List of Excipients in Branded Drug ELIGARD

Company	Tradename	Ingredient	NDC	Excipient	Potential Generic Entry
TOLMAR Inc	ELIGARD	leuprolide acetate	62935-461	METHYL PYRROLIDONE
TOLMAR Inc	ELIGARD	leuprolide acetate	62935-461	POLY(DL-LACTIC-CO-GLYCOLIC ACID)
TOLMAR Inc	ELIGARD	leuprolide acetate	62935-756	METHYL PYRROLIDONE
TOLMAR Inc	ELIGARD	leuprolide acetate	62935-756	POLY(DL-LACTIC-CO-GLYCOLIC ACID)

ELIGARD Excipient Strategy, ATRIGEL Delivery System, Patent Exposure, and Commercial Opportunities

Last updated: August 22, 2026

ELIGARD is a long-acting leuprolide acetate depot for advanced prostate cancer. Its commercial differentiation comes from the ATRIGEL Delivery System, which combines a biodegradable poly(DL-lactide-co-glycolide) polymer with N-methyl-2-pyrrolidone (NMP) to form an in situ depot after subcutaneous injection. The formulation supports four dosing intervals: one, three, four, and six months.

The principal commercial opportunity is not a simple leuprolide copy. It is the development of a differentiated depot platform with lower injection burden, improved handling, predictable drug release, and a regulatory pathway that can address both drug and device-like formulation complexity. The principal barrier is formulation equivalence. A generic or follow-on product must replicate clinically relevant release performance, local tolerability, syringe compatibility, reconstitution behavior, and manufacturing controls.

What is ELIGARD and how does its excipient strategy work?

ELIGARD contains leuprolide acetate, a gonadotropin-releasing hormone agonist, in a polymer-based depot system. The product is supplied as separate components that are mixed immediately before administration.

The approved presentation contains:

ELIGARD strength	Nominal dosing interval	Leuprolide acetate dose	Administration
7.5 mg	1 month	7.5 mg	Subcutaneous
22.5 mg	3 months	22.5 mg	Subcutaneous
30 mg	4 months	30 mg	Subcutaneous
45 mg	6 months	45 mg	Subcutaneous

The ATRIGEL system uses two principal excipient functions:

1. A biodegradable PLGA polymer creates the solidifying depot and controls release.
2. NMP acts as the water-miscible solvent that keeps the polymer in an injectable liquid before administration.

After injection, water enters the formulation, NMP diffuses away, and the polymer precipitates or solidifies. Leuprolide is released as the PLGA matrix hydrates and degrades. The formulation therefore combines solvent exchange, depot formation, polymer erosion, diffusion, and drug dissolution.

The approved label identifies the ATRIGEL Delivery System as a biodegradable polymer dissolved in NMP. The label does not disclose every formulation parameter needed to reproduce the product, including the precise polymer molecular-weight distribution, lactide-to-glycolide ratio, end-group chemistry, residual-solvent profile, and manufacturing controls (FDA, 2024).

What excipients are used in the ELIGARD formulation?

The core excipient system is PLGA and NMP. The commercial strategy depends less on the identity of those excipients than on their controlled physical and chemical attributes.

Poly(DL-lactide-co-glycolide)

PLGA is the release-controlling excipient. Its relevant attributes include:

• Lactide-to-glycolide ratio
• Polymer molecular weight and polydispersity
• Acid- or ester-terminated end groups
• Glass-transition temperature
• Residual monomer and solvent levels
• Water content
• Particle or polymer morphology
• Sterility and bioburden controls
• Degradation-product profile

Higher glycolide content generally increases hydrophilicity and can accelerate water uptake and degradation. Higher molecular weight usually supports slower degradation, although the release profile also depends on polymer concentration, drug loading, depot geometry, drug solubility, and injection-site conditions.

For a long-acting leuprolide product, minor changes in PLGA can shift the initial burst, mid-cycle release, terminal release, and local inflammatory response. Excipient substitution is therefore unlikely to be commercially neutral even when the polymer is nominally the same.

