List of Excipients in Branded Drug FYARRO

Company	Tradename	Ingredient	NDC	Excipient	Potential Generic Entry
Aadi Bioscience	FYARRO	sirolimus	80803-153	ALBUMIN HUMAN

Last updated: August 9, 2026

FYARRO’s commercial differentiation depends on its albumin-bound nanoparticle formulation, not on sirolimus alone. The excipient strategy removes conventional solvents and surfactants while creating a complex drug-delivery system that is difficult to copy with a simple generic tablet or injectable. The main commercial opportunities are formulation licensing, albumin and nanoparticle manufacturing, lifecycle extensions, and development of related sirolimus delivery products. The principal barriers are albumin supply, particle-characterization requirements, process reproducibility, and regulatory comparability.

FYARRO Excipient Strategy and Commercial Opportunities

What is FYARRO and how does its formulation work?

FYARRO is an intravenous formulation of sirolimus protein-bound particles approved by the FDA for adults with locally advanced unresectable or metastatic malignant perivascular epithelioid cell tumor, or PEComa [1].

The product is supplied as a sterile, lyophilized powder in single-dose vials. Each vial contains:

Component	Amount per vial	Functional role
Sirolimus	100 mg	Active pharmaceutical ingredient
Human albumin	200 mg	Carrier and formulation excipient
Conventional surfactant or organic solvent	Not listed in the U.S. label	Not required in the marketed formulation

After reconstitution, FYARRO is administered as an intravenous infusion at 100 mg/m² over approximately 30 minutes once every 21 days [1].

The formulation uses albumin-bound particles to create a nanoscale delivery system for the highly lipophilic sirolimus molecule. Albumin is more than a passive bulking agent. It contributes to drug dispersion, particle formation, physical stability, and delivery characteristics.

What excipients protect FYARRO?

Human albumin is the central excipient and the primary formulation differentiator. The FDA prescribing information identifies albumin human as the inactive ingredient in FYARRO [1].

Why albumin is commercially important

Albumin can perform several formulation functions:

• Improve dispersion of poorly water-soluble sirolimus.
• Support formation of protein-bound nanoparticles.
• Avoid or reduce the need for synthetic surfactants.
• Avoid the use of ethanol, propylene glycol, or other solubilizing solvents commonly used in injectable formulations.
• Permit a lyophilized presentation with reconstitution before infusion.
• Influence particle size, surface properties, drug loading, and release behavior.

The product is therefore better characterized as a drug-device-like delivery platform within a drug product than as a conventional excipient-based injectable.

The albumin source also creates supply-chain and quality requirements. Human albumin must meet donor-screening, viral-safety, manufacturing, and release specifications. Changes in albumin supplier, grade, purification process, or viral-clearance process can affect product comparability.

How does FYARRO compare with conventional sirolimus products?

FYARRO differs materially from oral sirolimus products such as RAPAMUNE.

Attribute	FYARRO	Conventional oral sirolimus
Active ingredient	Sirolimus	Sirolimus
Route	Intravenous	Oral
Delivery system	Albumin-bound nanoparticles	Tablet or oral solution
Key excipient strategy	Human albumin carrier	Solubilizers, polymers, fillers, coatings, or oral vehicle
Primary formulation challenge	Particle formation and protein-drug interaction	Solubility, dissolution, absorption, and stability
Clinical setting	Oncology infusion	Immunosuppression
Copying pathway	Complex injectable formulation	Conventional generic or 505(b)(2) pathway
Commercial differentiation	Delivery system and oncology indication	Established active ingredient and oral dosage form

A conventional sirolimus generic would not automatically substitute for FYARRO. The different route, dosage form, excipient system, particle attributes, and clinical use create a substantial product-development gap.

What formulation patents and intellectual-property rights protect FYARRO?

