CD19/CD22 targeting with cotransduced CAR T cells to prevent antigen-negative relapse after CAR T-cell therapy for B-cell ALL.

ABSTRACT: CD19-negative relapse is a leading cause of treatment failure after chimeric antigen receptor (CAR) T-cell therapy for acute lymphoblastic leukemia. We investigated a CAR T-cell product targeting CD19 and CD22 generated by lentiviral cotransduction with vectors encoding our previously described fast-off rate CD19 CAR (AUTO1) combined with a novel CD22 CAR capable of effective signaling at low antigen density. Twelve patients with advanced B-cell acute lymphoblastic leukemia were treated (CARPALL [Immunotherapy with CD19/22 CAR Redirected T Cells for High Risk/Relapsed Paediatric CD19+ and/or CD22+ Acute Lymphoblastic Leukaemia] study, NCT02443831), a third of whom had failed prior licensed CAR therapy. Toxicity was similar to that of AUTO1 alone, with no cases of severe cytokine release syndrome. Of 12 patients, 10 (83%) achieved a measurable residual disease (MRD)-negative complete remission at 2 months after infusion. Of 10 responding patients, 5 had emergence of MRD (n = 2) or relapse (n = 3) with CD19- and CD22-expressing disease associated with loss of CAR T-cell persistence. With a median follow-up of 8.7 months, there were no cases of relapse due to antigen-negative escape. Overall survival was 75% (95% confidence interval [CI], 41%-91%) at 6 and 12 months. The 6- and 12-month event-free survival rates were 75% (95% CI, 41%-91%) and 60% (95% CI, 23%-84%), respectively. These data suggest dual targeting with cotransduction may prevent antigen-negative relapse after CAR T-cell therapy.

Betibeglogene Autotemcel Gene Therapy for Non-ß0/ß0 Genotype ß-Thalassemia.

BACKGROUND: Betibeglogene autotemcel (beti-cel) gene therapy for transfusion-dependent ß-thalassemia contains autologous CD34+ hematopoietic stem cells and progenitor cells transduced with the BB305 lentiviral vector encoding the ß-globin (ßA-T87Q) gene. METHODS: In this open-label, phase 3 study, we evaluated the efficacy and safety of beti-cel in adult and pediatric patients with transfusion-dependent ß-thalassemia and a non-ß0/ß0 genotype. Patients underwent myeloablation with busulfan (with doses adjusted on the basis of pharmacokinetic analysis) and received beti-cel intravenously. The primary end point was transfusion independence (i.e., a weighted average hemoglobin level of ≥9 g per deciliter without red-cell transfusions for ≥12 months). RESULTS: A total of 23 patients were enrolled and received treatment, with a median follow-up of 29.5 months (range, 13.0 to 48.2). Transfusion independence occurred in 20 of 22 patients who could be evaluated (91%), including 6 of 7 patients (86%) who were younger than 12 years of age. The average hemoglobin level during transfusion independence was 11.7 g per deciliter (range, 9.5 to 12.8). Twelve months after beti-cel infusion, the median level of gene therapy-derived adult hemoglobin (HbA) with a T87Q amino acid substitution (HbAT87Q) was 8.7 g per deciliter (range, 5.2 to 10.6) in patients who had transfusion independence. The safety profile of beti-cel was consistent with that of busulfan-based myeloablation. Four patients had at least one adverse event that was considered by the investigators to be related or possibly related to beti-cel; all events were nonserious except for thrombocytopenia (in 1 patient). No cases of cancer were observed. CONCLUSIONS: Treatment with beti-cel resulted in a sustained HbAT87Q level and a total hemoglobin level that was high enough to enable transfusion independence in most patients with a non-ß0/ß0 genotype, including those younger than 12 years of age. (Funded by Bluebird Bio; HGB-207 ClinicalTrials.gov number, NCT02906202.).

Anti-CD45 PBD-based antibody-drug conjugates are effective targeted conditioning agents for gene therapy and stem cell transplant.

