Cladribine: Difference between revisions

{{Short description|Pharmaceutical drug}}

{{Use dmy dates|date=August 2024}}

{{cs1 config |name-list-style=vanc |display-authors=6}}

{{Infobox drug

| Watchedfields = changed

| verifiedrevid = 460040776

| IUPAC_name = 5-(6-Amino-2-chloro-purin-9-yl)-2-(hydroxymethyl)oxolan-3-ol

| alt =

| tradename = Leustatin, Mavenclad, others<ref name="drugs.comINT">{{cite web | title=Cladribine | website=Drugs.com | date=28 February 2020 | url=https://www.drugs.com/international/cladribine.html | access-date=4 March 2020}}</ref>

| synonyms = 2-Chlorodeoxyadenosine; 2-Chloro-2'-deoxyadenosine; 2-CdA

| DailyMedID = Cladribine

| pregnancy_AU = D

| routes_of_administration = [[Intravenous]], [[Subcutaneous injection|subcutaneous]] (liquid), [[by mouth]] (tablet)

| ATC_prefix = L01

| ATC_suffix = BB04

| ATC_supplemental = ([[parenteral]])<br />{{ATC|L04|AA40}} ([[mouth|oral]] for [[multiple sclerosis]])

| legal_AU = S4

| legal_CA = Rx-only

| legal_CA_comment = <ref>{{cite web | title= Neurological therapies | website=[[Health Canada]] | date=9 May 2018 | url=https://www.canada.ca/en/services/health/drug-health-products/drug-medical-device-highlights-2017/approved-drugs/neurological-therapies.html | access-date=13 April 2024}}</ref>

| legal_UK = POM

| legal_EU = Rx-only

| legal_EU_comment = <ref>{{cite web | title=Mavenclad EPAR | website=European Medicines Agency (EMA) | date=22 August 2017 | url=https://www.ema.europa.eu/en/medicines/human/EPAR/mavenclad | access-date=26 August 2024}}</ref>

| legal_status =

| bioavailability = 100% ([[Intravenous|i.v.]]);

37 to 51% ([[Mouth|orally]])<ref>{{cite journal | vauthors = Liliemark J | title = The clinical pharmacokinetics of cladribine | journal = Clinical Pharmacokinetics | volume = 32 | issue = 2 | pages = 120–131 | date = February 1997 | pmid = 9068927 | doi = 10.2165/00003088-199732020-00003 | s2cid = 32926069 }}</ref>

| protein_bound = 25% (range 5-50%);<ref name = TGA>{{cite web|title=PRODUCT INFORMATION LITAK© 2 mg/mL solution for injection|date=10 May 2010|access-date=27 November 2014|location=St Leonards, Australia|publisher=Orphan Australia Pty. Ltd|work=TGA eBusiness Services|url=https://www.ebs.tga.gov.au/ebs/picmi/picmirepository.nsf/pdf?OpenAgent&id=CP-2010-PI-02734-3|format=PDF}}</ref> up to 20% (orally) <ref name="Giovannoni Neurotherapeutics">{{cite journal | vauthors = Giovannoni G | title = Cladribine to Treat Relapsing Forms of Multiple Sclerosis | journal = Neurotherapeutics | volume = 14 | issue = 4 | pages = 874–887 | date = October 2017 | pmid = 29168160 | pmc = 5722776 | doi = 10.1007/s13311-017-0573-4 }}</ref>

| metabolism = Mostly via [[intracellular]] [[kinase]]s; 15-18% is excreted unchanged.<ref name = TGA/>

Intravenous and subcutaneous bolus injection: 15-18% is excreted unchanged

After oral administration, 25% (±21%) of dose is excreted unchanged in urine and 3.8% as a metabolite.<ref name="Giovannoni Neurotherapeutics" />

| elimination_half-life = Approximately 10 hours after both intravenous infusion and subcutaneous bolus injection ranging from 5.6 to 7.6 hours<ref name = TGA/> and 18.4 to 19.7 hours after oral administration, indicative of different elimination phases.

| excretion = Urinary<ref name = TGA/>

| IUPHAR_ligand = 4799

| CAS_number_Ref = {{cascite|correct|??}}

| C=10 | H=12 | Cl=1 | N=5 | O=3

|drug_name=|caption=|type=|pregnancy_category=|licence_US=}}

'''Cladribine''', sold under the brand name '''Leustatin''', among others, is a medication used to treat [[hairy cell leukemia]] (leukemic reticuloendotheliosis) and [[B-cell chronic lymphocytic leukemia]].<ref name=EMA>{{cite journal|title=European Medicines Agency - - Litak|website=www.ema.europa.eu|date=17 September 2018|url=http://www.ema.europa.eu/ema/index.jsp?curl=pages/medicines/human/medicines/000504/human_med_000888.jsp&mid=WC0b01ac058001d124|access-date=1 July 2024|archive-date=3 August 2018|archive-url=https://web.archive.org/web/20180803074436/http://www.ema.europa.eu/ema/index.jsp?curl=pages/medicines/human/medicines/000504/human_med_000888.jsp&mid=WC0b01ac058001d124|url-status=dead}}</ref><ref name=EMC>{{cite journal|title=Leustat Injection. - Summary of Product Characteristics (SPC) - (eMC)|website=www.medicines.org.uk|url=http://www.medicines.org.uk/emc/medicine/6737|access-date=19 August 2016|archive-date=3 October 2017|archive-url=https://web.archive.org/web/20171003075055/http://www.medicines.org.uk/emc/medicine/6737|url-status=dead}}</ref> Cladribine, sold under the brand name '''Mavenclad''', is used for the treatment of adults with highly active forms of [[relapsing-remitting multiple sclerosis]].<ref name="EMA_2021">{{cite web |title=Mavenclad EU SmPC | date = February 2021 |url=https://www.ema.europa.eu/en/documents/product-information/mavenclad-epar-product-information_en.pdf |website=European Medicines Agency }}</ref>

