PTAB Invalidates Two Anacor KERYDIN® Patents

By Olga Schwier, Ph.D. and Cary Miller, Ph.D.

The PTAB found obvious all claims of U.S. Patent Nos. 7,582,621 and 7,767,657 in the three final written decisions issued on February 23, 2017 (IPR2015-01776, IPR2015-01780, and IPR2015-01785).  This marks another victory for Coalition for Affordable Drugs (CFAD) — the petitioner in all three IPRs.

Anacor Pharmaceuticals (Anacor) owns both challenged patents, which are listed in the Orange Book for KERYDIN® (tavaborole) — a topical antifungal treatment of toenail onychomycosis.  The ’621 patent claims methods of treating an infection using tavaborole, while the ’657 patent claims pharmaceutical formulations of tavaborole.

The PTAB invalidated the ’621 patent claims over the combination of patent publications Austin and Brehove as well as the combination of Austin and Freeman.  The majority of the ’657 patent claims were also found obvious over these reference combinations, while the remaining claims were invalidated over these publication pairs in view of other references.

Austin relates to the use of boron compounds as industrial biocides — it teaches that tavaborole, a small boron-containing molecule, has antifungal activity against C. albicans and describes certain biocide compositions.  Brehove relates to the topical treatment of nail infections — it explains that onychomycosis can be caused by C. albicans and teaches a method of treatment of onychomycosis using certain boron-containing compounds along with their topical formulations.  Freeman discloses boronic acids used for treating fungal infections and their formulations.

Anacor failed to convince the PTAB that Austin’s biocide disclosure was not analogous art.  It argued that “medicinal chemists would not look to industrial biocides for pharmaceutical leads because the requirements for a useful biocide are different from the requirements for a useful drug.”  The Board found Austin pertinent as “[b]oth the inventors and Austin sought to inhibit microorganisms, including C. albicans” and stated that “a person of ordinary skill in the art would have recognized that industrial fungicides may have therapeutic uses, including in some cases, topically treating a human for C. albicans.”

Likewise, Anacor did not convince the Board that an ordinary artisan would have found Brehove non-credible.  According to Anacor, Brehove lacked certain test and data details — e.g., it did not confirm clinical diagnosis of onychomycosis, omitted certain safety warnings, erroneously identified C. albicans as the most common cause of onychomycosis, and described certain experiments that were contradicted by another study.  Moreover, Anacor insisted that an ordinary artisan would have viewed Brehove’s examples as prophetic and argued there would not have been a reasonable expectation of success.

The PTAB was not persuaded that the alleged inaccuracies, unexplained data, and prophetic examples detracted from the teachings of Brehove.  The Board found that “Brehove is a patent application that does not need to meet the standard of a peer-reviewed academic article” — “[t]here is no requirement . . . that Brehove provide details regarding background tests, data, and long-term toxicity reports, to be credited as results by a person of ordinary skill in the art.”  The PTAB also noted that Anacor’s own ’657 patent did not report toxicity data.  Moreover, pointing to the expert testimony, the Board found that it was reasonable to assume that onychomycosis diagnosis was done in Brehove’s experiments and that the reference described an effective onychomycosis treatment.

Secondary consideration arguments were once again unsuccessful in these three IPRs.  The PTAB was not persuaded by Anacor’s assertion that tavaborole’s selective toxicity for fungal cells was unexpected, noting that Anacor failed to identify the closest prior art and explain why such selectivity was unexpected.  Anacor also lost on its “long-felt but unmet need” argument because KERYDIN® had activity similar to another treatment (PENLAC®), which Anacor had criticized for being barely more effective than a placebo.  Finally, the PTAB rejected Anacor’s “industry praise” argument, noting that the statements cited by Anacor were just “recognition of yet another approved treatment regime” which did not overcome the evidence of obviousness.