Cell Costimulation Blockade Research Articles

Retinal microvascular alterations in patients with active rheumatoid arthritis without cardiovascular risk factors: the potential effects of T cell co-stimulation blockade.

The evaluation of microvascular alterations might provide clinically useful information for patients with an increased cardiovascular (CV) risk, such as those with rheumatoid arthritis (RA), being the small artery remodeling the earliest form of target organ damage in primary CV diseases, such as arterial hypertension. The evaluation of retinal arterioles is a non-invasive technique aimed to identify an early microvascular damage, represented by the increase of the wall-to-lumen ratio (WLR) index. Abatacept (ABA), a T-cell co-stimulator blocker, is used to treat RA. A CV protective action was hypothesized for its peculiar mechanism of action in the modulation of T-cells, potentially involved in the pathogenesis of CV comorbidity. The study aimed to non-invasively investigate morphological characteristics of retinal arterioles in a cohort of RA patients treated with ABA. Seventeen RA patients [median (25th-75thpercentile) age = 58 (48-64) years, baseline 28-joint Disease Activity Score DAS28-C-reactive protein (DAS28-CRP) = 4.4 (3.9-4.6), body mass index (BMI) = 24.2 (23.4-26) kg/m2, rheumatoid factor positive:52.9%, anti-citrullinated peptide autoantibodies positive:76.5%] without known CV risk factors (arterial hypertension, diabetes, hypercholesterolemia, previous CV events, smoking) were evaluated by the adaptive optics imaging system of retinal arterioles before and every 6 months of therapy with ABA (T0, T6 and T12). Office blood pressure evaluation, 24-h ambulatory blood pressure monitoring and tissue-doppler echocardiography were also performed. A progressive significant reduction of the WLR of retinal arterioles was observed [T0 = 0.28 (0.25-0.30), T6 = 0.27 (0.24-0.31), T12 = 0.23 (0.23-0.26); p T0 vs. T6 = 0.414; p T6 vs. T12 = 0.02; p T0 vs. T12 = 0.009], without significant variations in other parameters. The T0-T12 reduction of WLR was correlated with that of DAS28-CRP (r:0.789; p = 0.005). Moreover, a significant reduction of diastolic office blood pressure and a trend for reduction of daily pressure measured by ambulatory monitoring were observed. In a cohort of RA patients without known CV risk factors, a reduction of retinal microvascular alterations was demonstrated after treatment for 12 months with ABA, in parallel with the reduction of disease activity. These results might suggest the possibility of microvascular abnormalities regression induced by the immune system modulation.

Effectiveness of combined plasma cell therapy and costimulation blockade based desensitization regimen in heart transplant candidates.

Desensitization is one of the strategies to reduce antibodies and facilitate heart transplantation in highly sensitized patients. We describe our center's desensitization experience with combination of plasma cell (PC) depletion therapy (with proteasome inhibitor or daratumumab) and costimulation blockade (with belatacept). We reviewed five highly sensitized patients who underwent desensitization therapy with plasma cell depletion and costimulation blockade. We evaluated the response to therapy by measuring the changes in cPRA, average MFI, and number of positive beads>5000MFI. Five patients, mean age of 56 (37-66) years with average cPRA of 98% at 5000 MFI underwent desensitization therapy. After desensitization, mean cPRA decreased from 98% to 70% (p=.09), average number of beads>5000 MFI decreased from 59 to 37 (p=.15), and average MFI of beads>5000 MFI decreased from 16713 to 13074 (p=.26). Combined PC depletion and CoB could be a reasonable strategy for sustained reduction in antibodies in highly sensitized patients being listed for heart transplantation.

Early allogeneic immune modulation after establishment of donor hematopoietic cell-induced mixed chimerism in a nonhuman primate kidney transplant model.

Mixed lymphohematopoietic chimerism is a proven strategy for achieving operational transplant tolerance, though the underlying immunologic mechanisms are incompletely understood. A post-transplant, non-myeloablative, tomotherapy-based total lymphoid (TLI) irradiation protocol combined with anti-thymocyte globulin and T cell co-stimulatory blockade (belatacept) induction was applied to a 3-5 MHC antigen mismatched rhesus macaque kidney and hematopoietic cell transplant model. Mechanistic investigations of early (60 days post-transplant) allogeneic immune modulation induced by mixed chimerism were conducted. Chimeric animals demonstrated expansion of circulating and graft-infiltrating CD4+CD25+Foxp3+ regulatory T cells (Tregs), as well as increased differentiation of allo-protective CD8+ T cell phenotypes compared to naïve and non-chimeric animals. In vitro mixed lymphocyte reaction (MLR) responses and donor-specific antibody production were suppressed in animals with mixed chimerism. PD-1 upregulation was observed among CD8+ T effector memory (CD28-CD95+) subsets in chimeric hosts only. PD-1 blockade in donor-specific functional assays augmented MLR and cytotoxic responses and was associated with increased intracellular granzyme B and extracellular IFN-γ production. These studies demonstrated that donor immune cell engraftment was associated with early immunomodulation via mechanisms of homeostatic expansion of Tregs and early PD-1 upregulation among CD8+ T effector memory cells. These responses may contribute to TLI-based mixed chimerism-induced allogenic tolerance.

Systemic Administration of Acazicolcept, a Dual CD28 and Inducible T cell Costimulator Inhibitor, Ameliorates Experimental Autoimmune Uveitis.

