The
importance of Discoidin Domain Receptor 1 (DDR1) in renal fibrosis
has been shown via gene knockout and use of antisense oligonucleotides;
however, these techniques act via a reduction of DDR1 protein, while
we prove the therapeutic potential of inhibiting DDR1 phosphorylation
with a small molecule. To date, efforts to generate a selective small-molecule
to specifically modulate the activity of DDR1 in an in vivo model have been unsuccessful. We performed parallel DNA encoded
library screens against DDR1 and DDR2, and discovered a chemical series
that is highly selective for DDR1 over DDR2. Structure-guided optimization
efforts yielded the potent DDR1 inhibitor 2.45, which
possesses excellent kinome selectivity (including 64-fold selectivity
over DDR2 in a biochemical assay), a clean in vitro safety profile, and favorable pharmacokinetic and physicochemical
properties. As desired, compound 2.45 modulates DDR1
phosphorylation in vitro as well as prevents collagen-induced
activation of renal epithelial cells expressing DDR1. Compound 2.45 preserves renal function and reduces tissue damage in Col4a3
–/– mice (the preclinical
mouse model of Alport syndrome) when employing a therapeutic dosing
regime, indicating the real therapeutic value of selectively inhibiting
DDR1 phosphorylation in vivo. Our results may have
wider significance as Col4a3
–/– mice also represent a model for chronic kidney disease, a disease
which affects 10% of the global population.