Cladribine is a purine analogue that selectively targets and suppresses [[lymphocytes]] implicated in the underlying pathogenesis of [[multiple sclerosis]] and B-cell leukaemia.<ref name="Leist and Weissert">{{cite journal | vauthors = Leist TP, Weissert R | title = Cladribine: mode of action and implications for treatment of multiple sclerosis | journal = Clinical Neuropharmacology | volume = 34 | issue = 1 | pages = 28–35 | date = 2011 | pmid = 21242742 | doi = 10.1097/WNF.0b013e318204cd90 | ref = Leist and Weissert | s2cid = 43201228 }}</ref><ref name="Giovannoni Neurotherapeutics" /><ref name="pmid24652320">{{cite journal | vauthors = Jain P, Pemmaraju N, Ravandi F | title = Update on the biology and treatment options for hairy cell leukemia | journal = Current Treatment Options in Oncology | volume = 15 | issue = 2 | pages = 187–209 | date = June 2014 | pmid = 24652320 | pmc = 4198068 | doi = 10.1007/s11864-014-0285-5 }}</ref> Chemically, it mimics the [[nucleoside]] [[deoxyadenosine]]. However, unlike deoxyadenosine, it is relatively resistant to breakdown by the enzyme [[adenosine deaminase]], which causes it to accumulate in targeted cells and interfere with the cell's ability to process DNA.<ref name="Giovannoni Neurotherapeutics" /> Cladribine is taken up by cells via transporter proteins. Once inside a cell, cladribine undergoes phosphorylation by the enzyme [[deoxycytidine kinase]] (DCK) to produce mononucleotide 2-chlorodeoxyadenosine 5’monophosphate (2-CdAMP), which is subsequently phosphorylated to the triphosphorylated active compound 2-chlorodeoxyadenosine 5’triphosphate (2-CdATP). Activated cladribine is incorporated into cellular DNA, which triggers [[apoptosis]]. Accumulation of cladribine into cells is dependent on the ratio of DCK and [[5'-nucleotidase]] (5’-NT), which breaks down and inactivates the compound. This ratio differs between cell types, with high levels in T and B lymphocytes, resulting in selective targeting of these cells. In contrast, DCK:5'NT is relatively low in other cell types, thus sparing numerous non-haematological cells.<ref name="Leist and Weissert"/><ref name="Giovannoni Neurotherapeutics" />

It is on the [[WHO Model List of Essential Medicines|World Health Organization's List of Essential Medicines]].<ref name="WHO23rd">{{cite book | vauthors = ((World Health Organization)) | title = The selection and use of essential medicines 2023: web annex A: World Health Organization model list of essential medicines: 23rd list (2023) | year = 2023 | hdl = 10665/371090 | author-link = World Health Organization | publisher = World Health Organization | location = Geneva | id = WHO/MHP/HPS/EML/2023.02 | hdl-access=free }}</ref>

==Medical uses==

Cladribine is used as a first- and second-line treatment for symptomatic hairy cell leukemia and for B-cell chronic lymphocytic leukaemia, and is administered by intravenous or subcutaneous infusion.<ref name=EMC/><ref name=Label>{{cite web | title=Cladribine- cladribine injection | website=DailyMed | date=31 December 2019 | url=https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a2592a9b-bca6-4a5a-89c2-855a0634d5fe | access-date=4 March 2020}}</ref> Some investigators have used the parenteral formulation orally to treat patients with hairy cell leukemia. About 37–51% of oral cladribine is bioavailable orally.<ref name="Giovannoni Neurotherapeutics" /> It is used, often in combination with other cytotoxic agents, to treat various kinds of [[histiocytosis]], including [[Erdheim–Chester disease]]<ref>{{cite web | work = Histiocytosis Association | url = http://www.histio.org/page.aspx?pid=405#.V1BDvuTaHqk | title = Erdheim-Chester Disease | archive-url = https://web.archive.org/web/20190606140032/https://www.histio.org/page.aspx?pid=405#.V1BDvuTaHqk | archive-date= 6 June 2019 }}</ref> and [[Langerhans cell histiocytosis]].<ref>{{cite journal | vauthors = Aricò M | title = Langerhans cell histiocytosis in children: from the bench to bedside for an updated therapy | journal = British Journal of Haematology | volume = 173 | issue = 5 | pages = 663–670 | date = June 2016 | pmid = 26913480 | doi = 10.1111/bjh.13955 | quote = The combination of cytarabine and cladribine is the current standard for second-line therapy of refractory cases with vital organ dysfunction. | doi-access = free }}</ref>

Following EMA approval of cladribine tablets for the treatment of adult patients with highly active relapsing-remitting multiple sclerosis in 2017, as of July 2020, cladribine tablets have gained marketing authorisation in over 75 countries.<ref name="Rammohan 2020">{{cite journal | vauthors = Rammohan K, Coyle PK, Sylvester E, Galazka A, Dangond F, Grosso M, Leist TP | title = The Development of Cladribine Tablets for the Treatment of Multiple Sclerosis: A Comprehensive Review | journal = Drugs | volume = 80 | issue = 18 | pages = 1901–1928 | date = December 2020 | pmid = 33247831 | pmc = 7708385 | doi = 10.1007/s40265-020-01422-9 | ref = Rammohan 2020 }}</ref> In 2019, cladribine tablets were approved by the FDA for the treatment of relapsing forms of multiple sclerosis, to include [[Multiple sclerosis#Types and variants|relapsing-remitting disease and active secondary progressive]] disease, in adult patients who have had an inadequate response to, or are unable to tolerate, an alternate drug indicated for the treatment of multiple sclerosis.<ref name="Rammohan 2020"/><ref name="pmid32256946">{{cite journal | vauthors = Jamroz-Wiśniewska A, Bełtowski J, Wójcicka G, Bartosik-Psujek H, Rejdak K | title = Cladribine Treatment Improved Homocysteine Metabolism and Increased Total Serum Antioxidant Activity in Secondary Progressive Multiple Sclerosis Patients | journal = Oxidative Medicine and Cellular Longevity | volume = 2020 | issue = | pages = 1654754 | date = 2020 | pmid = 32256946 | pmc = 7103043 | doi = 10.1155/2020/1654754 | doi-access = free }}</ref>

