BACKGROUND: Chronic active antibody-mediated rejection (caAMR) in kidney transplants is associated with irreversible tissue damage and a leading cause of graft loss in the long-term. However, the treatment for caAMR remains a challenge to date. Recently, tocilizumab, a recombinant humanized monoclonal antibody directed against the human interleukin-6 (IL-6) receptor, has shown promise in the treatment of caAMR. However, it has not been systematically investigated so far underscoring the need for randomized controlled studies in this area.
METHODS: The INTERCEPT study is an investigator-driven randomized controlled open-label multi-center trial in kidney transplant recipients to assess the efficacy of tocilizumab in the treatment of biopsy-proven caAMR. A total of 50 recipients with biopsy-proven caAMR at least 12 months after transplantation will be randomized to receive either tocilizumab (n = 25) added to our standard of care (SOC) maintenance treatment or SOC alone (n = 25) for a period of 24 months. Patients will be followed for an additional 12 months after cessation of study medication. After the inclusion biopsies at baseline, protocol kidney graft biopsies will be performed at 12 and 24 months. The sample size calculation assumed a difference of 5 ml/year in slope of estimated glomerular filtration rate (eGFR) between the two groups for 80% power at an alpha of 0.05. The primary endpoint is the slope of eGFR at 24 months after start of treatment. The secondary endpoints include assessment of the following at 12, 24, and 36 months: composite risk score iBox, safety, evolution and characteristics of donor-specific antibodies (DSA), graft histology, proteinuria, kidney function assessed by measured GFR (mGFR), patient- and death-censored graft survival, and patient-reported outcomes that include transplant-specific well-being, adherence to immunosuppressive medications and perceived threat of the risk of graft rejection.
CONCLUSIONS: No effective treatment exists for caAMR at present. Based on the hypothesis that inhibition of IL-6 receptor by tocilizumab will reduce antibody production and reduce antibody-mediated damage, our randomized trial has a potential to provide evidence for a novel treatment strategy for caAMR, therewith slowing the decline in graft function in the long-term.
BACKGROUND: ClinicalTrials.gov NCT04561986. Registered on September 24, 2020.

Natural killer (NK) cells mediate spontaneous cell-mediated cytotoxicity and antibody-dependent cell-mediated cytotoxicity. This dual functionality could enable their participation in chronic active antibody-mediated rejection (CA-ABMR). Earlier microarray profiling studies have not subcategorized antibody-mediated rejection into CA-ABMR and active-ABMR, and the gene expression pattern of CA-ABMR has not been compared with that of T cell-mediated rejection (TCMR). To fill these gaps, we RNA sequenced human kidney allograft biopsies categorized as CA-ABMR, active-ABMR, TCMR, or No Rejection (NR). Among the 15,910 genes identified in the biopsies, 60, 114, and 231 genes were uniquely overexpressed in CA-ABMR, TCMR, and active-ABMR, respectively; compared to NR, 50 genes were shared between CA-ABMR and active-ABMR, and 164 genes between CA-ABMR and TCMR. The overexpressed genes were annotated to NK cells and T cells in CA-ABMR and TCMR, and to neutrophils and monocytes in active-ABMR. The NK cell cytotoxicity and allograft rejection pathways were enriched in CA-ABMR. Genes encoding perforin, granzymes, and death receptor were overexpressed in CA-ABMR versus active-ABMR but not compared to TCMR. NK cell cytotoxicity pathway gene set variation analysis score was higher in CA-ABMR compared to active-ABMR but not in TCMR. Principal component analysis of the deconvolved immune cellular transcriptomes separated CA-ABMR and TCMR from active-ABMR and NR. Immunohistochemistry of kidney allograft biopsies validated a higher proportion of CD56+ NK cells in CA-ABMR than in active-ABMR. Thus, CA-ABMR was exemplified by the overexpression of the NK cell cytotoxicity pathway gene set and, surprisingly, molecularly more like TCMR than active-ABMR.