Combined inhibition of CD28 and inducible T cell costimulator (ICOS) pathways with acazicolcept (ALPN-101) represents a potential new treatment for uveitis. Here, we evaluate preclinical efficacy using experimental autoimmune uveitis (EAU) in Lewis rats. Efficacy was tested in 57 Lewis rats treated with either systemic (subcutaneous) or local (intravitreal) administration of acazicolcept and compared to treatment with a matched Fc-only control or corticosteroid. Impact of treatment on uveitis was assessed using clinical scoring, optical coherence tomography (OCT), and histology. Ocular effector T cell populations were determined using flow cytometry, and multiplex ELISA used to measure aqueous cytokine concentrations. When compared to Fc control treatment, systemic acazicolcept led to statistically significant decreases in clinical score (P < 0.01), histologic score (P < 0.05), and number of ocular CD45+ cells (P < 0.01). Number of ocular CD4+ and CD8+ T cells expressing IL-17A+ and IFNγ+ were also decreased with statistical significance (P < 0.01). Similar results were achieved with corticosteroids. Intravitreal acazicolcept decreased inflammation scores when compared to untreated fellow eyes and to Fc control treated eyes, although not statistically significant. Systemic toxicity, measured by weight loss, occurred in the corticosteroid-treated, but not in the acazicolcept-treated animals. Systemic treatment with acazicolcept statistically significantly suppressed EAU. Acazicolcept was well-tolerated without the weight loss associated with corticosteroids. Acazicolcept may be an effective alternative to corticosteroids for use in treating autoimmune uveitis. Additional studies are needed to clarify the optimal dose and route for use in humans. We show that T cell costimulatory blockade could be an effective mechanism for treating uveitis.

556 - Immunogenetic Determinants of Relapse and Non-Relapse Mortality Following Haploidentical HCT with Ptcy and T Cell Costimulation Blockade with Abatacept

556 - Immunogenetic Determinants of Relapse and Non-Relapse Mortality Following Haploidentical HCT with Ptcy and T Cell Costimulation Blockade with Abatacept

Abatacept-based Graft-Versus-Host Disease Prophylaxis in Haplo-identical Hematopoietic Cell Transplant in a High-risk Cohort.

There is insufficient guidance in using posttransplant cyclophosphamide in patients with organ dysfunctions. Abatacept (Aba), a T cell costimulation blockade, has recently been shown to prevent severe acute graft-versus-host disease (GVHD). We report adding Aba as GVHD prophylaxis in 4 pediatrics patients who received haplo-hematopoietic cell transplantation. Two patients had grade 2 acute GVHD and 2 had mild chronic GVHD. All 4 patients are alive with full donor chimerism, and 3 are off immunosuppressants. An Aba-based regimen can result in reliable engraftment and acceptable GVHD when concerns of organ dysfunction prevents the use of posttransplant cyclophosphamide in haplo-hematopoietic cell transplantation.

A human CD137\xd7PD-L1 bispecific antibody promotes anti-tumor immunity via context-dependent T cell costimulation and checkpoint blockade

Immune checkpoint inhibitors demonstrate clinical activity in many tumor types, however, only a fraction of patients benefit. Combining CD137 agonists with these inhibitors increases anti-tumor activity preclinically, but attempts to translate these observations to the clinic have been hampered by systemic toxicity. Here we describe a human CD137xPD-L1 bispecific antibody, MCLA-145, identified through functional screening of agonist- and immune checkpoint inhibitor arm combinations. MCLA-145 potently activates T cells at sub-nanomolar concentrations, even under suppressive conditions, and enhances T cell priming, differentiation and memory recall responses. In vivo, MCLA-145 anti-tumor activity is superior to immune checkpoint inhibitor comparators and linked to recruitment and intra-tumor expansion of CD8 + T cells. No graft-versus-host-disease is observed in contrast to other antibodies inhibiting the PD-1 and PD-L1 pathway. Non-human primates treated with 100 mg/kg/week of MCLA-145 show no adverse effects. The conditional activation of CD137 signaling by MCLA-145, triggered by neighboring cells expressing >5000 copies of PD-L1, may provide both safety and potency advantages.

Imaging Tolerance Induction in Neonatal Mice: Hierarchical Interplay Between Allogeneic Adult and Neonatal Immune Cells.

In Medawar's murine neonatal tolerance model, injection of adult semiallogeneic lymphohematopoietic cells (spleen cells [SC] and bone marrow cells [BMC]) tolerizes the neonatal immune system. An eventual clinical application would require fully allogeneic (allo) cells, yet little is known about the complex in vivo/in situ interplay between those cells and the nonconditioned neonatal immune system. To this end, labeled adult SC and BMC were injected into allogeneic neonates; interactions between donor and host cells were analyzed and modulated by systematic depletion/inactivation of specific donor and host immune effector cell types. Consistent with effector cell compositions, allo-SC and allo-SC/BMC each induced lethal acute graft-versus-host disease, whereas allo-BMC alone did so infrequently. CD8 T cells from SC inoculum appeared naïve, while those of BMC were more memory-like. Age-dependent, cell-type dominance defined the interplay between adult donor cells and the neonatal host immune system such that if the dominant adult effector type was removed, then the equivalent neonatal one became dominant. Depletion of donor/host peripheral T cells protected against acute graft-versus-host disease and prolonged heart allograft survival; peripheral CD8 T-cell depletion together with CD4 T cell-costimulation blockade induced more robust tolerance. This comprehensive study provides direct observation of the cellular interplay between allogeneic donor and host immune systems, adds to our previous work with semiallogeneic donor cells, and provides important insights for robust tolerance induction. Induction of transplant tolerance in neonates will likely require "crowd sourcing" of multiple tolerizing cell types and involve depletion of immune effector cells with costimulation blockade.

