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Since the SARS-CoV-2 pandemic started in late 2019, the search for protective vaccines and for drug treatments has become mandatory to fight the global health emergency. Travel restrictions, social distancing, and face masks are suitable counter measures, but may not bring the pandemic under control because people will inadvertently or at a certain degree of restriction severity or duration become incompliant with the regulations. Even if vaccines are approved, the need for antiviral agents against SARS-CoV-2 will persist. However, unequivocal evidence for efficacy against SARS-CoV-2 has not been demonstrated for any of the repurposed antiviral drugs so far. Amantadine was approved as an antiviral drug against influenza A, and antiviral activity against SARS-CoV-2 has been reasoned by analogy but without data. We tested the efficacy of amantadine in vitro in Vero E6 cells infected with SARS-CoV-2. Indeed, amantadine inhibited SARS-CoV-2 replication in two separate experiments with IC50 concentrations between 83 and 119 µM. Although these IC50 concentrations are above therapeutic amantadine levels after systemic administration, topical administration by inhalation or intranasal instillation may result in sufficient amantadine concentration in the airway epithelium without high systemic exposure. However, further studies in other models are needed to prove this hypothesis.

Wojciech Danysz,1 Bartosch Nowag,1 Thomas Hengl,1 Peter Kreymerman,2 Céline Furne,3 Elise Madeuf,4 Christoph Höennscheidt,1 Deanne Mraz Robinson5,6 1R&D, Merz Pharmaceuticals GmbH, Frankfurt am Main, Germany; 2Medical Affairs, Merz North America, Raleigh, NC, USA; 3NAMSA, Chasse sur Rhône, France; 4Preclinical Studies, Voxcan, Marcy L´Etoile, France; 5Modern Dermatology of Connecticut, Westport, CT, USA; 6Yale-New Haven Hospital, New Haven, CT, USACorrespondence: Wojciech DanyszMerz Pharmaceuticals GmbH, Eckenheimer Landstrasse 100, Frankfurt am Main 60318, GermanyEmail Wojciech.danysz@merz.deIntroduction: Calcium hydroxylapatite microspheres suspended in a gel carrier of sodium carboxymethylcellulose (CaHA; Radiesse®) has demonstrated safe and effective restoration of facial volume in clinical trials, as well as collagen biostimulation leading to skin quality improvement. The potential with CaHA, as with any filler, to produce overcorrection and subsequent complications has led to the search for a reversal agent. Sodium thiosulfate (STS) was proposed based on experience with it as a chelating agent to treat calciphylaxis. Previous pilot studies with small sample sizes have suggested its efficacy in the reduction of CaHA volume and nodule formation. The present study focuses on the verification of this effect using various readout methods in preclinical experiments.Methods: We use both in vitro (co-incubation of STS with CaHA) and in vivo (injections in farm pig) methods with readout techniques such as 3D camera analysis, micro-computed tomography ex vivo (μCT), computed tomography in vivo (CT), histopathology and scanning electron microscopy.Results: We did not obtain any indications of CaHA degradation by STS, either in vitro or in vivo. 3D-camera analysis also did not show any decreasing effect of STS on CaHA. However, histology, μCT ex vivo, and CT in vivo indicated a decrease of Radiesse amount/volume after STS treatment, which could be attributed to dispersion effect. It should be noted that necrosis and haemorrhages were observed after STS treatment.Discussion: Results suggest no indication of CaHA microspheres degradation with STS and that the STS mechanism of action on CaHA is consistent with a dispersion effect. Observed necrosis is a further obstacle in the use of STS.Keywords: calcium hydroxylapatite, sodium thiosulfate, dispersion effect, computed tomography, histology, 3D camera

