Formosa Pharmaceuticals has submitted a Clinical Trial Application (CTA) to European regulatory authorities to conduct a pivotal clinical trial for TSY-110, a biosimilar candidate referencing Roche's Antibody Drug Conjugate (ADC) Kadcyla (ado-trastuzumab emtansine), indicated for HER2-positive metastatic and early-stage breast cancer.

Designed following regulatory guidance from both US and European Union (EU) authorities, the upcoming trial will evaluate the safety, tolerability, pharmacokinetics, and immunogenicity profile of TSY-110 compared with the reference product. This milestone advances Formosa Pharmaceuticals' and EirGenix's shared goal of providing cost-effective biosimilar ADC treatments to patients across regulated global markets.

Erick Co, Ph.D., President and Chief Executive Officer (CEO), Formosa Pharmaceuticals, said, "Filing this CTA marks a significant achievement for Formosa Pharmaceuticals and underscores our strategic alliance with EirGenix. ADCs have established themselves as mainstays in oncology, including HER2-positive breast cancer care, but patient access remains constrained by high treatment costs. Advancing TSY-110 into clinical evaluation is a momentous step toward fulfilling our goal of delivering world-class, accessible ADC options to oncologists and patients."

TSY-110, also designated as EG12043, is an ADC biosimilar co-developed by Formosa Pharmaceuticals and EirGenix, Inc. The conjugate links HER2 monoclonal antibody, trastuzumab, with a cytotoxic payload (mertansine) to selectively eradicate HER2-overexpressing cancer cells while minimising systemic toxicity. Comprehensive preclinical assessments demonstrate high biosimilarity, Drug Antibody Ratio (DAR) consistency, and comparable plasma kinetics to the reference product.

HER2-positive breast cancer accounts for a significant portion of all breast cancer diagnoses globally. Approximately, 2.4 million breast cancer cases were diagnosed in 2024, with HER2+ disease affecting roughly 360,000 to 480,000 of these patients based on the standard 15 to 20 percent prevalence rate. HER2-targeted therapies continue to be a prominent tool in modern oncological care.

Kadcyla, approved by the US Food and Drug Administration (FDA) in 2013, generated approximately USD 2.5 billion in global sales in 2025.