List of Excipients in Branded Drug REZLIDHIA

Company	Tradename	Ingredient	NDC	Excipient	Potential Generic Entry
Rigel Pharmaceuticals Inc	REZLIDHIA	olutasidenib	71332-005	CELLULOSE, MICROCRYSTALLINE	2039-05-16
Rigel Pharmaceuticals Inc	REZLIDHIA	olutasidenib	71332-005	CROSCARMELLOSE SODIUM	2039-05-16
Rigel Pharmaceuticals Inc	REZLIDHIA	olutasidenib	71332-005	FERROSOFERRIC OXIDE	2039-05-16

# REZLIDHIA Excipient Strategy and Commercial Opportunities for Olutasidenib

Last updated: September 3, 2026

REZLIDHIA is an oral, small-molecule IDH1 inhibitor approved for adults with relapsed or refractory acute myeloid leukemia (AML) harboring a susceptible IDH1 mutation. Its commercial formulation is a 150 mg immediate-release hard capsule taken twice daily on an empty stomach. The main excipient opportunities are generic-development support, capsule and powder-flow optimization, food-effect control, dose-flexibility platforms, and potential liquid or multiparticulate formulations. The strongest near-term opportunity is supply and technical support for an ANDA-ready capsule that reproduces the reference product’s dissolution and fasting-use profile.

What is REZLIDHIA and how is it used?

REZLIDHIA contains olutasidenib, an oral inhibitor of mutant IDH1. The FDA approved it on December 1, 2022, for adults with relapsed or refractory AML with a susceptible IDH1 mutation identified by an FDA-approved test.[1]

The labeled dose is 150 mg orally twice daily until disease progression or unacceptable toxicity. Patients must take the capsules on an empty stomach, defined in the prescribing information as at least one hour before or two hours after food.[2]

Attribute	REZLIDHIA
Active ingredient	Olutasidenib
Therapeutic area	Relapsed or refractory AML
Molecular target	Mutant IDH1
Dosage form	Immediate-release hard capsule
Strength	150 mg
Route	Oral
Dosing	150 mg twice daily
Food instruction	Empty stomach
Original NDA holder	Forma Therapeutics, now within Novo Nordisk
FDA approval	December 1, 2022
Orphan-drug exclusivity	Expected to run through December 1, 2029, absent loss or termination of exclusivity
Key regulatory pathway	Full NDA approval under section 505(b)(1)

The fasting requirement is commercially relevant. It increases the importance of excipient selection, dissolution reproducibility, capsule disintegration, and control of formulation-related variability.

What excipients are used in REZLIDHIA capsules?

The FDA labeling identifies an immediate-release capsule containing conventional solid-dose excipients. Public labeling identifies the following inactive ingredients:

• Colloidal silicon dioxide
• Croscarmellose sodium
• Hypromellose
• Magnesium stearate
• Microcrystalline cellulose
• Sodium lauryl sulfate
• Gelatin capsule shell components
• Titanium dioxide
• FD&C Blue No. 1, as applicable to the capsule shell

The exact supplier, grade, particle-size distribution, surface treatment, and manufacturing process are not disclosed in the public label. Those attributes can materially affect dissolution, blend uniformity, capsule fill weight, and scale-up performance.

Excipient function	Likely role in the REZLIDHIA capsule	Commercial relevance
Microcrystalline cellulose	Diluent and capsule-fill matrix	High-volume, substitution-sensitive component
Croscarmellose sodium	Superdisintegrant	Affects capsule opening and early dissolution
Colloidal silicon dioxide	Glidant and moisture-flow aid	Controls powder flow and fill consistency
Magnesium stearate	Lubricant	Excessive levels or blending time can slow dissolution
Sodium lauryl sulfate	Wetting or solubilization aid	Relevant to dissolution of a poorly wetting drug substance
Hypromellose	Processing or functional excipient	May support formulation robustness and powder handling
Gelatin	Capsule shell	Creates supply, color, and animal-origin considerations
Titanium dioxide and colorants	Capsule identification	Relevant to global regulatory and reformulation planning

An ANDA sponsor would not need to duplicate every supplier or grade. It would need to demonstrate pharmaceutical equivalence and bioequivalence while controlling critical quality attributes. Excipient substitution becomes higher risk if it changes wetting, powder hydrophobicity, capsule rupture, or the dissolution profile under fasting-relevant conditions.

Why is the food-effect requirement important for excipient strategy?

