# United States Patent 5,688,529: Claim Scope, Expiration, Orange Book Status, and Mycophenolate Mofetil Formulation Landscape

U.S. Patent No. 5,688,529 covers liquid and reconstitutable oral suspensions containing mycophenolate mofetil, including specific excipient systems, container presentations, and manufacturing processes. The patent is directed to the pediatric and swallowing-impaired dosage form of CellCept, rather than to mycophenolate mofetil as a molecule.

The patent’s enforceable term has expired. Its commercial significance now lies in historical formulation protection, freedom-to-operate analysis, prior-art mapping, and comparison with later oral-suspension and dry-powder technologies.

What does U.S. Patent 5,688,529 protect?

The patent protects four principal technology groups:

Technology group	Claims	Core subject matter
Ready-to-use liquid suspensions	1-5	Mycophenolate mofetil or mycophenolic acid in aqueous suspension with suspending agents, sweeteners, buffers, preservatives, flavors and masking agents
Dry granules and powder blends	6-14	Reconstitutable mycophenolate mofetil suspension, including xanthan gum, colloidal silicon dioxide, lecithin and sweeteners
Alternative dry formulation	15-17	Mycophenolate mofetil with sodium carboxymethylcellulose, sorbitol, sucrose, Pluronic F68 and potassium sorbate
Manufacturing processes	5 and 18	Sequential wet processing, dry granulation, milling and blending processes

The claims are formulation claims, not claims to the active pharmaceutical ingredient itself. A product must satisfy the claimed concentration, excipient, dosage-form and, where applicable, process limitations to fall within the literal scope.

How broad are the independent claims?

The principal independent claims are claims 1, 3, 5, 6, 15 and 18. Claims 2, 4 and 7-14 and 16-17 add narrower limitations.

Claims 1 and 3: liquid suspension ranges

Claims 1 and 3 require a liquid suspension suitable for oral administration containing 20% wt/vol mycophenolate mofetil.

Claim 1 requires:

Hydroxypropylmethylcellulose at 0.25% wt/vol
Microcrystalline cellulose at 0.25%
Xanthan gum at 0.1%
Sorbitol solution at 30%-50%
Maltitol syrup at 10%-30%
Optional sucrose, fructose, aspartame, lecithin, preservatives, flavors and color
Citric acid and dibasic sodium phosphate buffering
Purified water to volume

Claim 3 is similar but removes hydroxypropylmethylcellulose and changes several ranges. It requires:

Microcrystalline cellulose at 0.2%
Xanthan gum at 0.1%
Mycophenolate mofetil at 20% wt/vol
Sorbitol solution at 30%-50%
Maltitol syrup at 10%-30%
Buffer, flavor, masking agent and preservative components within defined ranges

These claims have meaningful formulation breadth because they use “comprising.” An accused product containing the listed ingredients within the ranges may still fall within the claim even if it contains additional excipients, subject to ordinary claim-construction principles.

The concentration limitation is restrictive. A suspension containing 100 mg/mL or 200 mg/mL mycophenolate mofetil would not literally meet a claim requiring 20% wt/vol, unless the concentration is interpreted as equivalent to 200 mg/mL or the claim is asserted under the doctrine of equivalents.

Claims 2 and 4: specific liquid formulations

Claims 2 and 4 narrow the liquid-suspension technology to defined compositions adjusted to pH 7.

Claim 2 specifies a formulation containing:

20% wt/vol mycophenolate mofetil
0.25% hydroxypropylmethylcellulose
0.25% microcrystalline cellulose
0.1% xanthan gum
50% sorbitol solution
10% sucrose
10% maltitol syrup
Lecithin
Methyl and propyl parabens
Grape and anise flavor
Citric acid and dibasic sodium phosphate
Red 28 and Blue 1 color
pH 7

Claim 4 covers a related formulation using:

0.2% microcrystalline cellulose
0.1% xanthan gum
50% sorbitol solution
10% sucrose
10% maltitol syrup
Soy lecithin
Citric acid and dibasic sodium phosphate
Methyl paraben
Flavor and color
pH 7

Because claims 2 and 4 use “consisting essentially of,” the analysis is narrower than for claims 1 and 3. Additional ingredients may be permissible only if they do not materially affect the basic and novel characteristics of the claimed suspension, including stability, taste masking, viscosity, redispersibility or oral suitability.

