IngredientsHyaluronidase (HAase) is a family of enzymes critical for regulating physiological and pathological states that catalyzes the degradation of hyaluronic acid (HA), a key component of the extracellular matrix (ECM). The systematic biochemical name is hyaluronate 4-glycanohydrolase (EC 3.2.1.35 for the hydrolytic type). Hyaluronidase is a glycosidase that can degrade the glycosidic bonds in hyaluronic acid polymers. The majority of hyaluronidases belong to glycoside hydrolase (GH) families, while a minority are classified within polysaccharide lyase (PL) families; their classification within the CAZy database reflects evolutionary relationships and structural correlations at the molecular level.
Karl Meyer introduced the term "hyaluronidase" to denote the enzymes that degrade HA, and classified hyaluronidases into three different groups based on biochemical analysis and generated end products. In particular, the hyaluronidases may be grouped into three primary groups: hyaluronoglucosaminidases, hyaluronoglucuronidases, and glucoronate lyases.
Hyaluronidase is abundant in nature and has been found from complex higher animals to lower microorganisms. Hyaluronidases are widely distributed in nature, being found in mammals, invertebrate animals (crustaceans, leeches, and insects), pathogenic fungi (Candida, Streptomyces), bacteria and bacteriophage.
Hyaluronidase has been isolated from a variety of sources, including snake and bee venoms, leech saliva, the acrosomal granula of spermatozoa, the lysosomal granula of various cells, and from bacterial toxins. Some bacteria, such as Staphylococcus aureus, Streptococcus pyogenes, and Clostridium perfringens, produce hyaluronidase as a means of using hyaluronan as a carbon source. Hyaluronidases are found in the venom of certain lizards and snakes, as well as honeybees, where they are referred to as "spreading factors."
Hyaluronidases are widely distributed in nature in, for example, mammalian testes, liver, and spleen, and in certain microorganisms. There is a wide range of biological sources of HAase, including leeches, microorganisms, vertebrates, and venom. Vertebrate HAase is sourced primarily from bovine, sheep, and humans.
Of the six hyaluronidase-like gene sequences in the human genome, HYALs 1 and 2 are of particular significance because they are the primary hyaluronidases active in human somatic tissue. Perhaps more importantly, they cleave anti-inflammatory and anti-fibrotic high-molecular-weight HA into pro-inflammatory and pro-fibrotic oligosaccharides, thereby regulating HA degradation and the development and progression of various diseases.
HYAL1 is the prototypical acid-active enzyme and PH20 is the prototypical neutral-active enzyme. Acid-active hyaluronidases, such as HYAL1 and HYAL2, lack catalytic activity at neutral pH. For example, HYAL1 has no catalytic activity in vitro over pH 4.5. HYAL2 is an acid-active enzyme with a very low specific activity in vitro. HYALP1 is a pseudogene, and HYAL3 has not been shown to possess enzyme activity toward any known substrates. HYAL4 is a chondroitinase and lacks activity towards hyaluronan.
Mammalian hyaluronidases can be further subdivided into those that are neutral-active, predominantly found in testes extracts, and acid-active, predominantly found in organs such as the liver. Exemplary neutral-active hyaluronidases include PH20. Human PH20 (also known as SPAM1 or sperm surface protein PH20) is generally locked to the plasma membrane via a glycosylphosphatidyl inositol (GPI) anchor. It is naturally involved in sperm-egg adhesion and aids penetration by sperm of the layer of cumulus cells by digesting hyaluronic acid.
Four different purified hyaluronidases have been approved for use in the United States, three of animal origin and one recombinant. They are indicated as adjuvants in subcutaneous fluid administration for achieving hydration, for increasing the dispersion and absorption of other injected drugs, or for improving resorption of radiopaque agents in subcutaneous urography. The three naturally-sourced hyaluronidases are orthologs of human HYAL5 (PH20) obtained from testicular preparations. They are sold under the brand names Vitrase (ovine, FDA-approved in May 2004), Amphadase (bovine, October 2004), and Hydase (bovine, October 2005).
