US Patent 7,427,638: Apremilast Claims, Expiration, Orange Book Status and Generic Risk
US Patent 7,427,638 covers stereomerically pure apremilast, its pharmaceutically acceptable salts, solvates and hydrates, together with pharmaceutical compositions and unit-dose formulations. The patent issued to Celgene and expired on March 17, 2024, absent a later enforceable extension. Its claims were important because they covered the active enantiomer itself, not only a particular disease indication or formulation. The patent no longer creates an enforceable US patent barrier to generic apremilast launch.
What drug does US Patent 7,427,638 protect?
The claimed compound is apremilast, chemically identified as:
2-[1-(3-ethoxy-4-methoxyphenyl)-2-methylsulfonylethyl]-4-acetylaminoisoindoline-1,3-dione
The patent claims the stereomerically pure (+) isomer, substantially free of the corresponding (-) isomer. Apremilast is marketed in the United States as Otezla by Amgen. It is an oral phosphodiesterase-4 inhibitor approved for plaque psoriasis, psoriatic arthritis and oral ulcers associated with Behçet's disease. [1]
Chemical and regulatory identity
| Item |
Description |
| Active ingredient |
Apremilast |
| Chemical class |
Isoindoline-1,3-dione derivative |
| Pharmacology |
Phosphodiesterase-4 inhibitor |
| US brand |
Otezla |
| Original US sponsor |
Celgene |
| Current commercial owner |
Amgen |
| Primary dosage forms |
Immediate-release tablets |
| FDA NDA |
205437 |
| Patent analyzed |
US 7,427,638 B2 |
| Patent issue date |
September 23, 2008 |
| Patent expiration |
March 17, 2024 |
| FDA approval of Otezla |
March 21, 2014 |
What are the independent claims in US Patent 7,427,638?
Claims 1, 7 and 13 provide the principal scope.
Claim 1: pharmaceutical composition
Claim 1 covers a pharmaceutical composition comprising:
- stereomerically pure (+)-apremilast, or a pharmaceutically acceptable salt, solvate or hydrate; and
- a pharmaceutically acceptable carrier, excipient or diluent.
The claim is composition-based. A product containing the claimed enantiomer and an ordinary pharmaceutical excipient can fall within the claim. The claim does not require a particular disease, mechanism of action, manufacturing process, tablet design or dosage strength.
Claim 7: single-unit dosage form
Claim 7 covers a single-unit dosage form containing approximately 1 mg to 1,000 mg of stereomerically pure (+)-apremilast, or a covered salt, solvate or hydrate, with a pharmaceutical carrier, excipient or diluent.
This claim is narrower than claim 13 because it requires a dosage form and a quantity range. It is broader than claims 11 and 12 because those dependent claims narrow the quantity to approximately 5 mg to 500 mg and 10 mg to 200 mg, respectively.
Claim 13: the active compound
Claim 13 is the broadest and commercially most important claim. It covers:
- stereomerically pure (+)-apremilast;
- apremilast substantially free of the (-) isomer;
- pharmaceutically acceptable salts;
- solvates and hydrates; and
- language referring to a pharmaceutically acceptable metabolite.
Unlike claims 1 through 12, claim 13 does not require a pharmaceutical carrier, excipient, diluent or dosage form. It is a product claim directed to the active molecular entity.
How do the dependent claims narrow the patent scope?
The dependent claims create nested protection around route, dose and dosage form.
| Claims |
Limitation |
| 1 |
Composition containing stereomerically pure (+)-apremilast and excipient |
| 2 |
Suitable for parenteral, transdermal, mucosal, nasal, buccal, sublingual or oral administration |
| 3 |
Suitable for oral administration |
| 4 |
1 mg to 1,000 mg |
| 5 |
5 mg to 500 mg |
| 6 |
10 mg to 200 mg |
| 7 |
Single-unit dosage form containing 1 mg to 1,000 mg |
| 8 |
Broad administration-route limitation |
| 9 |
Capsule or tablet |
| 10 |
Aerosol |
| 11 |
Approximately 5 mg to 500 mg |
| 12 |
Approximately 10 mg to 200 mg |
| 13 |
Stereomerically pure (+)-apremilast compound |
Oral products
Claims 3, 9, 11 and 12 are particularly relevant to Otezla-type products. A conventional oral tablet containing 10 mg, 20 mg or 30 mg of apremilast would fall within the stated dosage ranges if the active ingredient is the claimed (+) enantiomer and the other claim elements are present.
