Cladribine tablets for the treatment of relapsing–remitting multiple sclerosis

Long-term management of multiple sclerosis patients treated with cladribine tablets beyond year 4

INTRODUCTION

Oral cladribine is a highly effective pulsed selective immune reconstitution therapy licensed for relapsing multiple sclerosis (RMS) since 2017. A full treatment course comprises two treatment cycles given 1 year apart, followed by two treatment-free years. The management of cladribine-treated patients beyond year 4 needs to be addressed as patients have now passed the initial 4 years since European Medical Agency approval.

AREAS COVERED

A panel of neurologists and a neuroradiologist experienced in MS treatment/monitoring evaluated clinical trial data and real-world evidence and proposed recommendations for the management of cladribine-treated patients beyond year 4.

EXPERT OPINION

Continuous monitoring of disease activity during the treatment-free period is important. Subsequent management depends on the presence or absence of inflammatory disease activity, determined in the absence of consistent guidelines via practice-driven neurological decision criteria. Persisting or newly occurring inflammatory disease activity is an indication for further treatment, i.e. either re-initiation of cladribine or switching to another highly effective disease-modifying therapy. The decision to retreat or switch should be based on clinical and radiological evaluation considering disease course, treatment history, and safety aspects. In the absence of disease activity, either retreatment can be offered, or the treatment-free period can be extended under structured monitoring.

Cladribine as a Potential Object of Nucleoside Transporter-Based Drug Interactions

Cladribine is a nucleoside analog that is phosphorylated in its target cells (B and T-lymphocytes) to its active triphosphate form (2-chlorodeoxyadenosine triphosphate). Cladribine tablets 10 mg (Mavenclad®), administered for up to 10 days per year in 2 consecutive years (3.5-mg/kg cumulative dose over 2 years), are used to treat patients with relapsing multiple sclerosis. Cladribine has been shown to be a substrate of various nucleoside transporters (NTs). Intestinal absorption and distribution of cladribine throughout the body appear to be essentially mediated by equilibrative NTs (ENTs) and concentrative NTs (CNTs), specifically by ENT1, ENT2, ENT4, CNT2 (low affinity), and CNT3. Other efficient transporters of cladribine are the ABC efflux transporters, specifically breast cancer resistance protein, which likely modulates the oral absorption and renal excretion of cladribine. A key transporter for the intracellular uptake of cladribine into B and T-lymphocytes is ENT1 with ancillary contributions of ENT2 and CNT2. Transporter-based drug interactions affecting absorption and target cellular uptake of a prodrug such as cladribine are likely to reduce systemic bioavailability and target cell exposure, thereby possibly hampering clinical efficacy. In order to manage optimized therapy, i.e., to ensure uncompromised target cell uptake to preserve the full therapeutic potential of cladribine, it is important that clinicians are aware of the existence of NT-inhibiting medicinal products, various lifestyle drugs, and food components. This article reviews the existing knowledge on inhibitors of NT, which may alter cladribine absorption, distribution, and uptake into target cells, thereby summarizing the existing knowledge on optimized methods of administration and concomitant drugs that should be avoided during cladribine treatment.

Review of Transporter Substrate, Inhibitor, and Inducer Characteristics of Cladribine

Cladribine is a nucleoside analog that is phosphorylated in its target cells (B- and T-lymphocytes) to its active adenosine triphosphate form (2-chlorodeoxyadenosine triphosphate). Cladribine tablets 10 mg (Mavenclad^®) administered for up to 10 days per year in 2 consecutive years (3.5-mg/kg cumulative dose over 2 years) are used to treat patients with relapsing multiple sclerosis. The ATP-binding cassette, solute carrier, and nucleoside transporter substrate, inhibitor, and inducer characteristics of cladribine are reviewed in this article. Available evidence suggests that the distribution of cladribine across biological membranes is facilitated by a number of uptake and efflux transporters. Among the key ATP-binding cassette efflux transporters, only breast cancer resistance protein has been shown to be an efficient transporter of cladribine, while P-glycoprotein does not transport cladribine well. Intestinal absorption, distribution throughout the body, and intracellular uptake of cladribine appear to be exclusively mediated by equilibrative and concentrative nucleoside transporters, specifically by ENT1, ENT2, ENT4, CNT2 (low affinity), and CNT3. Renal excretion of cladribine appears to be most likely driven by breast cancer resistance protein, ENT1, and P-glycoprotein. The latter may play a role despite its poor cladribine transport efficiency in view of the renal abundance of P-glycoprotein. There is no evidence that solute carrier uptake transporters such as organic anion transporting polypeptides, organic anion transporters, and organic cation transporters are involved in the transport of cladribine. Available in vitro studies examining the inhibitor characteristics of cladribine for a total of 13 major ATP-binding cassette, solute carrier, and CNT transporters indicate that in vivo inhibition of any of these transporters by cladribine is unlikely.

