Discovery of CP-690,550: a potent and selective Janus kinase (JAK) inhibitor for the treatment of autoimmune diseases and organ transplant rejection

Immunosuppression by co-stimulatory molecules: inhibition of CD2-CD48/CD58 interaction by peptides from CD2 to suppress progression of collagen-induced arthritis in mice

Targeting co-stimulatory molecules to modulate the immune response has been shown to have useful therapeutic effects for autoimmune diseases. Among the co-stimulatory molecules, CD2 and CD58 are very important in the early stages of generation of an immune response. Our goal was to utilize CD2-derived peptides to modulate protein-protein interactions between CD2 and CD58, thereby modulating the immune response. Several peptides were designed based on the structure of the CD58-binding domain of CD2 protein. Among the CD2-derived peptides, peptide 6 from the F and C β-strand region of CD2 protein exhibited inhibition of cell-cell adhesion in the nanomolar concentration range. Peptide 6 was evaluated for its ability to bind to CD58 in Caco-2 cells and to CD48 in T cells from rodents. A molecular model was proposed for binding a peptide to CD58 and CD48 using docking studies. Furthermore, in vivo studies were carried out to evaluate the therapeutic ability of the peptide to modulate the immune response in the collagen-induced arthritis (CIA) mouse model. In vivo studies indicated that peptide 6 was able to suppress the progression of CIA. Evaluation of the antigenicity of peptides in CIA and transgenic animal models indicated that this peptide is not immunogenic.

Tyrosine kinase inhibitors for the treatment of rheumatoid arthritis

Tyrosine kinases (TK) are enzymes capable of transferring phosphate groups to tyrosine residues in cytoplasmic proteins or the intracellular domains of transmembrane receptors. TK play critical roles in diverse biological functions including cellular processes such as adhesion, motility, proliferation, cell cycle control, cell death, as well as biological functions at the whole-organism level such as growth and development, metabolism or immune defense. TK inhibitors including spleen TK (fostamatinib) and Janus kinases (tofacitinib) inhibitors are two novel oral therapies that have demonstrated short-term good clinical responses in active rheumatoid arthritis patients with and inadequate responses to methotrexate or other traditional (non-biologic) disease-modifying antirheumatic drugs (DMARDs). Those responses are comparable to responses rates from pivotal trials of TNF inhibitors. TK inhibitors are generally well tolerated but not free of adverse effects. Several side effects had been described including gastrointestinal symptoms, neutropenia, hypertension, elevated liver function test and lipid alterations among others.

Owing to the limited duration of follow-up of patients treated with TK inhibitors, the long term safety profile of these drugs are unknown.

Fate of lymphocytes after withdrawal of tofacitinib treatment

Tofacitinib (Tofa) is an inhibitor of Janus Kinase 3, developed for the treatment of autoimmune diseases and for the prevention of transplant rejection. Due to its selective action on proliferating cells, Tofa can offer a way to block T cell activation, without toxic effects on resting cells. However, few studies have investigated the effects of Tofa on lymphocyte activation in vitro. Our aim was to study the action of Tofa on different lymphocyte subsets after in vitro stimulation and to track the behaviour of treated cells after interruption of the treatment. Peripheral blood lymphocytes were stimulated in vitro with mitogen and treated with two concentrations of Tofa. After a first period in culture, cells were washed and further incubated for an additional time. Lymphocyte subsets, activation phenotype and proliferation were assessed at the different time frames. As expected, Tofa was able to reduce the activation and proliferation of lymphocytes in the first four days of treatment. In addition the drug led to a relative decrease of Natural Killer, B cells and CD8 T cells compared to CD4 T cells. However, treated cells were still viable after the first period in culture and begun to proliferate, strikingly, in a dose dependent manner when the drug was removed from the environment by replacing the culture medium. This novel data does not necessarily predict a similar behaviour in vivo, but can warn about the clinical use of this drug when a discontinuation of treatment with Tofa is considered for any reason.

