Evaluation of the sonosensitizing activities of 5-aminolevulinic acid and Sn(IV) chlorin e6 in tumor-bearing chick embryos

Background: Recently, 5-aminolevulinic acid (5-ALA), precursors of protoporphyrin IX (PpIX), and Sn(IV) chlorin e6 (SnCe6) have been proposed as possible sonosensitizers for sonodynamic therapy of cancer. Therefore, we evaluated the pharmacokinetic properties and sonosensitizing activities of 5-ALA and SnCe6 in vivo by using the EMT6/KU tumor-bearing chick embryos. Results: The concentration of PpIX in tumor and liver tissues and serum increased in a time-dependent manner after the i.v. administration of 5-ALA; PpIX concentrations reached their peak level after 5-7 h. The concentration of SnCe6 reached its maximum value in the tumor tissue and serum immediately after i.v. administration. The combined treatment of 5-ALA or SnCe6 with ultrasound irradiation showed a significant antitumor effect towards EMT6/KU solid tumors. Conclusion: We evaluated the pharmacokinetic properties and sonosensitizing activities of 5-ALA and SnCe6 in a chick embryo model and found that 5-ALA might be more suitable as a sonosensitizer than SnCe6.