T-cell Lymphoblastic Lymphoma Research Articles

T-cell lymphoblastic lymphoma in constitutional mismatch repair deficiency (CMMRD): Exploring treatment opportunities.

T-cell lymphoblastic lymphoma in constitutional mismatch repair deficiency (CMMRD): Exploring treatment opportunities.

A safety and efficacy study of allogeneic haematopoietic stem cell transplantation for refractory and relapsed T-cell acute lymphoblastic leukaemia/lymphoblastic lymphoma patients who achieved complete remission after autologous CD7 chimeric antigen receptor T-cell therapy.

CD7-targeted chimeric antigen receptor T-cell (CAR-T) therapy has shown promising initial complete remission (CR) rates in patients with refractory or relapsed (r/r) T-cell acute lymphoblastic leukaemia and lymphoblastic lymphoma (T-ALL/LBL). To enhance the remission duration, consolidation with allogeneic haematopoietic stem cell transplantation (allo-HSCT) is considered. Our study delved into the outcomes of 34 patients with r/r T-ALL/LBL who underwent allo-HSCT after achieving CR with autologous CD7 CAR-T therapy. These were compared with 124 consecutive T-ALL/LBL patients who received allo-HSCT in CR following chemotherapy. The study revealed that both the CAR-T and chemotherapy cohorts exhibited comparable 2-year overall survival (OS) (61.9% [95% CI, 44.1-78.1] vs. 67.6% [95% CI, 57.5-76.9], p = 0.210), leukaemia-free survival (LFS) (62.3% [95% CI, 44.6-78.4] vs. 62.0% [95% CI, 51.8-71.7], p = 0.548), non-relapse mortality (NRM) rates (32.0% [95% CI, 19.0-54.0] vs. 25.3% [95% CI, 17.9-35.8], p = 0.288) and relapse incidence rates (8.8% [95% CI, 3.0-26.0] vs. 15.8% [95% CI, 9.8-25.2], p = 0.557). Patients aged ≤14 in the CD7 CAR-T group achieved high 2-year OS and LFS rates of 87.5%. Our study indicates that CD7 CAR-T therapy followed by allo-HSCT is not only effective and safe for r/r T-ALL/LBL patients but also on par with the outcomes of those achieving CR through chemotherapy, without increasing NRM.

Antitumor Effect of Triptolide in T-Cell Lymphoblastic Lymphoma by Inhibiting Cell Viability, Invasion, and Epithelial-Mesenchymal Transition via Regulating the PI3K/AKT/mTOR Pathway [Retraction].

[This retracts the article DOI: 10.2147/OTT.S149788.].

MRD at the end of induction and EFS in T-cell lymphoblastic lymphoma: Children’s Oncology Group trial AALL1231

AbstractDefining prognostic variables in T-lymphoblastic lymphoma (T-LL) remains a challenge. AALL1231 was a Children’s Oncology Group phase 3 clinical trial for newly diagnosed patients with T acute lymphoblastic leukemia or T-LL, randomizing children and young adults to a modified augmented Berlin-Frankfurt-Münster backbone to receive standard therapy (arm A) or with addition of bortezomib (arm B). Optional bone marrow samples to assess minimal residual disease (MRD) at the end of induction (EOI) were collected in T-LL analyzed to assess the correlation of MRD at the EOI to event-free survival (EFS). Eighty-six (41%) of the 209 patients with T-LL accrued to this trial submitted samples for MRD assessment. Patients with MRD <0.1% (n = 75) at EOI had a superior 4-year EFS vs those with MRD ≥0.1% (n = 11) (89.0% ± 4.4% vs 63.6% ± 17.2%; P = .025). Overall survival did not significantly differ between the 2 groups. Cox regression for EFS using arm A as a reference demonstrated that MRD EOI ≥0.1% was associated with a greater risk of inferior outcome (hazard ratio, 3.73; 95% confidence interval, 1.12-12.40; P = .032), which was independent of treatment arm assignment. Consideration to incorporate MRD at EOI into future trials will help establish its value in defining risk groups. CT# NCT02112916.

T-cell non-Hodgkin lymphoma of lymphoblastic type revealed by a chronic swollen testicle managed in the urology department of Laquintinie Hospital in Douala, Cameroon

Background: Non-Hodgkin T-cell lymphomas typically develop in lymph node territories, and primary extra nodal locations are rare. The clinical presentation is nonspecific, dominated by signs of compression. Imaging aids in suspicion, and histology confirms the diagnosis. Clinical Observation: A 61-year-old patient initially hospitalized for the management of upper gastrointestinal bleeding six months ago was referred to the urology outpatient clinic due to a chronic swollen testicle persisting for a year. A non-contributory testicular ultrasound showed peri scrotal lymphedema with inguinal lymphadenopathy, right orchid epididymitis, and left epididymitis. Blood tests were normal. Despite antibiotic therapy, there was no improvement in the clinical condition. Physical examination revealed painless and mobile cervical, axillary, and inguinal lymph nodes. Pelvic MRI suspected a probable lymphoma. A lymph node biopsy in the left groin confirmed a non-Hodgkin T-cell lymphoma of lymphoblastic type infiltrating the capsule. The patient was transferred to haematology for further management. Conclusion: T-cell lymphoblastic lymphoma is primarily characterized by nodal involvement. There is a diagnostic delay that is anatomopathological in nature. Management involves polychemotherapy.

Key candidate genes and pathways in T lymphoblastic leukemia/lymphoma identified by bioinformatics and serological analyses.

T-cell acute lymphoblastic leukemia (T-ALL)/T-cell lymphoblastic lymphoma (T-LBL) is an uncommon but highly aggressive hematological malignancy. It has high recurrence and mortality rates and is challenging to treat. This study conducted bioinformatics analyses, compared genetic expression profiles of healthy controls with patients having T-ALL/T-LBL, and verified the results through serological indicators. Data were acquired from the GSE48558 dataset from Gene Expression Omnibus (GEO). T-ALL patients and normal T cells-related differentially expressed genes (DEGs) were investigated using the online analysis tool GEO2R in GEO, identifying 78 upregulated and 130 downregulated genes. Gene Ontology (GO) and protein-protein interaction (PPI) network analyses of the top 10 DEGs showed enrichment in pathways linked to abnormal mitotic cell cycles, chromosomal instability, dysfunction of inflammatory mediators, and functional defects in T-cells, natural killer (NK) cells, and immune checkpoints. The DEGs were then validated by examining blood indices in samples obtained from patients, comparing the T-ALL/T-LBL group with the control group. Significant differences were observed in the levels of various blood components between T-ALL and T-LBL patients. These components include neutrophils, lymphocyte percentage, hemoglobin (HGB), total protein, globulin, erythropoietin (EPO) levels, thrombin time (TT), D-dimer (DD), and C-reactive protein (CRP). Additionally, there were significant differences in peripheral blood leukocyte count, absolute lymphocyte count, creatinine, cholesterol, low-density lipoprotein, folate, and thrombin times. The genes and pathways associated with T-LBL/T-ALL were identified, and peripheral blood HGB, EPO, TT, DD, and CRP were key molecular markers. This will assist the diagnosis of T-ALL/T-LBL, with applications for differential diagnosis, treatment, and prognosis.

