A randomized phase II clinical trial of enzalutamide in combination with the therapeutic cancer vaccine, PSA tricom, in metastatic, castration resistant prostate cancer.

2013 ◽  
Vol 31 (15_suppl) ◽  
pp. TPS5104-TPS5104
Author(s):  
Nishith K. Singh ◽  
Joseph W. Kim ◽  
Christopher Ryan Heery ◽  
William L. Dahut ◽  
Anna Couvillon ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Clinical Trial ◽  
T Cells ◽  
T Cell ◽  
Cancer Vaccine ◽  
Phase Iii ◽  
Cytotoxic T Cell ◽  
Phase 2 ◽  
Therapeutic Cancer Vaccine ◽  
Randomized Phase 2

TPS5104 Background: There is a strong rationale to combine therapeutic cancer vaccines with hormonal abrogation in prostate cancer. Androgen abrogation augments T-cell trafficking to prostate, decreases immune tolerance, increases production of naïve thymic T-cells, enhances cytotoxic T-cell repertoire. PSA TRICOM (PROSTVAC) is a therapeutic, viral-vector based, off-the-shelf, cancer vaccine of PSA & 3 co-stimulatory molecules in phase III testing. This was developed at the NCI in collaboration with Bavarian Nordic Immunotherapeutics. It has demonstrated safety and survival benefit in a randomized phase 2 trial of metastatic castrate resistant prostate cancer (mCRPC). Enzalutamide is a modern androgen receptor inhibitor (ARI) approved for the treatment of mCRPC. Data from the clinical trials with these therapies suggest good individual tolerability without any overlapping toxicities. Analysis of previous trials suggests that vaccines may enhance clinical outcomes with ARI. These data form the scientific basis for a combination approach of a cancer vaccine with ARI to control tumor progression in mCRPC. Methods: A randomized, phase 2, open-label clinical trial at the NCI will enroll 72 chemo-naïve, minimally symptomatic patients with mCRPC. They will be randomized (1:1) to enzalutamide (160 mg daily) alone, or enzalutamide with PSA TRICOM for treatment until radiographic progression. PSA-TRICOM will be administered in a core phase (with day 1, 15 and 29 then 4 additional monthly boosts) followed by continued boosts every 3 months. The primary end point will evaluate time to progression in each arm with secondary endpoints including overall survival and systemic immune responses (lymphocyte subsets, regulatory T-cells, regulatory T-cell function, cytokines, naïve thymic emigrants). If a therapeutic cancer vaccine can enhance the clinical efficacy of a hormonal agent such as enzalutamide, it may help define a new role for vaccines as an adjuvant to standard therapies. We will also evaluate this combination in a second trial in non-metastatic, castration-sensitive patients where this combination may yield its greatest clinical impact.

DNA vaccine with pembrolizumab to elicit antitumor responses in patients with metastatic, castration-resistant prostate cancer (mCRPC).

2017 ◽  
Vol 35 (7_suppl) ◽  
pp. 168-168 ◽  
Author(s):  
Douglas G. McNeel ◽  
Jens C. Eickhoff ◽  
Robert Jeraj ◽  
Mary Jane Staab ◽  
Jane Straus ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Clinical Trial ◽  
T Cells ◽  
T Cell ◽  
Dna Vaccine ◽  
T Cell Activation ◽  
Peripheral Blood ◽  
Cell Activation ◽  
Flt Pet ◽  
Pet Ct