N-methyl-2-pyrrolidone

NMP is the solvent component of ATRIGEL. It supports syringeability and polymer processing before injection, then diffuses into surrounding tissue after administration.

The principal NMP control points are:

• Assay and impurity profile
• Water content
• Residual peroxide and reactive impurities
• Viscosity
• Compatibility with the syringe, needle, stopper, and container
• Local tolerability after subcutaneous administration
• Exposure from the full injected volume

NMP is commercially available and is used in pharmaceutical and medical-device applications. Its value in the product is functional rather than proprietary. The competitive barrier arises from the interaction between NMP, PLGA, leuprolide acetate, the packaging system, and the injection process.

How does ELIGARD compare with other leuprolide depot products?

ELIGARD competes primarily with other long-acting GnRH agonists and with GnRH antagonists such as degarelix and relugolix. The excipient and delivery strategy differs across products.

Product	Active ingredient	Delivery approach	Typical dosing interval	Key commercial distinction
ELIGARD	Leuprolide acetate	PLGA/NMP in situ subcutaneous depot	1 to 6 months	Multiple dosing intervals and ATRIGEL platform
Lupron Depot	Leuprolide acetate	Microsphere-based depot	1 to 6 months, depending on presentation	Established leuprolide brand with microsphere technology
Fensolvi	Leuprolide acetate	Long-acting subcutaneous depot	6 months	Pediatric central precocious puberty indication
Vantas	Histrelin acetate	Subcutaneous implant	12 months	Implant-based delivery
Firmagon	Degarelix	Injectable peptide formulation	Monthly or maintenance schedule	GnRH antagonist with rapid testosterone suppression
Orgovyx	Relugolix	Oral tablet	Daily	Oral GnRH antagonist

ELIGARD’s strongest product-level differentiator is interval flexibility. Its main weakness is the need for mixing before injection and the potential for handling variability. GnRH antagonists avoid the testosterone flare associated with GnRH agonists, which creates a clinical and commercial pressure that excipient optimization alone cannot solve.

What formulation patents protect ELIGARD?

ELIGARD’s historical patent position centered on the ATRIGEL depot system, the polymer-solvent composition, drug incorporation, depot formation, and controlled release. The relevant intellectual-property categories include:

• PLGA-based in situ forming depots
• NMP-containing injectable polymer systems
• Leuprolide depot formulations
• Multi-month release profiles
• Dual-component kits and mixing systems
• Syringe and administration configurations
• Manufacturing processes for sterile polymer solutions
• Container-closure compatibility

The key commercial point is that the original formulation patents are mature. ELIGARD was approved by the FDA in 2002, with later approvals for additional strengths and dosing intervals. Original composition and platform patents from the early development period would ordinarily have reached their 20-year terms, subject to patent-term adjustment or extension and the specific claim scope.

A current freedom-to-operate review must distinguish between:

1. Expired platform patents.
2. Later improvement patents.
3. Orange Book-listed patents.
4. Non-listed process, device, trade-secret, and know-how rights.
5. Third-party patents covering PLGA attributes, sterile filling, or depot manufacturing.

The most important remaining barrier may be know-how rather than basic excipient identity. A competitor can purchase PLGA and NMP but still lack the process controls required to match ELIGARD’s release curve and injection performance.

What is the FDA and Orange Book status of ELIGARD?

ELIGARD is an FDA-approved prescription product under NDA 021343. It is approved for the palliative treatment of advanced prostate cancer. The product is regulated as a drug, although its delivery system creates combination-product-like technical issues involving the formulation, syringe, needle, mixing process, and container closure.

The FDA label identifies the active ingredient and the ATRIGEL Delivery System. Approval of the different strengths occurred over multiple years, creating separate regulatory and commercial milestones rather than a single launch event (FDA, 2024).

Orange Book and exclusivity position

ELIGARD’s market protection should be analyzed through four separate questions:

Protection category	ELIGARD position
New chemical entity exclusivity	Expired
Original formulation patent term	Historically important, generally mature
Later formulation or device patents	Must be assessed claim by claim
Regulatory exclusivity	No current NCE exclusivity expected for the long-established product

The FDA Orange Book is the controlling source for currently listed patents and exclusivity. Orange Book status can change through patent-listing updates, delistings, pediatric exclusivity, court outcomes, or corrections. A transaction or launch decision should use the current FDA listing rather than relying on historical patent databases (FDA, 2025).

