Mast Cell Stabilizer Drug Class List

Drugs in Drug Class: Mast Cell Stabilizer

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Glenmark Speclt	RYALTRIS	mometasone furoate; olopatadine hydrochloride	SPRAY, METERED;NASAL	211746-001	Jan 13, 2022		RX	Yes	Yes	12,064,442
Glenmark Speclt	RYALTRIS	mometasone furoate; olopatadine hydrochloride	SPRAY, METERED;NASAL	211746-001	Jan 13, 2022		RX	Yes	Yes	10,376,526		Y
Glenmark Speclt	RYALTRIS	mometasone furoate; olopatadine hydrochloride	SPRAY, METERED;NASAL	211746-001	Jan 13, 2022		RX	Yes	Yes	10,016,443
Glenmark Speclt	RYALTRIS	mometasone furoate; olopatadine hydrochloride	SPRAY, METERED;NASAL	211746-001	Jan 13, 2022		RX	Yes	Yes	12,303,635		Y	Y
Glenmark Speclt	RYALTRIS	mometasone furoate; olopatadine hydrochloride	SPRAY, METERED;NASAL	211746-001	Jan 13, 2022		RX	Yes	Yes	10,517,880		Y

Mast Cell Stabilizer Drug Market Dynamics and Patent Landscape

Last updated: July 31, 2026

Mast cell stabilizers are a mature, largely generic drug class with limited remaining composition-of-matter protection. Cromolyn sodium, nedocromil, ketotifen, pemirolast, lodoxamide, and related ophthalmic products have mostly lost core patent protection. Commercial competition is driven by OTC switching, generic manufacturing, formulation convenience, combination therapy, and brand distribution rather than patent exclusivity. The main U.S. growth segments are OTC allergic-conjunctivitis products and prescription products that combine mast-cell stabilization with antihistamine activity.

What drugs are classified as mast cell stabilizers?

Mast cell stabilizers prevent or reduce mediator release from sensitized mast cells. They are used primarily for allergic conjunctivitis, allergic rhinitis, asthma prophylaxis, and selected gastrointestinal or systemic mast-cell conditions.

Active ingredient	Principal products or brands	Main dosage forms	U.S. commercial status
Cromolyn sodium	Gastrocrom, generic cromolyn	Oral concentrate, inhalation solution, nasal spray, ophthalmic solution	Generic and limited branded availability
Nedocromil sodium	Alocril, Tilade	Ophthalmic solution, inhalation product	Largely discontinued or replaced
Ketotifen fumarate	Zaditor, Alaway, generic ketotifen	Ophthalmic solution	OTC and generic
Olopatadine hydrochloride	Pataday, Patanol, Pazeo	Ophthalmic solution or spray	OTC and prescription; dual antihistamine/mast-cell activity
Lodoxamide tromethamine	Alomide	Ophthalmic solution	Prescription; limited commercial presence
Pemirolast potassium	Alamast	Ophthalmic solution	Discontinued or commercially limited
Azelastine hydrochloride	Optivar and combination nasal products	Ophthalmic and nasal products	Generic; primarily positioned as an antihistamine
Epinastine hydrochloride	Elestat and generic products	Ophthalmic solution	Generic; dual antihistamine and mast-cell activity

Cromolyn sodium is the most historically representative pure mast-cell stabilizer. Ketotifen and olopatadine have stronger current commercial positions because they combine mast-cell stabilization with H1-antihistamine activity and provide faster symptom relief than older stabilizers.

The class is composed almost entirely of small molecules. Biosimilar competition is therefore not a direct issue. Competition comes from generics, OTC products, antihistamines, corticosteroid sprays or drops, leukotriene modifiers, and biologics used in severe allergic or eosinophilic disease.

What patents protect mast cell stabilizer drugs?

The original composition-of-matter patents for the major mast cell stabilizers have expired.