T Cell Costimulation Blockade with Abatacept Nearly Eliminates Early Severe Acute Graft Versus Host Disease after HLA-Mismatched (7/8 HLA Matched) Unrelated Donor Transplant, with a Favorable Impact on Disease-Free and Overall Survival

HLA mismatched unrelated donor (MMURD) HCT plays a critical role in the treatment of high-risk hematologic malignancies in ethnic minorities and others lacking a fully matched donor. However, the high incidence of severe (Grade III-IV) acute GVHD (AGVHD) and resultant mortality remain critical barriers to success. T cell costimulation blockade with CTLA4-Ig has been demonstrated to potently inhibit T cell activation, and is FDA-approved for rheumatoid arthritis and renal transplant. We previously completed a pilot study adding 4 doses of the ‘abatacept’ formulation of CTLA4-Ig to calcineurin inhibitor (CNI) + methotrexate (MTX) GVHD prophylaxis in URD HCT (BBMT 19:1638-49, 2013). Based on robust immune reconstitution and a low rate of AGVHD, we initiated a multicenter phase II trial of abatacept (10 mg/kg/dose, Days -1, +5, +14, +28) plus CNI/MTX (‘ABA2‘) in patients undergoing URD HCT (Clinicaltrials.gov # NCT01743131).ABA2 has 2 cohorts: (1) 8/8 URD (a randomized double-blind stratum vs CNI/MTX, current accrual =133 of 140 patients) and (2) 7/8 MMURD (a single-arm stratum with 43 patients, enrollment completed in Nov, 2016). The 7/8 stratum was non-randomized due to ethical concerns related to the high risk of death from severe AGVHD in 7/8 URD HCT in the absence of adjunctive immunosuppression. The 7/8 stratum thus underwent a pre-specified comparison to CIBMTR matched controls. Here we report the results from the 7/8 stratum with a follow-up of 227-1544 days (median 559).The primary outcome was the incidence of severe (Gr III-IV) AGVHD prior to day +100. Key secondary outcomes were Gr II-IV AGVHD, chronic GVHD (CGVHD), graft failure, engraftment, transplant-related mortality (TRM), relapse, disease-free survival (DFS) and overall survival (OS). Key inclusion criteria were age >6, myeloablative conditioning and a high-risk heme malignancy. Key exclusion criteria were the use of ATG, alemtuzumab, or other T cell depletion, or a cord blood graft. Stopping rules were in place for TRM and PTLD, neither of which were met. We compared ABA2 to two CIBMTR matched control cohorts: (1) 7/8 URD HCT using CNI + MTX (n =127) or (2) CNI/MTX plus anti-thymocyte globulin (‘+ATG’, n = 128). Matching was based on age, performance score and disease stage, with similar baseline characteristics (Table 1).42 of 43 ABA2 patients received all 4 abatacept doses, and all 43 successfully engrafted donor cells, with no delay in median neutrophil (17 days) or platelet (18 days) engraftment. ABA2 was associated with a marked reduction in the cumulative incidence of grade III-IV AGVHD at day 100, with only 2.3% Gr III-IV AGVHD in ABA2 vs 30% in CNI+MTX and 22% in +ATG (p =0.0070 and 0.025, Fig. 1A, 2A). Grade II-IV AGVHD was similar in ABA2 vs controls (44.9% in ABA2 vs 53% in CNI+MTX and 45% in +ATG, p= 0.08 and 0.36). CGVHD was also similar: 40% at 12 months in ABA2 vs 41% in CNI+MTX and 37% in +ATG (p =ns). Importantly, the reduction in severe AGVHD in ABA2 was achieved without significant impact on patient safety, resulting in striking improvement in 12 month TRM (12.5% vs 34% in CNI+MTX and 27% in +ATG (p = 0.002 and 0.04, Fig. 1B, 2B). Also noteworthy, there was no increase in relapse in ABA2, with 7.5% relapse at 12 months compared to 15% in CNI+MTX and 11% in +ATG (p=0.04 and 0.26). Detailed analyses of viral reactivation and other infectious outcomes are ongoing, but uncontrolled infections were not a major problem. This led to very promising rates of DFS and OS in ABA2: 81% 12 month DFS, which was better than both CNI+MTX (50%) and +ATG (63%), p=0.0003 and 0.016, Fig. 1C, 2C). The same was true for OS: 85.4% OS at 12 months in ABA2, vs CNI+MTX (57%) and +ATG (68%, p=0.0025 and 0.048 respectively, Fig. 1D, 2D). These survival advantages are stable thus-far through 2 years.Our results strongly suggest that the administration of 4 doses of abatacept for GVHD prophylaxis is safe and highly effective at preventing severe AGVHD, lessens the risk for TRM and improves survival in MMURD HCT for heme malignancies. Our results also suggest that the administration of 4 doses of abatacept prior to day +30 may not be sufficient to impact CGVHD, thus trials to assess the effect of longer courses of abatacept are warranted. These results are the first to demonstrate significant efficacy of in vivo T cell costimulation blockade in enhancing outcomes after MMURD HCT, which could significantly expand the donor pool and improve outcomes for patients requiring these high-risk transplants. [Display omitted] DisclosuresNorkin:Celgene: Honoraria, Research Funding. Pulsipher:Jazz Pharmaceuticals: Other: advisory board, education; CSL Behring: Other: advisory board Feb 2017; Chimerix: Other: Advisory board Dec 2015; Novartis Pharmaceuticals Corporation: Consultancy, Other: Phase II steering committee; Adaptive: Other: Advisory board 6/17. Kean:Juno: Research Funding; Regeneron: Research Funding; Kymab Ltd: Research Funding; Bristol Myers Squibb: Consultancy.

