Clinical pharmacokinetics of leriglitazone and a translational approach using PBPK modeling to guide the selection of the starting dose in children.

Leriglitazone is a unique peroxisome proliferator-activated receptor-gamma (PPARγ) agonist that crosses the blood-brain barrier in humans and clinical trials have shown evidence of efficacy in neurodegenerative diseases. At clinical doses which are well-tolerated, leriglitazone reaches the target central nervous system (CNS) concentrations that are needed for PPARγ engagement and efficacy; PPARγ engagement is also supported by clinical and anti-inflammatory biomarker changes in the Cerebrospinal fluid in the CNS. Plasma pharmacokinetics (PK) of leriglitazone were determined in a phase 1 study in male healthy volunteers comprising a single ascending dose (SAD) and a multiple ascending dose (MAD) at oral doses of 30, 90, and 270 mg and 135 and 270 mg, respectively. Leriglitazone was rapidly absorbed with no food effect on overall exposure and showed a linear PK profile with dose-exposure correlation. A physiologically based pharmacokinetic (PBPK) model was developed for leriglitazone based on phase 1 data (SAD part) and incorporated CYP3A4 (fmCYP3A4 = 24%) and CYP2C8-mediated (fmCYP2C8 = 45%) metabolism, as well as biliary clearance (feBIL = 19.5%) derived from in vitro data, and was verified by comparing the observed versus predicted concentration-time profiles from the MAD part. The PBPK model was prospectively applied to predict the starting pediatric doses and was preliminarily verified with data from five pediatric patients.

Effect of the Metabotropic Glutamate Receptor Type 5 Negative Allosteric Modulator Dipraglurant on Motor and Non-Motor Symptoms of Parkinson's Disease.

Parkinson's disease (PD) patients suffer not only from the primary motor symptoms of the disease but also from a range of non-motor symptoms (NMS) that cause disability and low quality of life. Excessive glutamate activity in the basal ganglia resulting from degeneration of the nigrostriatal dopamine pathway has been implicated in the motor symptoms, NMS and dyskinesias in PD patients. In this study, we investigated the effects of a selective mGlu5 negative allosteric modulator (NAM), dipraglurant, in a rodent motor symptoms model of PD, but also in models of anxiety, depression and obsessive-compulsive disorder, all of which are among the most prevalent NMS symptoms. Dipraglurant is rapidly absorbed after oral administration, readily crosses the blood-brain barrier, and exhibits a high correlation between plasma concentration and efficacy in behavioral models. In vivo, dipraglurant dose-dependently reduced haloperidol-induced catalepsy, increased punished licks in the Vogel conflict-drinking model, decreased immobility time in the forced swim test, decreased the number of buried marbles in the marble-burying test, but had no effect on rotarod performance or locomotor activity. These findings suggest that dipraglurant may have benefits to address some of the highly problematic comorbid non-motor symptoms of PD, in addition to its antidyskinetic effect demonstrated in PD-LID patients.

First-in-Human Study in Healthy Subjects with the Noncytotoxic Monoclonal Antibody OSE-127, a Strict Antagonist of IL-7Rα.

OSE-127 is a humanized mAb targeting the IL-7Rα-chain (CD127), under development for inflammatory and autoimmune disease treatment. It is a strict antagonist of the IL-7R pathway, is not internalized by target cells, and is noncytotoxic. In this work, a first-in-human, phase I, randomized, double-blind, placebo-controlled, single-center study was carried out to determine the safety, pharmacokinetics, pharmacodynamics, and immunogenicity of OSE-127 administration. Sixty-three healthy subjects were randomly assigned to nine groups: six single ascending dose groups with i.v. administration (0.002-10 mg/kg), a single s.c. treatment group (1 mg/kg), and two double i.v. injection groups (6 or 10 mg/kg). Subjects were followed during <146 d. OSE-127's pharmacokinetic half-life after a single dose increased from 4.6 (1 mg/kg) to 11.7 d (10 mg/kg) and, after a second dose, from 12.5 (6 mg/kg) to 16.25 d (10 mg/kg). Receptor occupancy was ≥95% at doses ≥0.02 mg/kg, and this saturation level was maintained >100 d after two i.v. infusions at 10 mg/kg. IL-7 consumption was inhibited by OSE-127 administration, as demonstrated by a decreased IL-7 pathway gene signature in peripheral blood cells and by ex vivo T lymphocyte restimulation experiments. OSE-127 was well tolerated, with no evidence of cytokine-release syndrome and no significant alteration of blood lymphocyte counts or subset populations. Altogether, the observed lack of significant lymphopenia or serious adverse events, concomitant with the dose-dependent inhibition of IL-7 consumption by target cells, highlights that OSE-127 may show clinical activity in IL-7R pathway-involved diseases.

