One week after filing its first US drug application, Samsung Bioepis presented the clinical evidence that supports it — a complete Phase 3 dataset showing its Keytruda copy works as well as the original in a 555-patient lung cancer trial, the most detailed public glimpse yet into the competitive pressure building against the world’s best-selling medicine.

Samsung Bioepis has presented the full Phase 3 dataset for SB27, its proposed biosimilar to Merck’s Keytruda (pembrolizumab), at the Society for Immunotherapy of Cancer (SITC) 41st Annual Meeting, running November 4–8 at the Phoenix Convention Center in Phoenix, Arizona. The poster on November 6 is the first full Phase 3 data disclosure for any pembrolizumab biosimilar — and it arrives exactly one week after Samsung Bioepis submitted a Biologics License Application (BLA) to the US Food and Drug Administration, a filing the company made public on October 30, 2026.

That sequence matters. The BLA, which covers 18 indications including melanoma and lung cancer, has formally placed the FDA on a standard 12-month review clock under the Biosimilar User Fee Amendments. If the review proceeds on schedule, a decision from the agency could come as early as the fourth quarter of 2027 — roughly one year before the core US composition-of-matter patent protecting Keytruda’s intravenous formulation is expected to expire in December 2028. Keytruda generated $31.7 billion in global sales in 2025, making it both the world’s best-selling cancer drug and the world’s best-selling prescription medicine.

Trial Design and Clinical Results

The double-blind, randomized, parallel-group, multicenter Phase 3 study enrolled 555 patients with metastatic non-squamous non-small cell lung cancer (NSCLC) — a population where pembrolizumab combined with chemotherapy has become a standard first-line option — across 14 countries. Participants were randomized 1:1 to receive either SB27 (n=283) or the reference pembrolizumab (n=272), each at 200 mg intravenously every three weeks, alongside pemetrexed every three weeks and carboplatin for the first four cycles.

The trial’s primary endpoint was objective response rate (ORR) — the proportion of patients whose tumors measurably shrank — measured at Week 24. SB27 achieved a 34.6% ORR, compared with 37.9% for originator Keytruda. Critically, the 90% confidence interval for the ORR ratio between the two arms — 0.737 to 1.071 — fell entirely within the pre-specified equivalence margin of 0.712 to 1.405, formally demonstrating biosimilar equivalence on the primary endpoint.

Secondary efficacy endpoints, including progression-free survival, duration of response, and overall survival, showed high comparability between the two groups. Safety, pharmacokinetic, and immunogenicity profiles for SB27 were also reported as comparable to the originator.

The full dataset disclosed today expands on topline results Samsung Bioepis first announced in June 2026, when it reported that both the Phase 1 and Phase 3 studies for SB27 had met their respective primary endpoints. The Phase 1 pharmacokinetic data were separately presented as a poster at the European Society for Medical Oncology (ESMO) congress in Madrid in late October 2026. The two back-to-back presentations at ESMO and SITC serve as the peer-reviewed scientific record underpinning the FDA BLA filed between them.

How Pembrolizumab Works — and Why Biosimilar Development Is So Hard

Pembrolizumab belongs to a class of drugs called immune checkpoint inhibitors, whose discovery earned James P. Allison and Tasuku Honjo the 2018 Nobel Prize in Physiology or Medicine. It works by blocking the PD-1 receptor, a protein that sits on the surface of T cells — the immune system’s principal cancer-killing cells. Normally, when a cell displays the PD-L1 protein, it signals to T cells: “don’t attack me.” Cancer cells have learned to exploit this mechanism, overproducing PD-L1 to hide from immune surveillance. Pembrolizumab binds PD-1 and blocks this interaction, lifting the brake and allowing T cells to recognize and attack tumors.

Since its initial FDA approval in 2014, pembrolizumab has amassed more than 40 approved indications across cancer types — a breadth that reflects both its clinical potency and an unusually broad application of the tissue-agnostic approval framework the FDA pioneered for the drug. That indication footprint also makes it uniquely difficult to replicate through biosimilar development.

A biosimilar is not a small-molecule generic. Because pembrolizumab is a 149-kilodalton humanized IgG4 antibody — a large, three-dimensionally complex molecule assembled by living cells — its precise structure depends heavily on the manufacturing process: the specific cell line, fermentation conditions, and purification steps used to produce it. Even minor process differences can alter glycosylation patterns, charge variants, or aggregation profiles in ways that change how the molecule behaves in the body. Matching all of those properties to the reference product requires not only analytical chemistry but clinical proof — which is what the Phase 3 trial provides.

