The teachings of a later prior art reference generally outweigh contradictory statements in an earlier prior art reference. Here, for example, although an earlier prior art reference clearly taught away from the claimed invention by stating that the claimed “5-MTHF” compound would be too unstable for therapeutic use, a later prior art reference stating that “[a] new and stable preparation of MTHF has become available for clinical trials” was found to outweigh the teachings of the earlier prior art reference on the whole. “[T]he prior art must be considered as a whole.” This would be a good case to consult before responding to an obviousness rejection by citing other and older contrasting references.
Background / Facts: The patent on appeal here from rejection at the PTO during inter partes review (IPR) proceedings is directed to methods of using folates, including the claimed 5-methyl-tetrahydrofolic acid (5-MTHF), to lower levels of homocysteine in the human body. The prior art applied by the PTO identifies L-5-MTHF as a “natural metabolite” that may be used “as at least one active compound” in a treatment for folate deficiency. Other prior art cited by the patentee, however, states that “[a]lthough [5-MTHF] would be desirable for use in therapy, it is probably too unstable.”
Issue(s): Whether the prior art as a whole teaches away from the claimed invention by suggesting that 5-MTHF would be too unstable for therapeutic use.
Holding(s): No. “The [other] references [cited by the patentee], published in 1981 and 1983 respectively, certainly suggest 5-MTHF was unstable. … But subsequent references disclose that 5-MTHF is suitable for pharmaceutical use. A study published in 1986 explains that although prior ‘[s]tudies of MTHF … were hampered by its chemical instability[,] [a] new and stable preparation of MTHF has become available for clinical trials.’… Because the prior art must be considered as a whole [], the Board’s finding that a person of ordinary skill would not have thought that 5-MTHF was too unstable for pharmaceutical use is supported by substantial evidence.”