Daratumumab in Sensitized Kidney Transplantation: Potentials and Limitations of Experimental and Clinical Use

Abstract

Background: Donor-specific antibodies are associated with increased risk of antibody-mediated rejection and decreased allograft survival. Therefore, reducing the risk of these antibodies remains a clinical need in transplantation. Plasma cells are a logical target of therapy given their critical role in antibody production.

Methods: To target plasma cells, we treated sensitized rhesus macaques with daratumumab (anti-CD38 mAb). Before transplant, we sensitized eight macaques with two sequential skin grafts from MHC-mismatched donors; four of them were also desensitized with daratumumab and plerixafor (anti-CXCR4). We also treated two patients with daratumumab in the context of transplant.

Results: The animals treated with daratumumab had significantly reduced donor-specific antibody levels compared with untreated controls (57.9% versus 13% reduction; P<0.05) and prolonged renal graft survival (28.0 days versus 5.2 days; P<0.01). However, the reduction in donor-specific antibodies was not maintained because all recipients demonstrated rapid rebound of antibodies, with profound T cell-mediated rejection. In the two clinical patients, a combined heart and kidney transplant recipient with refractory antibody-mediated rejection and a highly sensitized heart transplant candidate, we also observed a significant decrease in class 1 and 2 donor-specific antibodies that led to clinical improvement of antibody-mediated rejection and to heart graft access.

Conclusions: Targeting CD38 with daratumumab significantly reduced anti-HLA antibodies and anti-HLA donor-specific antibodies in a nonhuman primate model and in two transplant clinical cases before and after transplant. This supports investigation of daratumumab as a potential therapeutic strategy; however, further research is needed regarding its use for both antibody-mediated rejection and desensitization.

Keywords: antibody-mediated rejection; daratumumab; desensitization; nonhuman primate; plasma cell.

Graphical abstract

Figure 1.

Desensitization with daratumumab and plerixafor reduces donor-specific alloantibody significantly in sensitized NHPs. (A) Schematic representation of sensitization and desensitization. Maximally MHC-mismatched NHP pairs received two serial skin transplants for sensitization and desensitization treatment or no treatment (control group) before kidney transplantation. (B) The absolute number of peripheral white blood cells and immune cell population. (C) Effect of DPT on peripheral B cells. B cell subpopulations, including CD20+ B cells, IgG⁺ B cells, and IgG⁺CD27⁺ B cells, were not changed. (D) The frequency of naive, central memory, effector memory CD4, and CD8 T cells were not changed with DPT. (E) Desensitization with daratumumab and plerixafor reduces DSA significantly compared with control. DSA levels were measured by T cell flow crossmatch and shown as MFI shift. *P<0.05. (F) Representative normalized MFI of single antigen bead testing before and after DPT. NHP serum samples were evaluated with HLA single antigen bead assay. BASO, basophil; EO, eosinophil; LN/BM, lymph node/bone marrow; LYMPH, lymphocyte; MONO, monocyte; NEUT, neutrophil; Tcm, central memory T cell; Tem, effector memory T cell; Tn, naive T cell; Tx, transplant; WBC, white blood cell.

Figure 2.

Desensitization with daratumumab and plerixafor reduces PC population, but not Tfh cells, in the lymph nodes. (A) Plasmablast population in the lymph nodes after desensitization. Representative flow plot shows the percentage of CD20⁻CD27⁺CD38⁺ cells within the CD3⁻IgD⁻ population of lymph nodes pre- (blue) and post- (orange) desensitization time points with DPT. (B) Tfh populations in the lymph nodes after desensitization. Representative flow cytometry plots show the percentage of PD1⁺ICOS⁺ Tfh cells within the CD4⁺ T cell population in lymph node pre- (blue) and post- (orange) desensitization with daratumumab and plerixafor. (C) Representative immunohistochemistry shows the Ki67-stained areas within the CD20+ B cell follicles in lymph nodes pre- and postdesensitization with daratumumab and plerixafor. Clonal B cell expansion (Ki67+CD20+) within B cell follicle was not significantly changed after desensitization. Images were adapted from whole slide scan; original magnification ×40 (inset, ×100). GC, Germinal Center.

Figure 3.

