When Can New Uses for Known Drugs Be Patented?

When Can New Uses for Known Drugs Be Patented?

Novartis v West-Ward (Fed. Cir., 2018-1434)

An invention is only eligible for patent protection in the US if, at the filing date, it would not have been obvious to a person skilled in the art (often called “POSITA”). A recent decision from the United States Court of Appeals for the Federal Circuit (“CAFC”), clarified the test for obviousness where an invention claims a new use of a known drug. The CAFC upheld the decision by the District Court dismissing an attempt by West-Ward Pharmaceutical International Limited (“West-Ward”) to invalidate a patent owned by Novartis Pharmaceuticals Corporation (“Novartis”) but found that the District Court had erred in its application of the law.

The ‘131 Patent

US Patent No. 8,410,131 (the “’131 Patent”) covers a method of using the compound everolimus to treat a type of kidney cancer known as advanced renal cell carcinoma (“RCC”). [pg. 3] Everolimus (marketed by Novartis as “Afinitor”) works by blocking an enzyme on the tumour cells leading to decreased levels of a cell growth factor called HIF-1. [pg. 5]

At the time the ‘131 Patent was filed in 2001, it was known that binding the enzyme could inhibit cell growth and that a family of compounds including everolimus caused tumour regression. [pg. 7-8] Another member of that family, temsirolimus, had been shown to produce responses in cancer patients including three RCC patients. [pg. 8] A previous patent disclosed a method for making everolimus into oral tablets, but it was not known at the time that everolimus could be used to treat RCC or any other tumour. [pg. 9]

The Obviousness Test

There is a two-step test to determine whether an invention is obvious. In order to invalidate the ‘131 Patent, West-Ward needed to first prove that a person skilled in pharmacology or a relevant field would have been motivated to test everolimus in the treatment of RCC. Secondly, West-Ward needed to prove that a skilled person had a reasonable expectation of success of treating RCC with everolimus. [pg. 13] The CAFC ruled against the District Court on the first prong of the test, but ultimately upheld the conclusion of the District Court on the second step.

Motivation to Combine

In the first step, the District Court was correct in finding that a skilled person would have been motivated by the combination of prior patents and research articles to pursue everolimus as a possible treatment option for RCC. However, the Court erred in adding that a skilled person would not have selected everolimus over other potential treatment options. According to the CAFC, this requirement to identify everolimus as the most desirable treatment is a “heightened standard.” [pg. 14] The question is not whether a skilled person would have selected everolimus over other candidate drugs, but rather   whether or not a skilled person would have been motivated to test everolimus among other treatments. [pg. 14]

Reasonable Chance of Success

Nonetheless, West-Ward’s case failed on the second stage of the test. The CAFC held that the District Court was correct to find that a person of ordinary skill’s understanding of RCC and everolimus in 2001 provided no reasonable expectation that the drug would succeed. [pg. 16-17] At the time the ‘131 Patent was filed, temsirolimus had only been tested for safety, not its ability to suppress tumours. Moreover, key properties differentiated everolimus from temsirolimus such that a skilled person would not have predicted that the two compounds would have similar anti-tumour efficacy. [pg. 17] Everolimus was known to inhibit mTOR, but it was not known that this would affect HIF-1 levels in kidney tumours. [pg. 18] Therefore, the CAFC concluded that Novartis’s invention would not have been obvious to a skilled person in 2001 and is worthy of patent protection.

Commentary

This decision from the CAFC reiterates that the first step in the obviousness analysis is a relatively low bar. When the invention is a new use for a known drug, a party challenging the patent only needs to show that it would have been obvious to include this particular drug among numerous other drugs being screened in the treatment of a disease. Due to the uncertain nature of clinical testing, a challenger may face some difficulty in the second step where a court asks whether the drug presented a reasonable chance of success. If you have further questions about the patent eligibility of known drugs, contact a PCK IP professional