The empty-stomach instruction indicates that systemic exposure can be affected by food. The label reports clinically meaningful food-effect considerations and directs patients to avoid food around administration.[2] This creates three formulation priorities.

Dissolution under low-volume conditions

A capsule intended for fasting administration must release olutasidenib consistently without relying on fed-state bile salts or increased gastrointestinal fluid volume. Wetting agents, disintegrants, particle engineering, and lubricant control are therefore central to development.

Robustness against manufacturing variation

Changes in magnesium stearate concentration, blending time, silica grade, or croscarmellose particle size can alter dissolution. A generic formulation should establish a design space around:

• Blend uniformity
• Lubrication time
• Capsule fill weight
• Disintegration time
• Dissolution at multiple pH values
• Water activity and moisture exposure
• Drug-substance particle-size distribution

Potential reformulation value

A formulation that reduces or eliminates the fasting requirement could create a differentiated product, but this would require clinical food-effect evidence and regulatory support. A new excipient system alone would not establish equivalent exposure under fed conditions.

What formulation opportunities exist for olutasidenib?

Generic immediate-release capsules

The most practical opportunity is a 150 mg capsule that matches the reference product. The development program would likely focus on:

1. A comparable capsule shell and fill composition.
2. Rapid and reproducible disintegration.
3. Dissolution similarity across relevant pH conditions.
4. Bioequivalence under the FDA-recommended fasting condition.
5. Acceptable impurity and degradation profiles.

A generic sponsor could evaluate direct-compression and dry-granulation approaches. Wet granulation may improve content uniformity or flow but introduces moisture and process complexity that could affect chemical stability.

Low-dose or dose-flexible presentations

The approved product is supplied as a 150 mg capsule. A lower-strength capsule could support dose reduction for toxicity management, renal or hepatic impairment strategies, or clinical development. Its commercial value would depend on whether the FDA label, clinical practice, and payer behavior support routine dose modification.

Multiparticulate or sprinkle formulations

A multiparticulate capsule or coated-pellet system could support swallowing-impaired patients. This is a secondary opportunity because AML treatment is primarily an adult oncology market and the current product is already a capsule. Such a product would require data on dose recovery, stability after opening, administration through feeding systems, and exposure equivalence.

Oral liquid formulations

A liquid formulation could address patients unable to swallow capsules, but it presents substantial development risk. Olutasidenib’s aqueous solubility, chemical stability, taste, preservative compatibility, container adsorption, and food-effect behavior would need to be resolved. The market is likely smaller than the capsule market unless the formulation captures a clinically important underserved population.

Alternative solubilization systems

Self-emulsifying systems, lipid-based formulations, amorphous solid dispersions, or polymer-assisted systems could be evaluated if dissolution or exposure is limiting. These technologies are more commercially defensible when they provide a measurable advantage, such as reduced food dependence, lower variability, or lower dose.

How strong is the excipient-based competitive position?

Excipient differentiation alone is unlikely to provide durable market exclusivity. Most inactive ingredients used in an immediate-release capsule are nonproprietary and replaceable. The commercial value is more likely to arise from technical performance, regulatory execution, and supply reliability.

Opportunity	Technical difficulty	Commercial attractiveness	Exclusivity potential
Standard 150 mg generic capsule	Moderate	High after loss of exclusivity	Low
Capsule with improved dissolution robustness	Moderate to high	Moderate to high	Moderate if patented
Lower-strength capsule	Moderate	Moderate	Low to moderate
Sprinkle or multiparticulate product	High	Niche	Moderate
Oral suspension	High	Niche	Moderate
Fed-state or food-independent formulation	High	Potentially high	High if clinically validated
Fixed-dose combination	Very high	Uncertain	High but clinically dependent

The best excipient strategy is not necessarily the most novel one. A conventional formulation with a defensible dissolution profile, qualified global suppliers, and a simple manufacturing process can outperform a technically complex formulation in the generic market.

When does REZLIDHIA lose exclusivity?

REZLIDHIA has orphan-drug exclusivity associated with its AML indication. The seven-year orphan period is generally calculated from FDA approval, placing the expected end date at December 1, 2029.[1,3]

The product may also have listed patents in the FDA Orange Book. Patent expiry can occur after orphan exclusivity and may delay commercial generic entry. Orange Book patent information should be reviewed for:

• Drug-substance claims
• Composition-of-matter claims
• Formulation claims
• Method-of-use claims
• Polymorph or solid-state claims
• Regulatory exclusivity and patent certification requirements

A precise generic-entry date cannot be inferred from orphan exclusivity alone. A Paragraph IV filer could challenge listed patents before their expiration, while a Paragraph III certification would defer launch until patent expiry. The relevant Orange Book entries, patent expiry dates, pediatric extensions, and any litigation settlements determine the practical entry window.[3]

What is the Orange Book and Paragraph IV status of REZLIDHIA?

