Safety and efficacy of cladribine tablets in patients with relapsing-remitting multiple sclerosis: Results from the randomized extension trial of the CLARITY study

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 tablets : Oral immunotherapy of relapsing-remitting multiple sclerosis with short yearly treatment periods]

BACKGROUND

The selective modulation of lymphocyte numbers and function is an attractive concept in the treatment of relapsing-remitting multiple sclerosis (RMS).

OBJECTIVE

Cladribine tablets (Mavenclad®), an oral RMS medication with an innovative treatment concept, have been available since August 2017. This review article summarizes the currently available clinical study data on cladribine tablets and aspects of their use in clinical practice.

RESULTS

Cladribine tablets are administered during two treatment phases of 8-10 (two times 4-5) days with a 1-year interval. The drug selectively reduces the number of T and B lymphocytes, which are subsequently gradually reconstituted with divergent kinetics. A pronounced and sustained effect on the clinical and paraclinical MS disease activity is achieved with good tolerability and a favorable overall safety profile. After completing the two short treatment phases, a relevant proportion of the treated patients experience a prolonged treatment-free period with absence of relevant disease activity. Regular monitoring of lymphocyte counts and reliable contraception during the required time frames are the most important safety measures. There is no evidence of an increased risk of malignancies.

CONCLUSION

Cladribine tablets are an important addition to the therapeutic landscape in RMS. With patient-friendly short dosing periods and a favorable adverse event profile, cladribine tablets provide a sustained and strong reduction of MS disease activity. The primary target population for cladribine tablets is patients with relevant MS disease activity (highly active RMS) while on first-line treatment, e. g. with injectable disease-modifying drugs.

Effects of Postponing Treatment in the Second Year of Cladribine Administration: Clinical Trial Simulation Analysis of Absolute Lymphocyte Counts and Relapse Rate in Patients with Relapsing-Remitting Multiple Sclerosis

INTRODUCTION

Cladribine Tablets (MAVENCLAD^®) selectively reduce absolute lymphocyte counts (ALCs) in patients with multiple sclerosis. The recommended cumulative dose of Cladribine Tablets is 3.5 mg/kg over 4-5 days in months 1 and 2 of treatment years 1 and 2, followed by prolonged efficacy with no additional treatment. After the cladribine-induced reduction, ALCs recover to normal within each treatment year in most patients. Those patients with slow ALC recovery can develop Grade 3-4 lymphopenia, especially those patients with Grade ≥  2 lymphopenia at the start of year 2. Guidelines allowing treatment postponements during year 2 have been proposed for patients with a low ALC, subsequent to CLARITY, the pivotal clinical trial.

METHODS

A virtual population was generated using characteristics from CLARITY patients. A clinical trial simulation was performed to determine the impact of alternative treatment scenarios on ALC and relapse rate, by postponing treatment in year 2 to allow for longer ALC recovery time in patients who required it. Should a patient not recover to normal ALC (Grade 0) or Grade 1 lymphopenia within the period defined in the treatment algorithm, treatment in year 2 was suspended.

RESULTS

Results were similar across considered scenarios, which implemented different postponement durations. Specifically, ~  92% of virtual subjects did not require treatment postponement and <  1% discontinued due to Grade 2-4 lymphopenia at the end of the maximally permitted postponement. Less severe lymphopenia was observed during year 2 when a treatment algorithm was applied. The effect on relapse rate over 2 years was negligible.

CONCLUSIONS

Results support treatment guidelines to decrease the risk of severe lymphopenia following treatment with Cladribine Tablets, while preserving efficacy.

TRIAL REGISTRATION

CLARITY; ClinicalTrials.gov: NCT00213135.

Cladribine tablets added to IFN-β in active relapsing MS: The ONWARD study

Objective

To evaluate the safety and efficacy of cladribine tablets in patients still experiencing active relapsing MS despite interferon (IFN)-β treatment.

