Thomson Scientific 2006 event report

European Stem Cells & Regenerative Medicine Congress – A Terrapinn Meeting
5-7 June 2006, London, UK

Reported by Leonie Croydon, Thomson Scientific Ltd, London, UK  Email: Leonie.Croydon@thomson.com

Introduction

Terrapinn's European Stem Cells & Regenerative Medicine Congress was well attended, with over 100 delegates from
diverse realms within industry and academia. The meeting covered a range of therapeutic areas. Both lecture and panel session formats were used, as well as a novel 'speed-networking' approach for meeting delegates.

The meeting was distinguished by the presence of a number of eminent personalities from the field, including Professor Dame Julia M Polak (Imperial College London, UK) and Professor Ian Wilmut (University of Edinburgh, UK). While many speakers, from both research and business backgrounds, were confident in the future use of stem cell technologies and therapies, they were also willing to admit the presence of a number of technical and political hindrances to the advancement of the discipline.   This report focuses on use of stem cells as therapeutics and for predictive screens.

Stem cell technologies to predict liver and heart toxicity

The importance of stem cell platforms was covered by Ian Cotgreave (AstraZeneca plc, Sweden), a toxicologist by trade, who gave a stimulating talk on the role of stem cells in clinical safety assessment, and their potential utility in problem solving with regards to liver toxicity. Although drug-induced liver injury (DILI) is a rare problem, with an incidence of approximately 14 cases in 100,000, it does have the ability to cause withdrawal of drugs from the market. In order to obtain fewer costly late-stage discontinuations, the industry is trying to implement a 'fail faster' climate, and improved prediction of DILI occurrence is an area in which both scientists and business specialists believe improvements can be made. Dr Cotgreave likened the current preclinical models' predictive ability to tossing a coin, expressing a desire for the precision of prediction to be nearer 100% than 50%, and stating that the regulatory authorities have no tolerance for toxicity. Problems with the existing models include cross-species variability, sub-optimal screens, poorly validated biomarkers, the inability of monolayers to perform metabolism studies following loss of cell character, and the complexity of the liver pathways. While the sandwich or '3D' models used at present are preferable to monolayer cultures due to their ability to maintain cytochrome P450 ability, they still provide only 70% precision in predictive ability. A dramatic shortage of human material for these cultures is also a problem.

AstraZeneca, the Karolinska Institute and Cellartis are collaborating on hepatocyte-like human embryonic stem cells (hESC) for predictive drug screens. These cells express cytochrome P450 enzymes in the absence of a sandwich culture, demonstrate normal induction in response to xenobiotics, exhibit glutathione transferase enzymes usually present in the liver and are amenable to pharmacogenetic characterization. Although these cells show great promise for use in the field of predictive toxicity, the lack of a fully organotypic test would mean that extensive animal testing would still be required by the regulators. The liver is an organ of complex cellular architecture, not merely parenchymal, and co-cultures of Kuppfer (and/or other liver cells) would have to be introduced to provide a better model of liver homeostasis in response to toxins, and other environmental elements.

Gabriela G Cezar (University of Wisconsin-Madison, USA) also discussed the need for improved predictive models to decrease the late-stage attrition rate. Although it was noted that animal use will remain essential for the assessment of systemic effects, Dr Cezar did assert that human stem cell models could fulfill some of the '3 Rs criteria' - to refine, reduce and replace the need for animals in research. The technologies could also evoke a better understanding of human toxicological pathways, and provide robustness and stability due to the cells' natural endogenous function and immortality. Research into teratogens, such as the histone deacetylase inhibitor valproic acid (approved for the treatment of epilepsy and currently being developed by G2M Cancer Drugs AG as a treatment for cancer), has shown in a real time PCR reporter gene assay that similar gene expression changes were observed with the hESC in vitro model compared to relevant in vivo animal studies. This suggests that the technology may have application in developmental toxicity as a predictive screen. Another area of interest was cardiotoxicity, where Dr Cezar eluded to the use of hESC models in an effort to move away from the current hERG-centric approach. Cardiomyocytes derived from ESCs have multiple functional ion channel types for in vitro screening. The presentation was concluded with a roundup of the challenges facing research into stem cells in toxicity, including the need to define endpoints, the problems of scalability and the importance of correlating in vitro and in vivo results.

In the following panel session, the lack of industrial funding into stem cell research was criticized. Reasons for this predominantly fell under the category of cautiousness - investment is only likely to be forthcoming when the technology is fully validated, when regulators express more of an interest in this as a requirement for drug marketing or if governments reduce restrictions on the use of hESCs. Dr Cotgreave considered a minimum of 6 months testing of 20 to 30 pharmacologically relevant compounds in about six functional assays would be necessary for model validation before major pharmaceutical companies might start to become involved. The cell type would also have to be defined and benchmarked against existing models.