Stem cell gene therapy and hematopoietic stem cell transplantation (SCT) require conditioning to ablate the recipient's hematopoietic stem cells (HSCs) and create a niche for gene-corrected/donor HSCs. Conventional conditioning agents are non-specific, leading to off-target toxicities and resulting in significant morbidity and mortality. We developed tissue-specific anti-human CD45 antibody-drug conjugates (ADCs), using rat IgG2b anti-human CD45 antibody clones YTH24.5 and YTH54.12, conjugated to cytotoxic pyrrolobenzodiazepine (PBD) dimer payloads with cleavable (SG3249) or non-cleavable (SG3376) linkers. In vitro, these ADCs internalized to lysosomes for drug release, resulting in potent and specific killing of human CD45+ cells. In humanized NSG mice, the ADCs completely ablated human HSCs without toxicity to non-hematopoietic tissues, enabling successful engraftment of gene-modified autologous and allogeneic human HSCs. The ADCs also delayed leukemia onset and improved survival in CD45+ tumor models. These data provide proof of concept that conditioning with anti-human CD45-PBD ADCs allows engraftment of donor/gene-corrected HSCs with minimal toxicity to non-hematopoietic tissues. Our anti-CD45-PBDs or similar agents could potentially shift the paradigm in transplantation medicine that intensive chemo/radiotherapy is required for HSC engraftment after gene therapy and allogeneic SCT. Targeted conditioning both improve the safety and minimize late effects of these procedures, which would greatly increase their applicability.

Practice guideline: Preparation for CAR T-cell therapy in children and young adults with B-acute lymphoblastic leukaemia.

The objective of this guideline, prepared by the ALL subgroup of the Advanced Cell Therapy Sub-Committee of BSBMTCT (British Society of Blood and Marrow Transplantation), is to provide healthcare professionals with practical guidance on the preparation of children and young adults with B-acute lymphoblastic leukaemia from the point of referral to that of admission for CAR T-cell treatment. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) nomenclature was used to evaluate the levels of evidence and to assess the strength of recommendations. The GRADE criteria can be found at http://www.gradeworkinggroup.org.

Management of paediatric monomorphic post-transplant lymphoproliferative disorders with low-intensity treatment: A multicentre international experience.

BACKGROUND: Monomorphic post-transplant lymphoproliferative disorder (mPTLD) is a major cause of morbidity/mortality following solid organ transplant (SOT), with infection, mPTLD progression and organ rejection presenting equal risks. Balancing these risks is challenging, and the intensity of therapy required by individual patients is not defined. Although an increasing body of evidence supports the use of a stepwise escalation of therapy through reduction in immunosuppression (RIS) to rituximab monotherapy and low-dose chemo-immunotherapy, many centres still use B-cell non-Hodgkin lymphoma (B-NHL) protocols, especially when managing Burkitt/Burkitt-like (BL) PTLD. This study sought to define outcomes for children managed in the UK or Spanish centres using low-intensity first-line treatments. PROCEDURE: Retrospective data were anonymously collected on patients younger than 18 years of age, with post-SOT mPTLD diagnosed between 2000 and 2020. Only patients given low-intensity treatment at initial diagnosis were included. RESULTS: Fifty-six patients were identified. Age range was 0.9-18 years (median 10.7). Most (62.5%) had early-onset PTLD. Haematopathological analysis showed 75% were diffuse large B-cell like, 14.3% were BL and nine of 33 (27%) harboured a MYC-rearrangement. Stage III-IV disease was present in 78.6%. All but one had RIS, 26 received rituximab monotherapy and 24 low-dose chemo-immunotherapy, mostly R-COP. Intensified B-NHL chemotherapy was required in 10/56 (17.9%). There were a total of 13 deaths in this cohort, three related to PTLD progression. The 1-year overall survival (OS), event-free survival (EFS) and progression-free survival (PFS) were 92.8%, 78.6% and 80.2%, respectively. CONCLUSIONS: R-COP provides an effective low-dose chemotherapy option. Escalation to more intensive therapies in the minority of inadequately controlled patients is an effective strategy.