168 Background: We have previously investigated a DNA vaccine encoding prostatic acid phosphatase (PAP, pTVG-HP) in patients with PSA-recurrent prostate cancer, and have demonstrated that this can be safely administered over many months and can elicit PAP-specific T cells. A phase 2 trial is currently underway. In preclinical models, we have found that blockade of regulatory receptors, including PD-1, at the time of T cell activation with vaccination produced anti-tumor responses in vivo. Similarly, we have recently found that patients with prostate cancer previously immunized with a DNA vaccine develop PD-1-regulated T cells. These findings suggested that combined PD-1 blockade with vaccination should elicit superior anti-tumor responses in patients with prostate cancer. Methods: A clinical trial was designed to evaluate the immunological and clinical efficacy of pTVG-HP when delivered in combination or in sequence with pembrolizumab, in patients with mCRPC. Serial biopsies, blood draws, and exploratory FLT PET/CT imaging are being conducted for correlative analyses. Results: While trial accrual continues, 1 of 14 subjects has experienced a grade 3 adverse event. There have been no grade 4 events. Several patients treated with the combination have experienced serum PSA declines, and several have experienced decreases in tumor volume by radiographic imaging at 12 weeks, including one partial response. Expansion of PAP-specific Th1-biased T cells has been detected in peripheral blood samples. Exploratory FLT PET/CT imaging has demonstrated proliferative responses in metastatic lesions and in vaccine-draining lymph nodes. Evaluation of biopsy specimens for recruitment of antigen-specific T cells is currently underway. Conclusions: PD-1 pathway inhibitors have demonstrated little clinical activity to date when used as single agents for treating prostate cancer. Our findings suggest that combining this blockade with tumor-targeted T-cell activation by a DNA vaccine is safe and can augment tumor-specific T cells, detectable within the peripheral blood and by imaging, and result in objective anti-tumor changes. Clinical trial information: NCT02499835.

A phase I study to evaluate the T-cell engager AMV564 alone and in combination with pembrolizumab in subjects with advanced solid tumors.

2020 ◽  
Vol 38 (15_suppl) ◽  
pp. 3101-3101
Author(s):  
Alexander Starodub ◽  
Sarina Anne Piha-Paul ◽  
Raghad Karim ◽  
Curtis Ruegg ◽  
Victoria Smith ◽  
...  
Keyword(s):  
Clinical Trial ◽  
T Cells ◽  
T Cell ◽  
Solid Tumors ◽  
T Cell Activation ◽  
Cell Activation ◽  
Gastroesophageal Junction ◽  
Effector Memory ◽  
Cytotoxic T Cell ◽  
Advanced Solid Tumors

3101 Background: Overcoming the immune-suppressive tumor environment induced by myeloid-derived suppressor cells (MDSC) is a major challenge in immune therapy. CD33 signaling in immature myeloid cells promotes expansion of MDSC and production of immune-suppressive factors. AMV564 is a bivalent, bispecific T-cell engager that binds CD3 and CD33. Preferential binding of AMV564 to areas of high CD33 density enables selective targeting of MDSC. Ex vivo data (Cheng 2017; Blood;130:51) and an ongoing clinical trial in acute myeloid leukemia (NCT03144245) demonstrate the ability of AMV564 to deplete MDSC while sparing monocytes and neutrophils. Methods: In this 3+3 dose escalation study, patients with advanced solid tumors receive AMV564 once daily via subcutaneous (SC) injection for 2 out of 3 wks per cycle, alone or in combination with pembrolizumab (200 mg every 3 wks). Key objectives are to evaluate AMV564 safety, identify a maximum tolerated or recommended phase 2 dose, and evaluate PK, immunophenotype of myeloid and T cell compartments, and preliminary efficacy. Results: Eleven patients have been enrolled: 8 monotherapy (3 at 15 mcg/d, 5 at 50 mcg/d) and 3 combination (5 mcg/d). Tumor types include ovarian (n = 2), small bowel, gastroesophageal junction, endometrial, rectal, penile, urothelial, squamous cell carcinoma (skin), appendiceal, and non-small cell lung. AMV564 was associated with grade (G) 1-2 injection site reactions and G1-2 fevers, which were manageable with acetaminophen and diphenhydramine, as well as G2 weight gain and G3 anemia. No dose-liming toxicity has been observed in any cohort. Three monotherapy patients (15 mcg/d) were evaluable for efficacy with ≥1 on-treatment scan; 2 had SD and 1 PD per RECIST 1.1 criteria. T cell activation, as shown by redistribution from the periphery (margination), was apparent in the first week of dosing for most patients. Compensatory myelopoiesis led to initial expansion of MDSC which were then depleted by AMV564. Increased cytotoxic T cell activation and T-helper (Th) 1 response was evidenced by increased T-bet positive CD4 and CD8 cells and controlled or decreased regulatory T cells. In some patients, effector memory CD8 cell populations (Tem and Temra) were expanded. Conclusions: AMV564 is safe and tolerable when administered SC at doses of 15 mcg/d alone and 5 mcg/d in combination with pembrolizumab. AMV564 depleted MDSC populations and altered T cell profiles consistent with activation of cytotoxic T cells and a Th1 response. Clinical trial information: NCT04128423 .