CLICK-MS and MASTER-2 Phase IV trial design: cladribine tablets in suboptimally controlled relapsing multiple sclerosis

Cladribine tablets 10 mg (3.5 mg/kg cumulative dose over 2 years) are approved for the treatment of relapsing forms of multiple sclerosis (MS), including relapsing-remitting MS and active secondary progressive MS. However, real-world data on cladribine tablets are limited. CLICK-MS and MASTER-2 are single arm, observational, 30-month, Phase IV studies in the US evaluating the effectiveness and safety of cladribine tablets 3.5 mg/kg in patients with relapsing-remitting MS or active secondary progressive MS who had suboptimal response to prior injectable (CLICK-MS), or infusion/oral (MASTER-2) disease-modifying therapy. The primary end point is 24-month annualized relapse rate. Key secondary end points include patient-reported outcomes on quality of life measures, treatment adherence and adverse events. Studies began in 2019 and are expected to be completed in 2023. Trial registration number • CLICK-MS: NCT03933215 (ClinicalTrials.gov) Full title; CLadribine tablets: observational evaluation of effectIveness and patient-reported outcomes in suboptimally Controlled patients previously taKing injectable disease-modifying drugs for relapsing forms of Multiple Sclerosis • MASTER-2: NCT03933202 (ClinicalTrials.gov) Full title; Cladribine tablets: observational evaluation of effectiveness and patient-reported outcomes in suboptiMAlly controlled patientS previously Taking oral or infusion disEase-modifying dRugs for relapsing forms of multiple sclerosis.

Cladribine tablets versus other disease-modifying oral drugs in achieving no evidence of disease activity (NEDA) in multiple sclerosis-A systematic review and network meta-analysis

INTRODUCTION

Assuming full control of the relapsing-remitting multiple sclerosis (RRMS) is the main target for practitioners. Disease control could be defined as no clinical relapse, absence of 3-month confirmed disability progression expressed on the Expanded Disability Status Scale (EDSS), as well as no disease activity on magnetic resonance imaging (MRI). NEDA-3 (no evidence of disease activity) is a composite endpoint used primarily in clinical trials, comprising these 3 measurements of disease activity. The aim of this study is to compare cladribine tablets (CT) with oral disease-modifying drugs (DMDs) - fingolimod (FTY), dimethyl fumarate (DMF), and teriflunomide (TERI) - with regard to NEDA-3 and its clinical (relapse and disability progression) and MRI (no new T1 Gd+ lesions or no new T2 lesions or no enlargement of existing lesions) components occurrence during a 24-month follow-up.

METHODS

In June 2018, a systematic review of MEDLINE, Embase and Cochrane database was performed. Due to the lack of head-to-head trials directly comparing cladribine tablets to oral drugs of interest, an indirect network meta-analysis (NMA) was applied, with placebo as a common comparator. NMA was performed with Bayesian approach and Markov chain Monte Carlo (MCMC) method for estimating posterior distributions. Additional data used in the analysis were taken from conference abstracts or post hoc analyses of pooled data from the clinical studies.

RESULTS

Six randomised clinical trials (RCTs) presenting NEDA, with active treatment compared to placebo, were included in the NMA: CLARITY (CT), FREEDOMS and FREEDOMS II (FTY), CONFIRM and DEFINE (DMF) and TEMSO (TERI). The rate of NEDA-3 was significantly higher in cladribine tablets vs DMF: OR (odds ratio)=1.76 (95% CrI [credible intervals]: 1.02-3.03) and TERI: OR=2.78 (95% CrI: 1.60-4.83), but not vs FTY. For the MRI NEDA results were as follows - cladribine tablets vs DMF: OR=1.87 (95% CrI: 1.18-2.97); cladribine tablets vs TERI: OR=6.59 (95% CrI: 4.32-10.09); cladribine tablets vs FTY: OR=1.58 (95% CrI: 1.10-2.29). The comparison of clinical NEDA did not reach significance vs either DMF or TERI and evaluation vs FTY was not possible because of lack of data.

