Holoclar: Uses, Procedure & Side Effects

What Is Holoclar and What Is It Used For?

Holoclar contains ex vivo expanded autologous human corneal epithelial cells, including a critical population of limbal stem cells. These limbal stem cells reside in a specialized region called the limbus – the border zone between the clear cornea and the white sclera of the eye. Under normal conditions, limbal stem cells continuously self-renew and differentiate into corneal epithelial cells, maintaining a transparent, healthy corneal surface throughout a person’s lifetime. They serve as the ultimate regenerative source for the entire corneal epithelium.

When the limbus is severely damaged – most commonly by chemical burns (acids or alkalis) or thermal/physical burns – the limbal stem cells can be partially or completely destroyed. This condition is known as limbal stem cell deficiency (LSCD). Without a functioning limbal stem cell population, the corneal epithelium cannot regenerate properly. Instead, the conjunctival epithelium (the tissue that normally covers the white of the eye) begins to grow across the corneal surface, a process called conjunctivalization. This leads to chronic inflammation, neovascularization (growth of blood vessels into the normally avascular cornea), persistent epithelial defects, scarring, pain, light sensitivity, and progressive vision loss that can ultimately result in blindness.

LSCD is classified as partial (when some areas of functioning limbal stem cells remain) or total (when the limbal stem cells are completely destroyed around the entire circumference of the cornea). The severity of LSCD directly correlates with the extent of the original burn and determines the treatment approach. Holoclar is indicated for moderate to severe LSCD where at least some residual healthy limbal tissue is available for biopsy, typically corresponding to at least 1–2 mm² of intact limbus.

The Holoclar manufacturing process begins with a small biopsy (1–2 mm²) taken from an area of healthy limbus in the patient’s affected or contralateral (unaffected) eye. This biopsy is transported to a specialized Good Manufacturing Practice (GMP) laboratory, where the limbal stem cells are isolated and cultured on a fibrin membrane support using a well-characterized cell expansion protocol developed over more than two decades of research. Over a period of approximately 2–3 weeks, the cells proliferate to form a coherent sheet of corneal epithelial cells containing a sufficient proportion of limbal stem cells. The resulting product is a circular living tissue equivalent, approximately 300 mm² in area, containing between 79,000 and 316,000 cells per cm² on a transparent fibrin support.

The surgical implantation procedure involves careful preparation of the recipient eye under local or general anesthesia. The damaged corneal surface is first cleared by removing the conjunctivalized tissue and any fibrovascular pannus. The Holoclar living tissue equivalent is then placed directly onto the prepared corneal surface, where the fibrin membrane gradually dissolves over several days as the transplanted cells integrate with the patient’s ocular surface. Over the following weeks and months, the engrafted limbal stem cells repopulate the limbal niche and begin producing new, healthy corneal epithelial cells, progressively restoring a stable, transparent corneal surface.

Clinical evidence for Holoclar comes from a combined retrospective and prospective dataset. The pivotal HOLOCORE study, a prospective, uncontrolled, multicenter clinical study, alongside retrospective analyses of patients treated with the same manufacturing process prior to marketing authorization, provided data on efficacy and safety. In these studies, approximately 72% of patients achieved treatment success, defined as a stable corneal epithelium without central corneal neovascularization at 12 months post-transplantation. Many patients experienced clinically meaningful improvements in best-corrected visual acuity (BCVA), with some gaining several lines on standard visual acuity charts. Importantly, successful Holoclar treatment can also serve as a prerequisite for subsequent corneal transplantation (penetrating keratoplasty) in patients who require it for deeper corneal scarring, as a healthy epithelial surface is essential for graft survival.

What Should You Know Before Receiving Holoclar?

Contraindications

Holoclar must not be used in patients with known hypersensitivity to any of the components of the product or its excipients, including bovine serum components used during the manufacturing process, or to the fibrin membrane matrix. Since the active component consists of the patient’s own autologous cells, immunological rejection of the cellular component itself is not expected. However, allergy to the biological matrix materials (such as bovine-derived components or fibrin/thrombin of human origin) must be excluded before treatment.

Holoclar should not be administered if the eye to be treated has an active infection (bacterial, viral, or fungal keratitis or conjunctivitis) or active, uncontrolled inflammation. Any infection or acute inflammatory process must be fully resolved before the surgical implantation can take place. Similarly, the product should not be used if the ocular surface has not been adequately prepared or if there are structural abnormalities that would prevent proper graft adhesion, such as significant corneal perforation or uncontrolled elevated intraocular pressure.