L-DOPA remains the gold-standard treatment for Parkinson's disease but causes motor fluctuations and dyskinesia. Metabotropic glutamate receptor type 5 (mGluR5) has been proposed as a target for antidyskinetic therapies. Here, we evaluate the effects of fenobam, a noncompetitive mGluR5 antagonist already tested in humans, using rodent and nonhuman primate models of L-DOPA-induced dyskinesia. In both animal models, acute administration of fenobam attenuated the L-DOPA-induced abnormal involuntary movements (50-70% reduction at the doses of 30mg/kg in rats and 10mg/kg in monkeys). The effect consisted in a reduction of peak-dose dyskinesia, whereas the end-dose phase was not affected. Chronic administration of fenobam to previously drug-naive animals (de novo treatment) attenuated the development of peak-dose dyskinesia without compromising the anti-parkinsonian effect of L-DOPA. In addition, fenobam prolonged the motor stimulant effect of L-DOPA. We conclude that fenobam acts similarly in rat and primate models of L-DOPA-induced dyskinesia and that it represents a good candidate for antidyskinetic treatment in Parkinson's disease.

International audience; Benzylquinolone carboxylic acid (BQCA) is a recently described cholinergic muscarinic M(1) receptor positive allosteric modulator having potential as cognitive enhancer in dementia. The present study focused on the characterisation of BQCA's mode of action in relation to positive effects on memory and side-effects in an animal model. To get insight into this mode of action, in vitro receptor potency/left shift experiments in cells stably expressing the rat's M(1) receptor were performed. They revealed an inflection point value of BQCA corresponding to 306nM, and potentiation of the agonist response up to 47-fold in presence of 10μM of BQCA. In vivo, brain microdialysis showed a maximal brain level of 270nM, 40min after i.p. administration at 10mg/kg. Based on in vitro data obtained with this dose, it can be concluded that BQCA reaches brain levels which should potentiate the agonist response about 4-fold. Behavioural data confirmed that BQCA used at 10mg/kg attenuated scopolamine-induced memory deficit in a spontaneous alternation task. Moreover, BQCA showed no side effect at 10mg/kg and above in spontaneous locomotion and salivation tests. The profile of BQCA observed in the present study displays a clear advantage over the M(1)-M(3) agonist cevimeline. The present data show the therapeutic potential of the M(1) receptor positive allosteric modulator BQCA for the treatment of memory deficits observed in Alzheimer's disease.

l-DOPA-induced dyskinesia (LID) in Parkinson's disease has been linked to altered dopamine and glutamate transmission within the basal ganglia. In the present study, we compared compounds targeting specific subtypes of glutamate receptors or calcium channels for their ability to attenuate LID and the associated activation of striatal nuclear signaling and gene expression in the rat. Rats with 6-hydroxydopamine lesions were treated acutely or chronically with l-DOPA in combination with the following selective compounds: antagonists of group I metabotropic glutamate receptors (mGluR), (2-methyl-1,3-thiazol-4-yl) ethynylpyridine (MTEP) for mGluR5 and (3-ethyl-2-methyl-quinolin-6-yl)-(4-methoxy-cyclohexyl)-methanone methane sulfonate (EMQMCM) for mGluR1; an agonist of group II mGluR, 1R,4R,5S,6R-2-oxa-4-aminobicyclo[3.1.0]hexane-4,6-dicarboxylate (LY379268); N-methyl-d-aspartate (NMDA)-R2B subunit (NR2B)-selective NMDA receptor antagonists 1-[2-(4-hydroxyphenoxy)ethyl]-4-[(4-methylphenyl)methyl]-4-piperidinol hydrochloride (Ro631908) and (±)-(R*,S*)-α-(4-hydroxyphenyl)-β-methyl-4-(phenylmethyl)1-piperidine propanol (Ro256981); and an L-type calcium channel antagonist, 4-(4-benzofurazanyl)-1,-4-dihydro-2,6-dimethyl-3,5-pyridinedicarboxylic acid methyl 1-methylethyl ester (isradipine). Dyskinesia and rotarod performance were monitored during chronic drug treatment. The striatal expression of phospho-extracellular signal-regulated kinase (ERK) 1/2 and mitogen- and stress-activated kinase (MSK)-1, or prodynorphin mRNA was examined after acute or chronic treatment, respectively. In the acute treatment studies, only MTEP and EMQMCM significantly attenuated l-DOPA-induced phospho-ERK1/2 and/or phospho-MSK-1 expression, with MTEP being the most effective (70–80% reduction). In the chronic experiment, only MTEP significantly attenuated dyskinesia without adverse motor effects, whereas EMQMCM and LY379268 inhibited the l-DOPA-induced improvement in rotarod performance. The NR2B antagonist had positive antiakinetic effects but did not reduce dyskinesia. Only MTEP blocked the up-regulation of prodynorphin mRNA induced by l-DOPA. Among the pharmacological treatments examined, MTEP was most effective in inhibiting LID and the associated molecular alterations. Antagonism of mGluR5 seems to be a promising strategy to reduce dyskinesia in Parkinson's disease.