Immunotherapy with CD25/CD71-allodepleted T cells to improve T-cell reconstitution after matched unrelated donor hematopoietic stem cell transplant: a randomized trial.

BACKGROUND AIMS: Delayed immune reconstitution is a major challenge after matched unrelated donor (MUD) stem cell transplant (SCT). In this randomized phase 2 multi-center trial, Adoptive Immunotherapy with CD25/71 allodepleted donor T cells to improve immunity after unrelated donor stem cell transplant (NCT01827579), the authors tested whether allodepleted donor T cells (ADTs) can safely be used to improve immune reconstitution after alemtuzumab-based MUD SCT for hematological malignancies. METHODS: Patients received standard of care or up to three escalating doses of ADTs generated through CD25+/CD71+ immunomagnetic depletion. The primary endpoint of the study was circulating CD3+ T-cell count at 4 months post-SCT. Twenty-one patients were treated, 13 in the ADT arm and eight in the control arm. RESULTS: The authors observed a trend toward improved CD3+ T-cell count at 4 months in the ADT arm versus the control arm (230/µL versus 145/µL, P = 0.18), and three ADT patients achieved normal CD3+ T-cell count at 4 months (>700/µL). The rates of significant graft-versus-host disease (GVHD) were comparable in both cohorts, with grade ≥2 acute GVHD in seven of 13 and four of eight patients and chronic GVHD in three of 13 and three of eight patients in the ADT and control arms, respectively. CONCLUSIONS: These data suggest that adoptive transfer of ADTs is safe, but that in the MUD setting the benefit in terms of T-cell reconstitution is limited. This approach may be of more use in the context of more rigorous T-cell depletion.

Pathogenesis, risk factors and therapeutic options for autoimmune haemolytic anaemia in the post-transplant setting.

Autoimmune haemolytic anaemia (AIHA) is a rare complication of allogeneic haematopoietic stem cell transplantation (HSCT), observed with an incidence of 1-5%. Paediatric age, diagnosis of non-malignant disease, lympho-depleting agents in the conditioning regimen, use of unrelated donor, graft versus host disease and infections have been associated with a higher risk of AIHA post HSCT. Post-HSCT AIHA is associated with high mortality and morbidity, and it is often very difficult to treat. Steroids and rituximab are used with a response rate around 30-50%. These and other therapeutic strategies are mainly derived from data on primary AIHA, although response rates in post-HSCT AIHA have been generally lower. Here we review the currently available data on risk factors and therapeutic options. There is a need for prospective studies in post-HSCT AIHA to guide clinicians in managing these complex patients.

Excellent overall and chronic graft-versus-host-disease-free event-free survival in Fanconi anaemia patients undergoing matched related- and unrelated-donor bone marrow transplantation using alemtuzumab-Flu-Cy: the UK experience.

Haematopoietic stem cell transplantation (HSCT) remains the only curative option in Fanconi anaemia (FA). We analysed the outcome of children transplanted for FA between 1999 and 2018 in the UK. A total of 94 transplants were performed in 82 patients. Among the donors, 51·2% were matched related donors (MRD) while the remainder were alternative donors. Most patients received a fludarabine-cyclophosphamide (Flu-Cy)-based conditioning regimen (86·6%) and in vivo T-cell depletion with alemtuzumab (69·5%). Five-year overall survival (OS) was 85·4% [70·4-93.2] with MRD, 95·7% [72·9-99.4] with matched unrelated donors (MUD), 44·4% [6·6-78.5] with mismatched unrelated donors (MMUD) and 44·4% [13·6-71.9] with mismatched related donors (MMRD) (P < 0·001). Other factors significantly impacting OS were pre-transplant bone marrow status, source of stem cells, cytomegalovirus (CMV) serostatus, preparation with Flu-Cy, use of total body irradiation (TBI) and alemtuzumab as serotherapy. In multivariate analysis, absence of myelodysplastic syndrome (MDS) or leukaemia, bone marrow as source of stem cells, cytomegalovirus (CMV) other than +/- (Recipient/Donor) and Flu-Cy were protective factors for five-year OS. Five-year chronic graft-versus-host-disease (cGVHD)-free event-free survival was 75·4% with the same risk factors except for CMV serostatus. Five-year non-relapse mortality was 13·8% [7·3-22.3]. Only five patients (6·1%) developed grade II-IV acute GVHD and two patients chronic GVHD. These data confirm the excellent outcome of matched related or unrelated HSCT in children with FA.

