An Anti-CD7 Antibody-Drug Conjugate Target Showing Potent Antitumor Activity for T-Lymphoblastic Leukemia (T-ALL).

Acute T-lymphoblastic leukemia (T-ALL) is a type of leukemia that can occur in both pediatric and adult populations. Compared to acute B-cell lymphoblastic leukemia (B-ALL), patients with T-cell T-ALL have a poorer therapeutic efficacy. In this study, a novel anti-CD7 antibody-drug conjugate (ADC, J87-Dxd) was successfully generated and used for T-ALL treatment. Firstly, to obtain anti-CD7 mAbs, we expressed and purified the CD7 protein extracellular domain. Utilizing hybridoma technology, we obtained three anti-CD7 mAbs (J87, G73 and A15) with a high affinity for CD7. Both the results of immunofluorescence and Biacore assay indicated that J87 (KD = 1.54 × 10-10 M) had the highest affinity among the three anti-CD7 mAbs. In addition, an internalization assay showed the internalization level of J87 to be higher than that of the other two mAbs. Next, we successfully generated the anti-CD7 ADC (J87-Dxd) by conjugating DXd to J87 via a cleavable maleimide-GGFG peptide linker. J87-Dxd also possessed the ability to recognize and bind CD7. Using J87-Dxd to treat T-ALL cells (Jurkat and CCRF-CEM), we observed that J87-Dxd bound to CD7 was internalized into T-ALL cells. Moreover, J87-Dxd treatment significantly induced the apoptosis of Jurkat and CCRF-CEM cells. The IC50 (half-maximal inhibitory concentration) value of J87-Dxd against CCRF-CEM obtained by CCK-8 assay was 6.3 nM. Finally, to assess the antitumor efficacy of a J87-Dxd in vivo, we established T-ALL mouse models and treated mice with J87-Dxd or J87. The results showed that on day 24 after tumor inoculation, all mice treated with J87 or PBS died, whereas the survival rate of mice treated with J87-Dxd was 80%. H&E staining showed no significant organic changes in the heart, liver, spleen, lungs and kidneys of all mice. In summary, we demonstrated that the novel anti-CD7 ADC (J87-Dxd) had a potent and selective effect against CD7-expressing T-All cells both in vitro and in vivo, and could thus be expected to be further developed as a new drug for the treatment of T-ALL or other CD7-expression tumors.

CD7 activation regulates cytotoxicity-driven pathology in systemic sclerosis, yielding a target for selective cell depletion.

OBJECTIVES: Cytotoxic T cells and natural killer (NK) cells are central effector cells in cancer and infections. Their effector response is regulated by activating and inhibitory receptors. The regulation of these cells in systemic autoimmune diseases such as systemic sclerosis (SSc) is less defined. METHODS: We conducted ex vivo analysis of affected skin and blood samples from 4 SSc patient cohorts (a total of 165 SSc vs 80 healthy individuals) using single-cell transcriptomics, flow cytometry and multiplex immunofluorescence staining. We further analysed the effects of costimulatory modulation in functional assays, and in a severely affected SSc patient who was treated on compassionate use with a novel anti-CD3/CD7 immunotoxin treatment. RESULTS: Here, we show that SSc-affected skin contains elevated numbers of proliferating T cells, cytotoxic T cells and NK cells. These cells selectively express the costimulatory molecule CD7 in association with cytotoxic, proinflammatory and profibrotic genes, especially in recent-onset and severe disease. We demonstrate that CD7 regulates the cytolytic activity of T cells and NK cells and that selective depletion of CD7+ cells prevents cytotoxic cell-induced fibroblast contraction and inhibits their profibrotic phenotype. Finally, anti-CD3/CD7 directed depletive treatment eliminated CD7+ skin cells and stabilised disease manifestations in a severely affected SSc patient. CONCLUSION: Together, the findings imply costimulatory molecules as key regulators of cytotoxicity-driven pathology in systemic autoimmune disease, yielding CD7 as a novel target for selective depletion of pathogenic cells.

Frequency and Prognostic Impact of Aberrant Antigens Expression among Egyptian Adult Acute Leukemia.

