Riordan et al. reported a clinical study of three Multiple Sclerosis patients who were treated with intravenous infusions of 25 to 75 million autologous adipose- derived SVF cells combined with intravenous infusions of allogeneic CD34+ cells and ASCs (Riordan et al., 2009). Their study demonstrated significant improvements in patient conditions, and the need for regular medication was clearly reduced after ASC treatment. However, MRI images obtained 6-7 months after the stem cell treatment showed lesions that were highly similar to the lesions observed prior to the stem cell treatment. Nevertheless, this study demonstrated that intravenous injections of SVF cells are well tolerated and may yield symptomatic improvements.
Fistulas, including Crohn's Disease Joint Disorders Neurological Disorders Cardiovascular Diseases Pulmonary Diseases Limb Ischemia Esthetics including Lipodystrophy Ulcers Breast Reconstruction Diabetes Ovaries Bone Renal Tract Liver Cirrhosis Erectile Dysfunction Urinary Incontinence Fecal Incontinence Tendon Eye Immune system disorders Anemia Others
Figure 6. A total number of 164 clinical trials using ASCs were ongoing on 19 May 2015, as searched from clinicaltrials.gov. Clinical studies are categorized based on the disease or target tissue of the treatment. The “Others” group includes clinical trials that could not be categorized into defined groups, e.g., trials for treatment of HIV, burn wounds, leukemia, amputation stumps, obesity, depressed scars, and urethral strictures in males. Only 10 out of 164 trials progressed into phase III or IV, whereas 120 trials were still in phase I or II. The remainder of the trials did not specify the current status.
The results of randomized clinical trials in a larger patient cohort are still needed before any conclusions can be drawn.
A clinical study using ASC injections for the treatment of critical limb ischemia was also published with encouraging results (Bura et al., 2014). The feasibility and safety of autologous ASCs was demonstrated in 108 cells that were intramuscularly injected into the ischemic leg of patients followed by improved wound healing that supported a functional efficiency of the treatment (Bura et al., 2014). Pre-clinical in vivo studies have suggested that ASCs exposed to ischemia or hypoxia secrete cytokines that improve cell proliferation and vasculogenesis directly without the presence of the ASCs themselves (Eto et al., 2011). Similar conclusions were drawn by Bhang et al., who demonstrated in vivo that the therapeutic efficacy of the ischemia treatment may be duo to paracrine effects (Bhang et al., 2011). These results suggest that ASC-conditioned medium alone may be sufficient for treatment of ischemic injuries, without the need for direct cell transplantation (Gimble et al., 2012).
The immunomodulation capacity of ASCs is likely involved in the therapeutic effects of many treatments described in this work; however, the overall number of clinical trials of ASCs that study severe immunological diseases such as sepsis or GVHD is still relatively small. The advanced biopharmaceutical company TiGenix NV has focused on developing novel therapeutics with allogeneic ASCs for treatment of inflammatory and autoimmune diseases (http://www.TiGenix.com).
This company has recently announced a phase I trial designed to demonstrate the safety and efficacy of allogeneic ASCs for treatment of sepsis using intravenous infusions of 0.25 - 4 x106 ASCs/kg (NCT02328612; www.clinicaltrials.gov). This trial uses healthy volunteers challenged with a bacterial endotoxin that elicits an inflammatory response that induce sepsis-like clinical symptoms. TiGenix expects to complete the phase I trial by the third quarter of 2015 and to follow with a Phase II trial. Apart from studies performed by TiGenix, another phase I/II clinical trial evaluating the use of allogeneic ASCs for the treatment of chronic, extensive GVHD is currently ongoing (NCT01222039; www.clinicaltrials.gov). This clinical study investigates the safety and efficacy of intravenously injected allogenic ASCs (1 - 3 x106 cells/kg) used in combination with a gradually descending dosage of the conventional treatment.
Moreover, Fang and co-workers have reported clinical case studies on the promising use of allogeneic ASCs for preventing steroid-resistant acute GVHD.
Transplantation of allogeneic ASCs was reported with successful results in 7 of 9 patients when patients received intravenous infusions of 1.0-1.5x106 ASCs/kg (Fang
et al., 2007a; Fang et al., 2007b; Fang et al., 2007c; Fang et al., 2009). The mechanism responsible for the improved outcomes of these patients is likely connected to a shift from a pro-inflammatory to anti-inflammatory cytokine milieu (C. S. Lin et al., 2012).
Similar to the work of Fang et al., the use of BM-MSC has been demonstrated in a phase II study as an effective therapy for patients with steroid-resistant, acute GVHD (Le Blanc et al., 2008). Although these clinical studies show encouraging results for treatment of steroid-resistant acute GVHD patients, preliminary trials using ASCs must be carefully followed to ensure both safety and efficacy for future treatments.
An important aspect in clinical translation is the ex vivo cell expansion method often required for ASC-based therapies to obtain clinically sufficient cell numbers for effective treatments. One possibility is use of a non-expanded adipose SFV, as has been performed by Riordan et al. (Riordan et al., 2009). In this way, the cell expansion step can be avoided, but relatively little is known about the potential clinical effects of whole lipoaspirate that contains numerous cell populations in addition to ASCs. For larger cell numbers, safe and efficient in vitro cell isolation and expansion techniques are required for clinical use of cells. The majority of the protocols use reagents derived from animal sources, although the risks and benefits of using of animal-derived reagents should be carefully assessed because of safety concerns (Mackensen et al., 2000; Selvaggi et al., 1997). In the clinical trials described above, Garcia-Olmo et al. used FBS supplemented medium for cell expansion (Garcia-Olmo et al., 2009a), whereas Bura et al. used human-platelet-growth-factor- enriched plasma for cell expansion (Bura et al., 2014). Fang et al. used 2% fetal calf serum in combination with growth factor bFGF, insulin-like growth factor (IGF), and platelet-derived growth factor (PDGF) (Fang et al., 2007a).