Epstein-Barr virus (EBV) deletions as biomarkers of response to treatment of chronic active EBV.

Chronic active Epstein-Barr virus (CAEBV) disease is a rare condition characterised by persistent EBV infection in previously healthy individuals. Defective EBV genomes were found in East Asian patients with CAEBV. In the present study, we sequenced 14 blood EBV samples from three UK patients with CAEBV, comparing the results with saliva CAEBV samples and other conditions. We observed EBV deletions in blood, some of which may disrupt viral replication, but not saliva in CAEBV. Deletions were lost overtime after successful treatment. These findings are compatible with CAEBV being associated with the evolution and persistence of EBV+ haematological clones that are lost on successful treatment.

Outcome of Non-hematological Autoimmunity After Hematopoietic Cell Transplantation in Children with Primary Immunodeficiency.

PURPOSE: Knowledge of post-hematopoietic cell transplantation (HCT) non-hematological autoimmune disease (AD) is far from satisfactory. METHOD: This multicenter retrospective study focuses on incidence, risk factors, and outcomes of post-HCT AD in 596 children with primary immunodeficiency (PID) who were transplanted from 2009 to 2018. RESULTS: The indications of HCT were severe combined immunodeficiency (SCID, n = 158, 27%) and non-SCID PID (n = 438, 73%). The median age at HCT was 2.3 years (range, 0.04 to 18.3 years). The 5-year overall survival for the entire cohort was 79% (95% cumulative incidence (CIN), 74-83%). The median follow-up of surviving patients was 4.3 years (0.08 to 14.7 years). The CIN of post-HCT AD was 3% (2-5%) at 1 year post-HCT, 7% (5-11%) at 5 years post-HCT, and 11% (7-17%) at 8 years post-HCT. The median onset of post-HCT AD was 2.2 years (0.12 to 9.6 years). Autoimmune thyroid disorder (n = 19, 62%) was the most common post-HCT AD, followed by neuromuscular disorders (n = 7, 22%) and rheumatological manifestations (n = 5, 16%). All patients but one required treatment for post-HCT AD. After multivariate analysis, age at transplant (p = 0.01) and T cell-depleted graft (p < 0.001) were significant predictors of post-HCT AD. None of the T cell-depleted graft recipients developed post-HCT AD. Patients with a lower CD3+ count at 6 months post-HCT had a significant higher incidence of post-HCT AD compared to disease controls. Graft-versus-host disease, viral infection, and donor chimerism had no association with post-HCT AD. CONCLUSION: Post-HCT AD occurred in 11% at 8 years post-HCT and its occurrence was associated with older age at HCT and unmanipulated graft.

Delaying haematopoietic stem cell transplantation in children with viral respiratory infections reduces transplant-related mortality.

Viral respiratory infections (VRIs) contribute to the morbidity and transplant-related mortality (TRM) after allogeneic haematopoietic stem cell transplantation (HSCT) and strategies to prevent and treat VRIs are warranted. We monitored VRIs before and after transplant in children undergoing allogeneic HSCT with nasopharyngeal aspirates (NPA) and assessed the impact on clinical outcome. Between 2007 and 2017, 585 children underwent 620 allogeneic HSCT procedures. Out of 75 patients with a positive NPA screen (12%), transplant was delayed in 25 cases (33%), while 53 children started conditioning with a VRI. Patients undergoing HSCT with a positive NPA screen had a significantly lower overall survival (54% vs. 79%) and increased TRM (26% vs. 7%) compared to patients with a negative NPA. Patients with a positive NPA who delayed transplant and cleared the virus before conditioning had improved overall survival (90%) and lower TRM (5%). Pre-HSCT positive NPA was the only significant risk factor for progression to a lower respiratory tract infection and was a major risk factor for TRM. Transplant delay, whenever feasible, in case of a positive NPA screen for VRIs can positively impact on survival of children undergoing HSCT.