OBJECTIVE: Aberrant antigen expression was reported to be due to genetic and epigenetic dysregulation. This study aimed to address aberrant antigen expression and its link to poor prognostic genetic markers in acute leukemia patients. METHODS: This study included 432 newly diagnosed acute leukemia patients (AML, B-ALL). For all included patients blast cells expression for line assignment CD33 CD13 on B-All and CD7 on cytogenetically normal-AML blasts was assessed by flow cytometry in parallel to FLT3 and Philadelphia and philadelphia like chromosome in B-ALL. RESULTS: From the total 432 cases of acute leukemia, the most frequent aberrant antigen expressed in B acute lymphoid leukemia (ALL) was CD33 (23.3%) followed by CD13(16.7%); while the most frequent one in AML was CD7 (16.7%). Aberrant myeloid phenotype in B-ALL was associated with lower mean total leukocytes count (TLC), low platelets count, positive Philadelphia like chromosome, shorter overall survival compared to the B-ALL without. Aberrant lymphoid phenotype (CD7) in AML was associated with a higher platelets count, FLT3 mutation, shorter disease-free and overall survival compared to those patients without. CONCLUSION: CD7 aberrant antigen expression is frequently detected in patients with CN-AML and frequently associated with FLT3 mutation. While in patients with B-ALL the most frequently detected ones are CD33 and CD13 which are frequently associated with Philadelphia like chromosome.

Universal Anti-CD7 CAR-T Cells Targeting T-ALL and Functional Analysis of CD7 Antigen on T/CAR-T Cells.

Chimeric antigen receptor T (CAR-T) cell therapy initiates new methods and turns the scale of clinical treatment on relapsed/refractory acute T lymphoblastic leukemia (T-ALL). In this study, we generated the second-generation CD7-targeting CAR-T cells with a new antigen-binding single-chain variable fragment sequence and made it universal via CRISPR-based knockout of TRAC and CD7 genes (termed UCAR-T). The CD7 UCAR-T cells can efficiently proliferate and lyse T-ALL tumor cell in vitro, along with prominent proinflammatory cytokines secretion. A Jurkat-based xenograft mouse model further verified the superior cytotoxicity of the UCAR-T cells in vivo. During the UCAR-T construction, we observed a CD4/CD8 ratio shift among CD7-/- T/CAR-T cells, which motivated us to further analyze the effects of CD7 antigen on T/CAR-T cells. We sorted out CD7+/- T or anti-CD19 CAR-T cells after partially CD7 knockout and performed functional, phenotypic detection, as well as translational analysis. CD7-/- CAR-T cells tended to be CD8 negative and showed slightly better cytotoxicity at long-term assay. RNA-seq further confirmed an elevation of activated CD4 memory cell subpopulation. However, limited distinction on crucial regulatory genes and pathways was revealed, suggesting the safety and feasibility of UCAR-T application as well as the potential translational rather than transcriptional regulation of CD7 antigen.

Base-Edited CAR7 T Cells for Relapsed T-Cell Acute Lymphoblastic Leukemia.

BACKGROUND: Cytidine deamination that is guided by clustered regularly interspaced short palindromic repeats (CRISPR) can mediate a highly precise conversion of one nucleotide into another - specifically, cytosine to thymine - without generating breaks in DNA. Thus, genes can be base-edited and rendered inactive without inducing translocations and other chromosomal aberrations. The use of this technique in patients with relapsed childhood T-cell leukemia is being investigated. METHODS: We used base editing to generate universal, off-the-shelf chimeric antigen receptor (CAR) T cells. Healthy volunteer donor T cells were transduced with the use of a lentivirus to express a CAR with specificity for CD7 (CAR7), a protein that is expressed in T-cell acute lymphoblastic leukemia (ALL). We then used base editing to inactivate three genes encoding CD52 and CD7 receptors and the ß chain of the αß T-cell receptor to evade lymphodepleting serotherapy, CAR7 T-cell fratricide, and graft-versus-host disease, respectively. We investigated the safety of these edited cells in three children with relapsed leukemia. RESULTS: The first patient, a 13-year-old girl who had relapsed T-cell ALL after allogeneic stem-cell transplantation, had molecular remission within 28 days after infusion of a single dose of base-edited CAR7 (BE-CAR7). She then received a reduced-intensity (nonmyeloablative) allogeneic stem-cell transplant from her original donor, with successful immunologic reconstitution and ongoing leukemic remission. BE-CAR7 cells from the same bank showed potent activity in two other patients, and although fatal fungal complications developed in one patient, the other patient underwent allogeneic stem-cell transplantation while in remission. Serious adverse events included cytokine release syndrome, multilineage cytopenia, and opportunistic infections. CONCLUSIONS: The interim results of this phase 1 study support further investigation of base-edited T cells for patients with relapsed leukemia and indicate the anticipated risks of immunotherapy-related complications. (Funded by the Medical Research Council and others; ISRCTN number, ISRCTN15323014.).

