Measuring Serum Vedolizumab and Vedolizumab Antibodies: Comparison of Commercial Assays with the Vedolizumab Clinical Development Assay.

BACKGROUND: Vedolizumab (VDZ) is an anti-α 4 ß 7 integrin monoclonal antibody approved for inflammatory bowel disease treatment. VDZ serum and antidrug antibody (ADA) concentrations may be used for treatment optimization. In this article, the results of 5 commercial assays (Grifols, Immundiagnostik, Progenika, Sanquin, and Theradiag) measuring VDZ concentration and ADA were compared with those of the reference assays used in VDZ clinical studies. Our findings will assist clinicians in interpreting commercial assay results in the context of VDZ clinical trial data. METHODS: VDZ-treated patient samples were used to evaluate the agreement between commercial assays and the reference VDZ serum concentration assay, based on linear regression, Bland-Altman, and qualitative agreement analyses. VDZ ADAs were detected using qualitative assays. Specificity, selectivity, accuracy, and precision were assessed using serum samples from healthy donors or patients with IBD (VDZ serum concentration <0.5 mcg/mL) spiked with VDZ, with/without other biologics (identical sample sets per assay). RESULTS: All assays were specific and selective for VDZ. Overall, the commercial assay results for VDZ-spiked samples correlated well with those of the reference serum concentration assay (R 2 ≥ 0.98). Compared with the Immundiagnostik and Theradiag assays, the Grifols, Sanquin, and Progenika assays had the best reference assay agreement (based on regression analysis, Bland-Altman plots, and qualitative agreement [Cohen's kappa ≥0.92]). All immunogenicity assays detected VDZ ADAs; only the reference assay detected VDZ ADAs in the presence of 15 mcg/mL VDZ, advising caution with commercial ADA assays if VDZ is present. CONCLUSIONS: All 5 commercial assays are suitable for VDZ therapeutic monitoring and ADA testing. However, the absolute values from the reference assays and the different commercial assays were not comparable, indicating that the same assay must be used for repeated monitoring of VDZ serum concentrations.

The Evolving Landscape of Biomarkers in Celiac Disease: Leading the Way to Clinical Development.

Celiac disease is a common immune-mediated disease characterized by abnormal T-cell responses to gluten. For many patients, symptoms and intestinal damage can be controlled by a gluten-free diet, but, for some, this approach is not enough, and celiac disease progresses, with serious medical consequences. Multiple therapies are now under development, increasing the need for biomarkers that allow identification of specific patient populations and monitoring of therapeutic activity and durability. The advantage of identifying biomarkers in celiac disease is that the underlying pathways driving disease are well characterized and the histological, cellular, and serological changes with gluten response have been defined in gluten challenge studies. However, there is room for improvement. Biomarkers that measure histological changes require duodenal biopsies and are invasive. Less invasive peripheral blood cell and cytokine biomarkers are transient and dependent upon gluten challenge. Here, we discuss established biomarkers and new approaches for biomarkers that may overcome current limitations.

TAK-101 Nanoparticles Induce Gluten-Specific Tolerance in Celiac Disease: A Randomized, Double-Blind, Placebo-Controlled Study.

BACKGROUND & AIMS: In celiac disease (CeD), gluten induces immune activation, leading to enteropathy. TAK-101, gluten protein (gliadin) encapsulated in negatively charged poly(dl-lactide-co-glycolic acid) nanoparticles, is designed to induce gluten-specific tolerance. METHODS: TAK-101 was evaluated in phase 1 dose escalation safety and phase 2a double-blind, randomized, placebo-controlled studies. Primary endpoints included pharmacokinetics, safety, and tolerability of TAK-101 (phase 1) and change from baseline in circulating gliadin-specific interferon-γ-producing cells at day 6 of gluten challenge, in patients with CeD (phase 2a). Secondary endpoints in the phase 2a study included changes from baseline in enteropathy (villus height to crypt depth ratio [Vh:Cd]), and frequency of intestinal intraepithelial lymphocytes and peripheral gut-homing T cells. RESULTS: In phase 2a, 33 randomized patients completed the 14-day gluten challenge. TAK-101 induced an 88% reduction in change from baseline in interferon-γ spot-forming units vs placebo (2.01 vs 17.58, P = .006). Vh:Cd deteriorated in the placebo group (-0.63, P = .002), but not in the TAK-101 group (-0.18, P = .110), although the intergroup change from baseline was not significant (P = .08). Intraepithelial lymphocyte numbers remained equal. TAK-101 reduced changes in circulating α4ß7+CD4+ (0.26 vs 1.05, P = .032), αEß7+CD8+ (0.69 vs 3.64, P = .003), and γδ (0.15 vs 1.59, P = .010) effector memory T cells. TAK-101 (up to 8 mg/kg) induced no clinically meaningful changes in vital signs or routine clinical laboratory evaluations. No serious adverse events occurred. CONCLUSIONS: TAK-101 was well tolerated and prevented gluten-induced immune activation in CeD. The findings from the present clinical trial suggest that antigen-specific tolerance was induced and represent a novel approach translatable to other immune-mediated diseases. ClinicalTrials.gov identifiers: NCT03486990 and NCT03738475.

