Biodistribution and anti-tumor efficacy of intratumorally injected necrosis-avid theranostic agent radioiodinated hypericin in rodent tumor models

H22 and S180 tumor-bearing Kunming (KM) mice were intratumorally injected with 131 I-monoiodohypericin ( 131 I-MIH) to investigate the biodistribution of 131 I-MIH as a function of time. Single-photon emission computed tomography (SPECT), autoradiography, fluorescence microscopy and hematoxylin and eosin (H&E) staining were performed to determine the intra-tumoral distribution of 131 I-MIH.

A therapeutic evaluation study was also performed in the tumor-bearing KM mice using saline and a positive drug as controls. Gamma counting, SPECT images, autoradiography and fluorescence microscopy and H&E staining results revealed intense retention of 131 I-MIH in the necrotic tumor over 168 h and good in vivo stability of the agent. Therapy with a single dose of intra-tumoral administration of 131 I-MIH caused significant tumor growth delay.