What do claims 6 through 14 protect?

Claims 6-14 cover dry granulations or powder blends that are reconstituted with water to form an oral suspension.

Claim 6 requires, after constitution:

Mycophenolate mofetil at 200 mg/mL
Xanthan gum at 0.5-1.5 mg/mL
Colloidal silicon dioxide at 5-10 mg/mL
Soy lecithin at 1-2 mg/mL
Optional sorbitol, aspartame, citric acid, sodium citrate, sodium methyl paraben, flavor and color

The claim is directed to the dry product as supplied, but the concentrations are expressed by reference to the constituted suspension. This creates an important infringement issue: the dry granulation must be capable of producing the claimed post-constitution concentrations.

Claim 7 adds a container marked to be filled with purified water to a predetermined volume. Claims 8-14 then define commercial presentations, principally 450 mL, 240 mL and 120 mL fills.

Representative claim 8 presentation

Claim 8 covers a 450 mL presentation containing:

90,000 mg mycophenolate mofetil
450 mg xanthan gum
2,250 mg colloidal silicon dioxide
450 mg soy lecithin
247,500 mg sorbitol
225 mg aspartame
Berry flavor and specified color

The 90,000 mg active quantity divided by 450 mL equals 200 mg/mL. Claims 9-14 use the same basic 200 mg/mL active concentration but vary the sweetener, buffer, preservative, flavor and color system.

The container-marking limitation may be significant in an inducement or contributory-infringement analysis. A bulk powder that is not supplied with the claimed fill instruction may avoid literal infringement of claims 7-14, although other claims could still be implicated.

What does claim 15 protect?

Claim 15 covers a separate dry granulation or powder blend that produces a suspension containing:

Ingredient	Concentration after constitution
Mycophenolate mofetil	200 mg/mL
Sodium carboxymethylcellulose	20 mg/mL
Sorbitol	300 mg/mL
Sucrose	100 mg/mL
Pluronic F68	4 mg/mL
Potassium sorbate	5 mg/mL
Cherry flavor	10 mg/mL
Color	0.01 mg/mL

Claims 16 and 17 add the marked container and a 450 mL presentation. Claim 17 therefore requires 90 g of mycophenolate mofetil, 9 g of sodium carboxymethylcellulose, 135 g of sorbitol and 45 g of sucrose in the specified container.

Claim 15 is compositionally distinct from claims 6-14. A product using sodium carboxymethylcellulose and Pluronic F68 but omitting xanthan gum and colloidal silicon dioxide would be assessed principally against claim 15, not claim 6.

What process steps are covered by claims 5 and 18?

Claim 5 addresses liquid suspension manufacturing. It covers formulations containing mycophenolate mofetil or mycophenolic acid at 7.5%-30.0% and requires a defined sequence involving:

Addition of antimicrobial agent to heated water.
Addition of suspending or viscosity agents.
Dissolution of buffers.
Addition of sweeteners, wetting agents, dyes, flavor enhancers and flavors.
Addition and mixing of the active compound.

The alternative process sequence separates preservative and suspending-agent processing from active-compound dispersion and later combines the mixtures.

Claim 18 addresses dry granulation or powder blending. Its wet-granulation route requires:

Combining active compound, sweeteners, wetting agents, suspending agents, flavors and antimicrobial agents.
Dissolving dyes and buffers in water.
Granulating the dry ingredients with the aqueous solution.
Drying and milling the granulation.
Adding further suspending or viscosity agent by blending.

The alternative route covers a powder blend formed without the same wet-granulation sequence.

Process infringement requires proof that the accused manufacturer performs the claimed steps, or directs or controls their performance. A finished product may infringe composition claims even if the manufacturing process differs.

