Comparison of thein vitroandin vivometabolism of Cladribine (Leustatin, Movectro) in animals and human

CLADIN- CLADribine and INnate immune response in multiple sclerosis - A phase IV prospective study

Cladribine (Mavenclad®) is an oral treatment for relapsing remitting MS (RRMS), but its mechanism of action and its effects on innate immune responses in unknown. This study is a prospective Phase IV study of 41 patients with RRMS, and aims to investigate the mechanism of action of cladribine on peripheral monocytes, and its impact on the P2X7 receptor. There was a significant reduction in monocyte count in vivo at week 1 post cladribine administration, and the subset of cells being most impacted were the CD14lo CD16+ 'non-classical' monocytes. Of the 14 cytokines measured in serum, CCL2 levels increased at week 1. In vitro, cladrabine induced a reduction in P2X7R pore as well as channel activity. This study demonstrates a novel mechanism of action for cladribine. It calls for studying potential benefits of cladribine in progressive forms of MS and other neurodegenerative diseases where innate immune related inflammation is implicated in disease pathogenesis.

The impaired distribution of adenosine deaminase isoenzymes in multiple sclerosis plasma and cerebrospinal fluid

Background

Adenosine deaminase (ADA) via two isoenzymes, ADA1 and ADA2, regulates intra- and extracellular adenosine concentrations by converting it to inosine. In the central nervous system (CNS), adenosine modulates the processes of neuroinflammation and demyelination that together play a critical role in the pathophysiology of multiple sclerosis (MS). Except for their catalytic activities, ADA isoenzymes display extra-enzymatic properties acting as an adhesion molecule or a growth factor.

Aims

This study aimed to explore the distribution and activity of ADA1 and ADA2 in the plasma and the CSF of MS patients as well as in the human brain microvascular endothelial cells (HBMEC), human brain vascular pericytes and human astrocytes.

Methods and results

The enzyme assay following reverse phase-high performance liquid chromatography (HPLC) analysis was used to detect the ADA1 and ADA2 activities and revealed an increased ratio of ADA1 to ADA2 in both the plasma and the CSF of MS patients. Plasma ADA1 activity was significantly induced in MS, while ADA2 was decreased in the CSF, but significance was not reached. The brain astrocytes, pericytes and endothelial cells revealed on their surface the activity of ADA1, with its basal level being five times higher in the endothelial cells than in the astrocytes or the pericytes. In turn, ADA2 activity was only observed in pericytes and endothelial cells. Stimulation of the cells with pro-inflammatory cytokines TNFα/IL17 for 18 h decreased intracellular nucleotide levels measured by HPLC only in pericytes. The treatment with TNFα/IL17 did not modulate cell-surface ATP and AMP hydrolysis nor adenosine deamination in pericytes or astrocytes. Whereas in endothelial cells it downregulated AMP hydrolysis and ADA2 activity and upregulated the ADA1, which reflects the ADA isoenzyme pattern observed here in the CSF of MS patients.

Conclusion

In this study, we determined the impaired distribution of both ADA isoenzymes in the plasma and the CSF of patients with MS. The increased ADA1 to ADA2 ratio in the CSF and plasma may translate to unfavorable phenotype that triggers ADA1-mediated pro-inflammatory mechanisms and decreases ADA2-dependent neuroprotective and growth-promoting effects in MS.

The development and impact of cladribine on lymphoid and myeloid cells in multiple sclerosis

Cladribine is an approved selective immune reconstitution therapy for relapsing-remitting MS (RRMS). It was first developed and used to treat various forms of cancer, particularly leukemia via parenteral administration. The oral tablet version of cladribine was later developed to treat RRMS, an autoimmune disorder of the central nervous system (CNS) with periods of relapse and remission. Cladribine is found to selectively deplete adaptive immune cell types, and its role on innate immune cells is largely unknown. Among the lymphocyte populations and subtypes, the magnitude and kinetics of depletion by cladribine vary substantially. The current consensus on the selective cytotoxic effect of cladribine is that it is dependent on the deoxycytidine kinase (DCK) to 5'nucleotidase (5-NT) ratio of the immune cell type. Nonetheless, there are some discrepancies that cannot be fully elucidated by the DCK:5-NT ratio paradigm. This review aims to delineate the development and pharmacological properties of cladribine, and elucidate its influence on lymphoid and myeloid cells in MS.

Cladribine transfer into human milk: A case report

BACKGROUND

Cladribine is an antimetabolite used for the treatment of relapsing-remitting multiple sclerosis. At present, there are no data available on its use in breastfeeding mothers and its transfer in human milk.

OBJECTIVE

We present a case of a lactating mother who donated her milk samples to study the transfer of cladribine following a 20-mg oral dose.

METHODS

Analysis was done using liquid chromatography-mass spectrometry.

RESULTS

The relative infant dose calculated in this study was 3.06%.

CONCLUSION

This is the first case report suggesting the transfer of cladribine in human milk in measurable quantities. However, caution should be advised during lactation.

