Last updated: August 2, 2026
Astellas US LLC v. Hospira, Inc., No. 1:18-cv-01675, was a Hatch-Waxman patent case in the U.S. District Court for the District of Delaware involving Hospira’s proposed generic version of Lexiscan, Astellas’ regadenoson injection product. Astellas asserted U.S. Patent No. 8,106,183, which covered methods of inducing pharmacologic stress using regadenoson during myocardial perfusion imaging. The dispute centered on whether Hospira’s ANDA product infringed the patent and whether the asserted claims were invalid for obviousness.
The case had direct commercial significance because Lexiscan was a high-value branded injectable with limited competing products. The principal patent was scheduled to expire in 2025, creating a potential generic-entry window before or near the end of the decade.
What drug was at issue in Astellas v. Hospira?
The case involved Lexiscan, the brand name for regadenoson injection.
Regadenoson is a selective adenosine A2A receptor agonist used as a pharmacologic stress agent in patients undergoing radionuclide myocardial perfusion imaging when exercise stress testing is inappropriate or inadequate. Lexiscan is administered intravenously and produces coronary vasodilation without requiring the patient to exercise.
| Item |
Details |
| Brand |
Lexiscan |
| Active ingredient |
Regadenoson |
| Dosage form |
Intravenous injection |
| Therapeutic use |
Pharmacologic cardiac stress testing |
| Originator |
Astellas US LLC and related Astellas entities |
| Regulatory pathway |
ANDA litigation under Hatch-Waxman |
| Defendant |
Hospira, Inc. |
| Court |
U.S. District Court for the District of Delaware |
| Case number |
1:18-cv-01675 |
| Presiding judge |
Judge Richard G. Andrews |
Lexiscan is a small-molecule drug. Biosimilar law therefore does not apply. The relevant competitive threat was an ANDA-based generic, not a biosimilar application under the Public Health Service Act.
What patents protected Lexiscan in the Hospira litigation?
The central patent was U.S. Patent No. 8,106,183.
U.S. Patent No. 8,106,183
The ’183 patent covered methods involving the administration of regadenoson to induce coronary hyperemia for myocardial perfusion imaging. The patent’s commercial importance came from its method-of-use claims rather than from a basic composition claim covering regadenoson itself.
The patent had the following general profile:
| Patent |
Subject matter |
Litigation role |
Expected expiration |
| U.S. 8,106,183 |
Regadenoson method of use for pharmacologic stress imaging |
Principal asserted patent |
2025, subject to the applicable patent-term adjustment and Orange Book listing |
The litigation record focused on whether the prior art made it obvious to use regadenoson in the claimed cardiac-imaging setting. Hospira argued that the relevant pharmacology, adenosine-receptor science and stress-imaging protocols provided a sufficient motivation to arrive at the claimed method.
Astellas defended the patent by emphasizing the claimed clinical advantages of regadenoson, including its selectivity for the A2A receptor and its suitability for use in pharmacologic myocardial perfusion imaging.
When did Astellas file the lawsuit against Hospira?
Astellas filed the action in 2018 after receiving notice of Hospira’s Paragraph IV certification.
The complaint triggered the Hatch-Waxman litigation framework. Under 21 U.S.C. § 355(j)(5)(B)(iii), filing a patent-infringement action within the statutory period can impose an automatic 30-month stay on FDA approval of the challenged ANDA, subject to court action and statutory exceptions.
The case was docketed as No. 1:18-cv-01675 in the District of Delaware. The pleadings alleged that Hospira’s proposed regadenoson product would infringe the ’183 patent under 35 U.S.C. § 271(e)(2), which treats the submission of an ANDA containing specified patent certifications as an artificial act of infringement.
What were the main legal issues?
The dispute had two principal legal issues:
- Whether Hospira’s proposed generic product and labeling would practice the asserted method of use.
- Whether the asserted claims were invalid as obvious under 35 U.S.C. § 103.
Infringement
Astellas’ infringement theory depended heavily on the proposed ANDA labeling. In Hatch-Waxman cases, a generic applicant can face liability where its proposed label directs or encourages use of the product in a patented manner, even if the applicant does not itself administer the drug.
The relevant question was whether Hospira’s labeling would encourage use of regadenoson for myocardial perfusion imaging in a manner falling within the patent claims. The analysis therefore covered:
- The scope of the claimed stress-imaging method.
- The dose and administration protocol.
- The patient population.
- The use of regadenoson to induce coronary hyperemia.
- The content of Hospira’s proposed labeling.
Because generic injectable products generally follow the reference product’s labeling closely, method-of-use patents can present a material infringement risk even when the active ingredient is old or no longer protected by composition claims.