Long-term follow-up of donor-derived CD7 CAR T-cell therapy in patients with T-cell acute lymphoblastic leukemia.

BACKGROUND: Donor-derived CD7-directed chimeric antigen receptor (CAR) T cells showed feasibility and early efficacy in patients with refractory or relapsed T-cell acute lymphoblastic leukemia (r/r T-ALL), in a previous phase I trial report, at a median follow-up of 6.3 months. Here we report long-term safety and activity of the therapy after a 2-year follow-up. METHODS: Participants received CD7-directed CAR T cells derived from prior stem cell transplantation (SCT) donors or from HLA-matched new donors after lymphodepletion. The target dose was 1 × 106 (± 30%) CAR T cells per kg of patient weight. The primary endpoint was safety with efficacy secondary. This report focuses on the long-term follow-up and discusses them in the context of previously reported early outcomes. RESULTS: Twenty participants were enrolled and received infusion with CD7 CAR T cells. After a median follow-up time of 27.0 (range, 24.0-29.3) months, the overall response rate and complete response rate were 95% (19/20 patients) and 85% (17/20 patients), respectively, and 35% (7/20) of patients proceeded to SCT. Six patients experienced disease relapse with a median time-to-relapse of 6 (range, 4.0-10.9) months, and 4 of these 6 patients were found to have lost CD7 expression on tumor cells. Progression-free survival (PFS) and overall survival (OS) rates 24 months after treatment were respectively 36.8% (95% CI, 13.8-59.8%) and 42.3% (95% CI, 18.8-65.8%), with median PFS and OS of respectively 11.0 (95% CI, 6.7-12.5) months and 18.3 (95% CI, 12.5-20.8) months. Previously reported short-term adverse events (< 30 days after treatment) included grade 3-4 cytokine release syndrome (CRS; 10%) and grade 1-2 graft-versus-host disease (GVHD; 60%). Serious adverse events reported > 30 days after treatment included five infections and one grade 4 intestinal GVHD. Despite good CD7 CAR T-cell persistence, non-CAR T and natural killer cells were predominantly CD7-negative and eventually returned to normal levels in about half of the participants. CONCLUSIONS: In this 2-year follow-up analysis, donor-derived CD7 CAR T-cell treatment demonstrated durable efficacy in a subset of patients with r/r T-ALL. Disease relapse was the main cause of treatment failure, and severe infection was a noteworthy late-onset adverse event. TRIAL REGISTRATION: ChiCTR2000034762.

A young woman with persistent sore throat, Epstein-Barr virus, lymphadenopathy, and aberrant CD4 + CD7- T-cells.

A young woman with persistent EBV viremia and lymphocytosis had an abnormal CD4- T cell population with aberrant loss of CD7. She had a diagnosis of chronic active EBV (CAEBV), a lymphoproliferative disorder for which she ultimately required allogeneic hematopoietic stem cell transplantation.

Donor CD7 Chimeric Antigen Receptor T Cell Bridging to Allogeneic Hematopoietic Stem Cell Transplantation for T Cell Hematologic Malignancy.