Kidney transplant recipients are immunocompromised hosts at risk for comorbidity and mortality due to infection. Currently, there are no established guidelines for the management of immunosuppressed transplant recipients with coronavirus disease 2019 (COVID-19). The impact of COVID-19 and its therapeutic management on chronic active antibody-mediated rejection (CAAMR) are still unclear. Here, we report a case of CAAMR exacerbation with endarteritis and intimal fibrosis after COVID-19. A 41-year-old female kidney transplant recipient with CAAMR was admitted to a local hospital with moderately severe COVID-19. Her doses of tacrolimus and mycophenolate mofetil were reduced, and she was administered methylprednisolone pulse and antiviral drugs. This resulted in a good clinical course and she was discharged in 15 days. During and after hospitalization, the immunosuppressants were gradually returned to the baseline levels. However, about 1.5 months after discharge, the serum creatinine level became elevated. An indication kidney biopsy showed CAAMR with intimal fibrosis and endarteritis in all interlobular arteries. An increase of immunosuppressant led to a decrease of the serum creatinine level. Factors contributing to CAAMR with intimal fibrosis and endarteritis may include (1) insufficient immunosuppression due to changes in the levels of immunosuppressive; (2) overlap with endothelial cell injury caused by COVID-19, and (3) an immune-activated state associated with COVID-19. COVID-19 is a life-threatening disease that can result in unexpected changes in immunological status. Possible allograft rejection should be carefully managed in such patients.

Late or chronic active antibody-mediated rejection (AMR) associated with de novo donor-specific antibodies (dnDSA) after renal transplantation is a great clinical challenge because it is often resistant to conventional therapies. Daratumumab, an anti-CD38 monoclonal antibody that can deplete plasma cells, may be effective for the treatment of late or chronic active AMR.
We designed a novel regimen that included early intensive therapy with daratumumab plus plasmapheresis (PP)/intravenous immunoglobulins (IVIG) and later maintenance therapy with daratumumab alone, and used this regimen to treat late or chronic active AMR in two kidney transplant recipients with extremely high levels of anti-DQ7 dnDSA.
Both patients had a limited clinical response to the early treatment with rituximab and PP/IVIG (with or without splenic irradiation); however, they had a remarkable decrease in anti-DQ7 DSA (MFI value from ~20,000 to ~5,000) after 2-3 months of intensive therapy with daratumumab plus PP/IVIG. Over 20 months of follow-up, patient 1 maintained a low DSA (as low as 1,572) and normal renal function on daratumumab maintenance therapy. Patient 2 retained a low DSA and improved renal function and pathological lesions within one year after treatment but then deteriorated because of acute T cell-mediated rejection.
Our daratumumab-based regimen has shown promising results in the treatment of refractory late active or chronic active AMR in renal transplant recipients with high-level dnDSA. This may provide a reference for better use of daratumumab in the treatment of late or chronic active AMR.

BACKGROUND: Chronic active antibody-mediated rejection (AMR) is a major cause of graft loss with no approved drugs for its treatment. Currently, off-label regimens are used, reflecting the high unmet need for effective therapies based on well-controlled trials. Clazakizumab is a high-affinity, humanized monoclonal antibody that binds interleukin-6 and decreases donor-specific antibody (DSA) production and inflammation. Phase 2 pilot studies of clazakizumab in kidney transplant recipients with chronic active AMR suggest modulation of DSA, stabilization of glomerular filtration rate (GFR), and a manageable safety profile. We report the design of the Phase 3 IMAGINE study (NCT03744910) to evaluate the safety and efficacy of clazakizumab for the treatment of chronic active AMR.
METHODS: IMAGINE is a multicenter, double-blind trial of approximately 350 kidney transplant recipients with chronic active AMR (Banff chronic glomerulopathy [cg] >0 with concurrent positive human leukocyte antigen DSA) randomized 1:1 to receive clazakizumab or placebo (12.5 mg subcutaneous once every 4 weeks). The event-driven trial design will follow patients until 221 occurrences of all-cause graft loss are observed, defined as return to dialysis, graft nephrectomy, re-transplantation, estimated GFR (eGFR) <15 mL/min/1.73m2, or death from any cause. A surrogate for graft loss (eGFR slope) will be assessed at 1 year based on prior modeling validation. Secondary endpoints will include measures of pharmacokinetics/pharmacodynamics. Recruitment is ongoing across North America, Europe, Asia, and Australia.
CONCLUSIONS: IMAGINE represents the first Phase 3 clinical trial investigating the safety and efficacy of clazakizumab in kidney transplant recipients with chronic active AMR, and the largest placebo-controlled trial in this patient population. This trial includes prognostic biomarker enrichment and uniquely utilizes the eGFR slope at 1 year as a surrogate endpoint for graft loss, which may accelerate the approval of a novel therapy for patients at risk of graft loss. The findings of this study will be fundamental in helping to address the unmet need for novel therapies for chronic active AMR.
BACKGROUND: ClinicalTrials.gov NCT03744910 . Registered on November 19, 2018.

