Synthesis and biological evaluation of new boron-containing chlorin derivatives as agents for both photodynamic therapy and boron neutron capture therapy of cancer

New boron-containing chlorin derivatives 9 and 13 as agents for both photodynamic therapy (PDT) and boron neutron capture therapy (BNCT) of cancer were synthesized from photoprotoporphyrin IX dimethyl ester (2) and l-4-boronophenylalanine-related compounds. The in vivo biodistribution and clearance of 9 and 13 were investigated in tumor-bearing mice. The time to maximum accumulation of compound 13 in tumor tissue was one-fourth of that of compound 9, and compound 13 showed rapid clearance from normal tissues within 24 h after injection. The in vivo therapeutic efficacy of PDT using 13 was evaluated by measuring tumor growth rates in tumor-bearing mice with 660 nm light-emitting diode irradiation at 3 h after injection of 13. Tumor growth was significantly inhibited by PDT using 13. These results suggested that 13 might be a good candidate for both PDT and BNCT of cancer.

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