The patent does not require the product to use a specific excipient, coating, dissolution profile or tablet manufacturing process. That makes the claims more difficult to design around than a narrowly drafted formulation claim.
The aerosol limitation
Claim 10 depends on claim 9, which refers to a capsule or tablet, and then adds an aerosol limitation. The wording is technically unusual because an aerosol ordinarily is not a capsule or tablet. The scope of this claim would depend on claim construction and the specification. It has limited commercial importance because Otezla is an oral tablet, not an aerosol product.
Dose ranges
The dose claims use overlapping ranges:
- Claim 4: 1 mg to 1,000 mg
- Claim 5: 5 mg to 500 mg
- Claim 6: 10 mg to 200 mg
- Claim 11: approximately 5 mg to approximately 500 mg
- Claim 12: approximately 10 mg to approximately 200 mg
The ranges encompass common apremilast tablet strengths. They do not, however, independently protect a dose without the required active stereoisomer and formulation elements.
Does US Patent 7,427,638 cover racemic apremilast?
The patent is directed to the (+) stereoisomer, not an undifferentiated racemic mixture.
A product containing only the (-) isomer would not meet the express stereochemical limitation. A racemic product would present a more complex infringement analysis. Literal infringement would depend on whether the racemate is legally treated as containing the claimed stereomerically pure compound, which is generally not established merely because the racemate contains the (+) enantiomer as one component.
The principal commercial risk was therefore directed at manufacturers producing the same enantiomer used in Otezla. Generic apremilast products use the active enantiomer rather than a racemic substitute because the FDA-approved drug, clinical data and labeling are based on apremilast as marketed.
When did US Patent 7,427,638 expire?
US Patent 7,427,638 expired on March 17, 2024, based on the patent term calculated from its earliest effective US nonprovisional filing date. The patent was not an active barrier after that date unless a specific statutory extension applied. [2]
| Milestone |
Date |
| Earliest effective priority date |
March 17, 2003 |
| Patent issue |
September 23, 2008 |
| Otezla FDA approval |
March 21, 2014 |
| Five-year NCE exclusivity period |
Ended in 2019 |
| US patent expiration |
March 17, 2024 |
The patent was issued more than five years before Otezla approval. As a result, the remaining patent term after FDA approval was shorter than the five-year new chemical entity exclusivity period. FDA regulatory exclusivity and patent exclusivity are separate rights. NCE exclusivity prevented certain abbreviated applications from relying on the reference product for five years, while the patent created a separate infringement barrier.
What was the Orange Book status of US Patent 7,427,638?
US Patent 7,427,638 was listed in the FDA Orange Book for Otezla. Orange Book listing connected the patent to the approved drug and enabled the patent holder to invoke the Hatch-Waxman certification and litigation framework during the patent’s enforceable term. [3]
The listing did not mean that every claim applied to every possible apremilast product. It meant that the patent holder identified the patent as claiming the drug substance, drug product or approved use associated with the NDA.
After expiration, the patent could remain visible in historical Orange Book records, but it no longer provided an enforceable patent term. An expired listing does not independently prevent FDA approval of an ANDA.
Were Paragraph IV challenges relevant to this patent?
Yes. Before expiration, an ANDA applicant could submit a Paragraph IV certification asserting that the patent was invalid, unenforceable or would not be infringed. The filing of a proper Paragraph IV notice could trigger patent litigation under 21 U.S.C. § 271(e)(2), and a timely lawsuit could create a 30-month FDA approval stay. [4]
After March 17, 2024, a Paragraph IV challenge to this patent no longer has the same commercial function because the patent has expired. Generic applicants can instead submit a certification reflecting expiration, subject to the status of other unexpired Otezla patents.