Nelarabine-containing salvage therapy and conditioning regimen in transplants for pediatric T-cell acute lymphoblastic leukemia and lymphoma.

Therapy for relapsed or refractory (r/r) T-cell acute lymphoblastic leukemia (T-ALL) and T-cell lymphoblastic lymphoma (T-LBL) in children is challenging, and new treatment methods are needed. We retrospectively analyzed eight patients with r/r T-ALL (five patients) and T-LBL (three patients) who were treated with nelarabine (NEL) plus etoposide, cyclophosphamide, and intrathecal therapy, administered 3days apart. Five patients achieved a complete response, and the other three achieved a partial response (PR). All patients underwent hematopoietic stem cell transplantation (HSCT) after two cycles of treatment, except for one patient who received one cycle. Three patients who had previously received HSCT were treated with reduced-intensity conditioning regimens, including fludarabine, melphalan, and NEL; one survived for over 5years after the second HSCT. Grade 2 neuropathy occurred in one patient, but other severe toxicities commonly associated with NEL were not observed during NEL administration in combination with chemotherapy. The 2-year overall survival and event-free survival rates were 60.0% and 36.5%, respectively. The addition of NEL to reinduction chemotherapy was useful in achieving remission and did not lead to excessive toxicity. In addition, a conditioning regimen, including NEL, appeared to be effective in patients who had previously undergone HSCT.

Cerebrospinal fluid cytology-assisted diagnosis of T-lymphoblastic lymphoma: A case report

Background: Lymphoblastic lymphoma is a rare form of highly aggressive non-Hodgkin lymphoma. The most common clinical manifestations are superficial lymphadenopathy and mediastinal mass. In a few cases, invasion of the central nervous system is the first manifestation. It is also difficult to diagnose patients using the central nervous system as the first manifestation. Here, we report the case of a 26-year-old man with central nervous system disease as the primary manifestation; we used cerebrospinal fluid cytology (CSF-C) for early diagnosis and shared the importance of CSF-C for early diagnosis of T-cell lymphoblastic lymphoma. Case presentation: The patient was admitted to the hospital because of “right eyelid closure weakness with headache for 1 month and exacerbation with sluggish response for 1 week.” Physical examination revealed a bilateral Kernig sign (+) and Lasgue sign (+). The Mini-Mental State Examination and Montreal Cognitive Assessment scores were 20 (out of 30). When there was no abnormality in the imaging examination, the patient was misdiagnosed with meningoencephalitis and received anti-inflammatory treatment because the initial symptom was a clinical manifestation of the central nervous system, and the imaging and blood tests showed no definite abnormality. Cerebrospinal fluid has been studied and second-generation sequencing detection, such as after CSF-C tip to abnormal lymphocytes, to open the breakthrough of the diagnosis of lymphoma. Conclusions: In the cases with central nervous system injury as the first manifestation, CSF-C was combined with immunohistochemistry and cerebrospinal fluid flow cytometry to provide a clear and effective method and evidence for the early diagnosis of T-cell lymphoblastic lymphoma.

A Retrospective Comparison of Allogenic and Autologous Hematopoietic Stem Cell Transplantation in Patients with T-Cell Lymphoblastic Lymphoma

Background: T-cell lymphoblastic lymphoma (T-LBL) is a rare type of non-Hodgkin's lymphoma accounting for 1%~2% of non-Hodgkin's lymphoma. T-cell lymphoblastic lymphoma is typically found in children and young adults, frequently affecting the mediastinum and bone marrow. It has a poor prognosis and develops quickly. It is anticipated that hematopoietic stem cell transplantation will significantly enhance the prognosis. We conducted a retrospective single center analysis aiming to compare the survival outcomes of autologous and allogeneic hematopoietic stem cell transplantation in patients with T-cell lymphoblastic lymphoma. Methods: From our center's database, we track down 92 individuals who underwent T-LBL transplantation between August 2011 and June 2022, including 77 individuals who got allogeneic hematopoietic stem cell transplants and 15 patients who underwent autologous hematopoietic stem cell transplants. Results：For the baseline characteristics of patients,there were significant differences in IPNHLSS staging, bone marrow involvement, IPI score and pre transplant status between Auto-HSCT group and Allo HSCT group.Group allo-HSCT had a higher proportion of bone marrow involvement (57.1% vs. 26.7%,p=0.031), a higher proportion of IPNHLSS staging as IV (57.1% vs. 26.7%,p=0.001) and a lower proportion of CR1 pre transplantations (51.9% vs. 86.7%,p=0.080). Figure 1 had shown the survival between auto-HSCT group and allo-HSCT group.Among the 15 patients who received auto-HSCT, 2 patients received allogeneic transplantation after relapse, 1 patient died after 3.1 months of survival after secondary transplantation, and 1 patient still survived after secondary transplantation.The 3-year OS rate of auto-HSCT group was 87.7%, while the 3-year OS rate of allo-HSCT group was 65.0%（P=0.086).The 3-year PFS rate of auto-HSCT group was 74.0%, while the 3-year PFS rate of allo-HSCT patients was 73.3%（P=0.95). The 3-year NRM rate of auto-HSCT group was 0%, while the 3-year NRM rate of allo-HSCT group was 9.9%（P=0.127). The 3-year CIR rate of auto-HSCT group was 21.0%, while the 3-year NRM rate of allo-HSCT group was 25.3%（P=0.514). Conclusion: Hematopoietic stem cell transplantation can significantly improve the prognosis of patients with T-cell lymphoblastic lymphoma. In our study, patients with T-cell lymphoblastic lymphomareceiving autologous hematopoietic stem cell transplantation and those receiving allogeneic hematopoietic stem cell transplantation have distinct baseline data, hence their survival rates also differ.

Gene-Edited Universal CD7 Chimeric Antigen Receptor T Cells for Pediatric T-Cell Acute Lymphoblastic Leukemia or Lymphoblastic Lymphoma

