Progesterone Agonist/Antagonist Drug Class List

Drugs in Drug Class: Progesterone Agonist/Antagonist

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Lab Hra Pharma	ELLA	ulipristal acetate	TABLET;ORAL	022474-001	Aug 13, 2010	AB	RX	Yes	Yes	8,735,380		Y
Lab Hra Pharma	ELLA	ulipristal acetate	TABLET;ORAL	022474-001	Aug 13, 2010	AB	RX	Yes	Yes	9,844,510		Y
Lab Hra Pharma	ELLA	ulipristal acetate	TABLET;ORAL	022474-001	Aug 13, 2010	AB	RX	Yes	Yes	8,512,745		Y
Lab Hra Pharma	ELLA	ulipristal acetate	TABLET;ORAL	022474-001	Aug 13, 2010	AB	RX	Yes	Yes	8,426,392

Progesterone Agonist/Antagonist Market Dynamics & Patent Landscape (2026): Key Patents, Exclusivity Timelines, Generic/Biosimilar Risk

Last updated: July 19, 2026

The progesterone agonist/antagonist class spans multiple hormonal targets with distinct IP and regulatory paths: FDA-listed small molecules (including oral, vaginal, and injectable formulations) with Orange Book-based exclusivity and patent term windows, plus limited but meaningful off-label and method-of-use patent risk. Patent cliffs are driven less by broad core chemical patents and more by formulation, device/combination patents (especially with estrogen or other agents), and method-of-use claims tied to endometrium protection, bleeding disorders, and reproductive indications.

The most defensible near-term IP positions typically cluster around:

• Brand protection via formulation and route-of-administration (micronized suspensions, solubilizers, depot technology, and vaginal inserts/films).
• Device and combination IP (progestin + delivery platform).
• Method-of-use (specific dosing regimens and patient subpopulations).
• Exclusivity sequencing (NCE/505(b)(2) exclusivities and pediatric exclusivity) that delays generic entry even when some composition patents have expired.

Which progesterone agonist/antagonist drugs have the strongest patent estates in the US?

The “progesterone agonist/antagonist” label in practice covers multiple progestins and one major progesterone receptor antagonist used clinically in women’s health and obstetrics. The patent estate strength varies by molecule and by route.

High-leverage branded progestin/IP baskets (typical US posture)

Common structural patterns in the class (as seen across progestin brands on the Orange Book and in Hatch-Waxman litigation) include:

• Composition-of-matter core patents that expire earlier than the market exclusivity.
• Formulation/process patents that persist into the generic window.
• Use patents that survive earlier chemical expiry by focusing on approved indication dosing and regimen steps.

What tends to drive enforceability

For progestin brands, enforceability most often comes from:

• Narrowly drafted formulation parameters (particle size/distribution, solubilizer ratios, release kinetics, depot characteristics).
• Manufacturing method claims that are harder for generics to design around without process risk.
• Specific regimen claims (timing, dose titration, cycle day windows).

How does progesterone antagonist patent coverage differ from progesterone agonists?

Progesterone antagonists and partial antagonists are fewer in number but tend to have:

• Higher linkage to single active ingredient plus indication-specific method-of-use.
• Smaller formulation diversity, which shifts the patent burden to regimen and combination coverage.

Example: mifepristone (progesterone receptor antagonist)

Mifepristone is the class anchor for progesterone receptor antagonism. The US regulatory and IP posture for mifepristone brands is usually dominated by:

• Orange Book listed patents (composition and use).
• Method-of-use and regimen patents related to endometrial effects and clinical workflow.

Market dynamic: entry risk depends heavily on whether challengers can avoid both composition claims (if still alive) and method-of-use claims (often more resilient than generic challengers expect).

What patents protect progesterone receptor modulators and progestins (composition, formulation, method-of-use)?

A progesterone agonist/antagonist IP map in the US usually breaks into five buckets:

1) Composition-of-matter patents

• New progestin molecules (when applicable).
• Salts/solvates and stereochemical sets (for older progestins).
• In some cases, improvements such as alternative crystalline forms.

2) Formulation patents

• Solubilizer systems and excipient compositions for oral absorption.
• Particle size and distribution for suspensions.
• Depot release technologies for injectable progestins.
• Vaginal products: matrix properties, release rate, mucoadhesion.

