The patent is a narrow, Orange Book-relevant method-of-treatment patent directed to coadministration of elagolix and rifampin in endometriosis patients. Its two claims require specific elagolix dosing, specific rifampin exposure, and pharmacokinetic increases measured against elagolix administered alone. It does not broadly cover elagolix, Orilissa, endometriosis treatment, or all drug interactions. The principal commercial risk is a Paragraph IV challenge directed to claim construction, pharmacokinetic variability, obviousness, and whether the FDA-approved label induces performance of the claimed regimen.

United States Patent 10,537,572: Elagolix, Rifampin, and Endometriosis Patent Landscape

What does US Patent 10,537,572 protect?

US Patent 10,537,572 protects two dosing methods for treating endometriosis with elagolix sodium in the presence of rifampin.

Claim	Elagolix regimen	Rifampin regimen	Required pharmacokinetic result
1	150 mg free-acid equivalent, orally once daily	One 600 mg dose	Elagolix Cmax increases 4.4-fold and AUC increases 5.6-fold versus elagolix alone
2	150 mg free-acid equivalent, orally once daily	600 mg once daily	Elagolix Cmax increases 2.0-fold and AUC increases 1.65-fold versus elagolix alone

The patent claims are method claims. They require performance of the complete combination regimen. A party does not infringe merely by selling elagolix, selling rifampin, treating endometriosis, or conducting a separate elagolix pharmacokinetic study.

The claimed active ingredient is elagolix, chemically identified in the claims as a particular sodium salt of the specified substituted pyrimidinedione compound. The claims do not use the brand name Orilissa, but Orilissa contains elagolix sodium.

What are the key claim limitations in US 10,537,572?

Claim 1: Single-dose rifampin interaction

Claim 1 requires all of the following:

A patient with endometriosis.
Oral administration of elagolix.
Once-daily administration of elagolix.
Elagolix sodium in an amount equivalent to 150 mg of elagolix free acid.
Administration of a single 600 mg dose of rifampin.
A 4.4-fold increase in elagolix maximum plasma concentration.
A 5.6-fold increase in elagolix plasma AUC.
Comparison against elagolix administered without the specified rifampin exposure.

The claim is therefore narrower than a standard drug-interaction claim. It does not cover any increase in elagolix exposure. It specifies two numerical pharmacokinetic outcomes.

Claim 2: Repeated rifampin interaction

Claim 2 uses the same elagolix treatment regimen but requires 600 mg of rifampin once daily. It specifies lower exposure increases than claim 1:

Cmax: 2.0-fold.
AUC: 1.65-fold.

The distinction reflects the different pharmacology of single-dose and repeated rifampin exposure. Rifampin can produce acute transporter or enzyme-inhibition effects while repeated administration produces enzyme induction. The patent claims capture both exposure profiles.

How strong is the patent estate for US 10,537,572?

The individual claims are narrow but technically specific. Their strength depends less on broad market coverage than on whether a generic applicant’s proposed labeling or clinical use necessarily produces the claimed regimen.

Strength factor	Assessment
Claim specificity	High. The claims identify the active ingredient, salt, dose, route, frequency, rifampin dose, and PK values.
Breadth	Low. The claims cover two specific regimens rather than a broad elagolix use.
Detectability	Moderate to high. Elagolix and rifampin use can be identified from medical records, labeling, prescribing data, and clinical studies.
Label-based infringement risk	Potentially limited if the proposed label omits rifampin coadministration.
Validity risk	Meaningful because the claims combine a known drug, a known inducer/inhibitor, and pharmacokinetic results.
Design-around potential	High. Changes in dose, rifampin schedule, treatment indication, or labeling may avoid literal infringement.
Commercial blocking effect	More limited than a core compound or formulation patent.

The PK limitations may improve the patent’s written-description and enablement position if the specification reports the claimed clinical interaction data. They also create litigation risk because PK values vary by subject, assay, population, food conditions, sampling schedule, and statistical method.

When does US Patent 10,537,572 expire?

The patent issued in 2020 and is directed to a later-developed method of using elagolix rather than the original elagolix compound. Its nominal patent term is expected to extend into the mid-2030s, subject to the recorded priority chain, patent term adjustment, terminal disclaimers, and any applicable patent-term extension.

The legally operative expiration date should be taken from the USPTO Patent Center term calculation and the FDA Orange Book listing rather than inferred solely from the issue date. A patent’s expiration date can differ from a simple 20-year calculation because of patent-term adjustment or an effective terminal disclaimer.[1][2]

The patent does not itself determine when generic elagolix can launch. Launch timing depends on the full Orilissa patent list, NDA exclusivity, any Paragraph IV litigation, settlement terms, and whether the generic applicant’s label practices fall within the asserted claims.

