Disease associated mutations at valine 804 in the RET receptor tyrosine kinase confer resistance to selective kinase inhibitors

We have recently demonstrated that the pyrazolopyrimidines
PP1and PP2 and the 4-anilinoquinazoline ZD6474
display a strong inhibitory activity (IC50p100 nM)
towards constitutively active oncogenic RET kinases.
Here, we show that most oncogenic MEN2-associated
RET kinase mutants are highly susceptible to PP1, PP2
and ZD6474 inhibition. In contrast, MEN2-associated
swap of bulky hydrophobic leucine or methionine residues
for valine 804 in the RET kinase domain causes resistance
to the three compounds. Substitution of valine 804 with
the small amino- acid glycine renders the RET kinase even
more susceptible to inhibition (ZD6474 IC50: 20nM) than
the wild-type kinase. Our data identify valine 804 of RET
as a structural determinant mediating resistance to
pyrazolopyrimidines and 4-anilinoquinazolines.