When did U.S. Patent 5,688,529 expire?

U.S. Patent 5,688,529 issued on November 18, 1997. The relevant term is generally measured from the earliest effective nonprovisional filing date under the post-Uruguay Round patent-term statute, subject to patent-term adjustment, terminal disclaimers and other statutory adjustments [1].

Public patent records identify a March 4, 1994 priority date for the formulation disclosure. On that basis, the ordinary patent term would have ended in 2014, subject to any adjustment. The patent is no longer a live barrier to generic formulation entry.

Patent expiration is separate from FDA regulatory exclusivity. Any pediatric exclusivity associated with CellCept would have been a six-month regulatory extension and would not revive the underlying patent after expiration [2].

What is the Orange Book status of U.S. Patent 5,688,529?

The relevant FDA product is CellCept, whose active ingredient is mycophenolate mofetil. CellCept has been marketed in tablets, capsules, oral suspension and intravenous dosage forms. The oral suspension is the dosage form most closely associated with the subject matter of Patent 5,688,529 [3].

An Orange Book listing, if present for the reference product and dosage form, would have been relevant to an ANDA applicant through the Paragraph IV certification process before patent expiration. The listing itself would not extend patent life or create protection for formulations outside the listed scope.

The practical present-day position is:

Issue	Assessment
Patent status	Expired
Remaining patent exclusivity	None under Patent 5,688,529
Paragraph IV relevance	Historical before expiration
Current ANDA blocking effect	None from this patent
Biosimilar relevance	None; mycophenolate mofetil is a small molecule
Formulation design relevance	High as prior art and freedom-to-operate reference
Litigation value	Primarily historical or relevant to legacy sales periods

Which companies challenged or competed with CellCept?

Generic competition has involved manufacturers of mycophenolate mofetil tablets, capsules and oral suspensions. Relevant commercial participants have included Teva, Sandoz, Mylan/Viatris, Dr. Reddy’s, Accord and other ANDA sponsors, depending on dosage form and market period.

Paragraph IV litigation must be analyzed by product, dosage form, patent and filing date. A Paragraph IV challenge to a tablet or capsule patent does not necessarily establish a challenge to the oral-suspension claims of Patent 5,688,529. The reverse is also true.

The commercial landscape also includes Myfortic, an enteric-coated mycophenolate sodium product marketed by Novartis. Myfortic is not a direct formulation copy of CellCept oral suspension. It uses a different active pharmaceutical ingredient and a different delivery system. It may compete clinically in transplant immunosuppression but does not automatically avoid or implicate claims directed to mycophenolate mofetil suspensions.

How strong was the patent estate for the CellCept oral suspension?

The patent was technically narrow in some respects and commercially useful in others.

Strengths

It addressed a finished dosage form needed by pediatric and dysphagic patients.
Claims 6-14 mapped closely to defined 200 mg/mL reconstitutable products.
The claims combined active concentration with excipient identity and dosage presentation.
The process claims created a second infringement theory independent of the finished composition.

Vulnerabilities

Many claims require exact or tightly bounded excipient concentrations.
Claims 2 and 4 depend on “consisting essentially of,” which can generate disputes over additional excipients.
Functional language such as “suitable” and “flavor enhancer/bitter maskant” may require specification-based construction.
Process claims are vulnerable where a competing manufacturer uses a different sequence.
The patent did not broadly cover every aqueous mycophenolate mofetil suspension.
The 20% wt/vol and 200 mg/mL concentration requirements leave design-around space.

Potential design-around strategies would include:

Using a different active concentration.
Replacing xanthan gum, hydroxypropylmethylcellulose or sodium carboxymethylcellulose.
Replacing lecithin or colloidal silicon dioxide.
Using a different preservative system.
Changing the dry-granulation sequence.
Supplying a constituted product rather than a marked container presentation.
Developing a suspension based on mycophenolate sodium instead of mycophenolate mofetil.

Whether any design-around is effective depends on claim construction, prosecution history, equivalents and the full patent family.

What manufacturing and intellectual-property barriers remain?

