Rejuvenating hepatic tumor microenvironment immunity with a phosphatidylserine-targeting small molecule drug conjugate

Abstract

We report the design, synthesis and evaluation of a class of phosphatidylserine-targeting zinc (II) dipicolylamine drug conjugates and show that conjugate 16b elicits immune cell infiltration and remodels the "cold" hepatic tumor microenvironment to the inflamed "hot" tumor. Structure-property relationship study via linker modifications and subsequent pharmacokinetics profiling were carried out to improve the solubility and stability of the conjugates in vivo. In a spontaneous hepatocellular carcinoma mouse model, we showed that conjugate 16b exhibited better antitumor efficacy than sorafenib. In particular, significant increase of CD8⁺ T cell infiltration and granzyme B level was observed, providing insights in sensitizing tumors from intrinsic immune suppressive microenvironment. Evaluation of tumor inflammation-related mRNA expression profile revealed that conjugate 16b, through inductions of key gene expressions including STAT1, CXCL9, CCL5, and PD-L1, rejuvenated tumor microenvironment with enhancement in T cell-, macrophage-, NK cell-, chemokines and cytokines'- functions. Our study establishes that an apoptosis-targeting theranostic enables enrichment of multifaceted immune cells into the tumor mass, which provides potential therapeutic strategies in the combination with immune checkpoint blockade treatment.

Keywords: Inflammed tumor microenvironment; Phosphatidylserine; Small molecule drug conjugates; Zinc dipicolylamine.