433 - T Cell Co-Stimulatory Blockade By CTLA4-Ig Does Not Appear to Impact the Clinical Efficacy of Viral Specific T Cell Therapy in Pediatric Patients after HSCT

433 - T Cell Co-Stimulatory Blockade By CTLA4-Ig Does Not Appear to Impact the Clinical Efficacy of Viral Specific T Cell Therapy in Pediatric Patients after HSCT

Abatacept Is Effective for Gvhd Prophylaxis after Unrelated Donor Stem Cell Transplantation (URD SCT) for Severe Sickle Cell Disease (SCD)

Background In 2016, results from the first URD SCT for SCD (the SCURT Trial) revealed a 2-year overall survival (OS) and event-free survival (EFS) of 79% (95% CI 59-90) and 69% (95% CI, 48-82) respectively following reduced intensity conditioning (RIC).1 Though the RIC approach provided successful engraftment in the majority, the transplant approach was not considered safe for widespread adoption due to high rates of graft-versus-host disease (GVHD) especially in children &amp;gt;13 years, a predominant cause of mortality. Strategies to minimize GVHD were essential if URD SCT was to be considered with curative intent in SCD. Aim/Method Multicenter trial (NCT03128996) with the primary objective of determining EFS in non-malignant disorders at one-year was amended as follows. The phase I SCD cohort included conditioning with hydroxyurea, proximal alemtuzumab, fludarabine, and melphalan in patients with 8/8 HLA-matched URD (-A, -B, - C and -DRB1).1 Thiotepa (8 mg/kg) was added in 7/8 HLA-mismatched SCT. GVHD prophylaxis included a calcineurin inhibitor and methotrexate as previously described. Abatacept (10 mg/kg) was administered on days -1, +5, +14, +28, +60, +100, +180, +270 and +365 based on efficacy described against acute GVHD with early dosing after SCT for malignant disorders.2,3 The latter 3 doses were omitted in cord transplant recipients. Result Thirteen children (7-21 years) underwent SCT (8/8 URD marrow- 7; 7/8 URD marrow or cord-6) primarily for stroke (N=6), ≥3 severe vaso-occlusive pain crises (N=4) or ≥2 acute chest syndrome episodes per year (N=3). The conditioning regimen was well tolerated. One patient had primary graft rejection after CMV infection (7%) and had autologous recovery. All other patients engrafted; neutrophils at median of 18 days (10-24), platelets at median of 28 days (16-39) and are surviving free of SCD with median follow-up of 12 months (range 4-59). Myeloid lineage donor chimerism was &amp;gt;95% and lymphoid was 39%- 100% at day+100. Two-year OS and EFS was 100% and 92.3% (95% CI, 6.57-35.7), respectively. The day+100 incidence of grade II-IV and III-IV acute GVHD incidence was 23% and 15% respectively. One-year incidence of chronic GVHD was 38%. However, only one patient (7%) developed extensive cGVHD. One patient (7%) developed posterior reversible encephalopathy syndrome and recovered. Viral replication in blood was detected in 7 of 13 patients (7 CMV, 1 EBV reactivation). No patient developed EBV PTLD or required EBV-related intervention. Conclusion In comparison to previous experience1 with RIC and URD SCT, our early observations are (1) a lower incidence of PRES (7 vs 34%) (2) low incidence of severe acute GVHD (15% vs 17% grade III -IV) despite mismatched donors, (3) low incidence of extensive chronic GVHD (7% vs 38%) and (4) no mortality despite patient age (10/13 were &amp;gt;13 years old). We attribute this gain to avoiding steroid use, and the benefit of including abatacept into the treatment regimen. The engraftment, safety, and immune reconstitution profile continue to be monitored in this ongoing trial now accruing in a Phase II cohort. As we and others work toward expanding donor options for SCD transplants, we submit that all alternate donor transplants for severe SCD are experimental and should be performed on clinical trials that track success and pitfalls. Reference: 1. Shenoy S et al. A trial of unrelated donor marrow transplantation for children with severe sickle cell disease. Blood. 2016 Nov 24; 128(21): 2561-2567. 2. Koura et al. In vivo T cell costimulation blockade with abataceptfor acute graft-versus-host disease prevention: a first-in-disease trial. Biol Blood Marrow Transplant. 2013 Nov; 19(11): 1638-49. 3. Watkins BK et al. T cell co-stimulation blockade with CTLA-4 Ig (Abatacept) for acute GVHD prevention in HLA-matched and mismatched unrelated donor transplantation: Results of a Phase 2 trial. Abstract 65. ASTCT Meetings, Houston 2019. Figure Disclosures Shah: Jazz pharmaceuticals: Speakers Bureau. OffLabel Disclosure: Abatacept, FDA approved for rheumatoid arthritis is a fusion protein that inhibits T-cell activation by binding to CD80/CD86 on antigen-presenting cells (APCs).It is used for acute graft-versus-host disease (aGVHD) prevention during unrelated-donor hematopoietic cell transplantation in this study