What is the FDA regulatory status of Orilissa and elagolix?

The FDA approved Orilissa tablets for the management of moderate to severe pain associated with endometriosis on July 23, 2018. The product contains elagolix sodium and is marketed in 150 mg and 200 mg tablet strengths.

The principal labeled regimens are:

Orilissa strength	Labeled regimen	Typical labeled duration
150 mg	Once daily	Up to 24 months, subject to labeling restrictions
200 mg	Twice daily	Up to 6 months

The approved label includes warnings and interaction information involving strong CYP3A inhibitors, strong CYP3A inducers, and other medicines. The patent’s rifampin regimens are pharmacokinetic combinations and are not equivalent to the ordinary labeled endometriosis regimen.[3]

The distinction matters under Hatch-Waxman. A generic applicant may seek approval for a 150 mg elagolix product while attempting to omit or carve out a patented interaction-related use. Whether a carve-out succeeds depends on the proposed labeling, prescribing information, promotional conduct, and the factual relationship between the label and the claimed method.

What is the Orange Book status of US 10,537,572?

US Patent 10,537,572 is relevant to the Orange Book analysis because it concerns an approved drug product and a method of using elagolix in endometriosis treatment. Orange Book listing status, use code, and delisting status are controlling for Paragraph IV mechanics.

An Orange Book-listed method patent can trigger a certification requirement for an ANDA applicant. The applicant may certify that the patent has expired, will not be infringed, is invalid, or is not eligible for listing. A Paragraph IV notice to the NDA holder and patent owner can create a 30-month stay if statutory requirements are met and litigation is timely filed.[4]

The practical questions are:

Whether US 10,537,572 is currently listed against the relevant Orilissa NDA.
Whether the listed use code accurately corresponds to the patent claims.
Whether the patent remains in force on the proposed ANDA filing date.
Whether the generic label includes the rifampin-related use.
Whether the NDA holder asserts induced infringement based on the full label.

The patent should not be treated as a blanket barrier to generic elagolix. Its value is tied to the exact listed use and the scope of the generic label.

What generic entry risks exist for elagolix?

A generic applicant has several potential pathways.

Paragraph IV challenge

A Paragraph IV applicant could argue that the claims are:

Invalid for obviousness because the interaction between elagolix and rifampin was predictable from known CYP3A and transporter pharmacology.
Anticipated by clinical pharmacokinetic studies or prior publications reporting the same dose combinations and exposure ratios.
Indefinite because the claims do not sufficiently define the reference condition for “elagolix alone.”
Not infringed because the proposed label does not instruct use with rifampin.
Not infringed because the generic product is not marketed for the claimed method.
Invalid for lack of written description or enablement if the specification does not support the claimed PK values across the full scope.

The patent owner would counter that the exact exposure changes, particularly the difference between single-dose and repeated rifampin, were experimentally demonstrated and are not established merely by knowing rifampin’s general enzyme effects.

Section viii carve-out

A generic applicant may seek a “skinny label” that omits a patented method of use. This strategy is most effective when the omitted use can be separated from the remaining approved indications and the product label does not otherwise encourage the patented conduct.

The claims create a potential labeling problem because the claimed regimen is not simply “use elagolix for endometriosis.” It requires coadministration with rifampin and specific PK outcomes. A label that omits rifampin instructions may materially reduce induced-infringement exposure.

Launch at risk

A generic applicant could launch before patent expiration after receiving approval, subject to litigation risk. Such a launch would expose the applicant to potential damages, an injunction, and business disruption if the patent survives and the court finds infringement.

What patent litigation affects elagolix and Orilissa?

The principal litigation risk under US 10,537,572 would arise from an ANDA Paragraph IV filing or a dispute over Orange Book listing. The relevant litigation questions would include:

Whether the patent is listed for the approved elagolix product.
Whether the generic applicant’s proposed label includes the claimed rifampin regimen.
Whether the PK limitations are limitations of treatment or merely result characteristics.
Whether “relative to administration of elagolix alone” identifies a legally definite comparator.
Whether the claims require actual measured PK results in each treated patient.
Whether the claims are infringed when the exposure increase is a population-average result rather than an individual patient result.
Whether the generic’s manufacturing and labeling create direct or induced infringement.

The claim language gives the patent owner a narrow infringement theory. It also gives the accused generic applicant several noninfringement arguments, especially if the label does not recommend rifampin coadministration.

