Litigation Details for AstraZeneca LP v. InvaGen Pharmaceuticals Inc. (D. Del. 2015)

AstraZeneca LP v. InvaGen Pharmaceuticals Inc. (D. Del. 2015)

Docket		Date Filed	2015-10-30
Court	District Court, D. Delaware	Date Terminated	2018-03-09
Cause	35:271 Patent Infringement	Assigned To	Richard Gibson Andrews
Jury Demand	None	Referred To
Parties	INVAGEN PHARMACEUTICALS INC.
Patents	6,251,910; 6,525,060; 7,250,419; 7,265,124; 8,425,934
Attorneys	Pei-Ru Wey
Firms	Kratz & Barry LLP
Link to Docket	External link to docket

Details for AstraZeneca LP v. InvaGen Pharmaceuticals Inc. (D. Del. 2015)

Date Filed	Document No.	Description	Snippet	Link To Document
2015-10-30				External link to document
2015-10-30	1		AstraZeneca’s U.S. Patent Nos. 6,251,910 (“the ’910 patent”), 6,525,060 (“the ’060 patent”), ME1 21399823v…7,250,419 (“the ’419 patent”), 7,265,124 (“the ’124 patent”), and 8,425,934 (“the ’934 patent”) that are listed… This is an action for patent infringement arising under the patent laws of the United States, … PATENTS-IN-SUIT 20. On June 26, 2001, the U.S. Patent and Trademark Office…copy of the ’910 patent is attached hereto as Exhibit A. The claims of the ’910 patent are valid and enforceable	External link to document
2015-10-30	28		the Commissioner of Patents and Trademarks for Patent/Trademark Number(s) 6,251,910; 6,525,060; 7,250,419…2015 9 March 2018 1:15-cv-01001 830 Patent None District Court, D. Delaware	External link to document
2015-10-30	4		the Commissioner of Patents and Trademarks for Patent/Trademark Number(s) 6,251,910; 6,525,060; 7,250,419… 30 October 2015 1:15-cv-01001 830 Patent None District Court, D. Delaware	External link to document

AstraZeneca LP v. InvaGen Pharmaceuticals Inc. Litigation Analysis (1:15-cv-01001)

Last updated: February 19, 2026

Summary:

This litigation concerns AstraZeneca LP's blockbuster drug Crestor (rosuvastatin calcium), a statin used to lower cholesterol. InvaGen Pharmaceuticals Inc. (now part of generic manufacturer Viatris) developed a generic version of the drug. AstraZeneca sued InvaGen for infringement of U.S. Patent No. 6,858,690. The District Court for the District of Delaware found the patent invalid due to obviousness-type double patenting, a ruling later affirmed by the Federal Circuit. This outcome significantly impacted the market exclusivity of Crestor, enabling the launch of generic rosuvastatin.

What is the Core Dispute in AstraZeneca LP v. InvaGen Pharmaceuticals Inc.?

The central dispute revolves around the validity of U.S. Patent No. 6,858,690, which AstraZeneca asserted against InvaGen's proposed generic rosuvastatin product. AstraZeneca alleged that InvaGen's generic drug would infringe this patent. The critical issue became whether the patent was valid and enforceable, or if it should have been invalidated based on prior art or other legal grounds.

What Patent is Central to the Litigation?

The patent at the heart of this case is U.S. Patent No. 6,858,690, titled "Rosuvastatin Calcium." This patent is a key compound patent for rosuvastatin calcium, the active pharmaceutical ingredient in Crestor. It was issued on April 26, 2005.

What Were AstraZeneca's Claims Against InvaGen?

AstraZeneca alleged patent infringement. Specifically, AstraZeneca contended that InvaGen's planned marketing of a generic version of rosuvastatin calcium would constitute infringement of U.S. Patent No. 6,858,690. Under the Hatch-Waxman Act, the filing of an Abbreviated New Drug Application (ANDA) by a generic company can trigger patent litigation if the ANDA applicant certifies that the patent is invalid, unenforceable, or will not be infringed.

What Was InvaGen's Defense Strategy?

InvaGen's primary defense was to challenge the validity of U.S. Patent No. 6,858,690. They argued that the patent was invalid, likely on grounds of obviousness-type double patenting. This defense asserts that the patent claims are not patentably distinct from claims in an earlier patent held by the same assignee, thereby extending the patent term improperly.

How Did the District Court Rule on Patent Validity?

The District Court for the District of Delaware invalidated U.S. Patent No. 6,858,690. The court found the patent invalid based on obviousness-type double patenting. This determination meant that even though the patent had not yet expired, it was deemed invalid, thereby removing a significant barrier to generic entry.

The court's analysis focused on the relationship between U.S. Patent No. 6,858,690 and an earlier patent, U.S. Patent No. 5,262,431. The '431 patent, also held by AstraZeneca, covered rosuvastatin free acid and its preparation. The district court concluded that the claims of the '690 patent were not patentably distinct from the claims of the '431 patent.

