FDA Accepts BLA for Formycon and Zydus’ FYB206, the First Publicly Announced Keytruda Biosimilar Under Review

The FDA has accepted for review the biologics license application (BLA) for FYB206, Formycon AG’s proposed biosimilar to Merck’s pembrolizumab (Keytruda). Formycon and its partner Zydus Lifesciences announced the acceptance on Oct. 13, 2026.¹ The companies said that, to the best of their knowledge, it is the first publicly announced FDA acceptance of an application for a Keytruda biosimilar.¹ FYB206 reached this stage without a comparative phase 3 efficacy trial, following a development pathway Formycon agreed on with FDA in early 2025.¹

What did FDA accept for review?

Pembrolizumab is an immune checkpoint inhibitor used to treat numerous types of cancer. It binds to and blocks the programmed cell death protein 1 (PD-1) receptor.¹ Formycon submitted the FYB206 BLA in the third quarter of 2026. Under the Biosimilar User Fee Amendments, FDA aims to complete its review within 12 months of submission. That window includes up to 60 days for the filing review and 10 months for the substantive review. Based on this timeline, the companies said a decision could be expected in the third quarter of 2027.¹ Formycon has also submitted the regulatory dossier to Health Canada.¹

How was FYB206 developed without a phase 3 trial?

In February 2025, Formycon agreed with FDA that FYB206 would not require a comparative phase 3 efficacy trial. According to the company, such trials had long been standard for monoclonal antibody biosimilars, typically take one to three years, and involve hundreds of patients.¹ Instead, development relied on a comprehensive analytical and functional comparability package and the pivotal Dahlia pharmacokinetic (PK) study. Dahlia met its primary objective in February 2026, demonstrating PK equivalence between FYB206 and the reference product, and clinical development was completed in July 2026.² Formycon expects that forgoing the phase 3 trial will save investments in the high double-digit million euro range.¹

“We developed FYB206 on a path agreed with the FDA, without conducting a comparative Phase III efficacy trial. This enabled us to accelerate the program and substantially reduce development investment while maintaining the rigorous scientific standards required for biosimilar approval,” said Stefan Glombitza, PhD, chief executive officer of Formycon, in the press release.¹

On Oct. 29, 2025, FDA issued draft guidance proposing that comparative efficacy studies may not be needed in some cases. That applies when a comparative analytical assessment of attributes such as protein structure and physicochemical and functional properties shows that a proposed biosimilar is highly similar to its reference product.³ The draft guidance says sponsors should consider this streamlined approach under three conditions.⁴

• Both products are manufactured from clonal cell lines, are highly purified, and can be well characterized analytically.
• The relationship between quality attributes and clinical efficacy is generally understood.
• A human PK similarity study is feasible and clinically relevant.

As BioPharm International® previously reported, FDA has also proposed reducing switching-study requirements for interchangeable biosimilars.

That reliance on analytical comparability reflects a core difference in biosimilar development. “Process development for biosimilars differs from other biologics and small-molecule drugs primarily due to the need to demonstrate high similarity to an existing reference product,” said Zara Bukhari, a PhD scholar at the University of the Pacific, in a Q&A with BioPharm International.

Other pembrolizumab biosimilar programs have taken a different route. mAbxience’s BENITO study is a randomized, double-blind trial comparing the PK, efficacy, safety, and immunogenicity of its candidate MB12 with Keytruda. It enrolls patients receiving chemotherapy for stage IV nonsquamous non-small cell lung cancer and is listed as active, not recruiting.⁵ Cipla’s partner Qilu Pharmaceutical is also running a phase 3 trial of its pembrolizumab biosimilar QL2107 in the same indication.

What are the commercialization terms?

Formycon and Zydus signed an exclusive licensing and supply agreement for FYB206 in the US and Canada in December 2025.¹ Formycon is responsible for completing development, preparing and filing the regulatory dossiers, and supplying the product. FDA’s acceptance of the BLA triggers a milestone payment from Zydus.¹ Zydus will commercialize FYB206 in both markets, subject to regulatory approval and resolution of any intellectual property issues.¹ Formycon holds global rights to FYB206 and will share in its commercialization partners’ gross profits. It has partnered the candidate with MS Pharma for the Middle East and North Africa and with Lotus for parts of Asia-Pacific. Partnering talks are ongoing for other regions, including Europe and Latin America.¹

What happens next?

FYB206 remains investigational, and regulators have not established its biosimilarity.¹ If approved, it would enter the market for the world’s best-selling biologic. Worldwide sales of Keytruda, including the subcutaneous formulation Keytruda Qlex, reached USD 31.7 billion in 2025. Combined sales totaled USD 16.4 billion in the first half of 2026.¹

References

1. Formycon AG. Formycon and Zydus: FYB206 Becomes First Publicly Announced Keytruda® Biosimilar Accepted for Review by FDA. Press release. Published October 13, 2026. Accessed October 13, 2026.
2. Capsius B, Pesic M, Niyazov R, et al. From reflection to implementation: tailored clinical development of a pembrolizumab biosimilar candidate. BioDrugs. Published online September 19, 2026. Accessed October 13, 2026. doi:10.1007/s40259-026-00803-y
3. Jones Day. FDA Proposes to Remove Comparative Efficacy Studies to Accelerate Biosimilar Development. Published November 2025. Accessed October 13, 2026.
4. Akin. FDA Issues Draft Guidance with Updated Recommendations for Assessing the Need for Comparative Efficacy Studies in Biosimilar Development. Published November 5, 2025. Accessed October 13, 2026.
5. ClinicalTrials.gov. A Study to Compare Pharmacokinetics, Efficacy, Safety, and Immunogenicity of MB12 (Proposed Pembrolizumab Biosimilar) to Keytruda® in Non-small Cell Lung Cancer (BENITO Study). NCT06687369. Accessed October 13, 2026.