The relevant competitive issue shifted from the 7,427,638 compound patent to later patents covering formulations, polymorphs, manufacturing processes or approved methods of use.
What other patents protect Otezla and apremilast?
The apremilast estate includes more than the patent analyzed here. The principal categories are:
| Patent category |
Typical subject matter |
Commercial effect |
| Compound patents |
Apremilast and related isoindoline derivatives |
Broadest molecular protection |
| Stereochemical patents |
Enantiomerically enriched apremilast |
Protects the marketed active form |
| Composition patents |
Apremilast with excipients or dosage ranges |
Targets finished pharmaceutical products |
| Polymorph patents |
Crystalline or solid-state forms |
Can restrict particular API manufacturing routes |
| Method-of-use patents |
Psoriasis, psoriatic arthritis, Behçet's disease or other inflammatory conditions |
Relevant to labeled-use substitution |
| Manufacturing patents |
Resolution, synthesis, purification or crystallization |
Can create supply-chain barriers |
| Regulatory patents |
Patents listed against the Otezla NDA |
Can delay or complicate generic approval |
US 7,427,638 is strongest as a molecule and composition patent. It is less dependent on a particular indication than a method-of-use patent and less vulnerable to routine formulation redesign than a narrowly drafted excipient or release-profile patent.
Formulation patents
A later formulation patent may require a specific excipient combination, particle size, polymorph, dissolution characteristic or manufacturing process. Such claims can be avoided more readily than claim 13 if the generic sponsor uses a different formulation and does not practice the claimed solid-state or process limitations.
The existence of a later formulation patent does not revive the expired compound patent. It must be analyzed separately for claim scope, Orange Book listing, term, terminal disclaimers and litigation status.
Method-of-use patents
Method-of-use patents may cover administration of apremilast for psoriasis, psoriatic arthritis, Behçet's disease or related inflammatory conditions. A generic sponsor may attempt a section viii “skinny label” strategy by carving out patented indications, although the feasibility depends on the patent claims, FDA labeling and the commercial significance of the omitted use.
The product claim in claim 13 does not depend on a treatment indication. A method-of-use carveout would not avoid a valid product claim, but it can be relevant to later use patents.
How strong was the patent estate for apremilast?
US 7,427,638 was commercially strong during its term for four reasons:
- Claim 13 covered the active stereoisomer itself.
- Claims 1 through 12 covered ordinary pharmaceutical compositions and dosage forms.
- The claims covered salts, solvates and hydrates.
- The patent did not depend on a particular disease indication.
Its principal weaknesses were term-related. The patent expired in 2024, and the claims did not provide continuing protection against products that use different active ingredients, noninfringing formulations or legally permissible alternative manufacturing processes after expiration.
The patent also contains drafting vulnerabilities. The use of “stereomerically” instead of the conventional “stereomerically” or “stereochemically” terminology, the unusual aerosol dependency and the reference to a “pharmaceutically acceptable metabolite” could have required prosecution-history and claim-construction analysis. Those issues did not change the central commercial fact that the patent covered the marketed apremilast active ingredient during its enforceable term.
Which companies challenged or competed against the Otezla patent estate?
The relevant competitive group includes:
- Amgen, which acquired Otezla from Celgene;
- Celgene, the original developer and patent holder;
- generic manufacturers filing apremilast ANDAs;
- API suppliers producing apremilast or intermediates;
- companies pursuing alternative PDE4 inhibitors or different psoriasis therapies.
A generic applicant challenging the expired patent would now focus on any later unexpired patents rather than US 7,427,638. Publicly reported settlements, launch dates and litigation outcomes must be assessed patent by patent because a settlement involving a later formulation or method patent does not alter the legal status of the expired compound patent.
What is the commercial exposure from apremilast patent expiry?
Otezla generated approximately $3.1 billion in 2023 product sales, according to Amgen's annual report. [5] The expiration of the principal compound and composition patent creates material erosion risk because generic entrants can compete with the same active ingredient, dosage strengths and oral route.
