CARM1 degrader-1 hydrochloride is the hydrochloride salt form of CARM1 degrader-1. CARM1 degrader-1 hydrochloride is a PROTAC degrader for co-activator associated argininemethyltransferase 1 ( CARM1 ), which degrades CARM1 in a VHL- and proteasome-dependent manner with a DC 50 of 8.1 nM. CARM1 degrader-1 hydrochloride inhibits methylation of CARM1 substrates such as poly(A)-binding protein PABP1 and BGR1-associated factor BAF155, and thus inhibits breast cancer cell migration.