Histone deacetylases inhibitor chidamide synergizes with humanized PD1 antibody to enhance T-cell chemokine expression and augment Ifn-γ response in NK-T cell lymphoma

Background: Whether immunotherapy combined with different histone deacetylases (HDAC) inhibitors in refractory or relapsed natural killer/T-cell lymphoma (NKTCL) is superior to each agent is still lacking in head-to-head clinical trials or preclinical evidence.

Methods: NKTCL cell line xenograft models (CDX) in immunocompetent, human programmed cell death protein 1 (PD1) knock-in genetically engineered mice were used to investigate the combination effects. Different types and dosages of HDAC inhibitors were investigated. We explored the underlying mechanisms by RNA-sequencing and ChIP-sequencing. Two clinical cases treated with anti-PD1/chidamide were presented.

Findings: Anti-PD1/chidamide shows significant tumour rejection in two CDX models. RNA-seq and CHIP-seq revealed that chidamide is synergistic to enhance T-cell chemokine expression, augment the IFN-γ response, and increase CD8 T-cell infiltration via histone modification. IFN-γ neutralizing antibody can attenuate the efficacy of combination drugs. However, the anti-PD1/romidepsin failed to augment the IFN-γ response. The expressions of IFN-γ related gene set signatures are significantly correlated with tumour rejection in anti-PD1/chidamide. In the clinic, two NKTCL patients treated with the PD1/chidamide show promising efficacy and limited toxicity.

Interpretation: Anti-PD1/chidamide enhances T-cell chemokine expression and augments the IFN-γ response in preclinical NKTCL immunocompetent models. IFN-γ signatures may be good response biomarkers for the selection of potentially benefit patients.

Funding: This study was supported by the Chinese National Major Project for New Drug Innovation (2017ZX09304015) and the Chinese Society of Clinical Oncology Research Fund (Y-BMS2019-026).