Generic launch scenarios include:
| Scenario |
Likely effect |
| Multiple immediate launches after all blocking patents expire |
Rapid price and market-share erosion |
| Limited launches under settlement agreements |
Staged erosion |
| Later formulation or method patents remain enforceable |
Delayed or indication-specific competition |
| Authorized generic launch |
Amgen may retain volume while reducing third-party share |
| Manufacturing constraints |
Slower supply ramp despite legal entry |
The greatest exposure is in commercially important oral indications where generic substitution is permitted. Otezla's clinical familiarity and established reimbursement position may preserve some branded demand, but those factors do not extend patent exclusivity.
What geographic protection did US Patent 7,427,638 provide?
The patent provided protection only in the United States. Foreign counterparts required separate national patents, separate expiration analysis and separate litigation assessments.
A US expiration did not automatically terminate European, Canadian, Japanese, Chinese or other national rights. Conversely, a foreign patent expiry did not authorize US commercialization. Patent term adjustments, supplementary protection certificates, pediatric extensions, terminal disclaimers and local regulatory exclusivity must be assessed by jurisdiction.
What generic launch risks remain after expiration?
The expired patent no longer blocks ordinary US generic apremilast on its own. Residual risks may arise from:
- later Orange Book-listed patents;
- polymorph or solid-state claims;
- formulation patents;
- manufacturing-process patents;
- method-of-use patents;
- trade-secret restrictions on API production;
- FDA requirements for bioequivalence and labeling;
- settlement agreements affecting launch timing;
- supply agreements or authorized-generic strategies.
These risks are separate from the legal scope of US 7,427,638. The patent itself does not provide continuing protection for Otezla after its expiration date.
Key Takeaways
- US 7,427,638 covers stereomerically pure (+)-apremilast, including its salts, solvates and hydrates.
- Claim 13 is the central product claim and does not require a carrier or dosage form.
- Claims 1 through 12 cover pharmaceutical compositions, unit-dose products, oral administration and overlapping dose ranges.
- The patent covered the active ingredient used in Otezla rather than only a particular indication.
- The patent expired on March 17, 2024.
- Its historical Orange Book listing does not create a current enforceable barrier after expiration.
- Current generic risk depends on later apremilast patents, including formulation, polymorph, method-of-use and manufacturing claims.
- Otezla's approximately $3.1 billion in 2023 sales create substantial commercial exposure to generic competition.
- Foreign patent rights and regulatory exclusivity must be analyzed separately from the US patent.
FAQs
Does US 7,427,638 cover Otezla 10 mg, 20 mg and 30 mg tablets?
Yes, during the patent term, those oral dosage forms were within the practical scope of the composition and dosage-form claims if they contained the claimed stereomerically pure (+)-apremilast and pharmaceutical excipients.
Can a generic company avoid US 7,427,638 by using a different excipient?
Changing excipients could avoid some composition claims only if the resulting product no longer meets the relevant limitations. It would not avoid claim 13, which is directed to the active compound itself.
Does patent expiration eliminate FDA exclusivity for Otezla?
No. Patent expiration and FDA regulatory exclusivity are separate. Otezla's five-year new chemical entity exclusivity expired years before the 2024 patent expiration.
Is a biosimilar pathway relevant to apremilast?
No. Apremilast is a small-molecule drug, so competitors generally use the ANDA pathway rather than the biosimilar pathway under the Biologics Price Competition and Innovation Act.
Does expiration of US 7,427,638 eliminate all Otezla patent risk?
No. It eliminates the barrier created by that patent. Later patents covering formulations, polymorphs, approved uses or manufacturing methods may present separate risks.
References
- U.S. Food and Drug Administration. (2024). Otezla (apremilast) prescribing information.
- United States Patent and Trademark Office. (2008). U.S. Patent No. 7,427,638, stereomerically pure derivatives and pharmaceutical compositions.
- U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book.
- 21 U.S.C. § 355(j); 35 U.S.C. § 271(e)(2).
- Amgen Inc. (2024). 2023 annual report.
