In its affirmance of a Patent Trial and Appeal Board Final Written Decision, a Federal Circuit panel held that a reference is a work “by another” when a named co-inventor is the sole inventor of a prior art invention and is not “one’s own work” because the reference is authored by fewer than all of the named inventors. In Merck Serono S.A. v. Hopewell Pharma Ventures, Inc., Case 25-1210 (Fed. Cir. Oct. 30, 2025), Hopewell filed an IPR petition seeking unpatentability determinations for two method of use patents directed to the treatment of multiple sclerosis (MS). The patents arose from a joint effort between Serono (acquired later by Merck) and Ivax Corporation to develop oral cladribine to treat MS. Within the one year prior to the filing of the challenged patents, named inventor Bodor, then an employee of Ivax, filed a patent application also claiming a treatment for MS which, in the view of the Board, when combined with the earlier published Stelmasiak reference, rendered the challenged claims unpatentable.

The Court stated that “the question presented to us in this appeal is whether and to what extent a disclosure invented by fewer than all the named inventors of a patent may be deemed a disclosure ‘by another’ and thus included in the prior art, or whether the disclosure should properly be treated as ‘one’s own work’ and therefore excluded from the prior art.” Examining the facts, the Court noted that the there was “no indication that the portions of the references relied on disclose anything they did jointly,” and held that “[w]hat should also be clear is that when the patented invention is the result of the work of joint inventors, the portions of the reference disclosure relied upon must reflect the collective work of the same inventive entity in the patent to be excluded as prior art.” (Slip op. at 21). 

The Court offered the following that serves as a practice pointer: “Any incongruity in the inventive entity between the inventors of a prior reference and the inventors of a patent claim renders the prior disclosure ‘by another,’ regardless of whether inventors are subtracted from or added to the patent.” (Slip op. at 21-22). Patent applicants need to pay particular attention to inventorship determinations and ensure that proof of co-invention, where possible, exists for both a prior disclosure and a later patent application.