It is crucial to quickly bridge to allogeneic hematopoietic stem cell transplantation (allo-HSCT) for hematopoietic reconstitution. Here we report on the efficacy and safety of donor CD7 chimeric antigen receptor (CAR) T cell therapy (CAR-T) bridging to allo-HSCT in treating 12 patients with relapsed/refractory (r/r) T-ALL or T-cell lymphoblastic lymphoma (T-LBL). The median time from CAR-T infusion to allo-HSCT was 33.5 days (range, 30 to 55 days). With reduced-intensity conditioning, all patients except 1 successfully engrafted. With a mean follow-up of 301 days (range, 238 to 351 days), the remaining 11 patients were alive and disease-free at their last follow-up. Acute graft-versus-host disease (GVHD) was observed in 3 patients, and chronic GVHD developed in 3 patients, all with a limited pattern. Under the current protocol, infection was the main complication post-transplantation, and all infections were well controlled except in 1 patient, who died of multiple organ failure caused by an infection-induced inflammatory cytokine storm at days 14 post-transplantation. One patient relapsed (CD7+), and 3 patients became minimal residual disease (MRD) positive (CD7+ in 1, CD7- in 1, fusion gene positive only in 1). Subsequently, all 3 of these patients achieved an MRD-negative complete remission with either CD7 CAR-T reinfusion or immunosuppressive agent withdrawal. Our study shows for the first time that a novel strategy of donor CD7 CAR-T bridging to allo-HSCT can be highly effective and feasible in improving disease-free survival for patients with r/r T-ALL or T-LBL.

Naturally selected CD7 CAR-T therapy without genetic editing demonstrates significant antitumour efficacy against relapsed and refractory acute myeloid leukaemia (R/R-AML).

BACKGROUND: The survival rate for patients with relapsed and refractory acute myeloid leukaemia (R/R-AML) remains poor, and treatment is challenging. Chimeric antigen receptor T cells (CAR-T cells) have been widely used for haematologic malignancies. Current CAR-T therapies for acute myeloid leukaemia mostly target myeloid-lineage antigens, such as CD123 and CD33, which may be associated with potential haematopoietic toxicity. As a lineage-specific receptor, CD7 is expressed in acute myeloid leukaemia cells and T cells but is not expressed in myeloid cells. Therefore, the use of CD7 CAR-T cells for R/R-AML needs to be further explored. METHODS: In this report, immunohistochemistry and flow cytometry were used to analyse CD7 expression in clinical samples from R/R-AML patients and healthy donors (HDs). We designed naturally selected CD7 CAR-T cells to analyse various functions and in vitro antileukaemic efficacy based on flow cytometry, and xenograft models were used to validate in vivo tumour dynamics. RESULTS: We calculated the percentage of cells with CD7 expression in R/R-AML patients with minimal residual disease (MRD) (5/16, 31.25%) from our institution and assessed CD7 expression in myeloid and lymphoid lineage cells of R/R-AML patients, concluding that CD7 is expressed in T cells but not in myeloid cells. Subsequently, we designed and constructed naturally selected CD7 CAR-T cells (CD7 CAR). We did not perform CD7 antigen knockdown on CD7 CAR-T cells because CD7 molecule expression is naturally eliminated at Day 12 post transduction. We then evaluated the ability to target and kill CD7+ acute myeloid leukaemia cells in vitro and in vivo. Naturally selected CD7 CAR-T cells efficiently killed CD7+ acute myeloid leukaemia cells and CD7+ primary blasts of R/R-AML patients in vitro and significantly inhibited leukaemia cell growth in a xenograft mouse model. CONCLUSION: Naturally selected CD7 CAR-T cells represent an effective treatment strategy for relapsed and refractory acute myeloid leukaemia patients in preclinical studies.

Autologous Nanobody-Derived Fratricide-Resistant CD7-CAR T-cell Therapy for Patients with Relapsed and Refractory T-cell Acute Lymphoblastic Leukemia/Lymphoma.