Treatment dilemmas in asymptomatic children with primary hemophagocytic lymphohistiocytosis.

Asymptomatic carriers (ACs) of pathogenic biallelic mutations in causative genes for primary hemophagocytic lymphohistiocytosis (HLH) are at high risk of developing life-threatening HLH, which requires allogeneic hematopoietic stem cell transplantation (HSCT) to be cured. There are no guidelines on the management of these asymptomatic patients. We analyzed the outcomes of pairs of index cases (ICs) and subsequently diagnosed asymptomatic family members carrying the same genetic defect. We collected data from 22 HSCT centers worldwide. Sixty-four children were evaluable. ICs presented with HLH at a median age of 16 months. Seven of 32 ICs died during first-line therapy, and 2 are alive after chemotherapy only. In all, 23/32 underwent HSCT, and 16 of them are alive. At a median follow-up of 36 months from diagnosis, 18/32 ICs are alive. Median age of ACs at diagnosis was 5 months. Ten of 32 ACs activated HLH while being observed, and all underwent HSCT: 6/10 are alive and in complete remission (CR). 22/32 ACs remained asymptomatic, and 6/22 have received no treatment and are in CR at a median follow-up of 39 months. Sixteen of 22 underwent preemptive HSCT: 15/16 are alive and in CR. Eight-year probability of overall survival (pOS) in ACs who did not have activated HLH was significantly higher than that in ICs (95% vs 45%; P = .02), and pOS in ACs receiving HSCT before disease activation was significantly higher than in ACs receiving HSCT after HLH activation (93% vs 64%; P = .03). Preemptive HSCT in ACs proved to be safe and should be considered.

New graft manipulation strategies improve the outcome of mismatched stem cell transplantation in children with primary immunodeficiencies.

BACKGROUND: Mismatched stem cell transplantation is associated with a high risk of graft loss, graft-versus-host disease (GvHD), and transplant-related mortality. Alternative graft manipulation strategies have been used over the last 11 years to reduce these risks. OBJECTIVE: We investigated the outcome of using different graft manipulation strategies among children with primary immunodeficiencies. METHODS: Between 2006 and 2017, 147 patients with primary immunodeficiencies received 155 mismatched grafts: 30 T-cell receptor (TCR) αß/CD19-depleted grafts, 43 cord blood (CB) grafts (72% with no serotherapy), 17 CD34+ selection with T-cell add-back grafts, and 65 unmanipulated grafts. RESULTS: The estimated 8-year survival of the entire cohort was 79%, transplant-related mortality was 21.7%, and the graft failure rate was 6.7%. Posttransplantation viral reactivation, grade II to IV acute graft-versus-host disease (aGvHD), and chronic graft-versus-host disease (cGvHD) complicated 49.6%, 35%, and 15% of transplantations, respectively. Use of TCRαß/CD19 depletion was associated with a significantly lower incidence of grade II to IV aGvHD (11.5%) and cGvHD (0%), although with a greater incidence of viral reactivation (70%) in comparison with other grafts. T-cell immune reconstitution was robust among CB transplants, although with a high incidence (56.7%) of grade II to IV aGvHD. Stable full donor engraftment was significantly greater at 80% among TCRαß+/CD19+-depleted and CB transplants versus 40% to 60% among the other groups. CONCLUSIONS: Rapidly accessible CB and haploidentical grafts are suitable alternatives for patients with no HLA-matched donor. Cord transplantation without serotherapy and TCRαß+/CD19+-depleted grafts produced comparable survival rates of around 80%, although with a high rate of aGvHD with the former and a high risk of viral reactivation with the latter that need to be addressed.

Brincidofovir is highly efficacious in controlling adenoviremia in pediatric recipients of hematopoietic cell transplant.