Methods

A 96-week phase II study, randomizing patients treated with IFN-β to cladribine tablets 3.5 mg/kg/IFN-β or placebo/IFN-β. Patients were to receive cladribine tablets 3.5 mg/kg/IFN-β or placebo/IFN-β in a 2:1 ratio (n = 172) with safety and exploratory efficacy outcomes being assessed.

Results

Adverse events (AEs) and serious AEs were similar across treatment groups, except lymphopenia. Fifty of 124 (40.3%) cladribine/IFN-β recipients vs 0% of placebo/IFN-β recipients reported lymphopenia as an AE, with grade 3/4 lymphopenia (laboratory lymphocyte count < 500 cells/mm³) experienced by 79/124 (63.7%) vs 1 (2.1%), respectively. Patients treated with cladribine tablets 3.5 mg/kg/IFN-β were 63% less likely to have a qualifying relapse than placebo/IFN-β recipients, and cladribine tablets 3.5 mg/kg/IFN-β reduced most MRI measures of disease activity.

Conclusions

In patients with active relapsing MS despite IFN-β treatment, cladribine tablets 3.5 mg/kg/IFN-β reduced relapses and MRI lesion activity over 96 weeks compared with placebo/IFN-β but led to an increased incidence of lymphopenia.

Classification of evidence

This study provides Class I evidence that for patients with active relapsing MS despite IFN-β treatment, cladribine tablets added to IFN-β reduced relapses and MRI lesion activity over 96 weeks and increased the incidence of lymphopenia.

Clinical trial registration

NCT00436826.

[New aspects of immunotherapy in multiple sclerosis]

The spectrum of therapeutic options for immunotherapy of multiple sclerosis is continuously broadening. After the approval of cladribine and ocrelizumab in Europe, two new drugs are now available with ocrelizumab being the first approved option for treatment of primary progressive multiple sclerosis; however, the increased use of highly effective therapies is accompanied by a rise in severe side effects. During recent months, special attention was paid to the new progressive multifocal leukoencephalopathy (PML) risk assessment in natalizumab-treated patients, cardiac side effects of fingolimod, cases of idiopathic thrombocytopenic purpura and listeria meningitis associated with alemtuzumab and cases of daclizumab-treated patients with liver failure or encephalitis. These case reports highlight the importance of careful monitoring of all patients treated with immunomodulatory therapies.

Induction or escalation therapy for patients with multiple sclerosis?

The concept of induction followed by a long-term maintenance treatment has attracted much attention for the treatment of multiple sclerosis over the 30 past years. It was first demonstrated by the combination of induction therapy with mitoxantrone (six-monthly courses) followed by maintenance therapy with an immunomodulatory treatment such as an interferon-β or glatiramer acetate. Long-term observational studies confirmed that this therapeutic regimen provides a rapid reduction in disease activity and sustained disease control up to at least five years in 60% of patients. A better treatment response was observed in patients with early signs of aggressive disease, as shown in randomised studies (using six-monthly 12mg/m² of mitoxantrone intravenously at a cumulative dose of 72mg/m², followed by an interferon-β) as well as in long-term observational studies. But the safety profile of mitoxantrone make it more particularly suitable for young patients with frequent early relapses with incomplete recovery and multiple gadolinium-enhancing T1 lesions or spinal cord lesions on magnetic resonance imaging. More recently approved, the second candidate for an induction strategy is alemtuzumab: phases II and III randomised studies showed the superiority of alemtuzumab 12mg per day given intravenously for only five days and repeated for 3 days one year later, compared with interferon-β three times a week. Like with mitoxantrone, results supported the concept of long-term benefit after a short induction rather than escalation, in a subset of patients with early very active MS, with a sustained control of the disease for up to 7 years in 60% of patients in the phase III extension studies and in a long-term observational study. On the contrary, when alemtuzumab was first studied later in the disease course, results were disappointing. However, the risk of developing manageable but potentially severe systemic autoimmune diseases within the years following the last course of alemtuzumab make it, like mitoxantrone, more suitable for patients with early aggressive MS. More recently, cladribine an oral immunosuppressant, showed interesting results in a phase III study extension suggesting its potential induction effect, since after two cycles of treatment (5 days repeated 1 month later) at one year of interval, the remained low up to 4 years of follow-up, in the absence of any new treatment. However, today other immunosuppressive drugs have proved to be strongly and rapidly efficacious in treating highly active MS patients but through a mechanism of continuous immunosuppression (i.e., natalizumab and ocrelizumab). Indeed, disease activity can reappear rapidly after stopping these drugs, sometimes associated with a rebound of the inflammatory process, which is the contrary of a mechanism of induction that is associated with a remnant effect. Taking into account advantages and disadvantages of the different DMDs, which enriched the today therapeutic arsenal for MS, we propose in this paper some algorithms summarizing our reflexion about using an escalation strategy or an induction strategy according to disease course and activity.

