一、Introduction

CD276 (B7‑H3) is a transmembrane immune‑checkpoint protein of the B7 family. It accumulates heavily on cell surfaces of lung cancer, breast cancer, glioma, pancreatic cancer and many other malignancies. Most healthy tissues barely express this molecule. High CD276 levels usually correspond to poor patient prognosis ^[1].

CD276 dampens anti‑tumour responses from T cells and NK cells and helps tumours escape immune surveillance. It also drives tumour proliferation, invasion, metastasis, angiogenesis and drug resistance. It carries both immune‑regulatory and non‑immune oncogenic functions ^[2].

Monoclonal antibodies are the mainstream choice for drug development against CD276. Such antibodies block inhibitory signalling and trigger ADCC effects to eliminate tumour cells. Still, CD276‑targeted antibody development faces multiple obstacles. Its physiological receptor remains unclear. Antigen glycosylation creates interference, and tumour heterogeneity brings extra challenges.

二、Technical Principles and Experimental Workflow

CD276 overexpresses on tumour cell surfaces. It suppresses T‑cell and NK‑cell activity and pushes macrophages toward the M2‑polarized state. An immune‑suppressive microenvironment forms to favour tumour immune escape. It also accelerates tumour growth, migration and drug‑resistant phenotypes.

Anti‑CD276 monoclonal antibodies shut down these inhibitory immune signals and restore host anti‑tumour immunity. Their Fc domains mediate ADCC effects to clear tumour cells. These antibodies also serve as backbones for engineering ADCs, bispecific antibodies and other novel therapeutics ^[1,3].

Standard development workflow for CD276‑targeted monoclonal antibodies:

1. Antigen preparation

Construct expression vectors for CD276 extracellular domain. Express and purify recombinant protein to obtain antigen with near‑native conformation.

2. Animal immunization or library screening

Generate candidate antibody clones via animal immunization combined with single‑B‑cell technology, or perform screening from phage‑display libraries.

3. Primary and secondary screening

Run ELISA and flow‑cytometry assays. Pick monoclonal antibodies that bind both purified CD276 antigen and CD276‑positive tumour cells.

4. Molecular engineering

Carry out humanization and Fc‑domain modification. Improve antibody affinity and effector functions.

5. Functional validation

Test antibody blocking activity and ADCC killing potency. Evaluate therapeutic effects through cell‑level assays and in‑vivo animal models.

三、Technical Advantages and Existing Difficulties

1.Merits of CD276 as a tumour target

①CD276 rises in a wide range of solid tumours but shows limited expression in normal tissues. Anti‑CD276 monoclonal antibodies achieve a favourable therapeutic window and apply to multiple tumour types.

②CD276 expression operates independently from PD‑L1. It remains a valid target for tumours resistant to PD‑1/PD‑L1 inhibitors and complements existing immunotherapy regimens.

③Starting from monoclonal antibodies, researchers can flexibly generate ADCs, bispecific antibodies, CAR‑T and other drug formats. Multiple developmental paths become available.

④CD276 expression measured in tissue samples works as a prognostic biomarker. It supports patient stratification for treatment selection.

2.Major technical difficulties

①The complete physiological receptor for CD276 has not been fully identified. Mechanism studies of monoclonal antibodies meet obstacles, and blocking activity cannot be assessed precisely [4].

②CD276 receives heavy glycosylation modifications. Sugar chains shield key epitopes. Screening may yield non‑functional antibodies that only recognize glycan moieties.

③Tumour heterogeneity is prominent. CD276 distribution varies within one tumour mass. Some tumour sub‑populations carry no CD276 expression. Monoclonal‑antibody monotherapy easily induces drug resistance.

四、Main Application Scenarios

1. Therapeutic monoclonal antibodies and derivative drug development

Fc‑optimized anti‑CD276 monoclonal antibodies enhance ADCC potency for solid‑tumour treatment. Antibodies can be built into ADC agents for targeted toxin delivery. Multiple CD276‑based ADC candidates advance into clinical studies and show encouraging results in small‑cell lung cancer and triple‑negative breast cancer.

