From The Field

October 10, 2019

35 U.S.C. Section 112 requires that patent claims have adequate written support. As a general matter, the requirement of adequate written description may not be satisfied by a so-called “equivalent disclosure.” A recent Federal Circuit opinion demonstrates that there are exceptions to this general rule.

In Nalpropion Pharms., Inc. v. Actavis Labs. FL, Inc., 2019 U.S. App. LEXIS 24281 (Fed. Cir. Aug. 15, 2019), Actavis filed an ANDA seeking to enter the market with a generic version of Nalpropion’s Contrave®, a weight management drug. In the district court, Actavis tried to invalidate claim 11 of U.S. Patent No. 8,916,195 (“the ’195 Patent”) – one of the patents covering the drug – for lack of adequate written description. Claim 11 recites a method of treating obesity by orally administering about 16 mg of naltrexone and about 180 mg of bupropion in certain formulations. The claim also requires that the claimed naltrexone formulation have a specific dissolution profile. The relevant claim language recites:

in a dissolution test of USP Apparatus 2 Paddle Method at 100 rpm in a dissolution medium of water at 37oC of:

  • Between 39% and 70% of naltrexone released in one hour;
  • Between 62% and 90% of naltrexone released in two hours; and
  • At least 99% in 8 hours . . . .

Two tables in the patent specification include naltrexone dissolution data that encompasses the ranges claimed in elements (a)-(c) quoted above. But the specification is silent as to whether the data in the tables was obtained using the recited USP 2 method.

Actavis provided evidence showing that the data was obtained using USP 1 and argued, on that ground, that the tables did not provide adequate written description support to claim 11, which specifically recited USP 2. Relying on Nalpropion’s expert’s testimony that a person of skill would understand that the inventors possessed the claimed invention regardless of whether USP 2 or a substantially equivalent method (e.g., USP 1) was used to measure the dissolution profile, the district court rejected Actavis’ argument.

The Federal Circuit affirmed the district court’s decision on appeal. The court found that the district court’s factual findings, namely that USP 1 and USP 2 were substantially equivalent and that the specification showed that the inventors possessed the invention claimed in claim 11, presented no clear error.

Significantly, the Federal Circuit pointed out that its holding represented an exception to the general rule that written description may not be satisfied by so-called equivalent disclosure. The court stated that a consideration in its decision was that the issue in dispute, i.e., the measurement of the dissolution profile of the naltrexone formulation, relates not to the operative steps to treat overweight or obesity (i.e., the invention) but to an ancillary issue – the measurement of the dissolution profile of the active ingredient, naltrexone. The court stated: “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.”

Author: Hui Liu