Background: T-cell acute lymphoblastic leukemia (T-ALL) and T-cell lymphoblastic lymphoma (T-LBL) are highly aggressive T-lineage malignancies characterized by an infiltration of immature T cells in the bone marrow (BM) and peripheral blood (PB) or extramedullary organ involvements. Effective treatments were elusive, and the long-term survival of patients with refractory/relapsed (R/R) T-ALL/LBL remains poor despite allogeneic hematopoietic stem cell transplantation (allo-HSCT). CAR-T therapies for T-cell malignancies remain underdeveloped due to the shared antigenicity between normal and malignant T cells. CD7 is highly expressed on the surface of T-ALL/LBL T cells and is considered a viable CAR-T therapeutic target. However, CD7-targeting immunotherapies may be compromised by T-cell fratricide and extermination. And one of the biggest challenges with autologous CAR-T cell therapy is to isolate a sufficient number of healthy T cells from malignant T cells. Thus, clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR9-associated protein 9 (Cas9)-mediated gene ablation has been used to produce universal CD7-targeted CAR T cells (UCD7-CAR) from suitable healthy donors that no longer express CD7 and TCR. In vitro killing tests, animal tests, and phase 1 clinical trials have preliminarily verified the efficacy and safety of universal CD7 CAR-T cells. Here we investigated the safety and efficacy of the universal CD7 CAR-T therapy in phase 2 clinical trial(NCT05454241) for pediatric R/R T-ALL/LBL patients. Aims: To investigate the efficacy and safety of the universal CD7 CAR-T therapy for pediatric R/R T-ALL/LBL patients. Methods: Patients over three years of age whose disease failed ≥ 2 lines of therapies and had ≥ 80% CD7 expression were eligible, including those who relapsed within 12 months after complete response or relapsed more than 12 months after complete response and failed to achieve remission induced by one or more courses of standard treatment; and patients with recurrence after hematopoietic stem cell transplantation. A lymphodepletion regimen was administered to all patients using fludarabine (30 mg/m2 per day) and cyclophosphamide (500 mg/m2 per day) for three consecutive days (day -5 to day -3) before CAR-T infusion. Patients received one single infusion of UCD7-CAR T cells at a median dose of 2.0×10^6/kg. Consolidative allo-HSCT after remission was allowed after day 28 after UCD7-CART infusion at the discretion of the physician and patient preference. All surviving patients were followed until July 15, 2023; the median follow-up was 109 days (54 to 117 days). Results: Five eligible children, 1 with r/r T-LBL and 4 with r/r T-ALL, were enrolled between December 2022 and April 2023 (Table 1). The median age of the patients was 5 (4-11) years. One girl(Patient 04) had a history of allo-HSCT before enrollment. Patients were heavily pretreated with a median of 3(2-6) lines of therapies. At registration, the median proportion of blasts in 4 T-ALL patients was 47.275% (6.0%-56.0%) in BM by FCM along with CNS(n=2) or testis(n=1) involvement. In contrast, 1 T-LBL patient(patient 02) did not have BM blasts but with bulky mediastinal masses ≥7 cm in diameter. All five patients had no or mild CRS (no CRS, n=1; grade 1, n=3; grade 2, n=1), and most(n=4) did not show symptoms of neurotoxicity. Patient 04, who received a prior allo-HSCT approximately seven months before CAR-T therapy, had a Herpes virus 6 (HHV-6B) encephalitis on day 17 after CAR-T infusion, but no GVHD was observed. On day 28, 4 of 5 (80.0%) patients who had BM involvement achieved MRD-negative complete remission (CR; n=2) or CR with incomplete hematologic recovery (CRi; n=2); but patient 02 with bulky mediastinal masses did not have an obvious response. Until the cutoff date, patient 04 still kept a sustained MRD negative CR; patient 05 relapsed again 49 days after CAR-T infusion, and the other three patients received a subsequent allo-UCBT with a CR state. All the children are still alive. Conclusion:UCD7-CAR T therapy is a safe and highly effective pediatric T-ALL/LBL treatment. More patients and longer follow-ups are needed for validation.

Oncogenetic-Driven Targeted Therapy for Relapsed/Refractory T-Cell Acute Lymphoblastic Leukemia : A French ALL-Target Observatory Report

Introduction T-cell acute lymphoblastic leukemia (T-ALL) is an orphan disease diagnosed mostly in adolescent and young adults. In adult population, 5-10% of T-ALL patients (pts) will be primary refractory and 30-40% will relapse. In relapse/refractory (R/R) patients, standard of care treatments, including nelarabine, yield response rate of about 20-40% and responses are of short duration. On behalf of the GRAALL (Group for Research on Adult Acute Lymphoblastic Leukemia), we launched the ALL-TARGET project combining a precision medicine platform dedicated to R/R T-ALL and T-cell lymphoblastic lymphoma (T-LL), and an observatory to evaluate therapeutic proposals based on mutational profile and intracellular signaling pathways alterations. Objectives and methods Leukemic samples from pts with R/R T-ALL/LL were shipped to the GRAALL T-ALL central laboratory in France (V. Asnafi, Hôpital Necker). Biological characterization comprised oncogenetic, phenotypic and in some cases functional analysis. Clinical data from R/R T-ALL/LL pts were collected in a real-life observatory (NCT05832125). Adults pts were eligible if an oncogenetic characterization was available at diagnosis or relapse, and if they received a salvage, either with conventional therapy or with a targeted therapeutic option (TTO). For example, TTOs included Tofacitinib and Venetoclax (Tofa/Ven) in case of IL7R (CD127) expression or IL7R-pathway alterations (IL7R ALT), 5-azacytidine and Venetoclax (Aza/Ven) in case of T-ALL/LL with epigenetic regulators alterations (DNMT3A, ASXL1, PHF6, TET2, PRC2, IDH1/2, SRSF2...) or Temsirolimus, Erwinase and Venetoclax (Tem/Erw/Ven) in case of PI3K signaling pathway alterations (PI3K ALT). The ALL-TARGET Observatory primary endpoint was overall response rate (ORR) including complete remission (CR), CR with incomplete hematological recovery and partial response. We report here the results of the first pts included, with a focus on those who received TTOs as salvage therapy. Results Eighty-nine were analyzed, including 80 T-ALL and 9 T-LL. Sex ratio was 3 and median age at diagnosis was 37.5y, and 51y at the time of the first TTO. Seventy-one pts were in relapse (79.7%) and 18 primary refractory (20.2%). Relapses occurred after a median first CR duration of 16.6 months (range: 2.5-92), with 62.8% in bone marrow, 30% in CNS and 30.3% in other extramedullary sites. Phenotype at diagnosis was available for 68 pts, including 36 Early T-cell Precursor (ETP or near-ETP) (52.9%), 6 immature non-ETP (8.8%), 20 cortical (29.4%) and 6 mature phenotype (8.8%). IL7R-expression was available for 53 pts, of whom 40 were IL7R+ (75.5%) and 13 IL7R- (24.5%). Out of 50 samples with available BCL2-expression, 47 were BCL2+ (94%) and 3 BCL2- (6%). IL7R ALT were evidenced in 41 pts (48.2%), PI3K ALT in 21 pts (24.7%), RAS pathway alterations (RAS ALT) in 19 pts (22.4%) and epigenetic dysregulation in 42 pts (49.4%). Ten pts harbored TP53/ATM mutations (11.7%) . These different alterations could coexist. At relapse, 33 phenotypes were reported, showing 22 ETP (66.6%), 2 immature non-ETP (6%) and 9 cortical (27.3%). IL7R-expression was available for 26 pts, among which 21 were IL7R+ (63.6%) and 5 IL7R- (19.2%). NGS was performed in 24 patients, revealing IL7R ALT in 9 pts (37.5%), PI3K ALT in 6 pts (25%), RAS ALT in 5 pts (20.8%) and epigenetic dysregulation in 15 pts (62.5%). Nine patients had TP53 mutations (37.5%). Twenty-five patients received a TTO, including 14 Aza/Ven (56%), 8 Tofa/Ven (32%), 2 Tem/Erw/Ven (8%) and 1 Trametinib/Ven (4%). Among these, 8 were in first salvage (32%), 10 in 2 nd (40%), and 6 in 3 rd/4 th salvage (28%). Of note, 14 patients received Ven associated with chemotherapy, including 4 Nelarabine-Ven, and 3 Ven in monotherapy. By 3 months, the cumulative incidence of response under the chosen TTO was 70.7% (95%CI:51-88) (Figure). Ten of 14 patients were in response after Aza/Ven (ORR 71.4%), 4 of 8 patients after Tofa/Ven (50%) and 2 of 2 patients treated with Tem/Erw/Ven (100%). Five patients were bridged to allogeneic stem cell transplantation. Conclusion Our results demonstrate the feasibility of the ALL-TARGET project. A better knowledge of the oncogenetic landscape of T-ALL, and a close collaboration between clinicians and biologists, resulted in individualized treatment strategies. With a 3 months cumulative incidence of response of 70%, TTOs appear to be a promising approach in R/R T-ALL.