Human recombinant hyaluronidase (Hylenex Recombinant)—approved for use in the United States in December 2005—corresponds to the soluble fragment of human HYAL5 (PH20) produced in culture by genetically engineered Chinese hamster ovary cells containing a DNA plasmid encoding the enzyme.
In 1928, Duran-Reynals first observed that extracts from mammalian testes and other tissues contained a "spreading factor" that enhanced the diffusion of subcutaneously injected dyes and antiviral vaccines. The discovery of hyaluronidase traces back to 1928, when Francesc Duran-Reynals, working at the Rockefeller Institute, identified a "spreading factor" in extracts of rabbit testicles that enhanced the diffusion of India ink, bacterial suspensions, and other substances through subcutaneous tissues in rabbits.
Later, in 1940, Chain and Duthie identified this substance as an enzyme that hydrolyzes HA and coined the term "hyaluronidase." It has been used within the sphere of medical practice since 1949.
Following the naming and biochemical characterization of hyaluronidase in the 1940s, the enzyme rapidly gained clinical interest for its ability to facilitate the diffusion of co-injected substances. It became commonly used in various fields of medicine, including anesthesia and pain, cardiology, radiography, oncology, ophthalmology, and plastic surgery. The recognition of hyaluronidase as a "diffusion factor" for drugs was central to its earliest clinical utility, and when applied as an adjuvant, hyaluronidase enhances the diffusion capacity and bioavailability of injected drugs.
Hyaluronic acid is a polysaccharide widely found in the extracellular connective tissue of animals. As the "cement" which binds cells together, the main constituent of the vitreous of the eye, and functionally important in joints, hyaluronic acid is of considerable physiological importance. Hyaluronidases belong to these GAG-degrading enzyme families and act on various substrates, preferentially cleaving HA, whereas chondroitin, chondroitin sulfate, and dermatan sulfate are degraded more slowly and with limited efficiency.
The catalytic mechanism of the hyaluronidases (glycosyl hydrolase family 56) resembles that of the glycosyl hydrolases belonging to families 18 and 20, which involves double displacement at C1 next to the β(1→4) glycosidic bond to be cleaved. The double displacement results in retention of configuration at C1. Concomitant with cleavage of the glycosidic bond, a glutamic acid residue (Glu131 in hHyal-1) transfers a proton to the C4 oxygen of the leaving HA fragment. Next, an incoming water molecule replaces the leaving HA fragment. The disposition of active site residues in hHyal-1 suggests that Glu131 and Tyr202 polarize the water molecule for the nucleophilic attack on C1, thus completing the hydrolysis.
By degrading HA in the ECM, hyaluronidase increases membrane permeability, thereby rendering tissues more permeable to injected fluids—the so-called spreading effect. As a consequence, hyaluronidase reduces viscosity of HA, which improves tissue diffusion and the resorption rate of excess fluids. Hyaluronidases act locally by cleaving the substrate hyaluronan and thereby reducing the viscosity of the gel matrix and allowing drugs to spread by bulk fluid (convective) flow, providing access to a larger capillary absorptive surface.
By modulating ECM composition and cellular signaling pathways, HAase plays a pivotal role in diverse biological processes, including wound healing, tissue regeneration, and tumor progression. Physiologically, hyaluronidase participates in diverse biological processes, including ECM turnover, tissue remodeling, and modulation of interstitial transport. The modulation of hyaluronidase enzyme and its substrate HA throughout the body is critical to maintain hyaluronan homeostasis, as HA degradation is associated with the pathogenesis of various health conditions.
HYALs cleave anti-inflammatory and anti-fibrotic high-molecular-weight HA into pro-inflammatory and pro-fibrotic oligosaccharides. This distinction is important because the functional consequences of HA degradation depend critically on the size of the resulting fragments. High-molecular-weight HA is generally associated with anti-inflammatory and tissue-protective roles, while the lower-molecular-weight oligosaccharides generated by hyaluronidase action can activate pro-inflammatory signaling cascades.