A Phase I, Randomized, Double-Blind, Placebo-Controlled, Single-Dose and Multiple-Rising-Dose Study of the BTK Inhibitor TAK-020 in Healthy Subjects.

Bruton's tyrosine kinase (BTK) is a target for treatment of hematologic malignancies and autoimmune diseases. TAK-020 is a highly selective covalent BTK inhibitor that inhibits both B cell receptor and fragment crystallizable receptor signaling. We assessed the safety/tolerability and pharmacokinetics/pharmacodynamics (PDs) of TAK-020 in healthy subjects. Each cohort of the single-rising dose (n = 72; 9 cohorts) and the multiple-rising dose (n = 48; 6 cohorts) portions of the study comprised six TAK-020-treated and two placebo-treated, subjects aged 18-55 years (inclusive). The PD effects were assessed by measuring BTK occupancy and the inhibition of fragment crystallizable epsilon receptor 1 (FcεRI)-mediated activation of basophils. Overall, treatment-emergent adverse events (TEAEs) were similar to placebo; there were no serious TEAEs or no TEAEs leading to discontinuation. TAK-020 was rapidly absorbed (median time to maximum plasma concentration (Tmax ) 45-60 minutes) with a half-life of ~ 3-9 hours at doses ≥ 2.5 mg. TAK-020 exposure was generally dose proportional for single doses ≤ 70 mg and after multiple doses of ≤ 60 mg once daily. Target occupancy was dose dependent, with doses ≥ 2.5 mg yielding maximum and sustained occupancy > 70% for > 96 hours. Single doses ≥ 4.4 mg reduced FcεRI-mediated activation of basophils by > 80% and comparable inhibition was observed with daily dosing ≥3.75 mg for 9 days. Inhibition persisted for 24-72 hours postdose and the duration generally increased with dose. TAK-020 was generally well-tolerated in healthy subjects after single and multiple doses and demonstrated target engagement and pathway modulation. The PD effects outlasted drug exposures, as expected for covalent inhibition of BTK.

Development and validation of a high-parameter mass cytometry workflow to decipher immunomodulatory changes in celiac disease.

The advent of time-of-flight mass cytometry (CyTOF) has enabled high dimensional and unbiased examination of the immune system to simultaneous interrogate a multitude of parameters and gain a better understanding of immunologic data from clinical trial samples. Here we describe the development and validation of a 33-marker mass cytometry workflow for measuring gastrointestinal (GI) trafficking peripheral blood mononuclear cells (PBMCs) in patients with celiac disease (CeD). This panel builds upon identification of well-characterized immune cells and expands to include markers modulated in response to gluten challenge in patients with CeD. The CeD panel was optimized and validated according to accepted industry practice for validation of flow cytometry assays and builds upon established sample processing workflows for mass cytometry studies. Several critical parameters were evaluated during the assay development phase of this study including optimization of the sample processing steps, antibody specificity, and ensuring the panel as a whole performed to expectation. The panel was then validated using a fit-for-purpose approach tailored to the intended use of the data in the clinical trial. Validation included assessment of analytical parameters essential to understanding the reliability and robustness of the CeD panel such as intra-assay precision, inter-assay precision, inter-operator precision and sample processing stability. Together, this validated mass cytometry workstream provides robust and reproducible high-dimensional analysis of human peripheral blood immune cells to characterize patient samples from clinical trials.

Evaluating Responses to Gluten Challenge: A Randomized, Double-Blind, 2-Dose Gluten Challenge Trial.