Comparative Analysis of Immune Effector Cell-Associated Hematotoxicity (ICAHT) and Infection Incidence Following CD19-Targeted CAR-T Therapy Versus CD7-Targeted CAR-T Therapy

Introduction CD19 CAR-T cell therapy has been revolutionizing the treatment of refractory /relapsed (R/R) B-cell acute lymphoblastic leukemia (B-ALL) over the past decade. While CD7 CAR-T therapy, an innovative approach, has only recently been applied over the last three years in our center to treat R/R T-cell acute lymphoblastic leukemia (T-ALL) and T-cell lymphoblastic lymphoma (T-LBL). While there are studies and guidelines from EBMT addressing hematologic toxicity, specifically Immune Effector Cell-Associated Hematotoxicity (ICAHT), following CD19 CAR-T treatment, the literature is still scarce on ICAHT occurrence post-CD7 CAR-T therapy. Here we conducted a retrospective study aiming at comparing ICAHT and infection incidences following the two distinct CAR-T therapies. Methods Data were extracted from two separate clinical trials. The CD19 CAR is structured with CD19 scFv, CD28-hinge, 4-1BB costimulatory region, and CD3ζ activation domains. T cells were activated by CD3/CD28 microbead 2 days before CD19-CAR lentivirus infection. “Naturally selected” anti-CD7 CAR-T cells (NS7CAR) were transduced an anti-CD7 CAR into bulk peripheral T lymphocytes via a lentivirus vector. NS7CAR is a 2nd generation murine-based CAR-T containing 4-1BB and CD3ζ co-stimulatory domains. All patients received lymphodepletion regimens of fludarabine (30 mg/m 2/d) and cyclophosphamide (300 mg/m 2/d) from Day -5 to Day -3 before CAR-T infusion. A single infusion of either CD19 CAR-T or CD7 CAR-T cells was administrated at a medium dose of 1×10 6/kg. Fitted patients undergo consolidation allogeneic hematopoietic stem cell transplantation (Allo-HSCT) within 1-3 months after CAR-T cell infusion. The hematology toxicity and infection were analyzed during the period from CD19 CAR-T or CD7 CAR-T cell infusion to Allo-HSCT. Hematology toxicity is graded according to “ICAHT: EHA/EBMT Consumption Grading and Best Practice Recommendations” (Table 1). Infection diagnosis includes both etiological diagnosis and imaging diagnosis. Results Between June 1, 2019, and September 22, 2022, 60 patients with R/R B-ALL patients received CD19 CAR-T therapy (https://clinicaltrials.gov NCT04546893, and NCT04792593). Meanwhile, between December 1, 2020, and July 16, 2022, 60 patients with R/R T-ALL/LBL received CD7 CAR-T therapy (NCT04572308, NCT04916860). The CD19 CART group had 19 patients ≤ 14 years old, with a male/female gender ratio of 33:27. The CD7 CART group had 20 patients ≤ 14 years old, with a gender ratio of 49:11. The incidence of severe early ICAHT (Grade III+IV, day 0-30) from CD19 CAR-T cells infusion to allo-HSCT was observed to be 18.3%, which was lower than the incidence of the early ICAHT post CD7 CAR-T therapy at 33.3%, p =0.035. However, the incidence of severe late ICAHT (after day+30) following CD19 CAR-T and the CD7 CAR-T therapy was similar: 27.8% vs. 28.6%, with no statistical difference( p=0.57). There was no statistical difference between CD19 CAR-T and CD7 CAR-T therapy groups in the infection rates with 28.3%vs. 36.7%, p=0.33. In the CD19 CAR-T group, bacterial infections were noted in 10 patients: 6 with Gram-positive bacteria (1 Enterococcus, 1 Streptococcus agalactis, and 4 Staphylococcus), and 4 with Gram-negative bacteria (1 Pseudomonas aeruginosa, 2 Acinetobacter baumannii, and 1 Klebsiella pneumoniae). Viral infections were observed in 7 patients (EBV 2, CMV 2, BKV 3), and 1 had fungal infection. Infection sites included pulmonary infections (7 cases), sepsis (10 cases), and other areas (4 cases). Post-CD7-CAR-T, bacterial infections were observed in 9 cases, 7 with Gram-positive bacteria (6 Staphylococcus, and 1 Streptococcus bradycardia) and 2 with Gram-negative bacteria (1 Pseudomonas aeruginosa, and 1 Klebsiella pneumoniae). Six cases had viral infections (EBV 2, CMV 2, HHV1 type 1, parainfluenza virus 1), and 6 with fungal infections. Infection sites included pulmonary infection (12 cases), sepsis (10 cases), and other areas (5 cases). Conclusions Our study noted a slightly higher incidence of ICAHT within 30 days following CD7 CAR-T infusion compared to CD19 CAR-T therapy. However, there was no statistical difference in the incidence of ICAHT beyond the 30-day. There was no statistical difference for infection rate after CD19 CAR-T and CD7 CAR-T. In both groups, Gram-positive bacteria were primary responsible for bacterial infections.

Long-Term Outcomes of T-Cell Acute Lymphoblastic Leukemia and Risk Factors for Survival in a Multicenter Registry Study from Brazil

