Interleukin-3 receptor α chain (CD123) is preferentially expressed in immature T-ALL and may not associate with outcomes of chemotherapy

The role of chemokines and interleukins in acute lymphoblastic leukemia: a systematic review

Acute lymphoblastic leukemia (ALL) is the most common childhood hematological malignancy, but it also affects adult patients with worse prognosis and outcomes. Leukemic cells benefit from protective mechanisms, which are mediated by intercellular signaling molecules - cytokines. Through these signals, cytokines modulate the biology of leukemic cells and their surroundings, enhancing the proliferation, survival, and chemoresistance of the disease. This ultimately leads to disease progression, refractoriness, and relapse, decreasing the chances of curability and overall survival of the patients. Targeting and modulating these pathological processes without affecting the healthy physiology is desirable, offering more possibilities for the treatment of ALL patients, which still remains unsatisfactory in certain cases. In this review, we comprehensively analyze the existing literature and ongoing trials regarding the role of chemokines and interleukins in the biology of ALL. Focusing on the functional pathways, genetic background, and critical checkpoints, we constructed a summary of molecules that are promising for prognostic stratification and mainly therapeutic use. Targeted therapy, including chemokine and interleukin pathways, is a new and promising approach to the treatment of cancer. With the expansion of our knowledge, we are able to uncover a spectrum of new potential checkpoints in order to modulate the disease biology. Several cytokine-related targets are advancing toward clinical application, offering the hope of higher disease response rates to treatment.

Flotetuzumab as a salvage immunotherapy in advanced CD123-positive hematological malignancies, a phase 1 pilot study

CD123 "expression" is common in hematological malignancies, including acute lymphoblastic leukemia (ALL). Flotetuzumab is a novel, investigational CD3/CD123 DART®. We conducted a phase 1 study evaluating safety and efficacy of flotetuzumab in relapsed/refractory ALL (Cohort A) and other advanced CD123-positive hematological malignancies (excluding myeloid malignancies) (cohort B). Thirteen patients (9 in Cohort A and 4 in Cohort B) were treated at dose level 1 (500 ng/kg/day) before early closure due to discontinuation of drug development by sponsor. Two dose limiting toxicities (Grade 4 thrombocytopenia and neutropenia) occurred in one patient in Cohort B. Cytokine release syndrome occurred in most patients (85%), all being grade ≤2. Responses only occurred in Cohort B, with a partial response in one patient with Hodgkin's lymphoma and morphological complete remission in the bone marrow in one patient with blastic plasmacytoid dendritic cell neoplasm. In conclusion, flotetuzumab had a manageable safety profile in advanced CD123-positive hematological malignancies.

Targeting CD123 in hematologic malignancies: identifying suitable patients for targeted therapy

Following the observation of interleukin 3 receptor α chain (IL-3Rα; CD123) upregulation on leukemia stem cells (LSCs) almost two decades ago, targeted treatment via CD123-diptheria toxin conjugates has now been tested in patients with diverse myeloid malignancies. Targeted eradication of LSCs could result in effective treatments for many challenging diseases initiated by these cells. Consequently, considerable effort has been directed toward targeting CD123 as a potential strategy for treating patients with hematologic malignancies in which CD123 is overexpressed. However, these therapies have had limited success so far, highlighting the need for suitable criteria to identify patients who could benefit from them. Given the diversity in CD123 expression across different hematologic malignancies, understanding CD123 expression patterns and the functional pathogenetic significance is crucial. Here, we review the methodologies available for CD123 assessment and discuss the biological and clinical characteristics of patients for whom CD123-targeting therapies may have a clinical impact.

