GMP-grade CD34+ selection from HLA-homozygous licensed cord blood units and short-term expansion under European ATMP regulations

Current Landscape of iPSC Haplobanks

The use of allogeneic induced pluripotent stem cell (iPSC)-derived cell therapies for regenerative medicine offers an affordable and realistic alternative to producing individual iPSC lines for each patient in need. Human Leukocyte Antigens (HLA)-homozygous iPSCs matched in hemi-similarity could provide cell therapies with reduced immune rejection covering a wide range of the population with a few iPSC lines. Several banks of HLA-homozygous iPSCs (haplobanks) have been established worldwide or are underway, to provide clinical grade starting material for cell therapies covering the most frequent HLA haplotypes for certain populations. Harmonizing quality standards among haplobanks and creating a global registry could minimize the collective effort and provide a much wider access to HLA-compatible cell therapies for patients with less frequent haplotypes. In this review we present all the current haplobank initiatives and their potential benefits for the global population.

GMP-compliant iPS cell lines show widespread plasticity in a new set of differentiation workflows for cell replacement and cancer immunotherapy

Cell therapeutic applications based on induced pluripotent stem cells (iPSCs) appear highly promising and challenging at the same time. Good manufacturing practice (GMP) regulations impose necessary yet demanding requirements for quality and consistency when manufacturing iPSCs and their differentiated progeny. Given the scarcity of accessible GMP iPSC lines, we have established a corresponding production workflow to generate the first set of compliant cell banks. Hence, these lines met a comprehensive set of release specifications and, for instance, displayed a low overall mutation load reflecting their neonatal origin, cord blood. Based on these iPSC lines, we have furthermore developed a set of GMP-compatible workflows enabling improved gene targeting at strongly enhanced efficiencies and directed differentiation into critical cell types: A new protocol for the generation of retinal pigment epithelium (RPE) features a high degree of simplicity and efficiency. Mesenchymal stromal cells (MSCs) derived from iPSCs displayed outstanding expansion capacity. A fully optimized cardiomyocyte differentiation protocol was characterized by a particularly high batch-to-batch consistency at purities above 95%. Finally, we introduce a universal immune cell induction platform that converts iPSCs into multipotent precursor cells. These hematopoietic precursors could selectively be stimulated to become macrophages, T cells, or natural killer (NK) cells. A switch in culture conditions upon NK-cell differentiation induced a several thousand-fold expansion, which opens up perspectives for upscaling this key cell type in a feeder cell-independent approach. Taken together, these cell lines and improved manipulation platforms will have broad utility in cell therapy as well as in basic research.

The monoculture of cord-blood-derived CD34+ cells by an automated, membrane-based dynamic perfusion system with a novel cytokine cocktail

Human leukocyte antigen (HLA)-matched cord blood (CB) transplantation is a procedure for the treatment of certain hematological malignancies, hemoglobinopathies, and autoimmune disorders. However, one of the challenges is to provide a sufficient number of T cell-depleted hematopoietic stem and progenitor cells. Currently, only 4%-5% of the CB units stored in CB banks contain enough CD34⁺ cells for engrafting 70-kg patients. To support this clinical need, we have developed an automated expansion protocol for CB-derived CD34⁺ cells in the Quantum system's dynamic perfusion bioreactor using a novel cytokine cocktail comprised of stem cell factor (SCF), thrombopoietin (TPO), fms-like tyrosine kinase 3 ligand (Flt-3L), interleukin-3 (IL-3), IL-6, glial cell line-derived neurotrophic factor (GDNF), StemRegenin 1 (SR-1), and a fibronectin-stromal-cell-derived factor-1 (SDF-1)-coated membrane. In an 8-day expansion of a 2 × 10⁶ positively selected CD34⁺ cell inoculum from 3 donor lineages, the mean cell harvest and cell viability were 1.02 × 10⁸ cells and 95.5%, respectively, and the mean frequency of the CD45⁺CD34⁺ immunophenotype was 54.3%. The mean differentiated cell frequencies were 0.5% for lymphocytes, 15.8% for neutrophils, and 15.4% for platelets. These results demonstrate that the automated monoculture protocol can support the expansion of CD34⁺ cells with minimal lymphocyte residual.

Public Cord Blood Banks as a source of starting material for clinical grade HLA-homozygous induced pluripotent stem cells

BACKGROUND

The increasing number of clinical trials for induced pluripotent stem cell (iPSC)-derived cell therapy products makes the production on clinical grade iPSC more and more relevant and necessary. Cord blood banks are an ideal source of young, HLA-typed and virus screened starting material to produce HLA-homozygous iPSC lines for wide immune-compatibility allogenic cell therapy approaches. The production of such clinical grade iPSC lines (haplolines) involves particular attention to all steps since donor informed consent, cell procurement and a GMP-compliant cell isolation process.

METHODS

Homozygous cord blood units were identified and quality verified before recontacting donors for informed consent. CD34+ cells were purified from the mononuclear fraction isolated in a cell processor, by magnetic microbeads labelling and separation columns.

RESULTS

We obtained a median recovery of 20.0% of the collected pre-freezing CD34+, with a final product median viability of 99.1% and median purity of 83.5% of the post-thawed purified CD34+ population.

CONCLUSIONS

Here we describe our own experience, from unit selection and donor reconsenting, in generating a CD34+ cell product as a starting material to produce HLA-homozygous iPSC following a cost-effective and clinical grade-compliant procedure. These CD34+ cells are the basis for the Spanish bank of haplolines envisioned to serve as a source of cell products for clinical research and therapy.

The wider perspective: cord blood banks and their future prospects

Over the past three decades, cord blood transplantation (CBT) has established its role as an alternative allograft stem cell source. But the future of stored CB units should be to extend their use in updated transplant approaches and develop new CB applications. Thus, CBT will require a coordinated, multicentric, review of transplantation methods and an upgrade and realignment of banking resources and operations. Significant improvements have already been proposed to support the clinical perspective including definition of the cellular threshold for engraftment, development of transplantation methods for adult patients, engraftment acceleration with single cell expansion and homing technologies, personalised protocols to improve efficacy, use of adoptive cell therapy to mitigate delayed immune reconstitution, and further enhancement of the graft-versus-leukaemia effect using advanced therapies. The role of CB banks in improving transplantation results are also critical by optimizing the collection, processing, storage and characterization of CB units, and improving reproducibility, efficiency and cost of banking. But future developments beyond transplantation are needed. This implies the extension from transplantation banks to banks that support cell therapy, regenerative medicine and specialized transfusion medicine. This new "CB banking 2.0" concept will require promotion of international scientific and technical collaborations between bank specialists, clinical investigators and transplant physicians.

Cord blood beyond transplantation: can we use the experience to advance all cell therapies?

Unrelated cord blood (CB) units, already manufactured, fully tested and stored, are high-quality products for haematopoietic stem cell transplantation and cell therapies, as well as an optimal starting material for cell expansion, cell engineering or cell re-programming technologies. CB banks have been pioneers in the development and implementation of Current Good Manufacturing Practices for cell-therapy products. Sharing their technological and regulatory experience will help advance all cell therapies, CB-derived or not, particularly as they transition from autologous, individually manufactured products to stored, 'off-the shelf' treatments. Such strategies will allow broader patient access and wide product utilisation.