Drug	Original innovator	Core patent position	Current patent relevance
Cromolyn sodium	Fisons and related commercial partners	Compound and early pharmaceutical-use patents originated in the 1960s and 1970s	Expired; no meaningful U.S. composition-of-matter barrier
Nedocromil sodium	Fisons	Compound and formulation patents originated before modern U.S. patent-term rules	Expired
Ketotifen	Sandoz/Novartis commercial lineage	Early compound patents expired	Expired; product competition is generic and OTC-driven
Lodoxamide	Alcon	Early compound and ophthalmic-use patents expired	Expired
Pemirolast	Allergan and related commercial entities	Early compound and ophthalmic-use patents expired	Expired
Olopatadine	Alcon	Original compound and formulation patents expired or reached the end of their commercial life	No durable U.S. core patent barrier for generic entry
Epinastine	Boehringer Ingelheim and related licensors	Original compound patents expired	Expired

The relevant patent categories were:

1. Composition-of-matter patents covering the active ingredient.
2. Salt and crystal-form patents.
3. Ophthalmic, nasal, inhaled, or oral formulations.
4. Method-of-use patents covering allergic conjunctivitis, asthma, rhinitis, or gastrointestinal disease.
5. Manufacturing and purification patents.
6. Combination patents pairing mast-cell stabilization with antihistamine activity.

The remaining value of these patent categories is limited because the active ingredients are old, the major products have generic equivalents, and many branded products have been discontinued or converted to OTC status.

When do mast cell stabilizer drugs lose exclusivity?

Most major mast cell stabilizers lost regulatory and patent exclusivity decades ago.

Product or active ingredient	Key FDA timing	Exclusivity position
Cromolyn inhalation products	Initial U.S. approvals in the 1970s	Core exclusivity expired
Gastrocrom oral concentrate	FDA approval in the 1980s	Core exclusivity expired
Nedocromil inhalation and ophthalmic products	U.S. approvals in the late 1980s and 1990s	Core exclusivity expired
Alomide, lodoxamide	U.S. approval in the 1990s	Core exclusivity expired
Alamast, pemirolast	U.S. approval in the 1990s	Core exclusivity expired
Patanol, olopatadine	U.S. approval in 1996	Core exclusivity expired; OTC conversion followed
Zaditor, ketotifen	U.S. OTC launch in 2006	No prescription-style market exclusivity
Pataday, olopatadine	OTC switch in 2020	OTC monograph and brand protection, not meaningful patent exclusivity

FDA Orange Book-listed patents for older products have either expired, been delisted, or have little practical effect on generic entry. A product can retain an Orange Book listing for a formulation or method-of-use patent while still facing generic entry for nonprotected indications or dosage forms. The class does not have a current U.S. patent estate comparable to newer specialty drugs.

What is the Orange Book status of mast cell stabilizers?

The Orange Book is most relevant to approved prescription products and their abbreviated new drug applications. It is less informative for OTC products sold under the FDA monograph system.

Cromolyn sodium

Cromolyn sodium prescription products have long been exposed to generic competition. Generic versions of inhalation solution, ophthalmic solution, and other presentations have been marketed at different times. Gastrocrom is a prescription oral concentrate with limited commercial scale and no active core patent protection comparable to a modern branded specialty drug.

Olopatadine

Olopatadine has the largest commercial footprint among products with mast-cell-stabilizing activity. Patanol and Pataday were prescription products before OTC switches. The OTC versions compete under FDA nonprescription requirements, while generic prescription products compete through the abbreviated new drug application pathway.

Ketotifen

Ketotifen ophthalmic products are primarily OTC. Zaditor and Alaway compete with store-brand and generic products. Patent disputes are not the main market constraint because market access depends on manufacturing cost, retail placement, and brand recognition.

Older ophthalmic products

Lodoxamide, pemirolast, and nedocromil ophthalmic products have limited current market importance. Their Orange Book relevance is reduced by discontinuations, low prescribing volumes, and availability of newer OTC antihistamine/mast-cell stabilizer products.

Which companies are challenging mast cell stabilizer patents?

Generic manufacturers have challenged or entered most of the class without facing current, durable patent barriers. Relevant competitors include:

• Akorn and other ophthalmic generic manufacturers.
• Bausch + Lomb.
• Teva Pharmaceuticals.
• Sandoz.
• Hikma Pharmaceuticals.
• Perrigo.
• Viatris.
• Dr. Reddy's Laboratories.
• Apotex.
• Major private-label OTC distributors.