The Clinical Pharmacology of Cladribine Tablets for the Treatment of Relapsing Multiple Sclerosis

Cladribine Tablets (MAVENCLAD^®) are used to treat relapsing multiple sclerosis (MS). The recommended dose is 3.5 mg/kg, consisting of 2 annual courses, each comprising 2 treatment weeks 1 month apart. We reviewed the clinical pharmacology of Cladribine Tablets in patients with MS, including pharmacokinetic and pharmacometric data. Cladribine Tablets are rapidly absorbed, with a median time to reach maximum concentration (T_max) of 0.5 h (range 0.5–1.5 h) in fasted patients. When administered with food, absorption is delayed (median T_max 1.5 h, range 1–3 h), and maximum concentration (C_max) is reduced by 29% (based on geometric mean). Area under the concentration–time curve (AUC) is essentially unchanged. Oral bioavailability of cladribine is approximately 40%, pharmacokinetics are linear and time-independent, and volume of distribution is 480–490 L. Plasma protein binding is 20%, independent of cladribine plasma concentration. Cladribine is rapidly distributed to lymphocytes and retained (either as parent drug or its phosphorylated metabolites), resulting in approximately 30- to 40-fold intracellular accumulation versus extracellular concentrations as early as 1 h after cladribine exposure. Cytochrome P450-mediated biotransformation of cladribine is of minor importance. Cladribine elimination is equally dependent on renal and non-renal routes. In vitro studies indicate that cladribine efflux is minimally P-glycoprotein (P-gp)-related, and clinically relevant interactions with P-gp inhibitors are not expected. Cladribine distribution across membranes is primarily facilitated by equilibrative nucleoside transporter (ENT) 1, concentrative nucleoside transporter (CNT) 3 and breast cancer resistance protein (BCRP), and there is no evidence of any cladribine-related effect on heart rate, atrioventricular conduction or cardiac repolarisation (QTc interval prolongation). Cladribine Tablets are associated with targeted lymphocyte reduction and durable efficacy, with the exposure–effect relationship showing the recommended dose is appropriate in reducing relapse risk.

Emerging small-molecule treatments for multiple sclerosis: focus on B cells

Multiple sclerosis (MS) is a major cause of disability in young adults. Following an unknown trigger (or triggers), the immune system attacks the myelin sheath surrounding axons, leading to progressive nerve cell death. Antibodies and small-molecule drugs directed against B cells have demonstrated good efficacy in slowing progression of the disease. This review focusses on small-molecule drugs that can affect B-cell biology and may have utility in disease management. The risk genes for MS are examined from the drug target perspective. Existing small-molecule therapies for MS with B-cell actions together with new drugs in development are described. The potential for experimental molecules with B-cell effects is also considered. Small molecules can have diverse actions on B cells and be cytotoxic, anti-inflammatory and anti-viral. The current B cell-directed therapies often kill B-cell subsets, which can be effective but lead to side effects and toxicity. A deeper understanding of B-cell biology and the effect on MS disease should lead to new drugs with better selectivity, efficacy, and an improved safety profile. Small-molecule drugs, once the patent term has expired, provide a uniquely sustainable form of healthcare.

Cladribine: mechanisms and mysteries in multiple sclerosis

OBJECTIVES

The aims of this manuscript were to review the evidence for the efficacy and safety of cladribine in multiple sclerosis (MS) and to review the molecular and cellular mechanisms by which cladribine acts as a disease-modifying therapy in MS.

METHODS

This is a narrative review of the available clinical and preclinical data on the use of cladribine in MS.

RESULTS

Clinical trial data argue strongly that cladribine is a safe and effective therapy for relapsing MS and that it may also be beneficial in progressive MS. The pharmacology of cladribine explains how it is selectively toxic towards lymphocytes. Immunophenotyping studies show that cladribine depletes lymphocyte populations in vivo with a predilection for B cells. In vitro studies demonstrate that cladribine also exerts immunomodulatory influences over innate and adaptive immunity.

CONCLUSIONS

Cladribine is a safe and effective form of induction therapy for relapsing MS. Its mechanism of benefit is not fully understood but the most striking action is selective, long-lasting, depletion of B lymphocytes with a particular predilection for memory B cells. The in vivo relevance of its other immunomodulatory actions is unknown. The hypothesis that cladribine's action of benefit is to deplete memory B cells is important: if correct, it implies that selective targeting of this cell population and sparing of other lymphocytes could modify disease activity without predisposing to immunosuppression-related complications.

Cladribine treatment of multiple sclerosis is associated with depletion of memory B cells

Background

The mechanism of action of oral cladribine, recently licensed for relapsing multiple sclerosis, is unknown.

Objective

To determine whether cladribine depletes memory B cells consistent with our recent hypothesis that effective, disease-modifying treatments act by physical/functional depletion of memory B cells.

Methods

A cross-sectional study examined 40 people with multiple sclerosis at the end of the first cycle of alemtuzumab or injectable cladribine. The relative proportions and absolute numbers of peripheral blood B lymphocyte subsets were measured using flow cytometry. Cell-subtype expression of genes involved in cladribine metabolism was examined from data in public repositories.

Results

Cladribine markedly depleted class-switched and unswitched memory B cells to levels comparable with alemtuzumab, but without the associated initial lymphopenia. CD3⁺ T cell depletion was modest. The mRNA expression of metabolism genes varied between lymphocyte subsets. A high ratio of deoxycytidine kinase to group I cytosolic 5′ nucleotidase expression was present in B cells and was particularly high in mature, memory and notably germinal centre B cells, but not plasma cells.

Conclusions

Selective B cell cytotoxicity coupled with slow repopulation kinetics results in long-term, memory B cell depletion by cladribine. These may offer a new target, possibly with potential biomarker activity, for future drug development.

Electronic supplementary material

The online version of this article (10.1007/s00415-018-8830-y) contains supplementary material, which is available to authorized users.

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.