Warnings and Precautions

Before proceeding with Holoclar treatment, the following precautions and considerations should be carefully evaluated by the treating ophthalmologist and discussed with the patient:

• Confirmation of LSCD diagnosis: A thorough clinical examination, including slit-lamp biomicroscopy and potentially in vivo confocal microscopy (IVCM) or impression cytology, must confirm the diagnosis of limbal stem cell deficiency. LSCD can present with variable severity, and the clinical features (conjunctivalization, superficial neovascularization, chronic inflammation, recurrent epithelial breakdown) must be carefully documented. The presence of sufficient remaining healthy limbal tissue for biopsy must be confirmed.
• Timing of treatment: Holoclar treatment should be performed once the acute phase of the burn injury has fully resolved and the ocular surface has stabilized. Treating during active inflammation significantly increases the risk of graft failure. A minimum waiting period of several months (typically 6–12 months after the burn) is recommended to allow inflammation to subside and the ocular surface to reach a stable state.
• Bilateral LSCD: In patients with bilateral burns, identifying sufficient healthy limbal tissue for biopsy may be challenging. If no healthy limbus remains in either eye, autologous limbal stem cell transplantation with Holoclar is not possible, and alternative approaches (such as allogeneic limbal transplantation from a living related donor or cadaveric donor, or oral mucosal epithelial transplantation) may need to be considered.
• Post-operative immunosuppression: After Holoclar implantation, a regimen of topical and potentially systemic anti-inflammatory and immunosuppressive medications is required to support graft survival. Topical corticosteroids are typically used for several months, and systemic immunosuppression (such as oral ciclosporin or mycophenolate mofetil) may be prescribed for a period determined by the treating physician. Patients must be monitored for the known side effects of these medications, including increased susceptibility to infection and, with prolonged corticosteroid use, elevated intraocular pressure (steroid-induced glaucoma) and cataract formation.
• Manufacturing and logistics: Holoclar is a living product with a limited shelf life. Once manufactured, it must be used within 36 hours. The logistics of coordinating the biopsy, manufacturing, transport, and surgical implantation require careful planning between the clinical center and the manufacturing facility. Any delays or logistical issues could render the product unusable.

Pregnancy and Breastfeeding

There are no specific clinical data on the use of Holoclar during pregnancy or breastfeeding. Since Holoclar is an autologous cell product applied locally to the ocular surface, systemic exposure to the cellular component is not expected. However, the post-operative immunosuppressive therapy required after Holoclar implantation (including systemic ciclosporin or corticosteroids) may pose risks during pregnancy and breastfeeding. Women of childbearing potential should discuss the timing of treatment and the potential risks of concomitant immunosuppressive therapy with their ophthalmologist and obstetrician before proceeding.

Animal reproductive toxicity studies have not been conducted with Holoclar, as the product is autologous and species-specific. The decision to proceed with treatment during pregnancy or breastfeeding should be made on an individual basis, weighing the potential benefits of restoring vision and ocular surface integrity against the risks associated with the required post-operative medications.

Children and Adolescents

The safety and efficacy of Holoclar in patients under 18 years of age have not been established. No clinical data are available in the pediatric population. While the underlying biology of limbal stem cell deficiency is similar in children and adults, the decision to use Holoclar in younger patients must be made on a case-by-case basis by experienced ophthalmologists, considering the severity of the LSCD, the availability of alternative treatments, and the ability of the child to comply with the post-operative care regimen.

How Does Holoclar Interact with Other Treatments?

Unlike conventional pharmaceuticals, Holoclar is a living tissue product and does not undergo traditional drug metabolism. It is not metabolized by cytochrome P450 enzymes and does not enter the systemic circulation in a pharmacologically meaningful way. Therefore, classical drug-drug interactions in the pharmacokinetic sense do not apply. However, several important considerations regarding concomitant treatments and the ocular environment must be taken into account to ensure optimal graft survival and clinical outcomes.

Topical Ophthalmic Medications

In the immediate post-operative period, the use of topical ophthalmic medications must be carefully managed. Preservative-free formulations should be used exclusively, as preservatives commonly found in eye drops (such as benzalkonium chloride) are toxic to corneal epithelial cells and can compromise the viability of the transplanted Holoclar graft. All topical medications used on the treated eye in the weeks and months following implantation should be preservative-free.

