Development of TX-816 and its derivatives as 5-Aminolevurinic acid-based photodynamic therapy sensitizer

5-Aminolevulinic acid (ALA), a precursor of protoporphyrin IX (PpIX), is now widely used for photodynamic therapy (ALA-PDT) of various cancers. Recently, I found that treatment of cancer cells with the Schiff base derivative TX-816 along with ALA could significantly increase the efficacy of ALA-PDT. This enhancing effect of TX-816 on ALA-PDT is attributed to 3,5-dichlorosalicylaldehyde (DCSA), a molecule produced by the degradation of TX-816. Similar to TX-816, DCSA significantly enhances the effect of ALA-PDT. Furthermore, DCSA could restore the sensitivity of cancer cells that acquired resistance to ALA-PDT. These results indicate that DCSA, as well as TX-816, is a potent lead compound for the development of an ALA-PDT sensitizer.

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