Light-induced structural rearrangements of axitinib and their role in phototoxic responses

Autores de IIS La Fe

• Meryem El Ouardi

  Autor

• Ignacio Vaya Pérez

  Autor

• Miguel Ángel Miranda Alonso

  Autor

• Inmaculada Andreu Ros

  Autor

Participantes ajenos a IIS La Fe

• Alvarez, A
• Linhares, DD
• Chen, X
• Hofkens, J

Grupos

• Unidad Mixta de Investigación en Mecanismos moleculares de las Reacciones adversas de fármacos

Abstract

Axitinib (AXT) is a second-generation tyrosine kinase inhibitor widely used in advanced renal cell carcinoma and currently explored in light-modulated therapies due to its E/Z photoisomerizable scaffold. Despite its clinical relevance and UVA absorption, the photobiological consequences of its light-induced structural rearrangements remain largely unexplored. Here, we elucidate the mechanistic basis of AXT phototoxicity by integrating photophysical characterization with cellular studies while distinguishing the roles of its (E)- and (Z)-isomers. Steadystate photolysis reveals that (E)-AXT undergoes photodegradation in aqueous media but preferentially isomerizes to (Z)-AXT in lipophilic environments, which is accelerated in the presence of human serum albumin (HSA). Conversely, (Z)-AXT displays medium-dependent photostability, being stabilized by HSA and reverting to the (E)-isomer in aqueous solution. Spectroscopic studies, including laser flash photolysis, support a mechanism involving tautomerization through excited-state intramolecular proton transfer and transient radical intermediates, consistent with predominant Type I photosensitization. Notably, (Z)-AXT is favored in lipophilic and protein-rich environments, likely through intramolecular hydrogen-bond stabilization of its 2H-tautomer. Cellular studies in keratinocytes revealed two complementary phototoxic pathways: photoinduced conversion of cytotoxic (Z)-AXT from (E)-AXT and the intrinsic phototoxicity of (Z)-AXT under irradiation. Although both isomers cause similar protein oxidation, (Z)-AXT is the main contributor due to its higher stability with HSA. While alkaline comet assays detected no direct DNA strand breaks, gamma-H2AX immunostaining revealed lightinduced DNA double-strand breaks. Overall, these findings identify (Z)-AXT as a previously unrecognized phototoxic species and establish a framework linking isomerization, microenvironmental stabilization, and Type I photosensitization in kinase inhibitors.

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Keywords

• Photo(geno)toxicity; Photoisomerization; Photophysical studies; Tautomerism; Expansion microscopy; Tyrosine kinase inhibitor