The competitive structure differs by product:

Segment	Main competitors	Entry mechanism
Cromolyn prescription products	Generic drug manufacturers and hospital suppliers	ANDA or legacy generic approvals
Ketotifen ophthalmic	Brand, private-label OTC, and generic suppliers	OTC distribution and abbreviated approvals
Olopatadine ophthalmic	Pataday, store brands, generics, and competing antihistamines	Prescription generic and OTC retail channels
Lodoxamide and pemirolast	Limited generic suppliers	Small-market prescription competition
Nasal mast-cell stabilizers	Cromolyn and antihistamine nasal products	OTC competition and generic prescription products

The class has little current Paragraph IV litigation activity compared with recently approved small-molecule drugs. Paragraph IV challenges were more relevant during the original genericization of branded ophthalmic products, particularly where formulation or method-of-use patents were listed. Most remaining disputes would be commercial rather than class-wide patent events.

What formulation patents protect mast cell stabilizer products?

Formulation protection has been more commercially relevant than active-ingredient protection, especially for ophthalmic products.

Potential formulation claim categories include:

• Preservative-free multidose ophthalmic delivery.
• Improved aqueous solubility.
• pH-controlled solutions.
• Isotonic ophthalmic compositions.
• Reduced irritation formulations.
• Stabilized solutions with longer shelf life.
• Metered-dose nasal delivery.
• Inhalation solutions compatible with nebulizers.
• Combination formulations containing an antihistamine and a mast-cell stabilizer.
• Packaging systems that limit microbial contamination.

The strongest formulation opportunities in this class are not broad claims covering cromolyn, ketotifen, or olopatadine. They are narrow claims directed to a specific concentration range, excipient system, device, or preservative-free container. Such patents can delay direct substitution for a particular product but rarely prevent broad class competition.

For OTC ophthalmic products, commercial differentiation increasingly depends on:

• Once-daily dosing.
• Preservative-free packaging.
• Lower irritation.
• Faster onset.
• Pediatric labeling.
• Contact-lens compatibility.
• Retail availability.

These attributes can support brand pricing without creating durable patent exclusivity.

What method-of-use patents cover mast cell stabilizers?

Historical method-of-use patents covered:

• Prevention of asthma symptoms.
• Prophylaxis before allergen exposure.
• Treatment of seasonal allergic conjunctivitis.
• Treatment of perennial allergic rhinitis.
• Reduction of mast-cell mediator release.
• Gastrointestinal symptoms associated with mast-cell disorders.

Most broad method-of-use claims are expired or vulnerable to invalidity challenges based on prior clinical use and published medical literature. Narrower claims can remain relevant where they cover a new patient population, dosing schedule, or combination treatment, but the commercial effect is limited for old active ingredients.

Skin, respiratory, and gastrointestinal uses have not generated a current patent moat around the class. In severe allergic disease, newer biologics and targeted immunomodulators compete more effectively than cromolyn or older mast-cell stabilizers.

How strong is the patent estate for mast cell stabilizer drugs?

The class-wide patent estate is weak.

Patent-estate factor	Assessment	Commercial effect
Composition of matter	Weak to nonexistent for major drugs	No barrier to generic active ingredients
Salt and crystal form	Generally expired or narrow	Limited
Formulation	Moderate for specific delivery systems	Can protect a product presentation
Method of use	Mostly expired or narrow	Limited indication protection
Manufacturing	Potentially relevant for quality and cost	Usually does not block finished-dose entry
Device and packaging	Relevant for preservative-free and multidose products	Supports differentiation
Regulatory exclusivity	Expired for established products	No meaningful delay to generic entry
Biosimilar protection	Not applicable	Small-molecule competition dominates

Cromolyn sodium has an especially weak patent position because its commercial and clinical history predates modern patent-term extensions. Olopatadine has greater brand value but not because of a current core patent estate. Its position comes from consumer recognition, OTC distribution, formulation quality, and the strength of the allergy-treatment category.

What generic entry risks exist for mast cell stabilizer drugs?

Generic entry risk is high across the class.

High-risk products

• Cromolyn sodium ophthalmic solution.
• Cromolyn sodium inhalation solution.
• Ketotifen ophthalmic solution.
• Prescription olopatadine ophthalmic products.
• Epinastine ophthalmic solution.