FYARRO’s defensibility is likely concentrated in formulation, particle engineering, manufacturing, and oncology use claims rather than in basic sirolimus composition-of-matter rights. Sirolimus was discovered and commercialized decades before FYARRO, so the active ingredient itself does not provide modern exclusivity.

Relevant protection categories include:

1. Albumin-bound sirolimus particles.
2. Particle-size and drug-loading specifications.
3. Lyophilized injectable compositions.
4. Reconstitution and infusion methods.
5. Manufacturing processes for drug-loaded albumin nanoparticles.
6. Treatment of PEComa and other tumors with protein-bound sirolimus.
7. Quality-control methods for particle size, aggregation, residual moisture, and release.

The enforceability of this estate depends on claim scope and the degree to which a competing product must reproduce the protected particle structure. Broad claims covering the active ingredient and albumin combination are commercially valuable. Narrow claims limited to specific particle sizes, process conditions, or ratios may be easier to design around but can still delay market entry if the product must meet demanding clinical and CMC requirements.

Patent and regulatory distinction

A patent claim and an FDA substitutability determination address different issues. A competitor can avoid literal infringement and still face regulatory difficulty demonstrating that its product has the same pharmaceutical quality and clinical performance. Conversely, a formulation can be scientifically similar without infringing a particular process or composition claim.

What is the FDA exclusivity status of FYARRO?

FYARRO received FDA approval on November 22, 2021, for malignant PEComa [1]. It received orphan-drug designation for the approved indication, creating seven years of orphan-drug exclusivity in the United States, subject to the statutory exceptions in the Orphan Drug Act.

The principal U.S. exclusivity timeline is:

Milestone	Date or period
FDA approval	November 22, 2021
Orphan-drug exclusivity	Generally through November 22, 2028
New chemical entity exclusivity	Not expected because sirolimus is an established active ingredient
Pediatric exclusivity	No extension should be assumed without a qualifying FDA grant
Patent expiry	Must be assessed patent by patent and is separate from orphan exclusivity

Orphan exclusivity blocks FDA approval of another product for the same orphan indication that contains the same active moiety, unless an exception applies. It does not block every sirolimus product, every albumin-bound product, or every oncology use of sirolimus.

How difficult would a generic or 505(b)(2) FYARRO competitor be?

A conventional ANDA strategy may be difficult because FYARRO is a complex injectable formulation. The development program would need to address more than active-ingredient identity.

Key comparison attributes would include:

• Sirolimus content and potency.
• Albumin source and quality.
• Particle-size distribution.
• Drug-to-albumin ratio.
• Free versus protein-bound sirolimus.
• Reconstitution time.
• Visible and subvisible particles.
• Aggregation and precipitation.
• Residual moisture after lyophilization.
• Infusion stability.
• Release profile.
• Sterility and endotoxin control.
• Container-closure compatibility.

A 505(b)(2) application may offer more flexibility where the sponsor relies partly on FDA findings for sirolimus or an established product while providing new data for the albumin-bound formulation. The pathway would not eliminate the need to establish product quality, clinical relevance, and any required bridging studies.

The commercial hurdle is also high. Malignant PEComa is a rare cancer, and the addressable patient population is much smaller than the population for conventional sirolimus. A competitor would need to balance development costs against limited volume and the remaining period of orphan exclusivity.

What manufacturing and excipient barriers affect FYARRO competition?

The main manufacturing barrier is control of the albumin-sirolimus nanoparticle process.

Albumin sourcing

Human albumin creates exposure to:

• Supplier concentration.
• Batch-to-batch variability.
• Human-plasma procurement constraints.
• Viral and adventitious-agent controls.
• Changes in albumin purity or excipient profile.
• Long-term supply agreements and minimum purchase commitments.

A competing sponsor may need to qualify a separate albumin source or develop a process that tolerates supplier variability without changing particle characteristics.

Nanoparticle process control

The process may involve high-energy mixing, homogenization, solvent handling, filtration, concentration, and lyophilization. Each step can affect particle size and drug distribution. Small process changes can change infusion behavior or in vivo exposure.

