The US Court of Appeals for the Federal Circuit affirmed a district court decision rejecting claims of a patent application directed to a dosing regimen for a cancer treatment, finding the claims to be obvious where the motivation to use the claimed dosing was not the same as the inventor’s motivation. ImmunoGen, Inc. v. Coke Morgan Stewart, Case No. 23-1763 (Fed. Cir. Mar. 6, 2025) (Lourie, Dyk, Prost, JJ)
The claims at issue involved a dosing regimen for administering IMGN853, an already-patented antibody drug conjugate used for treating certain cancers, at a claimed dose of six milligrams (mg) per kilogram (kg) of adjusted ideal body weight (AIBW) of the patient.
ImmunoGen argued that it was undisputed that, at the time of the invention, a person of ordinary skill in the art would not have known that IMGN853 caused ocular toxicity in humans and that without a motivation to address the problem of ocular toxicity, the claimed dosing limitation could not have been obvious. Therefore, according to ImmunoGen, the district court erred in its motivation-to-combine analysis. The Federal Circuit disagreed, stating, “that the specific problem the inventors . . . purported to solve via the claimed dosing regimen was unknown does not necessarily mean that the dosing regimen itself was not obvious.” The Court also noted that because ocular toxicity was a well-known adverse event in the administration of drugs containing a payload included in IMGN853, “a person of ordinary skill in the art, despite not knowing of IMGN853’s ocular toxicity, would have nonetheless been motivated to monitor for those side effects when administering the drug to a human.”
ImmunoGen also argued that the district court erred in finding that a person of ordinary skill in the art would have been motivated to use AIBW dosing to eliminate ocular toxicity. The Federal Circuit again disagreed, reasoning that although AIBW dosing has not been used for drugs such as IMGN853, it would still have been within the range of knowledge of a person of ordinary skill in the art when addressing dosing-induced ocular toxicity. The Court explained that AIBW was well known, had been used for drugs both smaller and larger than IMGN853, and had proven effective in reducing ocular toxicity.
The Federal Circuit concluded that the district court did not clearly err in determining that a person of ordinary skill in the art would have been motivated to select the claimed dose of six mg/kg AIBW with a reasonable expectation of success. The claimed dose had already been described in the literature for patients at their ideal body weight, regardless of whether a doctor was aware of AIBW dosing specifically. The Court also noted that the district court was not required to find that a person of ordinary skill in the art would have had a reasonable expectation of eliminating ocular toxicity using the claimed dose, as “the obviousness inquiry is generally agnostic to the particular motivation of the inventor” and the claims made no reference to ocular toxicity.
Practice Note: The motivation to combine analysis is not limited by the problem or need recognized by the inventors. Instead, any problem known at the time of the invention can provide a reason for combining elements as claimed.