BACKGROUND & AIMS: Gluten challenge is used to diagnose celiac disease (CeD) and for clinical research. Sustained gluten exposure reliably induces histologic changes but is burdensome. We investigated the relative abilities of multiple biomarkers to assess disease activity induced by 2 gluten doses, and aimed to identify biomarkers to supplement or replace histology. METHODS: In this randomized, double-blind, 2-dose gluten-challenge trial conducted in 2 US centers (Boston, MA), 14 adults with biopsy-proven CeD were randomized to 3 g or 10 g gluten/d for 14 days. The study was powered to detect changes in villous height to crypt depth, and stopped at planned interim analysis on reaching this end point. Additional end points included gluten-specific cluster of differentiation (CD)4 T-cell analysis with HLA-DQ2-gluten tetramers and enzyme-linked immune absorbent spot, gut-homing CD8 T cells, interleukin-2, symptoms, video capsule endoscopy, intraepithelial leukocytes, and tissue multiplex immunofluorescence. RESULTS: All assessments showed changes with gluten challenge. However, time to maximal change, change magnitude, and gluten dose-response relationship varied. Villous height to crypt depth, video capsule endoscopy enteropathy score, enzyme-linked immune absorbent spot, gut-homing CD8 T cells, intraepithelial leukocyte counts, and HLA-DQ2-restricted gluten-specific CD4 T cells showed significant changes from baseline at 10 g gluten only; symptoms were significant at 3 g. Symptoms and plasma interleukin-2 levels increased significantly or near significantly at both doses. Interleukin-2 appeared to be the earliest, most sensitive marker of acute gluten exposure. CONCLUSIONS: Modern biomarkers are sensitive and responsive to gluten exposure, potentially allowing less invasive, lower-dose, shorter-duration gluten ingestion. This work provides a preliminary framework for rational design of gluten challenge for CeD research. ClinicalTrials.gov number, NCT03409796.

Safety, tolerability, pharmacokinetics and pharmacodynamics of the anti-CD38 cytolytic antibody TAK-079 in healthy subjects.

AIMS: This investigation characterised tolerability, pharmacokinetics and pharmacodynamics of the anti-CD38 antibody TAK-079. METHODS: A randomised, double-blind, placebo-controlled trial of a single intravenous (i.v.) infusion or subcutaneous (s.c.) injection of TAK-079 at escalating doses in healthy subjects (n = 74), who were followed for 92 days postexposure. RESULTS: TAK-079 was well tolerated. All adverse events were mild or moderate. There were no withdrawals, infusion, or injection site reactions over the tested i.v. and s.c. doses up to 0.06 and 0.6 mg kg-1 , respectively. At higher doses, transient cytokine level increases, following i.v. administration, coincided with reduction in CD38-expressing cells; clinical symptoms included mild pyrexia, headache, and postural hypotension. Following an i.v. infusion of 0.06 mg kg-1 TAK-079, maximum observed serum concentration (Cmax ) was 100.4 (%CV: 52) ng mL-1 , time to Cmax was the end of infusion and natural killer (NK_ cells were reduced 93.8 (±8.5) % from baseline levels. Following a s.c. injection of 0.6 mg kg-1 TAK-079, Cmax was 23.0 (%CV: 67) ng mL-1 with time to Cmax of 24 (range 7.98-96.02) hours, and plasmablasts were subsequently reduced 93.4 (±8.8) % from predose levels. Serum immunoglobulin (Ig)M, IgA and IgG levels were reduced by 15-60% and had not returned to baseline levels within 78 days after administration at ≥0.3 mg kg-1 s.c. Reductions in NK cells at 0.6 mg kg-1 s.c. were approximately 2-3 times more durable than at 0.06 mg kg-1 i.v. CONCLUSIONS: TAK-079 was well tolerated and s.c. administration elicited more durable reductions in plasmablasts and NK cells. This plasmacytolytic profile could be useful for treating disorders caused by plasma or NK cells, malignant counterparts, and/or pathogenic antibodies.

Decreased circulating CXCR3 + CCR9+T helper cells are associated with elevated levels of their ligands CXCL10 and CCL25 in the salivary gland of patients with Sjögren's syndrome to facilitate their concerted migration.