Design and synthesis of tricyclic JAK3 inhibitors with picomolar affinities as novel molecular probes

The Janus kinase (JAK) signaling pathway is of particular importance in the pathology of inflammatory diseases and oncological disorders, and the inhibition of Janus kinase 3 (JAK3) with small molecules has proven to provide therapeutic immunosuppression. A novel class of tricyclic JAK inhibitors derived from the 3-methyl-1,6-dihydrodipyrrolo[2,3-b:2',3'-d]pyridine scaffold was designed based on the tofacitinib-JAK3 crystal structure by applying a rigidization approach. A convenient synthetic strategy to access the scaffold via an intramolecular Heck reaction was developed, and a small library of inhibitors was prepared and characterized using in vitro biochemical as well as cellular assays. IC50 values as low as 220 pM could be achieved with selectivity for JAK3 over other JAK family members. Both activity and selectivity were confirmed in a cellular STAT phosphorylation assay, providing also first-time data for tofacitinib. Our novel inhibitors may serve as tool compounds and useful probes to explore the role of JAK3 inhibition in pharmacodynamics studies.

Tofacitinib: a review of its use in adult patients with rheumatoid arthritis

Tofacitinib (Xeljanz(®)) is the first approved drug in a new class of disease modifying antirheumatic drugs (DMARDs), the Janus kinase (JAK) inhibitors. JAKs have a pivotal role in triggering cytokine-induced signal transduction pathways that influence normal and pathological cellular processes of haematopoiesis and immune cell function, including pathogenic mechanisms involved in rheumatoid arthritis (RA). Selective inhibition of JAKs by tofacitinib potentially modulates inflammatory processes and provides a novel approach for the treatment of RA. Oral tofacitinib is indicated for the treatment of adult patients with active RA who have had an inadequate response to methotrexate and/or other DMARDs. In several large well designed trials, tofacitinib, in combination with methotrexate or other nonbiological DMARDs or as monotherapy, was an effective and generally well tolerated DMARD for the treatment of adult patients with moderately to severely active RA who had had an inadequate response to previous DMARDs, including tumour necrosis factor-α inhibitors. Direct head-to-head trials and/or further clinical experience (including long-term safety data), along with robust pharmacoeconomic studies, are required to more definitively position tofacitinib relative to other currently available DMARDs. In the meantime, tofacitinib (alone or in combination with nonbiological DMARDs) is an emerging option for the treatment of DMARD-experienced adult patients with moderately to severely active RA who have had an inadequate response to or are intolerant of methotrexate or other DMARDs.

Highly efficient iridium-catalyzed asymmetric hydrogenation of β-acylamino nitroolefins

A highly Ir-catalyzed enantioselective hydrogenation of β-acylamino nitroolefins is first reported, which provides straightforward access to chiral β-amino nitroalkanes in excellent enantioselectivities (up to >99.9% ee).

CP-690550 Treatment Ameliorates Established Disease and Provides Long-Term Therapeutic Effects in an SKG Arthritis Model

Although pathogenesis of human rheumatoid arthritis (RA) remains unclear, arthritogenic T cells and downstream signaling mediators have been shown to play critical roles. An increasing numbers of therapeutic options have been added for the effective control of RA. Nevertheless, there is still a category of patients that fails treatment and suffers from progressive disease. The recently developed immunosuppressant CP-690550, a small molecule JAK kinase inhibitor, has been implicated as an important candidate treatment modality for autoimmune arthritis. In this study, we evaluated the therapeutic effect of CP-690550 on established arthritis using an SKG arthritis model, a pathophysiologically relevant animal model for human RA. CP-690550 treatment revealed remarkable long-term suppressive effects on SKG arthritis when administered to the well-advanced disease (clinical score 3.5~4.0). The treatment effect lasted at least 3 more weeks after cessation of drug infusion, and suppression of disease was correlated with the reduced pro-inflammatory cytokines, including IL-17, IFN-γ, and IL-6 and increased level of immunoregulatory IL-10.

Novel treatment options for ulcerative colitis

The approved treatment options for patients with ulcerative colitis (UC) are currently limited to mesalamine or immunosuppressants. Patients who do not respond to mesalamine-based therapy can be treated with immunomodulators or anti-TNF antibody therapy. Failure or adverse reactions to these medications leaves the patient with little choice other than colectomy. However, novel insights into the pathogenic drivers of UC have led to new developments in drugs that promise clinical efficacy via modulation of targeted pathways. Given the impending expansion of therapeutic options for patients with UC, clinicians and researchers should be familiar with these mechanisms of action. In addition, the typical 'step-up' treatment paradigm for UC will likely need to be reshaped to allow for a more personalized approach to treating UC.

