Background
Enanta Pharmaceuticals sued Pfizer for infringement of its patent covering compounds that inhibit coronavirus replication. Pfizer counterclaimed, arguing the patent was invalid because it could not claim priority from an earlier provisional application due to a discrepancy in the chemical range disclosed. The district court granted summary judgment for Pfizer, finding the patent invalid as anticipated by a public disclosure of a compound by Pfizer. Enanta appealed, arguing the discrepancy was a typographical error that should be corrected.
The court’s reasoning
The court applied the written description requirement of Section one thousand one hundred twelve of Title thirty-five of the United States Code to determine priority. The court found that the provisional application disclosed a chemical range of C two to C twelve alkyl, while the patent claimed C one to C twelve alkyl. The court held that the disclosure of C two to C twelve did not provide adequate written description support for C one alkyl. The court rejected Enanta’s argument that a mismatch in a general definition of alkyl constituted a typographical error in the specific disclosure. The court concluded that the provisional application did not disclose the C one alkyl group, so the patent could not claim the earlier priority date and was therefore anticipated by prior art.
What it means going forward
The decision reinforces the strict requirement that provisional applications must explicitly disclose the specific subject matter claimed in later non-provisional applications to secure priority. It limits the ability to correct apparent discrepancies in chemical ranges through expert testimony regarding typographical errors in general definitions.