Introduction T-cell acute lymphoblastic leukemia (T-ALL) constitutes around 25% of all newly diagnosed cases of acute lymphoblastic leukemia (ALL) in adults. While most pediatric treatment protocols categorize patients (pts) based on their phenotype, this approach is seldom applied to adults. Nevertheless, there is a scarcity of reported cohorts specifically focusing on adult T-ALL. Often, these cases are studied alongside B-cell cases, despite their notable biological differences, or grouped with T-cell lymphoblastic lymphoma, which exhibits a more favorable prognosis compared to T-ALL. The objective of this study is to present outcomes and identify prognostic factors for survival of adults newly diagnosed with T-ALL, utilizing data from a real-world multicenter registry study conducted in Latin America. Methods This registry encompassed four different academic centers in Brazil. The study included pts aged 15 years and above newly diagnosed with T-ALL between January 2009 and June 2022. Clinical data were collected from medical records after ethical approval. Overall (OS) and event-free (EFS) survivals were calculated by Kaplan-Meier method, with Cox regression multivariate analysis (MVA) for finding risk factors and competing risk analysis for relapse. Results A total of 97 pts were included, with a median age of 27 years (range, 15 - 82). Thymic T-ALL accounted for 51% of the cases. Mediastinal bulky was found in 48% and positivity of initial cerebrospinal fluid (CSF) evaluation was 12.5% (by morphology or flow cytometry). Baseline features of this cohort are summarized in table 1. Most pts (88%) were treated with pediatric-inspired regimens (asparaginase [ASP]-based), mostly adapted GMALL (43%) and adapted BFM (22%). Native E. coli ASP was used in 76% and pegylated ASP (PEG-ASP) was used in remaining cases. During presentation or treatment, 15% of the subjects experienced thrombosis of any site, with most cases being associated with the use of ASP (64%) and diagnosed during induction (64%). Following the frontline regimen, 77.3% of pts achieved complete response (CR). Overall, 11.3% of pts died during the induction phase, while 8% were primary refractory. Univariate analysis for CR showed correlation with age (p=0.002), bulky size (p=0.016), and use of ASP (p=0.009). Median follow-up period was 6 years. Overall, allogeneic stem cell transplant (alloHSCT) was performed in 18 pts, being 11/18 in first CR. Five-year OS and 5y EFS were 43.7% (95% confidence interval [CI]: 34.4-55.5) and 36.4% (95% CI 27.9-47.5), respectively. Over the follow-up, 5-year relapse rate and non-relapse mortality (NRM) were 35.6% and 27.9%, respectively. Among pts who underwent alloHSCT, 5y OS was 64%. In the univariate analysis, older age (HR 1.02 [1.01-1.04], p&amp;lt;0.01) was associated with lower OS. Conversely, thymic T-ALL (HR 0.54 [0.3-0.96], p=0.03) and use of ASP (HR 0.35 [0.17-0.716], p&amp;lt;0.01) were associated with higher OS. Initial white blood cell count was not statistically associated with OS. Subsequently, we performed a subgroup analysis focusing on the adult and young adult population (AYA, age between 15-45 years). In this subgroup (n=85), 89% were treated with pediatric-inspired regimens and 5y OS was 46.5%. In the univariate analysis, thrombosis (HR 2.21 [1.09-4.48], p=0.02) was associated with lower OS, while thymic T-ALL (HR 0.48 [0.24-0.93], p=0.03) and the use of ASP (HR 0.317 [0.13-0.75], p&amp;lt;0.01) were associated with higher OS. In the MVA for AYA, thymic T-ALL (HR 0.50 [0.25-0.98], p=0.04) and thrombosis (HR 2.23 [0.97-5.13], p=0.054) remained associated with OS, while older age was not (HR 1.004 [0.96 - 1.04], p=0.81) (Figure 1). Conclusions Reported outcomes of T-ALL in this registry from Latin America are comparable to older reports from large groups worldwide. Currently, European groups have reported OS rates surpassing 70% for adults with T-ALL.However, in our setting, even in the AYA population, OS was disappointing. This could be attributed to increased NRM due to treatment toxicity and limited access to HSCT, which may have contributed to these findings. As previously reported, thymic T-ALL remains a lower-risk subtype. Additionally, thrombosis has emerged as an independent risk factor for OS in the AYA population, which is a novel finding that warrants further research. To the best of our knowledge, this is the first study specifically focusing on adult T-ALL from Latin America.

Frailty in Children and Adolescents with Lymphoblastic Leukemia or Lymphoma Receiving Maintenance Chemotherapy - a Pilot Study

Background: Increased survivorship of childhood cancer has revealed a number of long-term morbidities related to treatment. Evidence suggests that cancer and its treatment may accelerate normal loss of physiologic capacity that occurs during aging.The advanced physiologic aging and related morbidities often seen in childhood cancer survivors suggests that these patients may present with signs of early-onset frailty. Frailty is a measure of global infirmity and impaired physical function and has been correlated with adverse health outcomes and elevated incidence of mortality in the general population. Research into the incidence and applicability of the frailty phenotype in children being treated for cancer may aid in the identification of the most vulnerable patients and identify those who may require intervention. The purpose of this study is to explore the frailty phenotype in children and adolescents receiving maintenance chemotherapy for acute lymphoblastic leukemia or lymphoma. Methods: We prospectively recruited children and adolescents (aged 5-18 years-old) diagnosed with acute lymphoblastic leukemia or lymphoma in the first cycle of their maintenance chemotherapy. Frailty was assessed twice: at an initial visit in cycle 1 maintenance treatment (V1), and 6-months following the initial assessment (V2). The frailty phenotype consists of 5 domains, which were assessed using developmentally appropriate measures: 1) Slowness: 6-minute walk test; 2) Weakness: Handgrip strength dynamometry - calibrated to the size of the participant's hand; 3) Exhaustion/Fatigue: The PedsQL TM Multidimensional Fatigue Scale; 4) Body Composition: InBody 270 body composition analyzer; and 5) Physical activity/Energy expenditure: Self-administered physical activity questionnaire for older children (PAQ-C) and physical activity questionnaire for adolescents (PAQ-A).Each assessment was scored individually and “Frailty points” were assigned based on age and sex-based normative z-scores or survey scores, and a composite “Frailty Score” ranging from 0=least frail to 25=most frail. Wilcoxon signed-rank test was used to compare V1 and V2 frailty scores. Results:The analysis sample consisted of 19 participants (mean age 9.1 [SD=3.4] years old; 63% female) who completed V1 and 7 participants that completed V2. Diagnoses of participants who completed V1 include precursor B-Cell acute lymphoblastic leukemia (n=15), T-Cell acute lymphoblastic leukemia (n=3), and T-Cell lymphoblastic Lymphoma (n=1). Median V1 z-scores and survey scores per domain are as follows: Slowness: z-score -3.11 [-4.02, -2.48]; Weakness: z-score -1.48 [-2.06, -1.38]; Exhaustion/Fatigue: score 58.3 [46.5, 70.8]; Body composition: z-score (total body fat) 0.90 [0.47, 1.79]; Physical activity/Energy expenditure: score 2.26 [1.73, 2.54]. Domain specific frailty score for V1 are displayed in Figure 1. Of the 7 participants with a V2 frailty assessment, paired analysis demonstrated significant improvement in Exhaustion/Fatigue (median score V1=56.94, V2=70.83 [p=0.016]). However, improvements in weakness, body composition, and physical activity/energy expenditure did not reach statistical significance. Median slowness z-scores at V2 were similar to V1. Median composite frailty score improved from 12 to 11 in V2 but was not statistically significant (p=0.054). Comparison of V1 and V2 overall composite scores are displayed in Figure 2. Conclusion: Children and adolescents receiving maintenance chemotherapy for acute lymphoblastic leukemia or lymphoma scored poorly in all five domains of frailty. We observed some improvements in exhaustion/fatigue, and trending improvements in subdomain and composite frailty scores in the small sample of participants with V1 and V2 assessments. Given that frailty has been shown to persist into adulthood in survivors of childhood cancer, the frailty assessment may be an effective tool for identifying patients who may require additional intervention. Initial and follow-up frailty measurements for this study are currently ongoing.

