United States Patent 5,756,513: Scope, Claim Analysis, Expiration, and Patent Landscape

U.S. Patent No. 5,756,513 covers timed, daily administration of a dopamine agonist, particularly bromocriptine, to modify prolactin or prolactin-and-cortisol rhythms and improve metabolic parameters such as insulin sensitivity, hyperglycemia, hyperinsulinemia, triglycerides, and body-fat stores. The patent is expired. Its claims do not provide current U.S. exclusivity for bromocriptine, Cycloset, or comparable metabolic treatments.

What does U.S. Patent 5,756,513 cover?

The patent covers a method-of-treatment regimen with four principal limitations:

The patient is a human subject requiring treatment.
The active agent is a dopamine agonist.
Administration occurs daily during a morning window, beginning shortly after awakening and extending to five hours after awakening.
The dose is approximately 3 to 40 micrograms per pound of body weight, with treatment continuing long enough to produce specified metabolic effects.

The patent is directed to chronobiological treatment rather than to a new dopamine agonist molecule, a particular tablet composition, or a manufacturing process.

Patent	Title	Issue date	Principal subject matter	Current U.S. status
U.S. 5,756,513	Method of treating diabetes with dopamine agonists	May 26, 1998	Morning administration of dopamine agonists to modify hormonal rhythms and improve metabolic control	Expired

The patent’s claims encompass bromocriptine but are not limited to bromocriptine. Claim 7 lists multiple ergoline and related dopamine agonists, while claims 16 through 20 narrow the treatment to bromocriptine in specified patient populations.

When did U.S. Patent 5,756,513 expire?

The patent’s enforceable term ended in 2015. Because the application falls within the transition rules applicable to certain pre-June 8, 1995 filings, the relevant term was generally 17 years from grant rather than 20 years from the earliest priority date. The patent issued on May 26, 1998, placing the ordinary expiration date at approximately May 26, 2015, subject to any applicable patent-term adjustment or disclaimer.

Event	Date
Earliest priority date reported for the patent family	June 15, 1993
U.S. patent issued	May 26, 1998
Ordinary 17-year expiration calculation	May 26, 2015
Status as of 2026	Expired and unavailable for new enforcement

The expiration eliminates infringement risk from practicing the claims in the United States. It does not invalidate later patents that may claim particular bromocriptine formulations, dosing schedules, indications, or manufacturing techniques.

How broad is independent claim 1?

Claim 1 is the patent’s central claim. It is broad as to the identity of the dopamine agonist and the metabolic endpoint, but narrow as to timing and dose.

Claim 1 limitations

Limitation	Scope implication
“Process for therapeutically modifying and resetting” hormonal rhythms	Requires a treatment objective involving prolactin or prolactin and glucocorticosteroid rhythms
Human subject in need of treatment	Excludes nonhuman treatment and ordinary laboratory administration
Dopamine agonist	Covers a functional drug class rather than one compound
Daily administration	Requires repeated daily dosing
Shortly after awakening through five hours after awakening	Creates a morning administration limitation tied to the patient’s awakening time
About 3 to 40 micrograms per pound	Approximately 6.6 to 88 micrograms per kilogram
Sufficient treatment duration	Requires treatment long enough to produce one or more claimed metabolic outcomes
Improved insulin sensitivity, suppressed hyperinsulinemia, reduced hyperglycemia, or both	Defines the therapeutic result

The claim is not limited to diabetes. The endpoint language includes insulin sensitivity and several metabolic abnormalities that may occur in obese, insulin-resistant, or prediabetic subjects.

The phrase “about” creates tolerance around the dose range. A court would ordinarily evaluate the phrase in light of the specification, prosecution history, measurement precision, and evidence concerning clinical equivalence. Since the patent is expired, this construction has no current U.S. enforcement consequence.

What dopamine agonists are protected by claim 7?

Claim 7 identifies the principal active-agent class and lists specific compounds or compound classes:

6-methyl-8 beta-carbobenzyloxy-aminoethyl-10 alpha-ergoline
1,6-dimethyl-8 beta-carbobenzyloxy-aminomethyl-10 alpha-ergoline
8-acylaminoergolenes
Ergocornine
9,10-dihydroergocornine
Bromocriptine
D-2-halo-6-alkyl-8-substituted ergolines

The claim is a dependent claim, so every limitation of claim 1 remains applicable. Claim 7 therefore does not cover the listed compounds in all uses. It covers their daily morning administration, at the claimed weight-based dose, for the stated hormonal and metabolic purposes.

