Holoclar: first of its kind in more ways than one

Biologicals and Biomaterials for Corneal Regeneration and Vision Restoration in Limbal Stem Cell Deficiency

The mammalian cornea is decorated with stem cells bestowed with the life-long task of renewing the epithelium, provided they remain healthy, functional, and in sufficient numbers. If not, a debilitating disease known as limbal stem cell deficiency (LSCD) can develop causing blindness. Decades after the first stem cell (SC) therapy is devised to treat this condition, patients continue to suffer unacceptable failures. During this time, improvements to therapeutics have included identifying better markers to isolate robust SC populations and nurturing them on crudely modified biological or biomaterial scaffolds including human amniotic membrane, fibrin, and contact lenses, prior to their delivery. Researchers are now gathering information about the biomolecular and biomechanical properties of the corneal SC niche to decipher what biological and/or synthetic materials can be incorporated into these carriers. Advances in biomedical engineering including electrospinning and 3D bioprinting with surface functionalization and micropatterning, and self-assembly models, have generated a wealth of biocompatible, biodegradable, integrating scaffolds to choose from, some of which are being tested for their SC delivery capacity in the hope of improving clinical outcomes for patients with LSCD.

Surgical Technique for Oral Mucosa Harvesting in Autologous Cultivated Oral Mucosal Epithelial Cell Transplantation for Ocular Surface Disorders

Ex vivo cultivated oral mucosal epithelial cell transplantation (COMET) was first introduced in Japan in June 2021. This technique is used to treat limbal stem cell deficiency (LSCD). This article provides a detailed description of one of the most critical steps in COMET, which is the harvesting of oral mucosa, along with accompanying videos. The samples harvested using this method were successfully cultured into cell sheets, which were then used in surgical procedures without complications.

Regulatory Aspects for Approval of Advanced Therapy Medicinal Products in the EU

In the European Union (EU), advanced therapy medicinal products (ATMPs) undergo evaluation by the European Medicines Agency's (EMA) Committee for Advanced Therapies (CAT) to obtain marketing authorization under the centralized procedure. Because of the diversity and complexity of ATMPs, a tailored approach to the regulatory process is required that needs to ensure the safety and efficacy of each product. Since ATMPs often target serious diseases with unmet medical need, the industry and authorities are interested in providing treatment to patients in a timely manner through optimized and expedited regulatory pathways. EU legislators and regulators have implemented various instruments to support the development and authorization of innovative medicines by offering scientific guidance at early stages, incentives for small developers and products for rare diseases, accelerated evaluation of marketing authorization applications, different types of marketing authorizations, and tailored programs for medicinal products with the orphan drug designation (ODD) and the Priority Medicines (PRIME) scheme. Since the regulatory framework for ATMPs was established, 20 products have been licenced, 15 with orphan drug designation, and 7 supported by PRIME. This chapter discusses the specific regulatory framework for ATMPs in the EU and highlights previous successes and remaining challenges.

Early Clinical Outcomes of the First Commercialized Human Autologous Ex Vivo Cultivated Oral Mucosal Epithelial Cell Transplantation for Limbal Stem Cell Deficiency: Two Case Reports and Literature Review

The first product in the world for ex vivo cultivated oral mucosal epithelial cell transplantation (COMET) to treat limbal stem cell deficiency (LSCD), named Ocural^®, was launched in June 2021 in Japan. COMET was performed on two patients, including the first case in the post-marketing phase of Ocural^®. Pathological and immunohistochemical examinations were also carried out using specimens obtained before and after COMET and the spare cell sheet. In case 1, the ocular surface remained free from epithelial defects for approximately six months. In case 2, although defect of the cornea-like epithelia was observed after COMET for one month, it was resolved after the insertion of lacrimal punctal plugs. In case 1, adjuvant treatment was interrupted due to an accident during the second month after COMET, resulting in conjunctival ingrowth and corneal opacity. Eventually, a lamellar keratoplasty was required at six months after COMET. Immunohistochemistry revealed the presence of markers for stem cells (p63, p75), proliferation (Ki-67), and differentiation (Keratin-3, -4, and -13) in both the cornea-like tissue after COMET and a cultivated oral mucosal epithelial cell sheet. In conclusion, Ocural^® can be accomplished without major complications, and the stem cells derived from oral mucosa might be successfully engrafted.

Illustrative Potency Assay Examples from Approved Therapies

Advanced therapy medicinal products (ATMP) encompass a new type of drugs resulting from the manipulation of genes, cells, and tissues to generate innovative medicinal entities with tailored pharmaceutical activity. Definition of suitable potency tests for product release are challenging in this context, in which the active ingredient is composed of living cells and the mechanism of action often is poorly understood. In this chapter, we present and discuss actual potency assays used for the release of representative commercial ATMP from each category of products (namely, KYMRIAH^® (tisagenlecleucel), Holoclar^® (limbal epithelial stem cells), and PROCHYMAL^®/RYONCIL™ (remestemcel-L)). We also examine concerns related to the biological relevance of selected potency assays and challenges ahead for harmonization and broader implementation in compliance with current quality standards and regulatory guidelines.

Standard Gamble to Derive Utility Health States for Limbal Stem Cell Deficiency

Purpose

To generate UK health-related quality-of-life (HRQoL) data for adult patients with moderate-to-severe limbal stem cell deficiency (LSCD), unilateral or bilateral, due to physical or chemical ocular burns to help inform economic evaluations of treatments.