Patent 5,688,529 no longer creates a current exclusionary barrier. Manufacturing barriers remain practical rather than patent-based:

Achieving uniform redispersion after storage.
Controlling sedimentation and particle-size distribution.
Maintaining chemical and microbiological stability.
Masking the bitter taste of mycophenolate mofetil.
Preserving dose uniformity at 200 mg/mL.
Validating reconstitution volume and container markings.
Demonstrating compatibility with the final bottle, cap and measuring device.

A current entrant would need to review later formulation, process, packaging, excipient and manufacturing patents, as well as FDA-approved labeling and product-specific guidance. The expired patent remains important because its disclosure may qualify as prior art against later attempts to claim substantially similar excipient combinations or processing steps.

What generic launch scenarios applied to the patented formulation?

Before expiration, three launch routes were commercially relevant:

A Paragraph IV ANDA challenge directed to the listed oral-suspension patent.
A non-infringing formulation using different excipients or concentrations.
A post-expiration launch relying on ordinary ANDA approval without a live patent barrier.

After expiration, the third route became the principal legal pathway. A generic could still face regulatory requirements relating to bioequivalence, pharmaceutical equivalence, stability, microbiological quality and labeling. Those requirements do not restore exclusivity to the patent owner.

Key Takeaways

Patent 5,688,529 covers liquid and reconstitutable oral suspensions of mycophenolate mofetil, not the active molecule itself.
Claims 1-4 focus on 20% wt/vol liquid suspensions with specified viscosity, sweetener, buffer and flavor systems.
Claims 6-17 focus on dry granulations or powder blends reconstituted to approximately 200 mg/mL.
Claims 5 and 18 cover alternative liquid and dry-granulation manufacturing processes.
Claims 8-14 and 17 correspond to marked commercial containers, principally 450 mL presentations.
The patent’s ordinary term expired in or around 2014, subject to any applicable term adjustment.
It provides no current patent exclusivity against generic mycophenolate mofetil oral suspension products.
Mycophenolate mofetil is a small molecule, so biosimilar analysis does not apply.
Myfortic is a competing mycophenolate product but uses mycophenolate sodium and a different dosage-form technology.
The patent remains relevant for historical litigation, prior-art analysis, formulation design and freedom-to-operate reviews.

FAQs

Does Patent 5,688,529 cover CellCept tablets?

No. The claims are directed principally to oral suspensions, reconstitutable powders and their manufacturing processes. Tablet and capsule protection would require separate composition, formulation or product patents.

Does a 100 mg/mL suspension infringe the patent?

Not literally under claims requiring 20% wt/vol or 200 mg/mL. Infringement could still require review of other claims and the doctrine of equivalents, but the concentration difference is a central design-around issue.

Can a generic use xanthan gum after Patent 5,688,529 expires?

Yes. The expired patent does not prevent use of xanthan gum. A current product must still be screened against later patents and regulatory requirements.

Does the container-marking language cover every bottle of reconstitutable powder?

No. Claims 7-14 and 16-17 require a container marked to be filled with purified water to a predetermined volume. Products without that claimed presentation may avoid those specific claims, although claims 6 or 15 may remain relevant.

Is mycophenolate sodium a biosimilar alternative to mycophenolate mofetil?

No. Mycophenolate sodium is a different small-molecule active ingredient and is regulated through small-molecule drug pathways rather than the FDA biosimilar pathway.

References

United States Patent and Trademark Office. (1997). U.S. Patent No. 5,688,529, Pharmaceutical formulations containing mycophenolate mofetil.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations, commonly known as the Orange Book.
U.S. Food and Drug Administration. (2023). CellCept (mycophenolate mofetil) prescribing information. Genentech USA, Inc.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	214572	⤷ Start Trial
Austria	303143	⤷ Start Trial
Australia	678303	⤷ Start Trial
Australia	7920594	⤷ Start Trial
Brazil	1100476	⤷ Start Trial
Brazil	9407728	⤷ Start Trial
Canada	2172506	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,688,529

Summary for Patent: 5,688,529