HG-6-63-01 serves as a type II RET tyrosine kinase inhibitor (TKI). It effectively targets and inhibits REarranged during Transfection (RET) kinase, disrupting signaling pathways in human thyroid cancer cell lines possessing oncogenic RET alleles. Moreover, this compound reduces the phosphorylation and signaling of RET oncogenic mutants. HG-6-63-01 further suppresses the proliferation of fibroblasts transformed by RET/C634R and RET/M918T, as well as thyroid cancer cells with RET mutations, showing potential as a therapeutic option for cancers with oncogenic activation of RET.