SENS-401 Effectively Reduces Severe Acoustic Trauma-Induced Hearing Loss in Male Rats With Twice Daily Administration Delayed up to 96 hours.

HYPOTHESIS: SENS-401 (R-azasetron besylate) is effective against severe acoustic trauma-induced hearing loss. BACKGROUND: SENS-401 has calcineurin inhibiting properties and attenuates cisplatin-induced hearing loss in a rat model. Cisplatin-induced and acoustic trauma-induced hearing loss share common apoptotic pathways. METHODS: The dose-response relationship of SENS-401 (6.6 mg/kg BID, 13.2 mg/kg BID, 26.4 mg/kg QD) and treatment time-window (13.2 mg/kg BID starting 24, 72, and 96 h posttrauma) versus placebo for 28 days were evaluated in a male rat model of severe acoustic trauma-induced hearing loss (120 dB SPL, 2 h) using auditory brainstem response (ABR) and distortion product otoacoustic emissions (DPOAE) measures followed by cochlear outer hair cell (OHC) counting with myosin-VIIa immunolabeling. RESULTS: All SENS-401 doses improved ABR threshold shift and recovery, reaching statistical significance (p < 0.05) for ABR threshold recoveries after 28-days treatment. DPOAE amplitude loss and recovery improved markedly for 13.2 mg/kg BID SENS-401, reaching significance after 14 days (p < 0.05). Significant improvements in ABR threshold shifts/recovery and DPOAE amplitude loss occurred with up to 96-hours delay in initiating SENS-401 (p < 0.05), and in DPOAE amplitude recovery with up to 72-hours delay (p < 0.05). Significantly more surviving OHCs were present after SENS-401 treatment compared with placebo after 24 to 96-hours delay posttrauma, with up to 5.3-fold more cells in the basal cochlea turn. CONCLUSIONS: In vivo data support the otoprotective potential of twice daily oral SENS-401. Improvements in hearing loss recovery make SENS-401 a promising clinical candidate for acoustic trauma-induced hearing loss, including when treatment is not initiated immediately.

Safety, tolerability, pharmacokinetics and pharmacokinetic-pharmacodynamic modelling of the novel H4 receptor inhibitor SENS-111 using a modified caloric test in healthy subjects.

AIM: A Phase 1 study was performed to evaluate safety, pharmacokinetics (PK) and pharmacodynamics (PD) of the selective histamine H4 receptor antagonist SENS-111, an oral small molecule. METHODS: One hundred healthy subjects were randomized in a placebo-controlled, double-blind study evaluating single-ascending doses (SAD; 100-500 mg) and multiple-ascending doses (MAD; 50-150 mg day-1 , 4 days; 200-250 mg day-1 , 7 days). Effects of SENS-111 on nystagmus and vertigo induced by modified caloric tests were measured in the MAD studies. Population PK and PK/PD models were developed using a nonlinear mixed-effects approach. RESULTS: SENS-111 was well tolerated with mild to moderate events. No sedation was reported. A maximal tolerated dose was not reached. Dose-proportional increases in concentrations were seen up to 200 mg and more than dose-proportional thereafter, with mean half-life between 24 and 56 h. The caloric test induced mild but measurable vertigo and nystagmus with large intra/inter-individual variation for all parameters. SENS-111 did not significantly impact nystagmus but significantly improved latency of vertigo appearance/disappearance, duration and European Evaluation of Vertigo questionnaire parameters vs. baseline. A two-compartment model with first-order absorption, distribution and elimination best fit the data. PK/PD indirect modelling applied to vertigo duration and latency of appearance indicated maximum activity between 100 and 500 ng ml-1 plasma concentrations, corresponding to 100 and 200 mg day-1 , which are appropriate for clinical efficacy evaluations in vestibular diseases. CONCLUSIONS: SENS-111 is a well-tolerated first-in-class H4 receptor antagonist with acceptable PK for oral daily dosing. PK/PD modelling determined plasma concentrations and doses for efficacy studies in patients with vertigo symptoms.

