Marc Ceusters

Pharmacology of a Novel Central Nervous System–Penetrant P2X7 Antagonist JNJ-42253432

In the central nervous system, the ATP-gated Purinergic receptor P2X ligand-gated ion channel 7 (P2X7) is expressed in glial cells and modulates neurophysiology via release of gliotransmitters, including the proinflammatory cytokine interleukin (IL)-1β. In this study, we characterized JNJ-42253432 [2-methyl-N-([1-(4-phenylpiperazin-1-yl)cyclohexyl]methyl)-1,2,3,4-tetrahydroisoquinoline-5-carboxamide] as a centrally permeable (brain-to-plasma ratio of 1), high-affinity P2X7 antagonist with desirable pharmacokinetic and pharmacodynamic properties for in vivo testing in rodents. JNJ-42253432 is a high-affinity antagonist for the rat (pKi 9.1 ± 0.07) and human (pKi 7.9 ± 0.08) P2X7 channel. The compound blocked the ATP-induced current and Bz-ATP [2′(3′)-O-(4-benzoylbenzoyl)adenosine-5′-triphosphate tri(triethylammonium)]–induced release of IL-1β in a concentration-dependent manner. When dosed in rats, JNJ-42253432 occupied the brain P2X7 channel with an ED50 of 0.3 mg/kg, corresponding to a mean plasma concentration of 42 ng/ml. The compound blocked the release of IL-1β induced by Bz-ATP in freely moving rat brain. At higher doses/exposure, JNJ-42253432 also increased serotonin levels in the rat brain, which is due to antagonism of the serotonin transporter (SERT) resulting in an ED50 of 10 mg/kg for SERT occupancy. JNJ-42253432 reduced electroencephalography spectral power in the α-1 band in a dose-dependent manner; the compound also attenuated amphetamine-induced hyperactivity. JNJ-42253432 significantly increased both overall social interaction and social preference, an effect that was independent of stress induced by foot-shock. Surprisingly, there was no effect of the compound on either neuropathic pain or inflammatory pain behaviors. In summary, in this study, we characterize JNJ-42253432 as a novel brain-penetrant P2X7 antagonist with high affinity and selectivity for the P2X7 channel.

Synthesis and anti-angiogenic activity of 6-(1,2,4-thiadiazol-5-yl)-3-amino pyridazine derivatives

General screening for inhibitors of microvessel growth in vitro in the rat aortic ring assay led to the discovery of a novel series of thiadiazole pyridazine compounds with potential anti-angiogenic activity. Chemical optimization produced orally active compounds with potent in vitro and in vivo anti-angiogenesis and anti-tumor activities.

Efficacy and safety of an adjunctive mGlu2 receptor positive allosteric modulator to a SSRI/SNRI in anxious depression.

This phase 2a, randomized, multicenter, double-blind, proof-of-concept study was designed to evaluate, efficacy, safety and tolerability of JNJ-40411813/ADX71149, a novel metabotropic glutamate 2 receptor positive allosteric modulator as an adjunctive treatment for major depressive disorder (MDD) with significant anxiety symptoms. Eligible patients (18-64 years) had a DSM-IV diagnosis of MDD, Hamilton Depression Rating Scale-17 (HDRS17) score of ≥ 18, HDRS17 anxiety/somatization factor score of ≥ 7, and an insufficient response to current treatment with a selective serotonin reuptake inhibitor or serotonin-norepinephrine reuptake inhibitor. The doubly-randomized, 8-week double-blind treatment phase was comprised of two 4-week periods, from which a combined test statistic was generated, with pre-determined weights assigned to each of the 2 treatment periods. Period 1: patients (n=121) were randomly assigned (1:1) to JNJ-40411813 (n=62; 50mg to 150 mg b.i.d, flexibly dosed) or placebo (n=59); Period 2: placebo-treated patients (n=22) who continued to meet entry severity criteria were re-randomized (1:1) to JNJ-40411813 or placebo, while other patients underwent sham re-randomization and continued on their same treatment. Of 121 randomized patients, 100 patients (82.6%) were completers. No efficacy signal was detected on the primary endpoint, the 6-item Hamilton Anxiety Subscale (HAM-A6, p=0.51). Efficacy signals (based on prespecified 1-sided p<0.20) were evident on several secondary outcome measures of both depression (HDRS17 total score, 6-item subscale of HDRS17 assessing core depressive symptoms [HAM-D6], and Inventory of Depressive Symptomatology [IDS-C30]) and anxiety (HDRS17 anxiety/somatization factor, IDS-C30 anxiety subscale). Although well-tolerated, the results do not suggest efficacy for JNJ-40411813 as an adjunctive treatment for patients with MDD with significant anxious symptoms in the dose range studied.