How much progress has there been in the second-line treatment of multiple sclerosis: A 2017 update

In 1993, the US Food and Drug Administration (FDA) approved the first drug specifically for treating multiple sclerosis (MS). More than two decades later, a dozen such treatments are now available. Of these, four are considered second-line treatments for use in escalation strategies and two new drugs are currently undergoing accreditation procedures. Soon, they will provide clinicians with a range of six effective disease-modifying treatments (DMTs) to thwart the inflammatory processes in MS patients with active disease. However, while such a large number of DMTs for MS can help to control early inflammation, any decisions to be made by clinicians have also been made substantially more complex. This complexity is increased by the lack of head-to-head studies comparing these second-line therapies and the benefit-risk profiles for each of these drugs, which are likely to vary among patients. Ultimately, good awareness of the benefits and, more important, the risks of each MS DMT is crucial for the effective management of inflammation in MS.

Cladribine tablets' potential role as a key example of selective immune reconstitution therapy in multiple sclerosis

Multiple sclerosis (MS) is one of the most important, disabling, and prevalent neurological disorders of young adults. It is a chronic inflammatory and neurodegenerative disease when autoreactive B and T cells have downstream effects that result in demyelination and neuronal loss. Anti-inflammatory disease-modifying therapies do have proven efficacy in delaying disease and disability progression in MS. While the progress in MS treatments has already improved the prognosis and quality of patients’ lives overall, there are some clear shortcomings and unmet needs in the current MS treatment landscape. The most promising means of MS treatment is selective immune reconstitution therapy (SIRT). This therapy is given in short-duration courses of immunosuppression, producing durable effects on the immune system and preventing nervous tissue loss. This review discusses the mechanisms of action and the data of clinical trials of cladribine tablets as an example of SIRT in MS. The clinical benefits of cladribine tablets in these studies include decreased relapse rate and disability progression with large reductions in lesion activity, and protection against brain volume loss. Whether all of these neurological findings are direct results of lymphocyte depletion, or if there are downstream effects on other, unknown, neurodegenerative processes are yet to be determined, but these clearly point to an interesting area of research.

Efficacy of Cladribine Tablets in high disease activity subgroups of patients with relapsing multiple sclerosis: A post hoc analysis of the CLARITY study

Background:

In the CLARITY (CLAdRIbine Tablets treating multiple sclerosis orallY) study, Cladribine Tablets significantly improved clinical and magnetic resonance imaging (MRI) outcomes (vs placebo) in patients with relapsing-remitting multiple sclerosis.

Objective:

Describe two clinically relevant definitions for patients with high disease activity (HDA) at baseline of the CLARITY study (utility verified in patients receiving placebo) and assess the treatment effects of Cladribine Tablets 3.5 mg/kg compared with the overall study population.

Methods:

Outcomes of patients randomised to Cladribine Tablets 3.5 mg/kg or placebo were analysed for subgroups using HDA definitions based on high relapse activity (HRA; patients with ⩾2 relapses during the year prior to study entry, whether on DMD treatment or not) or HRA plus disease activity on treatment (HRA + DAT; patients with ⩾2 relapses during the year prior to study entry, whether on DMD treatment or not, PLUS patients with ⩾1 relapse during the year prior to study entry while on therapy with other DMDs and ⩾1 T1 Gd+ or ⩾9 T2 lesions).

