Expert Review of Clinical Immunology Volume 8 Issue 4 2012 [Doi 10.1586%2Feci.12.19] Zerbini, Cristiano AF; Lomonte, Andrea Barranjard Vannucci -- Tofacitinib for the Treatment of

8/9/2019 Expert Review of Clinical Immunology Volume 8 Issue 4 2012 [Doi 10.1586%2Feci.12.19] Zerbini, Cristiano AF; Lo

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319www.expert-reviews.com ISSN1744-666X 2012 Expert Reviews Ltd10.1586/ECI.12.19

Drug Profile

Rheumatoid arthritis

Rheumatoid arthritis (RA) is a common systemicautoimmune disease characterized by a chronicand progressive inflammatory polyarthritis [1].Affected patients often experience inflammatorysigns of small joints of the hands and feet butmany other joints may be involved such astemporomandibular joints, wrists, elbows,

shoulders, hips, knees and ankles. Although amonoarticular involvement may occur initially,the articular signs of inflammation usuallybecome symmetrical. Many patients complainof joint stiffness early in the morning that maylast for more than one hour. The duration of thissensation is in direct proportion with the degreeof the articular inflammation.

Immune response

Th1 cell activation by a still unknown antigenis the first event in the beginning of the RA

development process. The inflamed synovium

contains a great amount of T cells. Thesecells, mostly CD4+with memory phenotype,constitute about 50% of the cell population inthe RA synovial membrane. B lymphocytes andplasma cells comprise only 5% of the synovialcell population but their activation by CD4+T cells help them to increase the production ofsynovial antibodies. The concept of RA as a Th1

disease became weaker after the finding that Th1cytokines including IFN-g, although detected inthe RA synovial tissue, are in far lower levelsthan the inflammatory cytokines TNF-a, IL-6and IL-1 [2]. After the identification of the Th17pathway the proinflammatory role of T cells inRA became better understood. Th17 lineage isdistinct from Th1 and Th2 lineages of T effectorcells [3]. Th17 and its signature cytokine IL-17may play a central role in the pathogenesisof RA. IL-6 and TGF-b induce the Th17differentiation whereas IL-23, a member of the

IL-12 family, promotes its survival, expansion

Cristiano AF Zerbini*and Andrea BarranjardVannucci Lomonte

Centro Paulista de Investigao Clinica

& Department of Rheumatology,

Hospital Helipolis, So Paulo, Brazil

*Author for correspondence:

Tel.: +55 11 35146022

Fax: +55 11 [email protected]

Rheumatoid arthritis (RA) is a chronic inflammatory disease that affects approximately 1% ofthe worldwide population. It primarily targets the synovial membrane of joints, leading to asynovial proliferation, joint cartilage lesion and erosions in the adjacent bone tissue. The diseaseis usually progressive and if the inflammatory process is not adequately suppressed, jointdeformity takes place, leading to a significant functional disability and work incapacity. Overthe last decade, biological therapy was established as a major step towards disease control inthose patients who experienced failure after treatment with disease-modifying antirheumaticdrugs. Despite the growing number of biological agents with different immunological targets,a significant number of patients do not receive appropriate disease control, or have the use ofthese agents limited because of adverse events. As such, the search for new molecules with ahigher efficacy and better safety profile is ongoing. This article focuses on a new drug, tofacitinib,which is a synthetic disease-modifying antirheumatic drug for treatment of RA. Preclinical studiesin arthritis and transplantation animal models are reviewed as a background for the possibleuse of tofacitinib treatment in humans. Four Phase II (one A and three B dose-ranging) trialslasting from 6 to 24 weeks in RA patients showed significant American College of Rheumatology20 improvements as early as week 2 and sustained at week 24 in two studies. Tofacitinib Phase IIIstudies in RA are included in a clinical program called ORAL Trials. Long-term follow-up fromongoing studies will contribute to a more accurate tofacitinib efficacy and safety profile. Trialsin other illness such as psoriasis, psoriatic arthritis, renal transplant rejection prevention,inflammatory bowel diseases and dry eye are underway.

KEYWORDS:JAK inhibitionjanus kinase inhibition mechanism of action rheumatoid arthritis tofacitinib

treatment

Tofacitinib for the treatment

of rheumatoid arthritisExpert Rev. Clin. Immunol. 8(4), 319331 (2012)


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Expert Rev. Clin. Immunol.8(4), (2012)320

Zerbini & LomonteDrug Profile

and pathogenicity [4]. IL-17 acts on many cells found in theinflamed synovium and also induces a wide variety of effectormolecules. Fibroblasts, monocytes, macrophages, chondrocytesand osteoclasts are stimulated by IL-17. Proinflammatorycytokines such as IL-1, IL-6 and TNF-a, prostaglandin E

2,

matrix metalloproteinases, and COX-2 have their productionupregulated by IL-17. It also upregulates the receptor activatorfor nuclear factor kB ligand (RANKL) production on osteoblastsand chondrocytes. RANKL promotes the differentiation andactivation of osteoclasts with consequent development of boneerosions and osteoporosis [5]. IFN-ghas inhibitory effects on Th17cells and this has been linked to a protective effect on joints [6].Another lineage of T cells may play a role in the developmentof RA. Treg cells are a population of CD4 +CD25+T cells thatsuppress CD4 and CD8 T-cell responses through cellcellcontact [7]. These cells may be functionally abnormal in theperipheral blood of patients with active RA [8]. The impairment

of Treg cell function may be induced by TNF-aand reversed byanti-TNF treatments explaining, at least in part, the efficacy ofthis therapy.

Many changes take place in the RA synovial membrane afterthe beginning of the inflammatory process. Normal synovialmembrane is composed of one to three cell layers without adefinite underlying basement membrane and a synovial sublining

within the joint capsule. After the initiation of the inflammatoryprocess (synovitis) hyperplasia of the synovial lining takes place.This is caused by tissue edema after vessel proliferation and newvessel formation. Angiogenesis, the generation of new bloodvessels, is one of the early pathologic responses in the synovitis.

Angiogenesis is induced by the transcription factor HIF-1 andsome angiogenic factors produced by synovial cells: HBGF,macrophage angiogenic factor, VEGF, prostaglandin E

1and E

2,

IL-8, CXC chemokines and others [9]. Angiogenesis is criticalfor the development of synovitis. The growth of new bloodvessels and the generation of adhesion molecules (i.e., integrins,E selectin and vascular cell adhesion molecule 1) facilitate themigration of cells to the synovial membrane. The synoviallesion starts with the initial transudation of fluid (edema)after neovascularization followed by a local accumulation ofcells (lymphocytes, macrophages and mast cells). These cellscan produce many cytokines and their autocrine and paracrine

communication results in a proliferative response of the affectedsinovium. The inflammatory process begins to be more organizedand synovial lining hyperplasia becomes more intense, extendingitself to a depth of more than ten cell layers. The synovial cells(synoviocytes) are divided into two types: macrophage-like cells(type A) and fibroblast-like cells (type B). Resident synovial cells,under the action of multiple cytokines, change phenotype and

may be transformed into very active anddestructive cells. Cadherin-11, a synovialintegral membrane protein, mediates thefibroblast-like synoviocyte invasion ofsynovial tissue [10]. These transformed cellsproduce very active enzymes, the matrix

metalloproteinases (MMP-1, MMP-3 andMMP-13) responsible for the destructiveprocess of cartilage. The invadinginflammatory process containing manycytokines and cells is calledpannus.