CD123: A Novel Biomarker for Diagnosis and Treatment of Leukemia

Leukemia is a group of progressive hematologic malignancies derived from stem cells in bone marrow which causes a large number of cancer deaths. Even with treatment such as traditional chemotherapy, targeted therapy, and allogeneic stem cell transplantation (allo-HSCT), many patients suffer from relapse/refractory disease, and the overall survival is dismal. Leukemic stem cells (LSCs) are induced by gene mutations and undergo an aberrant and poorly regulated proliferation process which is involved in the evolution, relapse, and drug-resistance of leukemia. Emerging studies demonstrate that CD123, the interleukin 3 receptor alpha (IL-3Rα), is highly expressed in LSCs, while not normal hematopoietic stem cells (HSCs), and associates with treatment response, minimal residual disease (MRD) detection and prognosis. Furthermore, CD123 is an important marker for the identification and targeting of LSCs for refractory or relapsed leukemia. Anti-CD123 target-therapies in pre-clinical studies and clinical trials confirm the utility of anti-CD123 neutralizing antibody-drugs, CD3×CD123 bispecific antibodies, dual-affinity retargeting (DART), and anti-CD123 chimeric antigen receptor-modified T-cell (CAR-T) therapies in progress. This review summarizes the most recent progress on the study of CD123 biology and the development of novel CD123-targeted therapies.

Targeting the alpha subunit of IL-3 receptor (CD123) in patients with acute leukemia

The IL-3 alpha chain receptor (CD123) is a cell surface protein that is widely expressed by various subtypes of acute leukemia, including acute myeloid leukemia (AML), acute lymphoblastic leukemia and blastic plasmacytoid dendritic cell neoplasm. Notably, CD123 is preferentially overexpressed in leukemia stem cells (LSC) in contrast to normal hematopoietic stem cells, and this differential expression allows for the selective eradication of LSC and leukemic blasts through therapeutic targeting of CD123, with less impact on hematopoietic cells. The level of CD123 expression in AML correlates with both treatment response and outcomes. Therefore, targeting CD123 represents a promising universal therapeutic target in advanced acute leukemias irrespective of the individual leukemia phenotype. There are currently 31 ongoing clinical trials examining the utility of CD123-based targeted therapies. Here we focus our review on current efforts to target CD123 in acute leukemia through various therapeutic constructs.

Early precursor T-cell acute lymphoblastic leukemia: current paradigms and evolving concepts

Early precursor T cell-acute lymphoblastic leukemia (ETP-ALL) is a rare entity characterized by chemo-resistance and a paucity of data regarding optimal management. We review here the literature regarding the management of ETP-ALL and focus on the recent, emerging data, regarding the potential role of molecularly targeted approaches with a focus on venetoclax.

Study on the Prognostic Value of Aberrant Antigen in Patients With Acute B Lymphocytic Leukemia

BACKGROUND

Approximately 30% to 60% of patients with acute B-lymphocytic leukemia (B-ALL) show as refractory or relapsed, which is one of the major causes of death in patients with B-ALL, but the methods of the treatment for relapsed/refractory B-ALL (R/R B-ALL) are limited. The chimeric antigen receptors redirected T cells (CAR-T cells) have showed a strong anti-leukemia role for B-ALL. About 90% of patients with R/R B-ALL treated with CD19-CAR-T cells achieved complete remission. However, 60% to 70% of patients relapsed after CAR-T cells treatment, which may be related to target antigen reduction or escape. New products are urgently needed to prevent and treat antigenic escapes causing recurrence.

PATIENTS AND METHODS

In this article, we retrospectively analyzed the immunophenotype of patients with B-ALL initially diagnosed in our center from January 2010 to December 2015 to determine whether aberrant antigen expression was associated with the prognosis of patients in order to find new targets for immunotherapy.

RESULTS

The results show that disease-free and overall survival in patients without aberrant antigen expression were better than patients with aberrant antigen expression. The most common abnormal antigens were CD123, CD13, and CD56. Correlation analysis showed a negative correlation between aberrant CD123 expression and both disease-free and overall survival.

CONCLUSION

Therefore, in the construction of CAR-T cells in patients with R/R B-ALL, conventional CD19 can be combined with aberrant antigens such as CD123 to form CARs with bi-specific antigens or multi-specific antigens may achieve the purpose of improving efficacy. However, more clinical trials are needed.