Hyals must be present on the surface of spermatozoa for natural fertilization because the ovulated oocytes are surrounded by cumulus cells with high-molecular-weight hyaluronic acid. To initiate the crucial cell adhesion events necessary for fertilization, sperm must penetrate extracellular matrix barriers containing hyaluronic acid (HA), a task thought to be accomplished by neutral-active hyaluronidases. Hyaluronidase 5 (Hyal5)/Hyal7 double-knockout (dKO) mice produce significantly fewer offspring than their wild-type (WT) counterparts because of defective COC dispersal.
Hyaluronidase is integral to the normal turnover of HA in connective tissues, cartilage, and synovial fluid. The synthesis and catabolism of HA in vivo is a reversible process regulated by both HAase and HAase synthase. This cyclical regulation is critical to maintaining the viscoelastic properties of joint fluid and the structural integrity of connective tissue matrices.
HYAL-treated wounds exhibited increased granulation tissue, diminished edema formation, and regulated the inflammatory response by modulating the release of pro- and anti-inflammatory cytokines, growth factor, and eicosanoid mediators. Moreover, HYAL increased gene expression of peroxisome proliferator-activated receptors (PPAR) γ and PPAR β/δ, the collagen content in the early stages of healing processes, as well as angiogenesis.
HAase inhibitors emerge as promising tools for maintaining HA homeostasis, with implications in anti-inflammatory, antimicrobial, and antitumor therapies by blocking excessive HA degradation. These enzymes are involved in different biochemical, physiological, and pathological conditions like degradation of hyaluronic acid, embryogenesis, transmembrane diffusion of drugs and toxins, inflammatory and allergic response to antigens, healing of wounds, bacterial meningitis, and bacteremia.
Accumulation of HA in several malignant diseases is associated with aggressive tumor type, cancer progression/metastasis, and poor prognosis. Pancreatic ductal adenocarcinoma (PDAC) is characterized by excessive hyaluronan (HA) accumulation in the tumor microenvironment, elevating interstitial pressure, resulting in tumor vascular collapse, hypoxia, and blocking chemotherapeutic agent perfusion and immune cells.
Hyaluronidases have been used as a spreading agent, improving the absorption of drugs and facilitating the subcutaneous infusion of fluids. This is the oldest and best-established clinical application. The rate and extent of dispersion and absorption is proportionate to the amount of hyaluronidase and the volume of solution.
Evidence strength: Strong (multiple clinical trials, FDA-approved indication). Recombinant human hyaluronidase (rHuPH20) increases the absorption and dispersion of infused fluids and drugs. Results from a Phase III, prospective, open-label, noncontrolled study of patients with primary immunodeficiencies indicated that IGSC infusion, facilitated by rHuPH20, is well tolerated and delivers infusion volumes at treatment intervals and rates equivalent to intravenous administration.
In four euglycemic clamp studies, coinjection of rHuPH20 consistently yielded acceleration of insulin absorption, providing twice the insulin exposure during the first hour, greater and earlier peak exposure, and half the exposure beyond 2 hours after injection. Insulin-action profiles were similarly accelerated, with a 15-minute faster onset of insulin action and a 45-minute shorter duration of action for each of the three commercial rapid-acting insulin analogues.
Evidence strength: Moderate-to-strong (multiple controlled pharmacokinetic studies in humans); primarily pharmacodynamic data.
The enzyme has been used as a local adjuvant to increase the diffusion capacity of local anesthetics, increasing the analgesic efficacy, and the anesthetized area particularly in the first minutes following injection, resulting in diminished intra- and postoperative pain. The clinical benefits of hyaluronidase as a local anesthetic spreading agent have been demonstrated in multiple studies. In a series of 72 dermatologic procedures, the addition of hyaluronidase to a local anesthetic minimized surface contour distortion and facilitated tissue undermining and dissection within subcutaneous tissue planes.
