological, and autonomic parameters (open field and Irwin tests) were evaluated. RESULTS: FOLFOX reduced the pain threshold in response to mechanical noxious and thermal (cold) non-noxious stimuli beginning from day 14 up to day 42 comparably to oxaliplatin alone. A fifth FOLFOX injection enhanced the severity but not the duration of painful alterations. Spontaneous activity, behavioural, autonomic, and neurological functions were also affected, whereas the motor coordination was not altered. On day 22, duloxetine (15 mg kg-1, per os), morphine (10 mg kg-1, subcutaneously), or pregabalin (20 mg kg-1, per os), acutely administered, reduced the FOLFOX-dependent hypersensitivity. Repeated treatments with dimiracetam (150 mg kg-1, per os, twice daily, from day 22) significantly protected rats from FOLFOX-induced alterations of pain threshold as well as from autonomic and neurological impairments taking effect after 7 days treatment. Pregabalin repeatedly administered (20 mg kg-1, per os, twice daily, from day 22) was less effective in reducing mechanical hypersensitivity. CONCLUSION: A clinically consistent model of FOLFOX-induced neurotoxicity has been developed in rats. Dimiracetam fully reduced hypersensitivity and neurological alterations showing a relevant profile as anti-neuropathic resource.

A model of neuropathic pain induced by sorafenib in the rat: Effect of dimiracetam.

BACKGROUND: Sorafenib is a kinase inhibitor anticancer drug whose repeated administration causes the onset of a peripheral painful neuropathy. Notably, the efficacy of common analgesic drugs is not adequate and this often leads pre-mature discontinuation of anticancer therapy. The aim of this study was to establish a rat model of sorafenib-induced neuropathic pain, and to assess the effect of the new anti-neuropathic compound dimiracetam in comparison with gabapentin, pregabalin and duloxetine. METHODS: Male Sprague-Dawley rats were treated i.v. (10 mg kg(-1)), i.p. (10 and 30 mg kg(-1)) or p.o. (80 and 160 mg kg(-1)) with sorafenib once daily for 21 days. Pain behaviour measurements (cold plate, paw pressure, electronic von Frey) were performed on days 0, 7, 14 and 21. RESULTS: Sorafenib lowered the paw-licking threshold to non-noxious cold stimuli on day 14 of all protocols evaluated. The i.p. administration resulted in greater efficacy than the other administration routes. Sorafenib treatments did not affect paw-withdrawal responses to non-noxious or to noxious mechanical stimuli. On day 14, dimiracetam (300 mg kg(-1)), gabapentin (100 mg kg(-1)), pregabalin (30 mg kg(-1)) and duloxetine (30 mg kg(-1)) were acutely administered p.o. in sorafenib i.p.-treated rats. A single oral dose of dimiracetam induced a statistically significant increase of the pain threshold 15 min after administration. Pregabalin induced a comparable effect, whereas gabapentin and duloxetine were ineffective. Repeated twice-daily administration of dimiracetam (150 mg kg(-1) p.o.), starting on the first day of i.p sorafenib administration, significantly protected rats from sorafenib-induced decrease in the paw-licking threshold. CONCLUSIONS: A rat model of sorafenib-induced hypersensitivity to cold stimulation has been established. Dimiracetam and pregabalin are effective in prevention of sorafenib-induced neuropathy in this model.

Three different up-titration regimens of ponesimod, an S1P1 receptor modulator, in healthy subjects.

Ponesimod is a selective S1P1 receptor modulator, and induces dose-dependent reduction of circulating lymphocytes upon oral dosing. Previous studies showed that single doses up to 75 mg or multiple doses up to 40 mg once daily are well tolerated, and heart rate (HR) reduction and atrio-ventricular conduction delays upon treatment initiation are reduced by gradual up-titration to the maintenance dose. This single-center, open-label, randomized, multiple-dose, 3-treatment, 3-way crossover study compared the tolerability, safety, pharmacokinetics, cardiodynamics, and effects on lymphocytes of 3 different up-titration regimens of ponesimod in healthy male and female subjects. Up-titration regimens comprised escalating periods of b.i.d. dosing (2.5 or 5 mg) and q.d. dosing (10 or 20 mg or both). After the third up-titration period a variable-duration washout period of 1-3 days was followed by re-challenge with a single 20-mg dose of ponesimod. Adverse events were transient and mild to moderate in intensity, not different between regimens. HR decrease after the first dose was greater than after all subsequent doses, including up-titration doses. Little or no HR change was observed with morning doses of b.i.d. regimens, suggesting that 2.5 and 5 mg b.i.d. are sufficient to sustain cardiac desensitization for the 12-hours dosing interval.