PURPOSE: Since CD7 may represent a potent target for T-lymphoblastic leukemia/lymphoma (T-ALL/LBL) immunotherapy, this study aimed to investigate safety and efficacy of autologous CD7-chimeric antigen receptor (CAR) T cells in patients with relapsed and refractory (R/R) T-ALL/LBL, as well as its manufacturing feasibility. PATIENTS AND METHODS: Preclinical phase was conducted in NPG mice injected with Luc+ GFP+CCRF-CEM cells. Open-label phase I clinical trial (NCT04004637) enrolled patients with R/R CD7-positive T-ALL/LBL who received autologous CD7-CAR T-cell infusion. Primary endpoint was safety; secondary endpoints included efficacy and pharmacokinetic and pharmacodynamic parameters. RESULTS: CD7 blockade strategy was developed using tandem CD7 nanobody VHH6 coupled with an endoplasmic reticulum/Golgi-retention motif peptide to intracellularly fasten CD7 molecules. In preclinical phase CD7 blockade CAR T cells prevented fratricide and exerted potent cytolytic activity, significantly relieving leukemia progression and prolonged the median survival of mice. In clinical phase, the complete remission (CR) rate was 87.5% (7/8) 3 months after CAR T-cell infusion; 1 patient with leukemia achieved minimal residual disease-negative CR and 1 patient with lymphoma achieved CR for more than 12 months. Majority of patients (87.5%) only had grade 1 or 2 cytokine release syndrome with no T-cell hypoplasia or any neurologic toxicities observed. The median maximum concentration of CAR T cells was 857.2 cells/µL at approximately 12 days and remained detectable up to 270 days. CONCLUSIONS: Autologous nanobody-derived fratricide-resistant CD7-CAR T cells demonstrated a promising and durable antitumor response in R/R T-ALL/LBL with tolerable toxicity, warranting further studies in highly aggressive CD7-positive malignancies.

T cells expressing CD5/CD7 bispecific chimeric antigen receptors with fully human heavy-chain-only domains mitigate tumor antigen escape.

Bispecific chimeric antigen receptor T-cell (CAR-T) therapies have shown promising results in clinical trials for advanced B-cell malignancies. However, it is challenging to broaden the success of bispecific CAR-T therapies to treat refractory/relapse (r/r) T-cell leukemia/lymphoma because targeting multiple T-cell-expressing antigens leads to exacerbated CAR-T cell fratricide and potential safety concerns. Fully human heavy chain variable (FHVH) antibodies that specifically target CD5 or CD7 were screened and constructed to CD5/CD7 bispecific CARs. A truncated Epidermal growth factor receptor were integrated into CAR constructs to address safety concerns. To tackle the fratricidal issue of CAR-T cells targeting T-cell-pan marker(s), CRISPR/Cas9-based CD5 and CD7 genes knockout were performed before lentiviral transduction of bispecific CARs. Functional comparison between different bispecific CAR structures: tandem CARs and dual CAR were performed in vitro and in vivo to determine the optimal construct suitable for addressing T-cell malignancy antigen escape in clinical setting. Knockout of CD5 and CD7 prevents fratricide of CD5/CD7 bispecific CAR-T cells, and FHVH-derived CD5/CD7 bispecific CAR-T cells demonstrate potent antitumor activity in vitro and in vivo. The fratricide-resistant FHVH-derived CD5/CD7 bispecific CAR-T cells have potent antitumor activity against T-cell malignancies, and tandem CARs are more effective than dual CAR in preventing tumor escape in heterogeneous leukemic cells. The meaningful clinical efficacy and safety of tandem CD5/CD7 CAR-T cells deserve to be explored urgently.

Association of lymphocyte subsets with mortality in severe COVID-19 pneumonia patients.

