Among them, SIAIS562055 emerged as a potent SOS1 PROTAC, exhibiting efficacy against not only KRAS-mutant cancer but also BCR–ABL–driven CML, both in vitro and in vivo, with evidence of robust and durable SOS1 degradation and downstream signal inhibition. Here, SOS1 is linked to chronic myelogenous leukemia, BCR-ABL1 positive.