United States Patent 4,421,762: Scope, Claims, Expiration, and Cromolyn Sodium Patent Landscape

U.S. Patent No. 4,421,762 covered oral treatment of allergy to ingested allergens using cromolyn, specifically 1,3-bis(2-carboxychromon-5-yloxy)-2-hydroxypropane and its salts. The broadest claim required a daily oral dose of 20 to 4,000 mg. The patent issued on December 20, 1983, and its ordinary 17-year patent term expired on December 20, 2000. It no longer creates a U.S. patent barrier to generic cromolyn sodium, oral food-allergy products, or competing formulations.

The patent was an expired method-of-treatment patent. Its commercial importance was linked to the use of disodium cromoglycate, also called cromolyn sodium, for food allergy and other reactions to ingested allergens. The claims did not cover a new chemical entity, a general composition of matter, or a manufacturing process.

What drug and active ingredient does U.S. Patent 4,421,762 cover?

The claimed active ingredient is 1,3-bis(2-carboxychromon-5-yloxy)-2-hydroxypropane, commonly known as cromoglycic acid or cromoglicic acid. Its disodium salt is cromolyn sodium, also called sodium cromoglycate or disodium cromoglycate.

The patent covers:

The parent cromoglycic acid compound.
Therapeutically acceptable salts.
Ammonium salts.
Alkali-metal salts, including sodium and potassium salts.
Alkaline-earth-metal salts.
Specifically, the disodium salt of the compound.
Oral treatment of allergy to an ingested allergen.
Daily doses from 20 to 4,000 mg.
Unit doses from 20 to 1,000 mg, with narrower ranges of 100 to 750 mg and 200 to 500 mg.
Daily doses from 40 to 1,000 mg.
Treatment of allergies associated with milk, eggs, fruit, fish, nuts, shellfish, meat, vegetables, and cereal flour.

The patent does not claim every use of cromolyn sodium. It is limited to the claimed route, patient condition, active ingredient, and dosage parameters.

What are the independent and dependent claims?

Claim 1 is the only independent claim. It requires four principal elements:

A method of treating an allergy to an ingested allergen.
Oral, or per os, administration.
A daily dosage of 20 to 4,000 mg.
Administration of cromoglycic acid or a therapeutically acceptable salt.

A product would fall within claim 1 only if the facts establish that the product is administered orally to a patient with an allergy to an ingested allergen and that the administered daily amount falls within the stated range.

Claims 2 through 8 narrow claim 1 as follows:

Claim	Limitation
1	Oral treatment of allergy to an ingested allergen; 20-4,000 mg daily
2	Ammonium, alkali-metal, or alkaline-earth-metal salt
3	Disodium salt
4	Unit doses of 20-1,000 mg
5	Unit doses of 100-750 mg
6	Unit doses of 200-500 mg
7	40-1,000 mg per day
8	Allergy to specified foods or food categories

Claim 3 is the commercially most relevant dependent claim because it targets cromolyn sodium. Claims 4 through 7 create dosage-specific subranges but do not expand the patent beyond claim 1.

How broad is the scope of claim 1?

Claim 1 is broad in therapeutic and dosage scope but narrow in chemical and clinical context.

Chemical scope

The claim is not limited to the disodium salt. It covers the parent acid and therapeutically acceptable salts. Claim 2 expressly identifies salt categories, while claim 3 narrows the scope to the disodium salt.

A competing product using a different salt would not automatically avoid claim 1 if the salt qualifies as therapeutically acceptable and the product meets the other limitations. A non-salt formulation of the parent acid could also fall within claim 1.

Route of administration

The phrase “per os administration” limits the claim to oral administration. Inhaled, intranasal, ophthalmic, injectable, or topical cromolyn products would not satisfy this limitation solely because they contain the same active ingredient.

An oral tablet, capsule, powder, granule, suspension, solution, or other oral dosage form could satisfy the route limitation if it delivers the claimed active ingredient.

Disease and patient limitation

The patient must have an allergy to an ingested allergen. The claim is directed to food allergy or another allergic response caused by an allergen consumed by mouth.

Claim 8 identifies particular food allergens. It does not necessarily limit claim 1 to only those listed foods because claim 8 is dependent. Claim 1 can reach other ingested allergens if the remaining limitations are met.

The claim does not expressly require a particular mechanism, antibody class, severity level, diagnostic test, or clinical endpoint. It also does not require that cromolyn be administered before food exposure, although treatment protocols and product labeling could affect infringement analysis.

Dosage limitation

Claim 1 requires a daily dose between 20 and 4,000 mg. The endpoints are ordinarily treated as included in the claimed range.

Claims 4 through 6 address unit dose amounts, while claim 7 addresses a narrower daily dose range. A regimen can infringe claim 1 without infringing claims 4 through 7 if it meets the broader daily-dose requirement but falls outside the narrower unit-dose or daily-dose subranges.

When did U.S. Patent 4,421,762 expire?

