The written description requirement of 35 U.S.C. § 112 can play a critical role in interferences as well as patent prosecution and litigation. In Goeddel v. Sugano, a decision that affects the scope of some DNA and protein claims, the Federal Circuit recently applied their en banc decision in Ariad to claims directed to DNA and protein sequences. Sugano had been designated the senior party in an interference based on the Board of Patent Appeals and Interferences’ (BPAI) conclusion that Sugano’s U.S. patent application was entitled to an earlier priority date of a Japanese priority application. On appeal, the Federal Circuit held that the disclosure of a protein sequence or a gene sequence encoding a protein did not necessarily describe a specific fragment of that protein. In its decision of September 7, 2010, the Federal Circuit reversed and remanded the BPAI’s decision that the disclosure of a recombinant DNA process for directly producing a naturally occurring precursor of the human fibroblast interferon (hFIF) constituted a constructive reduction to practice of a fragment of hFIF, recited in the count.

Although the earlier-filed Japanese priority application did not explicitly disclose the claimed truncated DNA or amino acid sequences, the BPAI adopted Sugano’s arguments and reasoned that one of ordinary skill in the art could have envisioned the truncated sequences. The Federal Circuit, however, noted that the claimed form of hFIF could only be produced 1) by cleavage of the precursor protein in human cells, or 2) by using a modified gene without the sequence corresponding to the cleaved amino acids. The Federal Circuit found that the procedure disclosed in Sugano’s patent application was ineffective in making active human FIF from the naturally occurring gene because the bacterial cells used could not cleave the presequence from the precursor hFIF. In holding that the patent application did not satisfy the written description requirement, the Federal Circuit stated that “[t]he question is not whether one skilled in this field of science might have been able to produce mature hFIF by building upon the teachings of the Japanese Application, but rather whether that application convey[ed] to those skilled in the art that the inventor had possession of the claimed subject matter as of the filing date.”

Conclusion and Application. This decision emphasizes that if fragments are contemplated or of interest, the patent application needs to specifically disclose the corresponding truncated sequences and/or methods for making the fragments associated with truncated sequences for the purposes of establishing written description in the U.S. for claims directed to such sequences or fragments. In addition, this case serves as a reminder that patentees should not rely on what might be known by those of skill in the art to satisfy the written description requirement, which is not met even where the claimed subject matter would be obvious to one of skill in the art from the disclosure.