Visilizumab

T cells play a pivotal role in the immune response underlying inflammatory bowel disease (IBD) pathogenesis. On this basis, over the past 25 years several drugs have assessed to target T cells in IBD patients. Amongst anti-CD3 antibodies, visilizumab and foralumab did not show clinical efficacy in ulcerative colitis (UC) and Crohn's disease (CD) patients, respectively, whereas otelixizumab has been tested in vitro only. The anti-CD4 BF-5 and cM-T412, and the anti-CD25 basiliximab and daclizumab were not effective in CD and UC patients, respectively. The anti-NKG2D antibody NNC0142-0002 showed clinical benefit in CD patients, in particular in biologic naïve ones, in a randomized, double-blind, parallel-group, placebo-controlled trial. The anti-CD40L M90 and the GSK1349571A blocking calcium release-activated calcium (CRAC) channels, which are involved in the T cell activation and proliferation, were tested only in ex vivo/in vitro experiments. Apart from ustekinumab, all the other drugs targeting T cell-derived cytokines failed. The reinduction of lamina propria T cell apoptosis is a mechanism to modulate T cell survival exploited by cyclosporin A, azathioprine and anti-tumor necrosis factor-α agents, such as infliximab, adalimumab and golimumab. In this article, we review the drugs targeting T cells via surface receptors, via T cell-derived cytokines, via CRAC channels or by inducing apoptosis.

Effective GvHD prevention after T-cell-replete, HLA-mismatched transplant is needed and has incentivized alternative approach development.¹.CD3-specific antibodies induce immunotolerance by rapidly clearing pathogenic T cells and promoting tolerance by sparing regulators.².Their success in exptl. GvHD prevention, human autoimmune disease treatment and post-transplant rejection has established the basis to test visilizumab for GvHD prophylaxis in humans.^3, 4.Visilizumab (Abbott), an anti-CD3 monoclonal Ab with T-cell-receptor partial agonist ligand function, enhances activation-induced cell death (AICD), leading to T-cell apoptosis.^5, 6.We reasoned that visiluzimab, with safety and biol. activity previously described in clin. studies of glucocorticoid-resistant GvHD treatment,^3, 4 could prevent GvHD by depleting activated T cells, yet allow immune reconstitution.Here, we report results from our prospective pilot trial using visilizumab for GvHD prevention in combination with tacrolimus (from day +4 at 0.02 mg/kg per day) and methotrexate (day +1 at 15 mg/m² and then at 10 mg/m² on days +3, +6 and +11) after unrelated donor allogeneic hematopoietic cell transplant (HCT) mismatched for 1 or 2 HLA-A, -B, -C or DRB1 loci.We used a Simon two-stage clin. trial design planned for 15 patients in stage 1.If serious toxicities were >2% (defined as grade 4/5 reaction to visiluzimab, HHV6 encephalitis, or PTLD within 100 days or any grade 4/5 adverse event unexpected with HCT) and <20% had GvHD grade 3/4, patients would proceed to stage 2, with groups randomized 1:1 with ATG or visiluzimab (30 per group).A G-CSF-mobilized peripheral blood CD34+ cell dose per kg of 5-10 × 10⁶ was used to minimize high-risk rejection compared with bone marrow.Conditioning regimen included fludarabine (40 mg/m² over 4 days) and busulfan (145 mg/m² IV over 4 days) to a steady-state concentration of 900±100 ng/mL (AUC of 5300±500 μmol/min).Prophylaxis with foscarnet (60 mg/kg per day on day +1 until ANC >500) followed by ganciclovir (5 mg/kg per day from ANC >500 to day+100 if CMV-pos. or to day +42 if CMV-neg.) or valganciclovir (900 mg/day orally from ANC >500 if able to tolerate oral administration) days +2 to +42 was used.⁷ Eight patients (six women, two men) were enrolled (median age 46 years; range, 23-50).Three patients had AML, two had ALL, one had MDS, one had follicular NHL and one had severe aplastic anemia, with HLA-mismatched 6/8 (n=2) or 7/8 (n=6).We hypothesized that visilizumab ≥2000 ng/mL might be optimal to prevent GvHD.A single 3 mg/m² visilizumab dose immediately resulted in goal levels³ in the first 7 patients.Visilizumab depleted blood T cells for <14 days.Using a non-compartmental ELISA with a murine anti-M291 monoclonal Ab (PDL, Fremont, CA, USA), we determined mean maximal concentration (±s.d.) at 1-2 h of 1564±428 ng/mL and terminal half-life of 157±48 h (Figure 1a).We surmised that repeated Ab administration was necessary to produce T lymphopenia for >14 days.Patient-8 received four 3 mg/m² doses on days 0, 3, 10 and 17 before premature study closure due to lack of efficacy,⁸ and a two-compartment model was used to analyze that patient's pharmacokinetics (Figure 1b).All 8 patients had similar maximal concentration and alpha half-life parameter