Antiviral cellular therapy for enhancing T-cell reconstitution before or after hematopoietic stem cell transplantation (ACES): a two-arm, open label phase II interventional trial of pediatric patients with risk factor assessment.

Viral infections remain a major risk in immunocompromised pediatric patients, and virus-specific T cell (VST) therapy has been successful for treatment of refractory viral infections in prior studies. We performed a phase II multicenter study (NCT03475212) for the treatment of pediatric patients with inborn errors of immunity and/or post allogeneic hematopoietic stem cell transplant with refractory viral infections using partially-HLA matched VSTs targeting cytomegalovirus, Epstein-Barr virus, or adenovirus. Primary endpoints were feasibility, safety, and clinical responses (>1 log reduction in viremia at 28 days). Secondary endpoints were reconstitution of antiviral immunity and persistence of the infused VSTs. Suitable VST products were identified for 75 of 77 clinical queries. Clinical responses were achieved in 29 of 47 (62%) of patients post-HSCT including 73% of patients evaluable at 1-month post-infusion, meeting the primary efficacy endpoint (>52%). Secondary graft rejection occurred in one child following VST infusion as described in a companion article. Corticosteroids, graft-versus-host disease, transplant-associated thrombotic microangiopathy, and eculizumab treatment correlated with poor response, while uptrending absolute lymphocyte and CD8 T cell counts correlated with good response. This study highlights key clinical factors that impact response to VSTs and demonstrates the feasibility and efficacy of this therapy in pediatric HSCT.

Secondary bone marrow graft loss after third-party virus-specific T cell infusion: Case report of a rare complication.

Virus-specific T cells (VST) from partially-HLA matched donors have been effective for treatment of refractory viral infections in immunocompromised patients in prior studies with a good safety profile, but rare adverse events have been described. Here we describe a unique and severe adverse event of VST therapy in an infant with severe combined immunodeficiency, who receives, as part of a clinical trial (NCT03475212), third party VSTs for treating cytomegalovirus viremia following bone marrow transplantation. At one-month post-VST infusion, rejection of graft and reversal of chimerism is observed, as is an expansion of T cells exclusively from the VST donor. Single-cell gene expression and T cell receptor profiling demonstrate a narrow repertoire of predominantly activated CD4+ T cells in the recipient at the time of rejection, with the repertoire overlapping more with that of peripheral blood from VST donor than the infused VST product. This case thus demonstrates a rare but serious side effect of VST therapy.

The Effects of Human Immunodeficiency Virus Type 1 (HIV-1) Antigen-Expanded Specific T-Cell Therapy and Vorinostat on Persistent HIV-1 Infection in People With HIV on Antiretroviral Therapy.

BACKGROUND: The histone deacetylase inhibitor vorinostat (VOR) can reverse human immunodeficiency virus type 1 (HIV-1) latency in vivo and allow T cells to clear infected cells in vitro. HIV-specific T cells (HXTCs) can be expanded ex vivo and have been safely administered to people with HIV (PWH) on antiretroviral therapy. METHODS: Six PWH received infusions of 2 × 107 HXTCs/m² with VOR 400 mg, and 3 PWH received infusions of 10 × 107 HXTCs/m² with VOR. The frequency of persistent HIV by multiple assays including quantitative viral outgrowth assay (QVOA) of resting CD4+ T cells was measured before and after study therapy. RESULTS: VOR and HXTCs were safe, and biomarkers of serial VOR effect were detected, but enhanced antiviral activity in circulating cells was not evident. After 2 × 107 HXTCs/m² with VOR, 1 of 6 PWH exhibited a decrease in QVOA, and all 3 PWH exhibited such declines after 10 × 107 HXTCs/m² and VOR. However, most declines did not exceed the 6-fold threshold needed to definitively attribute decline to the study intervention. CONCLUSIONS: These modest effects provide support for the strategy of HIV latency reversal and reservoir clearance, but more effective interventions are needed to yield the profound depletion of persistent HIV likely to yield clinical benefit. Clinical Trials Registration. NCT03212989.

Durable immunity to EBV after rituximab and third-party LMP-specific T cells: a Children's Oncology Group study.

ABSTRACT: Posttransplant lymphoproliferative disease (PTLD) in pediatric solid organ transplant (SOT) recipients is characterized by uncontrolled proliferation of Epstein-Barr virus-infected (EBV+) B cells due to decreased immune function. This study evaluated the feasibility, safety, clinical and immunobiological outcomes in pediatric SOT recipients with PTLD treated with rituximab and third-party latent membrane protein-specific T cells (LMP-TCs). Newly diagnosed (ND) patients without complete response to rituximab and all patients with relapsed/refractory (R/R) disease received LMP-TCs. Suitable LMP-TC products were available for all eligible subjects. Thirteen of 15 patients who received LMP-TCs were treated within the prescribed 14-day time frame. LMP-TC therapy was generally well tolerated. Notable adverse events included 3 episodes of rejection in cardiac transplant recipients during LMP-TC therapy attributed to subtherapeutic immunosuppression and 1 episode of grade 3 cytokine release syndrome. Clinical outcomes were associated with disease severity. Overall response rate (ORR) after LMP-TC cycle 1 was 70% (7/10) for the ND cohort and 20% (1/5) for the R/R cohort. For all cohorts combined, the best ORR for LMP-TC cycles 1 and 2 was 53% and the 2-year overall survival was 70.7%. vßT-cell receptor sequencing showed persistence of adoptively transferred third-party LMP-TCs for up to 8 months in the ND cohort. This study establishes the feasibility of administering novel T-cell therapies in a cooperative group clinical trial and demonstrates the potential for positive outcomes without chemotherapy for ND patients with PTLD. This trial was registered at www.clinicaltrials.gov as #NCT02900976 and at the Children's Oncology Group as ANHL1522.

