Board Reverses An Obviousness Rejection For Examiner's Failure To Provide Adequate Rationale For Substituting Substances Having Different Functions

May 4, 2012 – Blog Post

In Ex parte Sawada et al. (Appeal 2011-007934; Application serial no. 09/834,410), the Board reversed an obviousness rejection based on a combination of prior art because the Examiner did not adequately explain why it would have been obvious to substitute substances that had different functions in the respective drug formulations.

The claim at issue was directed to a timed-release compression-coated solid composition and recited an outer layer comprising polyethylene oxide. The primary reference, Giannini, lacked teaching of such an outer layer comprised of polyethylene oxide, and instead described a composition having a coating comprising ethylcellulose. The Examiner relied on the secondary reference, Sako, describing a drug coating comprising polyethylene oxide, and took the position that it would have been obvious to substitute ethylcellulose of Giannini with polyethylene oxide as taught by Sako.

The Board found that “the Examiner has not adequately explained why one of skill in the art would have substituted the polyethylene oxide of Sako for the ethylcellulose of Giannini,” noting that the two substances had different functions in the respective formulations. Specifically, the Board explained that “the ethylcellulose in Giannini’s granules was intended to be a part of a taste-mask coating for an immediate release preparation, while the polyethylene oxide of Sako is combined with the active agent and [polyethylene glycol] so that a sustained release gel encompassing the active agent is formed upon administration.”

According to the Board, there was another flaw in the obviousness rejection. Sako described a homogeneous mixture of drug, hydrophilic base and hydrogel-forming polymer, but the Examiner incorrectly found that Sako disclosed a drug core tablet coated with a mixture of hydrophilic base and hydrogel-forming polymer.