Background
Mallinckrodt Hospital Products marketed INOmax® — inhaled nitric oxide (iNO) for treating hypoxic respiratory failure in newborns. Mallinckrodt held patents claiming methods of supplying iNO therapy while monitoring patients for adverse cardiovascular effects — specifically, the worsening of pulmonary edema in patients with pre-existing left ventricular dysfunction (a condition in which the heart’s left chamber pumps poorly). The claims required administering iNO, monitoring for pulmonary edema signs in patients with left heart dysfunction, and adjusting (reducing or stopping) iNO therapy if edema worsened.
Praxair challenged the patents as directed to the natural phenomenon that iNO can cause or worsen pulmonary edema in patients with left heart dysfunction — a recognized clinical risk. The claims, Praxair argued, merely told doctors to be aware of and respond to this natural phenomenon using conventional clinical monitoring and dose adjustment techniques.
The Court’s Holding
The Federal Circuit held the claims patent-ineligible under § 101. Applying Mayo, the court found the claims directed to the natural phenomenon that iNO therapy can worsen pulmonary edema in patients with left ventricular dysfunction — a natural bodily response to the drug. The additional steps of monitoring for edema and adjusting iNO therapy were conventional clinical practices performed using standard medical monitoring equipment and dose adjustment protocols. These conventional clinical steps did not transform the natural phenomenon into a patent-eligible method.
The court distinguished Vanda Pharmaceuticals v. West-Ward (which had not yet been decided at this point, but was later decided in 2018): unlike a specific treatment protocol with particular dosing decisions tied to a genetic test result, Mallinckrodt’s claims essentially required doctors to be aware of and respond to a known drug risk — a clinical practice rather than a specific inventive treatment protocol.
Key Takeaways
- Method-of-treatment claims that essentially instruct physicians to monitor for and respond to a known adverse drug effect using conventional clinical monitoring techniques are directed to a natural phenomenon — the adverse effect itself — and lack an inventive concept sufficient for patent eligibility under Mayo.
- Drug therapy monitoring and dose adjustment claims must do more than direct physicians to conventional clinical vigilance for known drug risks — claims that specify novel monitoring approaches or unconventional treatment responses are better positioned for § 101 survival.
- The gap between Praxair (2016, ineligible drug monitoring claim) and Vanda (2018, eligible treatment protocol claim) turned on the specificity and concreteness of the therapeutic action required by the claim — broad monitoring and adjusting instructions fail where specific dose decisions based on specific diagnostic results succeed.
- Pharmaceutical and biologic drug patent portfolios should be audited for § 101 vulnerability with respect to claims that primarily claim monitoring for or responding to known adverse effects using conventional clinical methods — these claims are particularly vulnerable under the Mayo framework.
Why It Matters
Praxair Distribution v. Mallinckrodt illustrated the limitations of § 101 patent protection for drug therapy monitoring claims — an important category of pharmaceutical patents that seek to protect the use of drugs by specifying safety monitoring requirements. The decision showed that when a drug’s adverse effects are natural phenomena and the monitoring and dose adjustment steps are conventional medical practice, the resulting patent claim is directed to telling physicians to acknowledge and respond to a natural phenomenon, not to a patent-eligible inventive method.
The decision was commercially significant for the inhaled nitric oxide market: Mallinckrodt’s monitoring claims were among the last patent protections for INOmax after the composition patents expired, and their invalidity under § 101 cleared the way for generic iNO competition. The case highlights how § 101 has become a critical validity battleground for pharmaceutical companies whose late-stage patent protection strategies rely on use or monitoring claims tied to known drug properties and effects.