Merck Opens €70 Million Expansion of ADC Manufacturing Site in St. Louis, USA

News Release

• Increases bioconjugation manufacturing capacity for clinical and commercial programs
• Adds approximately 34,000 square feet of upgraded laboratory, manufacturing support and logistics space
• Expands U.S.-based capacity for complex, highly potent therapies

Darmstadt, Germany, September 30, 2026 – Merck, a leading science and technology company, today opened its €70 million expansion at the company’s Bioconjugation Center of Excellence in St. Louis, Missouri, USA. The expansion increases the site’s antibody-drug conjugate (ADC) manufacturing capacity, strengthening support for customers as their therapies advance from early development toward clinical and commercial production.

ADCs are a growing class of targeted therapies designed to deliver potent medicines directly to diseased cells without damaging nearby healthy tissue. While most ADCs are used to treat cancer, applications for the technology are being explored in non-oncology targets such as autoimmune, infectious and neurodegenerative diseases. With complex construction, stringent containment requirements and specialized development and manufacturing expertise needs, ADCs are a heavily outsourced modality with the largest demand in North America.

“The ADC pipeline is growing rapidly, creating demand for experienced partners that can support increasingly complex programs from early development through commercialization,” said Paolo Carli, Head of Advanced Solutions for the Life Science business of Merck. “By combining additional capacity with more than 15 years of ADC CDMO expertise, this expansion strengthens our ability to help customers advance promising therapies and bring them to patients.”

The expansion encompasses approximately 3,200 square meters of new and upgraded space across process and analytical development (PAD), quality control, manufacturing support and logistics. These capabilities will support clients whose programs are advancing toward late-stage and commercial scale, while creating room to accommodate new customers earlier in development.

The investment expands U.S.-based manufacturing capacity at a time when drug developers are seeking greater supply-chain resilience and specialized capacity for highly potent bioconjugates.

Merck was the first CDMO to manufacture a commercially approved ADC in the US. The company’s St. Louis facility has supported more than 100 ADC investigational new drug applications and more than 160 distinct ADC constructs through bioconjugation services. This experience spans the development of diverse ADC molecules, each requiring tailored combinations of antibodies, linkers, payloads and conjugation approaches.

About Merck

Merck, a leading science and technology company, operates across life science, healthcare and electronics. More than 62,000 employees work to make a positive difference to millions of people’s lives every day by creating more joyful and sustainable ways to live. From providing products and services that accelerate drug development and manufacturing as well as discovering unique ways to treat the most challenging diseases to enabling the intelligence of devices – the company is everywhere. In 2025, Merck generated sales of € 21.1 billion in 65 countries.

Scientific exploration and responsible entrepreneurship have been key to Merck’s technological and scientific advances. This is how Merck has thrived since its founding in 1668. The founding family remains the majority owner of the publicly listed company. Merck holds the global rights to the Merck name and brand. The only exceptions are the United States and Canada, where the business sectors of Merck operate as MilliporeSigma in life science, EMD Serono in healthcare, and EMD Electronics in electronics.

All Merck press releases are distributed by e-mail at the same time they become available on the Merck website. Please go to www.merckgroup.com/subscribe to register online, change your selection or discontinue this service.