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Built on the RenLite® platform, BCG041 utilizes common light chain technology to eliminate heavy/light chain mispairing, ensure seamless assembly, simplify manufacturing, and provide a developable antibody backbone for the B7-H3 × MUC1 bispecific ADC drug development.
BCG041 is conjugated with Biocytogen's proprietary BLD1102 linker–payload system containing BCPT02 , a topoisomerase I (TOP1) inhibitor payload designed to drive potent ADC-mediated cytotoxicity in solid tumor drug development.
BCG041 is being evaluated as a B7-H3/MUC1-directed bispecific ADC drug development asset for solid tumors. Potential development areas include non-small cell lung cancer (NSCLC), small cell lung cancer (SCLC), esophageal cancer, gastric cancer, breast cancer, and head and neck cancers.
The preclinical data package supporting BCG041, generated from Biocytogen internal preclinical studies, includes synergistically enhanced binding, improved internalization, robust antitumor activity across multiple PDX models, and a favorable pharmacokinetic profile with excellent bloodstream stability and tumor accumulation. Together, these data support the development of BCG041 as a B7-H3 × MUC1 bispecific for heterogeneous solid tumors.
Figure 1. Antigen binding analysis of BCG041 in B7-H3/MUC1 dual-expressing tumor cells. Across HCC1954 breast cancer, DU4475 breast cancer, and NCI-H1650 lung cancer cells, BCG041 showed enhanced binding activity compared with parental monoclonal antibodies, monovalent antibody controls, and single-target benchmark analogs including DS-7300 (B7-H3 ADC), 1H7, and Gatipotuzumab (MUC1 ADC). These results demonstrate that BCG041 achieves synergistically enhanced tumor cell binding, supporting its bispecific design for improved tumor cell engagement and broader coverage in heterogeneous solid tumors.
Figure 2. Internalization kinetics of BCG041 in B7-H3/MUC1-expressing tumor cells. In the same cancer cell panel used for binding analysis, BCG041 demonstrated stronger internalization over time compared with parental monoclonal antibodies, monovalent antibody controls, and benchmark analogs including DS-7300, 1H7, and Gatipotuzumab analog. These data indicate that B7-H3 × MUC1 dual-target engagement translates into enhanced cellular uptake, supporting efficient intracellular delivery of the BCPT02 payload.
Figure 3. In vivo tumor growth and body weight analysis of BCG041-BCPT02 in multiple PDX models. BCG041-BCPT02 was evaluated after a single intravenous dose in BP0847 colorectal cancer, BP0508 lung cancer, and BP0818 breast cancer PDX models. Across the evaluated models, BCG041-BCPT02 demonstrated robust tumor growth inhibition compared with BCPT02-conjugated single-target ADC controls and benchmark ADC analogs. Body weight profiles remained comparable to control groups, with no body weight loss observed, supporting a favorable preliminary tolerability profile.
Figure 4. Pharmacokinetic (PK) profile of BCG041 in the BP0508 lung cancer PDX model. Following a single 6 mg/kg i.v. dose of BCG041-BCPT02, serum and tumor concentrations of total antibody (-TAb), intact ADC (-ADC), and released payload (-BCPT02) were measured over time. Serum TAb and ADC showed comparable exposure, while released BCPT02 remained minimal, supporting bloodstream stability and limited premature payload release. In tumor tissue, delayed Tmax and higher BCPT02 exposure relative to serum supported tumor accumulation and localized payload exposure.
Biocytogen welcomes partnership discussions to further evaluate this B7-H3 × MUC1 bispecific ADC asset.
BCG041 leverages the cooperative co-expression topology of B7-H3 and MUC1 as a dual-anchor framework to counteract antigen heterogeneity and clonal evasion, ensuring tumor engagement despite single-antigen dynamics. Crucially, while conventional MUC1 ADCs are constrained by systemic clearance via the circulating antigen "sink effect," BCG041 selectively engages the membrane-proximal stalk of MUC1 to bypass decoy binding by shed fragments, guaranteeing efficient internalization and uncompromised payload delivery within the tumor microenvironment (TME).
BCG041 is built on Biocytogen's proprietary RenLite® platform. It utilizes a fully human IgG1κ common-light-chain backbone that delivers high binding affinity and strong developability. This advanced engineering minimizes the risk of chain mispairing, supporting efficient and scalable CMC manufacturing for clinical development of a differentiated B7-H3 × MUC1 bispecific ADC candidate.
BCG041 features an optimized, protease-cleavable hydrophilic linker conjugated to BCPT02—a potent topoisomerase I inhibitor—with a high drug-to-antibody ratio (DAR) of approximately 8. Engaging two targets simultaneously promotes faster internalization, widening the therapeutic window. Notably, in preclinical cachectic breast cancer models, BCG041 delivered superior antitumor efficacy while promoting unique body weight recovery in diseased mice, supporting a preliminary tolerability profile compared with benchmark ADC analogs.
Because B7-H3 and MUC1 are widely co-expressed across a multitude of high-prevalence solid tumors, BCG041 is designed for a massive global patient population. Key targeted indications include breast, lung, colorectal, prostate, esophageal, gastric, head and neck, and metastatic ovarian cancers.
