We injected ECLC5 (NSCLC cell line, TRIM33-RET) and HMSC-RET (immortalized human mesenchymal stem cells in which SPECCL1-RET was introduced by CRISPR-Cas9 genomic engineering, sarcoma model) cells... TAS0953/HM06 was superior to selpercatinib at inhibiting growth of ECLC5 (p < 0.0001) and HMSC-RET (p = 0.0005) brain xenograft tumors, and increasing survival of tumor-bearing animals (ECLC5: TAS0953/HM06 139±0.5 days, selpercatinib 95+2.3 days, p = 0.002; HMSC-RET: TAS0953/HM06 41± 2.2 days, selpercatinib 20±3 days, p = 0.0001).