Of special interest are the interactionsof cytokines in the RA synovium [11].Briefly, TNF-a, IL-1, IL-6, IL-18, VEGFand chemokines cause the recruitmentof inflammatory cells. IFN-a, IFN-b,TNF-a and IL-15 facilitate, by differentmechanisms, the retention of cells in the

synovium. IL-23, IL-12, IL-27, IL-15, IL-18and chemokines organize and activate Tcells. TNF-a, IL-17 and TGF-bmediatethe proliferative and destructive part of theinflammatory process (FIGURE1).

The knowledge of RA pathogenesis iscritical for the understanding of how oldand new therapeutic interventions canavoid joint damage and prevent morbidityand even mortality. Disease modifyingantirheumatic drugs (DMARDs) are thecornerstone in the treatment of RA. These

drugs can change the natural history of RA

Figure 1. Cytokine network in the rheumatoid arthritis sinovium.ACPA: Anticitrullinated protein antibody; FLS: Fibroblast-like sinoviocyte;GM-CSF: Granulocytemacrophage colony-stimulating factor; M-CSF: Macrophagecolony-stimulating factor; MMP: Matrix metalloproteinase; OPG: Osteoprotegerin;RANKL: Receptor activator for NF-kB ligand; RF: Rheumatoid factor.

ACPA

RF

B cell IL-2+

IL-2++

+

+

+

+

+

+

-

-

-

IL-4

IL-6

IL-6IL-8

GM-CSF

GM-CSFM-CSF

IL-1

IL-18

IL-18

IL-15

IL-1

TNF-

TNF-

M-CSF M-CSF

RANKLOPG

TNF-

IFN-

IL-12

IL-10

IL-10

IL-17

T cell

Vascular bed

Chemokines

Prostaglandins

Pannusformation

MMPs

CartilageBoneExpert Rev. Clin. Immunol. Future Science Group (2012)

Osteoclast

FLS

Macrophage


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Tofacitinib for the treatment of rheumatoid arthritis Drug Profile

by reducing the structural joint damage seen in the radiographicexams and preserving joint integrity and function. Methotrexate(MTX) is the most used DMARD in clinical practice andcan be prescribed initially as monotherapy or in combinationwith other drugs. In the last 10 years significant progress hasbeen made in the treatment of RA after the introduction ofthe biological DMARDs in the clinical routine (TABLE1). Thesenew drugs, used alone or in combination with MTX, providebetter and faster results in the resolution of the inflammatoryprocess. The American College of Rheumatology (ACR) andthe European League Against Rheumatism have published

recommendations for the management of RA includingbiological DMARDs. These recommendations can be foundat [101,102]. Some studies showed patients reaching ACR70 andeven remission evaluated by Disease Activity Score in 28 joints(DAS28) [1215]. Unfortunately, there are RA patients that arenot responsive to the available therapeutic agents and somepatients cannot use them after developing side effects. In thesearch for new biological treatments efforts have been made tofind more selective immunosuppressive therapies such as thosetargeting the cytokine signaling pathways. One of these targetsis the JAK pathway.

The JAK pathwayJAKs play an important role as gate keepers in the signa ltransduction pathway of many cytokines involved in the acquiredand innate immunity [16,17]. This family of tyrosine kinases iscomposed of four intracellular nonreceptor enzymes (JAK1,JAK2, JAK3 and Tyk2) and was named after the Roman godof gates and doors (Janus). JAK3 is predominantly expressedat high levels in hematopoietic tissues, being found in myeloidcells, thymocytes, natural killer (NK) cells, and activated B andT lymphocytes. It is not expressed in resting T cells [18]. JAK3binds to only one cytokine receptor, the common g chain orgc (F IGURE2 ). This chain is shared by many cytokine receptors,

including IL-2, IL-4, IL-7, IL-9, IL-15 and IL-21 [19]. JAK1 is

largely expressed (lymphoid cells, nervous system) and bindsto the b-subunit of these cytokine receptors. After the bindingof a cytokine to its membrane receptor, JAK1 and JAK3 comeinto close proximity and become bound to the cytoplasmic tailof the assembled receptor. These enzymes then undergo auto-transphosphorylation. This leads to the binding and activation ofthe monomeric signal transducers and activators of transcription(STAT) proteins, which bind to the cognate cytokine receptorsvia conserved Src homology 2 domains [20]. Receptor-boundSTATs become phosphorylated at their C-terminus and undergodimerization (homo- and hetero-dimerization), which allows

them to be translocated to the nucleus where they bind to genepromoter regions to regulate the transcription of a wide varietyof targeted genes. This activation of gene transcription is criticalfor the lymphocyte development and the immune response.JAK3 germline inactivating mutations have been described inthe autosomal recessive severe-combined immunodeficiencydisease, an inherited immunodeficiency characterized by aprofound defect in mature T and NK cells [21]. In this diseasepatients develop life-threatening infections early in lifeand are treated by hematopoietic stem cell transplantation.Mutations in JAK3 or gc receptors lead to virtually identicalimmunodeficiency phenotypes showing that JAK3 requires the

structure of gc to become activated. JAK3-deficient mice have asimilar phenotype displaying absence of lymph nodes, deficiencyin the development of thymic progenitor cells and low numberof circulating T and NK cells [22]. The critical role playedby the JAK family of enzymes in immune cell developmentand function makes these molecules an attractive target formodulation of immune function as a strategy for treatingautoimmune diseases. Some new protein kinase inhibitors arealready in development (TABLE2) .

With the intent ion to re-assess the role of more efficienttreatments of RA, a disease still incurable and with a smallchance of remission, this paper provides an overview of recent

information on tofacitinib, a highly potent oral DMARD.

Table 1. Biologics approved for the treatment of rheumatoid arthritis.

Generic name (trade name) Properties

Abatacept (Orencia) Fusion protein of the extracellular domain of human CTLA4 linked to a fragment of the FC segment

of human IgG1 specific for CD80/86

Adalimumab (Humira) Human mAb specific for TNF

Anakinra (Kineret) Recombinant human IL-1 receptor antagonist

Certolizumab pegol (Cimzia) PEGylated humanized antibody F(ab) fragment specific for human TNF

Etanercept (Enbrel) Fusion protein of extracellular domain of the human p75 TNF-areceptor linked to the FC portion of

human IgG1

Golimumab (Simponi) Human mAb specific for TNF

Infliximab (Remicade) Chimeric mAb specific for TNF

Rituximab (Rituxan/MabThera) Chimeric mAb specific for CD20 antigen

Tocilizumab (RoActemra/Actemra) Humanized mAb specific for the IL-6 receptor

mAb: Monoclonal antibody.Data taken from [54].


