List of Excipients in Branded Drug HYLENEX RECOMBINANT

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Company	Tradename	Ingredient	NDC	Excipient	Potential Generic Entry
A-S Medication Solutions	HYLENEX RECOMBINANT	hyaluronidase (human recombinant)	50090-4534	ALBUMIN HUMAN
A-S Medication Solutions	HYLENEX RECOMBINANT	hyaluronidase (human recombinant)	50090-4534	HYDROCHLORIC ACID
A-S Medication Solutions	HYLENEX RECOMBINANT	hyaluronidase (human recombinant)	50090-4534	METHIONINE
A-S Medication Solutions	HYLENEX RECOMBINANT	hyaluronidase (human recombinant)	50090-4534	POLYSORBATE 80
A-S Medication Solutions	HYLENEX RECOMBINANT	hyaluronidase (human recombinant)	50090-4534	SODIUM CHLORIDE

HYLENEX Recombinant Excipient Strategy, Formulation Economics, Patents, and Commercial Opportunities

Last updated: September 27, 2026

HYLENEX Recombinant is a recombinant human hyaluronidase product containing 150 USP units/mL of rHuPH20. Its commercial value is based on transiently increasing subcutaneous tissue permeability, allowing larger-volume or more rapid subcutaneous administration of selected injectable drugs and fluids. The product’s excipient strategy prioritizes protein stability, isotonicity, pH control, calcium management, and low immunogenicity rather than conventional small-molecule solubilization.

HYLENEX is marketed by Halozyme Therapeutics and is approved in the United States as an adjunct to increase the absorption and dispersion of other injected drugs and fluids. It is a biologic product, so its regulatory and patent position differs from an Orange Book-listed small-molecule drug.

What is HYLENEX Recombinant?

HYLENEX Recombinant is a sterile, preservative-free solution of recombinant human hyaluronidase PH20, or rHuPH20. The enzyme temporarily hydrolyzes hyaluronan in the extracellular matrix of subcutaneous tissue. This creates a short-lived increase in tissue permeability and improves dispersion of co-administered subcutaneous products.

Attribute	HYLENEX Recombinant
Active ingredient	Recombinant human hyaluronidase PH20
Strength	150 USP units/mL
Dosage form	Sterile injectable solution
Route	Subcutaneous administration
Product type	Biologic enzyme
Sponsor	Halozyme Therapeutics
U.S. approval	FDA-approved biologic product
Primary use	Facilitates absorption and dispersion of injected drugs and fluids
Preservatives	None in the single-dose presentation
Commercial role	Standalone hyaluronidase and enabling component for subcutaneous delivery

The product is not itself a conventional excipient in the formulation sense. It is an active biologic adjunct administered with another drug. In the broader drug-delivery market, however, rHuPH20 functions as a delivery-enabling excipient or formulation component.

What excipients are used in HYLENEX Recombinant?

HYLENEX contains a relatively simple aqueous formulation. The labeled inactive ingredients are sodium chloride, dibasic sodium phosphate, calcium chloride dihydrate, and human albumin. The formulation has a near-neutral pH and is supplied as a single-dose injectable solution.

Formulation component	Function in the formulation
Sodium chloride	Isotonicity and control of osmolality
Dibasic sodium phosphate	Buffering and pH control
Calcium chloride dihydrate	Supports formulation conditions relevant to enzyme stability
Human albumin	Protein stabilizer and surface-protection agent
Water for injection	Vehicle

The precise qualitative and quantitative composition should be confirmed against the current FDA-approved prescribing information and manufacturing specifications before use in a regulatory filing. The FDA label identifies the formulation ingredients and directs administration through the subcutaneous route. (U.S. Food and Drug Administration [FDA], 2023)

Why does HYLENEX use human albumin?

Human albumin can reduce adsorption of a low-concentration protein to vial, syringe, and administration-surface materials. It can also reduce interfacial stress during storage and handling. For rHuPH20, albumin is commercially relevant because protein aggregation, surface adsorption, and activity loss can affect delivered enzyme dose.

Albumin creates tradeoffs:

• It introduces a human-derived raw material into the manufacturing process.
• It requires control of viral safety, sourcing, and supply continuity.
• It can complicate development of animal-origin-free or fully synthetic formulations.
• It may limit compatibility with certain co-formulation strategies.
• It can affect regional regulatory review and customer preferences.

A future albumin-free HYLENEX formulation could reduce raw-material and supply-chain complexity if it matches the reference product for activity, stability, particulate profile, container compatibility, and immunogenicity risk.

How does the HYLENEX excipient strategy support product performance?

The formulation has four primary technical objectives.