3) Manufacturing/process patents

• Sterile fill/process controls.
• Micronization and milling processes.
• Steric stabilization and handling steps.

4) Method-of-use and regimen patents

• Specific dose schedules.
• Cycle-based administration windows.
• Patient subgroups (e.g., post-ovulation bleeding or endometrial protection regimens).

5) Device and combination patents

• Auto-injector or delivery device pairing.
• Progestin used with estrogen or other hormonal agents in a defined regimen.

When do progesterone agonist/antagonist drugs lose exclusivity in the US (Orange Book timelines)?

US exclusivity usually follows a sequencing framework:

• 5-year New Chemical Entity (NCE) or 3-year new clinical investigation exclusivity for certain 505(b)(2) or line extensions.
• Pediatric exclusivity (6 months) added on top if pediatric requirements are met.
• Patent term measured to the latest expiration among Orange Book-listed patents for the listed drug and strength/dosage form.

Featured snippet answer pattern

For progestins, generic eligibility is typically constrained until the last of:

• the latest expiring Orange Book patent, or
• the last expiring exclusivity tied to the NDA/BLA reference product.

Practical market effect: even if chemical patents expire earlier, formulation and use patents can hold the line for multiple years.

Which paragraph IV challenges target progesterone agonist/antagonist patents?

Paragraph IV challenges create the most visible entry risk, but coverage is uneven across the class. The typical pattern is:

• Generic applicants file Paragraph IV notices to one or more Orange Book listed patents covering formulation or method-of-use, not necessarily the earliest composition patent.
• Litigation often focuses on whether a proposed generic formulation infringes formulation parameters or whether method-of-use claims are effectively avoided via labeling carve-outs.

Business implication: the “generic entry date” is not just the earliest patent expiry. It is the date that emerges from:

• litigation outcome,
• settlement agreement terms (typical “carve-out” labeling and/or delayed launch),
• and any remaining exclusivity.

How strong is the patent estate for branded progestins versus generics (infringement risk)?

Patent strength in this class correlates with three technical variables:

Claim dependency and design-around surface area

• Formulation and manufacturing patents reduce generic design-around space.
• Method-of-use patents can be designed around via label changes, but only if claim scope is tightly tied to the prohibited regimen.

Drug product complexity

• Injectable and vaginal products with controlled release mechanisms usually sustain stronger enforceability.
• Simple immediate-release oral formulations are more vulnerable to generic equivalence arguments.

Claim breadth and claim numbers

• Estates with many continuation filings and multiple formulation and process patents generally increase the number of infringement touchpoints and prolong litigation.

What formulations are protected for progesterone agonists (oral vs vaginal vs injectable)?

Formulation patents are where the class typically “lives” near the end of the brand lifecycle.

Oral

Common patented angles:

• Solubilization systems and absorption-enhancing excipients.
• Particle engineering (in suspensions).
• Specific dose administration patterns when absorption varies across patient populations.

Vaginal

Common patented angles:

• Controlled release matrices.
• Mucoadhesive polymers and release kinetics.
• Device-integrated delivery for inserts and similar dosage forms.

Injectable

Common patented angles:

• Depot particle characteristics.
• Sterile suspension handling and depot formation steps.
• Release profile design tied to depot particle engineering.

What patent litigation affects generic entry for progesterone agonist/antagonist drugs?

Litigation outcomes typically influence one of three business levers:

1. Launch timing (preliminary injunctions, final trial outcomes, or settlement-driven delays).
2. Labeling carve-outs (specific indication or regimen restrictions).
3. Design changes to avoid formulation/method-of-use infringement.

Common litigation themes

• Whether the generic product matches the brand’s patented formulation parameters.
• Whether the proposed generic label avoids the patented method-of-use.
• Whether patent invalidity arguments succeed for process/formulation claims with narrow parameter recitations.

Which companies are challenging progesterone agonist/antagonist patents (Paragraph IV filers) and what are their launch strategies?

The challenger landscape in the class typically includes:

• Large generics with established women’s health footprints.
• Niche filers focused on formulation engineering (particularly for vaginal and depot products).
• 505(b)(2) route entrants seeking to differentiate with alternative excipients or delivery approaches.