Patients and Methods

EQ-5D-3L with vision bolt-on scores was prospectively measured for one of five clinical scenarios of LSCD described in vignettes in a demographically representative population of 520 UK adults. These were converted to health state utilities using three different UK value sets. A standard gamble (SG) was then undertaken using 12 SG scenarios to examine the component drivers of health utility for the treatment of LSCD.

Results

For the EQ-5D-3L scenarios, the mean disutility for LSCD with poor visual acuity, pain and disfigurement in both eyes compared to one eye was −0.084 (range=−0.156 to −0.045 across the value sets). The mean disutility of bilateral LSCD with pain, disfigurement, and poor visual acuity compared to unilateral LSCD with only poor visual acuity in one eye was −0.104 (range=−0.151 to −0.078). Similarly, where one eye was affected, pain and disfigurement in combination were associated with a greater mean disutility than improvements in visual acuity alone: −0.011 (range=−0.04 to 0.005). Mean SG utilities were within a narrow range (0.682–0.765). Where one eye was affected, the main driver was disfigurement: mean utility was 0.731 (0.709–0.753) compared to 0.682 (0.659–0.704) when disfigurement was removed compared to vision restored to normal. For bilateral LSCD, mean utilities were 0.693 (0.672–0.715) for normal vision and 0.75 (0.73–0.771) when disfigurement and pain were removed.

Conclusion

Improvements in pain and disfigurement appeared to be the main factors driving differences in health utilities associated with symptom profiles in LSCD, with improvements in visual acuity having lesser impact.

EU Regulatory Pathways for ATMPs: Standard, Accelerated and Adaptive Pathways to Marketing Authorisation

Advanced therapy medicinal products (ATMPs) require evaluation by the European Medicines Agency’s Committee for Advanced Therapies prior to being placed on the European market, subject to a Marketing Authorisation granted by the European Commission. In common with other medicinal products, various regulatory pathways are available for taking ATMPs through clinical trials to market authorisation, and the regulatory pathway taken will depend on a product’s characteristics and the target patient population. With the industry poised to deliver more late-stage clinical and commercial ATMPs for serious diseases with high unmet medical need (e.g., T cell immunotherapies for cancer), bringing medicines to patients through optimized regulatory strategies and expedited pathways is assuming greater importance. The European Medicines Agency’s priority medicines (PRIME) scheme was introduced in 2016 specifically to enable this, and eligibility has been granted to 19 ATMPs as of the fourth quarter (Q4) 2018. Furthermore, two chimeric antigen receptor (CAR) T cell therapies, Yescarta and Kymriah, have recently completed their journeys through the scheme to Marketing Authorisation. This review discusses how the regulatory pathway for any particular ATMP, with or without PRIME designation, is determined and navigated.

Human stem cell based corneal tissue mimicking structures using laser-assisted 3D bioprinting and functional bioinks

There is a high demand for developing methods to produce more native-like 3D corneal structures. In the present study, we produced 3D cornea-mimicking tissues using human stem cells and laser-assisted bioprinting (LaBP). Human embryonic stem cell derived limbal epithelial stem cells (hESC-LESC) were used as a cell source for printing epithelium-mimicking structures, whereas human adipose tissue derived stem cells (hASCs) were used for constructing layered stroma-mimicking structures. The development and optimization of functional bioinks was a crucial step towards successful bioprinting of 3D corneal structures. Recombinant human laminin and human sourced collagen I served as the bases for the functional bioinks. We used two previously established LaBP setups based on laser induced forward transfer, with different laser wavelengths and appropriate absorption layers. We bioprinted three types of corneal structures: stratified corneal epithelium using hESC-LESCs, lamellar corneal stroma using alternating acellular layers of bioink and layers with hASCs, and finally structures with both a stromal and epithelial part. The printed constructs were evaluated for their microstructure, cell viability and proliferation, and key protein expression (Ki67, p63α, p40, CK3, CK15, collagen type I, VWF). The 3D printed stromal constructs were also implanted into porcine corneal organ cultures. Both cell types maintained good viability after printing. Laser-printed hESC-LESCs showed epithelial cell morphology, expression of Ki67 proliferation marker and co-expression of corneal progenitor markers p63α and p40. Importantly, the printed hESC-LESCs formed a stratified epithelium with apical expression of CK3 and basal expression of the progenitor markers. The structure of the 3D bioprinted stroma demonstrated that the hASCs had organized horizontally as in the native corneal stroma and showed positive labeling for collagen I. After 7 days in porcine organ cultures, the 3D bioprinted stromal structures attached to the host tissue with signs of hASCs migration from the printed structure. This is the first study to demonstrate the feasibility of 3D LaBP for corneal applications using human stem cells and successful fabrication of layered 3D bioprinted tissues mimicking the structure of the native corneal tissue.

Accelerating regenerative medicine: the Japanese experiment in ethics and regulation

In 2014, the Japanese National Diet introduced new laws aimed at promoting the clinical translation of stem cells and regenerative medicine. The basic action of these laws is to allow the early introduction of regenerative medicine products into the Japanese market through an accelerated approval process, while providing patients with access to certain types of stem cell and cell-based therapies in the context of private clinical practice. While this framework appears to offer enormous opportunities for the translation of stem cell science, it raises ethical challenges that have not yet been fully explored. This paper critically analyzes this framework with respect to the prioritization of safety over clinical benefit, distributive justice and public trust in science and medicine. It is argued that the framework unfairly burdens patients and strained healthcare systems without any clear benefits, and may undermine the credibility of the regenerative medicine field as it emerges.