Lost in translation

A key problem highlighted during the meeting was the poor translation of potential therapies from the 'blue-sky' field of academic research into a marketable product. Chris Mason (University College London, UK) stressed the need for early collaboration between pharmaceutical and biotechnology companies, clinicians and academics. Cell therapies require complex, highly regulated manufacturing processes, which need to be tackled at an early stage. Preferably the bioprocessing should run in parallel with research to allow speedier entry into the market. Avinoam Kadouri (Rainbow Biotechnologies Co Ltd, Israel) also outlined the 'gap' issue, citing cell source, level of differentiation, reproducibility, safety, method of administration, and the clarification of regulatory issues as the fundamental considerations for the advancement of regenerative medicine.

It appeared that the predominant current concern was scalability. Cells are difficult to manipulate, and require costly and labor-intensive processing with low volume outputs, which has obvious cost-price implications. Decisions of whether to scale up from one cell line, with resultant immune issues, or scale out from several, at a higher price, must be made. Dr Mason expressed a desire to create 'something for the masses' using a technique similar to that used by Henry Ford in the early days of car manufacture; that is, to initially make small amounts of human-created therapies available to the most needy patients, and gradually automate the process, allowing prices to drop, and the product volume and number of patients treated to rise. Three objectives could contribute to reaching this goal: a consistent quality of products, the cooperation of regulatory bodies and economically sound business models.

Funding in the UK

In 2005, STG 1 billion was available for stem cell development, 80% of which was derived from government sources. Due to relatively liberal regulatory approaches in the UK, basic preclinical work in this area is well funded; however, in clinical development a large gap exists between the amount of work taking place and the amount of funding. Commercial funding is sparse as the research is not always immediately recognized to be a potential money-spinner. Translational research is often dull, disciplined, repetitive and expensive, and as it is unlikely to lead to top-level publications, attracting top-level students and putting together successful grant applications can be difficult. In terms of the long-term health economics, however, investment in stem cells seems essential. For example, the financial burden of diabetes on the NHS is already massive and looks set to continue to grow as more people develop the disease. If stem cells could be developed which negated the need for costly therapeutics, this burden could be dramatically reduced.

David Macauley (UK Stem Cell Foundation (UKSCF), UK) gave an interesting introduction to the funding available through the UKSCF, a non-profit organization recently formed as a result of recommendations from the UK Stem Cell Initiative, which has the primary aim of translating stem cell science from a promising idea into clinically suitable therapies via the formation of private/public partnerships. With Sir Richard Branson and Lord Robert Winston among its trustees, the foundation has powerful backing and has raised STG 25 million since its inception a little over 6 months ago. Pursuing research across the spectrum, with little concern for the origin of the stem cells (adult or embryonic), the UKSCF expected to announce its first products "very shortly".

Preclinical work and IND filings

The fact that the US government will not fund hESC development through the National Institute of Health (NIH) has
left the door open for companies to exploit and fund development in these areas. Thomas Okarma (Geron Corp,
USA) spoke of Geron's ESC therapies, of which eight ESC-derived cell lines exist, cultivated with standards stringent enough to meet FDA regulations. At the time of this meeting, the first cell line was expected to enter the clinic for spinal cord injury (SCI) in 2007. Geron selected SCI as the pioneering indication as it is an area where any improvement, however small, would be considered a benefit to patients. As a result, it would be relatively easy to satisfy regulatory authorities and bring the drug to market, compared to an indication where there were numerous alternative treatments already available.

IND-enabling studies, including biodistribution assessments with labeled cells, and optimization of administration route and dose, were underway at the time of this meeting. As were tests concerned with toxicology, tumorigenesis and immune reaction, which were designed using advice provided by the FDA. Negotiations to decide the number of animals required to necessitate the completion of these studies were also ongoing. A multicenter (12 sites enrolled at present), randomized, unblinded, dose-escalating (ESC doses up to 2 x 10(7) cells) study is planned in patients with sub-acute functionality and complete thoracic lesions (regions T3 to T7). Higher areas of the spine were not considered for initial assessment due to problems associated with toxicity detection in descending neural pathways. Upon completion of the first two cohorts it was expected that patients with lesions in cervical regions would also be included (regions C5 to T2). Patients were to be evaluated for 3 months, with a 9-month follow-up period, and were to be temporarily administered the immunosuppressant cyclosporine. Dr Okarma anticipated that it would be at least a year before the optimal dose was identified. The primary endpoint of the study was to be safety, both neurological and overall, with secondary endpoints being efficacy as measured by the American Spinal Injury Association (ASIA) scoring system, bowel and bladder functionality and independence measurements.

