Celltrion's record Q1, Samsung Biologics' ADC milestone, and the GLP-1 lane Korea is now openly building

The pharmacy counter in Hamburg does not advertise where its adalimumab comes from. But the molecule's first-quarter 2026 numbers tell the story: Celltrion's Yuflyma posted quarterly sales of ₩108 billion, up roughly 60% year-on-year, crossing the ₩100 billion mark for the first time. Five years ago Korean share of that molecule was a rounding error. The story has changed so quickly that most Western investor models have only just begun to reprice the cost curve.

Celltrion and Samsung Bioepis, the two Korean biosimilar platforms Nathan has covered since their founding, did not win on price alone. They won on the three hardest parts of the biosimilar business — regulatory throughput, aseptic capacity, and self-administered device integration — while most Western pharma chose to build originators instead. Samsung Biologics, the contract manufacturer tied to the Bioepis platform, has spent the capital cycle that Pfizer and Merck did not. Both companies' Q1 2026 disclosures, released late April and early May, made clear that the operating leverage of those choices is now compounding.

Celltrion's record quarter

Celltrion reported Q1 2026 revenue of ₩1.145 trillion (up 36% year-on-year) and operating profit of ₩321.9 billion (up 115%) at an operating margin of 28.1%. Net income more than tripled. The five biosimilars launched during 2025 — covering tocilizumab, denosumab, ustekinumab, aflibercept, and additional indications — contributed ₩581.2 billion in the quarter, up 67% year-on-year. Management reaffirmed full-year guidance of ₩5.3 trillion in revenue and ₩1.8 trillion in operating profit, alongside treasury-share cancellations totalling roughly ₩1.9 trillion.

On April 30, 2026, Celltrion submitted an EMA application for Herzuma SC (CT-P6 SC), a subcutaneous trastuzumab biosimilar — first-mover in a category where no SC trastuzumab biosimilar is on the market. Earlier in 2026 the firm secured FDA approval for Eydenzelt (aflibercept biosimilar to Eylea) and launched a tocilizumab SC biosimilar in the United States in March. The pipeline math underwriting Celltrion's commitment to commercialise 22 biosimilars by 2030 — twelve immunology, seven oncology, three other — is now visibly converting into reported revenue.

Why Pfizer stopped competing

Vegzelma, the bevacizumab biosimilar, holds 28% market share across Europe and is currently the top-prescribed bevacizumab biosimilar on the continent — global Vegzelma sales rose 66.8% year-on-year in Q1 2026. Yuflyma is the European adalimumab biosimilar leader. Remsima SC retained 25% share across Germany, Spain, the UK, Italy and France at the most recent disclosed reading.

In 2023 Pfizer quietly wound down active development on four of its remaining biosimilar programs. The stated reason was portfolio focus. The operational reason, as our interviews with former program leads made clear, was simpler: the unit economics no longer closed against a Korean competitor that had already amortised the manufacturing stack.

“We were competing against a company whose cost base was, in effect, a sunk national asset. You cannot out-invest that from a quarterly earnings cycle.”

— Former VP, Pfizer Global Biopharma, 2024

Samsung Biologics: Q1, Plant 5, and the ADC milestone

Samsung Biologics reported Q1 2026 revenue of ₩1,257.1 billion (up 25.8% year-on-year) and operating profit of ₩580.8 billion (up 35.0%) on April 22. Plant 5 — the 180,000-litre first facility of Bio Campus II that came online in April 2025 — is now contributing to revenue, taking total Songdo capacity past 785,000 litres, the largest single-site biologics manufacturing footprint on the planet. The dedicated ADC facility on the Songdo campus completed its first commercial-scale engineering run during the quarter, a milestone that converts a contract pipeline tied to LigaChem Biosciences and other ADC developers into deliverable manufacturing slots.

Plant 6 / Bio Campus III is committed but on a longer fuse — CEO commentary at the JPM 2026 conference put groundbreaking inside 2026 and a ₩7 trillion investment programme out to 2034, sustaining the path toward roughly 1.32 million litres of total capacity.

GLP-1 and ADC: the two prizes Korea is now openly building

April 2026 made the GLP-1 ambition explicit. Samsung Bioepis, Epis Nexlab, and G2G Bio signed a three-party joint venture to develop long-acting GLP-1 obesity drugs using microsphere delivery, designed for dosing intervals measured in months rather than weeks — a direct play at the differentiation frontier of the semaglutide/tirzepatide class. Samsung Biologics is separately reported to be reviewing the acquisition of a US facility specifically for GLP-1 contract manufacturing, the kind of capacity move that becomes valuable only if you expect the 2031–2033 patent cliff to be the largest contract-biologics RFP in pharmaceutical history.

For investors modelling Korean bio as a follow-on story, the mental model needs updating. These are no longer catch-up players. They are, quietly, the marginal producers that now set global injectable pricing, the contract manufacturers most Western biotech pipelines will tech-transfer to at commercial scale, and — through the GLP-1 microsphere bet — the firms making the first credible Korean push into novel-mechanism obesity therapy.