CONCLUSIONS

Cladribine in the form of tablets was significantly more effective in achieving NEDA-3 than DMF and TERI, but there was no significant difference vs FTY. Cladribine tablets was more effective than all oral comparators considering the MRI NEDA. For clinical NEDA, the superiority vs DMF and vs TERI was not confirmed, and vs FTY evaluation was not possible.

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.

Immunological consequences of "immune reconstitution therapy" in multiple sclerosis: A systematic review

Immune reconstitution therapy (IRT) is an emerging concept for the treatment of multiple sclerosis (MS) that is given intermittently and can induce long-term remission of MS that is sustained in treatment-free periods. A systematic literature review was performed to identify and summarize current knowledge regarding the short- and long-term immunological consequences of different IRTs and CD20 depleting therapies on the cellular level in patients with MS. A total of 586 articles published between January 2010 and September 2019 were identified and screened; 44 studies met inclusion criteria for the review. All the treatments considered appeared to produce both qualitative and quantitative changes in the immune cell populations of patients with MS that resulted in a more anti-inflammatory immune profile. Autologous hematopoietic stem cell transplantation produced the longest-lasting and greatest effects on a wide range of immune cells. Many patients achieved prolonged depletion of the adaptive immune system when alemtuzumab and cladribine tablets were administered as short courses of therapy; however, a proportion of patients required retreatment to maintain these effects. Alemtuzumab may produce greater depletion of both CD4+ and CD8+ T cells than cladribine tablets, although both treatments similarly deplete B cells. Recovery of B cells before T cell recovery and hyperpopulation of B cells after alemtuzumab may contribute to secondary autoimmunity. Cladribine tablets had a greater effect on B cells than T cells, and no hyperpopulation of B cells was observed after treatment with cladribine tablets. Ocrelizumab and rituximab require regular repeated treatment every 6 months to maintain depletion of B and T cells. Effects of the drug treatments on the innate immune system were minor compared with those on the adaptive immune system. Additional characterization of the cellular changes occurring during IRT and CD20 depletion may lead to further improvement in the understanding of the pathogenesis of MS and the future development of therapies with even longer lasting effects. Although the treatments considered in this review improve quality of life and outcomes for patients with MS, a cure for this debilitating disease is not yet in sight.

Cladribine Induces ATF4 Mediated Apoptosis and Synergizes with SAHA in Diffuse Large B-Cell Lymphoma Cells

Cladribine is a purine nucleoside analog used to treat B-cell chronic lymphocytic leukemia and hairy cell leukemia, also functions as an inhibitor of DNA synthesis to block the repair of the damaged DNA. The therapeutic role of cladribine against diffuse large B-cell lymphoma cells (DLBCL) is still undefined. In the present study, we demonstrated that cladribine inhibited cell proliferation and induced G₁ phase arrest in human DLBCL cells. Furthermore, we showed that cladribine induced apoptosis by decreasing the expression of c-FLIP_L and increasing the expression of DR4 and the cleaved form of caspase8. Cladribine also upregulated the expression of Bax, and downregulated the expression of Mcl-1 and Bcl-2 in a dose-dependent manner. It also activated endoplasmic reticulum (ER) stress, and ATF4 expression was required for cladribine induced apoptosis. Also, we showed that suberoylanilide hydroxamic acid (SAHA) enhanced the pro-apoptotic role of cladribine. Collectively, cladribine activated extrinsic and intrinsic apoptotic signaling pathways via stimulating ER stress signaling pathway and eliciting synergistic effect with SAHA in DLBCL cells.

Effects of cladribine tablets on heart rate, atrio-ventricular conduction and cardiac repolarization in patients with relapsing multiple sclerosis

Aims

Cladribine tablets have shown significant efficacy for the treatment of relapsing multiple sclerosis, a chronic and debilitating immune‐mediated disorder. This study was conducted to examine acute and/or cumulative effects of cladribine tablets 10 mg (3.5 or 5.25 mg/kg cumulative dose over 2 years) on heart rate, AV conduction and cardiac repolarization in patients with relapsing–remitting multiple sclerosis (RRMS).

Methods

CLARITY was a 96‐week, double‐blind, placebo‐controlled, multicentre trial which evaluated the safety and efficacy of cladribine tablets 3.5 and 5.25 mg/kg body weight in patients with RRMS. A total of 135 patients were included in the ECG substudy, providing a total of 1534 post‐dose ECGs. ECG data were collected 15 minutes pre‐dose and between 0.5 and 3 hours post‐dose at pre‐study evaluation, study Day 1 and Weeks 5, 9, 13, 48 and 52.

