United States Drug Patent RE37564: Claim Scope, Expiration, Orange Book Status, and Generic Risk

U.S. Patent RE37,564 covers an oral contraceptive package and dosing regimen rather than drospirenone itself. Its central limitation is a 23- or 24-day course of estrogen-progestin tablets followed by five or four hormone-free days, respectively. Claims 13-15 most directly target the commercial 20 microgram ethinylestradiol/3 mg drospirenone 24/4 regimen associated with Yaz and its authorized generic equivalents.

RE37,564 is an expired reissue patent. It does not provide a current blocking right against generic drospirenone/ethinylestradiol products. Its historical importance was greater than its present enforcement value because it addressed the tablet-count and hormone-free interval used in a leading branded contraceptive product.

What does U.S. Patent RE37564 cover?

RE37,564 covers a packaged combination preparation for oral contraception with two components:

Active combination tablets containing estrogen and a progestin.
Placebo tablets, or labeling and packaging instructions, directing a defined hormone-free interval.

The core regimen is:

Active tablets	Placebo or pill-free days	Regimen covered
23	5	28-day cycle
24	4	28-day cycle

The claims cover both physical dosage units and non-tablet indicia. “Other indications” can include packaging, blister-card markings, calendars, or instructions showing that the active tablets are followed by the specified placebo or pill-free interval.

The patent is therefore directed to a combination of:

Active pharmaceutical ingredients;
Dosage strength;
Number of active dosage units;
Number of inactive units or hormone-free days;
Uniformity of drospirenone content in the narrower claims.

The claims do not broadly cover every drospirenone contraceptive. A product must satisfy the relevant active-ingredient, dose, tablet-count, and interval limitations.

What are the main independent claims in RE37564?

Claims 1 and 13 are the principal claim categories.

Claim 1: broad combination-product claim

Claim 1 covers a 23- or 24-unit contraceptive product in which each active unit contains an estrogen and a gestagen, followed by five or four placebo units or corresponding pill-free days.

The supplied claim text contains apparent transcription or formatting defects in the dose ranges. The commercially and technically relevant portions appear to identify:

Ethinylestradiol at 0.020 mg, or 20 micrograms;
17β-estradiol within a milligram range;
Drospirenone at approximately 2.5 to 3.0 mg;
Cyproterone acetate within a separate progestin dose range.

The claim is broad in product architecture but narrow in cycle design. It does not cover a conventional 21 active-tablet/7-day hormone-free regimen unless another claim or patent independently applies.

Claim 13: drospirenone-specific claim

Claim 13 is narrower and more commercially significant. It requires:

23 or 24 daily active dosage units;
20 micrograms of ethinylestradiol in each active unit;
2.5 to 3.0 mg of drospirenone in each active unit;
Five or four placebo or pill-free days;
The same amount of drospirenone in every drospirenone-containing unit.

Claims 14 and 15 narrow claim 13 to the 23/5 and 24/4 formats.

Claim 15 is the closest textual match to a 24/4 product containing 20 micrograms of ethinylestradiol and 3 mg of drospirenone.

How do claims 2 through 12 narrow the patent scope?

Claim	Subject matter	Commercial relevance
1	23/24 active units, estrogen plus gestagen, followed by 5/4 placebo or pill-free days	Broad regimen architecture
2	Claim 1 with ethinylestradiol	Captures the principal synthetic-estrogen version
3	Claim 2 with cyproterone acetate	Relevant to CPA/EE contraceptive combinations
4	Claim 2 with drospirenone	Directly relevant to DRSP/EE products
5	20 micrograms ethinylestradiol or equivalent estradiol and progestin equivalent to 75 micrograms gestodene	Dose-equivalence limitation
6	23 active units and 5 placebo units	23/5 regimen
7	23 units containing 20 micrograms ethinylestradiol plus CPA or drospirenone equivalent to 75 micrograms gestodene, followed by 5 placebo units	Narrow 23/5 formulation
8	17β-estradiol	Natural-estrogen alternative
9	17β-estradiol plus cyproterone acetate	Narrow natural-estrogen/CPA combination
10	17β-estradiol plus drospirenone	Narrow natural-estrogen/DRSP combination
11	Drospirenone combination with 23 active and 5 placebo units	23/5 DRSP regimen
12	Drospirenone combination with 24 active and 4 placebo units	24/4 DRSP regimen
13	20 micrograms ethinylestradiol plus 2.5-3.0 mg drospirenone, uniform DRSP dose, 23/5 or 24/4	Main DRSP-specific independent claim
14	Claim 13 limited to 23/5	Narrower regimen
15	Claim 13 limited to 24/4	Closest Yaz-type claim

Claims 4, 12, 13, and 15 form the most relevant cluster for drospirenone/ethinylestradiol products. Claim 15 is the most specific claim directed to the 24 active tablets plus four placebo tablets configuration.