Moderate-risk products

• Preservative-free ophthalmic presentations.
• Products requiring specialized packaging.
• Low-volume inhalation solutions.
• Products with limited approved generic suppliers.

Lower direct-entry risk

Products with limited commercial availability may face less immediate generic substitution because the market is too small to attract multiple suppliers. This is a commercial limitation, not a patent advantage.

Generic launch economics are affected by:

• Small prescription volumes.
• Sterile ophthalmic manufacturing requirements.
• Drug-shortage risk.
• Limited active pharmaceutical ingredient suppliers.
• Retail channel access.
• Reimbursement pressure.
• Product discontinuations.

For an applicant, the principal barrier is often sterile manufacturing and reliable supply rather than patent infringement.

How does olopatadine compare with cromolyn and ketotifen?

Attribute	Olopatadine	Cromolyn	Ketotifen
Pharmacology	H1 antihistamine and mast-cell stabilizer	Mast-cell stabilizer	H1 antihistamine and mast-cell stabilizer
Main current use	Allergic conjunctivitis and rhinitis	Asthma prophylaxis, rhinitis, conjunctivitis, GI use	Allergic conjunctivitis
U.S. channel	OTC and prescription legacy products	Mostly prescription or limited generic channels	Predominantly OTC ophthalmic
Dosing convenience	Often once daily	Product-dependent; less convenient	Usually twice daily for common products
Patent strength	Expired core patents; brand value remains	Very weak	Expired core patents
Commercial position	Strongest branded OTC position	Mature niche	Strong OTC niche
Generic threat	High	High	High
Biosimilar relevance	None	None	None

Olopatadine has the strongest commercial profile because it combines efficacy, dosing convenience, and OTC brand recognition. Cromolyn remains relevant in selected prophylactic and gastrointestinal uses but has limited growth prospects. Ketotifen competes effectively in OTC allergic conjunctivitis but faces direct substitution from olopatadine and low-cost private-label products.

What FDA regulatory status affects the market?

FDA regulation divides the class into prescription products, generic prescription products, and OTC products.

Prescription products must generally rely on an approved NDA or ANDA. Generic applicants must demonstrate pharmaceutical equivalence and bioequivalence where applicable. Ophthalmic products also require sterile manufacturing and appropriate container-closure systems.

OTC products compete under either an OTC monograph framework or an approved switch application. The FDA approved OTC switches for major allergy products, including ketotifen and olopatadine ophthalmic products. These switches expanded consumer access and shifted competition from prescriber preference to retail distribution, packaging, advertising, and price.

The FDA has not created a separate regulatory pathway for mast-cell stabilizers. Classification depends on the active ingredient, route, indication, and product claims.

What licensing deals and commercial partnerships affect the class?

The class has a history of licensing and regional commercialization, especially for ophthalmic products. Key commercial patterns include:

• Discovery-company licensing to large pharmaceutical companies.
• Regional rights for ophthalmic products.
• Brand-to-OTC manufacturer transfers.
• Private-label supply agreements.
• Authorized generic arrangements.
• Contract manufacturing for sterile ophthalmic products.

Current deal value is generally concentrated in distribution and manufacturing rather than patent access. An acquirer evaluating a mast-cell stabilizer asset would focus on supply continuity, OTC shelf placement, regulatory status, and product differentiation. Royalty economics from expired core patents are generally immaterial.

What patent litigation affects mast cell stabilizer drugs?

The class has limited current litigation exposure. Historical disputes centered on:

• Whether an ANDA product infringed listed ophthalmic formulation patents.
• Validity of method-of-use claims.
• Patent-term calculations.
• Product-specific formulation differences.
• Regulatory exclusivity during prescription-to-OTC transitions.

There is no broad, active litigation campaign comparable to those affecting high-revenue oncology, immunology, or cardiometabolic drugs. Any litigation involving a current product is more likely to concern a narrow formulation, device, packaging system, or brand issue than the underlying mast-cell stabilizing molecule.

What is the revenue exposure and competitive outlook?

Revenue exposure is concentrated in OTC allergy products rather than prescription mast-cell stabilizers.