Results

For cladribine tablets 3.5 mg/kg, the maximum change in placebo‐adjusted post‐dose QTcF vs. visit‐baseline (BL) was −0.42 ms (90% CI: −3.61–4.44) at Week 1 (acute effects), and 3.20 ms (90% CI: −0.08–6.33) for cladribine tablets 5.25 mg/kg. The greatest observed differences in post‐dose QTcF vs. study BL occurred at Week 48 for both the 3.5 and 5.25 mg/kg doses of cladribine tablets with 5.99 ms (90% CI: 0.53–11.44) and 8.74 ms (90% CI: 3.18–14.31), respectively. No significant changes were observed in T‐wave morphology in either treatment group.

Conclusions

Cladribine tablets 3.5 mg/kg (approved dose in Europe/other regions) did not confer clinically meaningful effects on heart rate, AV conduction and ventricular repolarization.

Effect of cladribine tablets on lymphocyte reduction and repopulation dynamics in patients with relapsing multiple sclerosis

BACKGROUND

Immune reconstitution therapies (IRT) for patients with multiple sclerosis are used for short, intermittent treatment periods to induce immune resetting and allow subsequent treatment-free periods. Cladribine tablets are postulated to be an IRT that causes selective and transient reductions in CD19⁺ B cells and T cells, followed by reconstitution of adaptive immune function.

OBJECTIVE

To characterize long-term lymphocyte count changes in pooled data from the 2-year CLARITY and subsequent 2-year CLARITY Extension studies, and the PREMIERE registry (Long-term CLARITY cohort).

METHODS

Data from patients randomized to placebo (n = 435) or cladribine tablets 10 mg (MAVENCLAD^®; 3.5 mg/kg cumulative dose over 2 years, referred to as cladribine tablets 3.5 mg/kg; n = 685) in CLARITY or CLARITY Extension, including time spent in the PREMIERE registry were pooled to provide long-term follow-up data. The study investigated absolute lymphocyte counts (ALC) up to 312 weeks and B and T cell subsets up to 240 weeks after the first dose, in patients receiving placebo or cladribine tablets 3.5 mg/kg administered as two short (4 or 5 days) weekly treatments at the start of months 1 and 2 in each treatment year, followed by no further active treatment.

RESULTS

Treatment with cladribine tablets 3.5 mg/kg resulted in selective reductions in B and T lymphocytes. Lymphocyte recovery began soon after treatment in each of years 1 and 2. Median ALC recovered to the normal range and CD19⁺ B cells recovered to threshold values by week 84, approximately 30 weeks after the last dose of cladribine tablets in year 2. Median CD4⁺ T cell counts recovered to threshold values by week 96 (approximately 43 weeks after the last dose of cladribine tablets in year 2). Median CD8⁺ cell counts never dropped below the threshold value.

CONCLUSION

These results show the dynamics of lymphocyte count changes following treatment with cladribine tablets 3.5 mg/kg. The immune cell repopulation results provide further evidence that cladribine tablets may represent a form of IRT.

Inhibition of histone deacetylase 7 reverses concentrative nucleoside transporter 2 repression in colorectal cancer by up-regulating histone acetylation state

BACKGROUND AND PURPOSE

The concentrative nucleoside transporter 2 (CNT2) mediates the uptake of both natural nucleosides and nucleoside-derived drugs. Therefore, it is important both physiologically and pharmacologically. However, CNT2 expression is significantly repressed in colorectal cancer (CRC). Here, we have elucidated the mechanism(s) underlying CNT2 repression in CRC.

EXPERIMENTAL APPROACH

Repression of CNT2 in tumour samples from patients with CRC was identified using Western blot and RT-qPCR. The histone acetylation state at the CNT2 promoter region was then evaluated with chromatin immunoprecipitation and trichostatin A (TSA) treatment. To find the key enzyme responsible for hypoacetylation at the CNT2 promoter region, siRNA knockdown and RT-qPCR were used. Effects of combining HDAC inhibitors and cladribine were studied in HCT15 and HT29 cells.

KEY RESULTS

Histone deacetylase 7 was significantly up-regulated in CRC, leading to histone hypoacetylation at the CNT2 promoter region, especially at sites H3K9Ac, H3K18Ac and H4Ac. This hypoacetylation condensed the chromatin structure and reduced CNT2 expression. All these effects were reversed by treatment with TSA, a histone deacetylase inhibitor. In HCT15 and HT29 cells, inhibition of histone deacetylase increased cell uptake and decreased IC₅₀ for cladribine.