Critical process parameters may include:

• Mixing intensity.
• Homogenization pressure.
• Temperature.
• Feed concentration.
• Albumin concentration.
• Sirolimus loading.
• Solvent-removal conditions.
• Sterile filtration limits.
• Freeze-drying cycle parameters.

These controls create a higher CMC burden than a standard aqueous injectable.

Fill-finish requirements

The product requires sterile vial filling, lyophilization, reconstitution instructions, and compatibility validation. Commercial scale-up must preserve the same particle characteristics measured in clinical material.

What commercial opportunities exist for FYARRO excipients and delivery technology?

Albumin supply and manufacturing partnerships

Albumin manufacturers can pursue long-term supply agreements with oncology drug developers. The most valuable suppliers will offer consistent pharmaceutical-grade albumin, strong regulatory documentation, and capacity for clinical and commercial scale.

Contract development and manufacturing

CDMOs with expertise in nanoparticle production, sterile processing, and lyophilization can provide:

• Formulation development.
• Process scale-up.
• Analytical method development.
• Particle characterization.
• Aseptic fill-finish.
• Stability programs.
• Technology transfer.

The specialized CMC requirements support higher-value contracts than standard vial-filling work.

Follow-on sirolimus delivery products

Potential product concepts include:

• Subcutaneous albumin-bound sirolimus.
• Longer-acting injectable formulations.
• Lower-volume infusion presentations.
• Alternative nanoparticle carriers.
• Combination products with targeted oncology agents.
• Albumin-bound formulations for other rare tumors.
• Local or intratumoral delivery systems.
• Oral or inhaled nanocarrier products using related excipient technology.

Each opportunity would require careful assessment of whether it falls within FYARRO’s orphan indication, patent claims, or exclusivity scope.

Indication expansion

The mTOR pathway is relevant to several cancers and rare diseases. Expansion into additional indications could increase the value of the delivery platform, but the sponsor would need to evaluate:

• New clinical trial costs.
• Orphan designation opportunities.
• Dose differences between diseases.
• Combination-treatment safety.
• Potential overlap with existing sirolimus products.
• Patent term remaining for new methods of use.

Excipient substitution

A non-albumin carrier could create a separate product profile, but substitution would be technically and commercially difficult. Candidates could include synthetic polymers, phospholipid systems, cyclodextrins, or other nanoparticle carriers. The benefit would be reduced dependence on human plasma-derived material. The cost would be new toxicology, new process development, and potentially reduced clinical comparability.

Which companies are positioned to challenge FYARRO?

The most credible challengers would likely come from four groups:

1. Generic injectable manufacturers with complex-product capabilities.
2. Oncology companies developing mTOR inhibitors or targeted nanoparticles.
3. CDMOs with albumin-nanoparticle manufacturing platforms.
4. Specialty pharmaceutical companies seeking rare-cancer products.

Large generic companies may have the regulatory and manufacturing infrastructure but could view the PEComa market as too small. Specialty oncology companies may accept the smaller market because orphan pricing can support a focused commercial model.

A biosimilar challenge is not the expected pathway. FYARRO is a small-molecule sirolimus product, not a biologic. The relevant competitive pathways are an ANDA, a 505(b)(2) application, or a separate NDA for a differentiated delivery system.

What is the revenue exposure and market opportunity?

FYARRO’s commercial opportunity is defined by a rare indication, high oncology pricing, and potential use in additional tumors. The relevant revenue drivers are:

• Number of newly diagnosed and relapsed PEComa patients.
• Duration of treatment.
• Dose intensity based on body-surface area.
• Treatment discontinuation from toxicity or progression.
• Payer coverage and site-of-care economics.
• Expansion into other malignancies.
• Competition from future mTOR inhibitors or targeted therapies.

