The reaction between activator, linked to a tumor-targetingagent, and protodrug leads to the targeted activation of the drug.Here, tumor targeting is achieved by intratumoral injection of a tetrazine-modifiedhyaluronate (SQL70) or by infusion of a tetrazine-modified HER2-targetingantigen-binding fragment (SQT01). Here, ERBB2 is linked to neoplasm.