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Tofacitinib (CP-690,550)

Tofacitinib (CP-690,550) or ((3R,4R)-4-methyl-3-(methyl-1H-pyrrolo[2,3-d]pyrimidin-4-ylamino)-b-oxo-1-piper-idinepropanenitrile, 2-hydroxy-1,2,3-propanetricarboxylate),previously named tasocitinib (FIGURE3 ), is a potent inhibitor ofthe JAK family of tyrosine kinases [23,24]with a high degree of

selectivity within the human kinome (set ofprotein kinases in the genome). Tofacitinibshowed nanomolar inhibitory potencyagainst all JAK family kinases in enzymestudies and functional specificity for JAK1

and JAK1/3 over JAK2 in cell assays. Inenzyme studies its inhibitory activity,measured by its concentration providing50% enzymatic inhibition (IC

50), showed

IC50

= 3.2 nM for JAK1, IC50

= 4.1 nM forJAK2, IC

50= 1.6 nM for JAK3 and IC

50

= 34.0 nM for Tyk2, with approximately1000-fold selectivity for JAK3 comparedwith 82 other k inases for which IC

50has

been determined [25]. In a cellular setting,a series of assays were performed withcombinations of JAK enzymes to evaluate

the potency of tofacitinib. The inhibitoryeffect of tofacitinib was much morepotent against JAK1/3-dependent activitythan with other JAKs. In the two assaysmediated by JAK3 and JAK1, the IL-2-dependent T-cell proliferation showed anIC

50of~11 nM and the mixed lymphocyte

showed IC50

= 87 nM. A granulocytemacrophage-colony stimulating factor(GM-CSF)-proliferation assay driven byJAK2 resulted in an IC

50of ~324 nM in a

Hu03 cell based assay, which suggests thatinhibition of JAK2 could only be seen at

higher concentrations in vivo. The activityof tofacitinib has also been determined inhuman whole blood assays monitoringSTAT phosphorylation [26]. Tofacitinibinhibited JAK1/3-dependent signaling ofthe gc chain cytokines with an IC

50between

25 and 60. JAK2-driven STAT phosphorylation stimulated byGM-CSF was inhibited only at higher concentrations (1377nM). IFN-gprotein production from the blood following eitherIL-2 (JAK1/3) or IL-12 (JAK2/TYK2) stimulation showed onlymoderate selectivity. These cellular setting data support tofacitinibas a potent inhibitor of JAK3- and JAK1-dependent signaling

Table 2. Protein kinase inhibitors in clinical development.

Compound Target(s) Selected indications (Phase)

INCB-28050 JAK1/2 Rheumatoid arthritis (Phase I I)

Tofacitinib/CP-690550 JAK1/3 Rheumatoid arthritis (Phase III), psoriasis (Phase III), inflammatory bowel disease (Phase II)

VX-509 JAK3 Rheumatoid arthritis ( Phase II)

VX-702 p38 MAPK Rheumatoid arthritis (Phase II)

BMS-582949 p38 MAPK Rheumatoid arthritis, atherosclerosis (Phase II), psoriasis (Phase III)

Fostamatinib disodioum/R-788 SYK Rheumatoid arthritis, B-cell lymphoma, immune thrombocytopenic purpura, peripheral

T-cell lymphoma, solid tumors (Phase II)

Data taken from [54].

Figure 2. Cytokine signaling through the JAK1/JAK3/STAT pathway.JAK3 and gmutations leading to virtually identical phenotypes of SCID (autosomalrecessive SCID).X-SCID: X-linked severe-combined immunodeficiency disease.Reproduced with permission from [55].

IL-2, IL-4, IL-7, IL-9, IL-15, IL-21 X-SCID

Cytokine receptor

Cellular

membraneJAK1 JAK3 JAK3SCID

STAT

P

Nuclear

membrane

Transcription


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with moderate functiona l selectivity over JAK2/Tyk2- andJAK2-driven activation of the pathway.

The stereochemistry of tofacitinib and a model of spatialbinding to JAK3 were elegantly analyzed [27]. The chirality(property of a molecule that lacks an internal plane of symmetry

and thus does not have a superimposable mirror image) oftofacitinib defined its ability to bind to JAK3 and block JAK3dependent STAT5 phosphorylation. This conclusion wasobtained after a combination of molecular modeling, targetprofiling and cell-based analysis.

Pharmacokinetics & metabolism

The pharmacokinetics of tofacitinib has been analysed across RApatients, patients with Crohns disease, patients with ulcerativecolitis, de novo and stable renal transplant patients, renallyimpaired subjects, hepatically impaired subjects, patients withpsoriasis and healthy volunteers. Single oral doses ranging from

0.1 to 100 mg, two-times a day (b.i.d.) oral doses ranging from1 to 50 mg and once a day (q.d.) oral doses ranging from 20 to60 mg were evaluated in these subjects for a period ranging from2 weeks to 3 years. Tofacitinib is rapidly absorbed and eliminatedwith a time to peak concentration (T

max) of approximately 0.5 h

and a half-life of approximately 3 h. The protein binding oftofacitinib is approximately 40%, raising the possibility of a lowdrug interaction due to drug displacement.

The clearance of tofacitinib, calculated in healthy volunteersafter intravenous administration is approximately 24.7 l/h.The clearance of tofacitinib appears to be 70% by hepaticmetabolism and 30% by renal excretion of the unchanged drug.The metabolism of tofacitinib is mainly mediated by CYP3A4

with a small par t mediated by CYP2C19 [28]. Inhibitors orinducers of CYP3A4 may interact with tofacitinib [29,30]. Thecoadministration of tofacitinib and MTX had no effect ontofacitinib pharmacokinetics. During this coadministration,small variations observed in the extent of absortion (areaunder the plasma concentrationtime curve; AUC) and peakconcentrations (C

max) of MTX were considered not clinically

significant. Coadministration of tofacitinib with fluconazole,a moderate inhibitor of CYP3A4 and a strong inhibitor ofCYP2C19, increased the AUC and C

maxof tofacitinib by 79

and 27%, respectively. The coadministration of cyclosporine,a moderate inhibitor of CYP3A4, increased the AUC of

tofacitinib by 73% and decreased the Cmaxby 17%. In patientswith renal impairment the mean AUC

(0-)was 137% in mild

renally impaired subjects reaching 143 and 223% for those withmoderate and severe renal impairment, respectively [31].

Animal models

Tofacitinib showed its efficacy in two arthritis animal models:murine collagen-induced arthritis and rat adjuvant-inducedarthritis (AIA). Animal arthritis was induced by standardprotocols and tofacitinib was delivered by osmotic pumpinfusion at doses 0 (control), 1.5, 5 and 15 mg/kg/day [32].In the murine model, when efficacy was scored based on the

severity of paw swelling, the effective median dose (ED50) was

approximately 1.5 mg/kg/day, or an average serum concentration(Cave) of 6 ng/ml. At the end of the study, after animals wereeuthanized, inflammation score based on histological findingsshowed the ED

50 to be equivalent to a dose of 6.5 mg/kg or

Cave of 38 ng/ml. Histological evaluation also showed a dose-dependent reduction in the inflammatory process and cartilagedestruction after tofacitinib treatment. Doses of 5 and 15 mg/

kg/day produced an almost entire suppression of clinical scoresand the 15 mg/kg/day dose was associated with a significantreduction in the levels of IL-6. In the AIA model Meyer et al.evaluated thepotency of tofacitinib administered orally on pawedema (arthritis), plasma cytokines, neutrophil counts andbone marrow differentials [26]. In this model, an adjuvant ofMycobacterium butyricumwas injected subcutaneously at thebase of the rat tail on day 0. The induced paw arthritis wasfully developed on day 13 post-immunization and peakedon day 21. Plasma neutrophilsand cytokines IL-17 and IL-6significantly increased with disease progression. Neutrophilcounts and IL-17 peaked on day 14 and declined on day 21 butIL-6 peaked also on day 14 but remained elevated through day

