MEMORANDUM ORDER

SUE L. ROBINSON, District Judge.

At Wilmington this 7th day of March, 2016, having reviewed yet another round of evidentiary disputes presented by the parties to the above litigation;

IT IS ORDERED that:

1. Defendants' evidentiary issues 10-11. Defendants seek to preclude Amgen from referring to "post-priority date, non-prior art antibodies and fragments to rebut [d]efendants' obviousness defense." (D.l. 254 at 1) In support of their position, defendants state that the court "has already ruled that post-priority date antibodies cannot be used as evidence of pre-priority motivation," and that the parties have "also agreed that post-priority evidence cannot be used as evidence related to reasonable expectation of success." (Id.) According to defendants, "[t]he converse should also apply, namely that Amgen cannot rely on post-priority date evidence to rebut motivation." (Id.)

2. Plaintiffs counter that defendants have based their obviousness case on the Novartis and Schering PCT applications and their expert's opinion that "the PCT applications' disclosures create motivation and an expectation of success in developing the patent antibodies — stating sixteen times in his expert report that the techniques disclosed would `inevitably' lead to the Amgen patents." (D.I. 259 at 1) (emphasis in original) The real world evidence, however, is that "the Novartis team of skilled scientists, following the supposed `obvious' pathway to Amgen's antibodies, in fact developed a different antibody outside the scope of Amgen's claims." (Id.)

3. Although it remains difficult to draw reasonable evidentiary lines in this litigation and stick to them, I conclude with respect to this particular evidentiary dispute that plaintiffs may use the real world facts as impeachment of Dr. Ravetch and his theory of inevitability, as opposed to independent evidence of nonobviousness; i.e., no extrinsic evidence of the Novartis efforts will be admitted.1 To the extent documents are admitted, they are admitted for all purposes consistent with the way the case was pretried, as explained below.

4. Defendants' evidentiary issues 12-13. I agree with defendants that plaintiffs' experts are limited to the scope of their expert reports vis a vis secondary considerations of non-obviousness. Consistent with the above, plaintiffs' experts may not discuss the Novartis and Schering applications absent consent from the court based on the specific context of how the obviousness issues have been presented.

5. Dr. Stahl's proffer. Dr. Stahl will not be permitted to testify during the liability phase of the trial. His proffered testimony is that of an expert witness, not a fact witness, and the content of such testimony — particularly what was known to Regeneron during the development of Praluent® — is not relevant to the sole issue presented by defendants, that of obviousness based on two prior art references. The wide-ranging proffer will unfairly prejudice plaintiffs, and confuse and mislead the jury.2 Defendants' corporate representative will be introducing the companies and their product generally.