Chronic kidney disease (CKD) is a major public-health problem that increases the risk of end-stage kidney disease (ESKD), cardiovascular diseases, and other complications. Kidney transplantation is a renal-replacement therapy that offers better survival compared to dialysis. Antibody-mediated rejection (ABMR) is a significant complication following kidney transplantation: it contributes to both short- and long-term injury. The standard-of-care (SOC) therapy combines plasmapheresis and Intravenous Immunoglobulins (IVIg) with or without steroids, with or without rituximab: however, despite this combined treatment, ABMR remains the main cause of graft loss. IL-6 is a key cytokine: it regulates inflammation, and the development, maturation, and activation of T cells, B cells, and plasma cells. Tocilizumab (TCZ) is the main humanized monoclonal aimed at IL-6R and appears to be a safe and possible strategy to manage ABMR in sensitized recipients. We conducted a literature review to assess the place of the anti-IL-6R monoclonal antibody TCZ within ABMR protocols.
We systematically reviewed the PubMed literature and reviewed six studies that included 117 patients and collected data on the utilization of TCZ to treat ABMR.
Most studies report a significant reduction in levels of Donor Specific Antibodies (DSAs) and reduced inflammation and microvascular lesions (as found in biopsies). Stabilization of the renal function was observed. Adverse events were light to moderate, and mortality was not linked with TCZ treatment. The main side effect noted was infection, but infections did not occur more frequently in patients receiving TCZ as compared to those receiving SOC therapy.
TCZ may be an alternative to SOC for ABMR kidney-transplant patients, either as a first-line treatment or after failure of SOC. Further randomized and controlled studies are needed to support these results.

Chronic active antibody-mediated rejection (CAAMR) is a frequent cause of late graft loss. However, effective treatment for CAAMR after kidney transplantation has not yet been established. Here, we present the case of a kidney transplant recipient who recovered from CAAMR after administration of rabbit anti-thymocyte globulin. A 61-year-old man underwent ABO-compatible living-donor kidney transplantation for end-stage kidney disease; the kidney was donated by his wife. Five years after the transplant, the patient\'s serum creatinine level and urine protein-to-creatinine ratio increased. He was subsequently diagnosed with CAAMR based on the kidney allograft biopsy and the presence of donor-specific human leukocyte antigen antibodies. Rabbit anti-thymocyte globulin treatment was administered following steroid pulse therapy. Subsequently, his serum creatinine levels and urine protein to creatinine ratio improved. There was also an improvement in the pathological findings seen on biopsy and the mean fluorescence intensity of donor-specific antibodies. In conclusion, this report describes the case of a kidney transplant recipient who developed CAAMR, treated using rabbit anti-thymocyte globulin. This strategy might be a viable treatment option for CAAMR after a kidney transplant.