Analgesic effect of ADX71441, a positive allosteric modulator (PAM) of GABAB receptor in a rat model of bladder pain.

Therapeutic use of GABAB receptor agonists for conditions like chronic abdominal pain, overactive bladder (OAB) and gastroesophageal reflux disease (GERD) is severely affected by poor blood-brain barrier permeability and potential side effects. ADX71441 is a novel positive allosteric modulator (PAM) of the GABAB receptor that has shown encouraging results in pre-clinical models of anxiety, pain, OAB and alcohol addiction. The present study investigates the analgesic effect of ADX71441 to noxious stimulation of the urinary bladder and colon in rats. In female Sprague-Dawley rats, systemic (i.p), but not intrathecal (i.t), administration of ADX71441 produced a dose-dependent decrease in viscero-motor response (VMR) to graded urinary bladder distension (UBD) and colorectal distension (CRD). Additionally, intra-cerebroventricular (i.c.v.) administration of ADX71441 significantly decreased the VMRs to noxious UBD. In electrophysiology experiments, the drug did not attenuate the responses of UBD-sensitive pelvic nerve afferent (PNA) fibers to UBD. In contrast, ADX71441 significantly decreased the responses of UBD-responsive lumbosacral (LS) spinal neurons in spinal intact rats. However, ADX71441 did not attenuate these LS neurons in cervical (C1-C2) spinal transected rats. During cystometrogram (CMG) recordings, ADX71441 (i.p.) significantly decreased the VMR to slow infusion without affecting the number of voiding contraction. These results indicate that ADX71441 modulate bladder nociception via its effect at the supra-spinal sites without affecting the normal bladder motility and micturition reflex in naïve adult rats.

ADX71943 and ADX71441, novel positive allosteric modulators of the GABAB receptor with distinct central/peripheral profiles, show efficacy in the monosodium iodoacetate model of chronic osteoarthritis pain in the rat.

We tested novel positive allosteric modulators (PAMs) of the γ-aminobutyric acid receptor B (GABAB), ADX71943 and ADX71441in the monosodium iodoacetate model of chronic osteoarthritis pain in rats with the objective to delineate the role of peripheral versus central GABAB receptor populations in modulation of chronic pain. Anesthetized Sprague-Dawley rats received an injection of monosodium iodoacetate into the knee and were tested for hyperalgesia starting post-MIA day 14. Effects of compounds on ipsilateral joint compression threshold were evaluated on post-MIA day 14 (after acute treatment), as well as after repeated, daily treatment on days 21 and 28 (ADX71943 only) and were compared to those of celecoxib (30mg/kg, p.o.). The PAMs were also tested in the rat rotarod test for potential muscle-relaxant effects. Acutely, ADX71943 (1-30mg/kg, p.o.), the peripherally restricted PAM, resulted in similar increases in pain threshold across the doses on day 14, while showing reduced efficacy on day 21 and no efficacy on day 28. A clear reduction in the efficacy of celecoxib across testing was also noted in this experiment. Acutely ADX71441 (0.3-15mg/kg, p.o.), the central-peripheral PAM, resulted in over 2-fold increases in pain threshold at 15mg/kg (but not at lower doses) on day 14, while causing more modest effects on day 21. Celecoxib increased pain threshold after both acute and daily treatment, showing overall similar efficacy. Thus, early, presumably more inflammatory phase of osteoarthritis pain in more sensitive to GABAB PAMs with peripherally restricted profile, while later, presumably more neuropathic phase is more sensitive to PAMs with central-peripheral profile.

The drug candidate, ADX71441, is a novel, potent and selective positive allosteric modulator of the GABAB receptor with a potential for treatment of anxiety, pain and spasticity.

