PTC299 ((4-chlorophenyl) (1S)-6-chloro-1-(4-methoxyphenyl)-1,3,4,9-tetrahydropyrido[3,4-b]indole-2-carboxylate) is an orally active inhibitor of VEGFA mRNA translation and selectively inhibits VEGF protein synthesis at the post-transcriptional level. PTC299 is also a potent inhibitor of dihydrolactate dehydrogenase (DHODH).

PTC299 as an inhibitor of VEGFA mRNA translation in a phenotypic screen and evaluated in the clinic for treatment of solid tumors. To guide precision cancer treatment, we performed extensive biological characterization of the activity of PTC299 and demonstrated that inhibition of VEGF production and cell proliferation by PTC299 is linked to a decrease in uridine nucleotides by targeting dihydroorotate dehydrogenase (DHODH), a rate-limiting enzyme for de novo pyrimidine nucleotide synthesis.