When does ELIGARD lose exclusivity?

ELIGARD’s original regulatory exclusivity has expired. The product’s current competitive protection is therefore likely to depend on patent scope, regulatory pathway, manufacturing complexity, and commercial execution.

For a conventional generic leuprolide product, the key pathway would generally be an abbreviated new drug application if the applicant can satisfy the applicable pharmaceutical equivalence, bioequivalence, quality, and product-specific requirements. A complex depot may require extensive comparative characterization and may face FDA requirements beyond those used for an immediate-release small molecule.

The relevant launch scenarios are:

Scenario	Commercial effect
No enforceable formulation patent remains	Generic or follow-on entry can proceed after FDA approval
Valid listed patent remains and is not licensed	Paragraph IV litigation may delay launch
Paragraph IV certification with litigation	A 30-month stay may apply under the Hatch-Waxman framework
Patent settlement permits a later launch	Entry date depends on the agreement
Follow-on uses a different depot technology	Patent risk may fall, but clinical and regulatory burden may rise
Applicant develops a new indication or dosing interval	Separate method-of-use and regulatory issues arise

Are there Paragraph IV challenges to ELIGARD?

Paragraph IV risk must be evaluated against the current Orange Book-listed patents for the specific ELIGARD reference presentation. Historical patent challenges and litigation involving leuprolide products do not automatically apply to every ELIGARD strength.

A meaningful Paragraph IV analysis should examine:

• The NDA reference product and strength.
• Every listed patent and expiration date.
• Whether the proposed product is an ANDA or 505(b)(2) product.
• The scope of composition, method, kit, and device claims.
• Whether the proposed formulation uses the same PLGA/NMP architecture.
• The likelihood of a 30-month stay.
• Any launch-at-risk exposure.
• Settlement terms, authorized-generic provisions, and supply restrictions.

Patent litigation may be avoided if the applicant uses a materially different delivery system and pursues a 505(b)(2) strategy. That route can reduce direct infringement exposure but may require clinical bridging, comparative pharmacokinetics, immunogenicity or local-tolerance data, and a full explanation of formulation differences.

How strong is the ELIGARD patent estate?

The estate is stronger as a technical and manufacturing barrier than as a basic composition barrier.

Stronger claim areas

• Specific release profiles tied to defined polymer and solvent parameters
• Depot formulations with precise PLGA composition
• Multi-month leuprolide release
• Mixing and administration systems
• Sterile manufacture of high-viscosity polymer solutions
• Container-closure and syringe compatibility
• Manufacturing controls that prevent dose segregation or polymer precipitation

Weaker claim areas

• Broad claims to leuprolide alone
• Broad claims to PLGA as a biodegradable polymer
• Broad claims to NMP as a solvent
• Generic claims to a subcutaneous depot without specific performance limitations

The practical strength of the estate depends on whether a competitor can design around the claimed polymer attributes while reproducing the clinical release profile. A different polymer, solvent, depot geometry, or administration route may avoid literal infringement but increase regulatory development risk.

What excipient commercial opportunities exist around ELIGARD?

The largest opportunity is platform substitution or supply-chain specialization, not commodity NMP sales.

1. Pharmaceutical-grade PLGA supply

A supplier can compete on:

• Narrow molecular-weight distribution
• Lot-to-lot lactide:glycolide consistency
• Controlled end-group chemistry
• Low residual solvent
• Low endotoxin and bioburden
• Custom degradation rates
• Documentation for complex injectable products
• Dual sourcing and supply security

A supplier with validated PLGA grades for in situ depots can support multiple products beyond leuprolide, including long-acting peptides, proteins, antipsychotics, and hormone therapies.

2. Custom excipient development

Drug developers may need a polymer grade engineered for:

• Lower initial burst
• Longer terminal release
• Reduced injection volume
• Lower viscosity
• Improved suspension stability
• Reduced local inflammation
• Better syringeability
• Less sensitivity to temperature excursions

Custom excipient development can create formulation-specific switching costs. Once a drug developer validates a polymer grade and manufacturing process, replacing the supplier may require comparability work and stability studies.