Bromocriptine is the commercially significant compound in this claim set. The patent does not claim bromocriptine as a chemical entity. It claims a particular therapeutic use and administration schedule.

What do claims 2 through 6 add?

Claims 2 through 6 refine the duration, therapeutic objective, and metabolic effects.

Claim	Added limitation
2	Treatment continues for approximately 30 to 120 days
3	Timing is selected to produce a prolactin or prolactin-and-cortisol rhythm associated with an obese subject, with the stated objective of increasing body fat in a lean subject
4	Treatment increases cellular sensitivity to insulin’s glucose-disposal effects
5	Treatment reduces body fat, insulin resistance, hyperglycemia, hyperinsulinemia, or triglycerides
6	Treatment reduces hyperglycemia

Claim 3 is an unusual dependent claim because it recites an objective that could be relevant to weight gain in a lean subject, rather than metabolic improvement in an obese or diabetic subject. It remains dependent on claim 1 and therefore retains claim 1’s timing, dose, daily-administration, and therapeutic-treatment requirements.

Claims 4 through 6 focus on functional metabolic outcomes. They do not require a particular laboratory test in the claim language. In a live patent dispute, proof would likely center on whether the accused regimen was intended to produce, or in fact produced, the claimed physiological result.

How do claims 8 through 20 narrow the patient population?

Claims 8 through 15 identify patient populations and metabolic outcomes. Claims 16 through 20 narrow the dopamine agonist to bromocriptine.

Claims	Patient population or active ingredient
8, 12, 17	Insulin-resistant human subjects
9, 13, 18	Diabetic human subjects
10, 14, 19	Type II diabetic human subjects
11, 15, 20	Obese human subjects
16 through 20	Bromocriptine
12 through 15, 17 through 20	Specified metabolic reductions in the identified populations

The claims are cumulative. For example, claim 20 requires:

The base regimen of claim 1;
An obese human subject;
Bromocriptine as the dopamine agonist; and
Reduction of body fat, insulin resistance, hyperglycemia, hyperinsulinemia, or triglycerides.

A product sponsor practicing bromocriptine treatment could have fallen within several overlapping claims during the patent term if its labeled or actual regimen matched the morning timing and dose limitations.

How does the patent compare with the FDA-approved Cycloset regimen?

Cycloset is bromocriptine mesylate approved by the FDA in 2009 as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes. The FDA label directs administration within two hours of waking and titration from 0.8 mg to a maximum of 4.8 mg once daily. (U.S. Food and Drug Administration, 2009)

Parameter	U.S. 5,756,513	Cycloset labeling
Active ingredient	Dopamine agonist; bromocriptine expressly included	Bromocriptine mesylate
Administration frequency	Daily	Once daily
Timing	Shortly after awakening through five hours after awakening	Within two hours of waking
Dose	About 3 to 40 micrograms per pound	0.8 to 4.8 mg
Patient population	Broad metabolic populations, including obese and insulin-resistant subjects	Adults with type 2 diabetes
Therapeutic objective	Insulin sensitivity and metabolic improvement	Glycemic control
Patent 5,756,513 status	Expired	No current exclusivity from this patent

For a 70-kilogram adult, the patent’s stated dose range converts to approximately 0.46 to 6.17 mg. Cycloset’s labeled 0.8-to-4.8-mg range falls within that numerical range. Its morning administration instruction also falls within the patent’s timing window. During the patent term, those overlapping characteristics would have been commercially relevant.

What is the Orange Book status of U.S. Patent 5,756,513?

U.S. Patent 5,756,513 is not a current source of Orange Book exclusivity for Cycloset. The patent expired before Cycloset entered the market in 2009 or, at the latest, before current generic-entry analysis.

