CTLA4-CD80 Immune Checkpoint Biochemical Assay

Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), also known as CD152, is a key regulator of T-cell immunity by maintaining activation and inhibition of T-cell immune responses. CTLA4 and CD28 are co-stimulatory and co-inhibitory cell surface signaling proteins that interact with the same ligands (CD80 and CD86), with CTLA4 displaying a greater affinity than CD28 for both, thus creating effective ligand binding competition. Studies have shown that functional blockage of CTL4 by anti-CTL4 binding by biologics and small molecules with high affinity results in enhanced T cell responses, ultimately resulting in more effective immune responses targeting many cancers.

Target Overview


To provide a screening assay for identifying small and large molecule CTLA-4 and CD80 binding interaction blockage inhibitors, with the goal of eventually studying immune responses to aid in the discovery of novel immunotherapies to combat cancer.




CTLA4: Cytotoxic T-lymphocyte protein 4, CD152
CD80: T-lymphocyte activation antigen CD80, Activation B7-1 antigen, BB1, CTLA-4 counter-receptor B7.1 (B7)

Scientific Information

P16410 (https://www.uniprot.org/uniprotkb/P16410)
P33681 (https://www.uniprot.org/uniprotkb/P33681)

Assay Properties


HTRF Assay


Human CTLA4, human CD80

Reference Compound IC50s
Compounds IC50 (nM)
Ipilimumab 1.55

Screening Location

Malvern, PA, USA

Further Information

More information can be found on our website Immune Checkpoint Assays

Reference compound inhibition of CTLA4-CD80

Reference compound inhibition of CTLA4-CD80

Sample data showing reference compound inhibition of CTLA4-CD80 binding interaction