CCR9 + T helper (Th) cells can induce Sjögren-like symptoms in mice and both CCR9 + Th cells and their ligand CCL25 are increased in the salivary glands of primary Sjögren's syndrome (pSS) patients. Increased circulating CCR9 + Th cells are present in pSS patients. CCR9 + Th cells are hyperresponsive to IL-7, secrete high levels of IFN-γ, IL-21, IL-17 and IL-4 and potently stimulate B cells in both patients and healthy individuals. Our aim was to study co-expression of chemokine receptors on CCR9 + Th cells and whether in pSS this might differentially affect CCR9 + Th cell frequencies. Frequencies of circulating CCR9 + and CCR9- Th cells co-expressing CXCR3, CCR4, CCR6 and CCR10 were studied in pSS patients and healthy controls. CCL25, CXCL10, CCL17, CCL20 and CCL27 mRNA and protein expression of salivary gland tissue of pSS and non-Sjögren's sicca (non-SS) patients was assessed. Chemotaxis assays were performed to study migration induced by CXCL10 and CCL25. Higher expression of CXCR3, CCR4 and CCR6 but not CCR10 was observed on CCR9 + Th cells as compared to cells lacking CCR9. Decreased frequencies of circulating memory CCR9 + CXCR3+ Th cells were found in pSS patients, which was most pronounced in the effector memory subset. Increased salivary gland CCL25 and CXCL10 expression significantly correlated and both ligands functioned synergistically based on in vitro induced chemotaxis. Decreased memory CXCR3 + CCR9+ Th cells in blood of pSS patients may be due to a concerted action of overexpressed ligands at the site of inflammation in the salivary glands facilitating their preferential migration and positioning in the lymphocytic infiltrates.

A Reduction in B, T, and Natural Killer Cells Expressing CD38 by TAK-079 Inhibits the Induction and Progression of Collagen-Induced Arthritis in Cynomolgus Monkeys.

Ectoenzyme CD38 is increased on lymphocytes in response to an antigenic challenge and it is hypothesized that targeting these activated lymphocytes could ameliorate pathologic activities in autoimmune diseases. The cynomolgus monkey is an appropriate model for assessing potential effects of targeting CD38 in humans because these species exhibit similar expression profiles. TAK-079 is a human monoclonal antibody (IgG1 λ ) that binds to CD38 and lyses bound cells by complement-dependent cytotoxicity and antibody-dependent cell-mediated cytotoxicity. TAK-079 binds to monkey CD38 with an affinity at EC50 4.5 nM, and the potential activity of TAK-079 was investigated in a monkey collagen-induced arthritis model of autoimmune disease. Prophylactic administration of TAK-079 (3 mg/kg i.v. weekly) was well tolerated and prevented arthritis development compared with vehicle-treated control animals, which exhibited progressive disease with radiographic damage and worsening clinical scores over the study course. Therapeutic treatment of arthritic monkeys with TAK-079 (3 mg/kg i.v. weekly) was also well tolerated and reduced disease progression and symptoms. Arthritis scores and joint swelling were significantly lower than the vehicle control, accompanied by decreases in blood levels of C-reactive protein, alkaline phosphatase, and natural killer, B, and T cells. Histopathology, morphometry, and radiology revealed significantly less joint damage in animals exposed prophylactically to TAK-079 treatment compared with vehicle-treated animals and significantly less damage in animals treated therapeutically with TAK-079 or dexamethasone (0.1 mg/kg oral gavage daily), illustrating potential disease-modifying activity. In conclusion, these data indicate that depletion of CD38-expressing cells could be a therapeutic mechanism for treating autoimmune diseases. SIGNIFICANCE STATEMENT: This study demonstrates that targeting CD38-expressing leukocytes with a cytolytic antibody can ameliorate autoimmune disease in cynomolgus monkeys. The study gives a unique perspective into this therapeutic strategy because the three other anti-CD38 cytolytic antibodies in clinical development (daratumumab, isatuximab, and MOR202) cannot be tested in similar models because they do not crossreact with CD38 expressed by new world primates.

Pharmacokinetics and pharmacodynamics of the cytolytic anti-CD38 human monoclonal antibody TAK-079 in monkey - model assisted preparation for the first in human trial.