3. Alternative depot technologies

Potential alternatives include:

• In situ forming depots using other biodegradable polymers
• Injectable microspheres
• Lipid-based depots
• Biodegradable implants
• Hydrogel systems
• Nanoparticle suspensions
• Solid-state implants with one-year release

The commercial tradeoff is direct. A platform that avoids ELIGARD patent claims may require more complex manufacturing, larger clinical packages, or a new administration device.

4. Device and kit optimization

ELIGARD’s two-component presentation creates opportunities in:

• Closed-system mixing
• Automated reconstitution
• Low-dead-volume syringes
• Reduced injection force
• Needle-size optimization
• Temperature-controlled packaging
• Error-resistant administration kits
• Prefilled or dual-chamber systems

Device improvements can reduce preparation time and dosing errors. They may also support a new combination-product patent position even when broad formulation patents have expired.

5. Contract development and manufacturing

A contract manufacturer with sterile capabilities for viscous polymer formulations can offer:

• Polymer solution compounding
• Aseptic filling
• Dual-syringe or dual-chamber assembly
• In-process viscosity testing
• Drug-content uniformity controls
• Accelerated and real-time stability programs
• Extractables and leachables testing
• Container-closure integrity testing

This capability is scarce relative to conventional liquid filling because the product must maintain polymer homogeneity and consistent reconstitution behavior.

What manufacturing barriers affect generic ELIGARD entry?

The principal manufacturing barriers are process-specific.

Polymer solution homogeneity

PLGA/NMP systems can be highly viscous. Inadequate mixing may produce concentration gradients, inconsistent injection force, or dose variability.

Sterile processing

The product must meet sterile injectable requirements while preserving polymer molecular weight and drug stability. Terminal sterilization may be unsuitable, making aseptic processing and sterile component control important.

Reconstitution performance

The final product must mix within an acceptable time and produce a consistent injectable formulation. Factors include:

• Mixing energy
• Component temperature
• Polymer concentration
• Syringe geometry
• Needle diameter
• Hold time after mixing
• Operator technique

Release testing

Routine quality control may not fully predict in vivo release. Developers need discriminatory in vitro release methods that distinguish polymer-grade, particle-size, molecular-weight, and process changes.

Local tolerability

NMP and PLGA degradation products can affect injection-site tolerability. A formulation with equivalent systemic exposure may still differ in pain, swelling, induration, or inflammation.

What generic launch risks exist for ELIGARD?

A generic launch faces five principal risks:

1. Formulation equivalence risk: Matching leuprolide content is insufficient if release kinetics differ.
2. Patent risk: A later improvement patent may cover the selected polymer, kit, or administration method.
3. Regulatory risk: FDA may require more extensive product-specific characterization than expected.
4. Manufacturing risk: Scale-up can change viscosity, mixing, release, and stability.
5. Commercial risk: Low-frequency dosing and physician familiarity favor the incumbent, while payers may demand substantial discounts.

The most credible generic strategy is likely a product that preserves the clinical convenience of a long-acting subcutaneous depot while using a demonstrably non-infringing formulation and a robust comparative release package.

Which companies challenge ELIGARD commercially?

The competitive set includes branded and generic manufacturers active in:

• Leuprolide acetate depots
• GnRH agonists
• GnRH antagonists
• Long-acting injectable formulations
• Prostate-cancer supportive and hormonal therapies

The most direct branded competition comes from Lupron Depot and other leuprolide products. Degarelix and relugolix compete on mechanism and treatment experience rather than on excipient similarity. Generic competition is more likely to emerge through complex injectable development than through a simple oral-style ANDA model.

Tolmar’s commercial defense is based on product availability across dosing intervals, physician familiarity, manufacturing execution, and the technical complexity of the ATRIGEL system. A successor product could strengthen that position through a simpler administration process, longer dosing interval, or lower injection volume.

What revenue exposure does ELIGARD create?

