Researchers Develop Small Molecule Drug Targeting ILT3 to Enhance Cancer Immunotherapy
Researchers have discovered a small molecule compound, ICB-7, that binds and modulates ILT3 (LILRB4), a myeloid immune checkpoint that helps tumors evade the immune system. ILT3 is expressed on suppressive immune cells within the tumor microenvironment and has been linked to resistance to existing immunotherapies, but had not previously been targeted by small molecules. If validated in further studies, this approach could expand the toolkit for cancer immunotherapy beyond current antibody-based checkpoint inhibitors.
A team of researchers has reported the discovery of ICB-7, a small molecule that directly binds and inhibits ILT3 (also known as LILRB4), an immune checkpoint receptor found on suppressive myeloid cells in the tumor microenvironment. The compound was identified by screening an 8,961-member chemical library using a biophysical platform called Dianthus TRIC, and its binding was confirmed through microscale thermophoresis and cellular thermal shift assays. Molecular modeling studies located a stable binding pocket in the D2 domain of ILT3, and functional experiments showed ICB-7 disrupts the ILT3-SCG2 protein interaction while suppressing downstream signaling through SHP1, SHP2, and STAT3. In laboratory co-culture models using patient-derived colorectal cancer and acute myeloid leukemia cells, ICB-7 enhanced cytotoxic T-cell killing and reduced tumor cell viability. The compound also showed favorable pharmacokinetic and safety profiles and demonstrated anti-tumor efficacy in a mouse syngeneic colorectal cancer model. The study positions ILT3 as a viable small-molecule drug target and suggests that pharmacologically reprogramming suppressive myeloid immunity could complement or enhance existing immunotherapy strategies.
What's missing
As a preprint posted on bioRxiv, this study has not yet undergone formal peer review, and its findings should be interpreted with caution. The authors do not discuss whether ICB-7 has selectivity data against closely related LILRB family members (LILRB1, LILRB2, LILRB3, LILRB5), which could affect specificity and safety. All in vivo efficacy data come from a single mouse syngeneic tumor model (CT26), and no non-human primate or human clinical data exist yet.
What different sources said
- bioRxivCenter
Targeting the Myeloid Immune Checkpoint ILT3 (LILRB4) with Small Molecules Enables Reprogramming of Suppressive Tumor Immunity
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