Cidofovir is preemptively used for controlling adenoviremia and preventing disseminated viral disease in hematopoietic cell transplant (HCT) recipients but does not lead to resolution of viremia without T-cell immune-reconstitution. The lipid-conjugated prodrug of cidofovir, brincidofovir, has improved oral bioavailability and achieves higher intracellular concentrations of active drug. We present retrospective multicenter data comparing the kinetics of viremia and toxicities following preemptive treatment with and brincidofovir in children and adolescents diagnosed with HCT-related adenoviremia. Forty-one episodes (18 = brincidofovir; 23 = cidofovir) of antiviral therapy were observed in 27 patients. The 2 groups had comparable immune-reconstitution and viral burden. Major (≥2 log-reduction in 2 weeks; n = 13) and minor (≥1 to ≤2 log-reduction in 2 weeks; n = 2) virological responses were observed in 15 (83%) brincidofovir episodes compared to only 2 (9%) major virological responses with cidofovir (P < .0001). Brincidofovir mediated major responses in 9 of 11 cidofovir-unresponsive patients and resulted in complete responses (CR) despite significant lymphopenia (Brincidofovir vs cidofovir; CR = 13 (80%) vs 8 (35%); median lymphocyte count = 320/µl vs 910/µl; P < .05). One patient experienced abdominal cramps and diarrhea necessitating interruption of brincidofovir and none developed nephrotoxicity with brincidofovir. Thus, brincidofovir is well-tolerated and highly efficacious in controlling adenoviremia during the lymphopenic phase of HCT.

T-cell receptor αß+ and CD19+ cell-depleted haploidentical and mismatched hematopoietic stem cell transplantation in primary immune deficiency.

BACKGROUND: Allogeneic hematopoietic stem cell transplantation (HSCT) is used as a therapeutic approach for primary immunodeficiencies (PIDs). The best outcomes have been achieved with HLA-matched donors, but when a matched donor is not available, a haploidentical or mismatched unrelated donor (mMUD) can be useful. Various strategies are used to mitigate the risk of graft-versus-host disease (GvHD) and rejection associated with such transplants. OBJECTIVE: We sought to evaluate the outcomes of haploidentical or mMUD HSCT after depleting GvHD-causing T-cell receptor (TCR) αß CD3+ cells from the graft. METHODS: CD3+TCRαß+/CD19+ depleted grafts were given in conditioned (except 3) children with PIDs. Treosulfan (busulfan in 1 patient), fludarabine, thiotepa, and anti-thymocyte globulin or alemtuzumab conditioning were used in 77% of cases, and all but 4 received GvHD prophylaxis. RESULTS: Twenty-five patients with 12 types of PIDs received 26 HSCTs. Three underwent transplantation for refractory GvHD that developed after the first cord transplantation. At a median follow-up of 20.8 months (range, 5 month-3.3 years), 21 of 25 patients survived and were cured of underlying immunodeficiency. Overall and event-free survival at 3 years were 83.9% and 80.4%, respectively. Cumulative incidence of grade II to IV acute GvHD was 22% ± 8.7%. No case of visceral or chronic GvHD was seen. Cumulative incidences of graft failure, cytomegalovirus, and/or adenoviral infections and transplant-related mortality at 1 year were 4.2% ± 4.1%, 58.8% ± 9.8%, and 16.1% ± 7.4%, respectively. Patients undergoing transplantation with systemic viral infections had poor survival in comparison with those with absent or resolved infections (33.3% vs 100%). CONCLUSION: CD3+TCRαß+ and CD19+ cell-depleted haploidentical or mMUD HSCT is a practical and viable alternative for children with a range of PIDs.

Treosulfan and Fludarabine Conditioning for Hematopoietic Stem Cell Transplantation in Children with Primary Immunodeficiency: UK Experience.

