Design, synthesis, and pharmacological evaluation of novel isoindoline-based HPK1 degraders

Hematopoietic progenitor kinase 1 (HPK1), a critical negative regulator of T-cell signaling, has emerged as an attractive yet challenging therapeutic target in immuno-oncology. Inspired by the clinical success of immunomodulatory drugs, we designed a series of novel proteolysis-targeting chimera (PROTAC) molecules targeting HPK1. Among these, compound D02 demonstrated potent HPK1 degradation (DC₅₀ = 3.07 ± 1.81 nM, D_max = 98.33 %) and effectively suppressed downstream phosphorylation of SLP-76 in Jurkat cells (IC₅₀ = 11.38 nM). D02 potently induced IL-2 (EC₅₀ = 4.51 nM) and IFN-γ (EC₅₀ = 3.02 nM) secretion in human primary T cells. Notably, D02 exhibited favorable safety profiles in preliminary toxicological evaluations. We propose that D02 represents a promising candidate for further development of HPK1 degraders.