Leukoencephalopathy following treatment with carmofur: a case report and review of the Japanese literature

Promyelinating drugs ameliorate oligodendrocyte pathologies in a mouse model of Krabbe disease

Krabbe disease (KD) is a rare inherited demyelinating disorder caused by a deficiency in the lysosomal enzyme galactosylceramide (GalCer) β-galactosidase. Most patients with KD exhibit fatal cerebral demyelination with apoptotic oligodendrocyte (OL) death and die before the age of 2-4 years. We have previously reported that primary OLs isolated from the brains of twitcher (twi) mice, an authentic mouse model of KD, have cell-autonomous developmental defects and undergo apoptotic death accompanied by abnormal accumulation of psychosine, an endogenous cytotoxic lyso-derivative of GalCer. In this study, we aimed to investigate the effects of the preclinical promyelinating drugs clemastine and Sob-AM2 on KD OL pathologies using primary OLs isolated from the brains of twi mice. Both agents specifically prevented the apoptotic death observed in twi OLs. However, while Sob-AM2 showed higher efficacy in restoring the impaired differentiation and maturation of twi OLs, clemastine more potently reduced the endogenous psychosine levels. These results present the first preclinical in vitro data, suggesting that clemastine and Sob-AM2 can act directly and distinctly on OLs in KD and ameliorate their cellular pathologies associated with myelin degeneration.

Exploration of potential inhibitors for SARS-CoV-2 Mpro considering its mutants via structure-based drug design, molecular docking, MD simulations, MM/PBSA, and DFT calculations

The main protease (Mpro) of SARS-COV-2 plays a vital role in the viral life cycle and pathogenicity. Due to its specific attributes, this 3-chymotrypsin like protease can be a reliable target for the drug design to combat COVID-19. Since the advent of COVID-19, Mpro has undergone many mutations. Here, the impact of 10 mutations based on their frequency and five more based on their proximity to the active site was investigated. For comparison purposes, the docking process was also performed against the Mpros of SARS-COV and MERS-COV. Four inhibitors with the highest docking score (11b, α-ketoamide 13b, Nelfinavir, and PF-07321332) were selected for the structure-based ligand design via fragment replacement, and around 2000 new compounds were thus obtained. After the screening of these new compounds, the pharmacokinetic properties of the best ones were predicted. In the last step, comparative molecular dynamics (MD) simulations, molecular mechanics Poisson-Boltzmann surface area calculations (MM/PBSA), and density functional theory calculations were performed. Among the 2000 newly designed compounds, three of them (NE1, NE2, and NE3), which were obtained by modifications of Nelfinavir, showed the highest affinity against all the Mpro targets. Together, NE1 compound is the best candidate for follow-up Mpro inhibition and drug development studies.

Versatile use of Carmofur: A comprehensive review of its chemistry and pharmacology

Carmofur, 1-hexylcarbamoyl-5-fluorouracil (HCFU) is an antineoplastic drug, which has been in clinics in Japan since 1981 for the treatment of colorectal cancer. Subsequently, it was also introduced in China, Korea, and Finland. Besides colorectal cancer, it has also shown antitumor activity in other cancers such as breast, head and neck, pancreatic, gastrointestinal, and solid brain tumors. A prodrug of 5-fluorouracil (5-FU), carmofur has shown better gastrointestinal stability and superior antiproliferative activity compared to its active counterpart 5-FU. Recently, carmofur has gained attention as an acid ceramidase inhibitor and as a potential lead compound against several noncancerous diseases such as coronavirus disease 2019, Krabbe disease, acute lung injury, Parkinson's disease, dementia, childhood ependymoma etc. Carmofur has also been reported to have antifungal, and antimicrobial properties. Nevertheless, no comprehensive review is available on this drug. Herein, we summarized the chemistry, pharmacokinetics, and pharmacology of carmofur based on the literature published between January 1976 and March 2022 as identified from PubMed and Google Scholar search engines.

Reduction in miR-219 expression underlies cellular pathogenesis of oligodendrocytes in a mouse model of Krabbe disease

Krabbe disease (KD), also known as globoid cell leukodystrophy, is an inherited demyelinating disease caused by the deficiency of lysosomal galactosylceramidase (GALC) activity. Most of the patients are characterized by early‐onset cerebral demyelination with apoptotic oligodendrocyte (OL) death and die before 2 years of age. However, the mechanisms of molecular pathogenesis in the developing OLs before death and the exact causes of white matter degeneration remain largely unknown. We have recently reported that OLs of twitcher mouse, an authentic mouse model of KD, exhibit developmental defects and endogenous accumulation of psychosine (galactosylsphingosine), a cytotoxic lyso‐derivative of galactosylceramide. Here, we show that attenuated expression of microRNA (miR)‐219, a critical regulator of OL differentiation and myelination, mediates cellular pathogenesis of KD OLs. Expression and functional activity of miR‐219 were repressed in developing twitcher mouse OLs. By using OL precursor cells (OPCs) isolated from the twitcher mouse brain, we show that exogenously supplemented miR‐219 effectively rescued their cell‐autonomous developmental defects and apoptotic death. miR‐219 also reduced endogenous accumulation of psychosine in twitcher OLs. Collectively, these results highlight the role of the reduced miR‐219 expression in KD pathogenesis and suggest that miR‐219 has therapeutic potential for treating KD OL pathologies.