Commercial driver	Effect on revenue
Seasonal allergy prevalence	Supports recurring demand
OTC switch	Expands consumer access but increases price competition
Brand recognition	Supports premium pricing for Pataday and Zaditor
Private-label entry	Compresses prices
Once-daily dosing	Supports premium positioning
Preservative-free formats	Creates higher-value subsegments
Generic substitution	Reduces prescription brand revenue
Sterile manufacturing constraints	Can limit supply and support temporary pricing
New antihistamine combinations	Increase substitution pressure

The market outlook is stable to low growth for mature active ingredients. Growth is more plausible in reformulated ophthalmic products, preservative-free delivery, combination products, and consumer allergy platforms than in new indications for legacy molecules.

What generic launch scenarios are most likely?

Scenario 1: Low-cost generic substitution

Multiple suppliers enter standard ophthalmic or inhalation presentations. Prices decline, brand share falls, and the active ingredient becomes a commodity.

Scenario 2: Brand-led OTC premium

The innovator or OTC brand retains share through once-daily dosing, packaging, advertising, and retailer relationships despite generic availability.

Scenario 3: Formulation differentiation

A supplier protects or commercializes a preservative-free, multidose, or reduced-irritation formulation. The product gains limited differentiation but remains exposed to competing formulations.

Scenario 4: Supply-constrained niche

Only a small number of manufacturers maintain sterile production. Market access remains technically open, but practical competition is limited by supply economics.

Key Takeaways

• Core patents for cromolyn, nedocromil, ketotifen, lodoxamide, pemirolast, olopatadine, and epinastine are expired or commercially ineffective.
• Generic entry risk is high throughout the class.
• Formulation, packaging, and device patents are more relevant than composition-of-matter patents.
• Olopatadine and ketotifen have the strongest current OTC positions.
• Cromolyn remains clinically relevant but has limited commercial growth and weak IP protection.
• Biosimilar risk does not apply because these are small-molecule products.
• Current litigation and Paragraph IV activity are limited.
• The principal market barriers are sterile manufacturing, supply reliability, retail distribution, and brand execution.
• Licensing value is concentrated in commercial rights, manufacturing, and OTC distribution rather than patent exclusivity.

FAQs

Are mast cell stabilizers still patent protected?

The major active ingredients are not protected by active U.S. composition-of-matter patents. Narrow formulation, packaging, device, or method-of-use claims may exist for specific products.

Is cromolyn sodium still exclusive in the United States?

No. Cromolyn sodium has long been subject to generic and legacy-product competition. Its remaining commercial value is based on niche indications and availability, not patent exclusivity.

Can a generic manufacturer launch ketotifen eye drops?

Generic and private-label ketotifen ophthalmic products can enter subject to FDA requirements, applicable product-specific patents, and manufacturing compliance. The market is predominantly OTC and highly competitive.

Are olopatadine products protected by Orange Book patents?

Legacy prescription olopatadine products may have had Orange Book-listed patents, but the original patent estate has expired or lost practical blocking power. OTC olopatadine products are not evaluated solely through the Orange Book framework.

Which mast cell stabilizer has the strongest commercial position?

Olopatadine has the strongest U.S. commercial position because of its OTC conversion, once-daily products, broad consumer recognition, and dual antihistamine and mast-cell-stabilizing activity.

References

1. U.S. Food and Drug Administration. (2024). Orange Book: Approved drug products with therapeutic equivalence evaluations. https://www.accessdata.fda.gov/scripts/cder/ob/

2. U.S. Food and Drug Administration. (2024). Drugs@FDA: FDA-approved drugs. https://www.accessdata.fda.gov/scripts/cder/daf/

3. U.S. Food and Drug Administration. (2020). FDA approves first over-the-counter eye drop to treat itchy eyes due to allergies. https://www.fda.gov/

4. U.S. Food and Drug Administration. (2007). FDA approves first over-the-counter antihistamine eye drops for allergy relief. https://www.fda.gov/

5. U.S. Food and Drug Administration. (2024). Electronic Code of Federal Regulations, 21 C.F.R. Part 349: Ophthalmic drug products for over-the-counter human use. https://www.ecfr.gov/

6. National Library of Medicine. (2024). DailyMed: Drug labels. https://dailymed.nlm.nih.gov/dailymed/

7. World Health Organization. (2023). WHO guideline on the pharmacological treatment of asthma and allergic disease. World Health Organization.