Topical corticosteroid eye drops (such as dexamethasone or prednisolone) are a standard component of the post-operative regimen and are essential for controlling inflammation. These are not a contraindication but rather a required part of the treatment protocol. However, prolonged use must be monitored for potential complications including elevated intraocular pressure and cataract development.

Systemic Immunosuppressive Therapy

Systemic immunosuppressants such as ciclosporin (cyclosporine) or mycophenolate mofetil are commonly prescribed after Holoclar implantation to create a favorable immunological environment for graft survival, even though the graft is autologous. These medications support the healing process by suppressing excessive inflammation that could damage the newly transplanted cells. Patients receiving systemic immunosuppression require regular monitoring of renal function (for ciclosporin), complete blood counts (for mycophenolate), and general immune status. The interaction profiles of these immunosuppressive drugs with other medications the patient may be taking must be carefully reviewed.

Other Surgical Procedures

Patients who have received Holoclar may subsequently require additional ophthalmic procedures such as penetrating keratoplasty (corneal transplant) to address deeper corneal stromal scarring, or cataract surgery if cataract develops as a complication of prolonged corticosteroid use. These procedures should be carefully timed and planned in consultation with the treating ophthalmologist to avoid compromising the Holoclar graft. A stable, healthy corneal epithelium is generally a prerequisite for successful corneal transplantation, which is one of the key benefits of successful Holoclar treatment.

What Is the Correct Dosage and Procedure for Holoclar?

Holoclar is fundamentally different from conventional medications in terms of dosing. It is not a drug that is taken in measured doses over time. Instead, each Holoclar product is a unique, patient-specific living tissue equivalent manufactured from the individual patient’s own cells. The “dose” is the entire prepared tissue graft, which is surgically implanted in a single procedure per affected eye.

Step 1: Limbal Biopsy

Step 2: Cell Expansion

Step 3: Surgical Implantation

Post-Operative Care

The post-operative regimen is critical to the success of Holoclar treatment and typically includes the following components, all tailored to the individual patient by the treating ophthalmologist:

• Topical antibiotics: Preservative-free antibiotic eye drops to prevent infection during the early healing phase, typically continued for several weeks.
• Topical corticosteroids: Preservative-free corticosteroid eye drops (such as dexamethasone or prednisolone) to control inflammation, typically continued for several months with gradual tapering.
• Systemic immunosuppression: Oral ciclosporin (cyclosporine) and/or mycophenolate mofetil to support graft survival, typically for 3–12 months depending on clinical response.
• Preservative-free lubricants: Artificial tears without preservatives to maintain ocular surface hydration.
• Follow-up visits: Frequent ophthalmological follow-up (typically daily in the first week, then weekly, monthly, and then at longer intervals) to monitor graft integration, epithelial healing, and any complications.

Repeat Treatment

In cases where the initial Holoclar treatment does not achieve complete success (partial graft failure or late graft loss), repeat treatment may be considered. The decision to retreat must be based on a careful assessment of the residual healthy limbal tissue available for a new biopsy, the likely cause of the initial graft failure (which should be addressed if possible), and the overall ocular surface status. Some patients in the clinical studies underwent more than one Holoclar procedure with favorable outcomes after retreatment.

Elderly Patients

There is limited clinical experience with Holoclar in elderly patients (over 65 years of age). No dose adjustment is applicable as Holoclar is a single-application procedure. However, elderly patients may have additional comorbidities, slower wound healing, and increased susceptibility to the side effects of post-operative immunosuppressive medications, which should be carefully considered in the treatment plan.

What Are the Side Effects of Holoclar?

The safety profile of Holoclar has been characterized through clinical studies and post-marketing surveillance. Because Holoclar is an autologous cell product that is surgically implanted, the side effects profile reflects a combination of the surgical procedure itself, the healing process, and the required post-operative medications. The following adverse reactions have been reported in clinical studies with Holoclar:

It is important to distinguish between side effects directly attributable to the Holoclar product itself and those related to the surgical procedure or the required post-operative medications. Blepharitis, eye pain, and ocular hyperemia are commonly encountered after any ocular surface surgery and are not specific to Holoclar. Corneal neovascularization may represent incomplete resolution of the underlying LSCD rather than a side effect of the treatment per se.