Positive allosteric modulation of the GABAB receptor is a promising alternative to direct activation of the receptor as a therapeutic approach for treatment of addiction, chronic pain, anxiety, epilepsy, autism, Fragile X syndrome, and psychosis. Here we describe in vitro and in vivo characterization of a novel, potent and selective GABAB positive allosteric modulator (PAM) N-(5-(4-(4-chloro-3-fluorobenzyl)-6-methoxy-3,5-dioxo-4,5-dihydro-1,2,4-triazin-2(3H)-yl)-2-fluorophenyl)acetamide (ADX71441). In vitro, Schild plot and reversibility tests at the target confirmed PAM properties of the compound. In mice and rats ADX71441 is bioavailable after oral administration and is brain penetrant. A single dose of ADX71441 had an anxiolytic-like profile in the mouse marble burying test (minimum effective dose; MED 3 mg/kg) as well as in the elevated plus maze test in mice and rats (both MED 3 mg/kg). Also, in mice, acute administration of ADX71441 reduced visceral pain-associated behaviors in the acetic acid-induced writhing test. ADX71441 dose-dependently reduced time on rotarod in rats (MED 10 mg/kg) indicative of muscle-relaxant qualities. ADX71441 reduced locomotor activity in mice (10 mg/kg) and rats (3 mg/kg) after single dose; however, following sub-chronic administration in mice, 30 mg/kg ADX71441 was associated with normal locomotor activity. While acute administration of ADX71441 reduced body temperature in rats and mice (both MED 10 mg/kg), the effect in the former was transient, rapidly returning to normal levels despite high concentrations of the compound remaining in plasma. Thus, the GABAB PAM ADX71441 represents a valid therapeutic approach for development of novel treatment of anxiety, pain and spasticity.

Profiling of FSHR negative allosteric modulators on LH/CGR reveals biased antagonism with implications in steroidogenesis.

Biased signaling has recently emerged as an interesting means to modulate the function of many G protein-coupled receptors (GPCRs). Previous studies reported two negative allosteric modulators (NAMs) of follicle-stimulating hormone receptor (FSHR), ADX68692 and ADX68693, with differential effects on FSHR-mediated steroidogenesis and ovulation. In this study, we attempted to pharmacologically profile these NAMs on the closely related luteinizing hormone/chorionic gonadotropin hormone receptor (LH/CGR) with regards to its canonical Gs/cAMP pathway as well as to ß-arrestin recruitment in HEK293 cells. The NAMs' effects on cAMP, progesterone and testosterone production were also assessed in murine Leydig tumor cell line (mLTC-1) as well as rat primary Leydig cells. We found that both NAMs strongly antagonized LH/CGR signaling in the different cell models used with ADX68693 being more potent than ADX68692 to inhibit hCG-induced cAMP production in HEK293, mLTC-1 and rat primary Leydig cells as well as ß-arrestin 2 recruitment in HEK293 cells. Interestingly, differential antagonism of the two NAMs on hCG-promoted steroidogenesis in mLTC-1 and rat primary Leydig cells was observed. Indeed, a significant inhibition of testosterone production by the two NAMs was observed in both cell types, whereas progesterone production was only inhibited by ADX68693 in rat primary Leydig cells. In addition, while ADX68693 totally abolished testosterone production, ADX68692 had only a partial effect in both mLTC-1 and rat primary Leydig cells. These observations suggest biased effects of the two NAMs on LH/CGR-dependent pathways controlling steroidogenesis. Interestingly, the pharmacological profiles of the two NAMs with respect to steroidogenesis were found to differ from that previously shown on FSHR. This illustrates the complexity of signaling pathways controlling FSHR- and LH/CGR-mediated steroidogenesis, suggesting differential implication of cAMP and ß-arrestins mediated by FSHR and LH/CGR. Together, our data demonstrate that ADX68692 and ADX68693 are biased NAMs at the LH/CGR in addition to the FSHR. These pharmacological characteristics are important to consider for potential contraceptive and therapeutic applications based on such compounds.

A Phase 2A Trial of the Novel mGluR5-Negative Allosteric Modulator Dipraglurant for Levodopa-Induced Dyskinesia in Parkinson's Disease.

