OBI-998

OBI-998 is an **antibody-drug conjugate** in preclinical development by **OBI Pharma** for the treatment of **SSEA-4-expressing cancers**. It consists of a **humanized anti-SSEA-4 antibody** linked to the highly potent **microtubule-disrupting payload monomethyl auristatin E**. The molecule is designed to bind SSEA-4 on tumor cells, undergo internalization, and release its cytotoxic payload intracellularly, producing direct tumor cell killing and reported bystander activity. Preclinical reports describe high target specificity, rapid internalization, persistent intratumoral MMAE deposition, and antitumor activity across multiple animal models.