For the second time in as many weeks, the Federal Circuit has reversed a district court’s finding of patent ineligibility under Section 101 in the life science space, this time concluding that claims directed to methods of treating pain in renally impaired patients are patent-eligible. In Endo Pharmaceuticals Inc. v. Teva Pharmaceuticals USA, Inc., the Federal Circuit again attempted to narrow the Supreme Court’s holding in Mayo and strengthen its own precedent that method of treatment claims are directed to patent-eligible subject matter., 
Endo Pharmaceuticals Inc. (Endo) owns U.S. Patent No. 8,808,737 (the ’737 patent), which claims methods of treating pain in a renally impaired patient. The ’737 patent purports to disclose the discovery that the bioavailability of controlled-released oxymorphone can be increased in patients with renal impairment, especially in patients with moderately to severely impaired kidney function. This increased bioavailability is said to result in a higher level of oxymorphone in the blood of those patients than in the blood of healthy patients receiving the same dose, which can lead to harmful effects if the dose is not decreased. Armed with these findings, the inventor is said to have developed a new method of treating pain relief in patients with renal impairment.
Claim 1 of the ’737 patent recites:
A method of treating pain in a renally impaired patient, comprising the steps of:
a. providing a solid oral controlled release dosage form, comprising:
i. about 5 mg to about 80 mg of oxymorphone or a pharmaceutically acceptable salt thereof as the sole active ingredient; and
ii. a controlled release matrix;
b. measuring a creatinine clearance rate of the patient and determining it to be (a) less than about 30 mL/min, (b) about 30 mL/min to about 50 mL/min, (c) about 51 mL/min to about 80 mL/min, or (d) above about 80 mL/min; and
c. orally administering to said patient, in dependence on which creatinine clearance rate is found, a lower dosage of the dosage form to provide pain relief;
wherein after said administration to said patient, the average AUC of oxymorphone over a 12-hour period is less than about 21 ng·hr/mL.
Endo sued the defendants for allegedly infringing claims 1-6 of the ’737 patent. Actavis moved to dismiss, arguing that the claims are ineligible under Section 101. The magistrate judge recommended granting Actavis’ motion, concluding that under step 1 of the Alice/Mayo test, the claims are directed to a natural law – the increased bioavailability of oxymorphone in patients with renal impairment. For step 2, the magistrate judge analyzed the “providing,” “measuring” and “administering” steps of the claims, finding that:
- The “providing” step “merely identifies the specific drug for administration,” similar to the administering step in Mayo.
- The “measuring/determining” step “just directs one to use a well-known method to measure creatinine levels to obtain the necessary information to apply a law of nature” like Mayo.
- The “administering” step, like Mayo, “merely instructs physicians to dispense oxymorphone for the treatment of pain in a well-know[n] manner.”
The district court adopted the magistrate judge’s recommendation, finding the claims ineligible under Section 101. Endo stipulated that the claims were ineligible in its case against Teva, which was before the same judge, and appealed the ruling.
The Federal Circuit disagreed, concluding that the claims are not directed to patent-ineligible subject matter. In reaching this conclusion, the court first focused on the claims and specification, which were found to repeatedly describe the invention as a method of treating pain in patients with renal impairment. The court also noted that claim 1 requires the specific steps of (a) providing a pharmaceutical, (b) testing the patient for a disease state and (c) administering the pharmaceutical. The court concluded that the claims were “legally indistinguishable from the representative claim in Vanda.” According to the court, the Vanda claims recite the steps of carrying out a dosage regimen based on the results of genetic testing, and Endo’s claims recite the steps of carrying out a dosage regimen based on the results of kidney function testing.Additionally, both claim sets require specific treatment steps. According to the court, Endo’s claims “are eligible because they are ‘directed to a specific method of treatment for specific patients using a specific compound at specific doses to achieve a specific outcome.’” Interestingly, the court was not convinced by Actavis’ argument that the Endo claims fail to recite any particular way to obtain or assay a biological sample.
The court then spent some time comparing and contrasting the Endo and Vanda claims to those analyzed in other Supreme Court or Federal Circuit decisions, stating that:
- The representative Mayo claim “as a whole was not directed to the application of a drug to treat a particular disease.”
- The administering step in the Mayo claim “is the first step in the method that simply describes giving the drug to a patient with a certain disorder,” whereas the administering step in Endo’s claims “describes giving a specific dose of the drug based on the results of kidney function testing.”
- Unlike in Mayo, where the claim could “tie up the doctor’s subsequent treatment decision,” pre-emption is not a valid concern with Endo’s claims, which recite the steps of performing the dosage regimen based on the kidney function testing results.
- Like the claims found patent-eligible in CellzDirect, “the result of the claims is not simply an observation or detection” but rather is directed to “a new and useful method of treating pain in patients with impaired renal function.”, 
- Unlike the claims found patent-ineligible in Ariosa and Athena, Endo’s claims are directed to a method of treatment, not a method of detection, and “are directed to a new treatment for an ailment, albeit using a natural law or phenomenon.”, 
With this decision, the Federal Circuit continues to push for the subject matter eligibility of method of treatment claims, focusing again on the administering step and the recited dosing regimen. The Supreme Court, however, has expressed interest in the Vanda decision, recently requesting the views of the U.S. solicitor general on this exact issue. Time will tell the fate of method of treatment claims.
 Endo Pharmaceuticals Inc. v. Teva Pharmaceuticals USA, Inc., No. 2017-1240, 2019 WL 1387988 (Fed. Cir. Mar. 28, 2019).
 Mayo Collaborative Servs. v. Prometheus Labs., Inc., 566 U.S. 66 (2012).
 ’737 patent at 10:15-19.
 Id. at 10:19-24.
 Endo Pharmaceuticals Inc., 2019 WL 1387988 at *2.
 Id. at *3.
 Id. at *4.
 Vanda Pharmaceuticals Inc. v. West-Ward Pharmaceuticals Int’l Ltd, 887 F.3d 1117 (Fed. Cir. 2018).
 Endo Pharmaceuticals Inc., 2019 WL 1387988 at *5.
 Id. at *6 (citing Vanda, 887 F.3d at 1136).
 Id. at *6.
 Id. at *6.
 Rapid Litig. Mgmt. Ltd. v. CellzDirect, Inc., 827 F.3d 1042, 1050 (Fed. Cir. 2016).
 Endo Pharmaceuticals Inc., 2019 WL 1387988 at *7.
 Athena Diagnostics, Inc. v. Mayo Collaborative Servs., LLC, 915 F.3d 743 (Fed. Cir. 2019).
 Endo Pharmaceuticals Inc., 2019 WL 1387988 at *7.