BACKGROUND: The metabotropic glutamate receptor 5-negative allosteric modulator dipraglurant reduces levodopa-induced dyskinesia in the MPTP-macaque model. The objective of this study was to assess the safety, tolerability (primary objective), and efficacy (secondary objective) of dipraglurant on levodopa-induced dyskinesia in Parkinson's disease (PD). METHODS: The study was a phase 2A double-blind, placebo-controlled, randomized (2:1), 4-week, parallel-group, multicenter dose-escalation (from 50 mg once daily to 100 mg 3 times daily) clinical trial involving 76 PD subjects with moderate to severe levodopa-induced dyskinesia. Safety and tolerability were assessed based on clinical and biological examination and adverse events recording. Secondary efficacy outcome measures included the modified Abnormal Involuntary Movement Scale, UPDRS, and diaries. Pharmacokinetics were measured at 3 visits following a single dose. RESULTS: Fifty-two patients were exposed to dipraglurant and 24 to placebo. There were no major safety concerns. Two subjects did not complete the study because of adverse events. Most frequent adverse events included dyskinesia, dizziness, nausea, and fatigue. Dipraglurant significantly reduced peak dose dyskinesia (modified Abnormal Involuntary Movement Scale) on day 1 (50 mg, 20%; P = 0.04) and on day 14 (100 mg, 32%; P =0 .04) and across a 3-hour postdose period on day 14 (P = 0.04). There was no evidence of worsening of parkinsonism. Dipraglurant was rapidly absorbed (tmax = 1 hour). The 100-mg dose led to a mean Cmax of 1844 ng/mL on day 28. CONCLUSIONS: Dipraglurant proved to be safe and well tolerated in its first administration to PD patients. Its efficacy in reversing levodopa-induced dyskinesia warrants further investigations in a larger number of patients. © 2016 International Parkinson and Movement Disorder Society.

Allosteric modulation of metabotropic glutamate receptor 4 activates IDO1-dependent, immunoregulatory signaling in dendritic cells.

Metabotropic glutamate receptor 4 (mGluR4) possesses immune modulatory properties in vivo, such that a positive allosteric modulator (PAM) of the receptor confers protection on mice with relapsing-remitting experimental autoimmune encephalomyelitis (RR-EAE). ADX88178 is a newly-developed, one such mGluR4 modulator with high selectivity, potency, and optimized pharmacokinetics. Here we found that application of ADX88178 in the RR-EAE model system converted disease into a form of mild-yet chronic-neuroinflammation that remained stable for over two months after discontinuing drug treatment. In vitro, ADX88178 modulated the cytokine secretion profile of dendritic cells (DCs), increasing production of tolerogenic IL-10 and TGF-ß. The in vitro effects required activation of a Gi-independent, alternative signaling pathway that involved phosphatidylinositol-3-kinase (PI3K), Src kinase, and the signaling activity of indoleamine 2,3-dioxygenase 1 (IDO1). A PI3K inhibitor as well as small interfering RNA targeting Ido1-but not pertussis toxin, which affects Gi protein-dependent responses-abrogated the tolerogenic effects of ADX88178-conditioned DCs in vivo. Thus our data indicate that, in DCs, highly selective and potent mGluR4 PAMs such as ADX88178 may activate a Gi-independent, long-lived regulatory pathway that could be therapeutically exploited in chronic autoimmune diseases such as multiple sclerosis.

Targeting type-2 metabotropic glutamate receptors to protect vulnerable hippocampal neurons against ischemic damage.

