Formosa Pharmaceuticals filed a Clinical Trial Application with European regulatory authorities on August 28, 2026, to launch a pivotal clinical trial for TSY-110, an antibody-drug conjugate biosimilar targeting HER2-positive breast cancer, according to an official company announcement reported by PR Newswire.
Clinical Trial Plans and Regulatory Pathway for TSY-110
The upcoming trial will evaluate the safety, tolerability, pharmacokinetics, and immunogenicity profile of TSY-110 against its reference product, Roche’s Kadcyla (ado-trastuzumab emtansine). According to Formosa Pharmaceuticals, the trial design follows regulatory guidance issued by both United States and European authorities. This evaluation marks a key step toward establishing TSY-110 as the first biosimilar alternative to Kadcyla in major regulated markets.
Drug Mechanism and Preclinical Development
Also designated as EG12043, TSY-110 was co-developed by Formosa Pharmaceuticals and EirGenix, Inc. The antibody-drug conjugate links the HER2 monoclonal antibody trastuzumab with the cytotoxic payload mertansine. This design aims to selectively eradicate HER2-overexpressing cancer cells while limiting systemic toxicity. Preclinical assessments demonstrated high biosimilarity, consistent drug-antibody ratios, and plasma kinetics comparable to the reference product, according to company statements.
Market Impact and Corporate Alliances
Formosa Pharmaceuticals President and Chief Executive Officer Erick Co stated that high treatment costs continue to restrict patient access to antibody-drug conjugates, despite their status as oncology mainstays. The strategic alliance between Formosa Pharmaceuticals and EirGenix seeks to address this barrier by advancing cost-effective biosimilar options for oncologists and patients. Kadcyla, which received U.S. Food and Drug Administration approval in 2013, generated approximately $2.5 billion in global sales during 2025.
Global Burden of HER2-Positive Breast Cancer
HER2-positive disease accounts for a substantial share of global breast cancer diagnoses. Out of approximately 2.4 million breast cancer cases diagnosed worldwide in 2024, roughly 360,000 to 480,000 patients were affected by HER2-positive tumors, based on a standard 15% to 20% prevalence rate. HER2-targeted therapies remain a prominent component of modern cancer care, making the development of biosimilar alternatives a priority for expanding treatment access.
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