TPP-1 binds to PD-L1 with high affinity and blocks PD-1/PD-L1 interaction. The KD value of PD-L1 with TPP-1 peptide is about 95 nmol/L (around five times less than that with PD-1), The binding site of TPP-1 to PD-L1 is close to the interactive site of PD-1 and PD-L1.
TPP-1 (4 μM) reactivates T-cell functions, it induces IFNγ release significantly higher than control and SPP-1, and the TPP-1 group shows similar outcomes for cell proliferation.