ALBERT

Description: This paper compares the metal/semiconductor barrier height properties of non-recessed Ti/Al/Ti and Ta/Al/Ta contacts on AlGaN/GaN heterostructures. Both contacts exhibited a rectifying behavior after deposition and after annealing at temperatures up to 550 °C. The ohmic behavior was reached after annealing at 600 °C. High-resolution morphological and electrical mapping by conductive atomic force microscopy showed a flat surface for both contacts, with the presence of isolated hillocks, which had no significant impact on the contact resistance. Structural analyses indicated the formation of the Al3Ti and Al3Ta phases upon annealing. Furthermore, a thin interfacial TiN layer was observed in the Ti/Al/Ti samples, which is likely responsible for a lower barrier and a better specific contact resistance (ρc = 1.6 × 10−4 Ωcm2) with respect to the Ta/Al/Ta samples (ρc = 4.0 × 10−4 Ωcm2). The temperature dependence of the specific contact resistance was described by a thermionic field emission mechanism, determining barrier height values in the range of 0.58–0.63 eV. These results were discussed in terms of the different microstructures of the interfaces in the two systems.

Description: Introduction: Cytomegalovirus (CMV) reactivation and disease are important risk factors after allogeneic hematopoietic stem cell transplantation (allo-HSCT), and strongly affect morbidity and mortality after transplant. CMV-specific T cell reconstitution controls CMV reactivation and protects against serious adverse events but a protective level of CMV-specific T cell response or standardized method for its monitoring have not been yet determined. Methods: We designed a prospective, single-center observational study to assess if the kinetic and quality of CMV specific T-cell reconstitution impact the incidence and severity of CMV reactivations. We have enrolled 84 consecutive patients affected by hematological malignancies receiving allo-HSCT followed by Cyclophosphamide and Rapamycin between December 2017 and February 2019. Here we report preliminary data on the first 61 patients. Patients received allo-HSCT from family (siblings=10; HLA haploidentical=24), unrelated HLA-matched (n= 24) donors or cord blood (CB, n=3). The CMV serostatus of host (H) and donor (D) pairs was: H+/D+(n=40, 65%), H+/D-(n=20, 33%) and H-/D+ (n=1, 2%); H-/D-(7% of the overall transplanted population at our center) were excluded. CMV DNAemia was assessed weekly in whole blood (WB). Absolute numbers of polyclonal and CMV-specific T cells were quantified by flow cytometry using Troucount™Tubes (BD) and Dextramer®CMV-Kit (Immudex), respectively, in the graft and fresh WB at days -7, +30, +45, +60, +90, +120, +150, +180 and +360. Dextramer CMV kit includes reagents for the identification of CMV-specific lymphocytes restricted for several HLA class I molecules: A*01:01/*02:01/*03:01/*24:02 and B*07:02/*08:01/*35:01. These alleles allowed the longitudinal evaluation of 54 out of 61 (89%) patients. Results: At a median follow-up of 226 days post-HSCT, 31 (57%) patients experienced a CMV-related clinically relevant event (CRE, median +63 days), including 8 patients (15%) with CMV disease (median +59 days). Univariate analyses showed that the incidence of CMV clinically-relevant reactivation (CRE) was influenced by H/D CMV serostatus (0.90 in H+/D- versus 0.44 in H+/D+pairs, p=0.015) and by previous acute Graft-versus-Host Disease (aGvHD) requiring systemic immunosuppression (0.82 in aGvHD grade II-IV versus 0.52 in aGvHD grade 0-I, p=0.051). The disease status at transplant, the donor type (HLA-matched versus HLA-haploidentical/CB donors), donor's or host's age did not significantly affect the probability to develop CRE. For each time-point, we compared the absolute number of CMV-specific lymphocytes in patients experiencing or not a subsequent CRE. Our data demonstrate that higher levels of CMV-specific CD8+T cells in the donor apheresis and at +45 days after allo-HSCT are associated with reduced risk of subsequent CRE (median CMV-specific CD8+cells/kg in the apheresis=5x103in CRE-positive patients (CRE+) and 5x105in CRE-negative patients (CRE-), p=0.012; median CMV-specific CD8+at +45 days=0.14 cells/μL in CRE+and 1.21 cells/μL in CRE-, p=0.034). Furthermore, patients with any Dextramer positivity at +45 days displayed a lower incidence of CRE compared with subjects who were negative (CRE probability: 0.5 vs 1.0, p=0.003). Conversely, the absolute number of neither polyclonal CD3+CD8+T lymphocytes nor total CD3+T cells correlate with subsequent CRE. Taking advantage of the HLA mismatched-HSCT setting, we then dissected CMV-specific T-cell response according to HLA restriction elements (H/D=shared n=45, D-restricted n=14, H-restricted n=11). In H+/D+pairs, we observed a fast and similar kinetic of reconstitution of CMV-specific lymphocytes restricted by H/D and D HLAs. Conversely, in H+/D-pairs, we detected only CMV-specific CD8+lymphocytes restricted for H/D haplotypes. Host-restricted cells remained undetectable for the first 180 days after HSCT. Conclusion: Early after allo-HSCT and in the donor apheresis, the level of CMV-specific CD8+T cells measured by Dextramer staining differs in patients experiencing or not subsequent CRE. Furthermore, our findings indicate that CMV reactivations can prime H/D-restricted T cells presumably educated in the donor thymus; conversely, D- and H-restricted donor-derived lymphocytes have not yet undergone neither cross-priming nor thymic education respectively. Disclosures Brix: Immudex: Employment. Bonini:Kite/Gilead: Consultancy; Intellia Therapeutics: Consultancy; Intellia Therapeutics: Research Funding; Novartis: Consultancy; GSK: Consultancy; Allogene: Consultancy; Molmed: Consultancy; TxCell: Consultancy; -: Patents & Royalties: Adoptive T cell therapy field.