21. In this experiment, tofacitinib or vehicle control was givenorally to rats twice daily from day 14 to day 21. Tofacitinibat 10 mg/kg showed good efficacy at reducing paw volume tonormal by day 21. The relation between paw volume responseand tofacitinib exposure represented an ED

50of 0.55 mg/kg. In

the same study this ED50

exposure was compared with the in vitrorat whole blood JAK1/2, and JAK1/3 IC

50values showing that

this value of exposure was sufficient to inhibit JAK1 and JAK3but not JAK2. Disease-elevated neutrophil count decreased tonormal range in AIA rats treated with the 10 mg/kg tofacitinibdose. Levels of IL-17 and IL-6 also decreased dose-dependentlyshowing approximately 80% inhibition in comparison with

control levels. Tofacitinib at 10 mg/kg also inhibited the AIA-induced increase in maturing myeloid cells harvested from ratfemur bone marrow by 50%. Neutrophilia observed in the AIArats was mainly related to the inflammatory process but also, atleast in part, to the increase in granulopoiesis. The small dose oftofacitinib used in this experiment and the doses currently beingadministered in Phase III clinical trials in RA (5 to 10 mg b.i.d.)are associated with a JAK2 IC

50, which is much less significant

than the JAK1/JAK3 IC50

[33]. Taking this into account, theobserved decrease in plasma neutrophils was probably relatedto attenuation of the inflammatory process and not due to thesuppression of granulopoiesis associated with inhibition of JAK2.

Neither neutropenia nor myelosuppression were observed in the

Figure 3. Tofacitinib.

NH

NCN

O

N

N

N


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AIA rats. This study demonstrated a good relationship betweenpharmacologic parameters of JAK1/JAK3 inhibition and efficacyof tofacitinib in the treatment of inflammation in the AIA ratmodel. Signs of arthritis (paw edema), levels of inflammatorycytokines and neutrophilia correlate very well with disease

severity and all of them were reduced after tofacitinib treatment.Ghoreschi et al.analyzed the effects of tofacitinib on adaptive

and innate immune responses in a model of cytokine stimulationof mouse and human T cells in vitroand also the drug effecton Th differentiation of naive murine CD4 +T cells [33]. Theirstudy showed that tofacitinib inhibited IL-4 (cytokine thatsignals through JAK3/JAK1) dependent Th2 cell differentiationand also generation of inflammatory Th17 cells in response toIL-23, IL-6 and IL-1b. Interestingly, tofacitinib, by suppressingSTAT5, may stimulate the expression of a less pathogenic IL-17produced when Th17 cells are generated with TGF-b andIL-6 rather than the more pathogenic cytokine when Th17 is

generated in the absence of TGF-b. This study also suggests thattofacitinib prevented Th1 differentiation by a mechanism otherthan JAK3 inhibition. Tofacitinib inhibited Th1 differentiationby inhibiting STAT1 activation and suppressing the expressionof the Th1-associated transcription factor T-bet. To examinethe possible effect of tofacitinib in the innate immune responsethe authors observed the drug action on the model of acuteresponse to lipopolysaccharides. This inflammatory response ishighly dependent upon IFN-gand STAT1. After a single dose oftofacitinib, production of STAT1, TNF and IL-6 were suppressedconfirming the blockade of innate immune response. The dataobtained in this study show that the immunosuppressive effectsof tofacitinib appear to be associated with interference in the

innate and adaptive types of immune responses.Tofacitinib treatment effects on subsets of circulating

lymphocytes were assessed in rodent and monkey experiments[34,35]. Based on baseline NK cell numbers, tofacitinib wasadministered in a single-day dose to 20 cynomologousmacaques divided into groups of five animals. Each group wasrandomized to one of following tofacitinib treatments: vehicle,10, 50 or 200 mg/kg/day. Fluorescence-activated cell sortingand pharmacokinetics analysis were performed at different timesafter the first dose. There were no significant compound-relatedreductions on NK cells for up to 2 weeks after the single-daydosing and also no changes in other T or B lymphocytes.

The immunosuppressive effects of tofacitinib were alsoevaluated in murine and primate models of transplantationeither alone or in combination with other drugs. Tofacitinibin vivo efficacy was tested in two rodent models: vascularizedand nonvascularized allogeneic cardiac transplantation models[36,37]. In both models tofacitinib monotherapy was effective inprolonging cardiac transplants in a concentration-dependent way.The combination of tofacitinib with cyclosporine or rapamycinin mouse models of transplantation was also assessed. Theseexperiments showed improvement of cardiac graft survival duringtofacitinib therapy, either alone or in combination with otherimmunosuppressants. Improvement was measured by increase

in transplant mean survival time and also by observation of a

lower infiltration of inflammatory cells in the transplanted organ.Tofacitinib was evaluated as monoterapy or in combination withmycophenolate mofetil (MMF) in a model of life-sustaining renaltransplantation in cynomologus monkeys [38,39]. Tofacitinib andMMF were given b.i.d. by oral gavages. All animals were observed

for 90 days and then euthanized or euthanized sooner if a renalallograft failure was observed. Results showed that survival andterminal histological findings seen in combination therapy ortofacitinib monotherapy were comparable and both were superiorto placebo or MMF alone.

Clinical studies

Tofacitinib clinical trials are listed at [103].

Efficacy

Phase IIa monotherapy study

The proof of concept monotherapy study was a randomized,

double-blind, placebo-controlled, multicenter study designed tocompare three doses of tofacitinib administered orally b.i.d. incomparison to placebo in the treatment of signs and symptoms ofpatients with active RA [40]. This study included 264 RA patientswho experienced fai lure with MTX or a TNF-ainhibitor, whowere randomized to receive tofacitinib 5, 15 or 30 mg b.i.d. orplacebo for 6 weeks in a 1:1:1:1 ratio. Efficacy was evaluated atweeks 1, 2, 4, 6 (treatment end) and 8. The ACR20 responserates at week 6 were 70.5, 81.2, 76.8 and 29.2%, respectively(with p < 0.001 for all treatment groups compared with placebo).Improvements in disease activity were observed as early asweek 1 of treatment for all tofacitinib groups in comparison toplacebo. Increased ACR50 and ACR70 response rates, relative

to placebo, were seen at all time points, with a statisticallysignificant difference versus placebo in all tofacitinib groups byweek 4. A ll components of ACR response criteria improved intofacitinib groups by week 6 compared with placebo. A differencein response was seen between the 5 mg b.i.d. dosage and the twohigher dosages, but no clear difference was observed betweenthe 15- and 30-mg b.i.d. dosages in any of the individual ACRcomponent scores. DAS28 was an exploratory end point in thisstudy and it was calculated with C-reactive protein (CRP) levels(DAS28-3[CRP]). Decreases in DAS28-3(CRP) were dose-dependent in the tofacitinib groups, and the percentages ofpatients with a moderate or good response to treatment according

to the European League Against Rheumatism criteria werenumerically superior in the higher dosages groups in comparisonto the 5 mg b.i.d. group.

At week 6, significantly more patients receiving tofacitinibthan placebo experienced a 50% improvement in pain accordingto Visual Analogue Scale scores (44, 66, 78 and 14% for 5, 15and 30 mg b.i.d. tofacitinib and placebo groups, respectively).A stat istica lly significant difference was found between al ltofacitinib groups and placebo at week 6 regarding the HealthAssessment Questionnaire Disability Index (HAQ-DI) and theShort Form 36 Health Survey physical component. These datademonstrated tofacitinib efficacy in improving pain, function and

health status in patients with RA [41].


