[E-Daily Reporter Hong Ju-yeon ] Celltrion(068270)Celltrion announced on the 14th that it is terminating its European Phase 3 clinical trial for the Keytruda biosimilar “CT-P51” early and voluntarily withdrawing the trial protocol.

Celltrion announced in a regulatory filing that its board of directors had resolved to prematurely terminate the European Phase 3 clinical trial for CT-P51 and voluntarily withdraw the trial protocol, and that this decision had been registered with the European Medicines Agency’s (EMA) Clinical Trials Information System (CTIS). This clinical trial is a double-blind, randomized, active-controlled Phase 3 study comparing the efficacy and safety of CT-P51 with the originator drug Keytruda in patients with previously untreated metastatic non-squamous non-small cell lung cancer. Celltrion had received approval for the trial protocol from the EMA in December 2024.

This decision is seen as part of a global trend toward regulatory relaxation aimed at streamlining the biosimilar development process. The U.S. Food and Drug Administration (FDA) recently released a draft of its “Guidance on Streamlining Biosimilar Development,” stating that Phase 3 clinical trials may be omitted if certain requirements are met. The EMA has also indicated that it may grant approval without a Phase 3 trial if equivalence can be demonstrated through quality analysis.

Accordingly, Celltrion announced that it has revised its development and approval strategy to reduce the number of clinical trial participants. A Celltrion spokesperson explained, “Patient recruitment for the global Phase 3 clinical trial of CT-P51 has already concluded,” adding, “Since European Union (EU) countries have been excluded from the list of participating countries, there is no longer a need to maintain the European trial protocol.” The company plans to continue the existing Phase 3 trial in participating countries outside the EU to compare the efficacy and safety of CT-P51 and Keytruda. Earlier this month, Celltrion also submitted an application to the FDA to amend its Phase 3 trial protocol, reducing the number of participants from 606 to 220.

Keytruda (generic name: pembrolizumab), developed by MSD, is the world’s top-selling blockbuster drug by revenue, generating approximately $31.7 billion (about 48.9 trillion won) in sales last year. Its substance patent is set to expire in November 2029 in the United States and in January 2031 in Europe.