Tofacitinib prevents radiographic progression in rheumatoid arthritis

Tofacitinib, a novel Janus kinase inhibitor, may prevent structural damage in rheumatoid arthritis (RA). In this cohort study, we compared radiographic progression of hand joints between 21 RA patients who took tofacitinb for 18 months in a phase IIb and its extension study and 42 patients who took conventional disease modifying antirheumatic drugs (DMARDs), using simple erosion narrowing score. For tofacitinib group, changes before and after the treatment were also compared. The changes of erosion and sum scores were significantly less in tofacitinib than DMARDs group (for erosion, -0.60 ± 1.83 vs 0.51 ± 1.77, P = 0.038; for sum, -0.50 ± 1.72 vs 1.57 ± 4.13, P = 0.012). Joint space narrowing score (JSN) was also less in tofacitinib group (0.095 ± 0.58 vs 1.06 ± 2.60, P = 0.055). In tofacitinib group, yearly rates of both erosion and JSN were significantly decreased after administration of tofacitinib (For erosion, 0.62 ± 0.93 to -0.14 ± 0.48, P = 0.009; for JSN, 0.47 ± 0.64 to 0.03 ± 0.40, P = 0.032), as was change of sum score (1.09 ± 1.27 to -0.10 ± 0.63, P < 0.001). In conclusion, tofacitinib may prevent structural damage caused by RA.

tert-Butyl N-[(3R,4R)-1-(2-cyano-acet-yl)-4-methyl-piperidin-3-yl]-N-methyl-carbamate

The piperidine ring of the title compound, C15H25N3O3, adopts a slightly distorted chair conformation with the cis substituents displaying an N-C-C-C torsion angle of 43.0 (3)°. The cyano group (plane defined by C-C-C N atoms) is bent slightly out of the plane of the amide group by 13.3 (2)°. The carbamate group is oriented at a dihedral angle of 60.3 (5)° relative to the amide group.

Lead optimization of a 4-aminopyridine benzamide scaffold to identify potent, selective, and orally bioavailable TYK2 inhibitors

Herein we report our lead optimization effort to identify potent, selective, and orally bioavailable TYK2 inhibitors, starting with lead molecule 3. We used structure-based design to discover 2,6-dichloro-4-cyanophenyl and (1R,2R)-2-fluorocyclopropylamide modifications, each of which exhibited improved TYK2 potency and JAK1 and JAK2 selectivity relative to 3. Further optimization eventually led to compound 37 that showed good TYK2 enzyme and interleukin-12 (IL-12) cell potency, as well as acceptable cellular JAK1 and JAK2 selectivity and excellent oral exposure in mice. When tested in a mouse IL-12 PK/PD model, compound 37 showed statistically significant knockdown of cytokine interferon-γ (IFNγ), suggesting that selective inhibition of TYK2 kinase activity might be sufficient to block the IL-12 pathway in vivo.

Lead identification of novel and selective TYK2 inhibitors

A therapeutic rationale is proposed for the treatment of inflammatory diseases, such as psoriasis and inflammatory bowel diseases (IBD), by selective targeting of TYK2. Hit triage, following a high-throughput screen for TYK2 inhibitors, revealed pyridine 1 as a promising starting point for lead identification. Initial expansion of 3 separate regions of the molecule led to eventual identification of cyclopropyl amide 46, a potent lead analog with good kinase selectivity, physicochemical properties, and pharmacokinetic profile. Analysis of the binding modes of the series in TYK2 and JAK2 crystal structures revealed key interactions leading to good TYK2 potency and design options for future optimization of selectivity.

AG490 inhibits NFATc1 expression and STAT3 activation during RANKL induced osteoclastogenesis

Commonly, JAK/STAT relays cytokine signals for cell activation and proliferation, and recent studies have shown that the elevated expression of JAK/STAT is associated with the immune rejection of allografts and the inflammatory processes of autoimmune disease. However, the role which JAK2/STAT3 signaling plays in the receptor activator of nuclear factor-κB ligand (RANKL)-mediated osteoclastogenesis is unknown. In this study, we investigated the effects of AG490, specific JAK2 inhibitor, on osteoclast differentiation in vitro. AG490 significantly inhibited osteoclastogenesis in murine osteoclast precursor cell line RAW264.7 induced by RANKL. AG490 suppressed cell proliferation and delayed the G1 to S cell cycle transition. Furthermore, AG490 also suppressed the expression of nuclear factor of activated T cells (NFAT) c1 but not c-Fos in RAW264.7. Subsequently, we investigated various intracellular signaling components associated with osteoclastogenesis. AG490 had no effects on RANKL-induced activation of Akt, ERK1/2. Interestingly, AG490 partly inhibited RANKL-induced phosphorylation of Ser(727) in STAT3. Additionally, down-regulation of STAT3 using siRNA resulted in suppression of TRAP, RANK and NFATc1 expression. In conclusion, we demonstrated that AG490 inhibited RANKL-induced osteoclastogenesis by suppressing NFATc1 production and cell proliferation via the STAT3 pathway. These results suggest that inhibition of JAK2 may be useful for the treatment of bone diseases characterized by excessive osteoclastogenesis.

