TRANSTHERA-B (02617) announced that the company presented a poster at the 2026 American Association for Cancer Research (AACR) Annual Meeting. The poster disclosed lineage plasticity as a driver mechanism for endocrine resistance in HR+ breast cancer and its clinical translational significance. Through continuous drug screening and co-culture models, the research found that both treatment-induced and microenvironment-driven resistance converge on the co-activation of FGFR and JAK signaling pathways. This co-activation subsequently suppresses the expression of luminal-related genes, including ESR1 and PGR. Tiengotinib, an inhibitor capable of simultaneously targeting both FGFR and JAK, was shown to restore the luminal characteristics of tumor cells. Furthermore, it resensitized resistant models to endocrine therapy both in vitro and in vivo. These findings support dual FGFR-JAK blockade as an effective strategy to overcome lineage plasticity-driven endocrine resistance. A Phase II clinical trial evaluating tiengotinib in combination with endocrine therapy for advanced HR+ breast cancer is currently underway.