Sustained Donor Chimerism and Rapid Immune Cell Reconstitution with a Low Probability of Gvhd Following Familial Haploidentical (FHI) CD34 Enriched Stem Cell Transplantation with Pbmnc Addback in Patients with High Risk Sickle Cell Disease (SCD) (IND 14359)

Abstract

Background Allogeneic stem cell transplantation (AlloSCT) from an HLA-matched sibling donor is the only known curative therapy in high-risk SCD patients (Talano/Cairo, EJH, 2015). Unfortunately only about 15% of high-risk SCD patients have an HLA-matched unaffected sibling donor. T cell depletion has been employed to reduce AGVHD. We reported a very low incidence of GVHD in pediatric recipients receiving CD34 enriched HPC products with PBMNC addback from MUD donors (Geyer/Cairo et al, BJH, 2012). Rapid NK cell reconstitution after AlloSCT is associated with a significant improvement in 1yr OS (Pical-Izard, BBMT, 2015). Recently, we reported promising results for high-risk SCD patients at 1 yr follow-up after FHI CD34 enriched/PBMNC with addback with the probability of 1-yr OS 88.2% (Cairo, et al, JAMA Peds, 2019). Objective To investigate donor chimerism, immune reconstitution and the incidence of GVHD in high-risk SCD patients following AlloSCT using FHI CD34 enrichment/PBMNC (2 × 105 CD3/kg) addback. Methods CD34 cells were enriched using the CliniMACS® system, kindly provided by Miltenyi Biotec, with a target dose of 10 × 106 CD34+ cells/kg. PBMNC were added back to the final CD34 product at a dose of 2 × 10*5 CD3/kg. Whole blood and CD71-enriched erythroid lineage chimerism were determined by STR. Immune cell, subset reconstitution, NK function, CD107a and granzyme B were assessed by flow cytometry as previously described (Geyer/Cairo et al. BJH, 2012, Chu/Cairo et al, Can Imm Res, 2015). Results The cumulative incidence of grade II-IV and late AGVHD was 6.2 % and moderate and/or severe CGVHD incidence was 6.7%, respectively (Fig. 1A). There was 100% engraftment of neutrophils and platelets. The median day post-HISCT to neutrophil and platelet engraftment was +9 and +19, respectively. Whole blood donor chimerism (mean±SEM) at 1-yr, 2-ys, and 3-ys post-HISCT was 97±1%, 97±1%, 97±1%, respectively (Fig.1B). Donor chimerism for CD71-enriched erythroid lineage cells (mean±SEM) at 1-yr, 2-yrs, 3-yrs post-HISCT was 97±2%, 98±1%, 98±1%, respectively (Fig.1B). The time to recovery of minimal normal levels for CD3 (800 cells/ul), CD4 (400 cells/ul), CD8 (200 cells/ul), & CD19 cells (200 cells/ul), was approximately 365, 365, 270, and 60 days post-HISCT, respectively (Fig.1C). NK reconstitution was rapid and peaked at d+30 (36±9%) with higher level of activating receptors NKp46, NKG2D & KIR2DS and inhibitory receptors NKG2A, CD94 and KIR2DL2/3. NK cytotoxicity against K562 (E:T = 10:1) peaked at d+30 and d+180 vs pre-transplant (p Conclusion The PBMNC addback facilitated rapid donor chimerism & immune reconstitution with a low probability of Grade II-IV AGVHD. The rapid NK reconstitution may have in part contributed to the excellent 1yr OS in this study (FDA R01FD004090 (MSC)). This approach is comparable to the method of CD3 TCRa/b-CD19 depletion.