A Parallel Comparison of the Safety and Efficacy of Allogeneic Hematopoietic Stem Cell Transplantation for Refractory and Relapsed T-ALL/Lbl Patients Who Achieved Complete Remission with CD7 CAR-T Versus Patients Who Achieved First Complete Remission with Chemotherapy before Transplantation

Introduction We have developed a fratricide-resistant CD7 CAR-T cells from bulk T cells transduced with CD7 CAR without gene editing or additional gene transfer, named naturally selected CD7 CAR-T (NS7CAR-T). NS7 CAR-T therapy has shown a robust complete remission (CR) rate in patients with refractory or relapsed (R/R) T-cell acute lymphoblastic leukemia and T-cell lymphoblastic lymphoma (T-ALL/LBL). Nonetheless, the risk of relapse remains a challenge post-CD7 CAR-T therapy alone, suggesting the potential benefits of consolidation allogeneic hematopoietic stem cell transplantation (allo-HSCT). The question remains whether CD7 CAR-T therapy could increase the incidence of post-transplant complications. Here we conduct a parallel study to compare the safety and efficacy of allo-HSCT in R/R T-ALL/LBL patients who achieved CR with NS7 CAR-T therapy vs those who reached first CR (CR1) using chemotherapy prior to transplantation. Methods Between November 2020 and January 2023, a total of 223 consecutive patients with T-ALL/LBL who underwent allo-HSCT at our center were retrospectively analyzed. Patients who met the following criteria were included in this parallel study: 1) underwent the first allo-HSCT in our hospital, 2) achieved CR before transplantation either from NS7CAR-T therapy or CR1 from chemotherapy (Fig. 1). A total of 139 patients met the criteria for analysis and underwent allo-HSCT after achieving CR either from NS7CAR-T therapy (n=43) or chemotherapy (CR1=96). The median patient age at the time of transplantation was 15 years (range: 1-51 years). The median follow-up time was 370 days (2-941 days). CD7 CAR-T patients were from two clinical trials registered at www.clinicaltrials.gov NCT04572308, NCT04916860. Transplant donor types included sibling identical (n=12), haploidentical (n=110), and unrelated donors (n=17). We used total body irradiation (TBI)-based conditioning regimens (n=128) or Busulfan/Melphalan-based regimens (n=11). To prevent graft-versus-host disease (GVHD), we used ATG along with a short-term regimen combining methotrexate, cyclosporine/tacrolimus, and mycophenolate mofetil. Results The characteristics of patients from both groups are detailed in Table 1. The median interval between CD7 CAR-T treatment and transplantation was 59 (39-131) days. Within the CAR-T group, 16 patients had primary refractory disease, 18 had relapsed disease and 9 in minimal residual disease (MRD)-positive status in bone marrow before CD7 CAR-T therapy. Prior to CAR-T therapy, 55.8% (24 patients) had extramedullary lesions. In comparing the CAR-T and chemotherapy CR1 groups, we observed no significant differences in long-term efficacy post-allo-HSCT. The 2-year leukemia-free survival (LFS) rates were 64.9 (95% CI, 49.1-79.2)% and 69.8 (95% CI, 59.0-79.6)% (p=0.340); the 2-year overall survival (OS) rates were 64.1 (95%CI, 48.0-78.6)% and 71.8 (95%CI, 60.5-81.9)% (p=0.107); the 2-year relapse incidence (RI) rates were 9.3 (95%CI, 3.7-23.7)% and 11.5 (95%CI, 6.4-20.7)% (p=0.873); and the 2-year non-relapsed mortality (NRM) rates were 28.3 (95% CI, 16.9-47.4)% and 21.6 (95% CI, 13.9-33.4)% (p=0.244), for the CD7 CAR-T and non-CAR-T groups, respectively. The incidence of all grades of acute GVHD (aGVHD) 37.2 (95%CI, 25.2-54.9)% vs. 42.1 (95%CI, 33.3-53.3)% did not significantly differ between the CAR-T and non-CAR-T groups. A trend toward an increased rate but no P significance was observed in Grade 3-4 aGVHD incidence of 20.93 (95%CI, 11.7-37.4)% vs. 9.5 (95%CI, 5.1-17.6)% (p=0.139). One-year incidences of moderate to severe chronic GVHD (cGVHD) were 12.2 (95%CI, 5.4-28.0)% and 18.0 (95%CI, 11.5-28.0)% (p=0.357) in the CD7CAR-T and non-CAR-T groups, respectively (Table 2). No statistically significant differences were detected in the occurrences of transplant-associated thrombotic microangiopathy (TA-TMA), CMV, EBV, and HHV-6 infections between the two groups. Upon analyzing, we found that r/r patients who received allo-HSCT after achieving remission with NS7 CAR-T had a similar OS to CR1 patients (Fig. 2). Conclusions Our parallel study showed that T-ALL/LBL patients, who achieved CR via CD7 CAR-T therapy followed by a consolidation allo-HSCT, had similar favorable OS and LFS compared to patients who underwent allo-HSCT in the CR1 state induced by chemotherapy. This was achieved without increasing the incidence of GVHD, infections, or TA-TMA.

CD7 CAR-T Therapy Followed By a Second Transplant for T-Cell Acute Lymphoblastic Leukemia or Lymphoblastic Lymphoma Patients Who Relapsed after a Prior Transplant

