Satoshi Yuki

Structure–activity relationship of 3-methyl-1-phenyl-2-pyrazolin-5-one (edaravone)

Abstract This paper describes the discovery of a novel free radical scavenger, 3-methyl-1-phenyl-2-pyrazolin-5-one (edaravone, 1), as a potent antioxidant agent against lipid peroxidation. The structure-activity relationship of edaravone indicated that lipophilic substituents were essential to show its lipid peroxidation-inhibitory activity. In vivo studies revealed that edaravone showed brain-protective activity in a transient ischemia model.

MP-124, a novel poly(ADP-ribose) polymerase-1 (PARP-1) inhibitor, ameliorates ischemic brain damage in a non-human primate model.

Overactivation of poly (ADP-ribose) polymerase-1 (PARP-1) in response to DNA damage is considered to play a crucial role in the development of post-ischemic neuronal injury, such as ischemic stroke. The present study was undertaken to clarify the beneficial effects of MP-124, a novel PARP-1 inhibitor, on neurological deficits and cerebral infarcts following middle cerebral artery occlusion (MCAO) in the monkey. The effects of MP-124 on cerebral infarcts and neurological deficits in monkeys were investigated in permanent MCAO (pMCAO) and transient MCAO (tMCAO) models. In a dose-dependency study, the neurological deficits and cerebral infarct volume were assessed at 28h after pMCAO. MP-124 significantly reduced the total infarct volume, including that in the cortex/white matter and striatum, at doses of 0.3, 1 and 3mg/kg/h by 22, 54 and 64%, respectively. In addition, MP-124 at all doses significantly reduced the overall neurological deficits. Such ameliorative effects of MP-124 were observed in female as well as male monkeys. In the therapeutic time window (TTW) study, the neurological deficits and cerebral infarct volume were assessed at several time points after pMCAO or tMCAO. Treatment with MP-124 at 3 and 6h after MCAO significantly ameliorated not only the neurological deficits but also the infarct volume. MP-124 is thought to exhibit neuroprotective effects with a broad TTW regardless of sex in MCAO models. Such findings suggest that MP-124 may be beneficial for the treatment of acute ischemic stroke.

6-(4-Pyridyl)pyrimidin-4(3H)-ones as CNS penetrant glycogen synthase kinase-3β inhibitors.

The discovery of a series of 6-(4-pyridyl)pyrimidin-4(3H)-ones derived from a hit compound with low molecular weight and sufficient chemical space is reported. Transformation of substituents led to subnanomolar potent inhibitors with in vivo tau phoshorylation lowering activity.

Neuroprotective effects of a novel water-soluble poly(ADP-ribose) polymerase-1 inhibitor, MP-124, in in vitro and in vivo models of cerebral ischemia

Cerebral ischemia induces excessive activation of poly(ADP-ribose) polymerase-1 (PARP-1), leading to neuronal cell death and the development of post-ischemic dysfunction. Blockade of PARP-related signals during cerebral ischemia has become a focus of interest as a new therapeutic approach for acute stroke treatment. The purpose of the present study was to examine the pharmacological profiles of MP-124, a novel water-soluble PARP-1 inhibitor, and its neuroprotective effects on ischemic injury in vitro and in vivo. MP-124 demonstrated competitive inhibition of the PARP-1 activity of human recombinant PARP-1 enzyme (Ki=16.5nmol/L). In P388D(1) cells, MP-124 inhibited the LDH leakage induced by H(2)O(2) in a concentration-dependent manner. (IC(50)=20.8nmol/L). In rat primary cortical neurons, MP-124 also inhibited the NAD depletion and polymerized ADP-ribose formation induced by H(2)O(2) exposure. Moreover, we investigated the neuroprotective effects of MP-124 in rat permanent and transient stroke models. In the rat permanent middle cerebral artery occlusion (MCAO) model, MP-124 was administered intravenously for 24h from 5min after the onset of MCAO. MP-124 (1, 3 and 10mg/kg/h) significantly inhibited the cerebral infarction in a dose-dependent manner (18, 42 and 48%). In rat transient MCAO model, MP-124 was administered intravenously from 30min after the onset of MCAO. MP-124 (3 and 10mg/kg/h) significantly reduced the infarct volume (53% and 50%). The present findings suggest that MP-124 acts as a potent neuroprotective agent in focal ischemia and its actions can be attributed to a reduction in NAD depletion and PAR formation.

2-(2-Phenylmorpholin-4-yl)pyrimidin-4(3H)-ones; A new class of potent, selective and orally active glycogen synthase kinase-3β inhibitors

A series of 2-(2-phenylmorpholin-4-yl)pyrimidin-4(3H)-ones was synthesized and examined for their inhibitory activity against glycogen synthase kinase-3β (GSK-3β). We found 21, 29 and 30 to possess potent in vitro GSK-3β inhibitory activity with good in vitro PK profiles. 21 demonstrated significant decrease of tau phosphorylation after oral administration in mice and excellent PK profiles.