Does RE37564 cover Yaz, Yasmin, and generic drospirenone/ethinylestradiol?

Yaz and 24/4 products

A product containing 3 mg drospirenone and 20 micrograms ethinylestradiol in 24 active tablets followed by four placebo tablets falls within the literal structure of claims 12, 13, and 15, assuming the dosage units and packaging satisfy the remaining claim limitations.

This is the patent’s principal commercial target.

Yasmin and 21/7 products

Yasmin traditionally used 21 active tablets followed by seven hormone-free days. That format does not satisfy the express 23/24 active-unit and 5/4-day limitations in RE37,564. A 21/7 product may have been protected by other composition, formulation, method-of-use, or manufacturing patents, but RE37,564 is not the principal patent for that regimen.

Generic Yaz equivalents

Generic products with the same 24/4 architecture could have been exposed to RE37,564 during its enforceable term. After patent expiration, the claim no longer creates a patent-based generic-entry barrier. Product-specific FDA approval, labeling, bioequivalence, and any unexpired patents must be analyzed separately.

When did RE37564 lose exclusivity?

RE37,564 is expired. The reissue did not create a new patent term independent of the original patent. Under U.S. law, a reissue patent generally carries the remaining term of the original patent and cannot extend the original patent’s statutory duration merely because the reissue issued later (35 U.S.C. §§ 251, 252).

The patent was issued as a reissue on July 9, 2002. Its term was tied to the original patent, U.S. Patent No. 5,280,023, rather than running for a new 20-year period from the reissue date. Public patent records identify the original pre-Uruguay Round term as the controlling framework. The enforceable term therefore ended years before the current generic market for drospirenone/ethinylestradiol products developed.

Event	Date or status
Original patent	U.S. Patent No. 5,280,023
Reissue patent	RE37,564
Reissue issue date	July 9, 2002
Current status	Expired
New term from reissue?	No
Current blocking value	None as an enforceable patent right

The precise historical expiration date should be taken from the USPTO Patent Center record for the original patent, including any applicable term adjustment or terminal disclaimer data. The critical commercial conclusion is unchanged: RE37,564 is no longer an enforceable exclusivity barrier.

What was the Orange Book status of RE37564?

RE37,564 was associated historically with the drospirenone/ethinylestradiol contraceptive franchise. Orange Book relevance depended on whether Bayer or an affiliated NDA holder listed the patent against the applicable drug product and whether the listing remained active at the time of an ANDA filing.

The Orange Book distinguishes between:

Drug substance patents;
Drug product or formulation patents;
Method-of-use patents;
Patents that are no longer active because they expired or were delisted.

RE37,564 is a regimen and combination-product patent. It is not a simple drospirenone compound patent. Its relevance to an ANDA would have depended on the scope of the listed claims and the generic applicant’s proposed 23/5 or 24/4 labeling.

An expired Orange Book patent can remain historically visible in regulatory records, but it cannot support a current 30-month stay or a present infringement action. FDA approval of a generic product may still require appropriate certification to other listed patents, including formulation and method-of-use patents that had different expiration dates (FDA, 2024).

Which patents were more important for the drospirenone/ethinylestradiol franchise?

RE37,564 was one layer in a larger patent estate. Commercial protection for products such as Yasmin and Yaz typically involved several patent categories.

Drospirenone compound and synthesis patents

These patents protect:

The steroidal active ingredient;
Specific intermediates;
Stereochemical forms;
Manufacturing routes;
Purification and crystallization processes.

A compound or process patent may have expired on a different date from RE37,564. Process patents are relevant when a generic manufacturer uses a protected route or cannot obtain the active ingredient from an independent supplier.

Micronization and dissolution patents

Drospirenone has low aqueous solubility. Patents directed to particle size, micronization, dissolution, suspension, and tablet manufacture were commercially important. Bayer-related litigation involving U.S. Patent No. 6,787,531 addressed drospirenone formulation and dissolution characteristics. The Federal Circuit’s decision in Bayer Schering Pharma AG v. Barr Laboratories, Inc. addressed the validity and infringement issues surrounding that patent estate (Bayer Schering Pharma AG v. Barr Laboratories, Inc., 2009).

These patents could create a separate barrier even after a regimen patent expired.

Formulation patents

Formulation claims may cover:

Drospirenone particle size;
Defined dissolution profiles;
Excipients;
Granulation;
Tablet hardness;
Coating;
Stability;
Uniform active-ingredient distribution.

A generic applicant can sometimes avoid a formulation claim by using a different manufacturing process or dissolution profile. That strategy does not avoid a regimen claim if the product still uses the claimed 24/4 package.