Cladribine may cause foetal harm when administered to a pregnant woman and is listed by the FDA as [[US pregnancy category B|pregnancy category D]]; safety and efficacy in children has not been established.<ref name=Label/>

==Mechanism of action==

As a purine analogue, cladribine is taken up into rapidly proliferating cells, including B and T lymphocytes, to be incorporated into DNA synthesis. Chemically, it mimics nucleoside adenosine; however, unlike adenosine, cladribine has a chlorine molecule at position 2, which renders it partially resistant to breakdown by adenosine deaminase. This causes it to accumulate in cells and interfere with the targeted cell's ability to process DNA.<ref name="Giovannoni Neurotherapeutics" /><ref name="Leist and Weissert"/>

Cladribine is taken up by specific nucleoside transporter proteins. Once inside a cell, cladribine undergoes phosphorylation by the enzyme deoxycytidine kinase (DCK) to produce mononucleotide 2-chlorodeoxyadenosine 5’monophosphate (2-CdAMP), which is subsequently phosphorylated to the triphosphorylated active compound, 2-chlorodeoxyadenosine 5’triphosphate (2-CdATP).<ref name="Leist and Weissert"/><ref name="Giovannoni Neurotherapeutics" />

Activated cladribine is incorporated into the DNA synthesis pathway, where it disrupts DNA repair and synthesis, resulting in an accumulation of DNA strand breaks<ref name="Leist and Weissert"/><ref name="Giovannoni Neurotherapeutics" /><ref name="Johnston 2011">{{cite journal | vauthors = Johnston JB | title = Mechanism of action of pentostatin and cladribine in hairy cell leukemia | journal = Leukemia & Lymphoma | volume = 52 | pages = 43–45 | date = June 2011 | issue = Suppl 2 | pmid = 21463108 | doi = 10.3109/10428194.2011.570394 | ref = Johnston 2011 | s2cid = 207508023 }}</ref> This is followed by the activation of transcription factor [[p53]], the release of [[cytochrome c]] from mitochondria and eventual programmed cell death (apoptosis).<ref name="Johnston 2011" /> This process occurs over approximately 2 months, with a peak level of cell depletion 4–8 weeks after treatment.<ref>{{cite journal | vauthors = Beutler E, Piro LD, Saven A, Kay AC, McMillan R, Longmire R, Carrera CJ, Morin P, Carson DA | display-authors = 6 | title = 2-Chlorodeoxyadenosine (2-CdA): A Potent Chemotherapeutic and Immunosuppressive Nucleoside | journal = Leukemia & Lymphoma | volume = 5 | issue = 1 | pages = 1–8 | date = 1991 | pmid = 27463204 | doi = 10.3109/10428199109068099 }}</ref>

Another family of enzymes, the 5'-nucleotidase (5'-NT) family, is also capable of dephosphorylating cladribine, making it inactive. The most important subtypes of this group appear to be cytosolic 5'-NT, c-5NCT1A and c-NT1B, which are cytosolically active and specific for purine analogues.<ref name="ReferenceB"/>

Accumulation of cladribine into cells is dependent on the ratio of DCK and 5'-NT. This ratio differs between cell types, with high levels in T and B lymphocytes, making them particularly susceptible to cell death. The cells with the highest ratios are B cells, especially germinal centre and naïve B cells. This helps to explain which B cells are more vulnerable to cladribine-mediated apoptosis. DCK is the rate-limiting enzyme for conversion of the cladribine prodrug into its active triphosphate form, leading to the selective depletion of dividing and non-dividing T and B lymphocytes. In contrast, the DCK:5'-NT ratio is relatively low in other cell types, thus sparing numerous non-hematologic cells.<ref name="Leist and Weissert"/><ref name="Giovannoni Neurotherapeutics" /><ref name="ReferenceB">{{cite journal | vauthors = Ceronie B, Jacobs BM, Baker D, Dubuisson N, Mao Z, Ammoscato F, Lock H, Longhurst HJ, Giovannoni G, Schmierer K | display-authors = 6 | title = Cladribine treatment of multiple sclerosis is associated with depletion of memory B cells | journal = Journal of Neurology | volume = 265 | issue = 5 | pages = 1199–1209 | date = May 2018 | pmid = 29550884 | pmc = 5937883 | doi = 10.1007/s00415-018-8830-y }}</ref>

In multiple sclerosis, cladribine's effectiveness may be due to depletion of B cells, in particular memory B cells.<ref>{{cite journal | vauthors = Baker D, Marta M, Pryce G, Giovannoni G, Schmierer K | title = Memory B Cells are Major Targets for Effective Immunotherapy in Relapsing Multiple Sclerosis | journal = eBioMedicine | volume = 16 | pages = 41–50 | date = February 2017 | pmid = 28161400 | pmc = 5474520 | doi = 10.1016/j.ebiom.2017.01.042 }}</ref> In the pivotal phase 3 clinical trial of oral cladribine in multiple sclerosis, CLARITY, cladribine selectively depleted 80% of peripheral B cells, compared to only 40–45% of CD4+ T cells and 15‒30% CD8+ T cells.<ref>{{cite journal | vauthors = Baker D, Herrod SS, Alvarez-Gonzalez C, Zalewski L, Albor C, Schmierer K | title = Both cladribine and alemtuzumab may effect MS via B-cell depletion | journal = Neurology | volume = 4 | issue = 4 | pages = e360 | date = July 2017 | pmid = 28626781 | pmc = 5459792 | doi = 10.1212/NXI.0000000000000360 }}</ref> More recently, cladribine has been shown to induce long term, selective suppression of certain subtypes of B cells, especially memory B cells.<ref name="ReferenceB"/>