Novel S1P(1) receptor agonists--part 3: from thiophenes to pyridines.

In preceding communications we summarized our medicinal chemistry efforts leading to the identification of potent, selective, and orally active S1P1 agonists such as the thiophene derivative 1. As a continuation of these efforts, we replaced the thiophene in 1 by a 2-, 3-, or 4-pyridine and obtained less lipophilic, potent, and selective S1P1 agonists (e.g., 2) efficiently reducing blood lymphocyte count in the rat. Structural features influencing the compounds' receptor affinity profile and pharmacokinetics are discussed. In addition, the ability to penetrate brain tissue has been studied for several compounds. As a typical example for these pyridine based S1P1 agonists, compound 53 showed EC50 values of 0.6 and 352 nM for the S1P1 and S1P3 receptor, respectively, displayed favorable PK properties, and penetrated well into brain tissue. In the rat, compound 53 maximally reduced the blood lymphocyte count for at least 24 h after oral dosing of 3 mg/kg.

Novel S1P(1) receptor agonists--part 2: from bicyclo[3.1.0]hexane-fused thiophenes to isobutyl substituted thiophenes.

Previously, we reported on the discovery of a novel series of bicyclo[3.1.0]hexane fused thiophene derivatives that serve as potent and selective S1P1 receptor agonists. Here, we discuss our efforts to simplify the bicyclohexane fused thiophene head. In a first step the bicyclohexane moiety could be replaced by a simpler, less rigid cyclohexane ring without compromising the S1P receptor affinity profile of these novel compounds. In a second step, the thiophene head was simplified even further by replacing the cyclohexane ring with an isobutyl group attached either to position 4 or position 5 of the thiophene. These structurally much simpler headgroups again furnished potent and selective S1P1 agonists (e.g., 87), which efficiently and dose dependently reduced the number of circulating lymphocytes upon oral administration to male Wistar rats. For several compounds discussed in this report lymphatic transport is an important route of absorption that may offer opportunities for a tissue targeted approach with minimal plasma exposure.

Novel S1P1 receptor agonists--part 1: From pyrazoles to thiophenes.

From a high-throughput screening campaign aiming at the identification of novel S1P1 receptor agonists, the pyrazole derivative 2 emerged as a hit structure. Medicinal chemistry efforts focused not only on improving the potency of the compound but in particular also on resolving its inherent instability issue. This led to the discovery of novel bicyclo[3.1.0]hexane fused thiophene derivatives. Compounds with high affinity and selectivity for S1P1 efficiently reducing the blood lymphocyte count in the rat were identified. For instance, compound 85 showed EC50 values of 7 and 2880 nM on S1P1 and S1P3, respectively, had favorable pharmacokinetic properties in rat and dog, distributed well into brain tissue, and efficiently and dose dependently reduced the blood lymphocyte count in the rat. After oral administration to spontaneously hypertensive rats, the S1P1 selective compound 85 showed no effect on mean arterial blood pressure and affected the heart rate during the wake phase of the animals only.

2-imino-thiazolidin-4-one derivatives as potent, orally active S1P1 receptor agonists.

Sphingosine-1-phosphate (S1P) is a widespread lysophospholipid which displays a wealth of biological effects. Extracellular S1P conveys its activity through five specific G-protein coupled receptors numbered S1P(1) through S1P(5). Agonists of the S1P(1) receptor block the egress of T-lymphocytes from thymus and lymphoid organs and hold promise for the oral treatment of autoimmune disorders. Here, we report on the discovery and detailed structure-activity relationships of a novel class of S1P(1) receptor agonists based on the 2-imino-thiazolidin-4-one scaffold. Compound 8bo (ACT-128800) emerged from this series and is a potent, selective, and orally active S1P(1) receptor agonist selected for clinical development. In the rat, maximal reduction of circulating lymphocytes was reached at a dose of 3 mg/kg. The duration of lymphocyte sequestration was dose dependent. At a dose of 100 mg/kg, the effect on lymphocyte counts was fully reversible within less than 36 h. Pharmacokinetic investigation of 8bo in beagle dogs suggests that the compound is suitable for once daily dosing in humans.