Method-of-use patents

Separate patents may cover treatment of:

Contraception;
Premenstrual dysphoric disorder;
Moderate acne;
Premenstrual symptoms;
Hormonal symptoms associated with the menstrual cycle.

Method-of-use patents are often handled through a section viii “skinny label” where the generic removes patented indications, provided the remaining label does not encourage infringement. A regimen or product claim such as RE37,564 is harder to avoid through label carving if the ANDA product itself is packaged and labeled with the claimed schedule.

What Paragraph IV challenges affected RE37564 and related patents?

Generic companies challenging branded drospirenone/ethinylestradiol products typically used ANDA Paragraph IV certifications against listed patents. The principal legal issues were:

Whether the generic product satisfied the claimed drospirenone and ethinylestradiol strengths;
Whether the proposed product used the patented dissolution or micronization characteristics;
Whether the 24/4 regimen was claimed;
Whether the patent claims were valid over prior art;
Whether the generic applicant’s labeling induced infringement.

Bayer and Barr litigated the Yaz-related patent estate in federal court. The Federal Circuit addressed the formulation patent in 2009, and later generic-entry disputes involved other Bayer patents and settlements (Bayer Schering Pharma AG v. Barr Laboratories, Inc., 2009).

A Paragraph IV challenge against an expired patent has no current litigation-stay effect. Historical ANDA litigation can still matter for launch chronology and settlement analysis, but it does not revive the patent.

How strong were the claims of RE37564?

Strengths

The claims had several practical strengths during their term:

They captured the 24/4 architecture used in a major commercial product.
Claims 13-15 specified the commercially recognizable 20 microgram/3 mg formulation.
The claims covered both placebo tablets and instructions showing pill-free days.
Uniform drospirenone content in claim 13 reduced the ability to vary active-tablet strengths within the cycle.
The claims could reach the product package, not only a physician’s method of prescribing.

Weaknesses

The claims also had vulnerabilities:

The regimen concept was relatively easy to identify and describe, creating prior-art and obviousness issues.
The claim language supplied contains apparent transcription defects in the estrogen and gestagen ranges.
“Equivalent dose” language in claim 5 can create claim-construction disputes.
A manufacturer could attempt a different active-tablet count or hormone-free schedule.
A product with a different formulation may avoid separate composition or dissolution claims while still requiring analysis under the regimen claims.
The patent’s term has ended.

The commercial strength of RE37,564 was therefore highest against a branded or generic 24/4 product during the active term. Its present patent strength is zero because the patent is expired.

What generic launch scenarios existed?

During the enforceable period, generic manufacturers had several possible strategies.

Launch strategy	RE37,564 exposure
24 active tablets plus 4 placebo tablets, 20 micrograms EE/3 mg DRSP	High literal-claim exposure during patent term
23 active tablets plus 5 placebo tablets	Exposure under claims 13-14 and related claims
21 active tablets plus 7 placebo tablets	Generally outside RE37,564’s express tablet-count limitations
Different drospirenone strength	Potential avoidance of narrow dose claims, subject to broader claims
Different estrogen	May avoid EE-specific claims, subject to claim 1 and other patents
Same product with altered label	Limited value if the package itself satisfies product claims
Product without placebo tablets but with 4-day instructions	Potentially still covered because claims include “other indications”
Alternative formulation or dissolution profile	May avoid separate formulation patents, not necessarily regimen claims

Because RE37,564 has expired, these scenarios are now primarily relevant to historical litigation and patent-landscape reconstruction.

Which companies challenged the drospirenone franchise?

The main generic challengers in the U.S. drospirenone/ethinylestradiol market included Barr Laboratories and other ANDA applicants seeking approval of generic versions of Bayer’s products. Litigation focused more heavily on the broader patent estate than on RE37,564 alone.

Relevant parties included:

Bayer Schering Pharma AG and affiliated NDA holders;
Barr Laboratories;
Watson Pharmaceuticals and affiliated entities;
Other generic applicants pursuing drospirenone/ethinylestradiol approvals.

The commercial disputes involved Paragraph IV certifications, district-court litigation, Federal Circuit appeals, and settlement arrangements. Settlement terms can affect launch timing, authorized-generic rights, supply arrangements, and licensing, but RE37,564’s expiration means any current settlement analysis must focus on other patents, regulatory exclusivity, or contractual rights.

What licensing and settlement issues matter today?

RE37,564 itself has no remaining patent-license value as an exclusionary right. Historical agreements may still matter for:

Authorized generic launch rights;
Supply of drospirenone;
Early-entry dates;
Manufacturing arrangements;
Royalty obligations tied to other patents;
Release of litigation claims;
Geographic rights outside the United States.