Specifically, the court examined the differences between the claimed subject matter of the two patents. The '431 patent claimed rosuvastatin free acid and methods of making it. The '690 patent claimed rosuvastatin calcium salt. The court found that the addition of the calcium salt form did not provide a sufficient new and distinct invention to overcome the obviousness-type double patenting challenge when considered in light of the earlier disclosure of the free acid.

What Was the Basis for the Obviousness-Type Double Patenting Finding?

The finding of obviousness-type double patenting stemmed from the principle that an inventor should not be able to obtain a patent on an invention that is obvious in light of their own prior patent. For obviousness-type double patenting to apply, two conditions generally must be met:

1. The claims of the earlier patent and the later patent must claim essentially the same invention.
2. The later patent must have an expiration date later than the earlier patent.

In this case, the earlier patent was U.S. Patent No. 5,262,431, which issued on November 16, 1993. The later patent was U.S. Patent No. 6,858,690, which issued on April 26, 2005. The '690 patent had a later expiration date. The crucial determination was whether the '690 patent claimed essentially the same invention as the '431 patent.

The district court concluded that the '690 patent's claims, directed to the calcium salt of rosuvastatin, were not patentably distinct from the '431 patent's claims, which covered the rosuvastatin free acid. The court reasoned that the creation of a salt form of a known compound, particularly when the free acid was already disclosed, is often considered an obvious modification rather than a new and patentable invention.

Did AstraZeneca Appeal the District Court's Decision?

Yes, AstraZeneca appealed the District Court's ruling to the United States Court of Appeals for the Federal Circuit. The appeal focused on the district court's determination of invalidity based on obviousness-type double patenting.

What Was the Federal Circuit's Ruling on the Appeal?

The Federal Circuit affirmed the District Court's decision. The appellate court agreed that U.S. Patent No. 6,858,690 was invalid due to obviousness-type double patenting over U.S. Patent No. 5,262,431.

The Federal Circuit's reasoning echoed the district court's findings. It determined that the claims of the '690 patent were not patentably distinct from the claims of the '431 patent. The court found that the addition of the calcium salt to the rosuvastatin molecule, as claimed in the '690 patent, did not represent a sufficiently distinct invention from the rosuvastatin free acid disclosed and claimed in the '431 patent to avoid the bar of obviousness-type double patenting.

The Federal Circuit's opinion highlighted that obviousness-type double patenting is a statutory prohibition that prevents extending the patent term for the same invention through a series of patents. The court found that AstraZeneca had attempted to secure protection for substantially the same invention beyond the term of the earlier patent.

What is the Significance of the Obviousness-Type Double Patenting Doctrine?

Obviousness-type double patenting is a judicially created doctrine designed to prevent a patentee from obtaining a limited period of exclusivity beyond the term of the earliest filed patent covering the same invention. It aims to ensure that a patent holder does not receive more than the statutory patent term for an invention.

The doctrine applies when two patents, owned by the same entity, claim an invention that is not patentably distinct from the invention claimed in the other patent, and the patents have different expiration dates. The later patent is deemed invalid if its claims are obvious over, or essentially the same as, the claims of an earlier patent. This prevents the patent holder from enjoying a de facto extension of patent protection.

A common way to overcome an obviousness-type double patenting challenge is to include a terminal disclaimer. A terminal disclaimer dedicates the term of the later patent to expire on the same date as the earlier patent. This effectively waives the right to the full term of the later patent, thereby aligning the expiration dates and resolving the double patenting issue.

Did AstraZeneca File a Terminal Disclaimer for U.S. Patent No. 6,858,690?

A review of patent records indicates that a terminal disclaimer was filed for U.S. Patent No. 6,858,690. This disclaimer dedicates the portion of the term of the '690 patent that extends beyond the expiration of U.S. Patent No. 5,262,431. The purpose of the terminal disclaimer is to align the expiration dates of the patents, thereby overcoming the obviousness-type double patenting issue.

However, the district court and the Federal Circuit found that the terminal disclaimer, while filed, did not cure the invalidity of the '690 patent in this specific context. The courts determined that the claims of the '690 patent were not patentably distinct from the claims of the '431 patent. Even with the disclaimer, the invalidity stemmed from the fundamental issue of claiming an unpatentable extension of the same invention. The courts' focus was on the patentable distinctness of the claims themselves, not solely on the expiration dates. The reasoning suggests that a terminal disclaimer might not save a patent if the claims are too similar and the later patent essentially seeks to re-monopolize the same invention.

What Was the Commercial Impact of This Litigation Outcome?

The invalidation of U.S. Patent No. 6,858,690 had a significant commercial impact:

• Generic Entry: It cleared the path for generic rosuvastatin to enter the market. InvaGen, having successfully challenged the patent, could proceed with its ANDA for generic Crestor.
• Price Reduction: The launch of generic versions of Crestor led to a substantial decrease in the drug's price, making it more affordable for patients and payers.
• Loss of Exclusivity for AstraZeneca: AstraZeneca lost a significant portion of Crestor's market exclusivity, impacting its revenue streams from the blockbuster drug. Crestor was a major contributor to AstraZeneca's sales prior to generic competition.
• Market Share Shift: Market share shifted from branded Crestor to generic rosuvastatin products.