CONCLUSIONS AND IMPLICATIONS

Histone hypoacetylation due to increased levels of histone deacetylase 7 results in CNT2 repression in CRC tumour tissue and could lead to decreased uptake of and consequent resistance to nucleoside anti-cancer agents. Such resistance could be overcome by combining inhibitors of histone deacetylase with the nucleoside anti-cancer agent.

Cladribine: Off-label disease modification for people with multiple sclerosis in resource-poor settings?

Background

A considerable number of people with multiple sclerosis (pwMS) live in low- and middle-income countries (LMIC), where lack of resource adversely affects access to effective disease-modifying treatment.

Objective

The objective of this commentary is to propose a useful cost-effective disease-modifying treatment option for pwMS in LMIC with potential high efficacy and high convenience to the pwMS and treating physician.

Viewpoint: We propose using generic 2-chloro-2’-deoxyadenosine (cladribine), a small molecule licensed for treatment of people with hairy cell leukaemia, as a solution of this significant equity imbalance. Cladribine has been shown in phase II and III trials to be a highly effective disease-modifying treatment for pwMS, and its adverse effect profile is comparable with any DMT currently licensed in high-income economies where an oral preparation has recently been licensed by the European Medicines Agency.

Conclusion

Our viewpoint takes into account experience we have gathered over the past three years in the use of generic cladribine to treat pwMS. Whilst here we focus on MS, there is significant potential for use of cladribine in other conditions that could benefit from its mechanism of action.

The efficacy of cladribine tablets in CIS patients retrospectively assigned the diagnosis of MS using modern criteria: Results from the ORACLE-MS study

Background

Multiple sclerosis (MS) diagnostic criteria have changed since the ORACLE-MS study was conducted; 223 of 616 patients (36.2%) would have met the diagnosis of MS vs clinically isolated syndrome (CIS) using the newer criteria.

Objective

The objective of this paper is to assess the effect of cladribine tablets in patients with a first clinical demyelinating attack fulfilling newer criteria (McDonald 2010) for MS vs CIS.

Methods

A post hoc analysis for subgroups of patients retrospectively classified as fulfilling or not fulfilling newer criteria at the first clinical demyelinating attack was conducted.

Results

Cladribine tablets 3.5 mg/kg (n = 68) reduced the risk of next attack or three-month confirmed Expanded Disability Status Scale (EDSS) worsening by 74% vs placebo (n = 72); p = 0.0009 in patients meeting newer criteria for MS at baseline. Cladribine tablets 5.25 mg/kg (n = 83) reduced the risk of next attack or three-month confirmed EDSS worsening by 37%, but nominal significance was not reached (p = 0.14). In patients who were still CIS after applying newer criteria, cladribine tablets 3.5 mg/kg (n = 138) reduced the risk of conversion to clinically definite multiple sclerosis (CDMS) by 63% vs placebo (n = 134); p = 0.0003. Cladribine tablets 5.25 mg/kg (n = 121) reduced the risk of conversion by 75% vs placebo (n = 134); p < 0.0001.

Conclusions

Regardless of the criteria used to define CIS or MS, 3.5 mg/kg cladribine tablets are effective in patients with a first clinical demyelinating attack.

ClinicalTrials.gov registration: The ORACLE-MS study (NCT00725985).

Pharmacological Approaches to the Management of Secondary Progressive Multiple Sclerosis

It is well recognised that the majority of the impact of multiple sclerosis (MS), both personal and societal, arises in the progressive phase where disability accumulates inexorably. As such, progressive MS (PMS) has been the target of pharmacological therapies for many years. However, there are no current licensed treatments for PMS. This stands in marked contrast to relapsing remitting MS (RRMS) where trials have resulted in numerous licensed therapies. PMS has proven to be a more difficult challenge compared to RRMS and this review focuses on secondary progressive MS (SPMS), where relapses occur before the onset of gradual, irreversible disability, and not primary progressive MS where disability accumulation occurs without prior relapses. Although there are similarities between the two forms, in both cases pinpointing when PMS starts is difficult in a condition in which disability can vary from day to day. There is also an overlap between the pathology of relapsing and progressive MS and this has contributed to the lack of well-defined outcomes, both surrogates and clinically relevant outcomes in PMS. In this review, we used the search term 'randomised controlled clinical drug trials in secondary progressive MS' in publications since 1988 together with recently completed trials where results were available. We found 34 trials involving 21 different molecules, of which 38% were successful in reaching their primary outcome. In general, the trials were well designed (e.g. double blind) with sample sizes ranging from 35 to 1949 subjects. The majority were parallel group, but there were also multi-arm and multidose trials as well as the more recent use of adaptive designs. The disability outcome most commonly used was the Expanded Disability Status Scale (EDSS) in all phases, but also magnetic resonance imaging (MRI)-measured brain atrophy has been utilised as a surrogate endpoint in phase II studies. The majority of the treatments tested in SPMS over the years were initially successful in RRMS. This has a number of implications in terms of targeting SPMS, but principally implies that the optimal strategy to target SPMS is to utilise the prodrome of relapses to initiate a therapy that will aim to both prevent progression and slow its accumulation. This approach is in agreement with the early targeting of MS but requires treatments that are both effective and safe if it is to be used before disability is a major problem. Recent successes will hopefully result in the first licensed therapy for PMS and enable us to test this approach.

