Final outcomes from a phase 2 trial of posoleucel in allogeneic hematopoietic cell transplant recipients.

ABSTRACT: Allogeneic hematopoietic cell transplantation (allo-HCT) recipients are susceptible to viral infections. We conducted a phase 2 trial evaluating the safety and rate of clinically significant infections (CSIs; viremia requiring treatment or end-organ disease) after infusion of posoleucel, a partially HLA-matched, allogeneic, off-the-shelf, multivirus-specific T-cell investigational product for preventing CSIs with adenovirus, BK virus, cytomegalovirus, Epstein-Barr virus, human herpesvirus-6, or JC virus. This open-label trial enrolled allo-HCT recipients at high risk based on receiving grafts from umbilical cord blood, haploidentical, mismatched, or matched unrelated donors; post-HCT lymphocytes of <180/mm3; or use of T-cell depletion. Posoleucel dosing was initiated within 15 to 49 days of allo-HCT and subsequently every 14 days for up to 7 doses. The primary end point was the number of CSIs due to the 6 target viruses by week 14. Of the 26 patients enrolled, only 3 (12%) had a CSI by week 14, each with a single target virus. In vivo expansion of functional virus-specific T cells detected via interferon-γ enzyme-linked immunosorbent spot assay was associated with viral control. Persistence of posoleucel-derived T-cell clones for up to 14 weeks after the last infusion was confirmed by T-cell-receptor deep sequencing. Five patients (19%) had acute graft-versus-host disease grade 2 to 4. No patient experienced cytokine release syndrome. All 6 deaths were due to relapse or disease progression. allo-HCT recipients at high risk who received posoleucel had low rates of CSIs from 6 targeted viruses. Repeat posoleucel dosing was generally safe and well tolerated and associated with functional immune reconstitution. This trial was registered at www.ClinicalTrials.gov as #NCT04693637.

Phenotypic and functional characterization of posoleucel, a multivirus-specific T cell therapy for the treatment and prevention of viral infections in immunocompromised patients.

BACKGROUND: Deficits in T cell immunity translate into increased risk of severe viral infection in recipients of solid organ and hematopoietic cell transplants. Thus, therapeutic strategies that employ the adoptive transfer of virus-specific T cells are being clinically investigated to treat and prevent viral diseases in these highly immunocompromised patients. Posoleucel is an off-the-shelf multivirus-specific T cell investigational product for the treatment and prevention of infections due to adenovirus, BK virus, cytomegalovirus, Epstein-Barr virus, human herpesvirus 6 or JC virus. METHODS: Herein we perform extensive characterization of the phenotype and functional profile of posoleucel to illustrate the cellular properties that may contribute to its in vivo activity. RESULTS AND CONCLUSIONS: Our results demonstrate that posoleucel is enriched for central and effector memory CD4+ and CD8+ T cells with specificity for posoleucel target viruses and expressing a broad repertoire of T cell receptors. Antigen-driven upregulation of cell-surface molecules and production of cytokine and effector molecules indicative of proliferation, co-stimulation, and cytolytic potential demonstrate the specificity of posoleucel and its potential to mount a broad, polyfunctional, and effective Th1-polarized antiviral response upon viral exposure. We also show the low risk for off-target and nonspecific effects as evidenced by the enrichment of posoleucel in memory T cells, low frequency of naive T cells, and lack of demonstrated alloreactivity in vitro. The efficacy of posoleucel is being explored in four placebo-controlled clinical trials in transplant recipients to treat and prevent viral infections (NCT05179057, NCT05305040, NCT04390113, NCT04605484).

The remission status of AML patients after allo-HCT is associated with a distinct single-cell bone marrow T-cell signature.

ABSTRACT: Acute myeloid leukemia (AML) is a hematologic malignancy for which allogeneic hematopoietic cell transplantation (allo-HCT) often remains the only curative therapeutic approach. However, incapability of T cells to recognize and eliminate residual leukemia stem cells might lead to an insufficient graft-versus-leukemia (GVL) effect and relapse. Here, we performed single-cell RNA-sequencing (scRNA-seq) on bone marrow (BM) T lymphocytes and CD34+ cells of 6 patients with AML 100 days after allo-HCT to identify T-cell signatures associated with either imminent relapse (REL) or durable complete remission (CR). We observed a higher frequency of cytotoxic CD8+ effector and gamma delta (γδ) T cells in CR vs REL samples. Pseudotime and gene regulatory network analyses revealed that CR CD8+ T cells were more advanced in maturation and had a stronger cytotoxicity signature, whereas REL samples were characterized by inflammatory tumor necrosis factor/NF-κB signaling and an immunosuppressive milieu. We identified ADGRG1/GPR56 as a surface marker enriched in CR CD8+ T cells and confirmed in a CD33-directed chimeric antigen receptor T cell/AML coculture model that GPR56 becomes upregulated on T cells upon antigen encounter and elimination of AML cells. We show that GPR56 continuously increases at the protein level on CD8+ T cells after allo-HCT and confirm faster interferon gamma (IFN-γ) secretion upon re-exposure to matched, but not unmatched, recipient AML cells in the GPR56+ vs GPR56- CD8+ T-cell fraction. Together, our data provide a single-cell reference map of BM-derived T cells after allo-HCT and propose GPR56 expression dynamics as a surrogate for antigen encounter after allo-HCT.