Desensitization with daratumumab and plerixafor significantly prolongs but limits renal allograft survival in sensitized NHPs. (A) Dosing regimen of T cell depletional induction and maintenance immunosuppression for kidney transplantation after desensitization or without desensitization. (B) Percentage graft survival of sensitized NHPs with or without desensitization. Animals treated with DPT showed significantly prolonged graft survival compared with control group (P<0.05). (C) Representative hematoxylin and eosin (top panels) and C4d (bottom panels) staining of kidney allografts from control (left panels) and DPT (right panels) animals at the time of euthanasia. (D) Clustered Banff score related to AMR and TCMR. Animals treated with daratumumab and plerixafor showed elevated AMR score (g+ptc+C4d) and acute rejection (v+t+i) at euthanasia. (E) Post-transplant DSA kinetics. Animals with desensitization showed rapidly increased serum DSA (normalized to pre–renal transplant value=1). Post–kidney transplant peak DSA level showed strong trend of elevation compared with pretransplant time point. Original magnification ×200. ACR, acute cell-mediated rejection; g, glomerulitis; H&E, hematoxylin and eosin; i, interstitial inflammation; MMF, mycophenolate mofetil; ptc, peritubular capilaritis; t, tubulitis; TMA, thrombotic microangiopathy; Tx, transplant; v, intimal arteritis.

Figure 4.

A possible immune deviation after daratumumab and plerixafor treatment. (A) Ratio of CD8 to CD4 was not changed after desensitization with daratumumab and plerixafor in blood and lymph nodes. (B) Ratio of CD8 cells to Treg cells show a strong increasing trend (P=0.06) in the lymph nodes but not in the blood. (C) Transitional B cell population (CD20⁺CD24⁺CD38⁺) showed a strong trend of reduction (P=0.08). (D) Increased frequencies of activated T (CD69⁺) cells after kidney transplantation. The results are representative of four monkeys tested individually. LN, lymph node.

Figure 5.

Histological improvement of heart and kidney acute rejection after daratumumab treatment. (A–F) Kidney allograft biopsy at the time of diagnosis showed (A) interstitial edema and diffuse infiltrate (periodic acid–Schiff stain), made of (B) >10% of PCs (immunohistochemical staining with CD138), (C) with severe tubulitis (methenamine silver-periodic Jones stain Marinozzi), (D) capillaritis (periodic acid–Schiff ), and (E) interstitial hemorrhage (Masson trichrome). (F) Immunohistochemical stain with C4d is diffusely positive on peri-tubular capillaries. (G–H) Kidney allograft biopsy after daratumumab showed significant reduction of the interstitial infiltrate with (G) only mild persistent tubulitis (periodic acid–Schiff ); (H) only scattered PCs are stained with CD138 antibody compared with the first kidney biopsy. (I–K) Heart allograft biopsy at the time of cardiogenic shock showed (I) diffuse edema (hematoxylin eosin saffron [HES] stain), (J) interstitial infiltrate with myocyte damage (HES stain), and (K) diffuse C4d positivity . (L) Heart allograft biopsy after daratumumab showed no significant anomaly (HES stain). Original magnification, ×200 in A; ×200 in B; ×400 in C; ×400 in D; ×400 in E; ×200 in F; ×100 in G; ×200 in H; ×200 in I; ×400 in J; ×100 in K; ×200 in L.

Figure 6.

Significant improvement of AMR and significant decrease of DSA after daratumumab treatment. (A) Heart and kidney function evolution after daratumumab as acute rejection treatment. After the first eight injections of daratumumab, heart and kidney allograft functions improved significantly. Inotropic positive drugs and hemodialysis could be stopped. Twenty weeks after the eighth daratumumab infusion, serum creatinine level increased significantly, and heart allograft function remained stable. Daratumumab was reinitiated and serum creatinine level decreased. (B) DSA evolution after daratumumab as acute rejection treatment. After the first eight injections of daratumumab, DSAs class 1 and class 2 MFI decreased significantly besides DQ7 anti-HLA antibody (class 2). Two DSAs class 2 (DR12 and DR52) remained detectable with MFI>1000. At the time of the AKI episode, three class 2 DSAs were detected with MFI>1000 (DQ7, DR12, and DR52). Of those, two of them (DR12 and DR52) decreased significantly after daratumumab reinfusion. (C) Anti-HLA antibodies evolution after daratumumab as desensitization treatment. After plasmapheresis, anti-HLA antibodies MFI and cPRA increased significantly, both class 1 and class 2. After eight weekly infusions of daratumumab, anti-HLA MFI and cPRA decreased significantly. Maintenance infusion, bimonthly, permitted to decrease MFI and number of significant anti-HLA antibodies.