Elimination of Acute GvHD with Three Doses of Abatacept Prophylaxis Combined with Post-Transplant Cyclophosphamide after Myeloablative Treosulfan-Based Conditioning in the HLA Identical Sibling and Unrelated (10-12/12) Peripheral Blood Stem Cell Donor Setting: Improved Safety and Efficacy Compared to Alemtuzumab Prophylaxis

Background. Acute graft versus host disease (GvHD) remains a major cause of treatment failure post allogeneic stem cell transplantation (HSCT). CD28-CD80/CD86 axis T cell co-stimulation blockade with CTLA4-Ig using abatacept (AB) is an emerging acute GvHD prophylaxis strategy1. After myeloablative conditioning (MAC), together with methotrexate and calcineurin inhibition, four doses of AB commencing day (d)-1 is being investigated in the unrelated HLA 7/8 and 8/8 mismatched/matched donor settings, mostly in children2. It is unknown if AB can be de-escalated in adults to three doses for HLA matched sibling (SIB) or unrelated 10-12/12 donors (MUD), or combined with post-transplant cyclophosphamide (PT-CY) GvHD prophylaxis3, or combined with treosulfan (TREO)-based MAC4, which are other emerging transplant strategies. We investigated the safety and efficacy of this combination, and compared outcomes to a standard anti-CD52 directed IgG1 alemtuzumab (CH) prophylaxis regimen5 in a reduced intensity conditioning (RIC). Methods. We report a single centre consecutive cohort study using peripheral blood stem cells from SIB or HLA 10-12/12 MUDs, for HSCT in adults with blood cancer indications (intuitional registration: 1920-31). One group received AB GvHD prophylaxis while the other group received CH. During 2018-2019, the AB cohort received MAC with IV fludarabine 150 mg/m2, IV TREO 42 mg/m2, and 2 Gy total body irradiation (TBI). GvHD prophylaxis comprised three doses of IV AB 10 mg/kg on d+5, +14, and +28. This was combined with IV PT-CY 50 mg/kg on d+3 and +4, IV tacrolimus 0.03 mg/kg/d infusion from d+5, and IV mycophenolate mofetil 15 mg/kg tds from d+53. The MAC AB cohort was compared to a RIC CH cohort, chosen to be biased against AB. During 2017-2018 the CH cohort received RIC with IV fludarabine 150 mg/m2and IV melphalan 140 mg/m2. GvHD prophylaxis comprised IV CH 10 mg on d-7 to d-3, and IV ciclosporin 1.5 mg/kg bd from d-1. The primary outcome measure was the incidence of acute GvHD6 at d100 and 180 post HSCT. Secondary outcomes measures were the incidence of graft failure, mixed donor chimerism, donor lymphocyte infusion (DLI), CMV reactivation, relapse, overall survival, at d100 and 180. The AB and CH cohorts were indirectly compared. Results. A total of 39 patients were included in this study, with 15 consecutive patients in the AB group (Table). The AB group had a median Karnofsky score of 70% and HCT-CI of 6; significant comorbidity greater than other reports1,2. The major cancer indications were acute leukaemia and myelodysplastic syndrome (MDS). The AB and CH groups were largely balanced. There were no AB related infusion reactions. As expected for MAC, the AB group had a numerically but not clinically significantly slower time to engraftment relative to the RIC CH group. There was no AB group graft failure. Remarkably, the AB group did not experience acute GvHD compared to the CH group by d100 (P=0.03) and d180 (P&lt;0.01). In contrast, by d100, 29% in the CH group experienced acute GvHD after a median of 59 days post HSCT. No AB group patients experienced mixed donor chimerism (P&lt;0.01), nor required a DLI (P&lt;0.01) compared to the CH group, where all had &lt;99% T cell or whole blood values at d100. Consequently, 45% of the CH cohort without acute GvHD were treated with DLI, with all patients experiencing acute GvHD at a median of 39 days post DLI (Table). Other secondary outcomes were similar. The AB group experienced a CMV reactivation rate of 67% in IgG seropositive patients. Unfortunately, 93% of CMV IgG positive patients in the CH group experienced CMV reactivation. No relapses were observed by d180 in the AB group, whereas in the CH group, 8% of patients experienced relapse. Mortality at d180 was 20% in the MAC AB group, and 21% in the RIC CH group. Conclusions. Acute GvHD prophylaxis with only three doses of AB and PT-CY post TREO-based MAC appears to be safe and efficacious in the SIB and MUD settings, in a highly co-morbid adult blood cancer population. This AB approach seems favourable compared to CH despite RIC, where acute GvHD without DLI or post DLI remains significant. A prospective multicentre clinical trial with AB in this setting seems warranted to confirm these remarkable findings of patient benefit. References. 1. Biol Blood Marrow Transplant (BBMT) 2013;19:1638-49. 2. NCT01743131. 3. Lancet Haematol 2019;6:e132-43. 4. Cancer 2017;123:2671‐79. 5. BBMT 2017;23:805-12. 6. BBMT 2016;22:4-10. Table Disclosures No relevant conflicts of interest to declare. OffLabel Disclosure: Abatacept, alemtuzumab, cyclophosphamide all the for the indication of graft versus host disease (GvHD) prophylaxis.

