Design, synthesis, and biological evaluation of Flavokavain B derivatives as potent TRF2 inhibitors for the treatment of Osteosarcoma

Telomere repeat-binding factor 2 (TRF2) is a crucial component of the shelterin complex, commonly overexpressed in osteosarcoma (OS) and positively correlated with its progression. To date, effective TRF2 inhibitors for in vivo applications remain limited. In this study, a series of Flavokavain B derivatives were designed and synthesized, and their TRF2 inhibition and antitumor activity were evaluated. Among the tested compounds, the active compound F2 showed remarkable inhibition of TRF2 expression, along with potent antiproliferative activity in U2OS and MG63 cells, with IC₅₀ values of 5.28 μM and 1.52 μM, respectively. Moreover, F2 significantly suppressed OS cell proliferation and induced apoptosis by accelerating telomere shortening and loss due to TRF2 inhibition. Mechanically, F2 selectively inhibited TRF2 protein expression and telomeric localization by directly binding to the TRF2_TRFH domain. Furthermore, F2 demonstrated strong antitumor efficacy with minimal toxicity in an MG63-derived xenograft mouse model. These findings demonstrate that F2 is a promising drug candidate for the treatment of osteosarcoma.