A pharmacokinetic and clinical assessment of tofacitinib for the treatment of rheumatoid arthritis

INTRODUCTION

Rheumatoid arthritis (RA) is a chronic painful and debilitating autoimmune disease. Although the outcome for patients with RA has improved markedly in the past decades, driven largely by the advent of biological disease-modifying antirheumatic drugs (DMARDs) and updated management strategies, adequate disease control cannot be achieved in a substantial proportion of patients. Since RA is a syndrome with different biological subsets, DMARDs, with a novel mechanism of action, may represent a valuable addition to the current armamentarium. Tofacitinib is a novel synthetic DMARD that selectively inhibits Janus kinases (JAKs), particularly JAK1 and JAK3.

AREAS COVERED

This review describes the pharmacokinetics of tofacitinib. Furthermore, the article summarizes and comments the drug's efficacy and safety profile in RA patients. The authors furthermore assess data derived from the FDA's RA development program.

EXPERT OPINION

Tofacitinib is an oral synthetic DMARD displaying linear pharmacokinetics. Metabolism, primarily mediated by CYP3A4, accounts for 70% of the total clearance of the drug; the remaining 30% are renally excreted. Tofacitinib monotherapy, or in combination with traditional DMARDs, has demonstrated its efficacy while having an acceptable safety profile in RA patients who have responded inadequately to current DMARDs, including TNF antagonists. In view of its undetermined benefit to risk ratio, in the real-world population, tofacitinib should, for now, only be prescribed to selected patients.

Targeting kinases: a new approach to treating inflammatory rheumatic diseases

After two decades of research and development activity focussed on orally active kinase inhibitors, the first such drug (the JAK inhibitor Xeljanz, tofacitinib) was approved by the FDA in November 2012 for the treatment of rheumatoid arthritis (RA). There is an intense activity in many companies both on expanding the utility of JAK inhibitors in other auto-immune indications and in discovering inhibitors of the JAK family with different and more selective profiles. Progress is also being made with orally active Syk inhibitors. One such inhibitor (fostamatinib) is currently in large-scale phase 3 trials, and there are others in clinical development. The last two to three years have been transformative for kinase inhibitors in auto-immune diseases, as several inhibitors have finally progressed beyond phase 2 trials after so many failures on other targets. Thus, there are new treatment options for RA patients beyond existing oral DMARDs and parenteral biologics.

Immunomodulating options for liver transplant patients

Much has changed since the early years of liver transplantation. Improvements in post-transplant survival are largely due to more selective and less toxic immunosuppression regimens and advances in operative and perioperative care. This has allowed liver transplantation to become an extremely successful treatment option for patients with endstage liver disease. Beginning with cyclosporine, a cyclic endecapeptide of fungal origin and the first of the calcineurin inhibitors to find widespread use, immunosuppressive regimens have evolved to include additional calcineurin inhibitors, steroids, mTOR inhibitors, antimetabolites and antibodies, mostly targeting T-cell activation. This review will present currently available immunosuppressive agents used in the perioperative period of liver transplantation, as well as maintenance treatments, tailoring therapeutic strategies for specific populations, and advances in immune monitoring and tolerance.

BD750, a benzothiazole derivative, inhibits T cell proliferation by affecting the JAK3/STAT5 signalling pathway

BACKGROUND AND PURPOSE

A series of benzothiazole derivatives were screened for immunosuppressive activity; of these compounds BD750 was found to be the most effective immunosuppressant. The purpose of the current study was to determine the immunosuppressive activity of BD750 on T cell proliferation and its potential mode of action.