Measuring pharmacokinetic equivalence uses a parameter called AUC, or area under the concentration-time curve, which captures total drug exposure in the body over time. The Phase 1 trial enrolled 163 patients across four countries and confirmed that SB27’s AUC fell within the predefined equivalence criteria relative to both EU-sourced and US-sourced Keytruda. The larger Phase 3 trial then directly confirmed that this pharmacological equivalence translates into equivalent clinical effect in a first-line metastatic lung cancer population.

Samsung Bioepis’s Strategic Position

“Oncology remains an important area of focus for Samsung Bioepis, and the development of SB27 reflects our continued commitment to advancing high-quality biosimilar medicines,” said Donghoon Shin, Executive Vice President and Clinical Sciences Division Leader at Samsung Bioepis, in comments accompanying the SITC disclosure. “We aim to establish a robust clinical evidence base to support the development of a potential biosimilar treatment option for oncology patients worldwide.”

Samsung Bioepis, the Incheon-based biopharmaceutical subsidiary of Samsung Epis Holdings, is building a pipeline of cancer biologics to complement its existing commercial portfolio spanning immunology, ophthalmology, and hematology. The company already has approximately 11 biosimilars approved and launched across more than 40 countries. If SB27 successfully reaches commercialization, analysts have noted it would represent a step-change in scale: a pembrolizumab biosimilar would potentially become the single largest revenue contributor in the company’s history.

The company pursued an unusually comprehensive clinical strategy for SB27, running Phase 1 (pharmacokinetic) and Phase 3 (comparative efficacy) studies in parallel — an overlap strategy designed to compress the development timeline. That parallel approach also explains the rapid cadence of the past six weeks: Phase 1 data at ESMO in October, FDA BLA filed on October 30, full Phase 3 data at SITC today.

Samsung Bioepis had previously filed for South Korean regulatory approval in August 2026, covering 16 indications, making it the first company to file a Keytruda biosimilar application with South Korea’s Ministry of Food and Drug Safety.

A Crowded Race to Keytruda’s Patent Cliff

The core US composition-of-matter patent protecting Keytruda’s intravenous formulation is expected to expire in December 2028 — a date that has catalyzed a wave of biosimilar development programs across the global pharmaceutical industry.

The race is heating up on multiple regulatory fronts. FYB206, a proposed pembrolizumab biosimilar co-developed by Germany’s Formycon AG and India’s Zydus Lifesciences, holds the furthest regulatory position in the United States: on October 13, the FDA accepted FYB206 for review, the first publicly announced acceptance of a pembrolizumab biosimilar BLA by the agency. That filing positions FYB206 for a potential FDA decision in the third quarter of 2027. Notably, Formycon pursued a regulatory pathway relying solely on pharmacokinetic equivalence — with FDA agreement reached in early 2025 that a full Phase 3 comparative efficacy study would not be required, giving it a potentially faster route to market.

Samsung Bioepis, filing 17 days after Formycon’s BLA was accepted, is pursuing the opposite strategy: its application rests on both a Phase 1 PK study and a full Phase 3 efficacy trial across 555 patients. The company’s bet is that a clinical dossier grounded in direct head-to-head efficacy data carries greater weight in markets — particularly the European Union and Japan — where regulators have historically placed high value on comparative clinical evidence for oncology biosimilars, and in label negotiations spanning pembrolizumab’s 40-plus approved uses.

South Korea’s Celltrion is also in the race with CT-P51, having filed an IND application with the FDA to begin a global Phase 3 trial. Cipla and China’s Qilu Pharmaceutical announced a licensing and commercialization partnership for QL2107, a pembrolizumab biosimilar candidate, in September 2026. Amgen and Sandoz have also been identified as active programs calibrated around Keytruda’s anticipated loss of exclusivity.

The competitive field is complicated, however, by Merck’s own defensive maneuvers. In September 2025, the FDA approved Keytruda Qlex, a subcutaneous formulation of pembrolizumab that administers in roughly seven minutes versus the 30-minute intravenous infusion — with its own fresh patent exclusivity that could preserve market share well into the 2030s, even after the IV patent lapses. Merck has also layered method-of-use patents around its approved indications.

What Stands Between Here and Patients: The PBM Problem

Clinical proof of equivalence and regulatory approval are necessary conditions for biosimilar success. They are not sufficient. The experience of biosimilars for other blockbuster biologics — Humira (adalimumab), Remicade (infliximab), Enbrel (etanercept) — illustrates the structural barrier that awaits: even with biosimilars priced at roughly half the reference product, biosimilar penetration across the biologics market remains below 20% in the United States.