U.S. Patent 4,421,762 issued on December 20, 1983. Because it is an early U.S. patent governed by the pre-URAA patent-term framework, its ordinary term was 17 years from grant. The ordinary expiration date was therefore December 20, 2000. [1][2]

Event	Date or status
Patent issued	December 20, 1983
Ordinary U.S. term	17 years from grant
Ordinary expiration	December 20, 2000
Current status	Expired
Current enforceability	None

No current patent-term extension or patent-term adjustment is generally associated with this historic method patent. Even if a historical regulatory or term calculation had affected the final date, the patent has been expired for more than two decades.

An expired patent cannot support a new U.S. infringement action. It also cannot block an ANDA applicant, an abbreviated application, or a commercial launch based on patent rights.

What is the Orange Book status of U.S. Patent 4,421,762?

U.S. Patent 4,421,762 has no current blocking Orange Book effect. The FDA Orange Book lists patents associated with approved drug products when the statutory and regulatory listing requirements are met, but an expired patent does not create current market exclusivity. [3]

The relevant cromolyn sodium product history includes oral cromolyn products used for mastocytosis and other cromolyn products administered through inhaled, nasal, or ophthalmic routes. FDA approval of an oral cromolyn product does not establish approval for the claimed food-allergy indication.

The key distinction is:

The patent concerns oral cromolyn treatment for allergy to ingested allergens.
FDA approval depends on the approved product, indication, dosage form, labeling, and regulatory application.
Orange Book listing does not extend an expired patent.
FDA approval for mastocytosis does not automatically approve the product for food allergy.

A current applicant would assess any listed patents associated with the specific reference-listed drug, not rely on the historical status of Patent 4,421,762.

Does the patent create Paragraph IV risk?

No current Paragraph IV risk arises from Patent 4,421,762 because the patent expired in 2000.

Historically, a generic applicant could have faced a Paragraph IV certification if the patent had been listed against a relevant reference product and the applicant sought approval before expiration. Under the Hatch-Waxman framework, a Paragraph IV certification challenges the validity, enforceability, or infringement of a listed patent. [4]

That issue is no longer material for this patent:

No 30-month stay can be triggered by an expired patent.
No 180-day generic exclusivity period can be based on a current challenge to this patent.
No launch injunction can issue from this patent.
A generic applicant does not need to design around an expired patent for U.S. launch purposes.

Any present patent certification analysis would focus on later patents listed for the particular cromolyn sodium reference product, if any.

What formulations are protected by the patent?

The patent claims treatment by active ingredient, route, and dose. It does not expressly claim a particular tablet, capsule, liquid, excipient system, coating, particle size, release profile, or manufacturing process.

Potentially covered dosage forms during the patent term included:

Oral solutions.
Oral suspensions.
Capsules.
Tablets.
Powders.
Granules.
Sachets or other oral unit-dose products.

The claims do not require immediate release or sustained release. They also do not require a specific concentration or excipient. A later formulation patent could have added protection for a particular delivery system, stability profile, taste-masking technology, or release mechanism, but such protection would be separate from Patent 4,421,762.

What method-of-use protection does the patent provide?

The patent is principally a method-of-use patent. Its legal value depended on the combination of:

Cromoglycic acid or a permitted salt.
Oral administration.
A patient with allergy to an ingested allergen.
A specified daily dosage.

It does not cover:

Cromolyn sodium for asthma generally.
Cromolyn sodium for allergic conjunctivitis generally.
Cromolyn sodium for allergic rhinitis generally.
Nonoral administration.
Treatment of mastocytosis as a general indication.
Manufacturing cromolyn sodium.
A composition containing cromolyn sodium without the claimed treatment use.

The claim language also creates an indirect-infringement question for product suppliers. A product label expressly directing use for food allergy at the claimed dose would have presented a stronger inducement theory during the patent term than a label limited to an unrelated approved indication.

How strong was the patent estate?

The estate was commercially narrow compared with a modern drug patent portfolio.

Estate category	Position under Patent 4,421,762
New chemical entity	Not covered
Composition of matter	Not covered as a new invention
Oral food-allergy method	Covered
Salt selection	Covered through dependent claims
Dosage range	Covered
Unit-dose range	Covered through dependent claims
Formulation technology	Not expressly covered
Manufacturing process	Not covered
Inhaled or ophthalmic use	Not covered
Current enforceability	None

Its strongest historical position was claim 3 combined with claims 4 through 7: oral disodium cromoglycate administered in specified unit and daily doses to patients with food allergy. Its principal weakness was dependence on patient-use facts and the known nature of cromolyn as an established pharmacological compound.

The patent’s value was also constrained by the need to prove the claimed indication and dose. A generic product label that omitted food-allergy treatment could have reduced direct label-based infringement exposure, although actual prescribing, promotional conduct, and induced-use theories would still have required separate analysis.

Which companies challenged or licensed the patent?

The patent is now expired, so current challenge activity is not commercially relevant. A complete historical list of Paragraph IV filers, district-court defendants, settlements, or licenses cannot be established from the claim text alone. The patent record identifies the historical owner or applicant associated with Fisons Limited, but Patent 4,421,762 did not create an active licensing or litigation issue after its expiration.