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Phase IIb dose-ranging combination study

Five hundred and seven RA patients who had an inadequateresponse to MTX were randomized to receive tofacitinib 1, 3,5, 10 or 15 mg b.i.d., 20 mg q.d. or placebo for 24 weeks, withbackground MTX in this double-blind, multicenter study [42].

After week 12, subjects in the placebo group as well as those in the1 mg b.i.d., 3 mg b.i.d. and 20 mg q.d. groups could be reassignedto the 5 mg b.i.d. group if a reduction of at least 20% in swollenand painful/tender joint counts was not achieved. Tofacitinibdoses equal to or greater than 3 mg b.i.d. had significantly higherACR20 response rates at week 12 than placebo group (52.9% fortofacitinib 3 mg b.i.d., 50.7% for 5 mg b.i.d., 58.1% for 10 mgb.i.d., 56.0% for 15 mg b.i.d., 53.8% for 20 mg q.d. and 33.3% forplacebo group, with p 0.05 for all tofacitinib groups). ACR20response rates and secondary end points of the study, includingACR50, ACR70, and DAS28-3(CRP) remission were sustainedat week 24 for doses 5 mg b.i.d. and higher. In conclusion, the

addition of tofacitinib equal to or greater than 5 mg b.i.d. toMTX therapy in this population showed sustained efficacy over24 weeks, with the highest ACR20 response rates in the 10 mgb.i.d. group and the highest ACR50 and 70 response rates in the15 mg b.i.d. tofacitinib group.

Phase IIb dose-ranging monotherapy study

In this 24-week double-blind, dose-ranging monotherapy study,384 RA patients with an inadequate response to a DMARD wererandomized to placebo; tofacitinib 1, 3, 5, 10 or 15 mg orallyb.i.d.; or adalimumab 40 mg subcutaneously every 2 weeks [43].Patients randomized to tofacitinib 1 or 3 mg or placebo who didnot achieve a reduction of at least 20% from baseline in swollen

and tender/painful joint counts at week 12 were blindly reassignedto tofacitinib 5 mg b.i.d. All patients receiving adalimumab werereassigned to tofacitinib 5 mg b.i.d. at week 12. The primary endpoint was the ACR20 response rate at week 12. The safety ofreassignment from adalimumab to tofacitinib was evaluated. Asreported for the combination study, ACR20 response rates weresignificantly higher for all tofacitinib doses equal to or greaterthan 3 mg b.i.d. at week 12 in comparison to placebo: 39.2%for 3 mg (p < 0.05), 59.2% for 5 mg (p < 0.0001), 70.5% for10 mg (p < 0.0001) and 71.9% for 15 mg (p < 0.0001). ACR20response rates at week 12 were 35.9% for ada limumab (p = 0.105vs placebo) and 22.0% for placebo. At week 24, efficacy continued

to be seen in the 5-, 10- and 15-mg groups for ACR20 responserates and secondary end points of the study, including ACR50,ACR70 and DAS28-4(erytrocyte sedimentation rate [ESR]). Thehighest ACR50 and ACR70 response rates at week 24 were seenfor tofacitinib 10 mg b.i.d. and 15 mg b.i.d.

Phase IIb dose-ranging combination study in Japan

The Japanese combination study included one hundred and 40 RApatients with inadequate response to background MTX [44]. Thesubjects were randomized to receive tofacitinib 1, 3, 5 and 10 mgb.i.d. or placebo in combination with MTX for 12 weeks. ACR20response rates at week 12 were 64.3, 77.8, 96.3 and 80.8%,respectively, compared with 14.3% for placebo (p < 0.0001for all tofacitinib groups). At week 2 all tofacitinib groups hada significantly greater ACR20 response than placebo. Dose-dependent increases in both DAS remission rates and low DAS rateswere observed for treatment groups, regardless of DAS28-3(CRP)

score at baseline. In patients with high disease activity at baseline,the tofacitinib 10 mg b.i.d. group had the greatest percentage ofDAS remission (45.5%, p < 0.01) and low DAS at week 12 (72.7%,p < 0.0001). TABLE3summarizes Phase II tofacitinib studies.

Phase III monotherapy study

This randomized, double-blind, placebo-controlled, 6-monthstudy evaluated two doses of tofacitinib monotherapy in610 patients with active RA who had failed at least one DMARDtherapy [45]. Patients were randomized to one of the followingsequences: tofacitinib 5 mg b.i.d.; tofacitinib 10 mg b.i.d.; placebofollowed by tofacitinib 5 mg b.i.d. after 3 months and; placebofollowed by tofacitinib 10 mg b.i.d. after 3 months. The advance of

placebo to tofacitinib groups after 3 months was done in a blindedfashion. The month 3 ACR20 response rates for tofacitinib 5 and10 mg b.i.d. were 59.8 and 65.7% respectively in comparison to26.7% for the placebo group (p < 0.0001). As early as week 2,significant ACR20 response rates versus placebo were seen fortofacitinib 5 and 10 mg b.i.d. (p < 0.0001), as well as significantACR50 response rates for tofacitinib 10 mg b.i.d. (p < 0.05) andsignificant ACR70 response rates for tofacitinib 5 mg (p < 0.05)and 10 mg b.i.d. (p < 0.001). By month 6, similar changes frombaseline were observed for those patients who advanced fromplacebo to tofacitinib groups in comparison to the respectivedosing groups at month 3.

Table 3. Phase II trials of tofacitinib for rheumatoid arthritis treatment.

Study ClinicalTrials.govidentifier

Doses (mg) Patients (n) Duration oftreatment (weeks)

Ref.

Phase IIa monotherapy NCT00147498 5, 15, 30 b.i.d. and placebo 264 6 [40]

Phase IIb dose-ranging combination NCT00413660 1, 3, 5, 10, 15 b.i.d., 20 q.d. and

placebo

507 24 [42]

Phase IIb dose-ranging monotherapy NCT00550446 1, 3, 5, 10, 15 b.i.d., adalimumab

40.q2wk, and placebo

384 24 [43]

Phase IIb dose-ranging combination

(Japan)

NCT00603512 1, 3, 5, 10 b.i.d. and placebo 140 12 [44]

40.q2wk: 40 mg every 2 weeks; b.i.d.: Two-times a day; q.d.: Once a day.


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Phase III combined therapy study in MTX inadequate responders

This is an ongoing 2-year study to examine structural progressionwith tofacitinib in RA patients with inadequate response to MTX.Only partial results from a 1-year interim analysis are available atpresent [46]. In this double-blind study 797 patients were randomized

to one of four groups: tofacitinib 5 mg b.i.d., tofacitinib 10 mg b.i.d,placebo advanced to tofacitinib 5 mg b.i.d., or placebo advancedto tofacitinib 10 mg b.i.d. After 3 months, patients who had notachieved at least 20% improvement in joint counts advanced totofacitinib 5 or 10 mg b.i.d., while the remaining patients onplacebo advanced to tofacitinib 5 mg or 10 mg b.i.d. at month 6.x-rays were analyzed and modified total Sharp-Score with linearextrapolation was used. ACR20 response rates at month 6 were 51.5and 61.8% for tofacitinib 5 mg and 10 mg, respectively, and 25.3%for placebo (p < 0.0001). Tofacitinib 10 mg b.i.d. significantlyreduced radiographic progression of joint damage in comparisonto placebo (mean changes in mTSS were 0.06 for tofacitinib versus

0.47 for placebo, p < 0.05) and produced significant improvementsin DAS28-4(ESR)


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in patients receiving tofacitinib monotherapy compared withpatients on background MTX therapy [49].