BACKGROUND: Few studies have investigated the alterations in the T and B cell counts and related subgroups in pulmonary infections especially COVID-19. Here, we aimed to evaluate total T and B lymphocytes and T cell subgroup counts to find the possible correlation between number of these cells and severity and mortality in COVID-19 patients. METHODS: This study was performed on 40 patients with severe COVID-19 infection confirmed by reverse transcription-polymerase chain reaction (RT-PCR) and chest HRCT in August 2020. By the time of admission, T lymphocytes profile in peripheral blood was investigated using multicolor flow cytometry. The total number of T lymphocytes, CD4+ T cells, CD8+ T cells, and B lymphocytes were calculated. Expression of CD2, CD3, CD5, and CD7 as pan T cell surface markers and expression of CD38 and HLA-DR as activated markers on T lymphocytes were also evaluated. RESULTS: Nine patients (22.5%) died during the study and 16 patients (40%) were admitted to ICU. Deceased patients demonstrated lower amounts of T cell count and CD4+ T cell count (with a marginal difference (p = 0.07)) compared with survived patients at the time of admission. The chance of mortality was significantly higher for patients with CD7 loss (OR = 14.89). A marginally significant relationship was also indicated between CD4<200/ml and mortality (OR = 8.65), but no other significant relationships were observed between variables and ICU admission. CONCLUSION: Altogether, CD7 loss on T lymphocytes and CD4+ T cell count below 200/ml revealed a significant relationship with mortality. Considering T lymphocytes and T cell subgroup count could have a predictive value for patients suffering from COVID-19.

CD7-deleted hematopoietic stem cells can restore immunity after CAR T cell therapy.

Targeting T cell malignancies with universal CD7-targeting chimeric antigen receptor T cells (UCART7) can lead to profound immune deficiency due to loss of normal T and NK cells. While a small population of endogenous CD7- T cells exists, these cells are unlikely to be able to repopulate the entire immune repertoire after UCART7 treatment, as they are limited in number and proliferative capacity. To rescue T and NK cells after UCART7, we created hematopoietic stem cells genetically deleted for CD7 (CD7-KO HSCs). CD7-KO HSCs were able to engraft immunodeficient mice and differentiate into T and NK cells lacking CD7 expression. CD7-KO T and NK cells could perform effector functions as robustly as control T and NK cells. Furthermore, CD7-KO T cells were phenotypically and functionally distinct from endogenous CD7- T cells, indicating that CD7-KO T cells can supplement immune functions lacking in CD7- T cells. Mice engrafted with CD7-KO HSCs maintained T and NK cell numbers after UCART7 treatment, while these were significantly decreased in control mice. These studies support the development of CD7-KO HSCs to augment host immunity in patients with T cell malignancies after UCART7 treatment.

Donor-Derived CD7 Chimeric Antigen Receptor T Cells for T-Cell Acute Lymphoblastic Leukemia: First-in-Human, Phase I Trial.

PURPOSE: Patients with relapsed or refractory T-cell acute lymphoblastic leukemia (r/r T-ALL) have few options and poor prognosis. The aim was to assess donor-derived anti-CD7 chimeric antigen receptor (CAR) T-cell safety and efficacy in patients with r/r T-ALL. METHODS: In this single-center, phase I trial, we administered anti-CD7 CAR T cells, manufactured from either previous stem-cell transplantation donors or new donors, to patients with r/r T-ALL, in single infusions at doses of 5 × 105 or 1 × 106 (±30%) cells per kilogram of body weight. The primary end point was safety with efficacy secondary. RESULTS: Twenty participants received infusions. Adverse events including cytokine release syndrome grade 1-2 occurred in 90% (n = 18) and grade 3-4 in 10% (n = 2), cytopenia grade 3-4 in 100% (n = 20), neurotoxicity grade 1-2 in 15% (n = 3), graft-versus-host disease grade 1-2 in 60% (n = 12), and viral activation grade 1-2 in 20% (n = 4). All adverse events were reversible, except in one patient who died through pulmonary hemorrhage related to fungal pneumonia, which occurred at 5.5 months, postinfusion. Ninety percent (n = 18) achieved complete remission with seven patients proceeding to stem-cell transplantation. At a median follow-up of 6.3 months (range, 4.0-9.2), 15 remained in remission. CAR T cells were still detectable in five of five patients assessed in month 6, postinfusion. Although patients' CD7-positive normal T cells were depleted, CD7-negative T cells expanded and likely alleviated treatment-related T-cell immunodeficiency. CONCLUSION: Among 20 patients with r/r T-ALL enrolled in this trial, donor-derived CD7 CAR T cells exhibited efficient expansion and achieved a high complete remission rate with manageable safety profile. A multicenter, phase II trial of donor-derived CD7 CAR T cells is in progress (NCT04689659).