Targeting tumor-associated macrophage (TAM) mediated inhibition of T-cell migration in prostate cancer using epigenetic modifying agents.

2020 ◽  
Vol 38 (6_suppl) ◽  
pp. 166-166
Author(s):  
David Kosoff ◽  
Leigh Ellis ◽  
David J. Beebe ◽  
Joshua Michael Lang
Keyword(s):  
Gene Expression ◽  
Prostate Cancer ◽  
T Cells ◽  
Cell Migration ◽  
T Cell ◽  
Checkpoint Inhibitors ◽  
Cancer Cell Line ◽  
Cytotoxic T Cell ◽  
Culture Systems ◽  
T Cell Migration

166 Background: Cytotoxic T lymphocytes (CTLs) perform vital anti-tumor functions and are critical to the efficacy of many anticancer therapies. In prostate cancer, the characteristic paucity of activated CTLs within the tumor microenvironment (TME) may be a key factor in disease progression and likely underlies the limited role for immune checkpoint inhibitors (ICIs) in prostate cancer treatment. In this study, we utilized novel microfluidic technologies to evaluate whether TAMs may be driving the exclusion of T cells from the prostate TME and whether the immunosuppressive functions of TAMs could be modified by epigenetic modifying agents. Methods: Primary macrophages and autologous T cells were derived from peripheral blood samples of prostate cancer patients at the University of Wisconsin. Mono-, co-, and tri-culture systems of macrophages, T cells, and 22RV1 cells (androgen-dependent prostate cancer cell line) were cultured in 2D and 3D in microfluidic cell culture platforms. Culture systems were treated with the EZH2 inhibitors (EZH2i) DZNep or EPZ-6438 or left untreated. Macrophages were also treated with M1 (IFN-g) and M2 (IL-4) polarizing cytokines. Systems were analyzed for T cell migration as well as mRNA and protein expression in each cell population. Results: Autologous macrophages inhibited activated T cell migration towards tumor cells in a multi-cellular microscale TME. T cell migration was restored through treatment with EZH2i. Gene expression analysis identified that EZH2i altered macrophage gene expression in the unpolarized and M1/M2 polarized states. In particular, there was increased expression of genes involved in T cell recruitment/chemotaxis, including CXCL10, CXCL11, CXCL12, following EZH2i treatment. Conclusions: We used novel microfluidic technologies to model and analyze multicellular TMEs using primary, patient-derived cells. We demonstrate that TAM-mediated suppression of T cell migration is mediated, in part, through epigenetic pathways, which can be targeted with EZH2i. Treatment with EZH2i, alone or in combination other therapies such as ICIs, may enhance cytotoxic T cell migration and activity in primary prostate cancer.

scholarly journals Product Characteristics and Multi-Arm Clinical Trial Design for TSC-100 and TSC-101, TCR-T Cells That Target Leukemia Following Hematopoietic Cell Transplantation

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 3863-3863
Author(s):  
Shrikanta Chattopadhyay ◽  
Christopher Malcuit ◽  
Ryo Takeuchi ◽  
Emmett Hedblom ◽  
Warren Jaworowicz ◽  
...  
Keyword(s):  
Clinical Trial ◽  
T Cells ◽  
T Cell ◽  
Cell Transplantation ◽  
Trial Design ◽  
Hematopoietic Cell Transplantation ◽  
Clinical Trial Design ◽  
Phase 2 ◽  
Engineered T Cells ◽  
Relapse Rates

