Unveiling the mechanism of activation of the Te(IV) prodrug AS101. New chemical insights towards a better understanding of its medicinal properties.

AS101 (Ammonium trichloro (dioxoethylene-O,O') tellurate) is an important hypervalent Te-based prodrug. Recently, we started a systematic investigation on AS101 with the aim to correlate its promising biological effects as a potent immunomodulator drug with multiple medicinal applications and its specific chemical properties. To date, a substantial agreement on the rapid conversion of the initial AS101 species into the corresponding TeOCl ₃ ^- anion does exist, and this latter species is reputed as the pharmacologically active one. However, we realized that TeOCl ₃ ^- could quickly undergo further steps of conversion in an aqueous medium, eventually producing the TeO ₂ species. Using a mixed experimental and theoretical investigation approach, we characterized the conversion process leading to TeO ₂ occurring both in pure water and in reference buffers at physiological-like pH. Our findings may offer a valuable "chemical tool" for a better description, interpretation -and optimization- of the mechanism of action of AS101 and Te-based compounds. This might be a starting point for improved AS101-based medicinal application.
Competing Interests: Declaration of competing interest There are no conflicts to declare.
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