estimates; however, patient-8 showed a prolonged beta half-life (335 vs 187 h for multiple vs single dose) and a significantly slower clearance rate (0.02 vs 0.05 L/h for multiple vs single dose).Visiluzimab infusion toxicity was CTC grade 1-2 in six patients and grade 3 in two patients.Median time to neutrophil engraftment was reached in 14 days (12-17 days) and median time to platelet engraftment was 11.5 days (10-22 days) with >95% donor chimerism at day 30.The cumulative incidence of grade II-IV acute GvHD score at 100 days was 100%, with six having grade I-II and two having grade III-IV.Median onset of GvHD was 14 days (range, 7-21).Seven patients developed protracted acute overlapping with chronic GVHD, three having mild-to-moderate and four having severe.Chronic GvHD affected the skin (n=5), gut (n=4) and lung (n=2).Two patients were alive after median of 2818 days (2831-2806 days) and 6 died after median of 197 days (150-643 days) due to GvHD with or without infection.Prophylaxis resulted in no CMV reactivation.Six patients had EBV reactivation that responded to rituximab.Flow cytometry showed that visilizumab resulted in immediate and fast clearance of CD4+ and CD8+ lymphocytes, followed by a gradual count recovery at days 14-28 post transplant, which could explain the poor results (Figure 2a).T-regulatory cells were detected as early as day 28 but did not translate to a pos. outcome; CD56+/CD16+ cell recovery occurred by day +30 and CD19+ cells steadily fell after HCT (Figure 2a).The proportion of host-reactive interferon-γ-producing cells measured by ELISPOT was significantly increased vs. donor control at day 90 post-HCT (P=0.030) (Figure 2b).We used either PMA/Iono polyclonal stimulation or APCs from a third-party donor as pos.-stimulation controls.The Th17 lineage, measured by IL-17 production in ELISPOT supernatants at day 90, suggested increased IL-17 production by donor-derived host-reactive Th17 cells (P=0.4) (Figure 2c).We detected significantly increased IL-10 but not TGF-β production at day 90 post HCT by host-reactive donor-derived T cells (P=0.03) (Figure 2c).EBV-specific CD8+ T cells were measured by tetramers in five HLA-A*0201 patients with pos.-EBV serol. pre-HCT, with pos.-EBV DNA titers shown post-HCT (limit of detection ≤0.6 cells/μL).By day 90 post HCT, 4/5 patients had detectable EBV-specific CD8+ T cells measured with phycoerythrin (PE)-HLA-A*0201 EBV (GLCTLVAML) peptide, indicating persistence after visilizumab, although this did not translate to EBV reactivation prevention.CMV-specific CD8+ T cells measured with PE-HLA-A*0201 CMV PP65 (QYDPVAALF) peptide were undetectable in the two HLA-A*0201-pos. patients.Flow cytometry anal. of the CD4+ TCR repertoire using 25 anti-Vβ monoclonal antibodies showed minimal if any skewing from the normal donor repertoire, suggesting polyclonal alloresponse (data not shown).Here, visilizumab prior to methotrexate and tacrolimus was ineffective in preventing GvHD after HLA-mismatched unrelated transplant compared with other established prophylaxis methods.Tacrolimus was initiated at day +4 to avoid calcineurin blockade as delayed administration is effective in other settings.^9, 10.Although there was no GvHD liver involvement, all 8 patients developed acute GvHD of the gut and skin.Immune endpoint failure was observed as residual Th1, and possibly Th17 responses against host were still identified.Despite dose accumulation observed with multi-dose visilizumab, we observed intolerable GvHD, warranting no further testing.Drug interactions that could account for results are calcineurin inhibitors inhibiting T-cell AICD by down-modulation of CD95L,¹¹ glucocorticoids preventing cytokine release, and/or methotrexate, preventing division of T cells required for subsequent AICD.¹².CD3-specific antibodies are promising modalities, but challenges remain for universal clin. use as effectiveness depends on numerous variables.CD3-specific antibodies have been able to halt active autoimmunity in mice but have been less effective in preventing disease, suggesting different mechanisms of actions according to disease state.Furthermore, results depend on administration route/dose, with i.v. formulations more suitable for active autoimmune disease and oral formulations more potent for disease prevention.¹³.Immunosuppressive pharmacol. interactions in preclin. models are warranted, and primate models have been developed since our trial was conceived and may contribute to better trial design.¹⁴.We cannot exclude that a potential beneficial effect of anti-CD3 therapy may have been counteracted by concomitant immunosuppressive drugs and/or this intervention may not be effective in GvHD prevention as opposed to GvHD treatment.