Inari Medical, Inc. v. Imperative Care, Inc.

Background

Inari Medical, Inc. and Imperative Care, Inc. sell competing catheter-based devices for treating venous blood clots. Inari asserted two patents in its motion: U.S. Patent Nos. 11,844,921 and 11,974,910. The first concerns a hemostasis valve, which helps seal a catheter and limit blood loss. The second concerns an aspiration system using telescoping catheters and vacuum pressure to remove clot material associated with pulmonary embolism.

Imperative Care’s Symphony system uses catheters, aspiration, and a vacuum generator. Imperative Care received Food and Drug Administration clearance to sell Symphony for treating deep-vein thrombosis in February 2023 and began selling it in August 2023. It received clearance to market Symphony for pulmonary embolism on August 28, 2025, and expected to begin a limited market release in the following months.

Inari requested a preliminary injunction—an order providing temporary relief before trial—that would have barred Imperative Care and specified persons acting for it from making, using, selling, offering to sell, importing, marketing, or distributing Symphony in the United States, except for exempted clinical-study activity. The court treated the requested order as mandatory because it would change the pre-dispute situation by requiring Imperative Care to stop selling and marketing a device it had already been selling for deep-vein thrombosis procedures.

Legal standard

The court applied the four requirements for a preliminary injunction: the plaintiff must show a likelihood of success on the merits, likely irreparable harm without the injunction, a favorable balance of hardships, and that the injunction would serve the public interest. The court did not require the heightened likelihood showing sometimes applied to mandatory injunctions in the patent context, but it considered the injunction’s mandatory nature when evaluating the hardships and potential harm.

Likelihood of success

The court focused on Imperative Care’s challenges to the validity of Inari’s patent claims. A patent is presumed valid, but at the preliminary-injunction stage the accused infringer may present evidence of invalidity. If that evidence raises a substantial question—meaning an invalidity defense that the patent holder has not shown lacks substantial merit—the patent holder has not shown a likelihood of success on validity.

For the ’921 Patent, Imperative Care argued that prior-art reference Schaffer anticipated the asserted claims and that Schaffer combined with Hartley made them obvious. The court considered a Patent Trial and Appeal Board decision instituting inter partes review of a related patent in the same family. The Board had found a reasonable likelihood that Imperative Care would prevail on anticipation and obviousness arguments. The court found that the related patent and the ’921 Patent claims had no relevant differences for this preliminary analysis. It also concluded that Schaffer disclosed the additional elements required by claim 10. The court therefore found substantial questions about the validity of claims 1 and 10 of the ’921 Patent. Either the anticipation or obviousness challenge alone was sufficient to prevent Inari from showing likely success.

For the ’910 Patent, Imperative Care argued that Garrison and Laub together made claim 1 obvious. The court found that Garrison disclosed nearly all of the claim’s limitations, including telescoping catheters, while Laub disclosed the use of the system for pulmonary embolism and catheters sized at least 16 French. The court also found that a skilled person would have had a reason to combine the references because they addressed closely related clot-removal technology. Inari’s evidence about differences between systems for smaller and larger blood vessels did not eliminate that motivation to combine. The court concluded that Imperative Care had raised substantial questions about the validity of all claims asserted in the motion and that Inari had not shown likely success.

Irreparable harm and causal connection

The court separately found that Inari had not shown likely irreparable harm. Inari relied mainly on future lost sales, price erosion, and lost market share. The court found that the sales to date were very small or limited, that monetary losses could be addressed through damages, and that Inari’s assertions about future price erosion were unsupported. Inari also remained the dominant participant in the United States mechanical-thrombectomy market, while Imperative Care had no share in the pulmonary-embolism market and only a very small share in the deep-vein-thrombosis market.

The court also found no sufficient causal nexus, meaning a connection between the alleged infringement and the claimed harm. Inari did not provide direct evidence that the allegedly infringing valve and telescoping-catheter features drove customer demand for Symphony. The court noted that most Symphony procedures used only one catheter and that the specific features were not shown to be significant reasons for purchases. Inari’s copying allegations and evidence about a Freedom of Information Act request were also insufficient.

Balance of hardships and public interest

The court found that the balance of hardships favored Imperative Care. Imperative Care had made substantial investments in Symphony, was at an early stage of entering the market, and would face serious business consequences if sales were blocked. The proposed injunction would have blocked Imperative Care’s only product in the mechanical-thrombectomy market. By contrast, the court found that Inari was unlikely to suffer irreparable harm from continued competition during the litigation.

The court found the public-interest factor neutral. Enforcing valid patent rights and encouraging innovation generally serves the public interest, but that consideration carried less weight because the court found serious questions about the validity of Inari’s asserted claims.

Disposition

The court held that Inari had not shown that any of the preliminary-injunction requirements favored relief, much less all of them. It therefore denied Inari’s motion for a preliminary injunction.