Protein stability

rHuPH20 is a glycoprotein enzyme that requires control of pH, ionic strength, temperature, agitation, and interfaces. Albumin provides surface protection, while the aqueous buffer system limits pH drift during storage.

Enzyme activity

The commercial product must maintain hyaluronidase activity through filling, transport, storage, and administration. Activity is measured in USP units rather than only by protein concentration. This distinction matters because a biosimilar or follow-on product could match protein content while failing to match functional activity.

Injection compatibility

HYLENEX is administered subcutaneously with another injectable product. Its formulation must avoid unacceptable precipitation, turbidity, pH shifts, or activity loss when used in proximity to the co-administered drug.

The label places responsibility on the user to evaluate compatibility with the drug or fluid being administered. HYLENEX is not a universal compatibility enhancer. High-concentration antibodies, highly acidic or alkaline products, surfactant-rich formulations, and products with sensitive aggregation profiles may require separate compatibility studies.

Temporary tissue permeability

The delivery effect depends on enzymatic degradation of hyaluronan in the extracellular matrix. The effect is transient, which permits later restoration of tissue structure. This supports use in subcutaneous delivery without requiring a permanent change to tissue permeability.

What formulation patents protect HYLENEX and rHuPH20?

Protection for HYLENEX is distributed across biologic composition, recombinant production, purification, formulation, delivery-platform, and combination-product patent families. The commercial relevance of each family depends on claim scope, expiration, terminal disclaimers, patent-term adjustment, continuations, and jurisdiction.

Protection category	Typical claim subject matter	Commercial relevance
Composition of matter	Recombinant PH20 variants, sequences, glycosylation characteristics	Controls manufacture of the enzyme
Production	Host cells, expression constructs, fermentation, purification	Creates manufacturing barriers
Formulation	Stabilized aqueous protein compositions	Protects liquid injectable presentations
Delivery method	Use of hyaluronidase to facilitate subcutaneous administration	Protects clinical use
Co-formulation	rHuPH20 combined with a therapeutic antibody or other biologic	Protects fixed-dose products
Device and administration	Syringe, cartridge, infusion, or injection configurations	Supports differentiated delivery systems
Platform use	ENHANZE-enabled subcutaneous delivery	Supports licensing economics

Halozyme’s broader ENHANZE patent portfolio is strategically more important than the standalone HYLENEX label because it supports partnerships involving co-formulated or co-administered biologics. Patent protection can differ substantially between HYLENEX, a standalone vial, and a partner’s fixed-dose subcutaneous product.

Does HYLENEX have Orange Book patents?

No conventional Orange Book analysis should be used as the primary framework for HYLENEX. The product is a biologic, and biologic products are generally tracked through the FDA’s Purple Book rather than through the small-molecule Orange Book patent-listing process. (FDA, 2024a; FDA, 2024b)

This distinction affects generic-entry analysis:

• A conventional ANDA pathway is not the normal route for a biologic such as HYLENEX.
• A biosimilar or interchangeable product would proceed under the Public Health Service Act framework.
• Patent disputes may involve the Biologics Price Competition and Innovation Act patent-exchange process rather than an automatic Paragraph IV notice under the Hatch-Waxman framework.
• Absence from the Orange Book does not mean absence of patent protection.

When does HYLENEX lose exclusivity?

HYLENEX does not have a single publicly determinative “patent expiration date” comparable to a conventional Orange Book small molecule. Exclusivity analysis requires separating FDA regulatory exclusivity from patent protection.

Exclusivity layer	Relevance to HYLENEX
Biologic reference-product exclusivity	Limits timing of a biosimilar application and approval
Orphan exclusivity	Not the principal commercial framework for HYLENEX
Composition patents	May protect rHuPH20 or related molecules
Manufacturing patents	May constrain production routes
Formulation patents	May protect specific stabilized liquid products
Method-of-use patents	May cover subcutaneous administration or specified combinations
Partner-product patents	May protect combination biologics using rHuPH20

The reference-product exclusivity period for a biologic is generally 12 years from first licensure, subject to statutory rules and the product’s approval history. Patent expiry may occur later or earlier for individual claim sets. A biosimilar applicant can challenge relevant patents even when some formulation or manufacturing patents remain in force.

Are there Paragraph IV challenges to HYLENEX?

A Paragraph IV challenge is not the expected primary pathway for HYLENEX because it is a biologic rather than a conventional small-molecule drug. A competing developer would more likely pursue a biosimilar route, a separate biologic license application, or a non-identical hyaluronidase product.