Obviousness
Hospira’s invalidity defense challenged the patent’s nonobviousness. The prior-art analysis considered whether a skilled artisan would have been motivated to select regadenoson for cardiac stress imaging and whether the claimed result would have been reasonably predictable.
Astellas relied on the clinical and pharmacological advantages associated with regadenoson. Its position was that the claimed use was not an automatic or routine substitution based on the prior art and that the relevant technical literature did not establish a reasonable expectation of success.
The case illustrates the litigation value of method-of-use patents for mature injectable drugs. Even where the active ingredient and general pharmacology are known, a patent may retain commercial leverage if its claims cover the labeled indication and the generic applicant’s proposed label is substantially aligned with that indication.
What was the court’s decision?
The District of Delaware ruled in favor of Astellas on the principal patent dispute, rejecting Hospira’s challenge to the ’183 patent and finding the asserted claims enforceable against the proposed generic product. The judgment preserved Astellas’ ability to block FDA approval of Hospira’s ANDA during the remaining patent term.
The case proceeded through appellate review. The Federal Circuit’s treatment of the dispute confirmed that the validity and infringement analysis turned on the specific claim language, the scope of the ANDA labeling and the evidence concerning the predictability of the claimed regadenoson use.
The litigation did not produce a broad ruling invalidating the Lexiscan patent estate. The commercial effect was a continued barrier to Hospira’s launch until resolution of the patent term, an authorized launch arrangement or another legally effective pathway.
What was the Orange Book status of Lexiscan?
Lexiscan was listed in the FDA’s Orange Book with patent information covering the product and its approved use. The ’183 patent was the principal patent associated with the Hospira litigation.
Orange Book listings matter because an ANDA applicant must make a patent certification for each listed patent. A Paragraph IV certification states that the patent is invalid, unenforceable or will not be infringed by the proposed generic product. The certification gives the patent holder a basis to file an infringement action under Section 271(e)(2).
The case therefore represented a standard Orange Book dispute:
- Astellas listed a patent for Lexiscan.
- Hospira submitted an ANDA with a Paragraph IV certification.
- Astellas sued within the statutory period.
- The action created the statutory approval stay.
- The parties litigated validity and infringement in advance of generic launch.
The precise regulatory effect depended on the ANDA’s approval status, the timing of notice and the patent’s listed expiration date. A court judgment does not itself authorize commercial launch if other listed patents, pediatric exclusivity or regulatory requirements remain outstanding.
When does Lexiscan lose patent exclusivity?
The principal patent barrier associated with this case was scheduled to expire in 2025, subject to the final Orange Book expiration date, any patent-term adjustment and any applicable pediatric exclusivity.
Lexiscan’s regulatory exclusivity was separate from patent exclusivity. The product’s new-drug exclusivity period expired years before the Hospira case. By 2018, the commercial barrier was therefore patent-based rather than NCE-based.
| Exclusivity category |
Lexiscan status |
| New chemical entity exclusivity |
Expired before the 2018 case |
| Patent protection |
Continued through the listed term of the asserted patent |
| Biosimilar exclusivity |
Not applicable |
| Generic approval barrier |
Paragraph IV litigation and statutory stay |
| Primary litigation patent |
U.S. 8,106,183 |
| Expected end of principal patent barrier |
2025, subject to the official Orange Book term |
What generic entry risks existed for Astellas?
The generic-entry risk was meaningful because Lexiscan is an injectable product with a relatively concentrated competitive field. A successful Hospira launch could have affected Astellas through:
- Price erosion from generic regadenoson.
- Conversion of hospitals and imaging centers to lower-cost suppliers.
- Contracting pressure from group purchasing organizations.
- Loss of formulary preference.
- Reduced unit volume after generic substitution.
- Erosion of the product’s remaining lifecycle value.
The risk was moderated by several factors. Regadenoson is administered in controlled clinical settings, procurement is often contract-based and injectable suppliers must satisfy manufacturing, sterility and supply-continuity requirements. Those factors can slow substitution compared with conventional retail-tablet markets.
The absence of biosimilar exposure was favorable to Astellas. Generic competition could still be rapid after patent expiry, but the approval pathway was simpler than the interchangeability and biologic-manufacturing issues applicable to biosimilars.
How strong was the Lexiscan patent estate?
The Lexiscan estate was commercially useful but narrow.
Strengths
- The asserted patent covered the approved clinical use.
- Hospira’s ANDA label created a direct infringement pathway.
- The patent remained in force during a period when the product had established commercial demand.
- The product was an injectable, increasing manufacturing and regulatory barriers for generic entrants.
- The litigation preserved the possibility of delaying approval through the Hatch-Waxman stay.
Weaknesses
- The patent was a method-of-use patent rather than a basic composition patent.
- The active ingredient’s pharmacology was known before the patent’s asserted clinical use.
- Obviousness depended on the strength of the prior-art combination.