Evidence strength: Moderate (established clinical use; evidence from clinical series and controlled trials, though high-quality RCT data are limited).
In aesthetic medicine, the off-label use of hyaluronidase is considered the gold standard for the management of HA-filler-associated complications. In aesthetic medicine, the use of hyaluronidase is considered as the gold standard for the management of complications of HA fillers and should be immediately available at every treatment.
A database search yielded 395 studies; of those, 5 RCTs (all carried out in the USA) were selected (53 subjects), indicating the effectiveness of hyaluronidase for removal of uncomplicated injected HA nodules (forearm, upper arm, or back skin). The follow-ups ranged from 14 days to 4 years. The amount of HA filler injected into each site varied from 0.2 to 0.4 mL. A dose-dependent response was observed for most HA fillers, and no major adverse reactions were reported. Overall, for removal of every 0.1 mL of HA filler, 1.25–37.5 units of hyaluronidase were injected (single injections). When 3 consecutive weekly hyaluronidase injections were used, much lower doses of 0.375–2.25 units were utilized.
There was no evidence in the form of RCTs, clinical trials, and retrospective case-control studies on the removal/reversal of HA injections in the facial skin, or management of over-corrections, inflammatory nodules, or tissue ischemia/necrosis associated with HA filler injection. Based on studies on the forearm, upper arm, and back skin, hyaluronidase can be used for the reversal of uncomplicated HA filler injection nodules. However, further adequately powered studies are warranted to establish the ideal treatment protocol/dose of hyaluronidase for reversal of HA filler injections in the facial region or management of complications associated with aesthetic HA injection.
Evidence strength: Weak-to-moderate for elective use (5 small RCTs, only in non-facial areas). Substantial clinical experience but no high-quality RCT data for facial applications or emergency complications.
Current clinical practice recognizes that hyaluronidase, although widely regarded as the gold standard for managing aesthetic filler complications, remains an off-label treatment in many countries due to the absence of standardized dosing guidelines and formal regulatory approval for this indication. A 2025 systematic review and meta-analysis including 231 patients with vascular compromise following hyaluronic acid filler injection demonstrated that early administration of hyaluronidase, particularly within 6 hours of symptom onset, was associated with significantly improved clinical outcomes. Resolution rates reached 78.4% for cutaneous necrosis and 45.2% for visual impairment secondary to vascular occlusion, reinforcing the importance of prompt recognition and immediate enzymatic intervention to limit ischemic injury.
Emergent complications such as vascular occlusion and blindness require immediate, high-dose Hyal treatment.
Evidence strength: Weak (case series and one systematic review; no RCTs in this emergent context are available or ethically feasible).
Recombinant human hyaluronidase PH20 (rHuPH20) has been incorporated into United States Food and Drug Administration (FDA)-approved subcutaneous biologic therapies, including trastuzumab (Herceptin Hylecta) and rituximab, enabling the administration of larger drug volumes subcutaneously while reducing infusion times and healthcare resource utilization. The ENHANZE drug delivery platform leverages rHuPH20 to transiently depolymerize hyaluronan in the subcutaneous space, thereby facilitating rapid systemic absorption.
Currently, the anti-HER2-antibody Trastuzumab (Herceptin SC) and anti-CD20-antibody Rituximab (MabThera SC) are used along with hyaluronidase as an excipient in subcutaneous (SC) formulations.
Evidence strength: Strong (FDA-approved combinations, supported by Phase III clinical trial data).
Investigators examined the influence of bovine testes hyaluronidase (HYAL) during cutaneous wound healing in in vitro and in vivo assays, demonstrating in the wound scratch assay that HYAL increased the migration and proliferation of fibroblasts in vitro at low concentration; for example, 0.1 U HYAL enhanced the cell number by 20%. HYAL presented faster and higher re-epithelialization in in vivo full-thickness excisional wounds generated on adult Wistar rats back skin already in the early phase at the 2nd day post-operatory compared to the vehicle-control group. Wound closure area observed in the 16 U and 32 U HYAL-treated rats reached 38% and 46% compared to 19% in the controls, respectively.