We previously published results for 70 children who received conditioning with treosulfan and cyclophosphamide (n = 30) or fludarabine (n = 40) before undergoing hematopoietic stem cell transplantation (HSCT) for primary immunodeficiency (PID). Toxicity was lower and T cell chimerism was better in the patients receiving fludarabine, but cohort numbers were relatively small and follow-up was short. Here we report outcomes of 160 children who received homogeneous conditioning with treosulfan, fludarabine, and, in most cases, alemtuzumab (n = 124). The median age at transplantation was 1.36 years (range, .09 to 18.25 years). Donors included 73 matched unrelated, 54 1 to 3 antigen-mismatched unrelated, 12 matched sibling, 17 other matched family, and 4 haploidentical donors. Stem cell source was peripheral blood stem cells (PBSCs) in 70, bone marrow in 49, and cord blood in 41. Median duration of follow-up was 4.3 years (range, .8 to 9.4 years). Overall survival was 83%. No patients had veno-occlusive disease. Seventy-four patients (46%) had acute GVHD, but only 14 (9%) greater than grade II. Four patients underwent successful retransplantation for graft loss or poor immune reconstitution. Another patient experienced graft rejection and died. There was no association between T cell chimerism >95% and stem cell source, but a significant association was seen between myeloid chimerism >95% and use of PBSCs without an increased risk of significant GVHD compared with other sources. All 11 patients with severe combined immunodeficiency diagnosed at birth were alive at up to 8.7 years of follow-up. Long-term studies are needed to determine late gonadotoxic effects, and pharmacokinetic studies are needed to identify whether specific targeting is advantageous. The combination of treosulfan, fludarabine, and alemtuzumab is associated with excellent results in HSCT for PID.

Multicenter phase 1/2 application of adenovirus-specific T cells in high-risk pediatric patients after allogeneic stem cell transplantation.

BACKGROUND: Adenovirus (ADV) reactivation can cause significant morbidity and mortality in children after allogeneic stem cell transplantation. Antiviral drugs can control viremia, but viral clearance requires recovery of cell-mediated immunity. METHOD: This study was an open-label phase 1/2 study to investigate the feasibility of generating donor-derived ADV-specific T cells (Cytovir ADV, Cell Medica) and to assess the safety of pre-emptive administration of ADV-specific T cells in high-risk pediatric patients after allogeneic hematopoietic stem cell transplantation (HSCT) to treat adenoviremia. Primary safety endpoints included graft-versus-host disease (GvHD), and secondary endpoints determined antiviral responses and use of antiviral drugs. RESULTS: Between January 2013 and May 2016, 92 donors were enrolled for the production of ADV T cells at three centers in the United Kingdom (UK), and 83 products were generated from 72 mobilized peripheral blood harvests and 20 steady-state whole blood donations. Eight children received Cytovir ADV T cells after standard therapy and all resolved ADV viremia between 15 and 127 days later. ADV-specific T cells were detectable using enzyme-linked immunospot assay (ELISpot) in the peripheral blood of all patients analyzed. Serious adverse events included Grade II GvHD, Astrovirus encephalitis and pancreatitis. CONCLUSION: The study demonstrates the safety and feasibility of pre-emptively manufacturing peptide pulsed ADV-specific cells for high-risk pediatric patients after transplantation and provides early evidence of clinical efficacy.

Cord blood T cells mediate enhanced antitumor effects compared with adult peripheral blood T cells.

Unrelated cord blood transplantation (CBT) without in vivo T-cell depletion is increasingly used to treat high-risk hematologic malignancies. Following T-replete CBT, naïve CB T cells undergo rapid peripheral expansion with memory-effector differentiation. Emerging data suggest that unrelated CBT, particularly in the context of HLA mismatch and a T-replete graft, may reduce leukemic relapse. To study the role of CB T cells in mediating graft-versus-tumor responses and dissect the underlying immune mechanisms for this, we compared the ability of HLA-mismatched CB and adult peripheral blood (PB) T cells to eliminate Epstein-Barr virus (EBV)-driven human B-cell lymphoma in a xenogeneic NOD/SCID/IL2rg(null) mouse model. CB T cells mediated enhanced tumor rejection compared with equal numbers of PB T cells, leading to improved survival in the CB group (P < .0003). Comparison of CB T cells that were autologous vs allogeneic to the lymphoma demonstrated that this antitumor effect was mediated by alloreactive rather than EBV-specific T cells. Analysis of tumor-infiltrating lymphocytes demonstrated that CB T cells mediated this enhanced antitumor effect by rapid infiltration of the tumor with CCR7(+)CD8(+) T cells and prompt induction of cytotoxic CD8(+) and CD4(+) T-helper (Th1) T cells in the tumor microenvironment. In contrast, in the PB group, this antilymphoma effect is impaired because of delayed tumoral infiltration of PB T cells and a relative bias toward suppressive Th2 and T-regulatory cells. Our data suggest that, despite being naturally programmed toward tolerance, reconstituting T cells after unrelated T-replete CBT may provide superior Tc1-Th1 antitumor effects against high-risk hematologic malignancies.