Using the Immunophenotype to Predict Response to Biologic Drugs in Rheumatoid Arthritis.

Tumour necrosis factor (TNF)-α is a key mediator of inflammation in rheumatoid arthritis, and its discovery led to the development of highly successful anti-TNF therapy. Subsequently, other biologic drugs targeting immune pathways, namely interleukin-6 blockade, B cell depletion, and T cell co-stimulation blockade, have been developed. Not all patients respond to a biologic drug, leading to a knowledge gap between biologic therapies available and the confident prediction of response. So far, genetic studies have failed to uncover clinically informative biomarkers to predict response. Given that the targets of biologics are immune pathways, immunological study has become all the more pertinent. Furthermore, advances in single-cell technology have enabled the characterization of many leucocyte subsets. Studying the blood immunophenotype may therefore, define biomarker profiles relevant to each individual patient’s disease and treatment outcome. This review summarises our current understanding of how immune biomarkers might be able to predict treatment response to biologic drugs.

Early Expansion of CD56dim NKG2Alow with Late Surge and Persistence of CD56dimNKG2AnegNKG2Cbright NK Cells Attenuate Cytomegalovirus (CMV) Replication and Recurrence As Well As Leukemia Relapse Following Haploidentical HSCT with T Cell Co-Stimulation Blockade and Ptcy

CMV related morbidity and mortality remains a major limiting factor in Haploidentical HSCT. We have developed a novel approach to Haploidentical PBSCT combining T cell Costimulation Blockade (T-COSB) with PTCy and Cyclosporine or Sirolimus (BBMT 2018). We studied the pattern of CMV reactivation (CMV-R) and its progression in 60 patients undergoing Haploidentical HSCT in this protocol in relation to the kinetics of Immune Reconstitution (IR) and pattern of leukemia relapse. PCR based CMV monitoring was carried out until 180 days with preemptive anti-CMV therapy. All patients and donors were CMV seropositive. CMV-R was 54.2% with median onset at 32 days (14-75) in the study group [compared to 52.5% in 42 who had received PTCy alone (p=0.8)]. The median peak viral load was 5.7 × 103/ml (1.8-25.8). The median duration of anti-CMV therapy was 16 days (7-60 days). There was no recurrence noted before100 days and only 2/32 (6.2%) beyond 100 days with no CMV disease. CMV-R was higher in those transplanted for malignant diseases compared to non-malignant diseases (62.5% vs 8.2%, p=0.01). Analysis of IR in relation to CMV-R showed no difference in CD3 or CD4+T cell reconstitution. However, CD56dimCD16+ NK cells at D+60 were significantly higher in patients without CMV-R (median 95 vs 45 cells/µl, p=0.02) and the same population of cells were associated with lower peak of viral load (p=0.04). In those with a lower viral peak and lower duration of viral replication, CD56dimCD16+ NK cells had a higher KIR repertoire with lower NKG2A expression. In those with CMV-R, a subsequent surge in absolute NK cells was observed (median 188 vs 112 cells/µl, p=0.01). This was primarily contributed by massive expansion of CD56dimNKG2AnegNKG2Cbright NK cells (median 7.8% [5-14.6%] at day +30 to 35% [28-65%] at day +90, p=0.01, Fig 1). This phenomenon was not witnessed in patients treated with PTCy alone. Peak viral load inversely correlated with NKG2C+ NK cells and CD45RO+CD8+ T cells at day +90 (p=0.03). The incidence of aGVHD (10.2%), cGVHD (18%), NRM (9.5%), and overall survival (75.8%) were not influenced by CMV-R. Incidence of relapse was 23.5 % at 28-144 days (median 85 days). However, none of the patients who relapsed before 100 days had proliferation of NKG2C+ NK cells and only 1/38 patients with proliferation and persistence of this subpopulation beyond 100 days experienced leukemia relapse at a median follow-up of 18 months (p=0.01). The kinetics of NK cell reconstitution in relation to the pattern of viral replication suggests that an early surge of CD56dimNKG2Alow NK cells with cytotoxic potential is responsible for the initial containment of viral replication followed by late surge and persistence of memory type NKG2C+NK cells preventing late recurrence as well as leukemia relapse. This unique synaptic response was possibly responsible for improved outcome with this novel approach of T-COSB based haploidentical HSCT.