The core obstacle is the pharmacy benefit manager (PBM) system. Branded biologic manufacturers can offer higher rebates to PBMs precisely because their list prices are higher. PBMs, in turn, structure formularies to favor rebate-generating brands, keeping biosimilar market access constrained even when payers and patients would benefit from the lower-cost alternative. The Biosimilars Forum has argued this dynamic leaves billions in potential savings unrealized. Analysts at Numerof & Associates have noted that “market access, not regulation, may be the bigger obstacle” to biosimilar adoption — a warning that applies to any pembrolizumab biosimilar regardless of how clean its Phase 3 data are.

Merck’s ability to offer bundled rebates across its broader oncology portfolio adds a further dimension to this challenge for SB27 and its competitors.

Broader Implications for Oncology Access

Checkpoint inhibitors like pembrolizumab have fundamentally reshaped cancer treatment over the past decade, extending survival for patients with previously untreatable metastatic cancers. The cost, however, has been a persistent barrier: Keytruda’s US list price runs to approximately $13,000–$14,000 per month, limiting access in many healthcare systems worldwide, particularly in lower- and middle-income countries.

Biosimilar competition, when it arrives, is expected to trigger the same type of price compression seen with other biologic blockbusters — reductions of 40% to 70% over several years of market competition. The entry of multiple pembrolizumab biosimilars around 2028 to 2029 could meaningfully broaden access to immunotherapy for cancer patients globally. Whether that compression actually reaches patients in the United States, given the PBM dynamics described above, remains a live and unresolved question.

For now, Samsung Bioepis’s SITC poster and its October 30 FDA filing together represent the most complete public evidence package assembled for any pembrolizumab biosimilar — a clinical record and an active regulatory proceeding that together signal, for the first time, that the era of Keytruda biosimilar competition is not an approaching horizon but an underway process.

Frequently Asked Questions

When will a Keytruda biosimilar be available?

Samsung Bioepis filed its US FDA Biologics License Application for SB27 on October 30, 2026. Under the Biosimilar User Fee Amendments, the FDA typically issues a decision within 12 months of filing, putting a potential Samsung decision in late 2027. Formycon and Zydus Lifesciences’ FYB206 had its BLA accepted for review on October 13, 2026, and also expects a decision in the third quarter of 2027. Keytruda’s core US composition-of-matter patent for the intravenous formulation is expected to expire in December 2028, which would open the market for biosimilar launch. If regulatory approvals land in 2027, biosimilars could reach US patients shortly after that expiry.

How much cheaper will a Keytruda biosimilar be?

Biosimilar competition has historically cut prices of branded biologics by 40% to 70% over several years of competition. Keytruda’s US list price runs to approximately $13,000 to $14,000 per month. If pembrolizumab biosimilars achieve a similar pricing trajectory, patients and health systems could eventually see per-month costs fall significantly — though actual prices will depend on market competition, payer negotiations, and pharmacy benefit manager dynamics that have kept biosimilar market share below 20% for other blockbuster biologics.

What is a biosimilar of Keytruda?

A biosimilar is a biological medicine that has been shown to have no clinically meaningful differences from an already-approved reference product. Because pembrolizumab (Keytruda) is a large, complex protein antibody rather than a simple chemical compound, it cannot be exactly replicated. Instead, a biosimilar developer must demonstrate that its version matches the reference product’s structure, pharmacokinetics, efficacy, and safety through extensive analytical and clinical testing. Samsung Bioepis’s SB27 achieved this by running both a Phase 1 pharmacokinetic equivalence trial and a full Phase 3 clinical efficacy trial — the most rigorous evidence standard in biosimilar development.

Who is developing pembrolizumab biosimilars?

Multiple companies are racing to develop Keytruda biosimilars ahead of its December 2028 US patent expiry. The leading regulatory programs are Samsung Bioepis (SB27, US BLA filed October 30, 2026) and Formycon and Zydus Lifesciences (FYB206, FDA BLA accepted for review October 13, 2026). South Korea’s Celltrion is in Phase 3 trials with CT-P51, and Cipla and China’s Qilu Pharmaceutical have announced a commercialization partnership for QL2107. Amgen and Sandoz have also disclosed active programs calibrated around Keytruda’s upcoming loss of exclusivity.

What happens when Keytruda’s patent expires?

When Keytruda’s core US composition-of-matter patent for the intravenous formulation expires in December 2028, biosimilar manufacturers that have already received FDA approval will be legally permitted to launch and sell their products. This typically triggers significant price competition: in analogous situations with other blockbuster biologics like Humira and Remicade, biosimilar entry produced price reductions of 40% to 70% over several years. However, Merck has prepared defenses: its Keytruda Qlex subcutaneous formulation, FDA-approved in September 2025, carries its own fresh patent protection and could migrate a portion of the market to a formulation where biosimilar competition will arrive later.