A settlement involving RE37,564 may have used the patent as one element of a broader package. The operative commercial restrictions, if any, would depend on surviving contract provisions and other unexpired intellectual-property rights. The expired patent alone cannot prevent a U.S. generic launch.

How does RE37564 compare with other drospirenone patent barriers?

Patent category	Target	Typical generic design-around
Regimen patent	23/5 or 24/4 schedule	Use a different cycle structure
Drug-product patent	Tablet composition and manufacturing	Change excipients or process
Dissolution patent	Particle size and release profile	Use a different particle-size or release approach
Drug-substance patent	Drospirenone molecule or salt/form	Wait for expiry or use noninfringing source
Process patent	Synthesis or purification route	Use an alternative manufacturing route
Method-of-use patent	Contraception, PMDD, acne	Remove patented indication where permitted
Regulatory exclusivity	FDA approval protection	Wait for exclusivity expiration

RE37,564 was a regimen patent with product characteristics. It should not be treated as equivalent to a compound patent or a formulation patent. A complete freedom-to-operate analysis for a current product requires review of the full Orange Book and non-Orange Book estate, including process patents and foreign rights.

What is the geographic coverage of RE37564?

RE37,564 covers the United States only. Parallel patents or patent applications in Europe, Canada, Japan, and other jurisdictions required separate validity, term, and claim-scope analysis.

Foreign equivalents could differ in:

Active-tablet count;
Estrogen and progestin dose;
Placebo interval;
Claim format;
Patent term;
Supplementary protection certificate status;
Litigation outcome;
National validation and maintenance.

U.S. expiration does not establish worldwide freedom to operate. It establishes that RE37,564 no longer blocks U.S. manufacture, sale, importation, or FDA approval on its own.

Key Takeaways

RE37,564 is a regimen and combination-product patent, not a drospirenone compound patent.
The most important claims are 13-15, particularly claim 15 covering 20 micrograms ethinylestradiol, approximately 3 mg drospirenone, 24 active tablets, and four placebo or pill-free days.
The patent distinguishes 23/5 and 24/4 schedules from the conventional 21/7 regimen.
Claim 15 is the closest match to a Yaz-type 24/4 product.
The patent’s reissue did not create a new patent term.
RE37,564 is expired and has no current U.S. blocking effect.
Historical Paragraph IV litigation involving Bayer, Barr, Watson, and other generic applicants centered on the broader drospirenone patent estate, including formulation and dissolution patents.
Current generic-entry risk depends on surviving formulation, process, method-of-use, regulatory, and contractual restrictions, not RE37,564 itself.
Any claim analysis must account for apparent transcription defects in the supplied claim text, especially the dose ranges and the reference to “gestadene,” which appears to refer to gestodene.

FAQs About U.S. Patent RE37564

Does RE37564 cover a 21-day drospirenone contraceptive?

Generally no. The asserted claims require 23 or 24 active dosage units followed by five or four placebo or pill-free days. A 21/7 product falls outside those express tablet-count and interval limitations.

Does RE37564 cover generic Yaz?

It historically could have covered a generic using the same 24/4 package, 20 micrograms ethinylestradiol, and approximately 3 mg drospirenone. Because the patent is expired, it no longer blocks generic Yaz-equivalent products.

Is RE37564 a formulation patent?

It is best characterized as a combination-product and regimen patent. It includes active ingredients and dose limitations, but its defining feature is the 23/5 or 24/4 administration schedule.

Can a generic avoid RE37564 by omitting placebo tablets?

Not necessarily. The claims expressly include “other indications” showing that the active dosage units are followed by the specified pill-free interval. Removing placebo tablets would not automatically avoid the claims if the product labeling or packaging supplies the required schedule.

Are drospirenone process patents still relevant after RE37564 expired?

Yes. A manufacturer must separately assess active-ingredient synthesis, particle-size, dissolution, tablet-manufacturing, and method-of-use patents. Expiration of a regimen patent does not establish complete freedom to operate.

References

Bayer Schering Pharma AG v. Barr Laboratories, Inc., 575 F.3d 1341 (Fed. Cir. 2009).
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. FDA.
United States Patent and Trademark Office. (2002). U.S. Patent RE37,564: Pharmaceutical composition for contraception. USPTO Patent Center.
United States Patent and Trademark Office. (1994). U.S. Patent No. 5,280,023: Pharmaceutical composition for contraception. USPTO Patent Center.
35 U.S.C. §§ 251-252.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
Germany	43 44 462	Dec 22, 1993

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	344038	⤷ Start Trial
Canada	2179728	⤷ Start Trial
China	100377713	⤷ Start Trial
China	1142185	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: RE37564

Summary for Patent: RE37564