Feasibility study for functional test battery of SOD transgenic rat (H46R) and evaluation of edaravone, a free radical scavenger

We evaluated a battery of functional tests for investigating the effects of edaravone, a free radical scavenger, in SOD1 transgenic (H46R) rat model of amyotrophic lateral sclerosis. Edaravone (1.5 or 3.0mg/kg/h) or saline was administered intravenously to rats by continuous infusion (1h per day) for 2days, followed by a 2-day holiday. Lifetime and duration of illness were evaluated, and motor function was assessed using the hind-foot reflex test, landing foot-splay test, rota rod test and inclined plate test at a predetermined time point at which half of the control animals had died. Statistical comparison of motor functions of edaravone-treated and control SOD1 transgenic rats at an objectively determined time point was confirmed to be feasible. Edaravone-treated male rats showed significantly better performance in the landing foot-splay test. The present model seems suitable for evaluating motor function of H46R SOD1 transgenic rats, and be useful for examining the therapeutic potential of edaravone to treat amyotrophic lateral sclerosis.

Edaravone and its clinical development for amyotrophic lateral sclerosis

Abstract The etiology of amyotrophic lateral sclerosis (ALS) is unknown. Oxidative stress may be one of the major mechanisms involved. In vitro and in vivo data of edaravone suggest that it may possess broad free radical scavenging activity and protect neurons, glia, and vascular endothelial cells against oxidative stress. During the 1980s and 1990s, edaravone was developed for the treatment of acute ischemic stroke. In 2001, a clinical program in ALS was initiated and five clinical studies were conducted in Japan. Phase III studies were designed to rapidly evaluate (within a 24-week double-blind study window) functional changes using the Revised ALS Functional Rating Scale (ALSFRS-R) as a primary endpoint. The study populations were selected according to these considerations and were further refined as the studies proceeded. Although the first phase III study did not meet its primary endpoint, post-hoc analyses showed an apparent effect of edaravone, when additional patient inclusion criteria defined by ALSFRS-R score, pulmonary function, certainty of ALS diagnosis, and duration of disease were applied. This population was hypothesized not only to have retained broad functionality and normal respiratory function at study baseline but also to be likely to show measurable disease progression over 24 weeks. A second confirmatory phase III study applying these refinements in patient selection was prospectively designed and successfully documented a statistically significant difference between the edaravone and placebo groups in the ALSFRS-R primary endpoint. This paper describes and reviews data pertinent to the potential mechanism of action of edaravone, and reviews the development history of edaravone for the treatment of ALS.

Effects of alteplase, a thrombolytic agent, in a rat photothrombotic middle cerebral artery occlusion model.

In this study, we examined the effects of alteplase, a recombinant tissue-type plasminogen activator (t-PA), in a simple and reproducible rat middle cerebral artery (MCA) occlusion model induced by photoillumination with 12 mg/kg of rose bengal. A clinically equivalent dose of alteplase (3 mg/kg), which was administered just after thrombotic occlusion of the MCA, significantly reopened the thrombotic MCA occlusion in 16 of 23 animals (69.6%) when compared with vehicle-treated animals (8 of 22 animals, 36.4%). In addition, alteplase significantly reduced cerebral damage and improved neurological deficits. Although it has been reported that t-PA possesses neurotoxicity, the present findings suggest that alteplase was effective in a rat acute stroke model due to reopening of thrombotic MCA occlusion. This new model is very useful for investigating the efficacy of thrombolytic agents in stroke research, providing a condition similar to the clinical setting.

Discovery of novel 2-(3-phenylpiperazin-1-yl)-pyrimidin-4-ones as glycogen synthase kinase-3β inhibitors

We herein describe the results of further evolution of glycogen synthase kinase (GSK)-3β inhibitors from our promising compounds containing a 2-phenylmorpholine moiety. Transformation of the morpholine moiety into a piperazine moiety resulted in potent GSK-3β inhibitors. SAR studies focused on the phenyl moiety revealed that a 4-fluoro-2-methoxy group afforded potent inhibitory activity toward GSK-3β. Based on docking studies, new hydrogen bonding between the nitrogen atom of the piperazine moiety and the oxygen atom of the main chain of Gln185 has been indicated, which may contribute to increased activity compared with that of the corresponding phenylmorpholine analogues. Effect of the stereochemistry of the phenylpiperazine moiety is also discussed.

How is edaravone effective against acute ischemic stroke and amyotrophic lateral sclerosis

Edaravone is a low-molecular-weight antioxidant drug targeting peroxyl radicals among many types of reactive oxygen species. Because of its amphiphilicity, it scavenges both lipid- and water-soluble peroxyl radicals by donating an electron to the radical. Thus, it inhibits the oxidation of lipids by scavenging chain-initiating water-soluble peroxyl radicals and chain-carrying lipid peroxyl radicals. In 2001, it was approved in Japan as a drug to treat acute-phase cerebral infarction, and then in 2015 it was approved for amyotrophic lateral sclerosis (ALS). In 2017, the U.S. Food and Drug Administration also approved edaravone for treatment of patients with ALS. Its mechanism of action was inferred to be scavenging of peroxynitrite. In this review, we focus on the radical-scavenging characteristics of edaravone in comparison with some other antioxidants that have been studied in clinical trials, and we summarize its pharmacological action and clinical efficacy in patients with acute cerebral infarction and ALS.