Evaluation of Lymphocyte Immunity in Patients Treated with Venetoclax-Azacitidine for Acute Myeloid Leukemia
Authors: Kanaya Minoru , Suzuki Toma , Kajikawa Sayaka , Yokoyama Emi , Izumiyama Koh , Saito Makoto , Morioka Masanobu , Mori Akio , Matsukawa Toshihiro , Onozawa Masahiro , Teshima Takanori , Kondo Takeshi 
Published: December 2024

Background: The Venetoclax-Azacitidine (Ven-Aza) regimen has shown superior overall survival compared to azacitidine monotherapy (Aza) in unfit or elderly acute myeloid leukemia (AML) patients, which was demonstrated in the VIALE-A study (DiNardo CD, et al. N Engl J Med. 2020). Ven-Aza regimen is associated with serious neutropenia, a risk factor for bacterial and fungal infection. In contrast to neutropenia, the impact of Ven-Aza on lymphocyte immunity, which is crucial for protection against viral infections, has not been extensively addressed in the previous literature. Regarding T-cell immunity, Aza is known to improve T-cell repertoire and increase CD4+ and CD8+ T-cell frequencies in peripheral blood (Fozza C, et al. Leuk Res. 2015). And Ven increases T-cell effector function without inducing T-cell apoptosis in vitro (Lee JB, et al. Blood. 2021). However, the impact of Ven-Aza on T/B lymphocyte and humoral immunity in the real-world setting remains poorly elucidated.

Methods: To assess the effect of Ven-Aza on lymphocyte immunity, we retrospectively collected clinical data on lymphocyte numbers and lymphocyte flow cytometry analysis for peripheral blood, including T cell numbers (CD3+ cells/μL), CD4/8 ratio, B-cell numbers (CD19+ cells/ μL), and serum IgG levels (mg/dL) from peripheral blood of patients treated with Ven-Aza regimen, Aza monotherapy, and other regimens including 7+3 induction for AML or myelodysplastic syndrome (MDS) at Aiiku Hospital. Statistical tests were performed to compare three groups with non-parametric One-Way ANOVA (Kruskal-Wallis test) followed by multiple comparison tests. Analyses were performed using GraphPad Prism software. Informed consent was obtained using the opt-out method. The protocol was approved by the institutional review boards of Aiiku Hospital was conducted by the Declaration of Helsinki.

Results: We collected data from 27 Japanese patients with AML and MDS (AML n=20, APL n=3 and MDS n=4) . Ten patients received Ven-Aza (AML n=10) and 9 patients received Aza monotherapy (AML n=5 and MDS n=4), and 8 patients was administrated other regimens (AML n=5 and APL n=3) including IDA+Ara-C (n=2), CAG (Low dose Ara-C + aclarubicin + G-CSF, n=2), giltertinib (n=1) and ATRA+ATO (n=3). All peripheral blood samples were collected at the timing before starting treatment. The median age of all patients was 73 (63 - 91) years old and the median cycle for analyzing the evaluation of lymphocyte was cycle 8 in Ven-Aza and cycle 4 in Aza monotherapy.

Mean CD3 numbers (/μL), CD4 numbers (/μL), CD19 numbers (/μL), CD4/8 ratio, and serum IgG levels (mg/dL) were 515.0/μL, 271.0/μL, 8.3/μL, 1.0, and 1294 mg/dL in the Ven-Aza. In the Aza monotherapy, 520.6/μL, 340.6/μL, 37.1/μL, 1.7, and 1105 mg/dL and 914.9/μL, 591.5/μL, 65.2/μL, 1.7, and 1279 mg/dL in other regimens, respectively. CD3 numbers and CD4 numbers were significantly lower in the Ven-Aza than in the other regimens (p = 0.014 and p = 0.007, respectively). Notably, the CD19 numbers of Ven-Aza was much lower than Aza monotherapy and other regimens (p = 0.01 and p = 0.01, respectively). Despite the difference in CD19 numbers, serum IgG levels were comparable between the three groups.

Conclusions: Our findings, which peripheral CD4+ T cell numbers were significantly fewer in Ven-Aza than in other regimens including 7+3 suggest that CD4+ T cell immunity may be impaired in patients who administrated Ven-Aza regimen. This observation raises concerns regarding the potential risk of viral infections associated with Ven-Aza, which CD4+ T cell immunity has critical roles to protect for. In terms of B-cell immunity, we found serum immunoglobulin level remains unaffected by Ven-Aza despite severe peripheral CD19+ B cell reduction. This finding seems to be fascinating because distinct observation was seen between Ven-Aza and anti-CD20 monoclonal antibody/CD19 CAR-T cell therapy which affected not only B-cell number but also serum immunoglobulin. Given the limitations of this retrospective and small single-center study, further prospective studies with larger cohorts are needed to elucidate the impact of Ven-Aza on CD4+ T cell function and immune phenotype. The mechanism by which serum immunoglobulin level is intact despite severe B-cell reduction could be revealed as well in the larger and more detailed study.