T cell immune profiling of respiratory syncytial virus for the development of a targeted immunotherapy.

Respiratory syncytial virus (RSV)-associated viral infections are a major public health problem affecting the immunologically naïve/compromised populations. Given the RSV-associated morbidity and the limited treatment options, we sought to characterize the cellular immune response to RSV to develop a targeted T cell therapy for off-the-shelf administration to immunocompromised individuals. Here we report on the immunological profiling, as well as manufacturing, characterization and antiviral properties of these RSV-targeted T cells. A randomized, phase 1/2 clinical trial evaluating their safety and activity in haematopoietic stem cell transplant recipients as an off-the-shelf multi-respiratory virus-directed product is currently underway (NCT04933968, https://clinicaltrials.gov).

Allogeneic, off-the-shelf, SARS-CoV-2-specific T cells (ALVR109) for the treatment of COVID-19 in high-risk patients.

Defects in T-cell immunity to SARS-CoV-2 have been linked to an increased risk of severe COVID-19 (even after vaccination), persistent viral shedding and the emergence of more virulent viral variants. To address this T-cell deficit, we sought to prepare and cryopreserve banks of virus-specific T cells, which would be available as a partially HLA-matched, off-the-shelf product for immediate therapeutic use. By interrogating the peripheral blood of healthy convalescent donors, we identified immunodominant and protective T-cell target antigens, and generated and characterized polyclonal virus-specific T-cell lines with activity against multiple clinically important SARS-CoV-2 variants (including 'delta' and 'omicron'). The feasibility of making and safely utilizing such virus-specific T cells clinically was assessed by administering partially HLA-matched, third-party, cryopreserved SARS-CoV-2-specific T cells (ALVR109) in combination with other antiviral agents to four individuals who were hospitalized with COVID-19. This study establishes the feasibility of preparing and delivering off-the-shelf, SARS-CoV-2-directed, virus-specific T cells to patients with COVID-19 and supports the clinical use of these products outside of the profoundly immune compromised setting (ClinicalTrials.gov number, NCT04401410).

Assessment of the cytolytic potential of a multivirus-targeted T cell therapy using a vital dye-based, flow cytometric assay.

Reliable and sensitive characterization assays are important determinants of the successful clinical translation of immunotherapies. For the assessment of cytolytic potential, the chromium 51 (51Cr) release assay has long been considered the gold standard for testing effector cells. However, attaining the approvals to access and use radioactive isotopes is becoming increasingly complex, while technical aspects [i.e. sensitivity, short (4-6 hours) assay duration] may lead to suboptimal performance. This has been the case with our ex vivo expanded, polyclonal (CD4+ and CD8+) multivirus-specific T cell (multiVST) lines, which recognize 5 difficult-to-treat viruses [Adenovirus (AdV), BK virus (BKV), cytomegalovirus (CMV), Epstein Barr virus (EBV), and human herpes virus 6 (HHV6)] and when administered to allogeneic hematopoietic stem cell (HCT) or solid organ transplant (SOT) recipients have been associated with clinical benefit. However, despite mediating potent antiviral effects in vivo, capturing in vitro cytotoxic potential has proven difficult in a traditional 51Cr release assay. Now, in addition to cytotoxicity surrogates, including CD107a and Granzyme B, we report on an alternative, vital dye -based, flow cytometric platform in which superior sensitivity and prolonged effector:target co-culture duration enabled the reliable detection of both CD4- and CD8-mediated in vitro cytolytic activity against viral targets without non-specific effects.

Multi-antigen-targeted T-cell therapy to treat patients with relapsed/refractory breast cancer.