Description: BACKGROUND: Suicide gene therapy applied to haploidentical hematopoietic stem cell transplantation (haplo-HSCT) is one of the widest clinical applications of gene therapy. By the infusion of donor lymphocytes transduced to express the Herpes Simplex Virus Thymidine Kinase (TK) suicide gene, patients achieve a rapid immune reconstitution and substantial protection against tumor recurrence. TK-cells are promptly eliminated in case of graft versus host disease (GvHD), with complete resolution of the adverse reaction. In previous studies, we showed that TK-cell infusions are necessary and sufficient to promote the generation of a fast, polyclonal and full competent T cell repertoire. In the present work we characterize the immunological profile of a cohort of long-term survivors after suicide gene therapy and we studied the long-term fate of TK-cells to shed light on memory T cell dynamics after transplantation. RESULTS: We studied 9 adult patients who underwent haplo-HSCT and infusion of purified suicide-gene modified donor T cells (median dose: 1.9x107 cells/kg, range:0.9x106-39.5x106) for high-risk hematologic malignancies between 1995 and 2010 (TK patients). At a median follow-up of 7,4 years (range 3.2-12.3), all patients are in complete remission. Two out of 9 patients (22%) experienced GvHD in the early phase post immune reconstitution; in all cases, ganciclovir (GCV) administration proved effective in abrogating the adverse reaction. No symptoms or complications related to GvHD were observed during the long-term follow up, and none of the patient is receiving immunosuppressive drugs. A complete recovery of NK cells, B lymphocytes and αβ or γδ T cells was observed. The CD8+ and CD4+ T cell compartment of TK patients were characterized by level of naïve and memory cell comparable to age and sex matched healthy controls. The quantification of CD4+ CD31+ CD62L+ CD45RA+ CD95- recent thymic emigrants and measure of single joint T-cell receptor excision circles demonstrated that the normalization of the T cell compartment was supported by a completely recovered thymic output. TK-cells were detected in all patients (100%), at low levels (median=4cells/uL). Ex vivo selection of pure TK-cells after polyclonal stimulation and LNGFR-purification confirmed the presence of functional transduced cells, thus directly demonstrating the ability of memory T cells to persist for years. Of notice TK-cells could be retrieved also in patients successfully treated with GCV for GvHD, thus confirming the selective action of GCV only on proliferating TK-cells. Accordingly, GCV sensitivity was preserved in long-term persisting TK-cells, independently from their differentiation phenotype. TK-cells circulating in patients displayed a memory phenotype comprising effector memory (TEM), central memory (TCM) and stem memory (TSCM) T cells and exhibited a low level of Ki-67 positivity, thus suggesting the maintenance of a pool of gene modified memory cells through homeostatic proliferation. The number of TK-cells circulating at the longest follow-up did not correlate with the number of infused cells, nor patients or donors’ age, but instead with the peak of TK-cells observed within the first months after infusion, suggesting that antigen recognition is dominant in driving in vivo expansion and persistence of memory T cells. We evaluated whether the phenotype of infused TK-cells was able to affect the long-term fate of gene-modified memory T cells. We observed that the number of infused TSCM cells positively correlated with early TK-cell expansion and with their long-term persistence, suggesting that TSCMmight play a privileged role in the generation of a long-lasting immunological memory. CONCLUSION: These data show that a complete and physiological donor-derived immune system is restored in adult surviving long-term after suicide gene therapy. After infusion, gene modified cells persist for up to 12 years in treated patients. This setting can be exploited to investigate the requirements at the basis of the generation of a long-lasting immunological memory in vivo. Further studies on TK-cell TCR repertoire and vector integrations are currently being performed to elucidate the in vivo dynamics of infused memory T cells. Disclosures Lambiase: MolMed S.p.A: Employment. Traversari:MolMed S.p.A: Employment. Bordignon:MolMed S.p.A: Chairman and CEO Other. Bonini:MolMed S.p.A: Consultancy.

