A number of biosimilar makers have turned to inter partes review (IPR) proceedings in order to challenge innovator patents prior to submitting their biosimilar applications to FDA. IPRs have been attractive to biosimilar makers because in addition to offering procedural and substantive advantages for challenging patents they do not require the filing of a biosimilar application. As a result, they make it possible for biosimilar makers to obtain patent certainty at a time when litigation under the Biologics Price Competition and Innovation Act of 2009 (BPCIA) is premature and, depending on the results of the IPRs, may be avoided entirely.

Boehringer Ingelheim, a company developing a biosimilar of Biogen Idec’s and Genentech’s blockbuster antibody product, Rituxan, is one of the early adopters of IPRs as an alternative to BPCIA litigation. Boehringer filed IPR petitions challenging three patents covering methods of using Rituxan. The patents are to (1) a method for treating rheumatoid arthritis according to a specific regimen in patients that do not respond to other therapy, (2) a combination of using Rituxan and methotrexate to treat rheumatoid arthritis, and (3) a method for treating low grade B-cell non-Hodgkin’s lymphoma using chemotherapy followed by administration of Rituxan according to a specific regimen. All three patents do not expire until 2020 or later.

Boehringer filed its IPR petitions in December 2014, with its proposed biosimilar still in clinical trials. So far, Boehringer’s IPR strategy has met with mixed results. Last month, the Patent Trial and Appeal Board (Board) instituted IPR (IPR2015-00417) on all claims of the first patent. But it did not institute IPR (IPR2015-00415) of half of the challenged claims of the second patent and it did not institute IPR (IPR2015-00418) of the third patent. Boehringer has requested rehearing on one of its ten rejected grounds for instituting IPR of the third patent, arguing that the Board misapprehended the prior art and abused its discretion in denying IPR. Requests for rehearing are rarely granted and even when granted, are unlikely to yield a different result. The Board’s decisions on instituting IPR are otherwise final and cannot be appealed.

Celltrion, another biosimilar maker, is trying to leverage the IPRs that have been instituted for two of the three Rituxan method patents. Like Boehringer, Celltrion is developing a biosimilar of Rituxan and has an interest in clearing the path for its product prior to filing its biosimilar application with FDA. Its product is in clinical trials and an application has not been submitted for marketing approval. Within a month of the Board’s decisions to institute IPR (the time permitted for joinder to an instituted IPR), Celltrion filed requests for IPRs (IPR2015-01733 and 1744) of the same claims of the same two Rituxan method patents on the grounds in the Board’s decisions to institute IPR and moved for joinder with Boehringer’s IPRs. In its motions for joinder, Celltrion stated that joinder will not complicate the pending IPRs because its IPR petitions are “substantially identical” to Boehringer’s and because Celltrion relies on the same exhibits and the same expert declaration as Boehringer. Celltrion also argued that it would be prejudiced if it is not permitted to join Boehringer’s IPRs because if Boehringer settles with the patent owner, the IPRs could terminate without a final decision on patentability for the claims at issue in the IPRs. In those circumstances, Celltrion would need to initiate new IPR proceedings “having lost valuable time”.

While it is clear that biosimilar makers view IPRs as appealing for clearing the path for their products (Hospira, Boehringer, Celltrion and Amgen have all filed IPRs for that reason), the mixed results from Boehringer’s IPR filings show that it is far from certain that IPRs will provide patent certainty or permit biosimilar makers to avoid litigation under the BPCIA entirely. The Board’s decision not to institute IPR for one of the patents (assuming the request for rehearing is denied) and half of the challenged claims of another leaves at least those patents for BPCIA litigation and precludes patent certainty prior to the filing of Boehringer’s biosimilar application. In addition, the Board’s decision only strengthens the claims of those patents, particularly if Boehringer’s best defenses were those advanced in the requests for IPR. But given the procedural and substantive advantages that IPRs currently provide for challenging patents, including the use of the broadest reasonable interpretation standard for claim construction, biosimilar makers are likely to continue to use IPRs to try to chip away at innovator patents prior to BPCIA litigation.