Purpose: Adoptively transferred, ex vivo expanded multi-antigen-targeted T cells (multiTAA-T) represent a new, potentially effective, and nontoxic therapeutic approach for patients with breast cancer (BC). In this first-in-human trial, we investigated the safety and clinical effects of administering multiTAA T cells targeting the tumor-expressed antigens, Survivin, NY-ESO-1, MAGE-A4, SSX2, and PRAME, to patients with relapsed/refractory/metastatic BC. Materials and methods: MultiTAA T-cell products were generated from the peripheral blood of heavily pre-treated patients with metastatic or locally recurrent unresectable BC of all subtypes and infused at a fixed dose level of 2 × 107/m2. Patients received two infusions of cells 4 weeks apart and safety and clinical activity were determined. Cells were administered in an outpatient setting and without prior lymphodepleting chemotherapy. Results: All patients had estrogen receptor/progesterone receptor positive BC, with one patient also having human epidermal growth factor receptor 2-positive. There were no treatment-related toxicities and the infusions were well tolerated. Of the 10 heavily pre-treated patients enrolled and infused with multiTAA T cells, nine had disease progression while one patient with 10 lines of prior therapies experienced prolonged (5 months) disease stabilization that was associated with the in vivo expansion and persistence of T cells directed against the targeted antigens. Furthermore, antigen spreading and the endogenous activation of T cells directed against a spectrum of non-targeted tumor antigens were observed in 7/10 patients post-multiTAA infusion. Conclusion: MultiTAA T cells were well tolerated and induced disease stabilization in a patient with refractory BC. This was associated with in vivo T-cell expansion, persistence, and antigen spreading. Future directions of this approach may include additional strategies to enhance the therapeutic benefit of multiTAA T cells in patients with BC.

Donor-derived multiple leukemia antigen-specific T-cell therapy to prevent relapse after transplant in patients with ALL.

Hematopoietic stem cell transplant (HSCT) is a curative option for patients with high-risk acute lymphoblastic leukemia (ALL), but relapse remains a major cause of treatment failure. To prevent disease relapse, we prepared and infused donor-derived multiple leukemia antigen-specific T cells (mLSTs) targeting PRAME, WT1, and survivin, which are leukemia-associated antigens frequently expressed in B- and T-ALL. Our goal was to maximize the graft-versus-leukemia effect while minimizing the risk of graft-versus-host disease (GVHD). We administered mLSTs (dose range, 0.5 × 107 to 2 × 107 cells per square meter) to 11 patients with ALL (8 pediatric, 3 adult), and observed no dose-limiting toxicity, acute GVHD or cytokine release syndrome. Six of 8 evaluable patients remained in long-term complete remission (median: 46.5 months; range, 9-51). In these individuals we detected an increased frequency of tumor-reactive T cells shortly after infusion, with activity against both targeted and nontargeted, known tumor-associated antigens, indicative of in vivo antigen spreading. By contrast, this in vivo amplification was absent in the 2 patients who experienced relapse. In summary, infusion of donor-derived mLSTs after allogeneic HSCT is feasible and safe and may contribute to disease control, as evidenced by in vivo tumor-directed T-cell expansion. Thus, this approach represents a promising strategy for preventing relapse in patients with ALL.

T-Cell Therapy for Lymphoma Using Nonengineered Multiantigen-Targeted T Cells Is Safe and Produces Durable Clinical Effects.

PURPOSE: Patients with relapsed lymphomas often fail salvage therapies including high-dose chemotherapy and mono-antigen-specific T-cell therapies, highlighting the need for nontoxic, novel treatments. To that end, we clinically tested an autologous T-cell product that targets multiple tumor-associated antigens (TAAs) expressed by lymphomas with the intent of treating disease and preventing immune escape. PATIENTS AND METHODS: We expanded polyclonal T cells reactive to five TAAs: PRAME, SSX2, MAGEA4, SURVIVIN, and NY-ESO-1. Products were administered to 32 patients with Hodgkin lymphomas (n = 14) or non-Hodgkin lymphomas (n = 18) in a two-part phase I clinical trial, where the objective of the first phase was to establish the safety of targeting all five TAAs (fixed dose, 0.5 × 107 cells/m2) simultaneously and the second stage was to establish the maximum tolerated dose. Patients had received a median of three prior lines of therapy and either were at high risk for relapse (adjuvant arm, n = 17) or had chemorefractory disease (n = 15) at enrollment. RESULTS: Infusions were safe with no dose-limiting toxicities observed in either the antigen- or dose-escalation phases. Although the maximum tolerated dose was not reached, the maximum tested dose at which efficacy was observed (two infusions, 2 × 107 cells/m2) was determined as the recommended phase II dose. Of the patients with chemorefractory lymphomas, two (of seven) with Hodgkin lymphomas and four (of eight) with non-Hodgkin lymphomas achieved durable complete remissions (> 3 years). CONCLUSION: T cells targeting five TAAs and administered at doses of up to two infusions of 2 × 107 cells/m2 are well-tolerated by patients with lymphoma both as adjuvant and to treat chemorefractory lymphoma. Preliminary indicators of antilymphoma activity were seen in the chemorefractory cohort across both antigen- and dose-escalation phases.