Chronic active antibody-mediated rejection (CAAMR) is an intermediate process that occurs during the development of chronic antibody-mediated rejection (CAMR), which is a key problem associated with the long-term kidney grafts survival. This study investigated the role played by PC3-secreted microprotein (PSMP) in the progression of CAAMR and CAMR. We showed that CAAMR and CAMR patients\' allografts dysfunction with declined survival rate, which suggested that earlier diagnosis and treatment of CAAMR might be important to prevent irreversible chronic injury of CAMR progression. We found PSMP was an important factor in the development of chronic antibody-mediated rejection. The PSMP expression increased significantly in CAAMR biopsy samples but not in CAMR and control patients, which distinguished CAAMR patients from CAMR and non-rejection patients. Moreover, our results showed that infiltration of CD68+ macrophages in CAAMR increased, and the correlation between CD68+ macrophages and PSMP expression in CAAMR patients was significant. Additionally, our data also revealed that intimal arteritis (v-lesion) accompanied by increased macrophage infiltration might have contributed to more graft loss in CAAMR, and PSMP expression was significantly associated with the v-lesion score. These results indicated that PSMP played an important role in the recruitment of macrophages and promote intimal arteritis inducing allograft lost in CAAMR progression. In future study PSMP could be a potential histopathological diagnostic biomarker and treatment target for CAAMR in kidney transplantation.

Chronic active antibody-mediated rejection (CAABMR) is an important cause of late-stage renal allograft loss. Early inflammatory events such as acute rejection and infection after transplantation are considered to be the risk factors of de novo donor-specific antibody (dnDSA) production. In this study, we investigated the relationship between pre-disposing T-cell-mediated rejection and dnDSA-positive CAABMR.
We recruited 365 patients who underwent ABO-compatible renal transplantation at our hospital. Among them, 16 patients diagnosed as having dnDSA-positive CAABMR were designated as a CAABMR group, and 38 randomly selected patients were designated as a control group. All biopsies from 1 month after transplantation were included in the study. The presence or absence of borderline changes (BLCs), acute T-cell-mediated rejection (ATMR), microvascular inflammation (MVI), and C4d positive on peritubular capillaries (C4d-P) was examined.
In the CAABMR group, BLC/ATMR was found in 12 cases (75%), and the mean duration until appearance of BLC/ATMR was 282.7 ± 328.7 days. C4d-P was found in 11 cases (68.8%), and the mean duration until its appearance was 1,432 ± 1,307 days. MVI was found in all cases, and the mean duration until its appearance was 1,333 ± 1,126 days. The mean duration until diagnosis of CAABMR was 2,268 ± 1,191 days. In the control group, BLC/ATMR was found in 13 cases (34.2%), and the mean duration until the appearance of BLC/ATMR was 173.1 ± 170.4 days. C4d-P was found in 2 cases (5.3%), and the durations until its appearance were 748 and 1,881 days. No cases of MVI were found in the control group. The frequency of BLC/ATMR was significantly higher in the CAABMR group (p < 0.01).
Preceding BLC/ATMR is associated with the development of CAABMR with dnDSA.

Chronic allograft rejection is the most common cause of long-term allograft failure. One reason is that current diagnostics and therapeutics for chronic allograft rejection are very limited. We here show that enhanced NFκB signaling in kidney grafts contributes to chronic active antibody-mediated rejection (CAAMR), which is a major pathology of chronic kidney allograft rejections. Moreover, we found that urinary orosomucoid 1 (ORM1) is a candidate marker molecule and therapeutic target for CAAMR. Indeed, urinary ORM1 concentration was significantly higher in kidney transplant recipients pathologically diagnosed with CAAMR than in kidney transplant recipients with normal histology, calcineurin inhibitor toxicity, or interstitial fibrosis and tubular atrophy. Additionally, we found that kidney biopsy samples with CAAMR expressed more ORM1 and had higher NFκB and STAT3 activation in tubular cells than samples from non-CAAMR samples. Consistently, ORM1 production was induced after cytokine-mediated NFκB and STAT3 activation in primary kidney tubular cells. The loss- and gain-of-function of ORM1 suppressed and promoted NFκB activation, respectively. Finally, ORM1-enhanced NFκB-mediated inflammation development in vivo. These results suggest that an enhanced NFκB-dependent pathway following NFκB and STAT3 activation in the grafts is involved in the development of chronic allograft rejection after kidney transplantation and that ORM1 is a non-invasive candidate biomarker and possible therapeutic target for chronic kidney allograft rejection.