T Cell Costimulation Blockade with CTLA4-Ig (Abatacept) for Acute Gvhd Prevention in HLA Matched and Mismatched Unrelated Donor Transplantation: Results of the First Phase 2 Trial

We performed a Ph2 trial in adults and children to test abatacept for AGVHD prevention (‘ABA2', Clinicaltrials # NCT01743131), based on our promising preclinical and pilot patient data. ABA2 had 2 cohorts: A) HLA-mismatched (‘7/8', n = 43), a single-arm study with pre-specified CIBMTR matched analysis (vs CNI+MTX or CNI+MTX+ATG). B) HLA-matched (‘8/8', n = 142), randomized double-blind, comparing CNI+MTX+placebo vs CNI+MTX+ABA (‘ABA'). For each ABA arm, patients received 4 doses of 10mg/kg on d -1,5,14,28. ABA2 was designed as a screening Ph2 trial, with relaxed Type 1 error (0.2) and standard Type 2 error (0.2). Power analysis assumed ABA would decrease Gr 3-4 AGVHD from 30%–>10% in 7/8s and from 20%–>10% in 8/8s. Here we report top-line results for the 7/8s (median f/u = 708d, 264-1491) and 8/8s (median f/u = 369d, 180-1175). Reduced Grade 3-4 AGVHD: ABA was associated with decreased d180 Gr 3-4 AGVHD. In 7/8s, Gr 3-4 AGVHD = 2.5% in ABA (1 event/43 patients) vs 31% (CNI+MTX) and 22% (+ATG), 1 sided p = 0.001, 0.005,). In 8/8s, Gr 3-4 AGVHD = 6.85 % (5 events/73 patients) in ABA vs 14.6% (10 events) in placebo, 1 sided p = 0.068). Reduced Grade 2-4 AGVHD in 8/8s: ABA was associated with decreased d180 Gr 2-4 AGVHD. In 7/8s, Gr 2-4 AGVHD = 42% (ABA) vs 54% (CNI+MTX) and 45% (+ATG, 1 sided p = 0.098, 0.25). In 8/8s, Gr 2-4 AGVHD = 44.5% in ABA vs 62.3% in placebo (1 sided p = 0.004). Chronic GVHD: For 7/8s, 1 yr CGVHD = 38.8% (ABA) vs 43.5% (CNI+MTX) and 35.5% (+ATG, p = 0.4, 0.99). For 8/8s, follow up is still too short to adequately evaluate, and adjudication is ongoing. No Increase In Relapse: In 7/8s, relapse = 9.37% at 1 y vs 12.9% in CNI+MTX and 13.6% in +ATG (p = 0.115 and 0.085). In 8/8s, relapse = 13.8% at 1y (ABA) vs 20.5% (placebo, p = 0.7). Remarkably, in 7/8s, where median follow up=708d, there have been no further relapses reported in ABA2, with 9.37% relapse at 2 yr vs 20.63% (CNI+MTX) and 23.4% (ATG), despite matched disease risk. Statistically significant survival advantage in 7/8s: TRM: For 7/8s, 1 yr TRM = 10.5% (ABA) vs 32.7% (CNI+MTX) and 26% (+ATG, p = 0.024, 0.365). For 8/8s, TRM = 7.1% vs 14.6% at 1 yr (p = 0.5). Relapse-Free Survival (RFS): For 7/8s, RFS = 73.7% (ABA) vs 38.7% in CNI+MTX and 48.7% in +ATG (p = 0.001 and 0.027). For 8/8s, RFS = 79.1% for ABA vs 64.9% (placebo, p = 0.38). OS: For 7/8s, OS = 71% (ABA) vs 47.5% (CNI+MTX) and 58% (+ATG, p = 0.01 and 0.145). For 8/8s, OS = 83.2% (ABA) vs 76.6 (placebo, p = 0.32). Our results suggest that short-course (4 doses) ABA can safely prevent AGVHD without compromising relapse. While this was a modestly sized study (7/8s: n = 43, 8/8 n = 142), the comparative event size for 7/8s was high enough that the protective effect of ABA was highly statistically significant. For 8/8s, there was a statistically significant improvement for Gr 2-4 GVHD and a trend toward an advantage for ABA in all other parameters. These results are the first to demonstrate efficacy of in vivo T cell costimulation blockade in preventing AGVHD.

Higher CD45RA+ Regulatory T Cells in the Graft Improves Outcome in Younger Patients Undergoing T Cell–Replete Haploidentical Transplantation: Where Donor Age Matters

To understand the phenomenon of early alloreactivity (EA) in younger children undergoing post-transplantation cyclophosphamide (PTCy)-based haploidentical transplantation, we studied the graft composition and the immune reconstitution in 32 consecutive patients (aged 2 to 25 years) undergoing PTCy and T cell costimulation blockade based peripheral blood stem cell transplantation with emphasis on CD45RA+ subset of regulatory T cells (Tregs). All but 1 engrafted, and 14 patients experienced EA (acute graft-versus-host disease grades II to IV, n = 8; and post-transplantation hemophagocytic syndrome, n = 6) with a cumulative incidence of 43.7%; 42% developed mild chronic graft-versus-host disease. The overall survival was 70.2% with a nonrelapse mortality of 16.8% at a median of 19 months. Age < 10 years, donor age > 45 years, and poor recovery of Tregs correlated with EA. Not Tregs but higher CD45RA+ Tregs in the graft was associated with less EA (11.7% versus 32.5%, P = .0001). Higher donor age correlated with a lower CD45RA+ Tregs in the graft (P = .01). However, only higher CD45RA+ Treg percentage in the graft favorably impacted EA as well as nonrelapse mortality and overall survival. Our study demonstrates a critical role for CD45RA+ Tregs in determining EA and outcome after PTCy-based haploidentical peripheral blood stem cell transplantation, and the age-related physiologic decline in this population might be responsible for adverse impact of donor age.