BACKGROUND: To examine whether metabotropic glutamate (mGlu) receptors have any role in mechanisms that shape neuronal vulnerability to ischemic damage, we used the 4-vessel occlusion (4-VO) model of transient global ischemia in rats. 4-VO in rats causes a selective death of pyramidal neurons in the hippocampal CA1 region, leaving neurons of the CA3 region relatively spared. We wondered whether changes in the expression of individual mGlu receptor subtypes selectively occur in the vulnerable CA1 region during the development of ischemic damage, and whether post-ischemic treatment with drugs targeting the selected receptor(s) affords neuroprotection. RESULTS: We found that 4-VO caused significantly reduction in the transcript of mGlu2 receptors in the CA1 region at times that preceded the anatomical evidence of neuronal death. Down-regulation of mGlu2 receptors was associated with reduced H3 histone acetylation at the Grm2 promoter. The transcripts of other mGlu receptor subtypes were unchanged in the CA1 region of 4-VO rats. Ischemia did not cause changes in mGlu2 receptor mRNA levels in the resistant CA3 region, which, interestingly, were lower than in the CA1 region. Targeting the mGlu2 receptors with selective pharmacologic ligands had profound effects on ishemic neuronal damage. Post-ischemic oral treatment with the selective mGlu2 receptor NAM (negative allosteric modulator), ADX92639 (30 mg/kg), was highly protective against ischemic neuronal death. In contrast, s.c. administration of the mGlu2 receptor enhancer, LY487379 (30 mg/kg), amplified neuronal damage in the CA1 region and extended the damage to the CA3 region. CONCLUSION: These findings suggest that the mGlu2 receptor is an important player in mechanisms regulating neuronal vulnerability to ischemic damage, and that mGlu2 receptor NAMs are potential candidates in the experimental treatments of disorders characterized by brain hypoperfusion, such as hypovolemic shock and cardiac arrest.

Discovery of 1-butyl-3-chloro-4-(4-phenyl-1-piperidinyl)-(1H)-pyridone (JNJ-40411813): a novel positive allosteric modulator of the metabotropic glutamate 2 receptor.

We previously reported the discovery of 4-aryl-substituted pyridones with mGlu2 PAM activity starting from the HTS hit 5. In this article, we describe a different exploration from 5 that led to the discovery of a novel subseries of phenylpiperidine-substituted pyridones. The optimization strategy involved the introduction of different spacers between the pyridone core and the phenyl ring of 5. The fine tuning of metabolism and hERG followed by differentiation of advanced leads that were identified on the basis of PK profiles and in vivo potency converged on lead compound 36 (JNJ-40411813). Full in vitro and in vivo profiles indicate that 36 displayed an optimal interplay between potency, selectivity, favorable ADMET/PK and cardiovascular safety profile, and central EEG activity. Compound 36 has been investigated in the clinic for schizophrenia and anxious depression disorders.

Characterization of the novel positive allosteric modulator of the metabotropic glutamate receptor 4 ADX88178 in rodent models of neuropsychiatric disorders.

There is growing evidence that activation of metabotropic glutamate receptor 4 (mGlu4) leads to anxiolytic- and antipsychotic-like efficacy in rodent models, yet its relevance to depression-like reactivity remains unclear. Here, we present the pharmacological evaluation of ADX88178 [5-methyl-N-(4-methylpyrimidin-2-yl)-4-(1H-pyrazol-4-yl)thiazol-2-amine], a novel potent, selective, and brain-penetrant positive allosteric modulator of the mGlu4 receptor in rodent models of anxiety, obsessive compulsive disorder (OCD), fear, depression, and psychosis. ADX88178 dose-dependently reduced the number of buried marbles in the marble burying test and increased open-arm exploration in the elevated plus maze (EPM) test, indicative of anxiolytic-like efficacy. Target specificity of the effect in the EPM test was confirmed using male and female mGlu4 receptor knockout mice. In mice, ADX88178 reduced the likelihood of conditioned freezing in the acquisition phase of the fear conditioning test, yet had no carryover effect in the expression phase. Also, ADX88178 dose-dependently reduced duration of immobility in the forced swim test, indicative of antidepressant-like efficacy. ADX88178 reduced DOI (2,5-dimethoxy-4-iodoamphetamine)-mediated head twitches (albeit with no dose-dependency), and MK-801 [(5S,10R)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine]-induced locomotor hyperactivity in mice, but was inactive in the conditioned avoidance response test in rats. The compound showed good specificity as it had no effect on locomotor activity in mice and rats at efficacious doses. Thus, allosteric activation of mGlu4 receptors can be a promising new therapeutic approach for treatment of anxiety, OCD, fear-related disorders, and psychosis.

The mGluR5 negative allosteric modulator dipraglurant reduces dyskinesia in the MPTP macaque model.