However, the identification of XF alternatives for standard FBS-based media is important for considering clinical applicability of ASCs. An ideal culture media should be cost effective, display minimal batch variability and low immunogenicity and be free of all animal products and likely allogenic derivatives as well (Johal et al., 2015). Commercially available XF and SF media exist that meet these criteria, such as the MesenCult™-SF Culture Kit from Stem Cell Technologies and STEMPRO®
MSC SFM from Life Technologies, which both support the multilineage capacity of ASCs with significantly improved ASC proliferation rates (Al-Saqi et al., 2014a;
Lindroos et al., 2009) (Section 2.4.3.). If the cost effectiveness of these XF/SF media is reasonable, and adequate experimental data on ASC performance exist, these defined culture conditions will become clinically favored. Nevertheless, the culture media manufacturers should guarantee that a given media is available in the long-
term; if the pre-clinical and clinical data are demonstrated with a given media, it should be available for patient treatments. Otherwise, many additional studies should be performed to demonstrate the cell performance under distinct media, which would be substantially expensive for the producer of cell therapies.
Clinical trials are a required step forward in translation to cell-based therapies and for commercial use of cell-based products as well. However, licensed products and those approaching marketing authorization are still few. A major challenge in commercialization of cell-based products is the manufacturing and quality assurance of these complex products because cells are much more complex entities than small molecules and therapeutic proteins (Salmikangas et al., 2015). Demonstration of quality, safety and efficacy may be demanding because it is difficult to ensure the comparability between production processes and batches for cell-based medicinal products (Salmikangas et al., 2015). However, a flexible case-by-case and risk-based approach has been applied in the legislation for ATMPs (Schneider et al., 2010).
During clinical transition, ATMPs provide treatments for diseases with limited or no effective therapeutics for which safety and efficacy over conventional treatments is still not shown by clinical trials. The risk-based approach of ATMPs is based on the identification of specific risks (or lack thereof) associated with the clinical use such as risks linked to quality, manufacturing and administration of the product. These risks may include unwanted immunogenicity, tumor formation, and ectopic tissue formation as well as contaminations from the production process and toxicity due to toxic degradation products of biomaterial components (Salmikangas et al., 2015).
Currently, four cell-based medicinal products have received marketing authorization in the European Union (Salmikangas et al., 2015). Holoclar was the first cell-based product (ATMP) containing stem cells that was recommended for approval in the European Union (EMA, European Public Assessment Report:
Holoclar, 2015). This product was developed to replace damaged cells on cornea epithelium and can be used in adult patients with moderate to severe limbal stem cell deficiency due to physical or chemical burns to the eye. The other three products include two for cartilage repair, i.e., ChondroCelect® (EMA, European Public Assessment Report: ChondroCelect, 2009) and MACI® (EMA, European Public Assessment Report: MACI, 2013), and one for treatment of metastatic castrate- resistant prostate cancer, i.e., Provenge® (EMA, European Public Assessment Report: Provenge, 2013). At the moment, clinical translation and commercialization of cell-based medicinal products are experiencing strong progress worldwide, although most developers in European Union originate from hospitals/academia or spin-off companies of those institutions (Salmikangas et al., 2015).
TiGenix NV is one of the leading European cell therapy companies with a commercialized cell-based product ChondroCelect® that uses expanded autologous chondrocytes for cartilage repair in the knee (www.TiGenix.com). Additionally, this company has a clinical stage pipeline of three ASC programs in which the applicability of allogeneic ASCs under investigation in clinical trials for the treatment of 1) complex perianal fistulas in Crohn’s disease (NCT01541579;
www.clinicaltrials.gov), 2) rheumatoid arthritis (NCT01663116;
www.clinicaltrials.gov) and 3) autoimmune diseases via intralymphatic administration (NCT01743222; www.clinicaltrials.gov). For treatment of complex fistulas, phase III clinical trials are currently ongoing. Based on the report from the phase II trial, a high efficacy of the product was demonstrated compared with other products in the closing of fistulas in Crohn’s patients. The trial also confirmed the strong safety profile of the product. TiGenix has reported that the cell product acts by controlled reduction of inflammation in the fistula and through the release of anti-inflammatory factors, which in turn promote natural fistula closure (www.TiGenix.xom). Moreover, a phase IIa clinical trial of refractory rheumatoid arthritis was completed in 2013, and the safety and tolerability of the product was confirmed with encouraging signs of efficacy. A phase I study has been conducted for autoimmune diseases. The results confirmed the safety, tolerance and the feasibility of intra-lymphatic cell administration, which enables the possibility of achieving efficacy at lower dosage. According to TiGenix, the intra-lymphatic administration system would further increase the safety and feasibility of expanded ASCs and it would significantly reduce the cost of goods (www.TiGenix.com). These and other novel cell products offer promise for future medicine, but time will reveal the final outcome of these complex medicinal products.