EXPERIMENTAL APPROACH

T cell proliferation, CD25 and CD69 expression and cell cycle distribution were measured in vitro by flow cytometry. Cell viability was determined by CCK-8 assay. Cytokine levels were measured by elisa. The activation of signal-regulated molecules was assessed by Western blot analysis. The effects of BD750 were evaluated in vivo in a mouse model of delayed-type hypersensitivity.

KEY RESULTS

BD750 significantly inhibited mouse and human T cell proliferation, stimulated either by anti-CD3/anti-CD28 monoclonal antibodies or by an alloantigen, in a dose-dependent manner in vitro. No obvious cytotoxic effects of BD750 were observed in our experimental conditions. Furthermore, BD750 did not inhibit CD25 and CD69 expression or IL-2 and IL-4 secretion, but induced cell cycle arrest at the G(0) /G(1) phase in activated T cells. In IL-2-stimulated CTLL-2 cells and primary activated T cells, BD750 inhibited cell proliferation and STAT5 phosphorylation, but not Akt or p70S6K phosphorylation. BD750 also reduced the T cell-mediated delayed-type hypersensitivity response in mice in a dose-dependent manner.

CONCLUSION AND IMPLICATIONS

These data indicate that BD750 inhibits IL-2-induced JAK3/STAT5-dependent T cell proliferation. BD750 has the potential to be used as a lead compound for the design and development of new immunosuppressants for preventing graft rejection and treating autoimmune diseases.

Kurarinone regulates immune responses through regulation of the JAK/STAT and TCR-mediated signaling pathways

Sophora flavescens is a medicinal herb that contains flavonoids and quinolizidine alkaloids and has a wide range of biological activities due to its anti-inflammatory, anti-bacterial and anti-cancer properties. We isolated a series of flavonoids from the roots of Sophora flavescens and examined their ability to inhibit immune responses. Among the flavonoids, kurarinone exhibited the strongest inhibitory effect on immune responses. Kurarinone suppressed the differentiation of CD4(+) T cells by inhibiting the expression and production of T-cell lineage-specific master regulators and cytokines. Our results also demonstrated that kurarinone directly suppressed the cytokine-induced Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling and T-cell receptor (TCR) pathways. In two established animal models of chronic inflammatory skin disease, one in which psoriasis-like skin disease was induced by an interleukin 23 (IL-23) injection into mouse ears and another in which 2,4,6-trinitrochlorobenzene (TNCB) application on the abdomens of mice was used to induce contact dermatitis, kurarinone repressed disease development by inhibiting the expression of pro-inflammatory mediators, including cytokines, chemokines and enzyme in murine ear skin. This study provides new evidence that kurarinone may ameliorate chronic inflammatory skin diseases through the suppression of pathogenic CD4(+) T-cell differentiation and the overall immune response.

Efficient solution-phase synthesis of 4,5,7-trisubstituted pyrrolo[3,2-d]pyrimidines

We have developed an efficient and robust route to synthesize 4,5,7-trisubstituted pyrrolo[3,2-d]pyrimidines as potent kinase inhibitors. This solution-phase synthesis features a SNAr substitution reaction, cross-coupling reaction, one-pot reduction/reductive amination and N-alkylation reaction. These reactions occur rapidly with high yields and have broad substrate scopes. A variety of groups can be selectively introduced into the N5 and C7 positions of 4,5,7-trisubstituted pyrrolopyrimidines at a late stage of the synthesis, thereby providing a highly efficient approach to explore the structure-activity relationships of pyrrolopyrimidine derivatives. Four synthetic analogs have been profiled against a panel of 48 kinases and a new and selective FLT3 inhibitor 9 is identified.

3-Amido pyrrolopyrazine JAK kinase inhibitors: development of a JAK3 vs JAK1 selective inhibitor and evaluation in cellular and in vivo models

The Janus kinases (JAKs) are involved in multiple signaling networks relevant to inflammatory diseases, and inhibition of one or more members of this class may modulate disease activity or progression. We optimized a new inhibitor scaffold, 3-amido-5-cyclopropylpyrrolopyrazines, to a potent example with reasonable kinome selectivity, including selectivity for JAK3 versus JAK1, and good biopharmaceutical properties. Evaluation of this analogue in cellular and in vivo models confirmed functional selectivity for modulation of a JAK3/JAK1-dependent IL-2 stimulated pathway over a JAK1/JAK2/Tyk2-dependent IL-6 stimulated pathway.