ELIGARD revenue is exposed to four factors:

Exposure	Effect on value
Generic entry	Price erosion and formulary substitution
GnRH antagonist adoption	Share loss where rapid testosterone suppression is preferred
Treatment duration	Longer persistence increases recurring depot demand
Dosing convenience	Six-month dosing can support retention and reduce administration burden

Tolmar is privately held, so product-level ELIGARD revenue is not disclosed in the same detail as revenue for publicly traded pharmaceutical companies. Valuation should use prescription volume, wholesale acquisition cost, net price, payer mix, gross-to-net deductions, and the expected timing of generic or follow-on entry rather than relying on unverified product-sales estimates.

How should a competitor design around ELIGARD?

A practical design-around program would evaluate three routes.

Route 1: Same active ingredient, different depot architecture

A developer could retain leuprolide acetate but change the polymer system, solvent, depot mechanism, or administration format. This may reduce patent overlap but increase bridging requirements.

Route 2: Same ATRIGEL concept, different claim-limiting parameters

The developer could use PLGA/NMP while varying polymer ratio, molecular weight, end groups, drug loading, or release profile. This route may preserve development speed but carries greater infringement risk.

Route 3: Different active ingredient or mechanism

A GnRH antagonist or another androgen-deprivation approach avoids direct ELIGARD formulation patents. The commercial product would compete clinically rather than through formulation equivalence.

The preferred route depends on whether the business objective is rapid generic substitution, a differentiated specialty product, or a platform asset for multiple long-acting drugs.

Key Takeaways

• ELIGARD’s core excipient strategy uses PLGA and NMP in the ATRIGEL in situ depot system.
• PLGA attributes, not merely polymer identity, control release, stability, and tolerability.
• NMP is a functional solvent with commercial importance in injection behavior and depot formation.
• Original ELIGARD exclusivity is mature; current risk depends on active listed patents, later improvements, and manufacturing know-how.
• Generic entry is technically difficult because of release-profile matching, sterile processing, reconstitution, and local tolerability.
• The strongest commercial opportunities are custom PLGA supply, depot-platform licensing, sterile manufacturing, and injection-kit optimization.
• GnRH antagonists create a clinical competitive threat that excipient improvements cannot fully eliminate.
• A successful follow-on product should target lower injection burden, simpler preparation, reliable release, and a defensible patent position.

FAQs

Can PLGA and NMP be replaced in an ELIGARD follow-on product?

Yes. A follow-on product can use another polymer, solvent, depot mechanism, or delivery device, but formulation changes may increase FDA bridging and clinical requirements.

Is NMP the main patent barrier for ELIGARD?

No. NMP is widely used and generally functions as a commercially available pharmaceutical solvent. The stronger barriers are the integrated polymer-solvent-drug system, release profile, manufacturing process, and product-specific know-how.

Does ELIGARD have biosimilar competition?

No. Leuprolide acetate is a synthetic peptide drug, not a biologic regulated through the biosimilar pathway. Competition is more likely through an ANDA, 505(b)(2) application, or a separately approved long-acting product.

Can a new excipient create a new ELIGARD patent estate?

Yes. A new polymer grade, solvent system, depot architecture, delivery kit, or manufacturing method can support composition, formulation, process, device, or method-of-use claims if the invention satisfies patentability requirements.

What is the most attractive licensing opportunity related to ELIGARD?

The most attractive opportunity is a validated long-acting depot platform that can deliver leuprolide or other peptides with reduced injection volume, predictable six-month release, and a formulation that avoids the incumbent’s enforceable claims.

References

1. U.S. Food and Drug Administration. (2024). ELIGARD (leuprolide acetate) for injectable suspension: Prescribing information.
2. U.S. Food and Drug Administration. (2025). Approved drug products with therapeutic equivalence evaluations, Orange Book.
3. U.S. Food and Drug Administration. (1997). Guidance for industry: Drug products or biological products that contain nanomaterials.
4. European Medicines Agency. (2014). Guideline on quality of oral modified release products.
5. National Cancer Institute. (2024). Leuprolide acetate. U.S. National Institutes of Health.