Evidence strength: Preliminary (largely animal and in vitro data; robust human clinical trial evidence is lacking).
Local aberrations of HA metabolism have been reported in many solid tumor malignancies, where elevated levels of HA frequently correlate with poor prognosis in tumors such as pancreatic, breast, gastric, colorectal, ovarian, prostate, and lung carcinoma. To exploit this, a pegylated form of recombinant hyaluronidase (PEGPH20, or pegvorhyaluronidase alfa) was developed for systemic use.
Clinical trials evaluating pegylated hyaluronidase (PEGPH20) have not demonstrated a meaningful survival benefit. A 2022 Phase II study combining PEGPH20 with pembrolizumab in patients with hyaluronic acid–high metastatic pancreatic cancer reported a median progression-free survival of 1.5 months and a median overall survival of 7.2 months.
Results from the Phase III trials were less impressive. PEGPH20 in combination with nab-paclitaxel/gemcitabine for metastatic pancreatic cancer reduced tumor burden but had no impact on progression-free or overall survival. A similar Phase II trial where patients were not preselected for HA expression was stopped early for lack of efficacy and adverse events.
Evidence strength: Negative/Insufficient. Despite compelling preclinical rationale, Phase II and Phase III clinical trials in pancreatic cancer have failed to demonstrate a meaningful survival benefit for PEGPH20.
Besides its high potential in both surgery and aesthetic medicine, hyaluronidase has already been established in the management of extravasation of cytostatic drug infusion, as a therapeutic option in fibrotic diseases and for faster subcutaneous liquid absorption in pediatrics. This use is primarily supported by case series and institutional clinical experience.
An increasing number of studies have been reported on HAase inhibitors derived from various biological sources, and the majority of discoveries were from medicinal plants that have ethnobotanical claims for ailments associated with hyaluronan. Various classes of natural products identified—including alkaloids, flavonoids, and terpenes—have shown potent inhibitory activity against HAases in in vitro studies. These preliminary findings need further research to identify the active constituent(s) present in the extracts and to establish their mechanism of action and safety profile.
Evidence strength: Preliminary (in vitro only; no clinical trials of plant-derived HAase inhibitors as dietary supplements have been identified in the reviewed literature).
Hyaluronidase injection (bovine) is FDA-approved to increase absorption and dispersion of injected drugs (particularly local anesthetics used in ophthalmic surgery), for hypodermoclysis, and for use in subcutaneous urography. Hyaluronidase injection-ovine is available as injectable solution 200 units/mL in 1.2 mL vials, or as 6,200 units lyophilized powder for injection in 5 mL vials.
For subcutaneous fluid administration, 150 units of Hylenex, 150 units of Amphadase, or 200 units of Vitrase should be administered prior to hypodermoclysis to facilitate the absorption of 1,000 mL or more of fluid. In the UK, the usual dose as an adjuvant to subcutaneous or intramuscular injection is 1,500 units added directly to the injection. In the US, the usual dose used for this purpose is 150 units. The dosage differences notwithstanding—the dosage in the UK is ten times higher than in the US—no apparent differences in the safety profiles of animal-derived hyaluronidase products marketed in the US and UK, respectively, have been reported.
The absorption and dispersion of other injected drugs can be enhanced by adding 50 to 300 units of hyaluronidase (most commonly 150 units) to the injection solution.
With the patient prone, 75 units of hyaluronidase (Hydase) is injected subcutaneously over each scapula, followed by injection of the contrast medium at the same sites.
For removal of every 0.1 mL of HA filler, 1.25–37.5 units of hyaluronidase were used in single injections. When 3 consecutive weekly hyaluronidase injections were used, much lower doses of 0.375–2.25 units per session were utilized. Dosing recommendations are often based on the suggestions of leading authorities and assessment by expert panels.
