Human leukocyte antigen selected allogeneic mesenchymal stromal cell therapy in renal transplantation: The Neptune study, a phase I single-center study

Abstract

Mesenchymal stromal cells (MSC) hold promise as a novel immune-modulatory therapy in organ transplantation. First clinical studies have used autologous MSCs; however, the use of allogeneic "off-the-shelf" MSCs is more sustainable for broad clinical implementation, although with the risk of causing sensitization. We investigated safety and feasibility of allogeneic MSCs in renal transplantation, using a matching strategy that prevented repeated mismatches. Ten patients received two doses of 1.5 × 10⁶ /kg allogeneic MSCs 6 months after transplantation in a single-center nonrandomized phase Ib trial, followed by lowering of tacrolimus (trough level 3 ng/mL) in combination with everolimus and prednisone. Primary end point was safety, measured by biopsy proven acute rejection (BPAR) and graft loss 12 months after transplantation. Immune monitoring was performed before and after infusion. No BPAR or graft loss occurred and renal function remained stable. One patient retrospectively had DSAs against MSCs, formed before infusion. No major alterations in T and B cell populations or plasma cytokines were observed upon MSC infusion. Administration of HLA selected allogeneic MSCs combined with low-dose tacrolimus 6 months after transplantation is safe at least in the first year after renal transplantation. This sets the stage to further explore the efficacy of third-party MSCs in renal transplantation.

Keywords: clinical research/practice; clinical trial; immune regulation; immunosuppression/immune modulation; kidney transplantation/nephrology; monitoring: immune; stem cells.

FIGURE 1

Schematic presentation of study interventions and immunosuppressive regimen. Patients received induction therapy with alemtuzumab (Campath^®) 15 mg on day 0 and day 1 after transplantation [Tx]). Prednisolone started on day 0 with 500 mg, 250 mg on day 1, 125 mg on day 2, 100 mg on day 3, 50 mg on day 4, and 10 mg/day from day 5, then reduced to 7.5 mg after 3 months (week 12) and to 5 mg at 6 months (week 26). Target trough level of everolimus (Certican^®) was 3‐8 ng/mL. The tacrolimus (Advagraf^®) target was 8‐10 ng/mL the first 6 weeks post Tx, 4‐7 ng/mL from 6 to 24 weeks, and lowered to 1.5‐3 ng/mL at week 26. A renal biopsy was performed 24 weeks after transplantation, before MSC infusion, and 52 weeks after transplantation. In week 25 and week 26 1‐2 × 10⁶/kg allogeneic MSC were infused. W, weeks; Tx, transplantation; MSC, mesenchymal stromal cells; C0, trough level

FIGURE 2

MSC selection procedure regarding HLA matching. This figure shows the method of MSC selection for patient 3. In this patient the HLA mismatch with the kidney donor was 1‐2‐1 (and 1 for HLA DQ). MSC1 has three repeated mismatches, HLA‐B, HLA‐DR, and HLA‐DQ, therefore the product was not selected. MSC2 has mismatches with the recipient (1‐2‐0, 0) but no repeated mismatches between the mismatches with the kidney donor, so this product was selected for infusion. HLA, human leukocyte antigen; MSC, mesenchymal stromal cells

FIGURE 3

Kidney function before and after MSC infusion. The table on the left shows the values of the Chronic Kidney Disease Epidemiology Collaboration (CKD‐EPI) compared to the iohexol clearance in mL/min measured 24 and 52 weeks after kidney transplantation. In patient 3 iohexol clearance at week 24 is missing due to 1 missing laboratory measurement. Mean renal function is the mean of all patients. The figure on the right shows the eGFR calculated with CKD‐EPI formula for all 10 patients during study follow‐up. Week 0 is calculated just before transplantation, week 24 is the moment of renal biopsy, before MSC infusions (week 25 and 26). W, week; eGFR, estimated glomerular filtration rate; MSC, mesenchymal stromal cells

FIGURE 4

Sirius Red scores. This figure shows in the table on the left the Sirius Red score in percentages scored for the first biopsy at 6 months after transplantation (before MSC infusion) and the second biopsy 12 months after transplantation. The last patient had a vital anticoagulation indication (transient ischemic attack) so no renal biopsy was performed and therefore this value is missing. Two biopsies were shown as example, the biopsy of patient 8 had an important improvement of Sirius Red score, which is also seen in the picture. The second example from patient 9 had a stable Sirius Red score. MSC, mesenchymal stromal cells.

FIGURE 5

Leukocytes before and after MSC infusion. Absolute numbers of (A) CD45⁺ leukocytes, (B) CD19⁺ B cells, (C) CD14⁺ monocytes, and (D) CD56⁺ NK cells are shown at baseline before transplantation, so before induction therapy, before the first MSC infusion (week 25) and before the second MSC infusion (week 26) and three time points after both infusions (week 27, week 34, and week 52). Median values are given for every time point (horizontal bars). The y‐axis is a logarithmic scale. P values are given for the differences between week 25‐26 (after the first infusion), week 26‐27 (after the second infusion), and for week 25‐27 (before MSC infusion and after both infusions). The P value given at week 52 is the difference before transplantation (week 0) and week 52. MSC, mesenchymal stromal cells; NK, natural killer

FIGURE 6

T cell subsets before and after MSC infusions. Absolute numbers of (A) CD8⁺ T cells, (B) CD4⁺ T cells, (C) naïve Tregs, and (D) memory Tregs are shown at baseline before transplantation, so before induction therapy, before the first MSC infusion (week 25) and before the second MSC infusion (week 26) and three time points after both infusions (week 27, week 34, and week 52). In the population of naïve Treg cells there were one and two patients respectively with a value of 0 cells in week 26 and week 27, these values were not plotted. Median values are given for every time point (horizontal bars). The y‐axis is a logarithmic scale. P values are given for the differences between week 25‐26 (after the first infusion), week 26‐27 (after the second infusion), and for week 25‐27 (before MSC infusion and after both infusions). The P value given at week 52 is the difference before transplantation (week 0) and week 52. MSC, mesenchymal stromal cells; Treg, regulatory T cell

FIGURE 7

Cytokine levels of TNFα, IL4, IL10, and IFNγ and before and after MSC infusion. Levels of (A) TNFα, (B) IL4, (C) IL10, and (D) IFNγ, measured by multiplex assays before and 4 hours after the first and second MSC infusion (week 25 and week 26 after transplantation). IL, interleukin; IFN, interferon; MSC, mesenchymal stromal cells; TNF, tumor necrosis factor

FIGURE 8

All (serious) adverse events were classified according to MedDRA^® (Medical Dictionary for Regulatory Activities). During follow‐up 12 serious adverse events and 105 adverse events occurred. Most frequent reported adverse events are infectious problems. There were no adverse events directly related to the MSC infusions. MSC, mesenchymal stromal cells