The FDA Orange Book is the controlling public source for listed patents and exclusivity associated with an approved small-molecule drug. REZLIDHIA is an NDA product rather than a biologic, so biosimilar interchangeability rules do not apply. Any follow-on competition would generally proceed through an ANDA or, for a clinically differentiated formulation, a 505(b)(2) application.

A Paragraph IV certification would assert that a listed patent is invalid, unenforceable, or not infringed. If the reference sponsor brings a timely infringement action, FDA approval of the ANDA can be stayed for up to 30 months, subject to statutory exceptions.[4]

Public commercial analysis should distinguish:

• FDA approval of an ANDA from a tentative approval.
• Patent expiry from orphan-exclusivity expiry.
• A patent challenge from an actual launch.
• A settlement agreement from an enforceable right to market.
• An authorized generic from an independent ANDA generic.

No biosimilar risk applies because olutasidenib is a chemically synthesized small molecule.

What patent claims could affect excipient and formulation competition?

The main legal risks for an excipient-focused competitor are unlikely to arise from the excipients individually. They may arise from a claim covering the finished pharmaceutical composition or a specific method of treating IDH1-mutated AML.

Potentially relevant claim categories include:

Composition claims

A composition claim could cover olutasidenib with defined excipient classes, concentration ranges, dissolution characteristics, or particle-size parameters. A generic using a materially different formulation may avoid infringement, but it would still need to satisfy bioequivalence requirements.

Method-of-use claims

Method claims may cover treatment of relapsed or refractory AML with an IDH1 mutation. Such claims can create litigation exposure even where the active ingredient and formulation are otherwise unpatented.

Manufacturing claims

Claims directed to a particular synthesis route, crystalline form, impurity profile, or manufacturing intermediate can constrain drug-substance sourcing. An excipient supplier does not eliminate this risk because the finished-dose manufacturer still requires noninfringing olutasidenib API.

Regulatory exclusivity

Orphan exclusivity is independent of patent validity. A successful Paragraph IV challenge does not necessarily eliminate orphan exclusivity for the protected indication. The statutory scope of exclusivity and the proposed ANDA labeling would determine the FDA’s response.

Which companies are positioned in the REZLIDHIA commercial landscape?

Novo Nordisk controls the REZLIDHIA asset through its acquisition of Forma Therapeutics in 2022.[5] The competitive landscape includes:

• Novo Nordisk as the originator and commercial rights holder.
• API manufacturers with olutasidenib synthesis and impurity-control capabilities.
• Capsule manufacturers and contract development and manufacturing organizations.
• Excipient suppliers providing microcrystalline cellulose, superdisintegrants, glidants, lubricants, surfactants, and capsule shells.
• Future ANDA sponsors and authorized-generic partners.
• Competing AML therapies targeting IDH1, IDH2, FLT3, BCL-2, and other disease pathways.

The main clinical competitor is ivosidenib, another oral IDH1 inhibitor. Ivosidenib has broader approved use in certain AML, cholangiocarcinoma, and myelodysplastic-syndrome settings, while REZLIDHIA is positioned specifically in relapsed or refractory AML with susceptible IDH1 mutations.[6,7]

Product	Active ingredient	Target	Principal positioning
REZLIDHIA	Olutasidenib	Mutant IDH1	Relapsed or refractory AML
Tibsovo	Ivosidenib	Mutant IDH1	AML and other IDH1-mutated malignancies
Idhifa	Enasidenib	Mutant IDH2	Relapsed or refractory AML with IDH2 mutation
Venclexta combinations	Venetoclax	BCL-2	AML combinations and other hematologic cancers

What revenue exposure and launch scenarios matter?

REZLIDHIA’s commercial value depends on the relatively small IDH1-mutated relapsed/refractory AML population, treatment duration, physician adoption, payer coverage, and competition from ivosidenib and salvage regimens. The product does not have the volume profile of a primary-care generic.

Three launch scenarios are commercially relevant:

Early challenge and settlement

An ANDA sponsor files before patent expiry, the reference company litigates, and the parties settle. The settlement could permit a licensed entry date, an authorized generic arrangement, or entry contingent on patent outcomes.