The Orange Book distinguishes patent listing from FDA regulatory exclusivity. A listed patent can delay approval of an ANDA through the Hatch-Waxman process, while a patent that has expired cannot provide a current approval stay or launch bar. (U.S. Food and Drug Administration, 2024)

For Cycloset, relevant regulatory questions concern later patents listed for the approved product, not the expired 1998 patent. A generic applicant would evaluate:

Any currently listed formulation or method-of-use patents;
Whether the proposed label includes or carves out the patented indication;
Paragraph III certification if a listed patent has not expired;
Paragraph IV certification if the applicant challenges validity, enforceability, or infringement; and
Any 30-month stay triggered by a timely patent-owner infringement action.

The expired patent cannot independently support a Paragraph IV dispute with present commercial effect.

Are there Paragraph IV challenges to this patent?

No current Paragraph IV challenge can create a meaningful launch delay based on U.S. Patent 5,756,513 because the patent is expired. Paragraph IV certification is designed for an unexpired listed patent. An applicant could identify an expired patent in its regulatory analysis, but the patent would not support a current 30-month stay.

The commercially important Paragraph IV risk for bromocriptine products would arise from later, unexpired patents covering:

A rapid-release bromocriptine formulation;
Specific salt, particle-size, dissolution, or excipient profiles;
A particular dosing schedule;
A method of improving glycemic control; or
A product-specific formulation used in the FDA-approved label.

The patent at issue contains no apparent claims directed to tablet dissolution, excipient selection, release rate, stability, packaging, or a bromocriptine manufacturing process.

What formulations are protected by U.S. 5,756,513?

None. The patent does not claim a formulation.

It does not require:

Bromocriptine mesylate rather than another salt;
A specific tablet;
Immediate release or controlled release;
A particular excipient;
A defined dissolution profile;
A particle-size distribution;
A specific bioavailability profile; or
A manufacturing route.

The patent could have covered use of a formulation if the administration regimen satisfied the method claims, but it did not create formulation exclusivity. That distinction is important for generic strategy. A later applicant could avoid a formulation patent while still practicing an expired method, or could use a formulation that differs from the branded product while remaining exposed to a live method-of-use claim.

Does the patent create biosimilar risk?

No. Bromocriptine is a small-molecule active ingredient, not a biologic. Biosimilar and interchangeable-biologic pathways under the Public Health Service Act do not apply. A competing bromocriptine product would generally proceed through an abbreviated new drug application or a full NDA pathway, depending on the product and reference-product circumstances.

The relevant competitive risks are generic substitution, formulation patents, labeling restrictions, and commercial supply capability. Biosimilar litigation is not relevant to this patent family.

What patent litigation and settlement issues affect the patent?

The expired patent does not present an active U.S. litigation barrier. Any historical dispute involving this patent would have no remaining exclusionary term unless a separate legal remedy or related patent right applied, which would need to be analyzed independently.

No current settlement agreement can restore the expired patent’s exclusivity. A settlement involving later Cycloset or bromocriptine patents could affect launch timing, but it would not extend U.S. Patent 5,756,513 beyond its statutory expiration.

How strong was the patent estate?

During its term, the patent had meaningful practical scope because it combined:

A broad dopamine-agonist genus;
An express bromocriptine species;
A clinically relevant morning dosing window;
A weight-based dose range overlapping Cycloset dosing; and
Metabolic endpoints relevant to type 2 diabetes and obesity.

Its weaknesses included the following:

It was a method patent rather than a composition or product patent.
The claim depended on a specific time-of-day regimen.
The dose was expressed per pound of body weight, while commercial labels commonly use fixed doses.
Several outcome limitations were functional and potentially difficult to prove.
The patent had no remaining term by the time current bromocriptine competition developed.
It did not block alternative formulations or manufacturing methods independently.

The patent was therefore commercially relevant as an early use patent but has no residual blocking strength in the United States.

What generic launch risks exist for bromocriptine products?

The expired patent removes one major barrier, but a generic sponsor still must assess the current product-specific landscape.