Although cladribine is selective for B cells, the long-term suppression of memory B cells, which may contribute to its effect in multiple sclerosis, is not explained by gene or protein expression. Instead, cladribine appears to deplete the entire B cell department, but while naïve B cells rapidly move from lymphoid organs, the memory B cell pool repopulates slowly from the bone marrow. Both hairy cell leukemia and B-cell chronic lymphocytic leukaemia are types of B cell blood cancers.

==History in hairy cell leukemia==

[[Ernest Beutler]] and [[Dennis A. Carson]] had studied [[adenosine deaminase deficiency]] and recognised that because the lack of adenosine deaminase led to the destruction of B cell lymphocytes, a drug designed to inhibit adenosine deaminase might be useful in lymphomas. Carson then synthesised cladribine, and through clinical research at Scripps starting in the 1980s, Beutler tested it as intravenous infusion and found it was especially useful to treat hairy cell leukemia. No pharmaceutical companies were interested in selling the drug because hairy cell leukemia was an [[orphan disease]], so Beutler's lab synthesised and packaged it and supplied it to the hospital pharmacy; the laboratory also developed a test to monitor blood levels. This was the first treatment that led to prolonged remission of hairy cell leukemia, which was previously untreatable.<ref name=NASbeutler>{{cite web | vauthors = Lichtman MA | url = http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/beutler-ernest.pdf | title = Biographical Memoir: Ernest Beutler 1928–2008 | work = National Academy of Sciences| date = 2012 }}</ref>{{rp|14–15}}

In February 1991, Scripps began a collaboration with [[Johnson & Johnson]] to bring intravenous cladribine to market, and by December of that year, Johnson & Johnson had filed a [[new drug application]]; cladribine was approved by the FDA in 1993 for hairy cell leukemia as an [[orphan drug]],<ref name=Pink1993>{{cite journal | vauthors = Staff | journal = The Pink Sheet | date = 8 March 1993 | url = https://pink.pharmamedtechbi.com/PS022259/ORTHO-BIOTECHs-LEUSTATIN-FOR-HAIRY-CELL-LEUKEMIA | title = Ortho Biotech's Leustatin For Hairy Cell Leukemia | archive-url = https://web.archive.org/web/20171003030348/https://pink.pharmamedtechbi.com/PS022259/ORTHO-BIOTECHs-LEUSTATIN-FOR-HAIRY-CELL-LEUKEMIA | archive-date= 3 October 2017 }}</ref> and was approved in Europe later that year.<ref name=EMAsciLitak>{{cite web | work = Europeans Medicines Agency | date = 2004 | url = http://www.ema.europa.eu/docs/en_GB/document_library/EPAR_-_Scientific_Discussion/human/000504/WC500041660.pdf | title = Litak EMA package: Scientific Discussion | access-date = 21 August 2016 | archive-date = 24 September 2015 | archive-url = https://web.archive.org/web/20150924012012/http://www.ema.europa.eu/docs/en_GB/document_library/EPAR_-_Scientific_Discussion/human/000504/WC500041660.pdf | url-status = dead }}</ref>{{rp|2}}

The subcutaneous formulation was developed in Switzerland in the early 1990s and it was commercialised by Lipomed GmbH in the 2000s.<ref name=EMAsciLitak/>{{rp|2}}<ref>{{cite web | work = Europeans Medicines Agency | date = 2004 | url = http://www.ema.europa.eu/docs/en_GB/document_library/EPAR_-_Procedural_steps_taken_before_authorisation/human/000504/WC500041661.pdf | title = Litak: Background Information on the Procedure | access-date = 21 August 2016 | archive-date = 21 August 2016 | archive-url = https://web.archive.org/web/20160821212744/http://www.ema.europa.eu/docs/en_GB/document_library/EPAR_-_Procedural_steps_taken_before_authorisation/human/000504/WC500041661.pdf | url-status = dead }}</ref>

==Safety profile of cladribine in hairy cell leukemia==

Injectable cladribine suppresses the body's ability to make new lymphocytes, [[natural killer cells]], and [[neutrophils]] (called [[Bone marrow suppression|myelosuppression]]); data from hairy cell leukemia studies showed that about 70% of people taking the drug developed [[Neutropenia|dangerously low levels of white blood cells]] and about 30% developed infections and some of those progressed to [[septic shock]]; about 40% of people taking the drug had fewer [[red blood cells]] and became severely [[anemia|anaemic]]; and about 10% of people had too few [[platelets]].<ref name=Label/> At the dosage used to treat hairy cell leukemia in two clinical trials, 16% of people had rashes and 22% had nausea, the nausea generally did not lead to vomiting.<ref name=Label/>

==History in multiple sclerosis==

In the mid-1990s, Beutler, in collaboration with Jack Sipe, a neurologist at Scripps Institute, ran several clinical trials exploring the utility of cladribine in multiple sclerosis, based on the drug's immunosuppressive effects. Sipe's insight into multiple sclerosis, and Beutler's interest in multiple sclerosis due to his sister having the disease, initiated a very productive collaboration.<ref name="Sauter E">{{cite web | vauthors = Sauter E, Ono M |title=A potential new MS treatment's long and winding road |url= https://www.scripps.edu/newsandviews/e_20090601/MS.html |website=News & Views - Scripps Research Institute |ref=Sauter E}}</ref> Ortho-Clinical, a subsidiary of Johnson & Johnson, filed a new drug application for cladribine for multiple sclerosis in 1997 but withdrew it in the late 1990s after discussion with the FDA proved that more clinical data would be needed.<ref name="Sauter E" />

