Design, Synthesis, and Evaluation of Inhibitors of Hedgehog Acyltransferase

Hedgehog signaling
is involved in embryonic development
and cancer
growth. Functional activity of secreted Hedgehog signaling proteins
is dependent on N-terminal palmitoylation, making
the palmitoyl transferase Hedgehog acyltransferase (HHAT), a potential
drug target and a series of 4,5,6,7-tetrahydrothieno[3,2-c]pyridines have been identified as HHAT inhibitors. Based on structural
data, we designed and synthesized 37 new analogues which we profiled
alongside 13 previously reported analogues in enzymatic and cellular
assays. Our results show that a central amide linkage, a secondary
amine, and (R)-configuration at the 4-position of
the core are three key factors for inhibitory potency. Several potent
analogues with low- or sub-μM IC50 against purified
HHAT also inhibit Sonic Hedgehog (SHH) palmitoylation in cells and
suppress the SHH signaling pathway. This work identifies IMP-1575
as the most potent cell-active chemical probe for HHAT function, alongside
an inactive control enantiomer, providing tool compounds for validation
of HHAT as a target in cellular assays.