4-Methyl-6,7-dihydro-4H-triazolo[4,5-c]pyridine-Based P2X7 Receptor Antagonists: Optimization of Pharmacokinetic Properties Leading to the Identification of a Clinical Candidate

The synthesis and preclinical characterization of novel 4-(R)-methyl-6,7-dihydro-4H-triazolo[4,5-c]pyridines that are potent and selective brain penetrant P2X7 antagonists are described. Optimization efforts based on previously disclosed unsubstituted 6,7-dihydro-4H-triazolo[4,5-c]pyridines, methyl substituted 5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazines, and several other series lead to the identification of a series of 4-(R)-methyl-6,7-dihydro-4H-triazolo[4,5-c]pyridines that are selective P2X7 antagonists with potency at the rodent and human P2X7 ion channels. These novel P2X7 antagonists have suitable physicochemical properties, and several analogs have an excellent pharmacokinetic profile, good partitioning into the CNS and show robust in vivo target engagement after oral dosing. Improvements in metabolic stability led to the identification of JNJ-54175446 (14) as a candidate for clinical development. The drug discovery efforts and strategies that resulted in the identification of the clinical candidate are described herein.

Efficacy of mGlu2‐positive allosteric modulators alone and in combination with levetiracetam in the mouse 6 Hz model of psychomotor seizures

The metabotropic glutamate receptor subtype 2 (mGlu2) possesses both orthosteric and allosteric modulatory sites, are expressed in the frontal cortex and limbic structures, and can affect excitatory synaptic transmission. Therefore, mGlu2 is a potential therapeutic target in the treatment of epilepsy. The present study seeks to evaluate the anticonvulsant potential of mGlu2‐acting compounds.

Discovery of 8-Trifluoromethyl-3-cyclopropylmethyl-7-[(4-(2,4-difluorophenyl)-1-piperazinyl)methyl]-1,2,4-triazolo[4,3-a]pyridine (JNJ-46356479), a Selective and Orally Bioavailable mGlu2 Receptor Positive Allosteric Modulator (PAM)

Positive allosteric modulators of the metabotropic glutamate 2 receptor have generated great interest in the past decade. There is mounting evidence of their potential as therapeutic agents in the treatment of multiple central nervous system disorders. We have previously reported substantial efforts leading to potent and selective mGlu2 PAMs. However, finding compounds with the optimal combination of in vitro potency and good druglike properties has remained elusive, in part because of the hydrophobic nature of the allosteric binding site. Herein, we report on the lead optimization process to overcome the poor solubility inherent to the advanced lead 6. Initial prototypes already showed significant improvements in solubility while retaining good functional activity but displayed new liabilities associated with metabolism and hERG inhibition. Subsequent subtle modifications efficiently addressed those issues leading to the identification of compound 27 (JNJ-46356479). This new lead represents a more balanced profile that offers a significant improvement on the druglike attributes compared to previously reported leads.

Potent and selective pharmacodynamic synergy between the metabotropic glutamate receptor subtype 2–positive allosteric modulator JNJ‐46356479 and levetiracetam in the mouse 6‐Hz (44‐mA) model

We previously demonstrated that positive allosteric modulators (PAMs) of metabotropic glutamate subtype 2 (mGlu2) receptors have potential synergistic interactions with the antiseizure drug levetiracetam (LEV). The present study utilizes isobolographic analysis to evaluate the combined administration of JNJ‐46356479, a selective and potent mGlu2 PAM, with LEV as well as sodium valproate (VPA) and lamotrigine (LTG).

