Discovery of an Exceptionally Orally Bioavailable and Potent HPK1 PROTAC with Enhancement of Antitumor Efficacy of Anti-PD-L1 Therapy

HPK1, a well-known negative regulator of T cell receptors,
can
cause T cell dysfunction when abnormally activated. In this study,
a PROTAC C3 was designed and synthesized by optimizing
the physicochemical properties of the warhead, linker, and CRBN ligand. C3 demonstrated significant HPK1 degradation with a DC50 of 21.26 nM, excellent oral absorption with a Cmax of 10,899.92 ng/mL, and a bioavailability (F %) of 81.7%. C3 also showed degradation selectivity
and potent immune activation effects. Proteomic and WB analyses revealed
that immune-activating effect of C3 is attributed to
the inhibition of SLP76 and NF-κB signaling pathways, as well
as the enhancement of MAPK signaling pathway transduction. In vivo
efficacy study demonstrated that oral administration of C3 in combination with anti-PDL1 antibody significantly inhibited tumor
growth (tumor growth inhibition = 65.58%). These findings suggest
that C3, a novel HPK1 PROTAC, holds promise as a therapeutic
agent for tumor immunotherapy.