Post-exclusivity entry

Generic products launch after orphan exclusivity and any relevant patents expire. Price erosion may be slower than for high-volume chronic medicines because the population is specialized and distribution is concentrated.

Differentiated 505(b)(2) product

A sponsor launches a lower-strength, liquid, sprinkle, or food-independent formulation supported by new clinical data. This route could command a premium but would require a clear clinical or administration advantage.

What geographic coverage and manufacturing barriers apply?

The U.S. market is governed by FDA approval, Orange Book listings, orphan exclusivity, and ANDA litigation. European and other markets may have different patent families, supplementary protection certificates, pediatric extensions, data exclusivity periods, and regulatory requirements.

Manufacturing barriers include:

• Reliable olutasidenib API supply.
• Control of active-related impurities.
• Reproducible powder flow and capsule filling.
• Dissolution performance across commercial-scale batches.
• Stability under heat and humidity.
• Global acceptability of gelatin, titanium dioxide, colorants, and surfactants.
• Supplier qualification for critical excipients.
• Protection against single-source supply disruption.

A commercial formulation should use excipient grades with established pharmaceutical supply chains and documented change-control procedures. Substituting suppliers late in development can trigger comparability work and regulatory filing requirements.

Key Takeaways

• REZLIDHIA is a 150 mg immediate-release olutasidenib capsule for IDH1-mutated relapsed or refractory AML.
• The label requires twice-daily dosing on an empty stomach, making wetting, disintegration, lubrication, and dissolution control commercially important.
• The principal excipient opportunity is an ANDA-ready capsule with robust fasting-state performance.
• Liquid, sprinkle, lower-strength, and food-independent formulations are possible but require greater clinical and regulatory investment.
• Orphan-drug exclusivity is expected to extend through December 1, 2029, subject to statutory conditions.
• Patent expiry, Orange Book listings, Paragraph IV litigation, settlements, and labeling scope will determine actual generic-entry timing.
• Biosimilar competition is irrelevant because olutasidenib is a small molecule.
• Excipient patents alone are unlikely to create substantial barriers; formulation patents tied to dissolution, exposure, or food independence have greater strategic value.
• Supply security for olutasidenib API and critical excipients is a meaningful commercial differentiator.

FAQs about REZLIDHIA formulation and excipient opportunities

Can REZLIDHIA capsules be taken with food?

The prescribing information directs patients to take olutasidenib on an empty stomach, at least one hour before or two hours after food.[2]

Is REZLIDHIA eligible for a biosimilar?

No. Olutasidenib is a chemically synthesized small molecule. Follow-on products would generally use the ANDA pathway or, for differentiated formulations, the 505(b)(2) pathway.

What excipient is most likely to affect REZLIDHIA dissolution?

Magnesium stearate, sodium lauryl sulfate, croscarmellose sodium, and the microcrystalline-cellulose grade can each affect dissolution through lubrication, wetting, disintegration, or powder structure.

Could a generic manufacturer use different excipients from REZLIDHIA?

Yes. FDA generic approval does not normally require an identical inactive-ingredient composition. The proposed product must meet safety, pharmaceutical-equivalence, quality, labeling, and bioequivalence requirements.

Would a liquid olutasidenib product have meaningful commercial value?

Potentially, but the opportunity is niche. Its value would depend on demonstrating a clinically useful administration advantage for patients who cannot swallow capsules and resolving solubility, stability, taste, preservative, and food-effect issues.

References

1. U.S. Food and Drug Administration. (2022). FDA grants accelerated approval to olutasidenib for relapsed or refractory acute myeloid leukemia with a susceptible IDH1 mutation. https://www.fda.gov
2. U.S. Food and Drug Administration. (2023). REZLIDHIA (olutasidenib) prescribing information. Forma Therapeutics, Inc. https://www.accessdata.fda.gov
3. U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. https://www.accessdata.fda.gov/scripts/cder/ob/
4. U.S. Food and Drug Administration. (2024). Abbreviated new drug application process under the Hatch-Waxman Amendments. https://www.fda.gov
5. Novo Nordisk. (2022). Novo Nordisk completes acquisition of Forma Therapeutics. https://www.novonordisk.com
6. U.S. Food and Drug Administration. (2018). FDA approves ivosidenib for relapsed or refractory acute myeloid leukemia. https://www.fda.gov
7. U.S. Food and Drug Administration. (2022). TIBSOVO (ivosidenib) prescribing information. Servier Pharmaceuticals LLC. https://www.accessdata.fda.gov