Addressing whether a patented claim for a formulation was obvious to try, the district court on a motion for summary judgment held that the claim was nonobvious where several prior art references resulted in numerous approaches to a problem and was thus less “obvious to try.” Valeant Pharm. Int’l Inc. v. Mylan Pharm. Inc., Case No. 15-8180, 2018 (D.N.J., May 1, 2018) (Chesler, J).

Valeant Pharmaceuticals International, Inc., and Wyeth LLC (collectively, plaintiffs) owned US Patent No. 8,552,025, which covers Valeant’s drug Relistor (methylnaltrexone). Several generic drug makers (defendants) sought to make and sell a generic version of Relistor prior to the expiration of the relevant patents, and this Hatch-Waxman suit was initiated. 

At issue in this motion for partial summary judgment was claim 8 of the ’025 patent. The disputed claim element is a pharmaceutical parenteral formulation of methylnaltrexone in saline at a pH range of 3.0–4.0 with 24 months stability at ambient conditions. The plaintiffs moved for partial summary judgment of no invalidity. The defendants asserted that the claimed pH range of 3.0–4.0 was obvious to try due to prior art with an overlapping pH range of 3–7 for solutions of naloxone and naltrexone. The defendants also introduced numerous prior art references to prove that adjusting the pH parameter of a formulation would have been obvious to try, since pH is one of many commonly adjusted formulation parameters to enhance stability, and prolonged stability is typically desirable.

In response, the plaintiffs relied on the prior art’s failure to teach that an acidic pH alone was responsible for improving the stability of a formulation using a naloxone or naltrexone. In the plaintiffs’ view, there was no motivation to combine prior art, which specifically taught that stabilizers or chelating agents, rather than pH, improved the stability of acidic solution formulations of naloxone derivatives. Moreover, none of the prior art formulations resulted in stability out to 24 months.

The court granted plaintiffs’ motion for partial summary judgment that the patent was not invalid as obvious because using the claimed pH range of 3.0–4.0 to achieve 24 months stability in light of prior art was unpredictable. The court ruled that the overlapping pH ranges were not obvious because the claimed pH range applies to methylnaltrexone, a quaternary amine, while the prior art pH range applies to naloxone and naltrexone, both tertiary amines that are different molecules from the patented claim. Also, achieving 24 months stability at ambient conditions by adjusting pH alone was not a predictable result because the prior art provided many approaches to improve formulation stability in addition to pH, including stabilizers, antioxidants, chelating agents, container closure and preservatives, without specific guidance to adjust pH. None of the prior art taught adjusting a formulation’s pH to improve stability, but rather recommended the use of chelating agents.

Practice Note: To defeat summary judgment on obviousness, raise a dispute of fact using secondary considerations, since these are fact based. The court must consider secondary considerations in its obviousness analysis. Also, asserting too many prior art references may result in cumulatively more options for an inventor to pursue and would thus make the claimed invention nonobvious.