District court did not err in finding a limitation inherently present in the prior art. Extrinsic evidence can be used to show what is 'necessarily present' in a prior art embodiment even if the extrinsic evidence is not itself prior art. Also, if a property of a composition is in fact inherent, there is no question of a reasonable expectation of success in achieving it.
Moreover, "[i]t is well-settled that the inclusion of an inherent, but undisclosed, property of a composition does not render a claim to the composition nonobvious."
Read the case here.