JAK inhibitor tofacitinib for treating rheumatoid arthritis: from basic to clinical

Rheumatoid arthritis (RA) is a representative autoimmune disease characterized by chronic and destructive inflammatory synovitis. The multiple cytokines play pivotal roles in RA pathogenesis by inducing intracellular signaling, and members of the Janus kinase (JAK) family are essential for such signal transduction. An orally available JAK3 inhibitor, tofacitinib, has been applied for RA, with satisfactory effects and acceptable safety in multiple clinical examinations. From phase 2 dose-finding studies, tofacitinib 5 mg and 10 mg twice a day appear suitable for further evaluation. Subsequently, multiple phase 3 studies were carried out, and tofacitinib with or without methotrexate (MTX) is efficacious and has a manageable safety profile in active RA patients who are MTX naïve or show inadequate response to methotrexate (MTX-IR), disease-modifying antirheumatic drugs (DMARD)-IR, or tumor necrosis factor (TNF)-inhibitor-IR. The common adverse events were infections, such as nasopharyngitis; increases in cholesterol, transaminase, and creatinine; and decreases in neutrophil counts. Although the mode of action of tofacitinib remains unclear, we clarified that the inhibitory effects of tofacitinib could be mediated through suppression of interleukin (IL)-17 and interferon (IFN)-γ production and proliferation of CD4(+) T cells in the inflamed synovium. Taken together, an orally available kinase inhibitor tofacitinib targeting JAK-mediated signals would be expected to be a new option for RA treatment.

Pharmacodynamic analysis of tofacitinib and basiliximab in kidney allograft recipients

BACKGROUND

The common γ-chain (γ(c)) cytokines signal through the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway and play pivotal roles in lymphocyte activation. We investigated the effect of immunosuppressive drugs targeting this pathway, the JAK inhibitor tofacitinib (CP-690,550) and the anti-interleukin (IL)-2R antibody basiliximab, as part of a phase 2 study.

METHODS

After whole-blood activation with the γ(c) cytokines IL-2, IL-7, and IL-15, STAT5 phosphorylation was determined in T cells of de novo kidney transplantation patients treated with tofacitinib/basiliximab (n=5), calcineurin inhibitor (CNI) (cyclosporine A)/basiliximab (n=4) or CNI (tacrolimus)-based immunosuppression (n=6). The IC(50) for phosphorylated STAT (P-STAT) 5 inhibition by tofacitinib was determined in cytokine-activated CD4(+) and CD8(+) T cells from healthy individuals (n=4).

RESULTS

IC(50) was 26, 72, and 37 ng/mL for IL-2, IL-7, and IL-15 activation, in CD4(+) T cells, respectively; and 35, 61, and 76 ng/mL for IL-2, IL-7, and IL-15 activation, in CD8(+) T cells, respectively. In kidney transplantation patients, 7 days after starting tofacitinib/basiliximab treatment, cytokine-induced P-STAT5 was inhibited in CD4(+) T cells (92% for IL-2 activation, 60% for IL-7, and 75% for IL-15), which persisted for the 2-month study period. In contrast, CNI/basiliximab treatment did not affect IL-7-activated or IL-15-activated P-STAT5; only IL-2-activated P-STAT5 was reduced by 77% on day 7 and recovered to pretreatment levels within 2 months. CD8(+) T cells showed a comparable profile to CD4(+) T cells. P-STAT5 was not inhibited in CNI-treated control patients.

CONCLUSIONS

Tofacitinib therapy strongly inhibits γ(c) cytokine-induced JAK/STAT5 activation, whereas basiliximab suppresses IL-2-stimulated activation only. Pharmacodynamic monitoring offers a unique tool to evaluate the biologic effects of immunosuppressive drugs.

Tofacitinib for the treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disease that affects approximately 1% of the worldwide population. It primarily targets the synovial membrane of joints, leading to a synovial proliferation, joint cartilage lesion and erosions in the adjacent bone tissue. The disease is usually progressive and if the inflammatory process is not adequately suppressed, joint deformity takes place, leading to a significant functional disability and work incapacity. Over the last decade, biological therapy was established as a major step towards disease control in those patients who experienced failure after treatment with disease-modifying antirheumatic drugs. 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 of these agents limited because of adverse events. As such, the search for new molecules with a higher 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 studies in arthritis and transplantation animal models are reviewed as a background for the possible use of tofacitinib treatment in humans. Four Phase II (one A and three B dose-ranging) trials lasting from 6 to 24 weeks in RA patients showed significant American College of Rheumatology 20 improvements as early as week 2 and sustained at week 24 in two studies. Tofacitinib Phase III studies in RA are included in a clinical program called 'ORAL Trials'. Long-term follow-up from ongoing studies will contribute to a more accurate tofacitinib efficacy and safety profile. Trials in other illness such as psoriasis, psoriatic arthritis, renal transplant rejection prevention, inflammatory bowel diseases and dry eye are underway.