The relevant competitive questions are:

1. Whether the competitor’s product is sufficiently similar to rHuPH20.
2. Whether it uses the same or a different hyaluronidase sequence.
3. Whether it has comparable enzymatic activity and pharmacology.
4. Whether the competitor can support the proposed route and indication.
5. Whether Halozyme patents cover the competitor’s molecule, production method, formulation, or use.
6. Whether the competitor can obtain adequate reference-product information.

A non-rHuPH20 hyaluronidase may avoid some composition claims but face separate clinical, immunogenicity, activity, and regulatory hurdles.

What commercial opportunities exist for HYLENEX excipients?

The largest opportunities are not replacement sales for sodium chloride or phosphate. Those ingredients are commodity inputs. The higher-value opportunities concern formulation redesign, supply assurance, and use of rHuPH20 as a delivery-enabling component.

Albumin-free formulation development

A synthetic stabilizer system could eliminate dependence on human albumin. Candidate strategies may include combinations of nonionic surfactants, amino acids, sugars, polyols, and polymeric stabilizers. Any replacement must preserve:

• Enzyme activity
• Low aggregation
• Low subvisible particle formation
• Container closure compatibility
• Sterility and endotoxin performance
• Subcutaneous tolerability
• Long-term refrigerated stability
• Compatibility with co-administered products

An albumin-free presentation could have value in markets where animal- or human-derived excipients create procurement or regulatory friction.

Ready-to-use delivery kits

HYLENEX can be incorporated into commercial administration kits containing:

• The hyaluronidase vial or prefilled syringe
• A compatible co-administered drug
• Administration instructions
• Needles or transfer components
• Stability-controlled packaging

The commercial opportunity is strongest where a hospital or home-care provider currently performs multiple preparation steps. A kit could reduce preparation time and administration errors, although combination-product and labeling requirements would apply.

Co-packaged biologic delivery

Standalone HYLENEX can support subcutaneous administration of products that are otherwise intravenous or difficult to inject subcutaneously. The opportunity includes high-volume antibodies, immunoglobulins, enzymes, and other biologics.

The main commercial distinction is between:

• Co-administration, where HYLENEX and the therapeutic are supplied separately.
• Co-packaging, where the products are sold together but not mixed.
• Co-formulation, where both are present in a single container.
• Device-enabled delivery, where the system controls dosing and administration.

Co-formulation generally offers stronger differentiation but requires more extensive compatibility, stability, clinical, and regulatory work.

Biosimilar and follow-on delivery platforms

Biosimilar developers may use hyaluronidase to create subcutaneous versions of products traditionally administered intravenously. This can improve administration convenience and reduce infusion-center dependence.

Halozyme’s commercial position is stronger when the delivery technology is embedded in a partner product and protected by combination and use patents. A biosimilar developer seeking a non-Halozyme route would need to establish a separate delivery system, which may require additional clinical development.

How does HYLENEX compare with animal-derived hyaluronidase products?

Factor	HYLENEX Recombinant	Animal-derived hyaluronidase
Source	Recombinant human protein	Bovine or ovine tissue-derived enzyme
Immunogenicity profile	Designed to match human hyaluronidase more closely	Greater concern regarding non-human proteins
Supply model	Cell-culture manufacturing	Tissue sourcing and extraction
Regulatory positioning	Recombinant biologic	Animal-derived biologic
Excipient strategy	Human albumin-containing aqueous formulation	Product-specific formulation
Platform licensing	Strong association with ENHANZE	Limited platform relevance
Commercial use	Standalone and partner-enabled delivery	Primarily standalone clinical use

Animal-derived products can remain commercially relevant in selected markets, but rHuPH20 has stronger strategic value for chronic biologic delivery and partner co-formulations.

What manufacturing and IP barriers affect HYLENEX competition?

Manufacturing is a meaningful barrier because the product requires control of recombinant protein expression, glycosylation, purification, enzyme activity, and low-level impurities. The key technical risks include:

• Incorrect or heterogeneous glycosylation
• Loss of catalytic activity
• Aggregation during concentration or filling
• Host-cell protein and DNA impurities
• Proteolytic degradation
• Particulate formation
• Adsorption to process equipment
• Reduced stability after container or device transfer

A competitor may reproduce the active sequence but still face substantial analytical and clinical comparability work. Manufacturing patents can also create freedom-to-operate issues independent of composition patents.

What is the competitive landscape for subcutaneous biologic delivery?

The relevant competitors are not limited to hyaluronidase manufacturers. The competitive landscape includes:

• Other hyaluronidase products
• Large-volume subcutaneous infusion systems
• Wearable injectors
• On-body delivery devices
• High-concentration biologic formulations
• Slow-release depots
• Recombinant or engineered tissue-permeability enhancers
• Intravenous-to-subcutaneous reformulations

Halozyme’s advantage is the combination of an established enzyme, regulatory precedent, manufacturing experience, and a licensing platform. Device companies compete by avoiding enzymatic modification of tissue and by offering controlled, extended administration.