Ivax acquired the rights for oral administration of cladribine to treat multiple sclerosis from Scripps in 2000,<ref>{{cite web | agency = Reuters | date = 4 December 2000 | url = http://www.mult-sclerosis.org/news/Dec2000/CladribineforMultipleSclerosis.html | title = Ivax to Develop Cladribine for Multiple Sclerosis }}</ref> and partnered with Serono in 2002.<ref name=WSJSerono>{{cite web | vauthors = Sargent C | work = Dow Jones Newswires in the Wall Street Journal | date = 31 October 2002 | url = https://www.wsj.com/articles/SB1035995148253461151 | title = Serono Purchases Rights To Experimental MS Drug }}</ref> Ivax was acquired by [[Teva Pharmaceutical Industries|Teva]] in 2006,<ref>{{cite web | vauthors = Bayot J | work = New York Times | date = 26 July 2005 | url = https://www.nytimes.com/2005/07/26/business/teva-to-acquire-ivax-another-maker-of-generic-drugs.html?_r=0 | title = Teva to Acquire Ivax, Another Maker of Generic Drugs }}</ref><ref>{{cite web | work = Teva Press Release | date = 2006 | url = http://tevapharm.com/news/teva_completes_acquisition_of_ivax_01_06.aspx | title = Teva Completes Acquisition of Ivax | access-date = 21 August 2016 | archive-date = 18 December 2019 | archive-url = https://web.archive.org/web/20191218064856/https://tevapharm.com/news/teva_completes_acquisition_of_ivax_01_06.aspx | url-status = dead }}</ref> and [[Merck KGaA]] acquired control of Serono's drug business in 2006.<ref>{{cite web | author = Staff | work = First Word Pharma | date = 21 September 2006 | url = http://www.firstwordpharma.com/node/135767#axzz4HwfDP98J | title = Merck KGaA to acquire Serono }}</ref>

An oral formulation of the drug with [[cyclodextrin]] was developed<ref name=MovectroWithdraw>{{cite web | work = Europeans Medicines Agency | date = 2011 | url = http://www.ema.europa.eu/docs/en_GB/document_library/Application_withdrawal_assessment_report/2011/03/WC500104393.pdf | title = Withdrawal Assessment Report for Movectro | quote = Procedure No. EMEA/H/C/001197 | access-date = 21 August 2016 | archive-date = 21 August 2016 | archive-url = https://web.archive.org/web/20160821213510/http://www.ema.europa.eu/docs/en_GB/document_library/Application_withdrawal_assessment_report/2011/03/WC500104393.pdf | url-status = dead }}</ref>{{rp|16}} by Ivax and Serono, and then Merck KGaA conducted clinical trials. Merck KGaA submitted an application to the [[European Medicines Agency]] in 2009, which was rejected in 2010, and an appeal was denied in 2011.<ref name=MovectroWithdraw/>{{rp|4–5}} Likewise Merck KGaA's new drug application with the FDA rejected in 2011.<ref name=MedPage>{{cite web | vauthors = Gever J | date = 22 June 2011 | url = http://www.medpagetoday.com/neurology/multiplesclerosis/27207 | title = Merck KGaA Throws in Towel on Cladribine for MS }}</ref>

The ratio of benefit to harm was not clear to regulators, and further studies were requested to address concerns related to severe lymphopenia and cancer cases observed during pivotal trials.<ref name=MovectroWithdraw/>{{rp|54–55}} Clinical studies of multiple sclerosis were still ongoing at the time of the rejections, and Merck KGaA committed to completing them.<ref name=MedPage/> A meta-analysis of data from clinical trials comparing the risk of cancer and other disease-modifying therapies showed that cladribine tablets did not increase the risk of cancer at the doses used in the initial clinical trials.<ref>{{cite journal | vauthors = Pakpoor J, Disanto G, Altmann DR, Pavitt S, Turner BP, Marta M, Juliusson G, Baker D, Chataway J, Schmierer K | display-authors = 6 | title = No evidence for higher risk of cancer in patients with multiple sclerosis taking cladribine | journal = Neurology | volume = 2 | issue = 6 | pages = e158 | date = December 2015 | pmid = 26468472 | pmc = 4592538 | doi = 10.1212/nxi.0000000000000158 }}</ref>

Based on the supporting data from the completed clinical trials that confirmed no increased risk of cancer, Merck announced it would again seek regulatory approval.<ref>{{cite web |title=Four years after a transatlantic slapdown, Merck KGaA will once again seek cladribine OK |url=https://www.fiercebiotech.com/regulatory/four-years-after-a-transatlantic-slapdown-merck-kgaa-will-once-again-seek-cladribine-ok |website=Fierce Biotech}}</ref> In 2016, the EMA accepted its application for review.<ref>{{cite web | title = Merck Receives European Medicines Agency Acceptance for Review of Marketing Authorization Application for Cladribine Tablets | url = http://www.prnewswire.com/news-releases/merck-receives-european-medicines-agency-acceptance-for-review-of-marketing-authorization-application-for-cladribine-tablets-587207901.html | work = PR News Wire | date = 18 July 2016 }}</ref> On 22 June 2017, the EMA's Committee for Medicinal Products for Human Use (CHMP) adopted a positive opinion, recommending the granting of a marketing authorisation for the treatment of relapsing forms of multiple sclerosis.<ref>{{cite web|url=http://www.prnewswire.co.uk/news-releases/cladribine-tablets-receives-positive-chmp-opinion-for-treatment-of-relapsing-forms-of-multiple-sclerosis-630335053.html|title=Cladribine Tablets Receives Positive CHMP Opinion for Treatment of Relapsing Forms of Multiple Sclerosis|last=Merck|website=www.prnewswire.co.uk|access-date=22 August 2017}}</ref>

