Discovery of Novel Small-Molecule Immunomodulators for Cancer Immunotherapy Using OB2C Technology

Background/Objective: Immunomodulators play a critical role in regulating immune responses, with immunostimulatory agents enhancing cancer therapy by activating immune cells such as T cells. While immune checkpoint inhibitors (ICIs) targeting PD-1 and CTLA-4 have shown clinical success, the availability of small-molecule immunomodulators remains limited. This study aimed to identify novel small-molecule immunomodulators using the One-Bead-Two-Compound (OB2C) library approach for potential cancer immunotherapy. Methods: A OB2C library consisting of 1,764 compounds was screened to identify small-molecule immunomodulators capable of enhancing immune responses. The bead library was incubated with Jurkat cells, which express high levels of α4β1 integrin, each and every compound-bead was uniformly covered with cells. IFN-γ production was measured as a marker of immune activation. The most potent compound was further evaluated for its effects on PBMC activation and cytolytic activity against prostate cancer cells. Tumor cell viability assays were performed to evaluate its effect on immune-mediated tumor suppression. Results: Two immunomodulators, Kib-IM-1 and Kib-IM-4, were identified from a 1764-compound OB2C library. However, only Kib-IM-4 was confirmed to induce PBMC clustering and significantly enhance IFN-γ production. In addition, Kib-IM-4 promoted immune cell activation and enhanced the cytolytic activity of PBMCs against prostate cancer cells, leading to a reduction in tumor cell viability. Conclusions: These findings highlighted Kib-IM-4’s potential as a novel small-molecule immunomodulator for cancer immunotherapy. By enhancing immune cell activation and promoting tumor cell cytolysis, Kib-IM-4 represents a promising candidate for further development in cancer treatment.