Clinical effects of administering leukemia-specific donor T cells to patients with AML/MDS after allogeneic transplant.

Relapse after allogeneic hematopoietic stem cell transplantation (HCT) is the leading cause of death in patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS). Infusion of unselected donor lymphocytes (DLIs) enhances the graft-versus-leukemia (GVL) effect. However, because the infused lymphocytes are not selected for leukemia specificity, the GVL effect is often accompanied by life-threatening graft-versus-host disease (GVHD), related to the concurrent transfer of alloreactive lymphocytes. Thus, to minimize GVHD and maximize GVL, we selectively activated and expanded stem cell donor-derived T cells reactive to multiple antigens expressed by AML/MDS cells (PRAME, WT1, Survivin, and NY-ESO-1). Products that demonstrated leukemia antigen specificity were generated from 29 HCT donors. In contrast to DLIs, leukemia-specific T cells (mLSTs) selectively recognized and killed leukemia antigen-pulsed cells, with no activity against recipient's normal cells in vitro. We administered escalating doses of mLSTs (0.5 to 10 × 107 cells per square meter) to 25 trial enrollees, 17 with high risk of relapse and 8 with relapsed disease. Infusions were well tolerated with no grade >2 acute or extensive chronic GVHD seen. We observed antileukemia effects in vivo that translated into not-yet-reached median leukemia-free and overall survival at 1.9 years of follow-up and objective responses in the active disease cohort (1 complete response and 1 partial response). In summary, mLSTs are safe and promising for the prevention and treatment of AML/MDS after HCT. This trial is registered at www.clinicaltrials.com as #NCT02494167.

Neuro-inflammatory Sequelae of Minimal Trauma in the Non-traumatized Human Brain: A Microdialysis Study.

Cytokine measurement directly from the brain parenchyma by means of microdialysis has documented the activation of certain procedures in vivo, after brain trauma in humans. However, the intercalation of the micro-catheter insertion with the phenomena triggered by the head trauma renders the assessment of the findings problematic. The present study attempts to elucidate the pure effect of minimal trauma, represented by the insertion of the micro-catheter, on the non-traumatized human brain. Microdialysis catheters were implanted in 12 patients with drug-resistant epilepsy, and subjected to invasive electroencephalography with intracranial electrodes. Samples were collected during the first 5 days of monitoring. The dialysate was analyzed using bead flow cytometry, and the concentrations of interleukin (IL)-1, IL-6, IL-8, IL-10, IL-12, and tumor necrosis factor-α (TNF-α) were measured. The levels of IL-1 and IL-8 were found to be raised until 48 h post-implantation, and thereafter they reached a plateau of presumably baseline values. The temporal profile of the IL-6 variation was different, with the increase being much more prolonged, as its concentration had not returned to baseline levels at the fifth day post-insertion. TNF-α was found to be significantly raised only 2 h after implantation. IL-10 and IL-12 did not have any significant response to micro-trauma. These findings imply that the reaction of the neuro-inflammatory mechanisms of the brain exist even after minimal trauma, and is unexpectedly intense for IL-6. Questions may arise regarding the objectivity of findings attributed by some studies to inflammatory perturbation after head injury.

The safety and clinical effects of administering a multiantigen-targeted T cell therapy to patients with multiple myeloma.

Multiple myeloma (MM) is an almost always incurable malignancy of plasma cells. Despite the advent of new therapies, most patients eventually relapse or become treatment-refractory. Consequently, therapies with nonoverlapping mechanisms of action that are nontoxic and provide long-term benefit to patients with MM are greatly needed. To this end, we clinically tested an autologous multitumor-associated antigen (mTAA)-specific T cell product for the treatment of patients with high-risk, relapsed or refractory MM. In this study, we expanded polyclonal T cells from 23 patients with MM. T cells whose native T cell receptors were reactive toward five myeloma-expressed target TAAs (PRAME, SSX2, MAGEA4, Survivin, and NY-ESO-1) were enriched ex vivo. To date, we have administered escalating doses of these nonengineered mTAA-specific T cells (0.5 × 107 to 2 × 107 cells/m2) to 21 patients with MM, 9 of whom were at high risk of relapse after a median of 3 lines of prior therapy and 12 with active, relapsed or refractory disease after a median of 3.5 prior lines. The cells were well tolerated, with only two transient, grade III infusion-related adverse events. Furthermore, patients with active relapsed or refractory myeloma enjoyed a longer than expected progression-free survival and responders included three patients who achieved objective responses concomitant with detection of functional TAA-reactive T cell clonotypes derived from the infused mTAA product.