Risk category	Impact
Expired method patent	No current blocking effect
Later Orange Book patents	Could delay ANDA approval or require a label carve-out
Formulation differences	May avoid or trigger later formulation claims
Method-of-use labeling	Could create induced-infringement arguments if patented use remains on the label
FDA safety requirements	Bromocriptine has clinically important contraindications, warnings, and titration requirements
Supply and manufacturing	Commercial scale, API quality, and tablet consistency may affect launch
Market size	Type 2 diabetes is large, but bromocriptine has a differentiated and relatively limited commercial position
Substitution	Competition includes metformin, GLP-1 receptor agonists, DPP-4 inhibitors, SGLT2 inhibitors, and other glucose-lowering therapies

Cycloset’s regulatory indication is narrower than the full metabolic scope described in the patent. That difference can matter in a skinny-label strategy. A generic applicant may seek approval for non-patented uses while excluding a still-protected method of use, if the FDA-approved labeling and patent listing support that approach.

How does U.S. 5,756,513 compare with later bromocriptine IP?

IP category	U.S. 5,756,513	Later product patents
Primary focus	Chronotherapy and metabolic use	Product formulation, dosage form, or specific commercial use
Active ingredient	Broad dopamine agonist class with bromocriptine	Often bromocriptine-specific
Dose	Weight-based range	Often fixed-dose commercial regimen
Timing	Morning, up to five hours after awakening	May specify a narrower administration interval
Formulation coverage	None	May claim release, excipients, salt, or tablet properties
Manufacturing coverage	None	May claim process or impurity control
Current enforceability	None	Depends on each patent’s expiration and Orange Book status

The relevant freedom-to-operate question is therefore not whether a competing product practices the expired patent. It is whether the product practices any later, unexpired claims associated with the reference product or its formulation.

Key Takeaways

U.S. Patent 5,756,513 claims morning, daily administration of dopamine agonists to modify prolactin-related rhythms and improve metabolic control.
Bromocriptine is expressly covered, but only when used within the claimed regimen.
The central dose range is approximately 6.6 to 88 micrograms per kilogram.
The patent does not claim bromocriptine itself, a tablet formulation, a salt, an excipient system, or a manufacturing process.
The patent issued on May 26, 1998 and expired in 2015 under the applicable patent-term rules.
It cannot support a current Paragraph IV stay, injunction, or U.S. exclusivity period.
Cycloset’s FDA-approved regimen overlaps materially with the patent’s former timing and dose scope.
Bromocriptine is a small molecule, so biosimilar analysis does not apply.
Current generic-entry risk depends on later patents, current Orange Book listings, label strategy, formulation design, and manufacturing capability.

FAQs

Can a generic manufacturer launch bromocriptine without licensing U.S. Patent 5,756,513?

Yes. The patent is expired, so it does not require a license for current U.S. commercial activity.

Does U.S. 5,756,513 cover all bromocriptine uses?

No. It covers a specific daily, morning-timed regimen directed to hormonal-rhythm and metabolic outcomes. It does not claim bromocriptine for every indication or dosing schedule.

Does taking bromocriptine within five hours of waking still infringe the patent?

No current infringement liability arises from this expired patent. During its term, a matching regimen could have implicated the claims if the dose, daily administration, patient, and therapeutic-purpose limitations were satisfied.

Is the patent relevant to a bromocriptine ANDA today?

Only as expired prior patent history. It should not create a current approval stay. The ANDA applicant must still evaluate any later listed patents and applicable labeling restrictions.

Could a later patent revive the claims of U.S. 5,756,513?

No. A later patent may claim a related formulation, regimen, or indication, but it cannot revive or extend the expired claims of the 1998 patent.

References

U.S. Patent No. 5,756,513. (1998). Method of treating diabetes with dopamine agonists. United States Patent and Trademark Office.
U.S. Food and Drug Administration. (2009). Cycloset (bromocriptine mesylate) tablets prescribing information. FDA.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. FDA.
United States Code, 35 U.S.C. § 154. (2024). Contents and term of patent; provisional rights.
United States Code, 21 U.S.C. § 355. (2024). New drugs and abbreviated applications.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	174793	⤷ Start Trial
Austria	227566	⤷ Start Trial
Austria	249216	⤷ Start Trial
Austria	290863	⤷ Start Trial
Austria	391506	⤷ Start Trial
Austria	440606	⤷ Start Trial
Australia	1447595	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,756,513

Summary for Patent: 5,756,513