Celltrion has advanced Phase 3 development of biosimilar candidates for Merck’s Keytruda and Darzalex after regulators in the United States and South Korea cleared amended trial protocols. The U.S. Food and Drug Administration cleared the amended Phase 3 plan for CT-P51 after Celltrion’s July 6 submission, with the confirmation date set for the 5th following the 60-day review period. The global study will enroll 220 patients with previously untreated metastatic non-squamous non-small cell lung cancer and compare CT-P51 with Keytruda over two years. South Korea’s Ministry of Food and Drug Safety also approved an amended Phase 3 protocol for CT-P44, which will study 394 patients with refractory or relapsed multiple myeloma over two years against Janssen’s Darzalex Faspro, alongside lenalidomide and dexamethasone. Darzalex generated approximately $14.35 billion in global net sales last year, while Keytruda is the world’s top-selling drug by revenue. The clearances allow the trials to proceed but do not represent marketing approval or confirm commercial success. Celltrion must still demonstrate comparable efficacy and safety and complete regulatory reviews across jurisdictions.