Abstract Background: While adoptive cell therapies such as CAR-T therapies have transformed the treatment of lymphoid malignancies by targeting lineage-specific antigens, they have yet to demonstrate safety and efficacy against myeloid malignancies. T cells expressing T cell Receptors (TCRs) for the HLA-A*02:01-restricted minor histocompatibility antigens HA-1 and HA-2 have been observed to clonally expand after hematopoietic cell transplantation (HCT) in donor-recipient pairs mismatched for these antigens. These expanded T cells clones are associated with significantly lower relapse rates (Marijt et al. Proc. Natl. Acad. Sci. 2003; Spierings et al. Biol. Blood Marrow Transplant. 2013) indicating a specific graft versus leukemia effect. Engineered T cells expressing an HA-1-targeting TCR have demonstrated safety and preliminary anti-leukemic activity in patients with relapsed leukemia after HCT (Krakow et al. ASH 2020). We have developed engineered TCR-T cell products, TSC-100 and TSC-101, that target HA-1 and HA-2 respectively for the treatment of leukemias after HCT and present their product characteristics and the clinical trial design here. Methods and Results: To minimize potential safety risks, process variability, and costs associated with lentiviruses, our proprietary T-Integrate manufacturing platform uses a transposon/ transposase system delivered into pan T cells. This enables the introduction of larger vectors with an increased number of functional elements. Our transposon vector encodes both the α and β chains of the TCR under a strong promoter. We find high levels of cell-surface TCR that suppresses endogenous TCRs, thereby minimizing non-specific alloreactivity and potential graft versus host disease (GvHD). In mixed lymphocyte reactions, we find undetectable to minimal alloreactivity of the engineered T cell product compared with non-engineered T cells. The vector also encodes the α and β chains of CD8 ensuring that both CD8+ and CD4+ T cells in the product acquire cytotoxicity and we demonstrate efficient killing of target cells by both T cell types. The vector includes a short peptide tag that is recognized by a GMP-grade antibody, enabling efficient purification of engineered T cells during manufacturing along with the ability to track these T cells in patients. The manufacturing process generates more than 10 billion cells with an estimated vein-to-vein time of ~3 weeks, including product release testing. We routinely find high product purity exceeding 90% engineered T cells, high cytotoxicity in vitro and vector copy numbers <5 copies/cell, ensuring low risks of oncogenicity. The planned clinical trial design is a multi-arm Phase 1/2 trial that includes a control arm for safety and early efficacy comparisons. Patients with AML, ALL and MDS planned for HCT are eligible. Since disease burden is lowest soon after HCT with lower risks of acquired resistance, TCR-T treatment will begin shortly after HCT to prevent disease relapse. Because relapse rates are far higher with reduced intensity conditioning (RIC), only RIC-eligible patients are included. To ensure that all patient-donor pairs are mismatched for the minor antigens, only patients eligible for haploidentical transplantation will be included which enables HLA mismatches. Assignment to treatment or control arms is determined by HLA type as well as the minor antigen status as determined by a PCR-based central lab assay. Since both HA-1 and HA-2 are presented on HLA-A*02:01, all patients with HLA-A*02:01 are eligible for TCR-T treatment. HA-1-positive patients are assigned to the TSC-100 treatment and HA-2 positive patients are assigned to the TSC-101 arm. Donors for these patients are required to be mismatched at either HLA-A*02:01 or the minor antigens. HLA-A*02:01 negative patients will be assigned to the control arm. Analysis of CIBMTR datasets found that this HLA-based 'biological randomization' did not affect outcomes. Dosing of TCR-T cells begins upon count recovery after RIC-HCT and up to three doses will be administered every 40 days if there is no high-grade toxicity. Early readouts of biological activity include monitoring for minimal residual disease and kinetics of donor chimerism. Recruitment begins in Q1 2022 and after the recommended Phase 2 dose has been identified, the study will transition to a Phase 2 study to assess relapse rates of TSC-100- and TSC-101-treated patients versus the control arm. Disclosures Macbeath: TScan Therapeutics: Current Employment, Current equity holder in publicly-traded company.

