Orexo AB v. Sun Pharm. Indus. Ltd.

Zubsolv® (buprenorphine/naloxone)

July 12, 2023

GENERICally Speaking

Case Name: Orexo AB v. Sun Pharm. Indus. Ltd., Civ. No. 20-12588 (GC/DEA), 2023 WL 4492095 (D.N.J. July 12, 2023) (Castner, J.)

Drug Product and Patent(s)-in-Suit: Zubsolv® (buprenorphine/naloxone); U.S. Patents Nos. 9,439,900 (“the ’900 patent”) and 11,020,387 (“the ’387 patent”)

Nature of the Case and Issue(s) Presented: Orexo sued Sun based on its ANDA seeking to make and sell generic Zubsolv. Formulators developed Zubsolv to improve upon Suboxone® (also buprenorphine/naloxone), specifically, to formulate a drug with improved buprenorphine bioavailability. The asserted patents issued “because [the] formulation of Zubsolv® unexpectedly, and significantly improved bioavailability compared to the prior-art Suboxone®.” The court cited the drug’s ingredients and structural characteristics. The critical issue was whether Sun’s formulation, and/or the prior art, satisfied claim limitations reciting separate buprenorphine and weak acid particles. After a bench trial, the court issued findings of fact and conclusions of law finding that Sun’s ANDA products would infringe the valid asserted claims of the patents-in-suit.

Why Orexo Prevailed: With respect to infringement, in sum, the court did not find Sun’s expert persuasive, noting that Sun’s process “seems consistent with the [asserted patents’] specification.” In crediting Orexo’s expert over Sun’s on the separate particles issue, the court found that Orexo had proven infringement. Orexo also offered separate Raman and SEM evidence and testimony to show that Sun’s ANDA products met the separate particles limitation. Sun’s expert disagreed with the Raman and SEM results and opined that he saw “a composite particle based on his years of experience looking.” But again, the court credited Orexo’s expert. In particular, the court noted that Sun’s expert had not cited any academic literature to support certain opinions, nor did he perform his own Raman or SEM testing, nor did he review the electronic Raman data underlying Orexo’s expert’s work, because he did not have “the exact software package.” Important, the court noted—and Sun’s expert agreed—that the patent did not have to disclose all methods of testing for infringement. Finally, though the court did not rely on Sun’s PK data or its bioequivalence studies, the court did find that Orexo’s additional pH testing further supported a “separateness” finding and, thus, infringement.

With respect to validity, at trial Sun argued that the asserted claims were indefinite, lacked adequate written description, not enabled, and obvious. The court found that Sun had not proven invalidity under any of its theories. Sun’s indefiniteness argument—tethered to the separate particles limitation—failed because contrary to its arguments, all testing pointed in the same direction. Sun failed “to show how different tests lead to different infringement conclusions,” and the court instead found “that the different tests support the same infringement conclusion.”

Sun’s written description argument also failed. Sun argued that the specification disclosed only one way—and not Sun’s way—to achieve separate particles. But the asserted claims were composition claims, not method claims. Thus, the written description requirement does not demand that all methods of making the product, including those followed by Sun, be described in the specification. Sun’s enablement argument failed for a similar reason (“For product claims, such as those asserted here by virtue of the now-governing broad claim construction, the enablement requirement is satisfied if the specification provides a single way to make the claimed product.”).

Finally, the court determined that Sun had not met its burden in proving obviousness. First, Sun’s asserted references were before the Examiner during prosecution. Second, Sun did not demonstrate that the combined references disclosed all limitations of all asserted claims—in particular, that the weak acid particles are separate from buprenorphine microparticles, or the claimed dosage strengths. Perhaps most significant, the court determined that Sun had not shown a motivation to combine or a reasonable expectation of success—POSA did not have clear guidance on how to improve buprenorphine bioavailability in a sublingual tablet during the opioid crisis. The art “would not motivate a POSA to combine to get separate and distinct buprenorphine microparticles and a weak acid as claimed in the asserted patents with reasonable success.” Moreover, the court determined that Orexo had shown that Zubsolv®’s increased bioavailability was unexpected, and that there is a nexus between the increased bioavailability and the claimed inventions. The court also found evidence of unexpected patient preference (Zubsolv® over Suboxone®) and industry praise.

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