BACKGROUND: Blocking metabotropic glutamate receptor type 5 (mGluR5) has been proposed as a target for levodopa-induced dyskinesias (LID) in Parkinson's disease (PD). We assessed the effect on LID of dipraglurant, a potent selective mGluR5 receptor negative allosteric modulator in the gold-standard LID macaque model. METHODS: Dipraglurant (3, 10, and 30 mg/kg, by mouth) was tested in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) macaque model of LID in a four-way crossover, single-dose, controlled study (n = 8). RESULTS: Dipraglurant inhibited dyskinesias in the LID macaque model, with best effect reached at 30 mg/kg dose with no alteration of levodopa efficacy. CONCLUSION: Acute challenges of dipraglurant were efficacious on choreic and dystonic LID in the MPTP-macaque model. Dipraglurant pharmacokinetic variables were similar to those of levodopa, suggesting that both drugs can be co-administered simultaneously in further studies.

Inhibition of follicle-stimulating hormone-induced preovulatory follicles in rats treated with a nonsteroidal negative allosteric modulator of follicle-stimulating hormone receptor.

We previously described a negative allosteric modulator (NAM) of FSHR (ADX61623) that blocked FSH-induced cAMP and progesterone production but did not block estradiol production. That FSHR NAM did not affect FSH-induced preovulatory follicle development as evidenced by the lack of an effect on the number of FSH-dependent oocytes found in the ampullae following ovulation with hCG. A goal is the development of a nonsteroidal contraceptive. Toward this end, a high-throughput screen using human FSHR identified an additional nonsteroidal small molecule (ADX68692). Although ADX68692 behaved like ADX61623 in inhibiting production of cAMP and progesterone, it also inhibited FSH-induced estradiol in an in vitro rat granulosa primary cell culture bioassay. When immature, noncycling female rats were injected subcutaneously or by oral dosing prior to exogenous FSH administration, it was found that ADX68692 decreased the number of oocytes recovered from the ampullae. The estrous cycles of mature female rats were disrupted by administration by oral gavage of 25 mg/kg and 10 mg/kg ADX68692. In the highest dose tested (25 mg/kg), 55% of animals cohabited with mature males had implantation sites compared to 33% in the 10 mg/kg group and 77% in the control group. A surprising finding was that a structural analog ADX68693, while effectively blocking progesterone production with similar efficacy as ADX68692, did not block estrogen production and despite better oral availability did not decrease the number of oocytes found in the ampullae even when used at 100 mg/kg. These data demonstrate that because of biased antagonism of the FSHR, nonsteroidal contraception requires that both arms of the FSHR steroidogenic pathway must be effectively blocked, particularly estrogen biosynthesis. Thus, a corollary to these findings is that it seems reasonable to propose that the estrogen-dependent diseases such as endometriosis may benefit from inhibition of FSH action at the ovary using the FSHR NAM approach.

Mechanism based neurotoxicity of mGlu5 positive allosteric modulators--development challenges for a promising novel antipsychotic target.

Previous work has suggested that activation of mGlu5 receptor augments NMDA receptor function and thereby may constitute a rational approach addressing glutamate hypofunction in schizophrenia and a target for novel antipsychotic drug development. Here, we report the in vitro activity, in vivo efficacy and safety profile of 5PAM523 (4-Fluorophenyl){(2R,5S)-5-[5-(5-fluoropyridin-2-yl)-1,2,4-oxadiazol-3-yl]-2-methylpiperidin-1-yl}methanone), a structurally novel positive allosteric modulator selective of mGlu5. In cells expressing human mGlu5 receptor, 5PAM523 potentiated threshold responses to glutamate in fluorometric calcium assays, but does not have any intrinsic agonist activity. 5PAM523 acts as an allosteric modulator as suggested by the binding studies showing that 5PAM523 did not displace the binding of the orthosteric ligand quisqualic acid, but did partially compete with the negative allosteric modulator, MPyEP. In vivo, 5PAM523 reversed amphetamine-induced locomotor activity in rats. Therefore, both the in vitro and in vivo data demonstrate that 5PAM523 acts as a selective mGlu5 PAM and exhibits anti-psychotic like activity. To study the potential for adverse effects and particularly neurotoxicity, brain histopathological exams were performed in rats treated for 4 days with 5PAM523 or vehicle. The brain exam revealed moderate to severe neuronal necrosis in the rats treated with the doses of 30 and 50 mg/kg, particularly in the auditory cortex and hippocampus. To investigate whether this neurotoxicity is mechanism specific to 5PAM523, similar safety studies were carried out with three other structurally distinct selective mGlu5 PAMs. Results revealed a comparable pattern of neuronal cell death. Finally, 5PAM523 was tested in mGlu5 knock-out (KO) and wild type (WT) mice. mGlu5 WT mice treated with 5PAM523 for 4 days at 100 mg/kg presented significant neuronal death in the auditory cortex and hippocampus. Conversely, mGlu5 KO mice did not show any neuronal loss by histopathology, suggesting that enhancement of mGlu5 function is responsible for the toxicity of 5PAM523. This study reveals for the first time that augmentation of mGlu5 function with selective allosteric modulators results in neurotoxicity.