Background The therapeutic options for patients with T-cell acute lymphoblastic leukemia or lymphoblastic lymphoma (T-ALL/LBL) who relapse after hematopoietic stem cell transplantation (HSCT) are currently restricted. CD7-targeted chimeric antigen receptor (CAR) T-cell therapy provides a promising avenue towards remission, yet the long-term prognosis for these patients still needs to be improved. The advantages of progressing to a second transplant post-CAR-T treatment remain uncertain due to limited data. In this study, we analyzed the clinical characteristics and transplantation outcomes of 16 T-ALL/LBL patients who, having relapsed after their initial transplantation, achieved complete remission (CR) in bone marrow (BM) and CR/partial remission (PR) in extramedullary lesions via CD7 CAR-T therapy and then opted for a second allogeneic HSCT (allo-HSCT) at our center. Our aim is to explore strategies to enhance the survival rate of these patients. Methods From January 2021 to January 2023, we analyzed T-ALL/LBL patients who underwent second transplantation at Hebei Yanda Lu Daopei Hospital. The patients included in this study met the following criteria: they had relapsed following their first HSCT and had subsequently undergone CD7 CAR-T therapy prior to the second transplantation. The follow-up cut-off date was till June 1, 2023. The median follow-up duration after the second transplantation was 178 days, ranging from 9 to 500 days. Results A total of 16 patients including 13 with T-ALL and 3 with T-LBL were enrolled. There were 14 males and 2 females. The donor of first transplantation was autologous(n=3), sibling identical(n=2), unrelated donor(n=2), or haplo-identical (n=9). After the first transplantation, 8 patients relapsed in bone marrow (BM) and 8 relapsed both in BM and extramedullary sites. Of these, 13 patients received autologous CD7 CAR-T, one patient received donor-derived CD7 CAR-T, and one patient was treated with universal CAR-T cells. After the CD7 CAR-T therapy, all 16 patients (100%) achieved minimal residual disease (MRD)-negative CR in BM, and 6 out of 8 patients (75%) achieved CR in extramedullary lesions. Only two patients exhibited PR in the extramedullary lesions. The median age at the time of the second transplantation was 28 years (range 14-42 years). The median time from diagnosis to the second transplantation was 683 days (range 385-2672 days). The median interval between the first and second transplantation was 438 days (range 229-2540 days), and the median interval from CD7 CAR-T infusion to the second transplantation was 72 days (range 31-92 days). For the second transplantation, 13 cases had haplo-identical donors and 3 cases had unrelated donors. The conditioning regimens utilized were either total body irradiation (TBI)-based (n=9), busulfan-based (n=6), or melphalan-based (n=1). Following the 2 nd transplant, the 1-year overall survival(OS) and leukemia-free survival(LFS) were 58.5% (95% CI, 28.9-85.0%) and 51.4% (95% CI, 22.4-79.9%), respectively(Figure 1). The 1-year relapse incidence (RI) and non-relapse mortality (NRM) were 15.9% (95% CI, 4.4-57.8%) and 31.5% (95% CI, 13.2-74.9%), respectively. The cumulative incidence of CMV and EBV viremia at day 100 were 75.0% (95% CI, 56.5-99.5%) and 19.8% (95% CI, 7.2-54.6%), respectively. The cumulative incidence of all grades acute graft-versus-host disease (aGVHD) and 3-4 grade aGVHD at day 100 were 56.3% (95%CI, 36.5-86.7%) and 25% (95%CI, 10.7-58.4%), respectively. One-year chronic GVHD(cGVHD) was observed in 25.1% of the cases (95%CI, 9.3-67.4%), while moderate to severe cGVHD was not found in any patient. Following the 2 nd transplant, a total of 6 patients died, including 3 from infection, 2 from relapse and 1 from intracranial hemorrhage. Conclusions Our initial findings suggest that even in refractory/relapsed T-ALL/LBL patients who have experienced relapse following previous HSCT, MRD-negative complete remission can potentially be achieved utilizing CD7 CAR-T cell therapy. The subsequent implementation of a second allo-HSCT appears feasible. Combining CAR-T therapy with a follow-up second HSCT presents a strategy for these heavily pre-treated patients, offering promising prospects for survival. However, further evaluation of this treatment approach is required, necessitating long-term monitoring and a larger patient cohort.

Phase 1 Dose Escalation Study of the Anti-CD7 CAR-T Therapy in Relapsed/Refractory T-Cell Acute Leukemia and Lymphoblastic Lymphoma

Introduction Inspired by the successful experience of CAR-T therapy in B-cell malignancies, its introduction to T-cell tumors is being studied. CD7, highly expressed on T-cell tumors, provides a potential target for CAR-T therapy. However, it is also present on normal T and NK cells, leading to possible fratricide of CAR-T during the production and elimination of T and NK cells after infusion. Moreover, CD7 was suggested to express on parts of hematopoietic stem cells (HSC). Thus, apart from the clinical efficacy and safety, the manufacture and hematopoietic toxicity (HPT) are essential topics related with anti-CD7 CAR-T therapies. Here, we reported the preliminary results of phase I clinical trial of anti-CD7 CAR-T (SENL101, dual CD7-nanobodies with 4-1BB co-stimulation domain and CD7 gene unmodified) to address these issues in CD7 + T-cell acute leukemia and lymphoblastic lymphoma (T-ALL and T-LBL) patients. Methods Informed volunteers were screened according to the inclusion and exclusion criteria. Specially, tumors negative for CD4 and CD8, or the tumor load in peripheral blood less than 1% are required. CD4 and CD8 positive selection was employed for T-cell isolation. Lentivirus encoding CAR vector was transduced in CD7 unedited T-cells. The clinical trial was a single-arm, open-label, dose-escalation and predictive study. One day after a 3-day FC chemotherapy, patients were infused with SENL101 at a dose of 1E6, 2E6 or 4E6/ kg. The efficacy, safety and pharmacokinetics of CAR-T were assessed at specified time points. Results As of July 24 th 2023, 7 patients were treated with the specified dose of SENL101, including 5 T-LBL and 2 T-ALL. The average age was 33 years old, and the median prior therapy lines was 3. 28.6% patients experienced HSC transplantation (HSCT). SENL101 was successfully produced in all patients, with an average cell viability of 87.1% and CAR + rate of 92.3%. Complete response (CR) rate was 100% ( Figure 1A). One patient (E006) received HSCT after CR and continued to survive at the present. One case (E002) relapsed at 3-month follow-up, with CAR copy number16740 /ug DNA and CD7 negative in T and NK cells. Notably, 1 patient (E003) developed B-cell lymphoproliferative disease, with primary disease well controlled. The other 4 patients were in CR or hemogram incomplete-recovered CR (CRi), with the longest remission of 9 months. Unfortunately, 2 patients (E005 and E008) died of sepsis at day 116 and 137. CAR-T expanded robustly in all cases, with a median peak value of 701600 copies/ ug DNA reached at day 14. The median survival of CAR-T in vivo was 133 days. As the removal of CAR-T, the CD7 + T and NK cells recovered. The cytokine release syndrome (CRS) happened in 6 cases, with 5 grade 1-2 CRS and 1 grade 3 CRS. No immune effector cell-associated neurotoxicity syndrome was observed. All patients occurred grade 4 HPT. At day 28, 28.6% grade 4 leukopenia and 57.1% grade 4 thrombocytopenia persisted ( Figure 1B). Infections were observed in 3 out of 7 cases (including 2 CMV, 1 EBV and 2 sepsis). Other AEs, including transaminase elevation (3/7), malaise (2/7), anorexia (2/7), nausea/vomiting/diarrhea (1/7) and flu like symptoms (1/7) were relieved after treatment. Due to the high infectious rate (2 sepsis) and profound reduction of hemocyte in the 2E6/kg group, 1E6/kg was set as dose of an expanded cohort. Conclusions Withoutinterfering CD7,SENL101 can be well manufactured. The treatment was effective for T-ALL/LBL, with tolerable toxicity at a dose of 1E6 cells/kg. SENL101 expanded robustly but persisted shortly, which on the other hand, contributed to the recovery of CD7 + T and NK cells, thereby reducing the risk of infection. An expanded cohort is warranted to verify the long-term benefit of SENL101 for T-cell malignant patients.