Substrate Reduction Therapy for Krabbe Disease: Exploring the Repurposing of the Antibiotic D-Cycloserine

Krabbe disease is a lysosomal storage disease that is caused by a deficiency in galactosylceramidase. Infantile onset disease is the most common presentation, which includes progressive neurological deterioration with corresponding demyelination, development of globoid cells, astrocyte gliosis, etc. Hemopoietic stem cell transplantation (HSCT) is a disease modifying therapy, but this intervention is insufficient with many patients still experiencing developmental delays and progressive deterioration. Preclinical studies have used animal models, e.g., twitcher mice, to test different experimental therapies resulting in developments that have led to progressive improvements in the therapeutic impact. Some recent advances have been in the areas of gene therapy and substrate reduction therapy (SRT), as well as using these in combination with HSCT. Unfortunately, new experimental approaches have encountered obstacles which have impeded the translation of novel therapies to human patients. In an effort to identify a safe adjunct therapy, D-cycloserine was tested in preliminary studies in twitcher mice. When administered as a standalone therapy, D-cycloserine was shown to lengthen the lifespan of twitcher mice in a small but significant manner. D-Cycloserine is an FDA approved antibiotic used for drug resistant tuberculosis. It also acts as a partial agonist of the NMDA receptor, which has led to numerous human studies for a range of neuropsychiatric and neurological conditions. In addition, D-cycloserine may inhibit serine palmitoyltransferase (SPT), which catalyzes the rate-limiting step in sphingolipid production. The enantiomer, L-cycloserine, is a much more potent inhibitor of SPT than D-cycloserine. Previously, L-cycloserine was found to act as an effective SRT agent in twitcher mice as both a standalone therapy and as part of combination therapies. L-Cycloserine is not approved for human use, and its potent inhibitory properties may limit its ability to maintain a level of partial inactivation of SPT that is also safe. In theory, D-cycloserine would encompass a much broader dosage range to achieve a safe degree of partial inhibition of SPT, which increases the likelihood it could advance to human studies in patients with Krabbe disease. Furthermore, additional properties of D-cycloserine raise the possibility of other therapeutic mechanisms that could be exploited for the treatment of this disease.

Metabolism, Biochemical Actions, and Chemical Synthesis of Anticancer Nucleosides, Nucleotides, and Base Analogs

Nucleoside, nucleotide, and base analogs have been in the clinic for decades to treat both viral pathogens and neoplasms. More than 20% of patients on anticancer chemotherapy have been treated with one or more of these analogs. This review focuses on the chemical synthesis and biology of anticancer nucleoside, nucleotide, and base analogs that are FDA-approved and in clinical development since 2000. We highlight the cellular biology and clinical biology of analogs, drug resistance mechanisms, and compound specificity towards different cancer types. Furthermore, we explore analog syntheses as well as improved and scale-up syntheses. We conclude with a discussion on what might lie ahead for medicinal chemists, biologists, and physicians as they try to improve analog efficacy through prodrug strategies and drug combinations.

Akinetic mutism in bilateral necrotizing leucoencephalopathy after radiation and chemotherapy: electrophysiological and autopsy findings

In a patient with akinetic mutism, extensive circumscribed bilateral lesions in the precentral part of the centrum semiovale, due to delayed necrotizing leucoencephalopathy after combined intravenous polychemotherapy and radiation, were found at autopsy. CT and somatosensory evoked potentials were normal and a slow alpha rhythm was present, but there was a lack of EEG desynchronization. Akinetic mutism and the loss of desynchronization in this case are thought to result from interrupted thalamofrontal and extrathalamic reticulofrontal projections and the disconnection of the anterior limbic cortex.

Carmofur-induced organic mental disorders

Organic mental disorder was observed in a 29-year-old female in the prognostic period after the onset of carmofur-induced leukoencephalopathy. Symptoms such as euphoria, emotional lability and puerile attitude noted in the patient were diagnosed as organic personality syndrome according to the criteria defined in the DSM-III-R. It is referred to as a frontal lobe syndrome. Brain CT revealed a periventricular low density area in the frontal white matter and moderate dilatation of the lateral ventricles especially at the bilateral anterior horns. Consequently, carmofur-induced leukoencephalopathy may uncommonly result in organic personality syndrome in the residual state. It may be attributed to the structural damage to the frontal lobe.