FDA Accepts the First Keytruda Biosimilar for Review

Zydus Lifesciences and Formycon AG said on October 13 that FDA has accepted for review their Biologics License Application for FYB206, a proposed biosimilar to Merck's pembrolizumab, sold as Keytruda. The companies call it the first publicly announced FDA acceptance of a Keytruda biosimilar application. The more consequential detail for regulatory strategists is what the application does not contain: a head-to-head efficacy trial against the reference product.

Why the missing trial is the story

Biosimilar sponsors have spent a decade pushing FDA to accept less clinical data than an originator biologic required, on the theory that analytical characterization — structural, functional and pharmacokinetic comparison to the reference product — can establish biosimilarity on its own for well-understood molecule classes. FDA's 2025 agreement that FYB206 would not need a comparative Phase III efficacy trial against Keytruda is a concrete application of that totality-of-evidence approach to a checkpoint inhibitor, a more complex mechanism than the first wave of biosimilars (insulins, monoclonal antibodies against well-characterized targets like TNF-alpha) that cleared without efficacy trials. Keytruda is one of the best-selling drugs in the world — trade coverage of this acceptance has put global sales near $31 billion — so a pembrolizumab biosimilar program is also a test of whether that evidentiary approach scales to oncology's highest-revenue biologic class.

What FDA accepting a BLA does, and does not, decide

Acceptance for review is a filing-completeness determination, not a biosimilarity finding. FDA confirms the application is sufficiently complete to review on the merits; it says nothing yet about whether the analytical and pharmacokinetic package will persuade reviewers during the up-to-ten-month substantive review that follows. Zydus MD Sharvil Patel framed the acceptance as a step toward broader, more affordable access to pembrolizumab therapy in the US and Canada, while Formycon CEO Stefan Glombitza described the company as among the first to advance a Keytruda biosimilar candidate to this regulatory stage — both statements about where the program stands in the process, not predictions about the outcome.

The timeline and what comes next

• Submission: the BLA for FYB206 was submitted to FDA in the third quarter of 2026.
• Filing review: FDA's BsUFA clock allows up to 60 days to confirm the application is complete enough to review.
• Substantive review: up to an additional 10 months follows, covering the analytical, nonclinical and pharmacokinetic evidence package.
• Expected decision: the companies are targeting roughly Q3 2027, consistent with a 12-month cycle from submission.

For RA/QA teams building their own biosimilar pipelines against high-revenue immuno-oncology biologics, FYB206's path through FDA review over the next several quarters is the data point to watch: whether a checkpoint inhibitor biosimilar can clear substantive review on analytical and pharmacokinetic evidence alone, without FDA requesting a clinical efficacy study mid-review. That answer will shape how aggressively other sponsors scope their own PD-1 and PD-L1 biosimilar development programs.

Frequently asked questions

What did FDA accept, and when?

On October 13, 2026, Zydus Lifesciences and its German biosimilar-development partner Formycon AG announced that FDA accepted for review their Biologics License Application for FYB206, a proposed biosimilar to Merck's pembrolizumab (Keytruda). The BLA was submitted in the third quarter of 2026. The companies describe it as the first publicly announced FDA acceptance of a BLA for a proposed Keytruda biosimilar, a characterization Regulatory News has not independently verified against every other pembrolizumab biosimilar program in development.

Why does skipping a comparative efficacy trial matter?

FDA agreed with Zydus and Formycon in early 2025 that FYB206 would not need a comparative Phase III efficacy trial against Keytruda — meaning the application instead relies on analytical similarity, pharmacokinetic and other totality-of-evidence data to support biosimilarity. That is a meaningful test case for a top-selling PD-1 inhibitor: RA teams building biosimilar programs for complex immuno-oncology biologics will watch whether FDA's review holds to that agreed scope or asks for more during substantive review.

When will FDA decide?

Biosimilar applications run on the Biosimilar User Fee Act (BsUFA) review clock: up to 60 days for an initial filing review plus up to ten months of substantive review, roughly a 12-month cycle from submission. Based on the companies' Q3 2026 submission, they expect a decision around the third quarter of 2027.

Who gets to sell it, and where?

Zydus holds exclusive commercialization rights for FYB206 in the United States and Canada. A corresponding regulatory dossier has also been formally submitted to Health Canada, according to the companies' announcement.