Cladribine tablets were later approved in Europe, in August 2017, for highly active relapsing-remitting multiple sclerosis, and has since been approved by the FDA for the treatment of relapsing-remitting and secondary progressive multiple sclerosis in the US.<ref>{{cite web | url = https://www.merckgroup.com/en/news/mavenclad-25-08-2017.html | title = Cladribine approved in Europe | date = 25 August 2017 | work = Merck Press Release }}</ref>

==Use in multiple sclerosis==

As per the EU label, cladribine tablets are indicated for the treatment of adult patients with highly active relapsing multiple sclerosis as defined by clinical or imaging features: (i) patients with a relapse in the previous year and at least one T1 Gd+ lesion or 9 or more T2 lesions, while on another disease-modifying therapies or (ii) patients with two or more relapses in the previous year, whether on disease-modifying treatment or not.<ref name="EMA_2021" />

Two main approaches to multiple sclerosis treatment maintenance therapy are used – immunomodulation and [[immunosuppression]] and alternatively, immune reconstitution therapy. Classified as the latter, cladribine tablets are administered intermittently as a short treatment course without continuous immunosuppression. In contrast to maintenance therapies, clinical efficacy extends beyond the dosing period.<ref name="pmid30944586">{{cite journal | vauthors = Sorensen PS, Sellebjerg F | title = Pulsed immune reconstitution therapy in multiple sclerosis | journal = Therapeutic Advances in Neurological Disorders | volume = 12 | issue = | pages = 1756286419836913 | date = 2019 | pmid = 30944586 | pmc = 6440030 | doi = 10.1177/1756286419836913 }}</ref><ref name="pmid29634596">{{cite journal | vauthors = Giovannoni G | title = Disease-modifying treatments for early and advanced multiple sclerosis: a new treatment paradigm | journal = Current Opinion in Neurology | volume = 31 | issue = 3 | pages = 233–243 | date = June 2018 | pmid = 29634596 | doi = 10.1097/WCO.0000000000000561 | s2cid = 4736668 }}</ref><ref name="pmid28626781">{{cite journal | vauthors = Baker D, Herrod SS, Alvarez-Gonzalez C, Zalewski L, Albor C, Schmierer K | title = Both cladribine and alemtuzumab may effect MS via B-cell depletion | journal = Neurology: Neuroimmunology & Neuroinflammation | volume = 4 | issue = 4 | pages = e360 | date = July 2017 | pmid = 28626781 | pmc = 5459792 | doi = 10.1212/NXI.0000000000000360 }}</ref>

Cladribine tablets are administered as 2 courses separated by 1 year (a maximum of 20 days of treatment). The recommended cumulative dose is 3.5&nbsp;mg/kg weight over 2 years, administered as 1 treatment course of 1.75&nbsp;mg/kg per year. Each treatment course consists of 2 treatment weeks, one at the beginning of the first month and one at the beginning of the second month of the respective treatment year. Each treatment week consists of 4 or 5 days on which a patient receives 10&nbsp;mg or 20&nbsp;mg (1 or 2 tablets) as a single daily dose based on body weight.<ref name="EMA_2021" />

Before initiating treatment with cladribine tablets, blood tests, MRI and infection screening must be performed. Due to an increased risk of [[shingles|herpes zoster]] with cladribine tablets, patients who are antibody-negative for varicella zoster virus are recommended to be vaccinated before starting treatment. Treatment should not be initiated within 4 to 6 weeks of receiving a live or attenuated live vaccine because of a risk of active infection. Vaccination with live or attenuated live vaccines should also be avoided during and after treatment, but can be considered when lymphocyte counts have recovered to ≥1000 cells/mm³.<ref name="EMA_2021" />

Following completion of the two treatment courses, no further treatment or additional monitoring is required.<ref name="EMA_2021" />

The use of cladribine tablets is contraindicated in pregnant women, and women of childbearing potential must use effective contraception to prevent pregnancy during treatment and 6 months after receiving the last dose.<ref name="EMA_2021" />

