In Vitro: SC239 is composed of a tubulin-targeting 3-aminophenyl hemiasterlin warhead, SC209 (HY-144880), and a cleavable valine citrulline p-aminobenzyl carbamate linker functionalized with dibenzocyclooctyne (DBCO). The SC239 drug-linker is conjugated via a cleavable valine citrulline p-aminobenzyl carbamate linker functionalized with dibenzocyclooctyne (DBCO). SC239 conjugates exhibits better cytotoxic activity on Igrov1 cells which have lower expression levels of FolRα.