2. Bispecific antibodies and cell therapy

CD276‑targeted bispecific antibodies bridge tumour cells and T cells to redirect immune‑mediated killing. CD276‑directed CAR‑T constructs are tested in pre‑clinical solid‑tumour research and expand available therapeutic options.

3. Diagnosis and biomarker detection

Anti‑CD276 monoclonal antibodies support IHC and immunofluorescence assays. Researchers measure CD276 abundance in tumour tissues for patient stratification and guide targeted‑drug administration. They can also be made into PET imaging probes for in‑vivo tumour diagnosis.

4. Basic mechanism research

Recombinant CD276 antigen and matching monoclonal‑antibody tools support studies on tumour immune escape, metastasis and drug resistance. They help map upstream and downstream regulatory pathways and lay theoretical foundations for new‑drug development.

五、Relevant Technical Services from KMD‑Bioscience

1. Antigen preparation

Express and purify recombinant CD276 extracellular‑domain protein. Deliver high‑purity antigen close to native conformation for immunization, screening and detection purposes.

2. Monoclonal‑antibody screening

Deploy multiple technical routes including rabbit single‑B‑cell workflow, hybridoma technology and phage display. Isolate specific monoclonal antibodies targeting CD276.

3. Antibody molecular engineering

Complete antibody sequencing, humanization and Fc‑region modification. Optimize binding affinity and effector performance.

4. Multi‑dimensional functional validation

Confirm binding activity by ELISA and flow cytometry. Perform ADCC functional assays and IHC tests. Carry out cell‑level pharmacodynamic evaluation.

5. Sample delivery

Hand over recombinant antigen, antibody plasmids, purified monoclonal antibodies and complete experimental reports. Support follow‑up engineering of ADC and bispecific‑antibody molecules.

FAQs

Q：Several monoclonal antibodies show binding signals against recombinant CD276 protein, yet almost no binding appears in flow‑cytometry tests using CD276‑positive tumour cells. What are the main causes？

1. CD276 carries extensive glycosylation. The isolated antibodies recognize glycan structures on recombinant protein rather than peptide‑based epitopes of the protein itself. Glycosylation patterns differ on tumour‑cell surfaces and eliminate cell‑binding signals.

2. Recombinant antigen only contains extracellular‑domain fragments. Its spatial conformation diverges from native CD276 presented on cell membranes. Antibodies target epitopes unique to recombinant material.

3. CD276 expression level stays low on tumour‑cell surfaces and falls below assay detection limits.

4. Buffer‑solution conditions interfere antigen‑antibody interaction.

[1]Guo Y, Wang X, Zhang C, et al. Tumor Immunotherapy Targeting B7-H3: From Mechanisms to Clinical Applications. Immunotargets Ther. 2025;14:291-320. Published 2025 Mar 27. doi:10.2147/ITT.S507522

[2]Getu AA, Tigabu A, Zhou M, Lu J, Fodstad Ø, Tan M. New frontiers in immune checkpoint B7-H3 (CD276) research and drug development. Mol Cancer. 2023;22(1):43. Published 2023 Mar 2. doi:10.1186/s12943-023-01751-9

[3]Lutz MS, Wang K, Jung G, Salih HR, Hagelstein I. An Fc-modified monoclonal antibody as novel treatment option for pancreatic cancer. Front Immunol. 2024;15:1343929. Published 2024 Jan 22. doi:10.3389/fimmu.2024.1343929

[4]Jansen L, Wienke J, Molkenbur R, Rossig C, Meissner R. B7-H3 in the tumor microenvironment: Implications for CAR T cell therapy in pediatric solid tumors. Cancer Metastasis Rev. 2025;44(4):77. Published 2025 Oct 11. doi:10.1007/s10555-025-10294-y