==Efficacy of cladribine tablets in multiple sclerosis==

Clinical trial results have shown that cladribine tablets can be an effective treatment for highly active, relapsing forms of multiple sclerosis, with significant clinical benefits in relapse rate, disability progression, and radiological measures.<ref name="Giovannoni Mult Scler 2018">{{cite journal | vauthors = Giovannoni G, Soelberg Sorensen P, Cook S, Rammohan K, Rieckmann P, Comi G, Dangond F, Adeniji AK, Vermersch P | display-authors = 6 | title = Safety and efficacy of cladribine tablets in patients with relapsing-remitting multiple sclerosis: Results from the randomized extension trial of the CLARITY study | journal = Multiple Sclerosis | volume = 24 | issue = 12 | pages = 1594–1604 | date = October 2018 | pmid = 28870107 | doi = 10.1177/1352458517727603 | ref = Giovannoni Mult Scler 2018 | s2cid = 1910070 | doi-access = free }}</ref> Compared with placebo, patients who received cladribine tablets (3.5&nbsp;mg/kg) in the CLARITY study had a 58% reduction in annualized relapse rate<ref name="Giovannoni N Engl J Med 2010">{{cite journal | vauthors = Giovannoni G, Comi G, Cook S, Rammohan K, Rieckmann P, Soelberg Sørensen P, Vermersch P, Chang P, Hamlett A, Musch B, Greenberg SJ | display-authors = 6 | title = A placebo-controlled trial of oral cladribine for relapsing multiple sclerosis | journal = The New England Journal of Medicine | volume = 362 | issue = 5 | pages = 416–426 | date = February 2010 | pmid = 20089960 | doi = 10.1056/NEJMoa0902533 | ref = Giovannoni N Engl J Med 2010 | doi-access = free }}</ref> and 47% of patients showed no evidence of disease activity at 2 years.<ref name="Giovannoni Lancet 2011">{{cite journal | vauthors = Giovannoni G, Cook S, Rammohan K, Rieckmann P, Sørensen PS, Vermersch P, Hamlett A, Viglietta V, Greenberg S | display-authors = 6 | title = Sustained disease-activity-free status in patients with relapsing-remitting multiple sclerosis treated with cladribine tablets in the CLARITY study: a post-hoc and subgroup analysis | journal = The Lancet. Neurology | volume = 10 | issue = 4 | pages = 329–337 | date = April 2011 | pmid = 21397565 | doi = 10.1016/S1474-4422(11)70023-0 | ref = Giovannoni Lancet 2011 | s2cid = 20149620 }}</ref> Clinical improvements can be observed at Week 24 of treatment,<ref name="Giovannoni Lancet 2011" /><ref name="Comi 2013">{{cite journal | vauthors = Comi G, Cook SD, Giovannoni G, Rammohan K, Rieckmann P, Sørensen PS, Vermersch P, Hamlett AC, Viglietta V, Greenberg SJ | display-authors = 6 | title = MRI outcomes with cladribine tablets for multiple sclerosis in the CLARITY study | journal = Journal of Neurology | volume = 260 | issue = 4 | pages = 1136–1146 | date = April 2013 | pmid = 23263473 | doi = 10.1007/s00415-012-6775-0 | ref = Comi 2013 | s2cid = 8934723 }}</ref><ref name="Schippling ECTRIMS 2018">{{cite journal | vauthors = Schippling S |title=CLARITY: An analysis of severity and frequency of relapses in patients with RRMS treated with cladribine tablets or placebo |journal=Ectrims |date=2018 |pages=549 |ref=Schippling ECTRIMS 2018}}</ref> and benefits may be sustained up to 4 years, beyond the 2-year dosing period and recovery of total lymphocytes.<ref name="Giovannoni Mult Scler 2018" /><ref name="Comi 2019">{{cite journal | vauthors = Comi G, Cook S, Giovannoni G, Rieckmann P, Sørensen PS, Vermersch P, Galazka A, Nolting A, Hicking C, Dangond F | display-authors = 6 | title = Effect of cladribine tablets on lymphocyte reduction and repopulation dynamics in patients with relapsing multiple sclerosis | journal = Multiple Sclerosis and Related Disorders | volume = 29 | pages = 168–174 | date = April 2019 | pmid = 30885375 | doi = 10.1016/j.msard.2019.01.038 | ref = Comi 2019 | s2cid = 83461539 | doi-access = free }}</ref><ref name="Gavin EAN 2017">{{cite journal | vauthors = Giovannoni G |title=Effect of cladribine tablets on relapse rates and the proportions qualified relapse-free in patients with multiple sclerosis: analysis of the CLARITY and CLARITY extension studies |journal=EAN |date=2017 |pages=0542 |ref=Gavin EAN 2017}}</ref> ''Post-hoc'' analyses of clinical trial data showed that 89% of patients remained free from disability progression two years after treatment.<ref>{{cite journal |vauthors=Giovannoni G, Rammohan K, Cook S, Soelberg-Sørensen P, Vermersch P, Keller B, di Cantogno EV |display-authors=6 |title=An exploratory analysis of the efficacy of cladribine tablets 3.5mg/kg in patients with relapsing multiple sclerosis stratified according to age above and below 45 years in the CLARITY study |journal=Ectrims |date=2018 |pages=1204 |url=https://onlinelibrary.ectrims-congress.eu/ectrims/2018/ectrims-2018/229044/gavin.giovannoni.an.exploratory.analysis.of.the.efficacy.of.cladribine.tablets.html?f=menu%3D14%2Abrowseby%3D8%2Asortby%3D2%2Amedia%3D2%2Aspeaker%3D65030 |access-date=14 July 2021 |archive-date=17 July 2021 |archive-url=https://web.archive.org/web/20210717095305/https://onlinelibrary.ectrims-congress.eu/ectrims/2018/ectrims-2018/229044/gavin.giovannoni.an.exploratory.analysis.of.the.efficacy.of.cladribine.tablets.html?f=menu%3D14*browseby%3D8*sortby%3D2*media%3D2*speaker%3D65030 |url-status=dead }}</ref>

Further analyses of a subgroup of patients in the CLARITY study who had very active multiple sclerosis showed a 67% reduction in relapse rates and an 82% reduction in disability progression in those treated with cladribine tablets. Similarly, clinical improvements were seen in lesion burden on MRI scans in this population.<ref name="Giovannoni Mult Scler 2019">{{cite journal | vauthors = Giovannoni G, Soelberg Sorensen P, Cook S, Rammohan KW, Rieckmann P, Comi G, Dangond F, Hicking C, Vermersch P | display-authors = 6 | title = Efficacy of Cladribine Tablets in high disease activity subgroups of patients with relapsing multiple sclerosis: A post hoc analysis of the CLARITY study | journal = Multiple Sclerosis | volume = 25 | issue = 6 | pages = 819–827 | date = May 2019 | pmid = 29716436 | pmc = 6460686 | doi = 10.1177/1352458518771875 | ref = Giovannoni Mult Scler 2019 }}</ref>