- Label-based method claims can be vulnerable to carve-out strategies if the FDA-approved uses can be separated.
- The patent term was finite and near expiration when the litigation matured.
Overall, the ’183 patent had strong litigation relevance because it mapped to the Lexiscan label, but its ultimate durability depended on the obviousness record and the ability of a generic applicant to avoid the claimed use through labeling or product-positioning strategies.
Did the case involve a settlement agreement?
The public case record should be distinguished between judicial rulings and any confidential or private settlement terms. The docket reflects the litigation and judicial resolution of the patent dispute, but commercial terms such as launch dates, licenses, royalties and supply arrangements are not necessarily disclosed in full.
For competitive analysis, the critical question is whether Hospira obtained:
- A license before patent expiry.
- A defined early-entry date.
- A royalty-bearing launch right.
- A supply or manufacturing arrangement.
- A dismissal conditioned on a regulatory event.
Unless those terms are filed publicly, they should not be treated as established facts. The judicial outcome itself is the reliable basis for assessing the patent barrier.
Which companies challenged Lexiscan exclusivity?
Hospira was a principal ANDA challenger in the identified case. Other generic applicants may have pursued regadenoson approval or related patent challenges, but each applicant’s Paragraph IV position, proposed labeling and launch date must be assessed separately.
A competitor’s approval does not automatically eliminate Astellas’ patent risk because:
- The approved label may differ from the challenged label.
- The product may be subject to a separate patent certification.
- The applicant may have settled on a later launch date.
- Manufacturing approval may lag behind ANDA approval.
- A separate supplier may face distinct injunction or contract issues.
What patent litigation affects Lexiscan generic launch timing?
The principal timing variables were:
| Timing variable |
Effect |
| Paragraph IV notice |
Started the patent-holder response period |
| Astellas’ timely complaint |
Triggered the Hatch-Waxman approval stay |
| District court judgment |
Determined whether the asserted patent blocked Hospira |
| Federal Circuit review |
Could affirm, reverse or modify the patent judgment |
| Patent expiration |
Removed the principal patent-based approval barrier |
| FDA approval |
Required even after patent resolution |
| Manufacturing readiness |
Affected the practical launch date |
| Settlement terms |
Could permit an earlier licensed entry |
The patent expiration date was the most important long-term endpoint. A generic applicant could obtain FDA approval before expiration but remain unable to market the product without an authorized launch right or a favorable final judgment.
Key Takeaways
- Astellas US LLC v. Hospira, No. 1:18-cv-01675, involved Lexiscan, or regadenoson injection.
- The principal asserted patent was U.S. Patent No. 8,106,183.
- The case was a Hatch-Waxman Paragraph IV action arising from Hospira’s ANDA.
- Astellas prevailed on the principal patent dispute, preserving the patent barrier against Hospira’s proposed generic.
- The relevant patent protection extended into 2025, subject to the official Orange Book term.
- Lexiscan had no biosimilar risk because regadenoson is a small-molecule drug.
- The estate’s strongest feature was the direct alignment between the patent claims and Lexiscan’s approved use.
- The estate’s main weakness was reliance on a method-of-use patent rather than a composition patent.
- Generic launch timing depended on the judgment, appellate review, FDA approval, patent expiration and any confidential commercial resolution.
FAQs About Astellas v. Hospira and Lexiscan
What is the case number for the Lexiscan patent lawsuit?
The case is Astellas US LLC v. Hospira, Inc., No. 1:18-cv-01675, in the U.S. District Court for the District of Delaware.
What is U.S. Patent No. 8,106,183?
The ’183 patent covers methods involving regadenoson administration to induce pharmacologic coronary hyperemia for myocardial perfusion imaging.
Was Hospira’s product a biosimilar to Lexiscan?
No. Hospira’s product was a proposed generic version of regadenoson injection submitted through the ANDA pathway.
Can a generic launch before the Lexiscan patent expires?
Yes, but generally only through a court ruling that removes the infringement barrier, a license or settlement allowing early entry, or another legally effective arrangement.
Why was the Lexiscan method-of-use patent commercially important?
The patent covered the approved clinical use of regadenoson. That allowed Astellas to rely on Hospira’s proposed ANDA labeling as the basis for an infringement claim.
References
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Astellas US LLC v. Hospira, Inc., No. 1:18-cv-01675, U.S. District Court for the District of Delaware, docket filings and judgments.
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U.S. Patent No. 8,106,183. United States Patent and Trademark Office.
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U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations: Lexiscan and regadenoson patent listings. FDA Orange Book.
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U.S. Food and Drug Administration. (n.d.). Abbreviated new drug application regulations and patent certifications. FDA.
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21 U.S.C. § 355(j).
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35 U.S.C. § 271(e)(2).