We are studying the fully human, IgG1λ cytolytic monoclonal antibody TAK-079, which binds CD38. CD38 is expressed on plasma and natural killer (NK) cells constitutively and upregulated on subsets of B and T lymphocytes upon activation. TAK-079 cross-reacts with CD38 expressed by cynomolgus monkeys and depletes subsets of NK, B, and T cells. Therefore, safety and function of TAK-079 was evaluated in this species, prior to clinical development, using bioanalytical, and flow cytometry assays. We pooled the data from eight studies in healthy monkeys (dose range 0.03-100 mg/kg) and developed mathematical models that describe the pharmacokinetics and the exposure-effect relationship for NK cells, B cells, and T cells. NK cell depletion was identified as the most sensitive pharmacodynamic effect of TAK-079. It was adequately described with a turnover model (C50  = 27.5 µg/mL on depletion rate) and complete depletion was achieved with an IV dose of 0.3 mg/kg. Intermediate effects on T-cell counts were described with a direct response model (C50  = 11.9 µg/mL) and on B-cell counts with a 4-transit-compartment model (C50  = 19.8 µg/mL on depletion rate). Our analyses substantiate the observation that NK, B and T cells are cleared by TAK-079 at different rates and required different time spans to replete the blood compartment. The models were used to simulate pharmacokinetic and cell depletion profiles in humans after applying a straightforward scaling approach for monoclonal antibodies in preparation for the first-in-human clinical trial.

Increased CCL25 and T Helper Cells Expressing CCR9 in the Salivary Glands of Patients With Primary Sjögren's Syndrome: Potential New Axis in Lymphoid Neogenesis.

OBJECTIVE: Follicular helper T (Tfh) cells play a critical role in germinal center formation and B cell activation, both of which are hallmarks of primary Sjögren's syndrome (SS). CCR9-expressing T helper cells have "Tfh-like" characteristics and their numbers are increased at mucosa-associated sites in several inflammatory conditions. Because the characteristics of these cells are unique and evaluation has been limited, this study was undertaken to investigate the local and systemic CCL25/CCR9 axis in patients with primary SS. METHODS: Levels of CCL25 protein and messenger RNA (mRNA) and CCR9+ T helper cells were evaluated in the labial salivary glands (LSGs) of patients with primary SS and patients with sicca syndrome without a diagnosis of primary SS (non-SS sicca controls). CCL25 levels were assessed for correlation with parameters of inflammation and clinical features. Circulating CCR9+ and CXCR5+ T helper cells were compared on the basis of phenotypic and functional properties. RESULTS: CCL25 protein and mRNA levels were elevated in the LSGs of patients with primary SS as compared to non-SS sicca controls. Increased levels of CCL25 were associated with B cell hyperactivity, autoimmunity, and levels of interleukin-21 (IL-21) and soluble IL-7 receptor α-chain (IL-7Rα). Furthermore, the frequency of CCR9-expressing cells in the LSGs was increased and levels of circulating CCR9+ T helper cells expressing programmed death 1 and inducible T cell costimulator were elevated in patients with primary SS. CCR9+ T helper cells displayed higher expression of IL-7Rα and secreted higher levels of interferon-γ, IL-17, IL-4, and IL-21 as compared to CXCR5+ T helper cells, ex vivo and upon triggering with antigen or IL-7. Both CCR9+ and CXCR5+ T helper cells induced IgG production by B cells more potently than that induced in the cultures with CCR9-CXCR5- T helper cells. CONCLUSION: Enhanced expression of CCL25 in LSGs of patients with primary SS can facilitate attraction of CCR9+ T helper cells, and these cells secrete high levels of proinflammatory cytokines when triggered with antigen or IL-7. The observed associations with B cell hyperactivity, autoimmunity, and markers of lymphoid neogenesis indicate that the CCL25/CCR9 axis plays a significant role in the immunopathology of primary SS, suggesting that this axis could represent a novel therapeutic target for the disease.

BTNL8, a butyrophilin-like molecule that costimulates the primary immune response.

The role of the B7 family molecules in the regulation of the immune response is well documented. A large body of experimental evidence indicates that costimulatory molecules such as B7-1, B7-2, B7-DC, B7-H1, B7-H2, B7-H3 and B7-H4 are critical for initiation, maintenance and down-regulation of the immune response. However the immunological function of butyrophilin (BTN)-like molecules, which are a part of the expanded B7 family, is not known. Here, we demonstrate that the extracellular portion of human BTNL8 can augment Ag-induced activation of T lymphocytes. BTNL8 has two alternatively spliced forms: B7-like and BTN-like. Both isoforms of BTNL8 were expressed concurrently in various human tissues. A putative BTNL8 receptor was detected only on resting T lymphocytes. Administration of BTNL8Ig fusion protein into mice promoted production of Ag-specific IgG during the primary, but not the secondary immune responses. BTNL8 may therefore play an essential role in priming of naïve T lymphocytes.