Safety

In the Phase IIa monotherapy study, the 30 mg b.i.d. tofacitinib

group experienced a higher incidence of leukopenia, neutropenia,anemia, lymphopenia and thrombocytopenia than the othertreatment groups. An increase in infections was observed withhigher tofacitinib dosages (26, 25, 30 and 30% for placebo, 5, 15and 30 mg b.i.d. tofacitinib groups, respectively), but the majoritywere mild or moderate in severity and responded promptly totherapy. A dose response increase in the level of total cholesterol,low-density lipoprotein and high-density lipoprotein, and a decreasein the neutrophil count and hemoglobin were seen. There wereincreases in the blood EpsteinBarr virus DNA levels in all groups,including placebo (median increases of seven copies per 500 mgof DNA). The increases were largest in the 30 mg b.i.d. tofacitinib

group. Three patients experienced serious adverse events consideredrelated to the study drug (infectious gastroenteritis and severeleukopenia in patients receiving tofacitinib, and Staphylococcusaureuspneumonia in a patient receiving placebo) [40].

In the dose-ranging combination study, the most commonadverse events in the tofacitinib groups were urinary tractinfection, diarrhea, nasopharyngitis, arthralgia and headache [42].An increased incidence of infection in the tofacitinib groups wasobserved in comparison with placebo, but with no dose effect. Fiveserious infections with tofacitinib were observed during the study(three pneumonia, one respiratory tract infection and one urinarytract infection). There was one death in the tofacitinib 3 mg b.i.d.group, due to pneumonia followed by respiratory and cardiac failure.

Some increases in liver enzymes were seen, as well as increases incholesterol and a small increase in serum creatinine. Decreases inhemoglobin and neutrophils were observed in the tofacitinib groups.The 15 mg b.i.d. group reported the highest percentage of subjectswho discontinued treatment due to an adverse event.

The most common treatment-emergent adverse events inthe tofacitinib arms in the dose-ranging monotherapy studywere urinary tract infection, upper respiratory tract infection,nasopharyngitis, nausea, dizziness, diarrhea, headache andbronchitis [43]. Five patients experienced serious infectionsincluding pneumonia (n = 2, tofacitinib), pneumococcal sepsis(n = 1, tofacitinib), acute pyelonephritis (n = 1, after reassignment

from adalimumab to tofacitinib at week 12), and joint infection(n = 1, placebo). The tofacitinib 15 mg b.i.d. group had the highestfrequency of serious adverse events and severe adverse events; onedeath due to cerebrovascular accident was reported in this dosegroup. Dose-dependent increases in serum lipids and decreases inneutrophils levels were observed in the tofacitinib groups. Increasedlevels of serum creatinine and changes in hemoglobin were seenin all treatment groups. Elevations of liver enzymes were fewand similar in all study groups. The switch from adalimumab totofacitinib was, in general, well-tolerated.

In the Japanese combination study, the most commonlyreported adverse events were nasopharyngitis, increased alanine

transaminase, and increased aspartate transaminase [44]. The

proportion of patients reporting infections over 12 weeks was 10.7,29.6, 11.1 and 42.3% in tofacitinib 1-, 3-, 5- and 10-mg groups,respectively, compared with 21.4% for placebo. The most commoninfections were nasopharyngitis (8.3%), gastroenteritis (2.8%)and pharyngitis (1.9%). A significant dose-dependent decrease in

mean neutrophil counts was observed for all tofacitinib groups incomparison to placebo at week 12, but it did not result in therapydiscontinuation. Small changes in mean hemoglobin levels andincreases in serum creatinine and serum lipids were observed in thetofacitinib groups. Serious infections and death were not reported.

In the Phase III monotherapy study, changes in neutrophils,hemoglobin, serum creatinine, a lanine transaminase, aspartatetransaminase, and cholesterol occurred [45]. Twenty-five patients(4.1%) experienced serious adverse events. One death due tocardiac arrest and hyperkalemia in a patient who experienceddiarrhea occurred in the tofacitinib 10 mg b.i.d. group. No newpotential safety signals were detected.

In a Phase III combined therapy study in MTX inadequateresponders, the most frequent adverse events were infections andinfestations [46]. There were seven opportunistic infections, ofwhich three were serious. Four deaths were reported in tofacitnib5 mg b.i.d. group while tofacitinib 10 mg b.i.d. and placebo groupshad one death each reported. Laboratory abnormalities weresimilar to those reported in other tofacitinib studies.

In a Phase III combined therapy study in anti-TNF inadequateresponders, serious infections were reported in two patients ineach tofacitinib arm, and one patient in the placebo arm [47]. Noopportunistic infections were seen. One death due to pulmonaryembolism was reported in the placebo advanced to tofacitinib10 mg b.i.d. arm in a patient with known risk factors. Nonserious

adverse events and laboratory abnormalities were consistent withpreviously reported studies.

In the long-term open-label study, most frequently reportedadverse events were infections and infestations (18.4%),gastrointestinal disorders (10.2%) and laboratory abnormalities(7.4%) [48]. The most frequently reported serious adverse eventswere infections (2.62 per 100 patient-years experience) . Nosignificant difference in the safety profile was observed regardingthe use or not of concomitant MTX [49]. The most commontreatment-related adverse events in patients using MTX wereurinary tract infection (4.7%), bronchitis (4.0%) and sinusitis(3.6%), while in non-MTX patients they were upper respiratory

tract infection (2.5%), bronchitis (2.3%) and herpes zoster (2.2%).Liver laboratory test abnormalities were mild to moderate and morefrequent in the MTX combined group (mild in 3.6% and moderatein 2.6% in the MTX group).

In summary, according to integrated safety data, most commonadverse events observed with tofacitinb are infections, includingnasopharingitis, upper respiratory tract infection, urinary tractinfection, bronchitis, herpes zoster and influenza. Followinginfections, gastrointestinal disorders are the most common adverseevents [50,51].

In long-term extension studies up to 36 months, the incidencerate of serious adverse events was 11.34 per 100 patients-

years (95% CI: 10.2012.62), while the incidence rates of


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serious infections was 3.01 per 100 patients-years (95% CI:2.453.68) [50].

Most frequent laboratory abnormalities observed withtofacitinib are increase of creatinine and liver enzymes levels anddecrease of hemoglobin and neutrophils [50].

Conclusion

RA is a common inflammatory disease. After the initial diagnosis,treatment must be initiated as soon as possible; otherwise patientswill suffer from chronic joint pain, further functional disabilityand excess mortality. RA is a heterogeneous disease and responseto treatment is not predictable for many patients. Recently,translational research studies have led to new therapeutic targets butRA treatment is not satisfactory for more than a third of patients. IfMTX alone or in combination with other synthetic DMARDs doesnot control the disease, a biologic DMARD that targets TNF isusually added to the therapeutic regimen. Other biologic agents may

be used such as those targeting IL-1 receptor, IL-6 receptor, CD20B-cell antigen and T-cell activation surface antigens CD80 andCD86. These biologic drugs require intravenous or subcutaneousadministration, are very expensive and are not always effective.Tofacitinib, a new oral, potent and selective DMARD targetingthe intracellular JAK pathway, showed good results in Phase II andopen label studies as a therapeutic option for RA patients. Based onthese studies doses of 5 and 10 mg were selected for the Phase IIIprogramme named ORAL Trials. These Phase III trials includeevaluations of signs, symptoms, physical function, radiographicprogression and safety of this investigational drug when usedas monotherapy or combined with MTX or other DMARDs.Different RA patient populations will receive tofacitinib treatment

including MTX-naive patients and inadequate responders toMTX, other DMARDs and also to anti-TNF agents. Patients thatcompleted the Phase II trials and those completing the Phase IIIprogramme will continue to be evaluated in open-label ongoingextension studies that will help to determine the long-term efficacy,tolerability and safety of tofacitinib treatment in RA patients.

