Discovery of Macrocycle-Based HPK1 Inhibitors for T-Cell-Based Immunotherapy

Area of Science:

• Medicinal Chemistry
• Immunology
• Oncology

Background:

• Hematopoietic progenitor kinase 1 (HPK1) negatively regulates T-cell activation, making it a therapeutic target for enhancing antitumor immunity.
• Developing selective HPK1 inhibitors is challenging due to homology with GLK, a positive regulator of T-cell activation.

Purpose of the Study:

• To design and synthesize novel macrocycle-based HPK1 inhibitors using a conformational constraint strategy.
• To evaluate the inhibitory activity, selectivity, pharmacokinetic properties, and in vivo efficacy of the designed compounds.

Main Methods:

• Conformational constraint strategy was employed to design macrocycle-based HPK1 inhibitors.
• In vitro assays were used to determine HPK1 inhibition (IC50) and selectivity against GLK.
• Pharmacokinetic studies (oral bioavailability, metabolic stability) were performed in animal models and human liver microsomes.
• Synergistic effects with anti-PD-1 therapy were assessed in MC38 and CT26 syngeneic tumor mouse models.

Main Results:

• Compound 5i exhibited potent HPK1 inhibition (IC50 = 0.8 nM) with high selectivity (101.3-fold) over GLK.
• Compound 5i demonstrated favorable oral bioavailability (27-49%) and metabolic stability (T1/2 > 186.4 min).
• Compound 5i showed significant synergistic effects when combined with anti-PD-1 therapy in both MSI and MSS tumor models.

Conclusions:

• Macrocycle-based HPK1 inhibitors, exemplified by compound 5i, represent a promising approach for cancer immunotherapy.
• Compound 5i's potent activity, selectivity, and synergistic potential with checkpoint inhibitors warrant further investigation for clinical development.