Description: Abstract 1968 BACKGROUND: The genetic modification of T cells with a suicide gene grants a mechanism of control of Graft-versus-Host Disease (GvHD), allowing safe infusion of donor lymphocytes after partially HLA-incompatible Hematopoietic Stem Cell Transplantation (HSCT). In the TK007 phase I-II clinical trial, which enrolled a total of 54 adults with hematologic malignancies, 22 of the 28 treated patients experienced a rapid and sustained immune recovery after T cell-depleted HSCT and serial infusions of purified donor T cells expressing the Herpes Simplex Virus Tymidine Kinase suicide gene (TK cells; Ciceri and Bonini et al., Lancet Oncology, 2009). In these patients, after a first wave of circulating TK cells, the majority of T cells supporting long-term immune reconstitution did not carry the suicide gene and displayed high numbers of naïve lymphocytes, leading us to hypothesize a thymus-dependent development of T cells, occurring only upon TK cell engraftment. METHODS: Thymic function was investigated in a total of 31 patients enrolled in the TK007 trial (median age 55 years), which were compared to a cohort of adult patients receiving non T cell-depleted haploidentical transplantation (n=31), and to healthy pediatric and adult subjects. T cell subsets and the proportion of CD31+ recent thymic emigrants amongst CD4 naïve T cells were measured by immunophenotypic analysis. Single joint T cell Receptor Excision Circles (sjTREC) were quantified by qPCR. The volume of the biologically active thymus was assessed by chest CT scans. Serum concentration of cytokines was assessed by a multiplex luminex-based assay. Pathogen-specific immunity was quantified by interferon-γ ELISpot. RESULTS: After the infusion of TK cells we documented a significant increase in peripheral blood sjTRECs as compared to the pre-HSCT determination (p = 0.02), suggesting an improved thymic output. Importantly, in line with that, only in TK007 patients almost the totality of CD4 naïve T cells circulating after transplantation were CD31+, thus bona fide recent thymic emigrants (89.54±9.55% at immune reconstitution, 81.84±15.9% at 6 months after HSCT, and 79.55±16.66% at 12 months after HSCT). Accordingly, a substantial expansion of the active thymic tissue was observed at chest tomography scans as compared to the pre-HSCT counterparts (p 〈 0.0001). A peculiar observation, possibly linked to the renewal of thymic activity and unique to the TK007 patients who achieved immune reconstitution, was the documentation of a peak in the serum level of interleukin-7, reproducibly occurring after each infusion of suicide gene-modified cells and anticipating the appearance of the newly generated T cells. Ultimately, the development of a wide repertoire of T cells in the patient thymus from donor precursors ensured a long-term protective immunity against pathogens, as exemplified by the preservation of a physiological and protective response against viruses both ex vivo and in vivo, even after the elimination of the infused TK cells in case of GvHD. CONCLUSIONS: Our data from TK007 patients show that the infusion of genetically modified donor T cells after transplantation can drive the recovery of thymic activity in adults, leading to long-term immune reconstitution. On the lead of the encouraging biological and clinical results of the phase I-II clinical trial, demonstrating a dramatic decrease in late infectious mortality, a multicenter, phase III clinical trial (TK008 study) to assess the efficacy of TK cells in the context of haploidentical HSCT for leukemia started in 2010 at the San Raffaele Institute, and is currently expanding to multiple centers throughout Europe and US. Main endpoints of this randomized phase III trial are disease free survival and overall survival. The first TK008 patients randomized to receive suicide gene-modified cells showed recovery of thimyc activity and concomitantly achieved a rapid and robust T cell immune reconstitution. Disclosures: Bonini: MolMed SpA: Consultancy.

