iPSCs as a source of therapeutic cells

iPSCs offer a promising platform for cell-based therapy and personalized medicine. It was a breakthrough in the field of regenerative medicine that was discovered by Shinya Yamanaka and his colleagues in 20062. His innovation of iPSCs led him to be honored with Nobel Prize in Physiology or Medicine 2012 (jointly awarded with Sir John B Gurdon)10. iPSCs derivatives are potential therapeutic cells that overcome the limitation of ethical issues and immune barriers associated with embryonic stem cells (ESCs)11. In a decade, iPSC became the brand source of Japan that flourished globally due to its potential benefits in disease modeling, regenerative therapy, drug screening, population health, and basic research 7. Known that iPSC-derived cells have been gaining high demand for therapeutic use in the clinic, it is essential to determine the genomic integrity that could be associated with forced reprogramming, selective pressure, and cultural adaptation12, 13. Several studies reported the possibility of recurrent genomic alterations in iPSCs, such as cytogenetic abnormalities and copy number variations (CNV) that raise the potential safety issues14, 15, 16, 17, 18. However, considerable evidence indicates that genomic heterogeneity in iPSCs was inherited from the parental cells carrying somatic mutations that have a random probability distribution. Such genetic variations are neither due to reprogramming nor does it lead to an increased number of de novo mutations. They reported that observed rare alterations in parental cells existed in low frequencies detected by sequencing-based approaches19, 20. These indicate iPSC reprogramming is not mutagenic that supports the safety considerations for product development and the therapeutic application of iPSC-derived cells in regenerative medicine, as illustrated in Figure 2. iPSC technology offers several advantages that can be used directly for the study of developmental biology, disease modeling, drug discovery, and cell transplantation9. Although iPSCs have benefits in regenerative medicine, they do have some disadvantages, as listed in Table 1.

Meanwhile, genomic instability (chromosomal alterations, CNVs, and mutations) in iPSCs are major concern in clinical applications, but the key factors governing the instability is still elusive9, 12, 18. Instability in iPSCs are similar to that seen in cancer cells, which have compromised cell therapy safety21. Such transient mutation can be reduced by using starting cell sources from the younger donor, avoiding oncogenic transcription factors, using non-integrating vectors system, chemical induction, and using antioxidants in the culture medium9, 12. Also, high-resolution SNP genotyping should use to classify mutation pattern, differentiate benign mutations, and those causing tumor formations to mitigate effects of these mutations on cell therapy22.

iPSC technology commercialization in Japan

In a short time, iPSC benefits were well-recognized for medicine in the global community. Thus, iPS Academia Japan, Inc. was established at Kyoto University on 25 June 2008 to govern the licensing of iPSC patents, and then promote iPSCs and related technology transfer to industry for its commercialization23. In 2009, the first license agreement was signed with ReproCELL and then with Cellular Dynamics International in 2010 for industrialization of technology to generate clinical-grade iPSC. Later, Fujifilm acquired Cellular Dynamics International (CDI) and invested significantly in stem cells to develop safer and efficient iPSC-based cell therapies23. Now, Fujifilm headquartered in Tokyo is the foremost leader in the field of regenerative medicine. Afterward, license agreements have been signed with numerous companies globally that include 110 in Japan, 46 in North America, 34 in Europe and 5 in Asia as of April 201924.

The fact that iPSCs could be generated from the adult cells without moral and ethical restrictions, these cells have been showing potential benefits and growing impact in medicine. Also, iPSC-based clinical studies have been receiving growing scientific interest and rapidly increasing in number worldwide. Thus, the commercialization of these cells represents the productive market in the field of regenerative medicine. Knowing the progressive impact on medicine, Center for iPS Cell Research and Application (CiRA) was established in 2008 to hold the intellectual property and to foster iPSC technology. Later, on 1 April 2010, CiRA was recognized as an independent institute at Kyoto University and Nobel Laureate, Shinya Yamanaka was appointed as a director25. Currently, CiRA grips basic iPSC technology patents in numerous countries, such as Australia, Canada, China, France, Germany, Ireland, Italy, Japan, Mexico, Singapore, Spain, Sweden, UK, and U.S. . 26. In addition, CiRA promotes the iPSC stock, iPSC-based cell therapy, and personalized medicine using iPS cells. Due to the high demand of iPSC-based clinical studies, the iPS Cell Stock for Regenerative Medicine project was started in 2013. Further, they established the Facility for iPS Cell Therapy (FiT) to support the distribution of clinical-grade iPSC to institutions for developing new medical therapies. Later in February 2017, Japanese pharmaceutical company, Sumitomo Dainippon Pharma Co., LTD. started the construction of manufacturing plant for regenerative medicine and cell therapy to accelerate iPSC research and the advancement of iPSC therapies into the clinic. The Sumitomo Dainippon Manufacturing Plant for Regenerative Medicine & Cell Therapy (SMaRT) was established in its Central Research Laboratories at Osaka, Japan. The manufacturing plant, which cost around 3.6 billion Yen, was completed on 1 March 2018. There onwards, the plant is engaged in generating iPSC derivatives for the treatment of age-related macular degeneration (AMD), retinitis pigments, spinal cord injury, and Parkinson’s disease . 27.