Fisons was a major historical developer and marketer of cromolyn products. Cromolyn sodium products later appeared through other pharmaceutical companies and generic manufacturers. Those later commercial relationships do not revive or extend the patent.

What is the biosimilar risk for cromolyn sodium?

Cromolyn sodium is a chemically synthesized small molecule, not a biologic. Biosimilar regulation under the Public Health Service Act is therefore not the applicable pathway. [5]

Competitive products would generally use:

An ANDA for a therapeutically equivalent small-molecule product.
A 505(b)(2) application for a product relying in part on existing literature or an approved product while introducing differences in formulation, route, or indication.
A full NDA where the product or use requires an independent clinical and regulatory package.

The principal regulatory issues are pharmaceutical equivalence, bioavailability where relevant, product quality, dosage-form performance, labeling, and the applicable reference product.

How does Patent 4,421,762 compare with competing cromolyn patent categories?

Patent category	Typical subject matter	Status relative to Patent 4,421,762
Early cromolyn compound patents	Chemical compound and salts	Generally expired
Patent 4,421,762	Oral treatment of ingested-allergen allergy	Expired December 20, 2000
Formulation patents	Stability, concentration, taste masking, release	Must be analyzed separately
Manufacturing patents	Synthesis, purification, crystallization	Must be analyzed separately
Later method patents	New disease, regimen, or patient population	Potentially separate, but not established by this patent
Regulatory exclusivity	NDA-based exclusivity	Separate from patent term

No active patent can be inferred merely from the existence of this historic patent. A freedom-to-operate review for a current cromolyn product would need to examine later U.S. patents, FDA-listed patents, patent-family continuations, and formulation or manufacturing claims.

What generic launch scenarios exist?

For a current oral cromolyn sodium product, the expired patent presents no launch obstacle. The main scenarios are:

An ANDA for a therapeutically equivalent oral product where an appropriate reference-listed drug exists.
A 505(b)(2) application for a new oral formulation, concentration, dosing schedule, or indication.
A full NDA if the proposed product cannot rely sufficiently on an existing approval or published evidence.
A compounding or nonapproved commercial pathway, subject to separate FDA requirements and restrictions.

A product labeled specifically for food allergy could rely on the absence of enforceable rights under Patent 4,421,762. It would still need FDA authorization for that indication.

What geographic protection remains?

None remains in the United States under Patent 4,421,762. U.S. expiration does not determine the status of corresponding foreign patents. Patent-family members in Europe, Canada, Japan, or other jurisdictions required independent term and lapse analysis.

A U.S. launch can therefore proceed without this patent, but international launch planning should not assume that every corresponding foreign right expired on the same date. Patent terms, filing dates, prosecution histories, and maintenance requirements differ by jurisdiction.

Key Takeaways

U.S. Patent 4,421,762 claimed oral treatment of allergy to ingested allergens with cromoglycic acid or an acceptable salt.
The broadest daily-dose range was 20 to 4,000 mg.
The commercially relevant compound was disodium cromoglycate, or cromolyn sodium.
Claims 4 through 7 narrowed the invention by unit dose and daily dose.
The patent issued on December 20, 1983.
Its ordinary U.S. term expired on December 20, 2000.
It creates no current Paragraph IV, Orange Book, injunction, or generic-launch risk.
It does not claim a new chemical entity, formulation, manufacturing process, or nonoral use.
Cromolyn sodium is a small molecule, so biosimilar rules do not apply.
Current freedom-to-operate analysis must focus on later formulation, manufacturing, regulatory, and method-of-use rights.

FAQs

Is cromolyn sodium still protected by U.S. Patent 4,421,762?

No. The patent expired on December 20, 2000, and cannot currently be enforced.

Can a generic company market oral cromolyn sodium for food allergy?

The expired patent does not prevent marketing. The company must still satisfy FDA requirements for the selected regulatory pathway and obtain approval for the proposed indication and dosage form.

Does the patent cover Gastrocrom?

The patent could have covered oral cromolyn use within its claim limitations during its term, but it does not currently block Gastrocrom or a competing oral cromolyn product. Product-specific FDA approval and later patent listings must be assessed separately.

Does claim 8 limit all claims to milk, eggs, fish, and the other listed foods?

No. Claim 8 is dependent on claim 1. It narrows the method to specified food allergens but does not restrict the scope of claim 1 to only those allergens.

Are cromolyn manufacturing patents still relevant?

They can be relevant to a current product if a later patent remains in force. Patent 4,421,762 itself does not claim a manufacturing process, and its expiration does not resolve the status of later process or formulation patents.

References

United States Patent and Trademark Office. (1983). U.S. Patent No. 4,421,762, treatment of food allergy.
United States Code, 35 U.S.C. § 154. Patent term.
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations.
United States Code, 21 U.S.C. § 355(j). Abbreviated applications and patent certifications.
United States Code, 42 U.S.C. § 262. Regulation of biological products and biosimilar products.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
United Kingdom	6911/72	Feb 15, 1972
United Kingdom	4912/74	Feb 02, 1974

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
United Kingdom	1423985	⤷ Start Trial
Malaysia	7700009	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 4,421,762

Summary for Patent: 4,421,762