Related Experiment Video
Updated: Oct 12, 2025
In Vitro Methods for Comparing Target Binding and CDC Induction Between Therapeutic Antibodies: Applications in Biosimilarity Analysis
Published on: May 4, 2017
Two novel human anti-CD25 antibodies with antitumor activity inversely related to their affinity and in vitro
Deyong Song1, Xiu Liu1, Chuangchuang Dong1
1Antibody Research and Development Center, Shandong Boan Biotechnology Co., Ltd., Yantai, 264670, People's Republic of China.
Abstract:
High tumor regulatory T (Treg) cell infiltration is associated with poor prognosis of many cancers. CD25 is highly expressed on tumor Treg cells and is a potential target for Treg deletion. Previously characterized anti-CD25 antibodies appear to have limited efficacy in tumor inhibition. Here we identified two human anti-CD25 antibodies, BA9 and BT942, which did not prevent the activation of IL-2R signaling pathway by IL-2. BT942 had weaker binding and cytotoxic activity to human CD25-expressing cell lines than BA9. But both demonstrated significant tumor growth inhibition in early and late-stage animal cancer models. BT942 resulted in a higher expansion of CD8+ T cells and CD4+ T cells in tumor microenvironment in mouse MC38 model compared to BA9. BT942 also demonstrated significant higher tumor growth inhibition and higher expansion of CD8+ T cells and CD4+ T cells in combination with an anti-PD1 antibody. Pharmacokinetic study of BT942 in cynomolgus monkeys demonstrated a half-life of 206.97 ± 19.03 h. Structural analysis by cryo-EM revealed that BT942 recognizes an epitope on opposite side of the CD25-IL-2 binding site, consistent with no IL-2 signaling blockade in vitro. BT942 appears to be an excellent candidate for cancer immunotherapy.
Insights
New anti-CD25 antibodies, BA9 and BT942, show promise in cancer immunotherapy. BT942 demonstrates significant tumor growth inhibition and enhances T cell activity, especially when combined with anti-PD1 therapy.
Area of Science:
- Immunology
- Oncology
- Structural Biology
Background:
- High tumor regulatory T (Treg) cell infiltration correlates with poor cancer prognosis.
- CD25 is a potential therapeutic target on tumor Treg cells, but existing anti-CD25 antibodies have shown limited efficacy.
- Understanding the mechanism of anti-CD25 antibodies is crucial for developing effective cancer immunotherapies.
Purpose of the Study:
- To identify and characterize novel human anti-CD25 antibodies for cancer immunotherapy.
- To evaluate the efficacy of BA9 and BT942 in preclinical cancer models.
- To elucidate the mechanism of action and pharmacokinetic properties of BT942.
Main Methods:
- Identification and characterization of two human anti-CD25 antibodies, BA9 and BT942.
- In vitro assessment of IL-2R signaling pathway activation and cytotoxic activity.
- In vivo evaluation of tumor growth inhibition in animal cancer models.
- Analysis of T cell populations within the tumor microenvironment.
- Combination therapy studies with anti-PD1 antibody.
- Pharmacokinetic studies in non-human primates.
- Cryo-electron microscopy for structural analysis.
Main Results:
- Both BA9 and BT942 did not block IL-2 signaling but demonstrated significant tumor growth inhibition.
- BT942 showed weaker binding and cytotoxic activity than BA9 in vitro.
- BT942 led to greater expansion of CD8+ and CD4+ T cells in the tumor microenvironment.
- BT942 combined with anti-PD1 antibody yielded superior tumor growth inhibition and T cell expansion.
- BT942 exhibited a long half-life (206.97 ± 19.03 h) in cynomolgus monkeys.
- Cryo-EM revealed BT942 binds an epitope distinct from the IL-2 binding site on CD25.
Conclusions:
- BT942 is a promising candidate for cancer immunotherapy due to its ability to inhibit tumor growth and enhance T cell responses without blocking IL-2 signaling.
- The distinct binding epitope of BT942 contributes to its unique mechanism of action.
- BT942 demonstrates potential for combination therapy, particularly with checkpoint inhibitors like anti-PD1.
