Real Tech Fund*, operated by UntroD Capital Japan Inc. (Location: Minato-ku, Tokyo; Representative: Akihiko Nagata), has invested in CastBio Inc. (Head Office: Chuo-ku, Tokyo; CEO: Masaaki Fujiwara, hereafter "CastBio"), a company developing next-generation Antibody-Drug Conjugates (ADCs) based on its proprietary VLK linker technology. With this investment, CastBio will advance its non-clinical development and organizational structure, aiming to create innovative treatments for refractory solid tumors. Company Overview: CastBio is a drug discovery startup established through a company split from Rinsho K.K., a venture originating from the National Cancer Center. Refractory solid tumors such as glioblastoma (GBM), pancreatic cancer, and scirrhous gastric cancer have extremely low 5-year survival rates and represent significant unmet medical needs. One reason for their refractory nature is believed to be the cancer stroma in tumor tissue, which hinders drug penetration. CastBio is tackling this challenge with a new therapeutic approach. They have developed an anti-IF-ADC that combines an antibody that specifically binds to insoluble fibrin (IF) present in the cancer stroma with a VLK linker technology that is cleaved by plasmin, which is abundant in the stroma. This achieves efficient drug delivery to the tumor tissue. Purpose and Use of Funds: The funds raised by CastBio will be used to build the R&D structure for the anti-IF-ADC, advance its non-clinical development, and strengthen and protect its intellectual property. Comments from the Person in Charge: There is a strong demand for the development of innovative treatments for refractory solid tumors, which have an extremely poor prognosis with a 5-year survival rate below 10%. The cancer stroma, a factor in their refractory nature, is formed as cancer cells proliferate while incorporating blood vessels, repeating a process of bleeding, hemostasis, and the subsequent breakdown of fibrin clots by plasmin. The anti-I