The rare-disease profile limits unit volume but can support premium pricing and specialist distribution. The product’s intravenous administration also creates infusion-center and hospital economics that differ from oral sirolimus.

How strong is the FYARRO patent and excipient estate?

FYARRO has a stronger technical barrier than a conventional repurposed sirolimus product because its value is tied to a specific drug-delivery architecture. The estate is strongest where patents cover:

• The albumin-bound nanoparticle itself.
• Narrow but commercially necessary particle attributes.
• Manufacturing steps that are difficult to avoid.
• Approved or commercially important oncology methods of use.

The estate is weaker where claims cover only broad concepts that competitors can reproduce with different albumin ratios, particle-size ranges, process conditions, or carrier materials.

The practical protection period is therefore the combined effect of orphan exclusivity, listed patents, regulatory complexity, clinical differentiation, and manufacturing know-how. No single protection mechanism determines the full competitive risk.

Key Takeaways

• FYARRO uses human albumin as its principal excipient and nanoparticle carrier.
• The formulation avoids the conventional solvent and surfactant strategy used for many poorly soluble drugs.
• The main technical barrier is reproducible manufacture of albumin-bound sirolimus particles.
• FYARRO is a complex injectable, so a simple sirolimus generic would not be an equivalent commercial substitute.
• FDA approval occurred on November 22, 2021, with orphan-drug exclusivity generally extending through November 22, 2028.
• The most attractive commercial opportunities are albumin supply, nanoparticle CDMO services, lifecycle extensions, and new sirolimus delivery systems.
• Biosimilar competition is not the relevant risk category because FYARRO is a small-molecule drug.
• Patent strength depends on the scope of formulation, process, particle-characteristic, and method-of-use claims.

FAQs About FYARRO Excipient and Commercial Strategy

Can FYARRO be reformulated without human albumin?

Yes, but a non-albumin reformulation would likely be a materially different product. It would require new formulation development, stability data, toxicology assessment, and regulatory bridging. The sponsor would also lose the albumin-based technical and commercial identity of FYARRO.

Does human albumin make FYARRO a biologic drug?

No. FYARRO contains a small-molecule active ingredient, sirolimus. Human albumin is a plasma-derived excipient and carrier, but its presence does not convert the product into a biologic for FDA classification purposes.

Could an albumin supplier become a strategic partner to a FYARRO competitor?

Yes. A qualified pharmaceutical-grade albumin supplier could provide a critical input, support regulatory filings, and reduce supply risk. A supplier with robust capacity, documented viral safety, and demonstrated consistency would have greater commercial value.

Is FYARRO interchangeable with RAPAMUNE?

No. Both contain sirolimus, but FYARRO is an intravenous albumin-bound nanoparticle product and RAPAMUNE is an oral formulation. They have different routes, dosage forms, pharmacokinetic considerations, clinical uses, and administration requirements.

Could FYARRO’s nanoparticle platform support drugs other than sirolimus?

Potentially. Albumin-bound nanoparticle technology may be adaptable to other poorly water-soluble compounds. Each new active ingredient would require separate assessment of loading, release, stability, toxicity, pharmacokinetics, and intellectual-property coverage.

References

1. U.S. Food and Drug Administration. (2021). FYARRO (sirolimus protein-bound particles for injectable suspension) prescribing information. FDA.

2. U.S. Food and Drug Administration. (2021). FYARRO approval announcement and regulatory materials. FDA.

3. U.S. Food and Drug Administration. (2023). Orange Book: Approved drug products with therapeutic equivalence evaluations. FDA.

4. U.S. Food and Drug Administration. (2024). Guidance for industry: ANDAs for certain highly purified synthetic peptides and complex drug products. FDA.

5. U.S. Food and Drug Administration. (2024). Guidance for industry: Drug products, including biological products, that contain nanomaterials. FDA.

6. National Institutes of Health. (2024). Clinical and regulatory information for malignant PEComa and sirolimus-based therapy. National Cancer Institute.