What revenue exposure does HYLENEX create for Halozyme?

HYLENEX revenue is strategically smaller than the potential value of Halozyme’s ENHANZE licensing and royalty portfolio. Standalone HYLENEX sales provide product revenue, while partnered products can generate milestone payments, royalties, and commercial participation.

The key revenue drivers are:

Driver	Impact
HYLENEX unit sales	Direct product revenue
Number of partner products	Expands royalty base
Partner product approvals	Converts development programs into commercial assets
Subcutaneous conversion of IV biologics	Increases addressable market
Label expansion	Supports new therapeutic uses
Patent life	Extends royalty and exclusivity duration
Manufacturing capacity	Limits or enables supply growth

Investment analysis should separate HYLENEX product revenue from ENHANZE economics. Treating the two as one revenue stream obscures the commercial contribution of partner programs.

What is the FDA regulatory status of HYLENEX?

HYLENEX is an FDA-approved recombinant human hyaluronidase product. The approved use is as an adjunct to increase the absorption and dispersion of other injected drugs and fluids. The label includes contraindications related to hypersensitivity and warnings concerning inappropriate use, infection spread, and incompatibility considerations. (FDA, 2023)

HYLENEX is not approved as a general-purpose excipient for any drug selected by a manufacturer. Each proposed combination or administration use requires an appropriate regulatory strategy, including compatibility, safety, pharmacokinetic, and clinical evidence where applicable.

Key Takeaways

• HYLENEX contains rHuPH20 at 150 USP units/mL in a sterile, preservative-free aqueous formulation.
• Its labeled inactive ingredients include sodium chloride, dibasic sodium phosphate, calcium chloride dihydrate, and human albumin.
• Albumin supports protein stability but creates sourcing, regulatory, and animal-origin-free formulation considerations.
• HYLENEX is a biologic and should be analyzed through Purple Book and biologic patent frameworks, not standard Orange Book assumptions.
• Paragraph IV is not the expected primary challenge pathway; biosimilar and separate-biologic strategies are more relevant.
• The strongest commercial opportunity is rHuPH20-enabled subcutaneous delivery of biologics, not commodity excipient substitution.
• Albumin-free formulations, ready-to-use kits, co-packaged biologics, and device-enabled administration are the main formulation and commercial opportunities.
• Manufacturing comparability, enzyme activity, glycosylation, aggregation control, and patent freedom to operate create substantial barriers to entry.
• Halozyme’s broader ENHANZE platform and partner royalties are commercially more significant than standalone HYLENEX sales.

FAQs About HYLENEX Recombinant Formulation and Commercial Strategy

Can HYLENEX be mixed in the same syringe with another drug?

Not automatically. Compatibility must be established for the specific drug, concentration, container, diluent, and administration conditions. The HYLENEX label does not create universal compatibility across injectable products.

Is HYLENEX an excipient or an active pharmaceutical ingredient?

HYLENEX is an active biologic enzyme product. In drug-delivery applications, rHuPH20 can function as an enabling excipient-like component because it modifies tissue permeability and facilitates administration of another therapeutic.

Can a company replace HYLENEX with bovine hyaluronidase?

A bovine product may provide a different regulatory and clinical pathway but is not automatically interchangeable with rHuPH20. Sequence, glycosylation, immunogenicity, potency, impurity profile, and clinical performance must be evaluated.

Is an albumin-free HYLENEX formulation commercially attractive?

Yes. An albumin-free formulation could reduce dependence on human-derived raw materials and simplify supply management. It would need to demonstrate equivalent activity, stability, tolerability, and container compatibility.

Are HYLENEX and ENHANZE the same product?

No. HYLENEX is a marketed rHuPH20 product administered as an adjunct. ENHANZE is Halozyme’s broader delivery platform, which uses rHuPH20 technology in partner-specific subcutaneous delivery programs and co-formulations.

References

1. Halozyme Therapeutics, Inc. (2024). Annual report pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934. U.S. Securities and Exchange Commission.

2. U.S. Food and Drug Administration. (2023). HYLENEX recombinant prescribing information. FDA.

3. U.S. Food and Drug Administration. (2024a). Purple Book: Database of licensed biological products. FDA.

4. U.S. Food and Drug Administration. (2024b). Approved drug products with therapeutic equivalence evaluations. FDA.

5. U.S. Food and Drug Administration. (2020). Questions and answers on biosimilar development and the BPCI Act. FDA.

6. United States Pharmacopeia. (2024). Hyaluronidase monograph and USP biological activity standards. USP.