Prognostic value of lymphoid marker CD7 expression in acute myeloid leukemia patients undergoing allogeneic hematopoietic cell transplantation in first morphological complete remission.

Although defined as a lymphoid surface marker, CD7 is aberrantly expressed on a subtype of acute myeloid leukemia cells and appears to be associated with an inferior response to chemotherapy. Allogeneic hematopoietic cell transplantation (allo-HCT) is a potentially curative modality but no data has been reported in CD7-positive AML patients. We performed a retrospective analysis involving 141 AML patients who underwent allo-HCT in first morphological complete remission (CR1). The results showed that CD7-positive AML patients had a poor 2-year overall survival (64.5% vs 82.0%, P = 0.040), relapse-free survival (RFS) (56.5% vs 79.4%, P = 0.005), and higher cumulative incidence of relapse (27.0% vs 9.7%, P = 0.003) post-HCT. In addition, expression of CD7 was related to RAS and RUNX1 mutation, and high residual disease level pre-HCT. Multivariate analyses showed CD7 expression at diagnosis was an independent risk factor for RFS (P = 0.016, HR = 0.418) and relapse (P = 0.014, HR = 0.307). We concluded that for AML patients in CR1, CD7 is a negative predictor for allo-transplant outcomes.

An antibody-drug conjugate with intracellular drug release properties showing specific cytotoxicity against CD7-positive cells.

Refractory T cell acute leukaemias that no longer respond to treatment would benefit from new modalities that target T cell-specific surface proteins. T cell associated surface proteins (the surfaceome) offer possible therapy targets to reduce tumour burden but also target the leukaemia-initiating cells from which tumours recur. Recent studies of the T cell leukaemia surfaceome confirmed that CD7 is highly expressed in overt disease. We have used an anti-CD7 antibody drug conjugate (ADC) to show that the binding of antibody to surface CD7 protein results in rapid internalization of the antigen together with the ADC. As a consequence, cell killing was observed via induction of apoptosis and was dependent on cell surface CD7. The in vitro cytotoxic activity (EC50) of the anti-CD7 ADC on T cell acute leukaemia (T-ALL) cells Jurkat and KOPT-K1 was found to be in the range of 5-8 ng/mL. In a pre-clinical xenograft model of human tumour growth expressing CD7 antigen, growth was curtailed by a single dose of ADC. The data indicate that CD7 targeting ADCs may be developed into an important second stage therapy for T cell acute leukaemia, for refractory CD7-positive leukaemias and for subsets of acute myeloid leukaemia (AML) expressing CD7.

Base-edited CAR T cells for combinational therapy against T cell malignancies.

Targeting T cell malignancies using chimeric antigen receptor (CAR) T cells is hindered by 'T v T' fratricide against shared antigens such as CD3 and CD7. Base editing offers the possibility of seamless disruption of gene expression of problematic antigens through creation of stop codons or elimination of splice sites. We describe the generation of fratricide-resistant T cells by orderly removal of TCR/CD3 and CD7 ahead of lentiviral-mediated expression of CARs specific for CD3 or CD7. Molecular interrogation of base-edited cells confirmed elimination of chromosomal translocations detected in conventional Cas9 treated cells. Interestingly, 3CAR/7CAR co-culture resulted in 'self-enrichment' yielding populations 99.6% TCR-/CD3-/CD7-. 3CAR or 7CAR cells were able to exert specific cytotoxicity against leukaemia lines with defined CD3 and/or CD7 expression as well as primary T-ALL cells. Co-cultured 3CAR/7CAR cells exhibited highest cytotoxicity against CD3 + CD7 + T-ALL targets in vitro and an in vivo human:murine chimeric model. While APOBEC editors can reportedly exhibit guide-independent deamination of both DNA and RNA, we found no problematic 'off-target' activity or promiscuous base conversion affecting CAR antigen-specific binding regions, which may otherwise redirect T cell specificity. Combinational infusion of fratricide-resistant anti-T CAR T cells may enable enhanced molecular remission ahead of allo-HSCT for T cell malignancies.

Chimeric antigen receptor T cells targeting CD7 in a child with high-risk T-cell acute lymphoblastic leukemia.