18F-JNJ-64413739, a novel PET ligand for the P2X7 ion channel: radiation dosimetry, kinetic modeling, test-retest variability and occupancy of the P2X7 antagonist JNJ-54175446

The P2X7 receptor (P2X7R) is an adenosine triphosphate–gated ion channel that is predominantly expressed on microglial cells in the central nervous system. We report the clinical qualification of P2X7-specific PET ligand 18F-JNJ-64413739 in healthy volunteers, including dosimetry, kinetic modeling, test-retest variability, and blocking by the P2X7 antagonist JNJ-54175446. Methods: Whole-body dosimetry was performed in 3 healthy male subjects by consecutive whole-body PET/CT scanning, estimation of the normalized cumulated activity, and calculation of the effective dose using OLINDA (v1.1). Next, 5 healthy male subjects underwent a 120-min dynamic 18F-JNJ-64413739 PET/MRI scan with arterial blood sampling to determine the appropriate kinetic model. For this purpose, 1- and 2-tissue compartment models and Logan graphic analysis (LGA) were evaluated for estimating regional volumes of distribution (VT). PET/MRI scanning was repeated in 4 of these subjects to evaluate medium-term test-retest variability (interscan interval, 26–97 d). For the single-dose occupancy study, 8 healthy male subjects underwent baseline and postdose 18F-JNJ-64413739 PET/MRI scans 4–6 h after the administration of a single oral dose of JNJ-54175446 (dose range, 5–300 mg). P2X7 occupancies were estimated using a Lassen plot and regional baseline and postdose VT. Results: The average (mean ± SD) effective dose was 22.0 ± 1.0 μSv/MBq. The 2-tissue compartment model was the most appropriate kinetic model, with LGA showing very similar results. Regional 2-tissue compartment model VT values were about 3 and were rather homogeneous across all brain regions, with slightly higher estimates for the thalamus, striatum, and brain stem. Between-subject VT variability was relatively high, with cortical VT showing an approximate 3-fold range across subjects. As for time stability, the acquisition time could be reduced to 90 min. The average regional test-retest variability values were 10.7% ± 2.2% for 2-tissue compartment model VT and 11.9% ± 2.2% for LGA VT. P2X7 occupancy approached saturation for single doses of JNJ-54175446 higher than 50 mg, and no reference region could be identified. Conclusion: 18F-JNJ-64413739 is a suitable PET ligand for the quantification of P2X7R expression in the human brain. It can be used to provide insight into P2X7R expression in health and disease, to evaluate target engagement by P2X7 antagonists, and to guide dose selection.

Clinical pharmacokinetics, pharmacodynamics, safety, and tolerability of JNJ-54175446, a brain permeable P2X7 antagonist, in a randomised single-ascending dose study in healthy participants

Background: Central nervous system-derived interleukin-1β plays a role in mood disorders. P2X7 receptor activation by adenosine-triphosphate leads to the release of interleukin-1β. Aims: This first-in-human study evaluated safety, tolerability, pharmacokinetics and pharmacodynamics of a novel central nervous system-penetrant P2X7 receptor antagonist, JNJ-54175446, in healthy participants. Methods: The study had three parts: an ascending-dose study in fasted participants (0.5–300 mg JNJ-54175446); an ascending-dose study in fed participants (50–600 mg); and a cerebrospinal fluid study (300 mg). Target plasma concentrations were based on estimated plasma effective concentration (EC)50 (105 ng/mL) and EC90 (900 ng/mL) values for central nervous system P2X7 receptor binding. Results: Seventy-seven participants received a single oral dose of JNJ-54175446 (n=59) or placebo (n=18). Area under the curve of concentration time extrapolated to infinity (AUC∞) increased dose-proportionally; maximum concentration (Cmax) of plasma (Cmax,plasma) increased less than dose-proportionally following single doses of JNJ-54175446. Because food increases bioavailability of JNJ-54175446, higher doses were given with food to evaluate safety at higher exposures. The highest Cmax,plasma reached (600 mg, fed) was 1475±163 ng/mL. JNJ-54175446 Cmax in cerebrospinal fluid, a proxy for brain penetration, was seven times lower than in total plasma; unbound Cmax,plasma and Cmax,CSF were comparable (88.3±35.7 vs 114±39 ng/mL). JNJ-54175446 inhibited lipopolysaccharide/3′-O-(4-benzoylbenzoyl)-ATP-induced interleukin-1β release from peripheral blood in a dose-dependent manner (inhibitory concentration (IC)50:82 ng/mL; 95% confidence interval: 48–94). Thirty-three of 59 (55.9%) participants reported at least one treatment-emergent adverse event; the most common adverse event being headache (11/59, 18.6%). Conclusion: Plasma exposure of JNJ-54175446 was dose-dependent. No serious adverse events occurred. Single-dose administration of JNJ-54175446>10 mg attenuated ex-vivo lipopolysaccharide-induced interleukin-1β release in peripheral blood. Passive brain penetration of JNJ-54175446 was confirmed.