Novel, Self-Assembling Dimeric Inhibitors of Human β Tryptase

β-Tryptase,
a homotetrameric serine protease, has four identical
active sites facing a central pore, presenting an optimized setting
for the rational design of bivalent inhibitors that bridge two adjacent
sites. Using diol, hydroxymethyl phenols or benzoyl methyl hydroxamates,
and boronic acid chemistries to reversibly join two [3-(1-acylpiperidin-4-yl)­phenyl]­methanamine
core ligands, we have successfully produced a series of self-assembling
heterodimeric inhibitors. These heterodimeric tryptase inhibitors
demonstrate superior activity compared to monomeric modes of inhibition.
X-ray crystallography validated the dimeric mechanism of inhibition,
and compounds demonstrated high selectivity against related proteases,
good target engagement, and tryptase inhibition in HMC1 xenograft
models. Screening 3872 possible combinations from 44 boronic acid
and 88 diol derivatives revealed several combinations that produced
nanomolar inhibition, and seven unique pairs produced greater than
100-fold improvement in potency over monomeric inhibition. These heterodimeric
tryptase inhibitors demonstrate the power of target-driven combinatorial
chemistry to deliver bivalent drugs in a small molecule form.