Cladribine Exposure Results in a Sustained Modulation of the Cytokine Response in Human Peripheral Blood Mononuclear Cells

Background and Objectives

Cladribine is a cytotoxic drug which ameliorates the clinical course of relapsing-remitting multiple sclerosis. In addition to cytotoxicity, the mode of action may include immunomodulatory mechanisms. This in vitro study was designed to investigate cladribine’s effects on cell function after the removal of cladribine to distinguish cytotoxic versus immunomodulatory effects.

Methods

Cells were incubated in the absence or presence of cladribine (1×10^-8 M to 1×10^-5 M) for 72 h. Cladribine was removed from the cell culture and surviving peripheral blood mononuclear cells were cultured up to 58 days to determine the immunomodulatory effects of cladribine on cell function (e.g., proliferation and cytokine release).

Results

In the long-term, brief cladribine exposure did not impair the proliferation of surviving peripheral blood mononuclear cells. However, it induced an anti-inflammatory shift in the cytokine milieu with significantly enhanced release of IL-4 (Days 9 and 44, p<0.01; Day 58, p<0.05) and IL-5 (Day 9, p<0.01), resulting in an increased IL-4/INF-gamma ratio (Days 9 and 44, p<0.01; Day 58, p<0.05). Additionally, a trend towards an increased IL-10 production was observed. No changes were found in the production of IFN-gamma, TNF-alpha, IL-6, IL-8, IL-17A, IL-23 or NGF-beta.

Conclusions

In vitro cladribine exposure induces a sustained anti-inflammatory shift in the cytokine profile of surviving peripheral blood mononuclear cells. This immunomodulatory action might contribute to cladribine’s beneficial effects in the treatment of multiple sclerosis.

Mechanisms of action of ACTH in the management of relapsing forms of multiple sclerosis

Acute and subacute inflammation, the mechanisms by which demyelination and axonal loss occur in multiple sclerosis (MS), result from the migration of activated immune cells into the central nervous system parenchyma. The triggering antigen is unknown, but the process involves deregulated immune response of T and B lymphocytes, macrophages, and mediators with expansion of autoreactive T cells creating a shift in the balance of pro- and anti-inflammatory cytokines favoring inflammation. Ongoing disease activity and exacerbations early in the course of relapsing-remitting MS may prevent full remission and propagate future progressive disability. A key strategy of immune therapy is timely initiation of treatment to achieve remission, followed by maintenance of remission. In this context, treatment with high-dose methylprednisolone (MP) is currently recommended to induce a faster recovery from a clinical exacerbation that results from an acute inflammatory attack. Adrenocorticotropic hormone (ACTH or corticotropin) gel is an alternative for patients who do not respond to or do not tolerate corticosteroids. ACTH is a universal agonist in the melanocortin (MC) system and, as such, among other functions, stimulates the adrenal cortex to produce cortisol. MCs are a family of peptides that includes ACTH and other MC peptides. This system has five classes of receptors, all of which show a strong affinity for ACTH, suggesting a more complex and dynamic mechanism than only inducing endogenous corticosteroid production. ACTH and MCs regulate processes relevant to MS, including anti-inflammatory and immunomodulatory functions involving lymphocytes, macrophages, the sympathetic nervous system involved in inflammatory processes, and reduction of pro-inflammatory cytokines. The clinical implications of the mechanistic differences between corticosteroid and ACTH gel treatment remain to be elucidated. Recent data show that patients experiencing an acute exacerbation, who previously had suboptimal response to or were unable to tolerate MP treatment, showed positive clinical outcomes with fewer adverse events with ACTH gel.