CD123 expression levels in 846 acute leukemia patients based on standardized immunophenotyping

BACKGROUND

While it is known that CD123 is normally strongly expressed on plasmacytoid dendritic cells and completely absent on nucleated red blood cells, detailed information regarding CD123 expression in acute leukemia is scarce and, if available, hard to compare due to different methodologies.

METHODS

CD123 expression was evaluated using standardized EuroFlow immunophenotyping in 139 pediatric AML, 316 adult AML, 193 pediatric BCP-ALL, 69 adult BCP-ALL, 101 pediatric T-ALL, and 28 adult T-ALL patients. Paired diagnosis-relapse samples were available for 57 AML and 19 BCP-ALL patients. Leukemic stem cell (LSC) data was available for 32 pediatric AML patients. CD123 expression was evaluated based on mean fluorescence intensity, median fluorescence intensity, and percentage CD123 positive cells.

RESULTS

EuroFlow panels were stable over time and between laboratories. CD123 was expressed in the majority of AML and BCP-ALL patients, but absent in most T-ALL patients. Within AML, CD123 expression was lower in erythroid/megakaryocytic leukemia, higher in NPM1 mutated and FLT3-ITD mutated leukemia, and comparable between LSC and leukemic blasts. Within BCP-ALL, CD123 expression was higher in patients with (high) hyperdiploid karyotypes and the BCR-ABL fusion gene. Interestingly, CD123 expression was increased in BCP-ALL relapses while highly variable in AML relapses (compared to CD123 expression at diagnosis).

CONCLUSIONS

Authors evaluated CD123 expression in a large cohort of acute leukemia patients, based on standardized and reproducible methodology. Our results may facilitate stratification of patients most likely to respond to CD123 targeted therapies and serve as reference for CD123 expression (in health and disease). © 2018 The Authors. Cytometry Part B: Clinical Cytometry published by Wiley Periodicals, Inc. on behalf of International Clinical Cytometry Society.

CD123 expression patterns and selective targeting with a CD123-targeted antibody-drug conjugate (IMGN632) in acute lymphoblastic leukemia

The potential of CD123-targeted therapies in acute lymphoblastic leukemia/lymphoma remains largely unexplored. We examined CD123 expression levels in a large cohort of patients with acute lymphoblastic leukemia/lymphoma and assessed the in vitro impact of IMGN632, a conjugate of CD123-binding antibody with a novel DNA-alkylating payload. CD123 expression on leukemic blasts was surveyed using multicolor/multiparameter flow cytometry. The in vitro effect of IMGN632 was evaluated on B acute lymphoblastic leukemia/lymphoma cell lines and primary B acute lymphoblastic leukemia/lymphoma blasts. The study cohort (n=213) included 183 patients with B acute lymphoblastic leukemia/lymphoma and 30 with T acute lymphoblastic leukemia/lymphoma. CD123 expression was more prevalent in B acute lymphoblastic leukemia/lymphoma than in T acute lymphoblastic leukemia/lymphoma (164/183, 89.6% versus 13/30, 43.3%; P<0.0001), and within B acute lymphoblastic leukemia/lymphoma CD123 expression was more prevalent in Philadelphia chromosome-positive patients than in Philadelphia chromosome-negative patients (96.6% versus 86.3%; P=0.033). In T acute lymphoblastic leukemia/lymphoma, 12/13 (92.3%) patients with CD123-positive blasts had either early T precursor (ETP) or early non-ETP immunophenotype. IMGN632 was highly cytotoxic to B acute lymphoblastic leukemia/lymphoma cell lines, with half maximal inhibitory concentrations (IC₅₀) between 0.6 and 20 pM. In five of eight patients' samples, low picomolar concentrations of IMGN632 eliminated more than 90% of the B acute lymphoblastic leukemia/lymphoma blast population, sparing normal lymphocytes. In conclusion, CD123 expression is prevalent across acute lymphoblastic leukemia/lymphoma subtypes, and the CD123-targeted antibody-drug conjugate IMGN632 demonstrates promising selective activity in preclinical models of B acute lymphoblastic leukemia/lymphoma.