Results:

In the overall population, Cladribine Tablets 3.5 mg/kg reduced the risk of 6-month-confirmed Expanded Disability Status Scale (EDSS) worsening by 47% vs placebo. A risk reduction of 82% vs placebo was seen in both the HRA and HRA + DAT subgroups (vs 19% for non-HRA and 18% for non-HRA + DAT), indicating greater responsiveness to Cladribine Tablets 3.5 mg/kg in patients with HDA. There were consistent results for other efficacy endpoints. The safety profile in HDA patients was consistent with the overall CLARITY population.

Conclusion:

Patients with HDA showed clinical and MRI responses to Cladribine Tablets 3.5 mg/kg that were generally better than, or at least comparable with, the outcomes seen in the overall CLARITY population.

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.

Cladribine for multiple sclerosis

In the UK, there are twelve disease-modifying drugs licensed for various forms of multiple sclerosis (MS), of which three are oral therapies. An oral formulation of cladribine (Mavenclad - Merck Serono Europe Limited) was recently licensed by the European Medicines Agency (EMA) for the treatment of adult patients with highly active relapsing MS.^1,2 It is claimed to be "an innovatively simple approach" for treating this form of MS and "the only disease modifying therapy that can deliver and sustain 4 years of disease control with a maximum of 20 days oral treatment in the first 2 years."³ Here, we consider the evidence for its use in the treatment of highly active relapsing MS.

Long-term effects of cladribine tablets on MRI activity outcomes in patients with relapsing-remitting multiple sclerosis: the CLARITY Extension study

Background

The CLARITY and CLARITY Extension studies demonstrated that treatment of relapsing–remitting multiple sclerosis (RRMS) with cladribine tablets (CT) results in significant clinical improvements, compared with placebo. This paper presents the key magnetic resonance imaging (MRI) findings from the CLARITY Extension study.

Methods

Patients who received a cumulative dose of either CT 3.5 or 5.25 mg/kg in CLARITY were rerandomized to either placebo or CT 3.5 mg/kg in CLARITY Extension. Patients from the arm that received placebo in CLARITY were assigned to CT 3.5 mg/kg. MRI assessments were carried out when patients entered CLARITY Extension and after Weeks 24, 48, 72 and 96, and in a supplemental follow-up period.

Results

At CLARITY Extension baseline, patients who received placebo during CLARITY had more T1 gadolinium-enhanced (Gd+) lesions than patients who received CT during CLARITY. These patients, who were then exposed to cladribine 3.5 mg/kg during the extension, experienced a 90.4% relative reduction (median difference −0.33, 97.5% confidence interval −0.33–0.00; p < 0.001) in T1 Gd+ lesions at the end of the extension compared with the end of CLARITY. Overall, the majority of patients in each treatment group remained free from T1 Gd+ lesions throughout CLARITY Extension. However, a small proportion of patients who were treated with cladribine in CLARITY and received placebo in CLARITY Extension showed evidence of increased MRI activity, and this was associated with a prolonged treatment gap between CLARITY and CLARITY Extension.

Conclusion

A 2-year treatment with CT 3.5 mg/kg has a durable effect on MRI outcomes in the majority of patients, an effect that was sustained in patients who were not retreated in the subsequent 2 years after initial treatment.

