Federal Circuit Contrives Substantially Similar Written Description Test

27 August 2019 PharmaPatents Blog
Authors: Courtenay C. Brinckerhoff

In contrast to its decision in Nuvo Pharmaceuticals, Inc. v. Dr. Reddy’s Laboratories Inc., which seemed to impose a higher standard for satisfying the written description requirement, the Federal Circuit decision in Nalpropion Pharmaceuticals, Inc. v. Actavis Labs. FL, Inc., finds the written description requirement satisfied under what some might call a contrived approach. According to Chief Judge Prost’s dissenting opinion, the majority may have gone astray by treating the claim limitation at issue as secondary to the claimed “invention.” 

The Contrave® Patent At Issue 

The decision arose in the context of ANDA litigation surrounding Nalpropion’s weight loss drug, Contrave® (bupropion hydrochloride; naltrexone hydrochloride). Although several patents were at issue, written description was challenged only for claim 11 of U.S. Patent 8,916,195:

11. A method of treating overweight or obesity having reduced adverse effects comprising orally administering daily about 32 mg of naltrexone and about 360 mg of bupropion, or pharmaceutically acceptable salts thereof, to a person in need thereof, wherein the bupropion or pharmaceutically acceptable salt thereof is administered as a sustained release formulation, wherein the naltrexone or pharmaceutically acceptable salt thereof is administered as a sustained release formulation, and wherein said sustained release formulation of naltrexone has an in vitro naltrexone dissolution profile in a dissolution test of USP Apparatus 2 Paddle Method at 100 rpm in a dissolution medium of water at 37° C of: 

a) between 39% and 70% of naltrexone released in one hour;
b) between 62% and 90% of naltrexone released in two hours; and
c) at least 99% in 8 hours; 

wherein about 16 mg of said sustained release formulation of naltrexone or a pharmaceutically acceptable salt thereof is administered twice daily, and about 180 mg of said sustained release formulation of bupropion or a pharmaceutically acceptable salt thereof is administered twice daily.

Actavis challenged written description support for this claim because the specification does not report dissolution testing results obtained in accordance with USP Apparatus 2 (paddle method), but rather reports results obtained using the basket method (USP Apparatus 1).  

The claim language at issue was added in the last amendment before the application was allowed. The claim previously recited using a “standard” dissolution test, and in the response the claim language was said to be supported by paragraph [0044] of the specification, which discloses the USP method using Apparatus 2 at a spindle rotation speed of 100 rpm and a dissolution medium of water at 37° C as an example of a “standard” dissolution test.  The specification also includes this general disclosure of release rates which refers back to the “standard dissolution test” described earlier:

The amount of the sustained-release carrier composition may be effective to provide an in vitro release rate of the naltrexone of less than about 90%, or less than about 80%, in about 2 hours. The amount of the sustained-release carrier composition may be effective to provide an in vitro release rate of the naltrexone of less than about 98% in about 4 hours. The amount of the sustained-release carrier composition may be effective to provide an in vitro release rate of the naltrexone of less than about 80% or than about 70% in about 1 hour. In vitro release rate is determined by a standard dissolution test as described above.

Example 2 reports dissolution testing using a basket (Tables 5 and 6).  Example 3 reports results of dissolution testing, but does not state which apparatus was used (Table 10).  

The District Court Decision

The district court made two main findings on the written description issue that the Federal Circuit majority followed:

First, district court held that “whether the dissolution data reported in the specification was obtained using the basket method or the paddle method is not relevant to whether the inventors had possession of the invention.” 

Second, the district court held that the two dissolution testing methods were “substantially equivalent.” 

The Federal Circuit Decision

The Federal Circuit Decision was authored by Judge Lourie and joined by Judge Wallach. 

As Judge Prost points out in her dissenting opinion, Judge Lourie started the written description analysis by explaining that the claim limitation at issue was secondary to the “invention”: 

It is important to take note of the peculiarity of claim 11, which begins clearly enough by reciting a method of treating overweight or obesity by carrying out the specific, positive steps of administering a formulation of specific amounts of sustained-release naltrexone and bupropion in twice a day. The claim then records the dissolution data resulting from that formulation.

But that dissolution profile for naltrexone as measured by USP 2 relates only to the measurement of resultant in vitro parameters, not to the operative steps to treat overweight or obesity. 

(It’s really not very peculiar to recite product features in therapeutic method claims ….)

Judge Lourie then credits the district court’s finding that dissolution testing using USP Apparatus 1 and USP Apparatus 2 are “substantially equivalent.” From that, he explains: 

[The district court] found that, irrespective of the method of measurement used, the specification shows that the inventors possessed the invention of treating overweight or obesity with naltrexone and bupropion in particular amounts and adequately described it. We conclude that this finding does not present clear error.

The majority opinion concludes: 

While as a general matter written description may not be satisfied by so-called equivalent disclosure, in this case, buttressed by the district court’s fact-finding, and where the so-called equivalence relates only to resultant dissolution parameters rather than operative claim steps, we affirm the district court’s conclusion. Rigidity should yield to flexible, sensible interpretation.

The Right Decision For The Wrong Reason?

While the Federal Circuit decision on its face may seem contrived, having reviewed the specification and prosecution history I might agree that the court reached the correct result. It is not clear from the Federal Circuit decision that the specification expressly discloses dissolution testing using USP Apparatus 2 and refers to it as a “standard” method. Given that disclosure and the district court’s decision to credit expert testimony that the methodologies are “substantially equivalent,” it does not seem unreasonable to find that dissolution properties obtained using USP Apparatus 1 could support claim language reciting dissolution properties obtained using USP Apparatus 2. In her dissenting opinion, Judge Prost notes that “The record contains no evidence showing that the two methods produce the same results,” but I would think it would have been Actavis’s burden to show that the two methods produce such different results that testing via one would be insufficient to show possession of subject matter defined with respect to the other.

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