Complications related to the post-operative immunosuppressive therapy (systemic ciclosporin, mycophenolate, or prolonged topical corticosteroids) include nephrotoxicity, hypertension, bone marrow suppression, increased susceptibility to infections, and metabolic disturbances. These are well-characterized side effects of the immunosuppressive drugs themselves and require regular monitoring throughout the treatment period.

Graft failure – where the transplanted cells do not successfully engraft and the corneal surface fails to regenerate – is the most significant risk of Holoclar treatment. In clinical studies, approximately 28% of patients did not achieve the primary endpoint of treatment success at 12 months. Factors that may contribute to graft failure include severe underlying ocular surface disease, persistent inflammation, inadequate post-operative medication compliance, mechanical trauma to the graft during the early healing phase, and an insufficient proportion of stem cells in the manufactured product. Some patients with initial graft failure may benefit from repeat treatment.

How Should Holoclar Be Stored?

Holoclar is fundamentally different from conventional pharmaceutical products in terms of storage requirements. As a living tissue equivalent containing viable human cells, it requires specific handling conditions to maintain cell viability and potency. The product is supplied in a sealed, sterile container with a small amount of transport medium to keep the cells hydrated during transit.

The key storage and handling requirements for Holoclar are as follows:

• Temperature: Store at 15–25°C (59–77°F). Do not refrigerate. Do not freeze. Exposure to temperatures outside this range can compromise cell viability and render the product ineffective.
• Shelf life: Once released from the manufacturing facility, Holoclar must be used within 36 hours. There is no extended shelf life. This extremely short shelf life reflects the living nature of the product and necessitates precise coordination between the manufacturing facility and the clinical center.
• Do not sterilize: The product must not be sterilized (e.g., by irradiation or chemical sterilization) after manufacture, as this would kill the living cells.
• Keep in original container: Do not open the sealed container until immediately before use in the operating room. The container protects the product from contamination and desiccation.
• Visual inspection: Before use, the surgeon should visually inspect the product through the transparent container to confirm the integrity of the living tissue sheet on the fibrin membrane. Any product that appears damaged, discolored, or shows signs of contamination must not be used.
• Single use only: Each Holoclar implant is manufactured for a specific patient and intended for a single application. Any unused product or waste material must be disposed of in accordance with local regulations for human biological materials.

Because of these strict storage requirements and the extremely short shelf life, the logistics of Holoclar treatment require careful advance planning. The manufacturing facility, transport company, and clinical center must coordinate closely to ensure the product arrives at the hospital in optimal condition and that the operating room is prepared for implantation within the 36-hour window.

What Does Holoclar Contain?

Active Component

The active component of Holoclar is ex vivo expanded autologous human corneal epithelial cells containing limbal stem cells. These are the patient’s own cells that have been isolated from a small limbal biopsy and expanded in laboratory culture. The final product contains between 79,000 and 316,000 cells per cm², with a critical subpopulation of cells expressing high levels of p63 (a transcription factor that serves as a molecular marker of limbal stem cell identity and regenerative capacity). A minimum threshold of 3.5% p63-bright cells is required for product release, as this has been correlated with successful clinical outcomes in the HOLOCORE study.

Fibrin Membrane Support

The cells are cultured on and delivered within a transparent fibrin membrane, which serves as a mechanical support for the fragile cell sheet during transport and surgical handling. The fibrin membrane is composed of human fibrinogen and human thrombin (derived from pooled human plasma). After implantation, the fibrin membrane gradually dissolves over several days through natural enzymatic degradation, leaving only the transplanted cells integrated with the patient’s corneal surface.

Residual Manufacturing Components

Trace amounts of the following components from the manufacturing process may be present in the final product:

• Fetal bovine serum (FBS): Used in the cell culture medium to support cell growth. Residual amounts are present in the final product. Patients with known bovine protein allergy should be evaluated carefully.
• Murine 3T3-J2 feeder cells (irradiated): Used as a feeder layer to support limbal stem cell expansion. These cells are growth-arrested by irradiation and are not viable in the final product, but residual cellular material may be present.
• Cell culture medium components: Including Dulbecco’s Modified Eagle Medium (DMEM), Ham’s F12 medium, cholera toxin, insulin, hydrocortisone, triiodothyronine, and epidermal growth factor (EGF). These are present in trace quantities.