Promotion of sleep by targeting the orexin system in rats, dogs and humans.

Orexins are hypothalamic peptides that play an important role in maintaining wakefulness in mammals. Permanent deficit in orexinergic function is a pathophysiological hallmark of rodent, canine and human narcolepsy. Here we report that in rats, dogs and humans, somnolence is induced by pharmacological blockade of both orexin OX(1) and OX(2) receptors. When administered orally during the active period of the circadian cycle, a dual antagonist increased, in rats, electrophysiological indices of both non-REM and, particularly, REM sleep, in contrast to GABA(A) receptor modulators; in dogs, it caused somnolence and increased surrogate markers of REM sleep; and in humans, it caused subjective and objective electrophysiological signs of sleep. No signs of cataplexy were observed, in contrast to the rodent, dog or human narcolepsy syndromes. These results open new perspectives for investigating the role of endogenous orexins in sleep-wake regulation.

Pharmacology of the urotensin-II receptor antagonist palosuran (ACT-058362; 1-[2-(4-benzyl-4-hydroxy-piperidin-1-yl)-ethyl]-3-(2-methyl-quinolin-4-yl)-urea sulfate salt): first demonstration of a pathophysiological role of the urotensin System.

Urotensin-II (U-II) is a cyclic peptide now described as the most potent vasoconstrictor known. U-II binds to a specific G protein-coupled receptor, formerly the orphan receptor GPR14, now renamed urotensin receptor (UT receptor), and present in mammalian species. Palosuran (ACT-058362; 1-[2-(4-benzyl-4-hydroxy-piperidin-1-yl)-ethyl]-3-(2-methyl-quinolin-4-yl)-urea sulfate salt) is a new potent and specific antagonist of the human UT receptor. ACT-058362 antagonizes the specific binding of (125)I-labeled U-II on natural and recombinant cells carrying the human UT receptor with a high affinity in the low nanomolar range and a competitive mode of antagonism, revealed only with prolonged incubation times. ACT-058362 also inhibits U-II-induced calcium mobilization and mitogen-activated protein kinase phosphorylation. The binding inhibitory potency of ACT-058362 is more than 100-fold less on the rat than on the human UT receptor, which is reflected in a pD'(2) value of 5.2 for inhibiting contraction of isolated rat aortic rings induced by U-II. In functional assays of short incubation times, ACT-058362 behaves as an apparent noncompetitive inhibitor. In vivo, intravenous ACT-058362 prevents the no-reflow phenomenon, which follows renal artery clamping in rats, without decreasing blood pressure and prevents the subsequent development of acute renal failure and the histological consequences of ischemia. In conclusion, the in vivo efficacy of the specific UT receptor antagonist ACT-058362 reveals a role of endogenous U-II in renal ischemia. As a selective renal vasodilator, ACT-058362 may be effective in other renal diseases.

Urotensin II mediates ERK1/2 phosphorylation and proliferation in GPR14-transfected cell lines.

Urotensin-II (U-II), a vasoactive cyclic neuropeptide, was recently identified as the natural ligand for the G-protein coupled receptor GPR14. The expression pattern of U-II and GPR14 are consistent with a role as a neurohormonal regulatory system in cardiovascular homeostasis. Urotensin-II induces a rapid and short-lasting rise in intracellular calcium in recombinant GPR14 expressing cells. In the present study we show that U-II induces signal transduction pathways leading to the long-lasting activation of extracellular signal-regulated kinase 1/2 (ERK1/2) in chinese hamster ovary cells expressing human GPR14 (CHO-GPR14). Furthermore, we observed a growth-stimulating and PD98059 sensitive activity of U-II in CHO-GPR14 cells, but not CHO-K1 cells. The investigation of the GPR14 induced signal transduction pathways leading to ERKI/2 phosphorylation revealed a previously unsuspected role for G(i/o)-protein coupling and showed an involvement of phospatidylinositol-3-kinase, phospholipase C and calcium channel mediated mechanisms. Our results suggest that U-II and its receptor GPR14 may be involved in long-lasting physiological effects such as cardiovascular remodeling.