Procedures for studying the effects of medications on satiation will assist the development of obesity medications.Develop a procedure for measuring satiation during consumption of bland and highly palatable food and determine the effect of acute intramuscular administration of dexfenfluramine (DFEN), which increases serotonin levels, and memantine (MEM), which blocks N-methyl-D: -aspartate receptors.A modified progressive ratio (PR) procedure was used to track changes in reinforcing strength when a food was consumed. The response requirement increased after each reinforcement, and reinforcing strength was estimated using the breakpoint (BP), which was the last completed response cost. There was one preferred food (sweet candy) and one chow pellet PR session per week. During each session, four male and four female adult baboons experienced three 1-h PR trials, separated by 30 min. Chow pellets were available at all other times. We examined the BP for one to 20 candies or chow pellets. Drug effects were examined when baboons had access to one and ten candies or chow pellets.BPs for candy were greater than for pellets. Varying the pellet/candy pieces per delivery produced an inverted U-shaped function on the first trial, i.e., maximal BP was observed for three items, and the BP for multiple items, but not a single item, decreased across trials, i.e., BP decreased with food intake and satiation. DFEN and MEM decreased responding with the greatest effects at ten deliveries, suggesting that DFEN and MEM enhanced satiation.Drugs that enhance satiation for several types of food may be particularly effective for decreasing food intake.

Metabotropic glutamate receptor type 5 (mGluR5) modulates dopamine and glutamate neurotransmission at central synapses. In this study, we addressed the role of mGluR5 in l-DOPA-induced dyskinesia, a movement disorder that is due to abnormal activation of both dopamine and glutamate receptors in the basal ganglia. A selective and potent mGluR5 antagonist, 3-[(2-methyl-1,3-thiazol-4-yl)ethynyl] pyridine, was tested for its ability to modulate molecular, behavioural and neurochemical correlates of dyskinesia in 6-hydroxydopamine-lesioned rats treated with l-DOPA. The compound significantly attenuated the induction of abnormal involuntary movements (AIMs) by chronic l-DOPA treatment at doses that did not interfere with the rat physiological motor activities. These effects were paralleled by an attenuation of molecular changes that are strongly associated with the dyskinesiogenic action of l-DOPA (i.e. up-regulation of prodynorphin mRNA in striatal neurons). Using in vivo microdialysis, we found a temporal correlation between the expression of l-DOPA-induced AIMs and an increased GABA outflow within the substantia nigra pars reticulata. When co-administered with l-DOPA, 3-[(2-methyl-1,3-thiazol-4-yl)ethynyl] pyridine greatly attenuated both the increase in nigral GABA levels and the expression of AIMs. These data demonstrate that mGluR5 antagonism produces strong anti-dyskinetic effects in an animal model of Parkinson's disease through central inhibition of the molecular and neurochemical underpinnings of l-DOPA-induced dyskinesia.

We investigated the effects of pretreatment with low-affinity, uncompetitive NMDA receptor antagonists on morphine-induced antinociception in rats using the same intensity of thermal stimulus applied to the tail and the paws. Similar baseline responses to thermal stimuli of the same intensity were recorded from tails and hind paws. However, morphine produced equal antinociception from the tail and hind paw when used at doses of 2.5 and 6 mg/kg, respectively. These doses were used in further experiments. Thirty minutes before morphine, rats were administered the NMDA receptor antagonists dextromethorphan (2.5–30 mg/kg), memantine (2.5–15 mg/kg) and MRZ 2/579 (1-amino-1,3,3,5,5-pentamethyl-cyclohexane HCl) (1.25–10 mg/kg). All three compounds significantly and dose-dependently potentiated morphine-induced antinociception recorded from the tail. However, none of these NMDA receptor antagonists affected morphine antinociception recorded from the paw. These findings suggest that low-affinity NMDA receptor antagonists modulate differently morphine antinociceptive activity recorded from the tail and hind paws.