Phase I trial of anti-PSMA designer T-cell autografting in prostate cancer

2009 ◽  
Vol 27 (15_suppl) ◽  
pp. e16132-e16132
Author(s):  
M. Abedi ◽  
Q. Ma ◽  
A. Bais ◽  
E. Gomes ◽  
E. Beaudoin ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Clinical Trial ◽  
T Cells ◽  
T Cell ◽  
Phase I ◽  
Ex Vivo ◽  
Immune Therapy ◽  
Us Army

e16132 Background: We created chimeric immunoglobulin-T cell receptors (IgTCR) specific for prostate specific membrane antigen (PSMA). When expressed in patient T cells, these “designer T cells” specifically kill prostate cancer cells in vitro and in vivo in animal models, with 5/9 (55%) of xenografted mice experiencing complete remissions (Ma et al. Prostate 2004:61:12–25). A Phase I clinical trial was approved by the FDA in metastatic prostate cancers. Methods: Patient T cells are retrovirally transduced and expanded ex vivo to span dose levels of 10^9 to 10^11 T cells. Adapting methods of Dudley, Rosenberg and colleagues, patients undergo prior non-myeloablative (NMA) conditioning to create a “hematologic space” into which the infused designer T cells will stably engraft for prolonged in vivo efficacy. Patients are co-administered continuous infusion IL2. Outcomes will include Phase Ia goals of safety and toxicity and Phase Ib goals of establishing an optimal biologic dose in terms of designer T cell engraftment and tumor response. Results: For the first two patients, excellent T cell modifications of 50–60% were obtained. After NMA conditioning, T cells were infused and stable engraftments of 1–5% were observed post recovery, even at this lowest 10^9 T cell dose level, thus affirming one of the study end-points. The patients had PSA reductions of 50 and 70% in the two months following treatment. Patients experienced neutropenia and lymphopenia after conditioning, but no designer T cell-related toxicities. Results with additional patients will be described in terms of safety, engraftment efficiency and tumor responses. Conclusions: A new approach to adoptive immune therapy in metastatic prostate cancer has been devised. This clinical trial is funded by the US Army/DOD. No significant financial relationships to disclose.

Phase I trial of anti-PSMA designer T cells in advanced prostate cancer.

2011 ◽  
Vol 29 (7_suppl) ◽  
pp. 130-130
Author(s):  
R. P. Junghans ◽  
R. Rathore ◽  
Q. Ma ◽  
R. Davies ◽  
A. Bais ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Clinical Trial ◽  
T Cells ◽  
T Cell ◽  
Phase I ◽  
Ex Vivo ◽  
Immune Therapy ◽  
Early Results ◽  
Dose Levels

130 Background: We created chimeric immunoglobulin-T cell receptors (IgTCR) specific for prostate specific membrane antigen (PSMA). When expressed in patient T cells, these “designer T cells” (dTc) specifically kill prostate cancer cells in vitro and in vivo in animal models, with 5/9 (55%) of xenografted mice experiencing complete remissions (Ma et al. Prostate 2004:61:12–25). A phase I clinical trial was approved by the FDA. Methods: Patient T cells are retrovirally transduced and expanded ex vivo to span dose levels of 10^9 to 10^11 T cells. Patients undergo prior non-myeloablative (NMA) conditioning to create “hematologic space” into which designer T cells are infused for stable engraftment and prolonged in vivo efficacy. Patients are co-administered continuous infusion IL2. Outcomes include Phase Ia goals of safety and Phase Ib goals of establishing an optimal biologic dose in terms of designer T cell engraftment. Results: Five patients have been treated, three at 10^9 and two at 10^10 cell dose levels. Excellent T cell modifications of 30%-60% were obtained. After NMA conditioning, T cells were infused. Stable engraftments of 1%-20% post-recovery at one month after T cell infusion, thus affirming one of the study end-points. Patients experienced neutropenic fever after conditioning, but no designer T cell-related toxicities. Two patients had partial responses with PSA reductions of 50 and 70% in the two months following treatment with projected benefits of 4 months gain of time to return to starting PSA levels. Results will be updated at the conference. Conclusions: A new approach to adoptive immune therapy in metastatic prostate cancer has been devised with encouraging early results. Patients are being actively recruited. This clinical trial received partial funding from the US Army/DOD. Preclinical work was supported by the Prostate Cancer Foundation. No significant financial relationships to disclose.