PDGF-D inhibition by CR002 ameliorates tubulointerstitial fibrosis following experimental glomerulonephritis.

BACKGROUND: Arresting or regressing kidney scarring is of major clinical relevance. Platelet-derived growth factor D (PDGF-D) is widely expressed in fibrotic kidneys. Administration of the PDGF-D neutralizing fully human monoclonal antibody CR002 in the acute phase of progressive anti-Thy 1.1 glomerulonephritis reduced glomerular and secondary tubulointerstitial damage. METHODS: Using this model, we now assessed the effects of CR002 (n=15) vs irrelevant control IgG (n=17) administered on days 17, 28 and 35 after disease induction, i.e. after acute glomerular damage had subsided. RESULTS: In vitro, CR002 inhibited the PDGF-D- but not the PDGF-B-induced proliferation of rat renal fibroblasts. Following the first CR002 injection on day 17, exposure to therapeutic levels was maintained until day 49. Proteinuria in the CR002-treated group was transiently reduced between days 49 and 77 (-19 to -23% in comparison with the controls; P<0.05). On day 100, CR002 treatment reduced the number of rats that had doubled their serum creatinine (CR002: 40 vs controls: 71%; P<0.05). Compared with controls, the CR002 animals, on day 100, significantly lowered glomerular expression of vimentin and collagens as well as tubulointerstitial damage scores, interstitial fibrosis, vimentin and cortical PDGF-D mRNA levels. CONCLUSIONS: PDGF-D antagonism, even after the phase of acute glomerular damage, exerts beneficial effects on the course of tubulointerstitial damage, i.e. the final common pathway of most renal diseases.

Antagonism of PDGF-D by human antibody CR002 prevents renal scarring in experimental glomerulonephritis.

Glomerular mesangial cell proliferation and/or matrix accumulation characterizes many progressive renal diseases. PDGF-D was identified recently as a novel mediator of mesangial cell proliferation in vitro and in vivo. This study investigated the long-term consequences of PDGF-D inhibition in vivo. Rats with progressive mesangioproliferative glomerulonephritis (uninephrectomy plus anti-Thy-1.1 antibody) received the PDGF-D-neutralizing, fully human mAb CR002 on days 3, 10, and 17 after disease induction. Glomerular mesangioproliferative changes on day 10 were significantly reduced by anti-PDGF-D treatment as compared with control antibody. Eight weeks after disease induction, anti-PDGF-D therapy significantly ameliorated focal segmental glomerulosclerosis, podocyte damage (de novo desmin expression), tubulointerstitial damage, and fibrosis as well as the accumulation of renal interstitial matrix including type III collagen and fibronectin. Treatment with anti-PDGF-D also reduced the cortical infiltration of monocytes/macrophages on day 56, possibly related to lower renal cortical complement activation (C5b-9 deposition) and/or reduced epithelial-to-mesenchymal transition (preserved cortical expression of E-cadherin and reduced expression of vimentin and alpha-smooth muscle actin). In conclusion, these data provide evidence for a causal role of PDGF-D in the pathogenesis of renal scarring and point to a new therapeutic approach to progressive mesangioproliferative renal disease.

Inhibition of in vitro and in vivo T cell responses by recombinant human Tim-1 extracellular domain proteins.

Members of the T cell, Ig domain and mucin domain (Tim) family of proteins have recently been implicated in the control of T cell-mediated immune responses. Tim-1 (HUGO designation HAVCR1) polymorphisms have been linked to the regulation of atopy in mice and humans, suggestive of a role in immune regulation. Tim-1 is expressed upon activation of T cells. In concert with the increased expression of Tim-1, a binding partner for the extracellular domain of Tim-1 (eTim-1) was induced on activated T cells, and mRNA expression data was consistent with the binding partner being Tim-4. We found that co-immobilized recombinant eTim-1 was able to inhibit T cell activation mediated by CD3 + CD28 mAb. eTim-1 mediated its inhibitory effects on proliferation by arresting cell cycle at G(0)/G(1) phase through regulation of cell cycle proteins. In vivo, administration of eTim-1 proteins led to a decrease in both ear (contact hypersensitivity to oxazolone) and joint (methylated BSA antigen-induced arthritis) swelling. The inhibitory activity of eTim-1 in the T(h)1-dependent models was evidence that eTim-1 is able to modulate T cell responses. Manipulation of the Tim-1 interaction with its binding partner on T cells may therefore provide a novel target for therapeutic intervention in T cell-mediated diseases.