ALBERT

Description: Introduction: The outcome of allo-SCT in patients with hematological malignancies is still hampered by GVHD and relapse. Specific depletion of αβ T- cells is proposed to result in a decreased incidence of aGVHD, whereas the remaining innate cells such as NK cells and γδT cells may provide control of infected and transformed cells the first months post SCT. This strategy has been pioneered in haploindentical transplantation with promising results. Within this study, we extend αβT- cell depleted allo-SCT to patients with a matched related and unrelated donor. The primary aim is to develop an allogeneic SCT protocol with a low incidence of aGVHD without an increased incidence of infections or relapse to serve as a platform for post-allo interventions such as a pre-emptive DLI or transfer of genetically modified T cells. Methods: Patients with hematological malignancies (including AML, ALL, MM, NHL) who received an αβT-cell depleted allo-SCT of a HLA matched sibling (MRD) or HLA matched (9 or 10/10) unrelated donor (MUD) were analysed. αβT-cell reduction was performed by negative selection with anti-αβTCR antibodies in combination with magnetic microbeads, using the automated CliniMACS device (Miltenyi Biotec, Bergisch Gladbach, Germany). The maximal contamination with αβT-cells was 5x105/kg. The conditioning regimen consisted of: ATG (Genzyme®) 6 mg/m2 + fludarabine 120 mg/m2 + busilvex AUC=90. Immune suppression consisted of 28 days of mycophenolic acid. A cohort of 32 patients was retrospectively analyzed for clinical parameters including immune reconstitution, engraftment, infections, GVHD, relapse, NRM and OS and compared to an historical control cohort of recipients of a T cell replete allo-SCT. In addition in a subset of patients NGS of the TCRβ chain was performed using the Illumina/MiSeq sequencing platform after isolation diverse immune subsets within the αβT-cell repertoire. Results: The combination of ATG/fludarabine/busilvex was well tolerated with hematological recovery within 3 weeks. Primary engraftment (chimerism 〉 95%) was observed in all patients (n=32). Immune reconstitution primarily consisted of NK cells. In addition, γδT cells were detectable at normal numbers the first half year post SCT, whereas the adaptive immune repertoire showed a delayed reconstitution. As compared to the historical control cohort, the incidence of CMV (54% vs 38%; p = 0,48) and EBV (32% vs 9%' p=0,148) infections did not show a significant increase. The incidence of aGVHD 〉 grade II within 100 days in patients of a αβT-cell depleted allo-SCT was 0%. During this relative short time of follow-up (1-14 months) 2 patients developed a relapse (both 〉 6 months) and 2 patients deceased (one with mucormycosis, one with GVHD post DLI). With NGS of the TCRβ repertoire, a surprising diversity was observed in defined immune subsets ranging from clonal expansion of regulatory T cells to broad repertoires in effector memory cells. Conclusion: αβT-cell depletion in MRD/MUD results in a swift reconstitution of innate cells (NK cells and γδT-cells) the first 6 months post transplantation, followed by a subsequent reconstitution of the adaptive immune repertoire. The diversity appears to be different for diverse subsets of the αβT-cell repertoire, which remains to be confirmed in an extended pool of patients. The incidence of severe aGVHD is low, without a significant increase in infections or relapse shortly post allo-SCT. These results will be confirmed during extended follow-up and in a planned prospective multicenter study. Disclosures No relevant conflicts of interest to declare.