Tofacitinib, an oral Janus kinase inhibitor, in active ulcerative colitis

BACKGROUND

Ulcerative colitis is a chronic inflammatory disease of the colon for which current treatments are not universally effective. One additional treatment may be tofacitinib (CP-690,550), an oral inhibitor of Janus kinases 1, 2, and 3 with in vitro functional specificity for kinases 1 and 3 over kinase 2, which is expected to block signaling involving gamma chain-containing cytokines including interleukins 2, 4, 7, 9, 15, and 21. These cytokines are integral to lymphocyte activation, function, and proliferation.

METHODS

In a double-blind, placebo-controlled, phase 2 trial, we evaluated the efficacy of tofacitinib in 194 adults with moderately to severely active ulcerative colitis. Patients were randomly assigned to receive tofacitinib at a dose of 0.5 mg, 3 mg, 10 mg, or 15 mg or placebo twice daily for 8 weeks. The primary outcome was a clinical response at 8 weeks, defined as an absolute decrease from baseline in the score on the Mayo scoring system for assessment of ulcerative colitis activity (possible score, 0 to 12, with higher scores indicating more severe disease) of 3 or more and a relative decrease from baseline of 30% or more with an accompanying decrease in the rectal bleeding subscore of 1 point or more or an absolute rectal bleeding subscore of 0 or 1.

RESULTS

The primary outcome, clinical response at 8 weeks, occurred in 32%, 48%, 61%, and 78% of patients receiving tofacitinib at a dose of 0.5 mg (P=0.39), 3 mg (P=0.55), 10 mg (P=0.10), and 15 mg (P<0.001), respectively, as compared with 42% of patients receiving placebo. Clinical remission (defined as a Mayo score ≤2, with no subscore >1) at 8 weeks occurred in 13%, 33%, 48%, and 41% of patients receiving tofacitinib at a dose of 0.5 mg (P=0.76), 3 mg (P=0.01), 10 mg (P<0.001), and 15 mg (P<0.001), respectively, as compared with 10% of patients receiving placebo. There was a dose-dependent increase in both low-density and high-density lipoprotein cholesterol. Three patients treated with tofacitinib had an absolute neutrophil count of less than 1500.

CONCLUSIONS

Patients with moderately to severely active ulcerative colitis treated with tofacitinib were more likely to have clinical response and remission than those receiving placebo. (Funded by Pfizer; ClinicalTrials.gov number, NCT00787202.).

Tofacitinib or adalimumab versus placebo in rheumatoid arthritis

BACKGROUND

Tofacitinib (CP-690,550) is a novel oral Janus kinase inhibitor that is being investigated for the treatment of rheumatoid arthritis.

METHODS

In this 12-month, phase 3 trial, 717 patients who were receiving stable doses of methotrexate were randomly assigned to 5 mg of tofacitinib twice daily, 10 mg of tofacitinib twice daily, 40 mg of adalimumab once every 2 weeks, or placebo. At month 3, patients in the placebo group who did not have a 20% reduction from baseline in the number of swollen and tender joints were switched in a blinded fashion to either 5 mg or 10 mg of tofacitinib twice daily; at month 6, all patients still receiving placebo were switched to tofacitinib in a blinded fashion. The three primary outcome measures were a 20% improvement at month 6 in the American College of Rheumatology scale (ACR 20); the change from baseline to month 3 in the score on the Health Assessment Questionnaire-Disability Index (HAQ-DI) (which ranges from 0 to 3, with higher scores indicating greater disability); and the percentage of patients at month 6 who had a Disease Activity Score for 28-joint counts based on the erythrocyte sedimentation rate (DAS28-4[ESR]) of less than 2.6 (with scores ranging from 0 to 9.4 and higher scores indicating greater disease activity).