Expert commentary

The way rheumatologists see the treatment of RA has considerablychanged in the past 12 years. There is a worldwide consensus thatRA treatment must start very early and be effective in suppressingsynovitis without inducing undesirable adverse side effects. The

ultimate goal of an early and aggressive treatment of RA is to reachcomplete remission in order to have the greatest impact in preventingdamage and further disability. Biologic DMARDs contributedvery much to this new notion. In Phase II open-label studies,tofacitinib results in RA seemed to be noninferior to biologicaltherapies. Tofacitinib successfully suppressed disease activity andwas well tolerated in the initial clinical trials. This small-moleculeJAK inhibitor downregulates six inflammatory cytokines and seemsmore attractive as an inhibitor of the synovitis than the anti-TNFor anti-IL-6 compounds which are more specifically targeted.Tofacitinib, administrated as monotherapy or on background MTXtherapy, showed good safety and efficacy data in four randomized

Phase II trials. One of these studies also showed efficacy of a single

daily dosing (20 mg) of tofacitinib suggesting future trials with thisunique administration. The results of the Phase III monotherapytrial demonstrated, as early as week 2, significant ACR20 responserates for tofacitinib 5 and 10 mg b.i.d., as well as significant ACR50response rates for tofacitinib 10 mg b.i.d. and ACR70 response rates

for tofacitinib 5 and 10 mg b.i.d. These results are in the same rangeas biologic therapies particularly the anti-TNF therapies. In theopen-label extension trial efficacy was sustained for 24 months witha DAS change from 6.4 at open-label baseline to 3.55 at 24 months.Being an oral drug, tofacitinib will be easier to administer and willprobably have a better compliance than the injectable biologics.ORAL ongoing studies will give us a clue on how tofacitinib will beincluded in a new R A treatment strategy. Those trials will providemore information about tofacitinib administration as monotherapycompared with its administration on background MTX. There arealso current clinical studies in other indications including psoriasis,psoriatic arthritis, inflammatory bowel disease and prevention of

transplant rejection.The successful results obtained in the preclinical and clinicaltofacitinib trials showed that inhibition of the JAK family of enzymesis an effective means for modulation of the immune function as astrategy for treating RA and other autoimmune diseases.

Five-year view

Biochemistry and molecular biology made a huge contribution toour understanding of the pathogenic mechanisms involved in RA.The discovery and characterization of anticitrullinated proteinantibodies, the development of biologic drugs and the evolvingconcept that RA must be treated aggressively in its early stagesenormously changed the way rheumatologists see the disease today.

Pathways involved in the chronic phase of this disease are muchclearer than 10 years ago but there are still many questions regardingthe initiating cellular and molecular events leading to the synovitis.New studies are underway to better analyze the initiation ofautoimmunity in RA. Those include: T-cell tolerance breakdownearly in disease; T-cell cross-reaction activated by foreign antigenswith self-antigens (molecular mimicry) and; T-cell reaction toarticular neo-epitopes. Studies have shown that IgM rheumatoidfactor and anticitrullinated protein antibodies can be detectedin the serum of RA patients many years before the initiation ofclinical disease. Recently, one study showed that the synovium is notabnormal during this preclinical stage suggesting that autoimmunity

precedes the development of synovitis in individuals at risk forRA development [52]. These new data and the identification ofindividuals susceptible to the development of autoimmunitythrough the presence of specific MHC or other genetic factors willmake clinicians do a better diagnosis and a long-term prognosis evenbefore the first signs of an inflammatory arthritis.

The concept of making a good assessment of prognosis andperform a quick therapeutic action for an individual RA patienttoday represents a critical challenge to the rheumatologist. Newapproaches to the initial clinical investigation are being developedto more accurately define the prognosis of an early inflammatoryarthritis. A recent publication established ten recommendations

on how to investigate and follow-up in undifferentiated peripheral


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inflammatory arthritis. The 3E Initiative (Evidence, Expertise,Exchange) made a multinational effort to formulate practicalrecommendations for the everyday practice [53]. These will helpclinicians to discriminate between a benign course of the diseaseand a more severe illness associated with joint destruction and extra-

articular features. The recent 2010 ACR/EULAR classificationcriteria for RA, has been also developed with this purpose [22]. In thefuture rheumatologists will see the results of its universal application.

Another developing medical field to play an important role inthe future of rheumatology is the relation between treatment andindividual genetic variations. Efforts in this direction has been madeby studies in two areas of medical research: pharmacogenomics, theapplication of genomics to production of better drug design andbetter drug selection based on individual patients genetic profiles,and its branch pharmacogenetics, the relation between individualgenetic variations and his/her response to drug therapy. These newfields of investigation will help the rational individualization of

therapy using a genetic approach in the next few years.Inhibitors of signal transduction of the intracellular pathwaysof inflammation are now in development. We have reviewed the

first of these new drugs. Tofacitinib, a potent, orally active JAKinhibitor, showed rapid, statistically significant and clinicallymeaningful reductions in signs and symptoms of RA in patientsin Phase II and III trials. Tolerance was acceptable with mildto moderate side effects. In the initial trials tofacitinib showed

comparable results to anti-TNF therapy with the advantage ofbeing an oral drug and probably less expensive than the biologics.Studies currently underway will show us how this new class ofdrugs will fit in the treatment of RA and other rheumatic diseases.

Financial & competing interests disclosure

CAF Zerbini has received grants for Reseach from Merck, Pfizer, Amgen,

Lilly, Novartis, Sanofi-Aventis, Servier, GSK and Roche, has presented at

medical conferences for Pfizer, Merck, Sanofi-Aventis and Servier and is on

the board committees for Sanofi-Aventis, Pfizer and Merck. The authors

have no other relevant affiliations or financial involvement with any

organization or entity with a financial interest in or financial conflict with

the subject matter or materials discussed in the manuscript apart from thosedisclosed.

No writing assistance was utilized in the production of this manuscript.

Key issues

JAKs are a family of tyrosine kinases composed of four membrane-associated intracellular nonreceptor enzymes (JAK1, JAK2, JAK3

and Tyk2).

JAK3 is predominantly expressed at high levels in hematopoietic tissues, being found in myeloid cells, thymocytes, natural killer cells and

activated B and T lymphocytes. JAK3 binds to only one cytokine receptor, the common gchain or gc. This chain is shared by many

inflammatory cytokine receptors, including IL-2, IL-4, IL-7, IL-9, IL-15 and IL-21.

Tofacitinib is an oral selective and potent inhibitor of JAK1 and 3 capable of interfering with signaling through cytokine receptors of all the

cytokines listed above.

Tofacitinib is rapidly absorbed and eliminated with a time to peak concentration of approximately 0.5 h and a half-life of approximately 3 h.