scholarly journals Pre-existing immune status associated with response to combination of sipuleucel-T and ipilimumab in patients with metastatic castration-resistant prostate cancer

2021 ◽  
Vol 9 (5) ◽  
pp. e002254
Author(s):  
Meenal Sinha ◽  
Li Zhang ◽  
Sumit Subudhi ◽  
Brandon Chen ◽  
Jaqueline Marquez ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Clinical Trial ◽  
T Cells ◽  
T Cell ◽  
Clinical Response ◽  
T Cell Responses ◽  
Castration Resistant Prostate Cancer ◽  
Cell Responses ◽  
Castration Resistant ◽  
Clinical Responses

BackgroundSipuleucel-T is a US Food and Drug Administration-approved autologous cellular immunotherapy that improves survival in patients with metastatic castration-resistant prostate cancer (mCRPC). We examined whether administering ipilimumab after sipuleucel-T could modify immune and/or clinical responses to this treatment.MethodsA total of 50 patients with mCRPC were enrolled into a clinical trial (NCT01804465, ClinicalTrials.gov) where they received ipilimumab either immediately or delayed 3 weeks following completion of sipuleucel-T treatment. Blood was collected at various timepoints of the study. Luminex assay for anti-prostatic acid phosphatase (PAP) and anti-PA2024-specific serum immunoglobulin G (IgG) and ELISpot for interferon-γ (IFN-γ) production against PAP and PA2024 were used to assess antigen-specific B and T cell responses, respectively. Clinical response was defined as >30% reduction in serum prostate-specific antigen levels compared with pretreatment levels. The frequency and state of circulating immune cells were determined by mass cytometry by time-of-flight and statistical scaffold analysis.ResultsWe found the combination to be well tolerated with no unexpected adverse events occurring. The timing of ipilimumab did not significantly alter the rates of antigen-specific B and T cell responses, the primary endpoint of the clinical trial. Clinical responses were observed in 6 of 50 patients, with 3 having responses lasting longer than 3 months. The timing of ipilimumab did not significantly associate with clinical response or toxicity. The combination treatment did induce CD4 and CD8 T cell activation that was most pronounced with the immediate schedule. Lower frequencies of CTLA-4 positive circulating T cells, even prior to treatment, were associated with better clinical outcomes. Interestingly, these differences in CTLA-4 expression were associated with prior localized radiation therapy (RT) to the prostate or prostatic fossa. Prior radiation treatment was also associated with improved radiographic progression-free survival.ConclusionCombining CTLA-4 blockade with sipuleucel-T resulted in modest clinical activity. The timing of CTLA-4 blockade following sipuleucel-T did not alter antigen-specific responses. Clinical responses were associated with both lower baseline frequencies of CTLA-4 expressing T cells and a history of RT. Prior cancer therapy may therefore result in long-lasting immune changes that influence responsiveness to immunotherapy with sipuleucel-T and anti-CTLA-4.

T Cell Suicide Gene Therapy Prompts Thymic Renewal in Adults After Haploidentical Hematopoietic Stem Cell Transplantation in the Absence of Post-Transplant Immunesuppression

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 1968-1968
Author(s):  
Luca Vago ◽  
Giacomo Oliveira ◽  
Attilio Bondanza ◽  
Maddalena Noviello ◽  
Corrado Soldati ◽  
...  
Keyword(s):  
Clinical Trial ◽  
T Cells ◽  
Stem Cell ◽  
T Cell ◽  
Immune Reconstitution ◽  
Suicide Gene ◽  
Phase Iii ◽  
Hematopoietic Stem ◽  
Donor T Cells

Abstract 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.

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