# Byondis

Source: https://onco.cc/companies/byondis/  
OnCo record `byondis` (Company). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

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over physician's choice, but the FDA issued a complete response letter in 2023 and the European application was withdrawn.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.

## Fields

- Kind: Company
- Last checked: 2026-09-17
- Also known as: Synthon Biopharmaceuticals; Byondis B.V.
- Tags: drug-maker
- HQ: Nijmegen
- Type: biotech
- Website: https://www.byondis.com/

## Sources

- Official website: https://www.byondis.com/

## Connected records

- drugs: [Trastuzumab duocarmazine](https://onco.cc/drugs/trastuzumab-duocarmazine/)

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