No biosimilar pathway applies. Elagolix is a chemically synthesized small molecule, so competitive products would generally proceed through the ANDA pathway rather than the abbreviated biologics license application pathway.

What other patents protect elagolix and Orilissa?

The broader elagolix patent landscape normally includes several layers:

Patent layer	Typical subject matter	Relevance to generic entry
Core compound patents	Elagolix chemical structure and related compounds	Potentially the earliest and broadest protection, but often earlier-expiring
Salt and solid-form patents	Elagolix sodium, crystalline forms, polymorphs	Can affect active-ingredient manufacture
Pharmaceutical composition patents	Tablets, excipients, dosage forms, stability	Relevant to product formulation and ANDA sameness
Treatment patents	Endometriosis, uterine fibroids, dosing schedules	Can support Orange Book use-code protection
Drug-interaction patents	Elagolix with rifampin or other interacting drugs	Narrower, fact-intensive method claims
Manufacturing patents	Synthesis, intermediates, purification, salt formation	Can create supply-chain barriers even if not Orange Book-listed

US Patent 10,537,572 is in the drug-interaction and method-of-treatment category. It does not replace core compound, formulation, or solid-form protection. A complete freedom-to-operate analysis requires review of the entire US family, continuations, divisionals, terminal disclaimers, and Orange Book records.

How does elagolix compare with competing endometriosis drugs?

Product	Active ingredient	Regulatory category	Key patent-risk profile
Orilissa	Elagolix	Small-molecule oral GnRH antagonist	Core compound, formulation, method, and interaction patents
Myfembree	Relugolix, estradiol, norethindrone acetate	Combination oral GnRH antagonist product	Combination, formulation, dosing, and method patents
Lupron Depot	Leuprolide acetate	Peptide GnRH agonist depot	Depot formulation, device, manufacturing, and use patents
Aygestin and progestin products	Norethindrone acetate and related agents	Hormonal therapy	Older compound and formulation estates
Generic hormonal therapies	Various	ANDA products	Lower barriers in older, off-patent products

Orilissa’s differentiation is oral, nonpeptide GnRH antagonism and dose-dependent suppression. Myfembree competes in overlapping endometriosis and uterine-fibroid markets but uses a combination approach with hormonal add-back therapy. The patent risk for US 10,537,572 is specific to elagolix and does not extend to relugolix or leuprolide products.

What licensing deals are relevant to elagolix?

Neurocrine Biosciences developed elagolix and licensed development and commercialization rights to AbbVie. The parties announced a global collaboration covering elagolix and related GnRH antagonists, with AbbVie assuming specified development and commercialization responsibilities and Neurocrine receiving upfront, milestone, and royalty economics.[5]

The commercial allocation between AbbVie and Neurocrine does not expand the legal scope of US Patent 10,537,572. It does affect enforcement authority, ownership records, royalty economics, and the identity of the party likely to participate in Orange Book or ANDA litigation.

What manufacturing and IP barriers affect generic elagolix?

A generic applicant must address more than the interaction patent.

Potential manufacturing barriers include:

Access to validated elagolix sodium synthesis.
Control of impurities and stereochemical purity.
Salt formation and crystallinity.
Tablet dissolution and stability.
Bioequivalence at the 150 mg and 200 mg strengths.
Supplier qualification for active pharmaceutical ingredient.
Freedom to operate under process and intermediate patents.

US Patent 10,537,572 is unlikely to block manufacture of elagolix by itself. It could, however, increase risk for a generic label or clinical program that studies or promotes rifampin coadministration.

What is the likely commercial exposure from US 10,537,572?

The patent’s direct revenue exposure is narrower than the full Orilissa franchise because the claims require rifampin. Most endometriosis patients do not receive rifampin, and rifampin is not a routine component of endometriosis therapy.

Its commercial importance is therefore strategic rather than volume-based:

It may delay or complicate an ANDA approval if Orange Book listed.
It may require a label carve-out.
It can increase Paragraph IV litigation cost.
It may protect a regulatory interaction study or a specific prescribing scenario.
It does not independently preserve all branded elagolix sales.

The core commercial patent risk for Orilissa would usually come from the broader compound, formulation, and standard dosing patents, not from the two rifampin-specific claims alone.

What are the principal invalidity and infringement issues?

Validity issues

The strongest potential validity arguments are obviousness and indefiniteness.

Obviousness would focus on whether a skilled pharmacologist would have expected rifampin to alter elagolix exposure and whether the exact fold changes were predictable. The patent owner would rely on the magnitude and direction of the observed effects, especially the contrast between single-dose and repeated rifampin.