Outcomes following posttransplant virus-specific T-cell therapy in patients with sickle cell disease.

Hematopoietic stem cell transplantation (HSCT) is being increasingly used as a curative approach for sickle cell disease (SCD). With the risk of graft-versus-host disease (GVHD), especially in the human leukocyte antigen-mismatched donors, intense immunosuppression is required leading to an increased risk of viral infection. Post-HSCT, adoptive transfer of virus-specific T-cell (VST) therapies have not been well-studied in patients with SCD. Here, we report the outcomes of patients with SCD at a single-center who received VSTs after transplant to prevent or treat viral infections. Thirteen patients who received HSCT from human leukocyte antigen-matched (n = 9) or -mismatched (n = 4) donors for SCD were treated with a total of 15 VST products for the treatment or prophylaxis of multiple viruses (cytomegalovirus, Epstein-Barr virus, adenovirus, BK virus, human herpes virus 6 +/- human parainfluenza virus 3). Of the patients evaluated, 46.2% (n = 6)) received VSTs as treatment for viral infection. Eighty percent of patients with active viremia (n = 4/5) achieved remission of at least 1 target virus. Seven additional patients (53.8%) received VSTs prophylactically and 6 of 7 (85.7%) remained virus-free after infusion. No immediate infusion-related toxicities occurred, and severe de novo acute GVHD occurred in only 2 (15.4%) patients. Given the good safety profile, high-rate of clinical responses and sustained remissions when administered with standard antiviral treatments, the routine use of VSTs after HSCT as prophylaxis or treatment may improve the overall safety of transplant for patients with SCD.

Outcome of donor-derived TAA-T cell therapy in patients with high-risk or relapsed acute leukemia post allogeneic BMT.

Patients with hematologic malignancies relapsing after allogeneic blood or marrow transplantation (BMT) have limited response to conventional salvage therapies, with an expected 1-year overall survival (OS) of <20%. We evaluated the safety and clinical outcomes following administration of a novel T-cell therapeutic targeting 3 tumor-associated antigens (TAA-T) in patients with acute leukemia who relapsed or were at high risk of relapse after allogeneic BMT. Lymphocytes obtained from the BMT donor were manufactured to target TAAs WT1, PRAME, and survivin, which are over-expressed and immunogenic in most hematologic malignancies. Patients received TAA-T infusions at doses of 0.5 to 4 × 107/m2. Twenty-three BMT recipients with relapsed/refractory (n = 11) and/or high-risk (n = 12) acute myeloid leukemia (n = 20) and acute lymphoblastic leukemia (n = 3) were infused posttransplant. No patient developed cytokine-release syndrome or neurotoxicity, and only 1 patient developed grade 3 graft-versus-host disease. Of the patients who relapsed post-BMT and received bridging therapy, the majority (n = 9/11) achieved complete hematologic remission before receiving TAA-T. Relapsed patients exhibited a 1-year OS of 36% and 1-year leukemia-free survival of 27.3% post-TAA-T. The poorest prognosis patients (relapsed <6 months after transplant) exhibited a 1-year OS of 42.8% postrelapse (n = 7). Median survival was not reached for high-risk patients who received preemptive TAA-T posttransplant (n = 12). Although as a phase 1 study, concomitant antileukemic therapy was allowed, TAA-T were safe and well tolerated, and sustained remissions in high-risk and relapsed patients were observed. Moreover, adoptively transferred TAA-T detected by T-cell receptor V-ß sequencing persisted up to at least 1 year postinfusion. This trial was registered at clinicaltrials.gov as #NCT02203903.

Processing laboratory considerations for multi-center cellular therapy clinical trials: a report from the Consortium for Pediatric Cellular Immunotherapy.

``Cellular therapies first emerged as specialized therapies only available at a few "boutique" centers worldwide. To ensure broad access to these investigational therapies-regardless of geography, demographics and other factors-more and more academic clinical trials are becoming multi-center. Such trials are typically performed with a centralized manufacturing facility receiving the starting material and shipping the final product, either fresh or cryopreserved, to the patient's institution for infusion. As these academic multi-center trials increase in number, it is critical to have procedures and training programs in place to allow these sites that are remote from the production facility to successfully participate in these trials and satisfy regulatory compliance and patient safety best practices. Based on the collective experience of the Consortium for Pediatric Cellular Immunotherapy, the authors summarize the challenges encountered by institutions in shipping and receiving the starting material and final product as well as preparing the final product for infusion. The authors also discuss best practices implemented by each of the consortia institutions to overcome these challenges.

Critical testing and parameters for consideration when manufacturing and evaluating tumor-associated antigen-specific T cells.

The past year has seen remarkable translation of cellular and gene therapies, with U.S. Food and Drug Administration (FDA) approval of three chimeric antigen receptor (CAR) T-cell products, multiple gene therapy products, and the initiation of countless other pivotal clinical trials. What makes these new drugs most remarkable is their path to commercialization: they have unique requirements compared with traditional pharmaceutical drugs and require different potency assays, critical quality attributes and parameters, pharmacological and toxicological data, and in vivo efficacy testing. What's more, each biologic requires its own unique set of tests and parameters. Here we describe the unique tests associated with ex vivo-expanded tumor-associated antigen T cells (TAA-T). These tests include functional assays to determine potency, specificity, and identity; tests for pathogenic contaminants, such as bacteria and fungus as well as other contaminants such as Mycoplasma and endotoxin; tests for product characterization, tests to evaluate T-cell persistence and product efficacy; and finally, recommendations for critical quality attributes and parameters associated with the expansion of TAA-Ts.