Toward Functional Immune Monitoring in Allogeneic Stem Cell Transplant Recipients.

Serious viral infections, due to delayed immune reconstitution, are a leading cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT). Thus, many transplant centers prospectively track cellular immune recovery by evaluating absolute cell numbers and the phenotypic profile of reconstituting T cell subsets to identify individuals who are at highest risk of infection. Conventional assessments, however, fail to measure either the antigen specificity or functional capacity of reconstituting cells-both factors that correlate with endogenous antiviral protection. In this pilot study, we sought to address this limitation by prospectively investigating the tempo of endogenous immune reconstitution in a cohort of 23 pediatric HSCT patients using both quantitative (flow cytometry) and qualitative (IFNγ ELISpot) measures, which we correlated with either the presence or absence of infections associated with cytomegalovirus, adenovirus, Epstein-Barr virus, BK virus, human herpes virus 6, respiratory syncytial virus, parainfluenza, influenza, and human metapneumovirus. We present data spanning 12 months post-transplant demonstrating the influence of conditioning on immune recovery and highlighting the differential impact of active viral replication on the quantity and quality of reconstituting cells. Judicious use of standard (phenotypic) and novel (functional) monitoring strategies can help guide the clinical care and personalized management of allogenic HSCT recipients with infections.

Immune cell response to strenuous resistive breathing: comparison with whole body exercise and the effects of antioxidants.

Background/hypothesis: Whole body exercise (WBE) changes lymphocyte subset percentages in peripheral blood. Resistive breathing, a hallmark of diseases of airway obstruction, is a form of exercise for the inspiratory muscles. Strenuous muscle contractions induce oxidative stress that may mediate immune alterations following exercise. We hypothesized that inspiratory resistive breathing (IRB) alters peripheral blood lymphocyte subsets and that oxidative stress mediates lymphocyte subpopulation alterations following both WBE and IRB. Patients and methods: Six healthy nonathletes performed two WBE and two IRB sessions for 45 minutes at 70% of VO2 maximum and 70% of maximum inspiratory pressure (Pimax), respectively, before and after the administration of antioxidants (vitamins E, A, and C for 75 days, allopurinol for 30 days, and N-acetylcysteine for 3 days). Blood was drawn at baseline, at the end of each session, and 2 hours into recovery. Lymphocyte subsets were determined by flow cytometry. Results: Before antioxidant supplementation at both WBE end and IRB end, the natural killer cell percentage increased, the T helper cell (CD3+ CD4+) percentage was reduced, and the CD4/CD8 ratio was depressed, a response which was abolished by antioxidants only after IRB. Furthermore, at IRB end, antioxidants promoted CD8+ CD38+ and blunted cytotoxic T-cell percentage increase. CD8+ CD45RA+ cell percentage changes were blunted after antioxidant supplementation in both WBE and IRB. Conclusion: We conclude that IRB produces (as WBE) changes in peripheral blood lymphocyte subsets and that oxidative stress is a major stimulus predominantly for IRB-induced lymphocyte subset alterations.

Ex Vivo Induction of Multiple Myeloma-specific Immune Responses by Monocyte-derived Dendritic Cells Following Stimulation by Whole-tumor Antigen of Autologous Myeloma Cells.

The introduction of novel agents has significantly expanded treatment options for multiple myeloma (MM), albeit long-term disease control cannot be achieved in the majority of patients. Vaccination with MM antigen-loaded dendritic cells (DCs) represents an alternative strategy that is currently being explored. The aim of this study was to assess the immunogenic potential of ex vivo-generated monocyte-derived DCs (moDCs), following stimulation with the whole-antigen array of autologous myeloma cells (AMC). MoDCs were loaded with antigens of myeloma cells by 2 different methods: phagocytosis of apoptotic bodies from γ-irradiated AMC, or transfection with AMC total RNA by square-wave electroporation. Twenty patients with MM were enrolled in the study. Following stimulation and maturation, moDCs were tested for their capacity to induce T-helper 1 and cytotoxic T lymphocyte responses in vitro. Both strategies were effective in the induction of myeloma-specific cytotoxic T lymphocyte and T-helper 1 cells, as demonstrated by cytotoxicity and ELISpot assays. On the whole, T-cell responses were observed in 18 cases by either method of DC pulsing. We conclude that both whole-tumor antigen approaches are efficient in priming autologous antimyeloma T-cell responses and warrant further study aiming at the development of individualized DC vaccines for MM patients.