Tilfrinib是一个强效且选择性的乳腺肿瘤激酶（Brk）抑制剂，其IC50为3.15 nM，表现出抗增殖活性，并作为一个有前景的抗肿瘤药物。

BRK inhibitor P21d hydrochloride is a potent breast tumor kinase (BRK/PTK6) inhibitor with an IC50 of 30 nM. BRK inhibitor P21d hydrochloride inhibits p-SAM68 with an IC50 of 52 nM. BRK inhibitor P21d hydrochloride can be used to evaluate the in vivo activity of BRK inhibitors in xenograft breast tumor models[1].