Skip to main content
An official website of the United States government
Government Funding Lapse
Because of a lapse in government funding, the information on this website may not be up to date, transactions submitted via the website may not be processed, and the agency may not be able to respond to inquiries until appropriations are enacted.

The NIH Clinical Center (the research hospital of NIH) is open. For more details about its operating status, please visit cc.nih.gov.

Updates regarding government operating status and resumption of normal operations can be found at opm.gov.

anti-PD-1/CTLA-4 bispecific antibody SI-B003

A bispecific antibody directed against the human negative immunoregulatory checkpoint receptors programmed cell death protein 1 (PD-1; PDCD1; CD279) and cytotoxic T-lymphocyte-associated antigen 4 (CTLA4; CTLA-4), with potential immune checkpoint inhibitory and antineoplastic activities. Upon administration, anti-PD1/CTLA-4 bispecific antibody SI-B003 targets and binds to both PD-1 and CTLA4 expressed on tumor-infiltrating T lymphocytes (TILs), and inhibits the PD-1- and CTLA4-mediated downregulation of T-cell activation and proliferation. This restores immune function and activates a sustained cytotoxic T-lymphocyte (CTL)-mediated immune response against tumor cells. Both PD-1 and CTLA4 are selectively expressed on TILs in the tumor microenvironment (TME) and negatively regulate the activation and effector functions of T cells. They play key roles in the downregulation of the immune system and tumor evasion from host immunity. Dual checkpoint blockade of PD1 and CTLA4 with SI-B003 may enhance T-cell activation and proliferation more than the blockade of either immune checkpoint receptor alone.
Synonym:anti-PD-1/anti-CTLA-4 bispecific antibody SI-B003
PD-1 x CTLA-4 bispecific antibody SI-B003
Code name:SI B003
SI-B003
SIB003
Search NCI's Drug Dictionary