Market dynamic: challengers optimize for either “design-around by formulation” or “label carve-out for method-of-use.” Their strategy determines whether litigation is mostly technical (formulation/process infringement) or regulatory (labeling, ANDA carve-outs).

How does FDA regulatory status and exclusivity affect progesterone antagonist/generic entry?

FDA status gates market entry:

• ANDA approval is tied to bioequivalence and to the ability to avoid patent infringement for the active Orange Book patents.
• 505(b)(2) approvals can shift exclusivity and reference product linkage.
• Safety and REMS requirements (where present) can affect manufacturing and market access even after patent expiry.

Practical regulatory constraints

• For complex dosage forms, bioequivalence demonstrations can be harder, raising development cost and timeline risk.
• For indication-specific labeling, method-of-use carve-outs can limit real-world uptake even when the generic is approved.

What is the Orange Book status of major progesterone agonist/antagonist brands (how to interpret listings)?

Orange Book listings should be interpreted by:

• Patent type (composition vs formulation vs method-of-use).
• Listed drug granularity (different strengths and dosage forms can have separate listed patents).
• Expiration sequencing across the estate.

Decision rule for generic entry

A generic is blocked until the later date among:

• the last-to-expire Orange Book patent(s) relevant to the strength/dosage form, and
• any applicable exclusivity.

How do progesterone agonist/antagonist brands compare on patent risk for revenue exposure?

Revenue exposure tends to track:

• proportion of branded units in indications with entrenched prescribing (e.g., bleeding disorders, fertility support regimens, endometrial protection).
• durability of depot/vaginal demand.
• share of revenue tied to formulations that have fewer generic substitutes.

Risk concentration pattern

• Products with fewer competitors but more formulation patents have higher “post-first generic entry” erosion risk if challengers succeed.
• Products with multiple strengths/dosage forms often see staged erosion, as generics may launch only certain strengths early.

Which generic entry risks exist for progesterone receptor antagonist drugs (labeling and regimen constraints)?

For progesterone antagonists, generic entry risks are commonly driven by:

• method-of-use claims that align with approved clinical regimens.
• regulatory constraints on labeling, including mandated wording or contraindications.

Business implication: even if a generic is approved, uptake can be limited if the label design avoids patented regimens.

What licensing deals or settlement agreements usually shape the progestin generic market?

Settlement agreements in women’s health tend to include:

• delayed commercial marketing dates.
• “authorized use” carve-outs: label language changes and indication limits.
• sometimes supply/technology provisions tied to formula or manufacturing constraints.

Market effect: settlements can create a de facto exclusivity window longer than the raw patent expiration date, shifting revenue cliffs.

Key takeaways

• Progesterone agonist/antagonist IP is dominated by formulation, manufacturing, and method-of-use protections, not just early composition-of-matter patents.
• Orange Book sequencing and exclusivity stacking determine effective market cliffs.
• Paragraph IV challenges most often target the patents that maximize infringement leverage: formulation parameters and regimen-based method claims.
• Patent estate strength correlates with dosage form complexity (vaginal and depot) and claim density.
• For progesterone antagonists, label/regimen constraints are central to both litigation and commercial adoption.

FAQs

1. Do progestin formulation patents block FDA approval even if the generic is bioequivalent?
2. How do method-of-use patents for progestins interact with labeling carve-outs in ANDAs?
3. What drives the longest delay to generic entry for depot injectable progesterones: formulation patents or exclusivity?
4. Can 505(b)(2) products avoid progestin patent barriers by changing route or excipients?
5. How do settlements typically affect launch dates for progesterone agonists compared with pure patent expiration?

References

1. FDA. Approved Drug Products with Therapeutic Equivalence Evaluations (Orange Book). U.S. Food and Drug Administration. (Accessed 2026-07-20).
2. FDA. Hatch-Waxman Amendments: ANDA, Paragraph IV certification, and exclusivity overview. U.S. Food and Drug Administration. (Accessed 2026-07-20).
3. U.S. Patent and Trademark Office. Patent term, PTA/PTE concepts and general patent duration framework. (Accessed 2026-07-20).