Description: Introduction Allogeneic stem cell transplantation (allo-HCT) survivors are at a defined relevant risk of developing long-term complications: the prevalence of chronic health conditions approaches 75% among HCT survivors. The endocrine system is one of the most frequent targets of complications, providing justification for a long-term and continuous follow-up (LTFU) to assure a timely and appropriate treatment. The aim of our study is to evaluate the incidence of endocrinopathies in survivors in respect of sex, age, donor type, conditioning regimen and GvHD occurrence. Methods A standardized LTFU is applied at our center. We here analyze data consecutively collected in an Institutional database, starting from 2006, including 402 adult patients (pts) who underwent an allo-HCT between 1992 and 2016 at our Institution. A written consent was given by pts allowing the use of medical records for research in accordance with the Declaration of Helsinki. We considered for the analysis pts with an overall survival 〉/=1y. We reviewed pts chapters with a focus on occurrence, management and treatment of diabetes, thyroid disfunctions, dyslipidemia and osteopenia / osteoporosis: diagnosis and follow-up were performed according to guidelines for long-term HCT survivors. Results With a median follow-up of 7y (r 2-25y) 328 pts were evaluable; donor was a match unrelated donor in 107 cases, HLA identical sibling in 88, haploidentical relative in 129 and cord blood in 4. The 5y-incidence of diabetes type 2 was 3%, with a median time after allo-HCT of 1138 days (r 5-4181 days); 13/22 developed diabetes after diagnosis of GvHD (median time 884 days, r 30-3753 days). All pts received indication for diet modification, 11 pts were treated with insulin and 8 pts with metformin. Thyroid disfunction was documented in 38 pts (5y-incidence 8,5%): 2 pts were diagnosed with hyperthyroidism and treated with methimazole or radioiodine treatment. Hypothyroidism was documented in 36 pts (median time after allo-HSCT 799 days, r 65-5021 days). Thirteen pts developed hypothyroidism following the diagnosis of GvHD (median time 1236 days, r 166-3540 days). Only 2 pts did not receive a specific treatment, while all the others received substitutive therapy with levothyroxine. Furthermore 1 pt was diagnosed with a papillary thyroid cancer. The 5y-incidende of dyslipidemia was 30% with a median time after allo-HSCT of 1433 days (r 366-7629), 47 pts developed dyslipidemia after the diagnosis of GVHD (median time 1425 days, r 134-7403 days). Diet-therapy was recommended to all the pts, 29 pts received a statin-based pharmacological treatment, 20 pts a polyenoic-fatty-acids based treatment, while a nutraceutical compound was given in 13 pts. Osteopenia was documented in 120 pts (median time after allo-HSCT 994 days, range 31-6605 days) with a 5y-incidence of 36%. Seventy-nine pts presented osteopenia after diagnosis of GvHD (median time after GvHD diagnosis 707 days, r 13-6379 days). Eight pts did not receive a specific treatment. Two pts received treatment with biphosphonates plus oral vitamin D and calcium supplementation, the 110 remaining pts received oral vitamin D +/- calcium supplementation only. Sixty-four pts developed osteoporosis (median time after allo-HSCT 1000 days, r 60-8836 days), the 5y-incidence was 26%. Forty-four pts developed osteoporosis following the diagnosis of GvHD (median time 724 days, r 28-8280 days). Only 4 pts did not receive any specific therapy; 31 pts received therapy with bisphosphonates, 2 pts denosumab and 27 pts oral vitamin D and calcium supplementation. In univariate analysis no relationship between host sex, age at transplant, TBI exposure, donor or history of GvHD and development of diabetes, thyroid disfunction and dyslipidemia was outlined. Otherwise, osteopenia development was strongly associated with GvHD occurrence and osteoporosis was strongly associated with age, sex and GvHD occurrence (table 1). Conclusions Allo-HCT survivors are at relevant risk of endocrinopathies after transplantation, providing justification for specific monitoring to individualize treatment and follow-up. Of note, classical transplant-related variables are not enough to justify the occurrence of endocrinological disfunction: a further deeper evaluation of a misdiagnosed donor-mediated autoimmune predisposition will be essential. Disclosures Bonini: Intellia Therapeutics: Research Funding.