Geron's follow up cardiomyocyte cell line was also outlined, with data demonstrating that the cells respond normally to drugs exhibiting regular electrophysiological profiles. Cell preparations were shown to be 80% pure and scaleable. At 4 weeks post-injection, cells resided in the infarct zone and were able to survive due to their inherent glycogen sources. Geron is working on scaleable methods to produce islets for use in diabetic therapy. In vitro observation of the differentiation process showed that co-localization of C-peptide and Pdx1 occurred at day 36 in cell cluster structures similar to islets, but it was unknown if this would occur in animals as well. The cells lasted more than 50 days. The company's hepatocyte hESCs also exhibited inducibility and scalability. Placentally-derived adult fibroblasts (both male and female), which differentiate in vitro, can be easily scaled up, and have diminished ethical problems compared to hESC-derived lines, were also mentioned by Dr Okarma.

An IND for the adult stem cell therapy REN-001 (ReNeuron Group plc), indicated for chronic stroke, was expected to be filed in the US by the end of the year, according to ReNeuron's Michael Hunt (UK). Regulatory debate had occurred previously, with a pivotal pre-IND meeting having taken place with the FDA in July 2005, and discussions with EU regulators (UK, Germany and Sweden) in October 2005. In vivo studies demonstrated the ability of clinical grade cells, scaled up by the ReNeuron's Scottish collaborator BioReliance and stored in a GMP-standard cell bank facility, to restore sensory and motor function in a dose-dependent manner in rats disabled by stroke. Mr Hunt described the company's exclusively licensed stem cell expansion platform, which requires the addition of c-mycER (a fusion protein of the estrogen receptor (ER)) and c-myc to fetal cells before the selection of the relevant cells. Cells remained inactive until given a metabolite of the ER modulator tamoxifen, after which they could be developed into a large number of clonal cell lines, selected by different characteristics.

Michael West (Advanced Cell Technology Inc, USA) presented the stem cells portfolio of a small biotech on the lookout for outlicensing opportunities, describing stem cell science as a confluence between molecular and cell biology The current status of a research program called ACTC60 for smooth muscle was detailed. INDs were planned for retinal pigment epithelial cells in 2007, and for dermal progenitors and hemangioblasts in 2008.

Clinical success

Trials of adult autologous, bone marrow-derived, stem cells (Aastrom Biosciences Inc) were outlined by Aastrom's Janet Hock (USA). The cells were expanded ex vivo and enriched for a number of uses using the company's Replicell system. The cells had been administered to over 220 patients globally, at low volumes of aspirate (30 to 50 ml) without causing adverse events, despite the fact that cultures were unpurified allowing cells to grow in presence of facilitator cells. In the EU, a total of five endentulous patients with severe loss of maximillary floor sinus bone (co-morbidities were plentiful and included smoking and osteoporosis) were treated with cells and BioOss matrix, or matrix alone, with a brief provision of tetracycline. Treated patients displayed graft bone similar to original bone, had reduced post-operative swelling relative to control and had no adverse events. Two studies of non-union fracture had also taken place, whereby cells were placed into the marrow between the broken ends. In the EU study, five of six patients had new bridging bone and disappearance of fracture line in radiographs at 6 months post-injection, and the final patient was recovered at 9 months. At 6 months, patients with tibia injuries were weight-bearing and those with humeri injuries had restored range of motion. No adverse events were observed up to two years post-surgery, and similar to results from the jaw study, there was a decrease in post-operative swelling and inflammation. The US study showed similar results in those who had failed prior therapies. Finally, a trial of patients with diabetic foot callus was described in which patients expressed mature vasculature, new bone, active bone formation and a decrease in the need for allograft matrix extender at 3 months post-treatment. The studies showed that there was little relationship between dose and efficacy in stem cell therapies.

Cardiomyocyte therapy

ES Cell International's potential stem cell therapeutics for treatment of heart failure was described by the company's Alan Colman (Singapore). It was predicted that this therapy could have a commercial value similar to current treatment methods if it could be optimized efficiently in a clinically compliant method. The cells are autologous, contractile, easily procured, highly scalable and resistant to ischemia. Dr Colman was keen to assert that positive results may have been due to other interventions than cell therapy. An increased proportion of hESCs with sarcomeric structures (from 15 to 95%, 4-weeks post-transplantation) were observed in a SCID mouse model, in alignment with endogenous cardiomyocytes. In vivo maturation was thought to have occurred, demonstrated by the downregulation of smooth muscle actin and upregulation of Cx43 and MLC2V. hESC-derived cardiomyocytes survived and matured regardless of cell fusion, and non-cardiomyocytes died, migrated away or differentiated to become cardiomyocytes. In an athymic mouse model, injection of green fluorescent protein (GFP)-labeled hESC (1 to 5 x 10(6) cells, 15 to 30% cardiomyocytes) resulted in robust long-term engraftment of hESCs for 4 weeks in mice with and without myocardial infarction, as well as wall thickening in cardiomyocyte-treated animals and increase of ejection fraction. A pig model of an immune suppression regime was evaluated: GFP-hESC (1 x 10(7) cells, 15 to 30% cardiomyocytes) were found to be present in the infarct zone for up to 6 weeks, surrounded by leukocytes.

This report was originally published on the Thomson Pharma database from Thomson Scientific www.thomsonpharma.com