Immunogen, Inc. v. Hirshfeld
21-1939
| Fed. Cir. | Mar 25, 2022Background
- ImmunoGen filed U.S. Application No. 14/509,809 claiming a method of treating FOLR1‑expressing ovarian/peritoneal cancer by administering mirvetuximab at 6 mg/kg of adjusted ideal body weight (AIBW).
- The specification defines IBW and AIBW, includes example formulas (IBW(male)=0.9H–88; IBW(female)=0.9H–92; AIBW=IBW + 0.4(Actual weight – IBW)), labels those formulas “for example,” and incorporates Green (2004) discussing drug‑specific correction factors.
- Mirvetuximab produced ocular toxicity at 7 mg/kg TBW in Phase 1; ImmunoGen adopted 6 mg/kg AIBW to retain efficacy while reducing ocular risk. AIBW dosing had not previously been used for this drug class.
- The PTO Board affirmed examiner rejections for obviousness and obviousness‑type double patenting; ImmunoGen sued under 35 U.S.C. § 145 in the Eastern District of Virginia.
- The district court granted summary judgment, holding the claims fatally indefinite and obvious as a matter of law. The Federal Circuit vacated and remanded, finding the district court improperly resolved multiple material factual disputes against ImmunoGen.
Issues
| Issue | Plaintiff's Argument (ImmunoGen) | Defendant's Argument (USPTO/Board) | Held |
|---|---|---|---|
| Indefiniteness of “AIBW” | AIBW is defined by the specification and Example 4; a skilled artisan would understand which formula to use (drug‑specific correction factor) | “For example” language and incorporation of Green create multiple possible IBW/AIBW formulas, leaving scope uncertain | Vacated summary judgment; disputed factual evidence (examples, prosecution history, expert testimony) precludes resolving indefiniteness on summary judgment; remanded |
| Obviousness of claimed dosing regimen | Claims not shown obvious: immunoconjugates are pharmacologically unpredictable; secondary considerations and lack of clear motivation/expectation undermine obviousness | Prior art taught relevant elements; a skilled artisan would be motivated to use AIBW to mitigate ocular toxicity with reasonable expectation of success | Vacated summary judgment; district court improperly resolved factual disputes (motivation, expectation, secondary considerations); remanded |
| Weight/admissibility of expert evidence | Experts show drug‑specific correction factors and that Example 4 and prosecution history inform claim scope | District court characterized expert disagreement as manufactured and declined to credit it | Vacated: court must view evidence in light most favorable to non‑movant; experts create genuine issues of material fact |
Key Cases Cited
- Nautilus, Inc. v. Biosig Instruments, Inc., 572 U.S. 898 (2014) (patent claims must inform skilled artisans of scope with reasonable certainty)
- Anderson v. Liberty Lobby, Inc., 477 U.S. 242 (1986) (summary judgment standard; view evidence in light most favorable to non‑moving party)
- Teva Pharmaceuticals USA, Inc. v. Sandoz, Inc., 789 F.3d 1335 (Fed. Cir. 2015) (factual findings may be required in patent claim‑construction or validity inquiries)
- Acorda Therapeutics, Inc. v. Roxane Laboratories, Inc., 903 F.3d 1310 (Fed. Cir. 2018) (obviousness may turn on factual findings like motivation to combine and reasonable expectation of success)
- Interval Licensing LLC v. AOL, Inc., 766 F.3d 1364 (Fed. Cir. 2014) (examples in the specification can supply definiteness)
- Enzo Biochem, Inc. v. Applera Corp., 599 F.3d 1325 (Fed. Cir. 2010) (a claim phrase defined through examples can satisfy definiteness requirement)