Ischemia augments alloimmune injury through IL-6-driven CD4+ alloreactivity

Ischemia reperfusion injuries (IRI) are unavoidable in solid organ transplantation. IRI augments alloimmunity but the mechanisms involved are poorly understood. Herein, we examined the effect of IRI on antigen specific alloimmunity. We demonstrate that ischemia promotes alloimmune activation, leading to more severe histological features of rejection, and increased CD4+ and CD8+ T cell graft infiltration, with a predominantly CD8+ IFNγ+ infiltrate. This process is dependent on the presence of alloreactive CD4+ T cells, where depletion prevented infiltration of ischemic grafts by CD8+ IFNγ+ T cells. IL-6 is a known driver of ischemia-induced rejection. Herein, depletion of donor antigen-presenting cells reduced ischemia-induced CD8+ IFNγ+ allograft infiltration, and improved allograft outcomes. Following prolonged ischemia, accelerated rejection was observed despite treatment with CTLA4Ig, indicating that T cell costimulatory blockade failed to overcome the immune activating effect of IRI. However, despite severe ischemic injury, treatment with anti-IL-6 and CTLA4Ig blocked IRI-induced alloimmune injury and markedly improved allograft survival. We describe a novel pathway where IRI activates innate immunity, leading to upregulation of antigen specific alloimmunity, resulting in chronic allograft injury. Based on these findings, we describe a clinically relevant treatment strategy to overcome the deleterious effect of IRI, and provide superior long-term allograft outcomes.

Treatment with Biologicals in Rheumatoid Arthritis: An Overview.

Management and therapy of rheumatoid arthritis (RA) has been revolutionized by the development and approval of the first biological disease-modifying antirheumatic drugs (bDMARDs) targeting tumor necrosis factor (TNF) α at the end of the last century. Today, numerous efficacious agents with different modes of action are available and achievement of clinical remission or, at least, low disease activity is the target of therapy. Early therapeutic interventions aiming at a defined goal of therapy (treat to target) are supposed to halt inflammation, improving symptoms and signs, and preserving structural integrity of the joints in RA. Up to now, bDMARDs approved for therapy in RA include agents with five different modes of action: TNF inhibition, T cell co-stimulation blockade, IL-6 receptor inhibition, B cell depletion, and interleukin 1 inhibition. Furthermore, targeted synthetic DMARDs (tsDMARDs) inhibiting Janus kinase (JAK) and biosimilars also are approved for RA. The present review focuses on bDMARDs and tsDMARDS regarding similarities and possible drug-specific advantages in the treatment of RA. Furthermore, compounds not yet approved in RA and biosimilars are discussed. Following the American College of Rheumatology (ACR) and European League Against Rheumatism (EULAR) recommendations, specific treatment of the disease will be discussed with respect to safety and efficacy. In particular, we discuss the question of favoring specific bDMARDs or tsDMARDs in the two settings of insufficient response to methotrexate and to the first bDMARD, respectively.

T cell costimulation blockade promotes transplantation tolerance in combination with sirolimus and post-transplantation cyclophosphamide for haploidentical transplantation in children with severe aplastic anemia

We conducted a pilot study employing extended T cell costimulation blockade (COSBL) with Abatacept along with sirolimus and post-transplantation cyclophosphamide (PTCy) in 10 patients (median age 12) with severe aplastic anemia (SAA). Nine patients engrafted in the COSBL group, compared to all 10 patients (median 14 vs 13days) treated on PTCy protocols without abatacept (CONTROL group). The incidence of acute graft-versus-host disease (GVHD) was 10.5% in the COSBL group compared to 50% in the CONTROL group (p=0.04). Chronic GVHD (12.5% vs 56%, p=0.02) and CMV reactivation (30% vs 80%, p=0.03) were also reduced in the COSBL group. T and NK cell subset analysis revealed higher CD56brightCD16− NK cells in the CONTROL group (p=0.004), but similar CD56dimCD16+ NK cells in both groups at day+30. Tregs (CD4+CD25+CD127dim/− FoxP3+) were markedly higher in the COSBL group at day+30 (8.4% vs 1.1%) and the trend was maintained through day+90 (p<0.01). The GVHD and Disease-free survival at one year in the COSBL group was 80% vs. 30% in the CONTROL group (p=0.05). Our preliminary findings suggest that COSBL in combination with PTCy and sirolimus might augment transplantation tolerance in children with SAA, probably due to synergistic effect on early recovery of Tregs.

T cell costimulation blockade blunts pressure overload-induced heart failure

Heart failure (HF) is a leading cause of mortality. Inflammation is implicated in HF, yet clinical trials targeting pro-inflammatory cytokines in HF were unsuccessful, possibly due to redundant functions of individual cytokines. Searching for better cardiac inflammation targets, here we link T cells with HF development in a mouse model of pathological cardiac hypertrophy and in human HF patients. T cell costimulation blockade, through FDA-approved rheumatoid arthritis drug abatacept, leads to highly significant delay in progression and decreased severity of cardiac dysfunction in the mouse HF model. The therapeutic effect occurs via inhibition of activation and cardiac infiltration of T cells and macrophages, leading to reduced cardiomyocyte death. Abatacept treatment also induces production of anti-inflammatory cytokine interleukin-10 (IL-10). IL-10-deficient mice are refractive to treatment, while protection could be rescued by transfer of IL-10-sufficient B cells. These results suggest that T cell costimulation blockade might be therapeutically exploited to treat HF.