A novel in situ permeation system and its utility in cancer tissue ablation

Focal ablation therapy is an emerging treatment modality for localized cancer lesions. It is an attractive strategy for inhibiting tumor progression and preventing morbidity associated with open surgery. As for intratissue drug delivery systems for use in local therapy, the convection-enhanced delivery (CED) of liquid drugs has been utilized, particularly for the treatment of malignant brain tumors. Although the conventional CED system is useful for providing drug/vehicle-based local therapy, there are several reported disadvantages in terms of the ability to control the extent of drug diffusion. We herein developed and validated a novel in situ permeation (ISP)-MW-1 system for achieving intratissue drug diffusion. The ISP system includes a perfusion catheter connected to an injector and aspirator, which enables intratissue perfusion of the solute diluted in the vehicle in the tip-inserted cavity. We subsequently evaluated the utility of the ISP-MW-1 system for in situ permeation in a subcutaneous tumor model in hamsters. Dehydrated ethanol, saline and 50% acetic acid were evaluated as the vehicle, and methylene blue was used as a dissolved substance for evaluating the diffusion of the agent. As a result, almost all of the tumor tissue within the capsule (tumor size: ~3 cm) was permeated with the dehydrated ethanol and 50% acetic acid and partially with the saline. We further demonstrated that ISP treatment with 50% acetic acid completely ablated the subcutaneous tumors in all of the treated hamsters (n=3). Therefore, the ISP-MW-1 system is a promising approach for controlling the intratissue diffusion of therapeutic agents and for providing local ablation therapy for cancer lesions. We believe that this system may be applicable to a broad range of medicinal and industrial fields, such as regenerative medicine, drug delivery systems, biochemistry and material technologies as well as cancer therapy.