RESULTS

At month 6, ACR 20 response rates were higher among patients receiving 5 mg or 10 mg of tofacitinib (51.5% and 52.6%, respectively) and among those receiving adalimumab (47.2%) than among those receiving placebo (28.3%) (P<0.001 for all comparisons). There were also greater reductions in the HAQ-DI score at month 3 and higher percentages of patients with a DAS28-4(ESR) below 2.6 at month 6 in the active-treatment groups than in the placebo group. Adverse events occurred more frequently with tofacitinib than with placebo, and pulmonary tuberculosis developed in two patients in the 10-mg tofacitinib group. Tofacitinib was associated with an increase in both low-density and high-density lipoprotein cholesterol levels and with reductions in neutrophil counts.

CONCLUSIONS

In patients with rheumatoid arthritis receiving background methotrexate, tofacitinib was significantly superior to placebo and was numerically similar to adalimumab in efficacy. (Funded by Pfizer; ORAL Standard ClinicalTrials.gov number, NCT00853385.).

JAK inhibition for the treatment of rheumatoid arthritis: a new era in oral DMARD therapy

INTRODUCTION

In rheumatoid arthritis (RA) there is a significant medical need for safe and effective oral disease-modifying anti-rheumatic drugs (DMARDs) for patients who respond inadequately to methotrexate, the first-line therapy in RA. Oral agents targeting Janus-associated kinases (JAKs) are the most promising new agents in clinical development. This review describes the preclinical and clinical activities of the most advanced JAK inhibitors with different JAK selectivity profiles.

AREAS COVERED

This review first describes the current treatment landscape and the pathophysiology of RA. Role for cytokines in the disease pathogenesis followed by significance of JAK/STAT pathway in cytokine signaling are discussed. Available chemical description and enzymatic data on the most advanced JAK inhibitors in clinical development are provided. Preclinical and clinical results that are publicly available are summarized. Review of literature was conducted using National Library of Medicine (NLM) database, 'PubMed'. In addition, all publicly disclosed data from companies that are developing the JAK inhibitors was researched to obtain the most up-to-date information of the compounds discussed in this report.

EXPERT OPINION

Emerging clinical results demonstrate that JAK inhibition is a validated new mechanism for the development of oral DMARD agents that is likely to join the armamentarium against RA in the near future.

Discovery of the macrocycle (9E)-15-(2-(pyrrolidin-1-yl)ethoxy)-7,12,25-trioxa-19,21,24-triaza-tetracyclo[18.3.1.1(2,5).1(14,18)]hexacosa-1(24),2,4,9,14(26),15,17,20,22-nonaene (SB1578), a potent inhibitor of janus kinase 2/fms-like tyrosine kinase-3 (JAK2/FLT3) for the treatment of rheumatoid arthritis

Herein, we describe the synthesis and SAR of a series of small molecule macrocycles that selectively inhibit JAK2 kinase within the JAK family and FLT3 kinase. Following a multiparameter optimization of a key aryl ring of the previously described SB1518 (pacritinib), the highly soluble 14l was selected as the optimal compound. Oral efficacy in the murine collagen-induced arthritis (CIA) model for rheumatoid arthritis (RA) supported 14l as a potential treatment for autoimmune diseases and inflammatory disorders such as psoriasis and RA. Compound 14l (SB1578) was progressed into development and is currently undergoing phase 1 clinical trials in healthy volunteers.

Current landscape for T-cell targeting in autoimmunity and transplantation

In recent years, substantial advances in T-cell immunosuppressive strategies and their translation to routine clinical practice have revolutionized management and outcomes in autoimmune disease and solid organ transplantation. More than 80 diseases have been considered to have an autoimmune etiology, such that autoimmune-associated morbidity and mortality rank as third highest in developed countries, after cardiovascular diseases and cancer. Solid organ transplantation has become the therapy of choice for many end-stage organ diseases. Short-term outcomes such as patient and allograft survival at 1 year, acute rejection rates, as well as time course of disease progression and symptom control have steadily improved. However, despite the use of newer immunosuppressive drug combinations, improvements in long-term allograft survival and complete resolution of autoimmunity remain elusive. In addition, the chronic use of nonspecifically targeted immunosuppressive drugs is associated with significant adverse effects and increased morbidity and mortality. In this article, we discuss the current clinical tools for immune suppression and attempts to induce long-term T-cell tolerance induction as well as much-needed future approaches to produce more short-acting, antigen-specific agents, which may optimize outcomes in the clinic.