Human PBMCs were purchased from Shanghai Hycells Co., Ltd and were cultured at 37 °C in a 5% CO2-humidified atmosphere, maintaining in RPMI-1640 medium with 10% FBS. hPBMCs were seeded in 96-well plate and were treated with HPK1 inhibitors for 1 hours. Cells were then transferred into a plate pre-coated with anti-human CD3 (0.5 μg/mL), fueling with anti-human CD28 (0.5 μg/mL), and further cultured for 48 hours. PGE2 (5 nM) was added together with anti-human CD28 if needed. Culture supernatant was collected after 48 hours and IL-2 was tested by ELISA (Biolegend 431804) following the manufacture's instruction. Two-way ANOVA were used to compare effects among several doses of 3 compounds. A mixed-effect analysis were used to compare effectes with or without PGE2. Multipule comparisons were performed by Fisher's LSD multipule comparison. Paried t-test were used to analysis drug effect of individual hPBMC donor.