186P - Unveil and overcome PD(L)1 antibody resistance via functional genomics and clinical derived biopsies

Background

Currently anti-PD(L)1 immunotherapy is widely used to treat microsatellite-instability-high (MSI-H) pan-cancers. However, part of MSI-H patients and more others with microsatellite stable (MSS) phenotype do not respond well to this immunotherapy, which means potential extra factors or signals have also participated in the complicated tumor microevironment.

Methods

1. In vivo Crispr screening: Commercial or house-made CRISPR library was transduced into target cancercell lines, e.g., A375, with MOI=0.1-0.3. Cells were transferred into PBMC humanized immune deficient mice then dosed with target drugs (e.g. Pembrolizumab, 10mg/kg I.V., 2 weeks). Tumors were collected at theendpoint for genomic DNA isolation, and gRNAabundance was analysed by deep-sequence. 2. Human conditional reprogrammed cell lines (CRs) reconstruction: The tumor bioposies, clinically resistant or sensitive to medicine, were processed, cultured with OncoVeeTM Conditional Reprogramming Cell Culture Kit, to generate stable celllines for in vivtro and in vivo functional assays.

Results

1. From in vivo genomic CRISPR screening assay, we have identified several key molecules contributing to immunotherapy resistance in cancer patients, including high expression of Tgfb1, CD73/NT5E, down-regulation of Jak1 signalling, as well as novel drivers/regulators, e.g., discoidin domain receptors, solute carrier family, V-set and transmembrane domain-containing proteins, Ig domain superfamily adhesion molecules. 2. We have successfully generated at least 3 PDL1+ CR cell lines, two non-small cell lung cancers and one melanoma, confimed its characteistics with PD1 antibody resistance by in vitro 2D and 3D pbmc/cancer coculture assays. 3. We have proved that novel antibodies (new ICB, Bs/TsAb, ADC, TCE) and chemical compounds mono- or combo- therapy could successfully overcome individual PD1 antibody immunotherapy resistance in vivo.

Conclusions

1. In vivo CIRPSR screening is a powerful tool to identify novel key cancer driver genes, susceptible genes in tumor development. 2. The clinical relavant condtional reprogrammed cancer cell lines (CRs) are becoming more and more useful to study the mechanism of action(MOA) of PD1 antibody resistance.

Legal entity responsible for the study

B. Xie.

Funding

Lide Biotech.

Disclosure

All authors have declared no conflicts of interest.