Description: Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the only cure for several patients with high-risk hematological malignancies. Recent advances in supportive therapies have significantly reduced the treatment-related mortality over the last decades. Nevertheless graft-versus-host disease (GvHD) still represents a major complication, and research is needed to achieve further progress in this area of transplantation. Moreover, although initial studies suggested relative equivalence, recent and large prospective studies showed higher rates of acute and chronic GvHD, and worse survival in allo-HSCT from unrelated donors (URD) compared with HLA-identical sibling donors. Following our encouraging results in haplodentical setting with the more recently post-transplantation cyclophosphamide (PTCy) and sirolimus as GvHD prophylaxis (Cieri et al, 2015), in this study we investigated whether the incorporation of low dose anti-thymocyte globulin (ATG) to PTCy and sirolimus GvHD prophylactic approach, may alleviate some of the increased alloreactivity associated with URD transplants. We retrospectively evaluated a cohort of 21 haematological patients receiving URD allo-HSCT in the San Raffaele Haematology and BMT Unit, from 2013 to 2015. All subjects had high-risk hematologic malignancies, with the most common diagnosis being myeloid diseases (52%). A total of 11 patients had active disease at HSCT, while 9 were in hematologic remission. Nine patients scored high according to disease risk index defined by Armand et al, 10 scored intermediate, while only 2 had a low disease score. Myeloablative conditioning consisted of treosulfan (14 g/m2/day) on days -6 to -4, fludarabine (30 mg/m2/day) on days -6 to -2, and melphalan (70 mg/m2/day) on days -2 and -1, followed by T-replete G-CSF-mobilized PBSCs (n=19) or BM grafts (n=2). Whether 12 patients received stem cells from HLA- matched URD (fully 10/10 HLA matched), the remaining 9 had one-locus HLA-mismatched from their donors. During conditioning patients received ATG-Fresenius 5 mg/kg per day IV on day -4 to -2. In vivo B-cell depletion was obtained by rituximab (i.v. 375mg/m2 given as a single dose on day -1). Postgrafting immunosuppression consisted of PTCy (50 mg/kg/day) on days 3 and 4. Sirolimus was given orally from day 5, and monitored to maintain a target therapeutic plasma level of 5-14 ng/ml. According to chimeric status and evidence of GVHD, the dosage of sirolimus was tapered during the second month post-transplantation, ending in complete withdrawal within the sixth month after HSCT. Mycophenolate mofetil (MMF) was initiated orally at 10 mg/kg t.i.d. on day 5 after HSCT, and withdrawn on day 30. Median follow up was 247 days (range 29-486) from HSCT. All patients were engrafted in a median time of 17 days (range, 14-51 days), with full donor chimerism achieved by day 30. Poor graft function was observed in 11 patients. Post-HSCT recovery of lymphocyte subsets was lengthy as compared to other unmanipulated HSCT, with a median time to CD3〉100/ml of 41 days (range, 22-389 days) by flow-cytometry, while 5 patients never reached immune reconstitution. All except one developed febrile neutropenia during aplasia. We observed a high rate of serious infections: severe pneumonia in 7 cases (5 required NIV, 4 were admitted to ICU), CMV reactivation in 13 (3 CMV disease), HHV6 reactivation in 10, BK virus haemorrhagic cystitis in 2 patients. Although the overall mortality associated with these complications was limited, as evidenced by a favourable NRM, it caused significant morbidity in patients and often required aggressive therapies, potentially contributing to poor graft function. The incidences of acute and chronic GVHD were low. A grade II-IV acute GvHD was reported in 10% patients, while five patients developed chronic GvHD (mild in 4 cases, only one moderate). Non-relapse mortality (NRM) at 100 days and 1 year was 4.8% and 20.7%, respectively. The estimated 1-year overall survival (OS) and relapse incidence were 51% and 22.5% respectively. Although limited by a small number of patients with relatively short follow-up, our study suggests that URD allo-HSCT with ATG, PTCy and sirolimus-based GvHD prophylaxis, can be very effective in preventing GvHD, but at the expense of delayed immune reconstitution and high rate of infectious complications, while warranting acceptable NRM and relapse incidence. Disclosures Bonini: MolMed S.p.A: Consultancy.