Yantai, April 29, 2025 – Boan Biotech presented the early research findings about its BA1106, a non-IL-2 blocking anti-CD25 antibody, at the 2025 Annual Meeting of the American Association for Cancer Research (AACR). The innovative antibody is the first of its kind in China to undergo a clinical trial for the treatment of solid tumors. The trial is underway.
Regulatory T cells (Tregs) drive immunosuppression in the tumor microenvironment by inhibiting the antitumor effects of various immune cells, such as T cells. Tregs are present in a wide range of malignancies, including cervical cancer, renal cancer, ovarian cancer, melanoma, pancreatic cancer, hepatocellular cancer, gastric cancer, and breast cancer, etc. The elevated level of Tregs is associated with poor survival.
CD25, also known as interleukin-2 receptor alpha (IL-2Rα), is highly expressed in Tregs, making it a high-potential target for a broad spectrum of antitumor immunotherapies. Antibodies targeting CD25 can delete Tregs and enhance anti-tumor activity of T cells. However, developing anti-CD25 antibodies faces two major challenges. The first is that CD25 is also expressed at low levels in Effector T cells (Teffs), so anti-CD25 antibodies with high activities may delete Teffs unspecifically while targeting Tregs. The second is that anti-CD25 antibodies tend to block IL-2 signaling, thereby suppressing the antitumor activity of T cells.
BA1106 is able to overcome both challenges thanks to molecular engineering design. In vitro activity assays show that BA1106 has a “moderate” antibody-dependent cellular cytotoxicity (ADCC): it can effectively deplete Tregs in which CD25 is highly expressed to relieve immunosuppression while sparing Teffs with a relative low CD25 expression. In this process, BA1106 does not interfere with the IL-2 signaling pathway, to ensure the functioning of Teffs in immune responses.
The findings presented at this year’s annual meeting of AACR are the early results from a multicenter, open-label, first-in-human Phase I clinical trial. As of the trial’s data cutoff, 31 patients with relapsed or refractory advanced solid tumors have received at least one dose of BA1106. The early results are as follows:
BA1106 has the potential for treating multiple types of solid tumors. In the 31 patients who had progressed following prior systemic treatments, including immunotherapies, BA1106 induced tumor shrinkage and durable disease stabilization across multiple tumor types. Patients who were the earliest to receive BA1106 have been treated for over one year.
BA1106’s pharmacodynamic (PD) profile matches its intended mechanism of action. Peripheral Tregs were selectively depleted, the effector-to-regulatory T-cell ratio increased markedly, and no Teff-depletion was observed, underscoring a favorable PD profile.
BA1106 is safe and tolerable. Maximum tolerated dose (MTD) was not reached and no any treatment-related serious adverse event (SAE) was reported up to the highest tested dose of 1.2 mg/kg. The overall incidences of SAE, treatment-related adverse events (TRAE), and skin toxicity were low for BA1106, consistent with the candidate’s moderate Treg-depletion activity.
BA1106 demonstrated a good pharmacokinetics (PK) profile with low immunogenicity, and its anti-drug antibody (ADA) detections were uniformly negative.
In addition, preclinical studies have shown that BA1106 is potent against both early-stage and late-stage tumors and functions well when used in combination with a PD-1 inhibitor. These results have been published in Scientific Reports, a journal of the Nature Portfolio .
Dr. Changlin Dou, R&D President and Chief Operating Officer at Boan Biotech, said: “Tregs suppress antitumor immune responses, contributing to a poor prognosis in many solid tumors. Therefore, Treg-depletion has been an attractive strategy for cancer immunotherapy. Available research data shows that BA1106 can eliminate Tregs without impairing Teffs. In our monotherapy Phase I trial, BA1106 demonstrated preliminary efficacy and the potential to treat a broad range of solid malignancies, which should be attributed to its moderate Treg-cytotoxicity conferred by a unique antibody design. In addition, a clinical trial has been approved to evaluate BA1106 used in combination with a PD-1 inhibitor (BA1104, nivolumab) for treating certain solid tumors in both immunotherapy-resistant and treatment-naïve patient cohorts, which will further expand its therapeutic promise.”
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