Targeting the Phosphatidylserine-Immune Checkpoint with a Small-Molecule Maytansinoid Conjugate

Area of Science:

• Oncology
• Pharmacology
• Immunology

Background:

• Ligand-targeting drug delivery systems are advancing precision medicine.
• Immune checkpoint inhibitors are a cornerstone of modern cancer therapy.
• Developing novel targeted therapies remains crucial for overcoming treatment resistance.

Purpose of the Study:

• To develop and evaluate novel small molecule-based immune checkpoint-targeting maytansinoid conjugates.
• To assess the efficacy of these conjugates against pancreatic, triple-negative breast, and sorafenib-resistant liver cancers.
• To investigate the impact of the conjugate on the tumor microenvironment.

Main Methods:

• Synthesis and characterization of small molecule-based maytansinoid conjugates.
• Pharmacokinetic profiling and *in vivo* efficacy studies in relevant cancer models.
• Quantitative mRNA analysis of tumor tissues to assess immune microenvironment modulation.

Main Results:

• Conjugate 40a demonstrated significant *in vivo* anti-cancer efficacy in pancreatic, triple-negative breast, and liver cancer models.
• Conjugate 40a induced lasting tumor growth regression.
• Treatment with conjugate 40a successfully rejuvenated the immunosuppressive tumor microenvironment into an "inflamed hot tumor" phenotype, evidenced by elevated gene expression.

Conclusions:

• Small molecule-based immune checkpoint-targeting maytansinoid conjugates represent a promising new class of anti-cancer agents.
• Conjugate 40a offers a novel pharmacodelivery strategy with potential for combination therapy.
• This approach can enhance existing immune-oncology treatments by overcoming tumor immunosuppression.