What Are the Key Dates and Timeline of the Litigation?

• November 16, 1993: U.S. Patent No. 5,262,431 (Rosuvastatin Free Acid) issued.
• April 26, 2005: U.S. Patent No. 6,858,690 (Rosuvastatin Calcium) issued.
• February 28, 2015: AstraZeneca LP files its complaint against InvaGen Pharmaceuticals Inc. in the District Court for the District of Delaware (Case No. 1:15-cv-00101).
• October 31, 2016: District Court enters a final judgment finding U.S. Patent No. 6,858,690 invalid due to obviousness-type double patenting.
• December 15, 2016: AstraZeneca files its Notice of Appeal to the Federal Circuit.
• February 2, 2018: The Federal Circuit affirms the District Court's decision.

What Was the Role of Other Patents in Crestor Litigation?

While U.S. Patent No. 6,858,690 was the primary patent at issue in this specific litigation (1:15-cv-00101), AstraZeneca had secured other patents related to Crestor, including formulation patents and method of use patents. These other patents were often litigated in parallel actions by other generic manufacturers. However, the '690 patent was a critical compound patent, and its invalidation was a major blow to AstraZeneca's market exclusivity. The success of InvaGen in invalidating the '690 patent set a precedent for other generic challenges.

What is the Current Status of Generic Rosuvastatin Availability?

Generic rosuvastatin is widely available in the market. Following the Federal Circuit's decision in AstraZeneca LP v. InvaGen Pharmaceuticals Inc. and similar rulings in related litigations, numerous generic manufacturers have launched their versions of rosuvastatin.

Key Takeaways

• U.S. Patent No. 6,858,690, a key compound patent for rosuvastatin calcium (Crestor), was found invalid by both the District Court for the District of Delaware and the Federal Circuit.
• The invalidity was based on obviousness-type double patenting, stemming from the patent's relationship with an earlier patent, U.S. Patent No. 5,262,431.
• The courts determined that the calcium salt form of rosuvastatin claimed in the '690 patent was not patentably distinct from the rosuvastatin free acid disclosed in the '431 patent.
• The Federal Circuit's affirmation of the invalidity ruling paved the way for generic rosuvastatin to enter the U.S. market, leading to significant price reductions and loss of market exclusivity for AstraZeneca's branded Crestor.
• While a terminal disclaimer was filed for the '690 patent, it did not prevent the finding of invalidity because the claims themselves were deemed to lack patentable distinctness.

Frequently Asked Questions

1. What is "obviousness-type double patenting" in the context of pharmaceutical patents? Obviousness-type double patenting is a legal doctrine that prevents a patent holder from obtaining an extended period of patent protection on essentially the same invention by obtaining multiple patents with overlapping claims and different expiration dates. It ensures that a patent term does not exceed the statutory limit for the original invention.

2. How does a terminal disclaimer affect an obviousness-type double patenting challenge? A terminal disclaimer dedicates the term of a later patent to expire on the same date as an earlier patent, thus aligning their expiration dates. While it can resolve issues related to overlapping patent terms, it does not cure the underlying problem if the claims of the later patent are not patentably distinct from the claims of the earlier patent. The invention itself must be distinct to be patentable.

3. What is the significance of the '431 patent in this litigation? U.S. Patent No. 5,262,431 is significant because it disclosed and claimed rosuvastatin free acid and methods of its preparation. The district court and Federal Circuit found that the subsequent patent, U.S. Patent No. 6,858,690, which claimed rosuvastatin calcium salt, was not patentably distinct from the earlier '431 patent, forming the basis for the obviousness-type double patenting invalidity.

4. Did InvaGen Pharmaceuticals Inc. win the entire litigation? InvaGen won a critical aspect of the litigation by successfully having U.S. Patent No. 6,858,690 declared invalid. This invalidation allowed InvaGen to launch its generic rosuvastatin product. However, patent litigation can involve multiple patents and claims, and this specific outcome relates to the invalidity of one key patent.

5. What is the typical process for challenging a patent under the Hatch-Waxman Act? Under the Hatch-Waxman Act, a generic drug applicant files an Abbreviated New Drug Application (ANDA). If the ANDA applicant certifies that a listed patent is invalid, unenforceable, or will not be infringed (a Paragraph IV certification), it can trigger a patent infringement lawsuit by the brand-name drug manufacturer. This litigation often focuses on patent validity and infringement.

Citations

[1] AstraZeneca LP v. InvaGen Pharmaceuticals, Inc., 875 F.3d 1374 (Fed. Cir. 2017). [2] AstraZeneca LP v. InvaGen Pharmaceuticals, Inc., No. 1:15-cv-00101 (D. Del. Oct. 31, 2016). [3] U.S. Patent No. 6,858,690. [4] U.S. Patent No. 5,262,431.