On 14 July 2026, ChosunBiz reported that Celltrion has voluntarily terminated the European Phase 3 trial of CT-P51, biosimilar to MSD’s Keytruda® (pembrolizumab), and has withdrawn its investigational new drug application. The early termination of the trial in Europe is part of Celltrion’s strategy to streamline its development program for the biosimilar.
Celltrion’s strategy follows a “reflection paper” published by the European Medicines Agency in April 2025, and adopted by the Committee for Medicinal Products for Human Use (CHMP) in March 2026, which considers that, in certain circumstances, analytical comparability and pharmacokinetic data may be sufficient for approval of biosimilars, with Phase 3 trial data no longer required.
Celltrion has also recently streamlined its US Phase 3 trial for CT-P51 (pembrolizumab), having filed with the FDA an amendment to reduce the number of trial participants from about 600 to around 220. The US Phase 3 trial plan was originally approved by the FDA in August 2024 and aims to compare the efficacy and safety of CT-P51 and Keytruda® in patients with previously untreated metastatic non-squamous non-small cell lung cancer. The trial will be conducted over a period of 2 years.
Celltrion’s revisions to its Phase 3 trial strategy comes shortly after Samsung Bioepis announced positive results from its global Phase 1 and Phase 3 clinical trials for SB27 (pembrolizumab). According to Samsung Bioepis, it was the first developer of a pembrolizumab biosimilar to announce global Phase 3 trial results.
Pembrolizumab biosimilars have reportedly been launched in Paraguay (by Bioeticos in August 2025) and approved in Vietnam (by Biocad in November 2025) and Jordan (by Sana Pharma in February 2026).
There are multiple pembrolizumab biosimilars in development. Formycon’s FYB206 demonstrated pharmacokinetic bioequivalence with Keytruda® in the Phase 1 “Dahlia” study (reported in February 2026). Formycon’s US commercialisation partner, Zydus, has previously expressed optimism that it is well-placed to file the first BLA in the US for biosimilar pembrolizumab. Formycon has also announced agreements for commercialisation of pembrolizumab biosimilar FYB206 with MS Pharma for the MENA region and Lotus for the Asia-Pacific.
Other companies with pembrolizumab biosimilars in clinical trials include Amgen, mAbxience, Sandoz, Bio-Thera, Shanghai Henlius, BioNTech, Qilu Pharmaceutical and Enzene. Alvotech and Dr Reddy’s have entered into a global collaboration and licence agreement to co-develop, manufacture and commercialise a Keytruda® biosimilar and Bio-Thera and Avalon are partnering on commercialisation of a pembrolizumab biosimilar (BAT3306) in Saudi Arabia/MENA.