Obviousness

As a technical patent analyst, I have analyzed the obviousness of US patent 10947555B2 under 35 U.S.C. § 103, building on the previously established prior art. The legal standard for obviousness requires determining whether the differences between the claimed invention and the prior art would have been obvious to a person having ordinary skill in the art (POSA) at the time of the invention. This includes considering motivations to combine prior art references and a reasonable expectation of success.

The independent claims of US 10947555B2 (Claims 1, 17, 18, 19, and 20) center on a transgenic plant cell, plant, and seed resistant to both 2,4-D and aryloxyphenoxypropionate (AOPP) herbicides, due to the expression of a plant-optimized aryloxyalkanoate dioxygenase (AAD-1) polypeptide (having at least 95% amino acid sequence identity to SEQ ID NO: 11) that degrades both herbicide classes. The methods claims (19, 20) involve applying these two classes of herbicides to such plants or seeds.

The patent itself highlights that AAD-1 (derived from rdpA) exhibits a "surprisingly" novel property of degrading both phenoxy auxin and AOPP herbicides, noting that "No α-ketoglutarate-dependent dioxygenase enzyme has previously been reported to have the ability to degrade herbicides of different chemical classes and modes of action." This statement presents a direct challenge to any obviousness argument regarding the dual resistance.

However, an obviousness argument can be constructed based on the following combination of prior art:

Prior Art References:

1. Westendorf et al. (2002, 2003): These references disclosed the rdpA gene from Sphingobium herbicidovorans (the precursor to AAD-1) and demonstrated that its encoded enzyme degrades 2,4-D and (R)-dichlorprop (both phenoxy auxin herbicides) in vitro.
2. Streber et al. (1989), Lyon et al. (1989), Lyon (1993), and U.S. Pat. No. 5,608,147: These references taught the successful use of tfdA-type genes to confer 2,4-D resistance in transgenic dicot plants (e.g., cotton and tobacco). This established a clear precedent for expressing bacterial dioxygenase genes in plants to achieve herbicide resistance.
3. General Knowledge in Agricultural Biotechnology: A person of ordinary skill in the art would have been aware of:
   • The increasing problem of weed resistance to widely used herbicides, such as glyphosate, and the consequent need for new herbicide resistance traits and diversified weed control strategies.
   • Standard molecular biology techniques for isolating genes, plant codon optimization to enhance expression in specific plant hosts, and methods for plant transformation and regeneration.
   • The commonality of "aryloxyalkanoate chemical substructures" in various herbicide classes, including phenoxy auxins (like 2,4-D and dichlorprop) and aryloxyphenoxypropionates (AOPPs).

Motivation to Combine and Obvious to Try:

A POSA, motivated by the ongoing challenge of herbicide-resistant weeds and the desire to develop new or improved herbicide-tolerant crops with broader resistance spectrums (Reference 3), would have looked for alternative or more broadly effective herbicide degradation genes.

1. Expression of rdpA for 2,4-D Resistance in Plants: Given that tfdA-type genes were successfully employed to confer 2,4-D resistance in plants (Reference 2), and rdpA (AAD-1) was known to degrade 2,4-D in vitro (Reference 1), a POSA would have had a clear motivation and a reasonable expectation of success to express rdpA in plants to confer 2,4-D resistance. This would involve routine steps of gene isolation, plant-optimization of the coding sequence for enhanced expression (Reference 3), and standard plant transformation techniques.

2. Anticipation of AOPP Degradation (Obvious to Try): While the patent asserts the AOPP degradation activity was surprising, a POSA, aware of rdpA's activity on phenoxy auxins (which contain aryloxyalkanoate substructures) and the fact that AOPP herbicides also share these "aryloxyalkanoate chemical substructures" (Reference 3), could have been motivated to undertake a screening effort. In the context of developing broader herbicide resistance for crops (Reference 3), it would have been an "obvious to try" approach to test the substrate specificity of a known aryloxyalkanoate-degrading enzyme (like rdpA) against other herbicide classes containing similar structural motifs, such as the AOPPs. Even if the success of degrading AOPPs was not guaranteed or expected to be as robust as found, the motivation to try to expand the enzyme's known specificity to related chemical classes for potential agronomic benefit would have existed.

Therefore, the combination of:

• The known in vitro activity of rdpA on phenoxy auxins (Reference 1);
• The established success of expressing similar genes (tfdA) for in planta 2,4-D resistance (Reference 2); and
• The general motivation to develop broad-spectrum herbicide resistance in crops, coupled with the recognition of common chemical substructures in both phenoxy auxins and AOPPs (Reference 3),
  would have rendered the invention of a plant cell, plant, or seed with AAD-1 conferring resistance to both 2,4-D and AOPP herbicides obvious to a POSA. The methods claims (19, 20) would similarly be obvious as they describe using these resistant plants with the herbicides to which they are resistant. The "plant-optimized" nature of the nucleic acid in Claim 1 further aligns with routine practices in plant biotechnology (Reference 3).

The PTAB challenges (IPR2024-00179 and IPR2023-01036) are scrutinizing claims 1-34 based on prior art, and their ultimate decisions will be crucial in determining whether this "unexpected result" argument overcomes an obviousness challenge rooted in the "obvious to try" doctrine given the structural similarities and known enzymatic activity.