Anti-Cancer Activities of Thyrointegrin α(v)β(3) Antagonist Mono- and Bis-Triazole Tetraiodothyroacetic Acid Conjugated via Polyethylene Glycols in Glioblastoma

SIMPLE SUMMARY: Different Triazole Tetrac (TAT) thyrointegrin αvβ3 antagonists exhibited optimal therapeutic efficacy against U87 or primary glioblastoma cells. TAT containing molecules bind with high affinity to the integrin αvβ3 and plasma protein Transthyretin (TTR), which facilitate transport across the blood brain barrier. Biological studies showed that decreasing the PEG linker size (1600 versus 4000) or having mono-TAT versus bi-TAT had no significant impact on their αvβ3 binding affinity, anti-angiogenesis, and overall anti-cancer efficacy. ABSTRACT: Integrin αvβ3 receptors are overexpressed in different tumors and their associated neovascularization and hence, represent a potential cancer target. We previously synthesized a high affinity thyrointegrin αvβ3, P(4000)-bi-TAT (tetrac derivative), with potent anticancer properties. However, the long polydisperse PEG conjugate showed large scaleup and analytical/bioanalytical issues. Hence, in the present study, we synthesized a mono versus bi-triazole tetrac with discrete monodisperse PEG, which provided improvement in scaleup and bioanalysis. In the present study, we compared binding affinity and anticancer activates with a smaller PEG size (P(1600)-bi-TAT, Compound 2) and the removal of one TAT molecule (P(1600)-m-TAT, Compound 3) versus P(4000)-bi-TAT, Compound 1. The results of the selectivity and affinity of TATs showed greater affinity to integrin αvβ3. The xenograft weights and tumor cell viabilities were decreased by >90% at all doses compared to the control (ON Treatment, *** p < 0.001) in cells treated with Compounds 1, 2, and 3 in U87-Luc-treated mice. The in vivo luminescent signals of U87-luc cells reflect the proliferation and distribution of tumor cells in the animals and the maximum intensity corresponding to the maximum tumor cells that the animals could tolerate. We found that the three thyrointegrin αvβ3 antagonists exhibited optimal therapeutic efficacy against U87 or primary glioblastoma cells. Biological studies showed that decreasing the PEG linker size (1600 vs. 4000) or having mono-TAT or bi-TAT had no significant impact on their αvβ3 binding affinity, anti-angiogenesis, or overall anti-cancer efficacy.