Background
Juno Therapeutics and Sloan Kettering Institute held U.S. Patent No. 7,446,190, which claimed nucleic acid constructs encoding chimeric T-cell receptors — the molecular components at the heart of CAR-T cell therapy, a revolutionary form of cancer immunotherapy. The asserted claims were written broadly in functional terms, covering any single-chain variable fragment (scFv) that would bind to a target antigen and trigger T-cell activation, without specifying the structural features needed to define the many possible scFvs that could perform that function.
Kite Pharma — a competitor that developed the CAR-T therapy Yescarta — was sued for infringement. A jury found infringement and awarded Juno $1.2 billion in damages, one of the largest patent verdicts in the history of biotechnology. Kite appealed, arguing that the patent’s claims were invalid for lack of written description because the specification disclosed only a handful of specific scFv examples but claimed the full functional space of all possible scFvs that could perform the recited function.
The Court’s Holding
The Federal Circuit reversed. Chief Judge Moore, writing for the panel, held that the jury’s finding that the claims satisfied the written description requirement was not supported by substantial evidence. The court applied the principle — well established in biotech patent law — that a claim to a genus of functionally defined molecules requires the specification to either disclose a representative number of species spanning the breadth of the genus or to identify common structural features shared across the genus that correlate with the claimed function.
The ‘190 patent’s specification disclosed only a small number of specific scFv examples and did not identify any structural characteristics that defined which scFvs would perform the claimed T-cell activation function. The claimed functional genus was vast — potentially covering millions of molecular variants — yet the specification described only a narrow subset. Because the inventors could not have possessed the full scope of what they claimed at the time of filing, the written description requirement was not satisfied, and the claims were invalid. The $1.2 billion verdict was vacated.
Key Takeaways
- Broad functional claims over a genus of biological molecules require the specification to describe either a representative number of species spanning the genus, or the structural features common to the genus that correlate with the function — examples alone are not enough if the genus is vast.
- The written description requirement under 35 U.S.C. § 112(a) is not satisfied merely by claiming a function; the patent owner must demonstrate possession of the full scope of the claimed genus at the time of filing.
- In biotech and pharma, broad genus claims using functional language are particularly vulnerable to written description challenges unless the specification provides robust structural disclosure across the claimed space.
- Patent applicants in CAR-T, antibody, and similar biological fields should include structural data for multiple examples and, if possible, identify common structural determinants of the claimed function.
Why It Matters
Juno v. Kite was one of the most consequential patent decisions in the history of the CAR-T industry. The reversal of a $1.2 billion verdict underscored the existential risk that written description challenges pose to biotech companies whose patent portfolios rely on broad functional claims. The ruling sent a clear signal that the Federal Circuit would apply the genus written description standard rigorously, even in blockbuster cases where the underlying technology is genuinely transformative.
For the CAR-T field specifically — where multiple companies spent years and billions of dollars developing therapies based on similar molecular architectures — the decision changed the competitive landscape. It also prompted a widespread review of biotech patent prosecution strategies: drafting claims that cover a full functional genus while providing structural specificity in the specification has become essential. The case is now cited alongside Ariad Pharmaceuticals v. Eli Lilly as a foundational text on the written description requirement for genus claims in the life sciences.