Abstract: [Problem] It is desired to develop an antibody-drug conjugate capable of being systemically administered and delivering a STING agonist specifically to a target cells or organ (for example, a tumor lesion), and a therapeutic agent and/or therapeutic method using the antibody-drug conjugate for diseases related to STING agonist activity, for example, diseases (for example, cancers) to which immunostimulation therapy can be applied. [Solution] The present invention provides a novel antibody-CDN derivative conjugate which can be systemically administered and exhibits an antitumor effect against an antigen-expressing tumor.

Abstract: Desired is development of novel CDN derivatives having STING agonist activity; and a therapeutic agents and/or therapeutic methods using the novel CDN derivatives for diseases associated with STING agonist activity. Further desired is development of a therapeutic agents and/or therapeutic methods capable of delivering the novel CDN derivatives specifically to targeted cells and organs for diseases associated with STING agonist activity. The present invention provides novel CDN derivatives having potent STING agonist activity, and antibody-CDN derivative conjugates including the novel CDN derivatives.