{"entity":{"id":"byondis","kind":"company","name":"Byondis","aka":["Synthon Biopharmaceuticals","Byondis B.V."],"tldr":"Byondis is a Dutch antibody-drug conjugate company, formerly Synthon Biopharmaceuticals, whose HER2 conjugate trastuzumab duocarmazine improved progression-free survival in the TULIP trial but did not win US approval.","summary":"Byondis develops antibody-drug conjugates with its duocarmycin-based ByonZine linker-drug technology and the ByonShieLD site-specific conjugation platform. Trastuzumab duocarmazine (SYD985) links trastuzumab to a DNA-alkylating duocarmazine prodrug; in the phase 3 TULIP trial in pretreated HER2-positive metastatic breast cancer it lengthened progression-free survival over physician's choice, but the FDA issued a complete response letter in 2023 and the European application was withdrawn. Byondis continues with next-generation conjugates.","asOf":"2026-09-17","links":[{"label":"Official website","url":"https://www.byondis.com/"}],"tags":["drug-maker"],"related":[],"cancers":[],"sections":[],"technologies":[],"targets":[],"drugs":["trastuzumab-duocarmazine"],"companies":[],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"provenance":{"editedBy":"OnCo drug-maker linking round (corporate websites and regulatory records)","editedOn":"2026-09-17"},"hq":"Nijmegen","country":"NL","companyType":"biotech","website":"https://www.byondis.com/","investors":[],"funding":[]},"route":"/companies/byondis/","neighbours":{"drug":[{"id":"trastuzumab-duocarmazine","kind":"drug","name":"Trastuzumab duocarmazine","route":"/drugs/trastuzumab-duocarmazine/"}]}}