Reduction of excessive alcohol drinking by a novel GABAB receptor positive allosteric modulator ADX71441 in mice.

RATIONALE: A promising pharmacotherapy for alcohol use disorders has been positive allosteric modulators (PAMs) of the γ-aminobutyric acid receptor B (GABAB R) since GABAB R PAMs reduce ethanol drinking and self-administration in rodents. OBJECTIVE: The current studies investigated a novel, selective GABAB R PAM, ADX71441, in comparison to naltrexone in a protocol of ethanol binge-like drinking, drinking-in-the-dark (DID), and in a model of long-term, excessive drinking, intermittent access to ethanol (IA). METHODS: Male C57BL/6 J mice were given doses of ADX71441 (3, 10, 30 mg/kg, p.o.) before the fourth test day of repeated DID access to 20 % ethanol. Another group of mice had a history of 4 weeks of IA before ADX71441 (3, 10, 17 mg/kg, p.o.) treatment. The opioid antagonist, naltrexone (0.1, 1, 10 mg/kg, i.p.), was administered to different groups of mice in both protocols as a positive control. RESULTS: In both DID and IA protocols, ADX71441 showed a selective and potent reduction of ethanol drinking, but not water drinking, while naltrexone had a more modest and transient effect on reducing ethanol drinking. The long-lasting effect of ADX71441 agrees with its plasma pharmacokinetics in showing peak concentrations at 2 h followed by a slow decay lasting well beyond 8 h. CONCLUSIONS: These findings support previous studies demonstrating that GABAB R PAMs decrease voluntary ethanol intake without altering water intake. ADX71441 may be a worthwhile candidate for developing a treatment of alcoholism, yet its site of action in the brain and long-term pharmacological effects require further exploration.

A novel series of metabotropic glutamate receptor 5 negative allosteric modulators based on a 4,5,6,7-tetrahydropyrazolo[1,5-a]pyridine core.

A series of potent non-acetylinic negative allosteric modulators of the metabotropic glutamate receptor 5 (mGlu5 NAMs) was developed starting from HTS screening hit 1. Potency was improved via iterative SAR, and physicochemical properties were optimized to deliver orally bioavailable compounds acceptable for in vivo testing. A lead molecule from the series demonstrated dose-dependent activity in the second phase of the rat formalin test from 30 mg/kg, and a preliminary PK/PD relationship was established.

Amorphous solid dispersion successfully improved oral exposure of ADX71943 in support of toxicology studies.

ADX71943 is a potent and selective GABA(b) receptor positive allosteric modulator (PAM) which exhibits poor aqueous solubility at all physiologically relevant pHs. The aim of this study was to identify an adequate formulation to improve the solubility of ADX71943 to achieve a sufficiently high plasma exposure after oral administration to support the toxicology program. Considering the overall physicochemical properties and the low solubility of ADX71943 in a variety of solvents, solid dispersion, and particle size reduction have been successfully chosen as potential strategies to improve its oral bioavailability. Both technologies have proven useful in improving the in vitro dissolution profile and as a result of the solubility enhancement, higher bioavailability was obtained in vivo. As the solid dispersion gave better bioavailability (30-fold compared with the neat active pharmaceutical ingredient (API)), this formulation was selected for the toxicology study. Changing the crystalline form of ADX71943 into amorphous state by preparing a solid dispersion has greatly improved its oral bioavailability and has allowed achieving the required plasma concentration needed in toxicology studies.