Description: Introduction: We report the first analysis of a multicenter prospective single-arm phase I/II study that assesses the safety and feasibility of transplantation of TCRalpha/beta depleted stem cells from matched related or unrelated donors using the CliniMACS plus System (Miltenyi Biotec, Germany) in combination with a non-myeloablative conditioning in adult patients (trial nr NL48606.000.14). The conditioning regimen consisted of ATG (Thymoglobulin®) 1.5mg/kg i.v. days -12 to -9; fludarabine i.v. 40 mg/m2 days -5 to -2 and busulfan i.v. (Busivex®) days -5 to -2 (cumulative AUC of 80-90mg*h/L), followed by 28 days of mycophenolic acid. All 35 subjects were eligible to address the primary endpoint which is the incidence of acute GVHD at day 100. Results: 2 centers enrolled 10 female and 25 male patients (median age 59 years, range 19 - 69 years), including 9 AML, 4 ALL, 2 CML, 5 MM, 1 NHL, 10 MDS, 4 MPN. Diseases were in CR (n=17), VGPR (n=1), PR (n=5) or non-remission (n=12). 4 subjects had one or more previous allogeneic SCTs. Donors included 4 MRD, 24 10/10 matched MUD and 7 9/10 matched MUD. 8 male patients received stem cells of female donors. The median number of CD34+ cells and αβ TCR cells/kg was 6.1x 10^6 (range, 1.9-10) and 14.5x10^3 (range, 0-136), respectively. One primary graft failure was observed. Primary engraftment of ANCs 〉 500 cells/μL was reached at a median of 14 days (range 9 - 48 days) and of platelets 〉 20 at a median of 17 days (range 10 - 99) days. The median time of follow-up of this first analysis was 190 days (range 110-400 days). 3/35 patients developed acute GVHD grade III-IV during the first 100 days, 9/35 patients developed acute GVHD grade II-IV and 16/35 patients grade I-IV at day 100. At day 100 the cumulative incidence (CI) of CMV was 31%, of EBV 36% and of BK cystitis 20%. The combined CI of CMV/EBV/BK infections with a CTC-AE grade III-V was 53% at day 100. Immune reconstitution was rapid with a median of 227 (range 34 - 1626) CD3+ cells/µl on day 100 but varied substantially between patients. The median numbers of CD3/CD4+ and CD3/CD8+ at day 100 post transplant were 60 (range 30 - 120) and 124 (range 5 - 1450) cells/µl. The median numbers of NK were 289 (range 32-1140) at day 30 and 128 (range 24 - 1228) cells/µl at day 100 post transplant. The median numbers of γδ T cells were 38 (range 4-143) at day 30 and 50 (range 8-556) cells/µl at day 100 post transplant. 26 out of 35 patients were alive, 2 patients died of a relapse, 2 of GVHD and 5 of infectious complications. Kaplan Meier estimates of the OS are 88% (+/- 6%) at day 100 and 68% (+/- 9%) at 1Y. Kaplan Meier estimates of the EFS are 77% (+/- 7%) at day 100 and 52% (+/- 10%) at 1Y. 2 patients developed a relapse before day 100 and 5 patients before 1Y. It is noted that the outcome of 5 patients with MM was very poor in this cohort (3 patients developed a relapse and 2 patients died of complications). Conclusion: Allo-SCT of αβ T cell depleted PBMCs form matched related or unrelated donors, in combination with early ATG and a non-myeloablative conditioning regimen, resulted in favorable rates of primary engraftment (34/35), a CI of aGVHD II-IV of 26% with only minimal immuno-suppression and an encouraging early disease control (Fig 1). OS survival was mainly impacted by NRM (Fig 1), by which the majority of complications were of infectious nature. While all patients with MM suffered from NRM or relapse, all other disease categories had a rather favorable outcome. Reducing inter-individual variations in immune reconstitution early after transplantation will be key to further improve outcomes. Disclosures Minnema: Amgen: Consultancy; Takeda: Consultancy; Celgene: Consultancy, Research Funding; Janssen: Consultancy; Servier: Consultancy. Kuball:Novartis: Research Funding; Miltenyi Biotec: Research Funding; Gadeta (www.gadeta.nl): Consultancy, Equity Ownership, Patents & Royalties: on gd T cells and receptors and isolation strategies, Research Funding.

Description: Adoptive transfer of T-cell receptor (TCR) genes has been proposed as an attractive approach for immunotherapy in cases where the endogenous T-cell repertoire is insufficient. While there are promising data demonstrating the capacity of TCR-modified T cells to react to foreign antigen encounter, the feasibility of targeting tumor-associated self-antigens has not been addressed. Here we demonstrate that T-cell receptor gene transfer allows the induction of defined self-antigen–specific T-cell responses, even when the endogenous T-cell repertoire is nonreactive. Furthermore, we show that adoptive transfer of T-cell receptor genes can be used to induce strong antigen-specific T-cell responsiveness in partially MHC-mismatched hosts without detectable graft versus host disease. These results demonstrate the feasibility of using a collection of “off the shelf” T-cell receptor genes to target defined tumor-associated self-antigens and thereby form a clear incentive to test this immunotherapeutic approach in a clinical setting.

Description: Minor histocompatibility antigen (MiHAg) differences between donor and recipient in MHC-matched allogeneic hematopoietic stem cell transplantation (allo-HSCT) often result in graft-versus-host disease (GVHD). While MiHAg-specific T-cell responses can in theory be directed against a large number of polymorphic differences between donor and recipient, in practice, T-cell responses against only a small set of MiHAgs appear to dominate the immune response, and it has been suggested that immunodominance may predict an important contribution to the development of GVHD. Here, we addressed the feasibility of graft engineering by ex vivo removal of T cells with 1 or more defined antigen specificities in a well-characterized experimental HSCT model (B6 → BALB.B). We demonstrate that immunodominant H60- and H4-specific CD8+ T-cell responses can be effectively suppressed through MHC class I tetramer–mediated purging of the naive CD8+ T cell repertoire. Importantly, the development of GVHD occurs unimpeded upon suppression of the immunodominant MiHAg-specific T-cell response. These data indicate that antigen-specific graft engineering is feasible, but that parameters other than immunodominance may be required to select T-cell specificities that are targeted for removal.

Description: To assess the safety and efficacy of nonmyeloablative allogeneic transplantation in patients with HIV infection, a clinical protocol was initiated in patients with refractory hematologic malignancies and concomitant HIV infection. The results from the first 2 patients are reported. The indications for transplantation were treatment-related acute myelogenous leukemia and primary refractory Hodgkin disease in patients 1 and 2, respectively. Only patient 1 received genetically modified cells. Both patients tolerated the procedure well with minimal toxicity, and complete remissions were achieved in both patients, but patient 2 died of relapsed Hodgkin disease 12 months after transplantation. Patient 1 continues in complete remission with undetectable HIV levels and rising CD4 counts, and with both the therapeutic and control gene transfer vectors remaining detectable at low levels more than 2 years after transplantation. These results suggest that nonmyeloablative allogeneic transplantation in the context of highly active antiretroviral therapy is feasible in patients with treatment-sensitive HIV infection.