Effect of stem cell source on long-term chimerism and event-free survival in children with primary immunodeficiency disorders after fludarabine and melphalan conditioning regimen.

BACKGROUND: Reduced-intensity conditioning (RIC) regimens are increasingly being used in the transplantation of patients with primary immunodeficiency disorders (PIDs), but there are no large studies looking at long-term lineage-specific chimerism. OBJECTIVES: We sought to analyze long-term chimerism and event-free survival in children undergoing transplantation for PIDs using RIC with fludarabine and melphalan (Flu/Melph) and to study the effect of donor type and stem cell source. METHODS: One hundred forty-two children underwent transplantation with RIC by using Flu/Melph and for PIDs by using bone marrow (n = 93) or peripheral blood stem cells (PBSCs; n = 49). Donors were matched unrelated donors (n = 72), mismatched unrelated donors (n = 37), matched sibling donors (n = 14), matched family donors (n = 12), and mismatched family donors (n = 7). RESULTS: Overall survival at a median follow-up of 7.5 years was 78%, irrespective of stem cell source or donor type. When bone marrow was used as the stem cell source, 26% of patients ended up with very low levels of donor chimerism (<10% donor), especially in the myeloid lineage. Event-free survival in this group was significantly lower compared with that in the rest of the group (25% vs 70%, P < .001). With the use of PBSCs, more than 90% of patients achieved complete donor chimerism or high-level mixed chimerism (>50% donor chimerism) in all lineages. CONCLUSIONS: On the basis of our experience, we would suggest that PBSCs should be the stem cell source of choice in children with PIDs undergoing transplantation with Flu/Melph RIC from a matched donor source. This is most likely to ensure sustained high-level donor chimerism.

Adoptive immunotherapy for primary immunodeficiency disorders with virus-specific T lymphocytes.

BACKGROUND: Viral infections are a leading fatal complication for patients with primary immunodeficiencies (PIDs) who require hematopoietic stem cell transplantation (HSCT). Use of virus-specific T lymphocytes (VSTs) has been successful for the treatment and prevention of viral infections after HSCT for malignant and nonmalignant conditions. Here we describe the clinical use of VSTs in patients with PIDs at 4 centers. OBJECTIVE: We sought to evaluate the safety and efficacy of VSTs for treatment of viral infections in patients with PIDs. METHODS: Patients with PIDs who have received VST therapy on previous or current protocols were reviewed in aggregate. Clinical information, including transplantation details, viral infections, and use of antiviral and immunosuppressive pharmacotherapy, were evaluated. Data regarding VST production, infusions, and adverse reactions were compared. RESULTS: Thirty-six patients with 12 classes of PID diagnoses received 37 VST products before or after HSCT. Twenty-six (72%) patients had received a diagnosis of infection with cytomegalovirus, EBV, adenovirus, BK virus, and/or human herpesvirus 6. Two patients were treated before HSCT because of EBV-associated lymphoproliferative disease. Partial or complete responses against targeted viruses occurred in 81% of patients overall. Time to response varied from 2 weeks to 3 months (median, 28 days). Overall survival at 6 months after therapy was 80%. Four patients had graft-versus-host disease in the 45 days after VST infusion, which in most cases was therapy responsive. CONCLUSION: VSTs derived from either stem cell donors or third-party donors are likely safe and effective for the treatment of viral infections in patients with PIDs.