The protein binding of tofacitinib is approximately 40%, raising the possibility of a low drug interaction due to drug displacement.

There is no need for dosage adjustment with coadministration of tofacitinib and methotrexate. Tofacitinib dosage adjustments or food

restrictions are not warranted during chronic treatment.

Tofacitinib administration showed significant anti-inflammatory effects in two rodent models of arthritis and animal models of

transplantation.

In a proof-of-concept monotherapy study, improvements in disease activity were observed as early as 1 week after treatment for all

tofacitinib groups (5, 15 and 30 mg two-times a day) in comparison to placebo. Increased American College of Rheumatology (ACR)50 and

ACR70 response rates relative to placebo were seen at all time points by week 4.

Three Phase IIb dose-ranging trials lasting from 6 to 24 weeks in RA patients showed significant ACR20 improvements as early as week 2

and sustained at week 24 in two studies. These studies led to the identification of the two-times a day doses now used in the Phase III trials.

A Phase III 6 month monotherapy study evaluated two doses of tofacitinib in 610 RA patients. The month 3 ACR20 response rates for

tofacitinib 5 and 10 mg two-times a day were significantly better than the placebo group responses.

Phase III studies in RA are included in a large clinical program called ORAL Trials. Additional results will be available soon. Dose-related increases in the number of adverse events were observed in the clinical trials. Common adverse events included headache,

nausea, upper respiratory infections, urinary tract infections, anemia, leukopenia, neutropenia and hypercholesterolemia.

Results from the RA studies show that there is potential for trials in other illnesses like psoriasis, inflammatory bowel diseases and organ

transplantation.

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First Phase II trial of tofacitinib treatment

in RA. The proof-of-concept monotherapy

study.

41 Coombs JH, Bloom BJ, Breedveld FC et al.Improved pain, physical functioning andhealth status in patients with rheumatoidarthritis treated with CP-690,550, an orallyactive Janus kinase (JAK) inhibitor: resultsfrom a randomized, double-blind, placebo-controlled trial.Ann. Rheum. Dis.69,413416 (2010).

42 Kremer JM, Cohen S, Wilkinson BE et al.A Phase IIb dose-ranging study of the oralJAK inhibitor tofacitinib (CP-690,550)versus placebo in combination withbackground methotrexate in patients withactive rheumatoid arthritis and aninadequate response to methotrexate alone.Arthriti s Rheum.64(4), 970981 (2012).

43 Fleischmann R, Cutolo M, Genovese MCet al.Phase IIb dose-ranging study of theoral JAK inhibitor tofacitinib (CP-690,550)or adalimumab monotherapy versusplacebo in patients with active rheumatoid

arthritis with an inadequate response todisease-modifying antirheumatic drugs.Arthriti s Rheum.64(3), 617629 (2012).

Study comparing American College of

Rheumatology 20 responses in tofacitinib

arm, adalimumab (anti-TNF) arm and

placebo arm of RA patients treatment.

44 Tanaka Y, Suzuki M, Nakamura Het al.Phase 2 study of tofacitinib (CP-690, 550)combined with methotrexate in patientswith rheumatoid arthritis and inadequateresponse to methotrexate.Arthriti s CareRes. (Hoboken)63(8), 11501158 (2011).

45 Fleischmann R, Kremer J, Cush Jet al.Phase 3 study of oral JAK inhibitortasocitinib (CP-690,550) monotherapy inpatients with active rheumatoid arthritis.Presented at:Annual Scientific Meeting ofthe American College of Rheumatology.

Atlanta, GA, USA, 611 November 2010(Abstract 4352).

46 van der Heijde D, Tanaka Y, FleischmannRet al. Tofacitinib (CP-690,550), an oraljanus kinase inhibitor, in combination withmethotrexate reduced the progression ofstructural damage in patients withrheumatoid arthritis: a 24-month Phase 3study.Arthriti s Rheum.63(S1017), 2592(2011) (Abstract).

First study to show inhibition of

structural damage with tofacitinib in

patients with RA.

47 Burmester G, Blanco R, Charles-Schoemann Cet al. Tofacitinib (CP-690,550), an oral janus kinase inhibitor, incombination with methotrexate, in patientswith active rheumatoid arthritis with aninadequate response to tumor necrosisfactor-inhibitors: a 6-month Phase 3 study.Arthriti s Rheum.63(S279), 718 (2011)(Abstract).

Study of tofacitinib in patients with

inadequate response to anti-TNF agents.

48 Connell CA, Riese RJ, Wood SPet al.Tasocitinib (CP-690,550), an orally

available selective janus kinase inhibitor,exhibits sustained safety and efficacy in thetreatment of rheumatoid arthritis over24 months.Artrhtis Rheum.62(S473),1129 (2010) (Abstract).

49 Connell CA, Riese RJ, Wood SPet al.Tasocitinib (CP-690,550) appears to beeffective and tolerated when administeredeither as long-term monotherapy or onbackground methotrexate in patients withrheumatoid arthritis.Arthriti s Rheum.62(S911), 2171 (2010) (Abstract).

50 Wollenhaupt J, Silverfield JC, Lee EBet al.Tofacitinib (CP-690,550), an oral januskinase inhibitor, in the treatment ofrheumatoid arthritis: open-label, long-termextension studies up to 36 months.ArthritisRheum.63(Suppl. 10), S152S153 (2011)

(Abstract 407).51 Cohen S, Radominski SC, Asavatanabodee

Pet al. Tofacitinib (CP-690,550), an oralJanus Kinase inhibitor: analysis ofinfections and all-cause mortality acrossPhase 3 and long-term extension studies inpatients with rheumatoid arthritis.Arthriti sRheum.63(Suppl. 10), S153 (2011)(Abstract 409).

52 van de Sande MGH, de Hair MJH, vander Leij C et al.Different stages ofrheumatoid arthritis: features of thesinovium in the preclinical phase.Ann.

Rheum. Dis.70, 772777 (2011). Paper showing that development of

autoimmunity may precede synovial

inammation suggesting a clue to

diagnosis before the appearance of clinical

symptoms.

53 Machado P, Castrejon I, Katchamart Wet al. Multinational evidence-basedrecommendations on how to investigateand follow-up undifferentiated peripheralinflammatory arthritis: integratingsystematic literature research and expertopinion of a broad international panel ofrheumatologists in the 3E Initiative.Ann.Rheum. Dis.70, 1524 (2011).

European initiative aimed to improve

clinicians investigation and follow-up of

arthritis at early stages of the disease. The

paper emphasizes the importance of early

discrimination between a benign course

and a more destructive disease.

54 Opar A. Kinase inhibitors attract attentionas oral rheumatoid arthritis drugs. Nat.Rev. Drug Discov.9(4), 257258 (2010).

55 Shuai K, Liu B. Regulation of JAKSTATsignalling in the immune system. Nat. Rev.

Immunol.3(11), 900911 (2003).

Websites

101 American College of Rheumatology.www.rheumatology.org

102 The European League AgainstRheumatism.www.eular.org

103 ClinicalTrials.gov.http://clinicaltrials.gov/ct2/results?term=CP+690+550+rheumatoid+arthritis

Documents

Expert Review of Clinical Immunology Volume 8 Issue 4 2012 [Doi 10.1586%2Feci.12.19] Zerbini, Cristiano AF; Lomonte, Andrea Barranjard Vannucci -- Tofacitinib for the Treatment of