Studies evaluating the treatment effects of cladribine tablets across a spectrum of baseline demographics and disease characteristics showed that the relative risk of relapse was significantly reduced compared with placebo, irrespective of previous treatment experience.<ref>{{cite journal | vauthors = Rammohan K, Giovannoni G, Comi G, Cook S, Rieckmann P, Soelberg Sørensen P, Vermersch P, Hamlett A, Kurukulasuriya N | display-authors = 6 | title = Cladribine tablets for relapsing-remitting multiple sclerosis: Efficacy across patient subgroups from the phase III CLARITY study | journal = Multiple Sclerosis and Related Disorders | volume = 1 | issue = 1 | pages = 49–54 | date = January 2012 | pmid = 25876451 | doi = 10.1016/j.msard.2011.08.006 }}</ref>

Furthermore, treatment with cladribine tablets has been shown to significantly reduce the rate of brain atrophy in patients with highly active relapsing-remitting multiple sclerosis. This reduction correlated with a reduced risk in disability progression in a retrospective analysis.<ref name="pmid28140753">{{cite journal | vauthors = De Stefano N, Giorgio A, Battaglini M, De Leucio A, Hicking C, Dangond F, Giovannoni G, Sormani MP | display-authors = 6 | title = Reduced brain atrophy rates are associated with lower risk of disability progression in patients with relapsing multiple sclerosis treated with cladribine tablets | journal = Multiple Sclerosis | volume = 24 | issue = 2 | pages = 222–226 | date = February 2018 | pmid = 28140753 | doi = 10.1177/1352458517690269 | pmc = 5818021 }}</ref>

In clinical trials, higher cumulative doses of cladribine tablets did not result in further improvement in efficacy nor did additional courses after the 2-year treatment period, but was associated with a higher incidence of Grade 3 and Grade 4 lymphopenia.<ref name="EMA_2021" /><ref name="Giovannoni Mult Scler 2018" />

==Safety profile of cladribine tablets in multiple sclerosis==

Cladribine tablets target the cells of the [[adaptive immune system]] with minimal impact on innate immune cells. Although the exact mechanism by which cladribine exerts its therapeutic effect is not fully elucidated, it is proposed to have a transient effect on B and T lymphocyte depletion, interrupting the cascade of immune events central to multiple sclerosis. As a result, a reduction in lymphocyte count ([[lymphocytopenia|lymphopenia]]) may be reported following treatment.<ref name="EMA_2021" /> In clinical trials, lymphocyte levels above Grade 0 (≥1000 cells/mm³) and Grade 1 (<1000–800 cells/mm³) were maintained in most patients, with levels continuing to improve after the 2-year dosing period.<ref name="Comi 2019" /> Less than 1% of patients developed Grade 4 lymphopenia (<200 cells/mm³). It is important that patients with lymphocyte counts below 500 cells/mm³ should be actively monitored for signs suggestive of infection and that anti-infective treatments are given to at-risk patients.<ref name="EMA_2021" /><ref name="Cook 2019">{{cite journal | vauthors = Cook S, Leist T, Comi G, Montalban X, Giovannoni G, Nolting A, Hicking C, Galazka A, Sylvester E | display-authors = 6 | title = Safety of cladribine tablets in the treatment of patients with multiple sclerosis: An integrated analysis | journal = Multiple Sclerosis and Related Disorders | volume = 29 | pages = 157–167 | date = April 2019 | pmid = 30885374 | doi = 10.1016/j.msard.2018.11.021 | ref = Cook 2019 | s2cid = 81873347 | doi-access = free }}</ref>

Despite the initial reduction in lymphocyte counts following treatment, studies showed the overall risk of infection in patients receiving cladribine tablets was comparable to those who received placebo, except for herpes zoster infection.<ref name="Cook 2019" /> Due to this increased risk, it is recommended that patients are screened for varicella zoster virus and antibody-negative patients are vaccinated prior to receiving treatment.<ref name="EMA_2021" /> In an analysis of post-approval data, as of 2020, no new infection safety signals were observed in over 18,000 patients.<ref name="Giovannoni ACTRIMS-ECTRIMS 2020">{{cite journal | vauthors = Giovannoni G | title=A965 |journal=Actrims-Ectrims |date=2020 |pages=A965}}</ref>

[[Progressive multifocal leukoencephalopathy]] has been reported in patients with hairy cell leukemia treated with parenteral cladribine.<ref name="EMA_2021" /> However, in up to 10 years of follow-up of patients receiving cladribine tablets for multiple sclerosis, no cases of progressive multifocal leukoencephalopathy have been observed; baseline MRI must be performed prior to initiating treatment.<ref name="EMA_2021" />

In clinical trials, malignancies were observed more frequently in patients treated with cladribine tablets compared with patients who received placebo. Compared with a matched reference population from the Global Cancer Observatory <!-- (GLOBOCAN) --> database, cladribine tablets had no increased risk of [[malignancy]] in long-term real-world evidence data.<ref name="EMA_2021" /><ref name="Cook 2019" />

== Research ==

Cladribine has been studied as part of a multidrug [[chemotherapy regimen]] for drug-resistant [[T-cell prolymphocytic leukemia|T-cell prolymphocytic leukaemia]].<ref>{{cite journal | vauthors = Hasanali ZS, Saroya BS, Stuart A, Shimko S, Evans J, Vinod Shah M, Sharma K, Leshchenko VV, Parekh S, Loughran TP, Epner EM | display-authors = 6 | title = Epigenetic therapy overcomes treatment resistance in T cell prolymphocytic leukemia | journal = Science Translational Medicine | volume = 7 | issue = 293 | pages = 293ra102 | date = June 2015 | pmid = 26109102 | pmc = 4807901 | doi = 10.1126/scitranslmed.aaa5079 }}</ref>

== References ==

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