Indefiniteness would focus on:

The comparator represented by “elagolix alone.”
Whether the fold-change values are population means or individual outcomes.
The permitted statistical variation around 4.4-, 5.6-, 2.0-, and 1.65-fold values.
Whether the claims require measurement in the patient receiving treatment.

Infringement issues

Literal infringement requires proof of every claim limitation. A generic may avoid infringement by:

Omitting rifampin from labeling.
Using a different rifampin dose or schedule.
Using a different elagolix dose.
Avoiding the claimed endometriosis indication.
Demonstrating that its label does not produce or report the claimed PK results.
Arguing that the claimed numerical results are not guaranteed for each patient.

The doctrine of equivalents may be limited by the precise numerical and dosing language, prosecution history, and the public-notice function of the claims.

Key Takeaways

US Patent 10,537,572 covers two narrow elagolix-rifampin treatment regimens for endometriosis.
Claim 1 covers a single 600 mg rifampin dose with 4.4-fold Cmax and 5.6-fold AUC increases.
Claim 2 covers 600 mg rifampin once daily with 2.0-fold Cmax and 1.65-fold AUC increases.
The patent does not broadly cover elagolix, Orilissa, endometriosis treatment, or all drug interactions.
The principal Paragraph IV issues are obviousness, indefiniteness, PK variability, and induced infringement.
The patent’s commercial value is narrower than that of a core compound or formulation patent.
No biosimilar pathway applies because elagolix is a small molecule.
Generic entry depends on the entire Orilissa patent estate, FDA exclusivity, Orange Book status, label carve-outs, and any ANDA settlement.
The patent’s exact enforceable expiration date must be determined from the USPTO term record and current Orange Book data.

FAQs About US Patent 10,537,572 and Elagolix

Can a generic sell elagolix without infringing US Patent 10,537,572?

Potentially yes. A generic that does not label, promote, or direct use of elagolix with the claimed rifampin regimens may have a substantial noninfringement position. Other Orilissa patents could still block launch.

Does US Patent 10,537,572 cover the 150 mg Orilissa dose by itself?

No. The claims require the 150 mg elagolix regimen together with specified rifampin exposure and specified PK results.

Is rifampin an approved treatment for endometriosis?

No. Rifampin is an antibacterial drug. Its relevance to the patent is as a pharmacokinetic interacting drug, not as an endometriosis therapy.

Could a Paragraph IV challenger argue that the patent claims are obvious?

Yes. A challenger could argue that rifampin’s known effects on drug-metabolizing enzymes and transporters made interaction with elagolix predictable. The patent owner would rely on the specific and counterintuitive exposure results.

Does the patent protect elagolix manufacturing?

No. The quoted claims are method-of-treatment claims. Manufacturing protection would require separate claims directed to synthesis, intermediates, salt formation, solid forms, or pharmaceutical compositions.

References

United States Patent and Trademark Office. (2020). United States Patent No. 10,537,572, methods of treating endometriosis.
United States Patent and Trademark Office. (n.d.). Patent Center: Patent term adjustment and application prosecution records.
U.S. Food and Drug Administration. (2023). Orilissa (elagolix) prescribing information. AbbVie Inc.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book.
AbbVie Inc. & Neurocrine Biosciences, Inc. (2010). AbbVie and Neurocrine enter global collaboration for elagolix. Corporate transaction announcement.
Drug Price Competition and Patent Term Restoration Act, 21 U.S.C. §§ 355(j), 355(b)(2).

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Abbvie	ORILISSA	elagolix sodium	TABLET;ORAL	210450-001	Jul 23, 2018		RX	Yes	No	⤷ Start Trial	⤷ Start Trial				MANAGEMENT OF MODERATE TO SEVERE PAIN ASSOCIATED WITH ENDOMETRIOSIS USING 150MG ELAGOLIX WHILE CO-ADMINISTERING RIFAMPIN	⤷ Start Trial
>Applicant	>Tradename	>Generic Name	>Dosage	>NDA	>Approval Date	>TE	>Type	>RLD	>RS	>Patent No.	>Patent Expiration	>Product	>Substance	>Delist Req.	>Patented / Exclusive Use	>Submissiondate

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Australia	2016317955	⤷ Start Trial
Australia	2021204104	⤷ Start Trial
Canada	3002791	⤷ Start Trial
European Patent Office	3344245	⤷ Start Trial
Hong Kong	1258062	⤷ Start Trial
World Intellectual Property Organization (WIPO)	2017040841	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 10,537,572

Which drugs does patent 10,537,572 protect, and when does it expire?

Summary for Patent: 10,537,572