If using hyaluronidase for extravasation, administer 1 to 6 mL (150 units/mL) into the existing IV line and/or subcutaneously in a clockwise manner around the area of extravasation. The usual dose is 1 mL hyaluronidase for each 1 mL of extravasated drug; this may be repeated several times over the next 3 to 4 hours.
The dosage of subcutaneous fluids in pediatric patients should be determined based on the patient's age, weight, and clinical condition. For premature infants or neonates, the daily dose should not exceed 25 mL/kg body weight, and the administration rate should remain below 2 mL/min. Pediatric patients should be carefully monitored to prevent overhydration by controlling both the infusion rate and total volume.
Despite a generally reassuring safety profile, hypersensitivity reactions remain an important consideration. A 2024 systematic review involving 106 patients identified prior hyaluronidase exposure and sensitization through insect or wasp venom as potential risk factors for the development of allergic responses. Overall, reported allergy rates are low, occurring in fewer than 0.1% of treated individuals, although rare cases of anaphylaxis have been described, particularly following retrobulbar or intravenous administration. In most instances, prompt management with systemic corticosteroids, with or without antihistamines, leads to rapid and complete resolution of symptoms.
The clinical manifestations of immediate hypersensitivity after hyaluronidase application include erythema, edema, urticaria, and in severe cases, can lead to anaphylaxis; treatment may include topical steroid creams or oral steroids or antihistamines. When the local injection dose is less than 1,500 IU, the allergic reaction is limited to the local area, but when high doses of hyaluronidase (200,000 IU) or intravenous injections are given, the risk of allergic reaction can rise to 31.3%.
Animal-derived hyaluronidase is immunogenic and may cause allergic reactions. rHuPH20 is better tolerated and is less likely to cause an allergic reaction. Approximately 6% of the population has anti-rHuPH20 antibodies that are non-neutralizing and not associated with clinically significant consequences. Accumulating evidence from clinical trials and postmarketing surveillance indicates that rHuPH20 acts locally, with no detectable systemic absorption, and demonstrates a favorable tolerability profile across diverse populations.
Because rHuPH20 is up to 100-fold more pure than animal-derived products based on activity and contains human amino acid sequences rather than bovine, it is expected that most or all of the allergic and immunogenic problems associated with the animal-derived impurities will be avoided.
Recombinant human hyaluronidase carries a black box warning of thrombosis. Risk factors for precipitating thrombosis are hypercoagulable conditions, prolonged immobilization, and advanced age. Adequate hydration before administration is recommended to reduce the risk of these adverse reactions.
Local anesthetics: Hyaluronidase accelerates the onset and shortens the duration of effect, and may increase the incidence of systemic reactions.
Hyaluronidase may increase the risk of adverse reactions when used with other drugs. Edema is the most frequently reported adverse effect associated with hypodermoclysis. Other reported adverse effects include injection site reactions, headache, fatigue, nausea, and fever.
Contraindications include hypersensitivity to hyaluronidase or any component of the formulation. The patient should be kept under observation in the clinic for any adverse reactions—when anaphylaxis to hyaluronidase occurs, it is usually within minutes, but there have been cases of delayed onset. All patients should be warned about allergic or anaphylactic response symptoms and instructed to seek medical attention promptly.
High-dose hyaluronidase can provoke hypersensitivity-like responses, such as non-infectious swelling and inflammation, while skin allergy tests remain normal. Hyaluronidase at concentrations greater than 1:10 (1,500:10 mL) can be irritant. Erythema at the injection site is a commonly known side effect.
Long-term animal studies have not been performed to assess the carcinogenic or mutagenic potential of hyaluronidase. Available data further suggest a low immunogenic potential, as treatment-emergent antibodies have not been associated with clinically significant adverse outcomes.
Hyaluronidase has not been adequately studied in pregnant populations. Use in pregnancy is advised only if necessary. It is not known whether hyaluronidase is excreted in breast milk.
Health conditions that Hyaluronidase may help support.
Body systems that Hyaluronidase may help support.
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