A New t(7;9)(p12;q34) Involving NOTCH1 and IKZF1 in Pediatric T-Cell Lymphoblastic Lymphoma

Background Notch1 pathway activation is demonstrated in approximately 50% of T-cell acute lymphoblastic leukemias/lymphomas (T-ALL/LL) mainly by the presence of activating somatic mutations of NOTCH1 involving homodimerization and/or PEST (proline, glutamic acid, serine, threonine) domains. The oncogenic role of NOTCH1 was however primarily described with the characterization of the recurrent although rare t(7;9)(q34;q34). By positioning the coding region of the intracellular part of Notch1 (ICN1) under the control of the TCR beta-gene promoter, this translocation generates a truncated Notch1 receptor resulting in constitutive activation of the Notch1 pathway, independent of ligand binding. In murine models ICN1 is much more pro-oncogenic than NOTCH1 activating mutations. While several retrospective studies identified NOTCH1 activating mutations as an independent good-prognostic factor in human T-ALL/LL, search for truncated ICN1 in NOTCH1 wild-type patients was usually not performed/considered. Aim To describe and characterize a new translocation in a pediatric patient with T-LL. Method Somatic cytogenetics of blastic T-cells from diagnosis was explored by conventional karyotype. A specific fluorescence in situ hybridization (FISH) Breakapart probe was designed to explore the NOTCH1 locus on chromosome 9q34. Targeted locus amplification based sequencing (TLA) using genomic DNA was used to confirm/determine the partners involved in the new fusion found. Targeted RNA-sequencing using the Illumina TruSight RNA Fusion Panel was used to determine the putative transcript produced by the fusion. Results The patient, a 14-year-old young female, was diagnosed with stage 3 T-LL characterized by a large mediastinal mass with massive pleural effusion. Flow cytometry demonstrated a CD7+, CD1a+, CD4+/CD8+ double positive phenotype corresponding to EGIL type III T-LL. Conventional karyotype on T-lymphoblastic cells showed two clonal abnormalities, a deletion del(6)(q13q22) and a translocation t(7;9)(p12;q34) in 10 metaphases analyzed. Involvement of NOTCH1 in this new t(7;9)(p12;q34) was confirmed by molecular cytogenetics using a FISH Breakapart probe targeting the NOTCH1 locus. Targeted locus amplification based sequencing (TLA) revealed IKZF1 as the fusion partner involved in this new fusion. DNA sequencing revealed a predictive fusion between the intracellular domain of NOTCH1 (ICN1; breakpoint in intron 26 (NM_017617.5)) and IKF1 (breakpoint in intron 5 (NM_006060)). The targeted RNA-sequencing performed on the pleural effusion confirmed an in frame NOTCH1-IKZF1 fusion transcript. Sequencing of exons 26-27 and 34 of NOTCH1 showed wild-type alleles. After a swift response to the induction phase, the patient is in complete remission one year after completing her treatment according to the EuroLB-02 protocol. Summary/perspectives This new t(7;9)(p12;q34) involving ICN1 illustrates the importance to look for ICN1 more extensively in parallel to NOTCH1/FBXW7 mutations in the screening of Notch1 activation pathway in T-ALL/LL specially in the event of a stratification on Notch1 status for treatment. As both NOTCH1 and IKZF1 are major actors of normal T-cell differentiation/proliferation, the oncogenic role of the fusion NOTCH1::IKZF1 in T-ALL/LL deserves a better understanding in a larger population and will be further explored.

Targeting hyperactive platelet-derived growth factor receptor-β signaling in T-cell acute lymphoblastic leukemia and lymphoma.

T-cell acute lymphoblastic leukemia (T-ALL) and T-cell lymphoblastic lymphoma (T-LBL) are rare aggressive hematologic malignancies. Current treatment consists of intensive chemotherapy leading to 80% overall survival but is associated with severe toxic side effects. Furthermore, 10-20% of patients still die from relapsed or refractory disease providing a strong rationale for more specific, targeted therapeutic strategies with less toxicities. Here, we report a novel MYH9::PDGFRB fusion in a T-LBL patient, and demonstrate that this fusion product is constitutively active and sufficient to drive oncogenic transformation in vitro and in vivo. Expanding our analysis more broadly across T-ALL, we found a T-ALL cell line and multiple patient-derived xenograft models with PDGFRB hyperactivation in the absence of a fusion, with high PDGFRB expression in TLX3 and HOXA T-ALL molecular subtypes. To target this PDGFRB hyperactivation, we evaluated the therapeutic effects of a selective PDGFRB inhibitor, CP-673451, both in vitro and in vivo and demonstrated sensitivity if the receptor is hyperactivated. Altogether, our work reveals that hyperactivation of PDGFRB is an oncogenic driver in T-ALL/T-LBL, and that screening T-ALL/T-LBL patients for phosphorylated PDGFRB levels can serve as a biomarker for PDGFRB inhibition as a novel targeted therapeutic strategy in their treatment regimen.

A-159 Role of TCRB1 Antibody in the Evaluation Panel of T Lymphoproliferative Diseases

Abstract Background The diagnosis of T lymphoproliferative diseases is usually a challenge due to the difficulty indifferentiating pathological T cells from reaction cells and also due to the limitation of clonalitytests currently available. TCRB1 is a monoclonal antibody specific for region 1 of the TCR T cellreceptor Beta chain constant, detecting clonal populations of TCRab positive T cells in caseswhere its expression is monotypic. Its application is similar to immunoglobulin light chainrestriction in the detection of B cell lymphoproliferations and in normal T CD3 + TCRab + cells, theexpression of this marker is polytypic. The objective of the present work is to report theexperience of including this antibody in the lymphoproliferative T panel in a private laboratoryin southern Brazil. Methods Samples received with indication of lymphoproliferative disease and lymphocytosis wereevaluated using the tube Lymphocyte Screnning Tube—LST (Euroflow) and were acquired usingFACS CANTO or FACS LYRIC cytometers. Analyzes were performed using Infinicyt software. After, all, samples that showed alteration in the CD4/CD8 ratio, or antigen alteration in the expressionof pan T markers were evaluated for the complete investigation panel according to Euroflowprotocol. This panel had the incorporation of the tube for the evaluation of clonality that hasthe TCRB1 antibody in the PE channel associated with the anchor markers CD45V500, CD3PerCpcy5, CD4V450 and CD8APCH7. The channels that were not used (FITC, APC, Pecy7) areused when necessary, to evaluate antigens that can help select the desired aberrant population,such as CD5, CD2, CD7 antibodies or to assess maturation, like CD45RA and CD27. Data werecollected from the beginning of the use of this antibody from February 2021 until the presentmoment. Results During this period, 2870 samples for immunophenotyping analysis were received, of which 17cases were T chronic lymphoproliferative diseases. Of the 17 cases found, 11 (65%) were caseswith the pathological population TCRab positive and the expression of TCRB1 could beevaluated. In these cases, the expression of the patologic cells was monotypic for the TCRB1antigen. The cases were: 4 large granular lymphocytic (LGL) leukemia, 4 Adult T-cellleukemia/lymphoma /Peripheral T-cell lymphoma, unspecified , 1 Sezary syndrome, 1 T-celllymphoblastic lymphoma in cortical/common thymocyte stage and 1 T-cell prolymphocyticleukemia (T-PLL). Recent studies have demonstrated the high specificity of this test for clonality, as long as it is associated with an expanded and standardized lymphoproliferative panel. Thepresent cases demonstrated good results for peripheral blood samples, bone marrow and lymphnode biopsy. Conclusion T-lymphoproliferative disorders remain a diagnostic challenge, due to the difficulty of a simpletest to assess clonality. The inclusion of the TCRB1 antibody in the lymphoproliferative panelincreased the specificity of the test for diagnosis, being a method of rapid execution and lowcost. Another advantage of using this marker is the possibility of evaluating small cell clonesthat may not be detected in molecular biology techniques due to the sensitivity of the test.