ClinicalTrials.gov identifier: NCT00641537

Cladribine Tablets: A Review in Relapsing MS

Cladribine is a deoxyadenosine analogue prodrug that preferentially depletes lymphocytes, key cells underlying multiple sclerosis (MS) pathogenesis. Cladribine tablets (Mavenclad^®) represent the first short-course oral disease-modifying drug (DMD) for use in MS. The tablets, administered in two short courses 1 year apart, are indicated for the treatment of adults with highly active relapsing MS on the basis of data from pivotal clinical trials, including the phase 3 study CLARITY and its extension. A cumulative cladribine tablets dose of 3.5 mg/kg administered in this fashion in CLARITY reduced clinical relapse, disability progression and MRI-assessed disease activity and also improved some aspects of health-related quality of life (HR-QOL) versus placebo over 96 weeks in adults with relapsing-remitting MS (RRMS). Moreover, in the 96-week extension (plus 24 weeks' supplemental follow-up), no additional clinical benefit was gained from continuing versus discontinuing cladribine tablets after the first two annual courses of therapy, although MRI activity was more notable in a subset of cladribine tablet recipients who discontinued the drug. In post hoc analyses of CLARITY and/or a phase 2b trial, benefits of cladribine tablets were seen in patients with high disease activity (HDA) relapsing MS that were sometimes greater than in patients without HDA. Cladribine tablets have an acceptable tolerability profile and do not appear to be associated with an increased risk of overall infection or with an increased risk of malignancy (vs. matched reference populations). Active comparisons and longer-term follow-up would be beneficial, although current data indicate that for adults with highly active relapsing MS, cladribine tablets are an effective treatment option with the convenience of low-burden, short-course, oral administration.

Recent Advances in the Treatment for Multiple Sclerosis; Current New Drugs Specific for Multiple Sclerosis

Since the first approved parenteral drug for the treatment of multiple sclerosis (MS) in 1993 (interferon [IFN] beta, and later glatiramer acetate [GA]), today there are both parenteral and oral treatment options for MS. After IFN beta preparations, glatiramer acetate was developed; and, until the approval of natalizumab in 2006, those dominated the treatment of MS. Later on, among oral drug options, cladribine made a promising entry; however, due to safety concerns, it was withdrawn soon. Afterwards, with the understanding of the role of sphingosine-1 phosphate (S1P) receptors in the pathogenesis of MS, fingolimod was approved in 2010, which was followed by other oral agents such as teriflunomide and dimethyl fumarate. Recently newer IV treatment options such as alemtuzumab, rituximab and ocrelizumab have widened the treatment arena. Recently, after submitting new efficacy and safety data, cladribine was approved for MS by EMA, in 2017. Moreover, seven years after its rejection due to safety reasons, in August 2018 FDA accepted to re-evaluate the data of cladribine as a treatment option for relapsing remitting MS (RRMS). Another oral treatment option, Laquinimod, was not approved because it could not be shown to slow disability progression despite favourable effect in relapsing MS. Newer generation S1P receptor modulators are being investigated currently, and they are expected to come into the treatment arena soon. In this article, mechanisms of actions, clinical trial results, and side effects of the newer drugs used for MS, are reviewed. IFN beta and glatiramer acetate were not included since they have clinical experience nearing 30 years.

Cladribine to Treat Relapsing Forms of Multiple Sclerosis

Cladribine is a purine nucleoside analogue that selectively depletes peripheral lymphocytes without a major impact on cells of the innate immune system. An oral formulation of cladribine has been developed to be given as short courses over two annual cycles. Oral cladribine results in the peripheral depletion of lymphocytes that is gradual, occurring over several weeks, and is not associated with a cell lysis syndrome, has a greater impact on B cells than T cells, and is followed by gradual reconstitution of the peripheral lymphocyte counts over several months. Oral cladribine is effective in relapsing forms of multiple sclerosis. As a selective immune reconstitution therapy (SIRT), cladribine acts as a short-term immunosuppressant, relative to other maintenance immunosuppressive therapies that result in long-term immunosuppression. The main safety signal that has emerge relates primarily to herpes zoster infection, which was more common in patients with higher grades of lymphopenia, in particular grade 3 and 4 lymphopenia. Data from the oral cladribine extension trial and safety register, and reanalysis of the pivotal phase III trial has indicated that oral cladribine is unlikely to be associated with an increased short- to intermediate-term risk of malignancy.