[1-[2-[bis(trifluoromethyl)-phenyl]methoxy]ethyl]- 1,2,5,6-tetrahydro-3-pyridine-carboxylic acid, HCl (Cl-966, Parke-Davis) is a new specific inhibitor of GABA uptake to neurons that is severalfold more potent than for inhibition of glycine or glutamate uptake. Cl-966 crosses the blood-brain barrier and when injected intravenously into rats (doses up to 10.5 μM/Kg = 5.0 mg/kg) produces only marginal behavioral effects. Cl-966 also produces a modest reversal of punished-suppressed drinking behavior in thristy rats both in the conflict and phenylenetetrazole (PTZ)-induced proconflict Vogel test. However an inactive dose of Cl-966 (6.3 μM/kg i.v., 90 min prior to the test) significantly potentiated the anticonflict and anti-PTC-induced proconflict action of diazepam and alprazolam. The anticonflict/antiproconflict ED50 ratio for diazepam was shifted from 1.2 to 1.0 and that of alprazolam from 13.0 to 7.0 after pretreatment with Cl-966. These results suggest that Cl-966, while it may produce increasing GABAergic tone throughout the CNS, selectively enhances the action of GABA at GABAA receptor subtypes whose sensitivity is preferentially increased by administration of positive allosteric modulators. Therefore Cl-966 may represent a very useful drug to study modifications of animal behavior in relation to the function of GABAergic transmission in specific brain areas.

This review describes the preclinical mechanisms that may underlie the increased therapeutic benefit of combination therapy—with the N-methyl-d-aspartate receptor antagonist, memantine, and an acetylcholinesterase inhibitor (AChEI)—for the treatment of Alzheimer’s disease (AD). Memantine, and the AChEIs target two different aspects of AD pathology. Both drug types have shown significant efficacy as monotherapies for the treatment of AD. Furthermore, clinical observations indicate that their complementary mechanisms offer superior benefit as combination therapy. Based on the available literature, the authors have considered the preclinical mechanisms that could underlie such a combined approach. Memantine addresses dysfunction in glutamatergic transmission, while the AChEIs serve to increase pathologically lowered levels of the neurotransmitter acetylcholine. In addition, preclinical studies have shown that memantine has neuroprotective effects, acting to prevent glutamatergic over-stimulation and the resulting neurotoxicity. Interrelations between the glutamatergic and cholinergic pathways in regions of the brain that control learning and memory mean that combination treatment has the potential for a complex influence on disease pathology. Moreover, studies in animal models have shown that the combined use of memantine and the AChEIs can produce greater improvements in measures of memory than either treatment alone. As an effective approach in the clinical setting, combination therapy with memantine and an AChEI has been a welcome advance for the treatment of patients with AD. Preclinical data have shown how these drugs act via two different, but interconnected, pathological pathways, and that their complementary activity may produce greater effects than either drug individually.

The effects of the alpha-adrenoceptor antagonists prazosin, phentolamine and yohimbine upon 5-methoxy-N,N-dimethyltryptamine (5-MeODMT)-induced analgesia were tested in the hot-plate, tail-flick and shock-titration tests of nociception with rats. Intrathecally injected yohimbine and phentolamine blocked or attenuated the analgesia produced by systemic administration of 5-MeODMT in all three nociceptive tests. Intrathecally administered prazosin attenuated the analgesic effects of 5-MeODMT in the hot-plate and tail-flick tests, but not in the shock titration test. Intrathecal yohimbine showed a dose-related lowering of pain thresholds in saline and 5-MeODMT-treated animals. Phentolamine and prazosin produced normal dose-related curves in the hot-plate test and biphasic effects in the shock titration and tail-flick tests. These results demonstrate a functional interaction between alpha 2-adrenoceptors and 5-HT agonist-induced analgesia at a spinal level in rats.