Effective systemic treatments for relapsed or refractory T-cell acute lymphoblastic leukemia (T-ALL) are limited. Recent clinical application of chimeric antigen receptor (CAR) immunotherapy has demonstrated successful control of B-cell malignancies by CAR-T cells; however, designing CARs for T-ALL remains a challenge. CD7 overexpression in T-cell malignancies may be an attractive target for immunotherapy in T-ALL. This study aimed to describe the safe and effective use of autologous CD7-CAR T cells (4SCAR7) for the treatment of T-ALL with induction failure in an 11-year-old patient. Based on The Chinese Children's Cancer Group-ALL (CCCG-ALL) study protocol, minimal residual disease (MRD) by flow cytometry (FC) analysis was detected on days 19 and 46 of remission induction. At the end of remission-induction chemotherapy, the patient achieved morphologic complete remission, though with MRD 16.13% and RT-PCR of KMT2A-MLLT1 fusion positive, which indicated induction failure. The cerebrospinal fluid (CSF) was negative for blasts at diagnosed. CAR-T therapy and allogeneic transplant were recommended as the next treatment options. CD3+ lymphocytes were collected from the patient 18 days after the high-dose MTX chemotherapy through leukapheresis. The 4SCAR7 CD7-targeting CAR-T cells were generated thereafter. The patient received lymphodepleting chemotherapy prior to 4SCAR7 infusion. Oral administration of itraconazole and sulfamethoxazole was performed from day 0 after CAR-T cell infusion. The patient did not have hypotension, hypoxia, or serious biochemical change or abnormality, but had fever on day 9. Although grade 1 cytokine-release syndrome (CRS) was diagnosed, it was successfully treated with ibuprofen. Anti-CD7 CAR transgene copy numbers in peripheral blood were determined by qPCR, which showed effective expansion initially, then dropped quickly, and persisted at a low level. Although experienced cytopenia from days 14 to 21, the patient achieved remission on day 17. After complete remission, the patient received hematopoietic stem cell transplantation (HSCT) and has recovered well to thisdate. Overall, this report suggested that 4SCAR7 could be a safe and effective strategy for the treatment of pediatric patients with high-risk T-cell malignancies.

CD2 and CD7 are sensitive flow cytometry screening markers for T-lineage acute leukemia(s): a study of 465 acute leukemia cases.

T-lymphoblastic leukemia/lymphoma (T-ALL/LBL) is a rare acute leukemia that expresses cytoplasmic CD3 (cCD3) and frequently lacks surface CD3. Given that routine flow cytometric testing for cCD3 may not be feasible and cCD3 interpretation may be difficult, we investigate if surface CD2 and/or CD7 expression on blasts can be used by flow cytometry to screen for T-lineage acute leukemia. We retrospectively reviewed flow cytometric data from 233 acute leukemias (36 T-ALL/LBL, 8 mixed-phenotype acute leukemia T/myeloid, 80 acute myeloid leukemia, 97 B-ALL/LBL, 8 mixed-phenotype acute leukemia B/myeloid, and 4 acute undifferentiated leukemia cases). Uniform expression (≥75% of blasts) of CD2 and/or CD7 was seen in all 44 cCD3-positive cases but in only 11% (20/189) of cCD3-negative acute leukemias, thus demonstrating 100% sensitivity and 89% specificity in the identification of cCD3-positive (T-lineage) acute leukemia. To avoid selection bias, we prospectively studied 232 consecutive acute leukemias for which cCD3, CD2, and CD7 were automatically performed in all cases. Similar to the retrospective study, uniform expression of CD2 and/or CD7 on blasts showed 100% sensitivity and 88% specificity in the screening for cCD3-positive (T-lineage) acute leukemia. Therefore, acute leukemias with uniform expression of CD2 and/or CD7 warrant further testing for cCD3 to evaluate for T-lineage acute leukemia. Blasts that lack both uniform CD2 and CD7 expression do not require additional cCD3 testing. We propose that CD2 and CD7 could be utilized in a limited antibody flow cytometry panel as a sensitive, robust, and cost-effective way to screen for T-lineage acute leukemia.