Enablement of Transgenic Plant Inventions

A US patent document must provide a description of the patented invention that is adequate to enable a person of ordinary skill in the art to make and use the claimed invention (35 U.S.C. §112, 1st). The enablement requirement seeks to ensure that patentees provide high-quality teachings that correlate in scope with the scope of the potentially valuable patent rights that they receive; as such, enablement is an essential part of the quid pro quo of the patent system ( in re Wright, Enzo Biochem, Inc. v Calgene , p. 1561). Courts have established that a patent document satisfies the enablement requirement even if ordinary artisans would need to undertake some experimentation in order to make or use a patented invention, as long as experimentation is not deemed to be ‘undue’ ( in re Vaeck ). Courts have to balance a number of factors when determining whether experimentation is undue for enablement purposes, including the often critical factor of predictability in the art ( in re Wands ). The Federal Circuit has identified biotechnology as one of the unpredictable arts for enablement purposes, though it has also recognized that assessments of predictability should be revised as science advances ( in re Wright, Enzo Biochem, Inc .). Relatedly, the Federal Circuit observed, in a biotechnology enablement case, that the enablement requirement should be applied with particular vigour in ‘nascent technologies’ ( Chiron v Genentech ). Courts have also held that the enablement inquiry must be undertaken in view of the state of the art as it existed at the time when the inventor filed the patent application ( in re Goodman ).

An issued patent is presumed to comply with the enablement requirement, a consequence of the general presumption of validity accorded to all issued patents (35 U.S.C. §282). Patent challengers bear the burden of proving a failure of enablement, and must establish the relevant facts by the standard of clear and convincing evidence in order to overcome the presumption of validity ( Chiron , p. 1252).

In a series of cases, the Court of Appeal for the Federal Circuit (the most important US court on patent law matters) has applied the enablement requirement to transgenic plant inventions. In Adang v Fischoff , an appeal from an interference proceeding, in which two inventors, Adang and Fischoff, both claimed rights to the same invention, the court analysed the validity of the following interference count:

A tomato plant which has been regenerated from a tomato plant cell transformed to comprise a full length Bacillus thuringiensis crystal protein gene capable of encoding a Bacillus thuringiensis crystal protein of about 130 kD under control of a promoter such that said gene is expressible in said plant in amounts insecticidal to Lepidopteran insects.

Adang’s patent specification included an example reporting the transformation of tobacco cells with a Bt gene having the characteristics called for in the count, and a list of 94 types of plants (including tobacco and tomato) described as being capable of being transformed by Bt crystal protein genes.

The court concluded that the disclosure did not enable the count. References from the technical literature, even after the filing date of Adang’s application, showed that attempts to incorporate a full-length Bt crystal protein gene into various strains of tobacco plants using Agrobacterium -mediated transformation failed to produce stable transformations or predictable insect toxicity – and in some instances failed even to produce viable plants. Although both Adang and Fischoff had submitted expert evidence (testimony and new experimental evidence), Fischoff ’s was more credible; Adang’s seemed to be based on hindsight. The court upheld the conclusion of the US Patent and Trademark Office (PTO) that it would have required undue experimentation on the part of a worker of ordinary skill to use the Adang disclosure to transform and produce a transgenic tomato plant within the scope of the interference count ( Adang , pp. 1355–1358).

In Plant Genetic Systems v DeKalb Genetics , the patent in suit claimed a transformed ‘plant cell’:

1. A plant cell having a heterologous DNA stably integrated into its genome; said DNA comprising a heterologous DNA fragment encoding a protein having an acetyl transferase activity which inactivates a glutamine synthetase inhibitor in said cell.

The patent disclosed working examples involving the Agrobacterium -mediated transformation of tobacco, tomato, sugarbeet and potato plants – all dicots. Yet the term ‘plant cell’ in claim 1 arguably covered not only dicots, but also monocots (such as DeKalb’s transgenic corn varieties). Likewise, claim 1 arguably covered any transformation technique. The enablement issue was whether the disclosure would have enabled a person of ordinary skill in the art to employ any transformation technique, including Agrobacterium -mediated transformation, to transform any plant cells, including monocot plant cells, as of the 1987 application filing date.