iPSC-based pretrial clinical studies in Japan

Thirteen years on, safety, efficacy, and potential benefits of iPSC derivatives has been proved in preclinical models. iPSC is an innovation of Japan, now leading for quality commercialization of iPSC-derivatives, and also becoming the world first nation to conduct pretrial clinical studies. Japanese researchers consider iPSC as an alternative source for therapeutic cells and artificial organs for diseases in which human tissues or organs are inaccessible to investigate. Recognizing their discovery and productive market, Japan government amended the Pharmaceutical and Medical Device Act (PMDA) in Nov 2013 opening door for regenerative medicine products. Revised PMDA act accelerated the iPSC-based therapy development by setting the fastest approval system for clinical trials in the world 28, 29, 30. In Japan, therapeutic cells derived from iPSCs have been transplanted into wet-type AMD and Parkinson’s disease, while more clinical studies are planned for other conditions. In recent years, the Japan government is setting to host world’s first pretrial clinical studies for several diseases and had approved physician-led clinical trials as listed in Table 2. The country’s scientists are now leading the way with clinical translation.

It is obvious that the challenges encounter when closer to clinical trials, but that also leads to the process for scientific discovery. In 2013, Japan took credit for historical movement in the race to develop iPS-based therapies and considered as a landmark year. A panel of Japan’s Health Ministry approved the project for autologous transplantation RPE sheets derived from iPSC in patients with wet-type AMD39. The project was conducted at RIKEN Center in Kobe, Japan, which was led by Masayo Takahashi of the RIKEN Center for Developmental Biology (CDB). RIKEN is the largest national scientific research institute supported by Japan’s Health Ministry and exclusively funded by the Japanese government40, 41. For the first patient enrolled, iPSC-derived RPE patch was transplanted in September 2014. One-year follow-up observation showed a good safety profile without significant improvement in visual acuity but stopped the progression of the disease42. However, transplant was halted in second patients due to genomic alteration in the patient’s iPSC-derived RPE cells, owing to the possible risk of aberrations in DNA copy numbers (deletions)42. Surprisingly, new regulation was implemented in regenerative medicine legislation of Japan in November 2014 that state, “the proposal for pretrial clinical study should be submitted from medical but not research institutions”. Thus, patient enrollment was immediately halted for RPE cell therapy in 2015. Later in 2017, allogenic HLA-matched iPSC-derived RPE cells were transplanted in the second patient43. Interestingly, Kyoto Hospital made an official announcement for establishment of special iPSC therapy center with 30-bed ward to conduct clinical studies for testing safety and efficacy of the iPSC therapies on volunteer patients. They aim to finish complete setup by September 2019 and planning to get approval for iPSC-based product by 2020.

Globalization of Japan iPSC and derivatives

iPSC-based therapies should be available to global population. Therefore, making availability of quality iPSC and derivatives become commercially important. To move forward with global clinical trials using iPSC-RPE for treatment of AMD, Healios K.K. established a patent license agreement with RIKEN in August 2011. They hold the exclusive worldwide license covering regenerative products that contain iPSC-derived RPE cells. Additionally, Healios establish collaboration with Sumitomo Dainippon Pharma for joint development of new therapies for wet-type AMD in Japan and also with National Eye Institute (NEI) for dry-type AMD in US/EU44, 45. Next, Cynata Therapeutic in joint development with Japanese company, Fujifilm received approval from the U.K. and Australia government in September 2016, to begin a clinical trial using allogenic iPSC-derived mesenchymal stem cells (MSCs) for treating graft-versus-host disease (GVHD)46. The world’s first clinical trial of an allogeneic cell product, “CYP-001” derived from iPSC begins in both the U.K. and Australia46. In this historic trial, Australian regenerative medicine company is testing product for GVHD47. GVHD is a transplant complication, in which the donor’s immune T cells (graft) attack the patient’s healthy cells or tissues (host) and damage them. iPSCs-derived MSCs were implanted, and two years post-implantation data from all 16 participants are expected to be completed by May 2020 to evaluate the safety and efficacy.

Japan iPSC banking and online database for global population

Patient-specific iPSCs are becoming challenging due to time-consuming to generate iPSC derivatives from patient somatic cells48, and chance of carrying somatic mutation into iPSCs49. Such challenges pose risk for missing threshold time for transplantation and effects of mutation inherited from parental cells. So, there is prerequisite of healthy donor for reducing the cost and rapid availability for cell therapy to the patients. To overcome the need of autologous cell therapy or immune rejection associated with human leucocytes antigen (HLA) mismatch50, CiRA is establishing the iPSC stock for medical use by recruiting the HLA homozygous (HLA-A, -B, and -D.R.) super donors. iPSCs derived from super donor somatic cells reduced the risk of rejection when transplanted in patient with heterozygous HLA for same haplotypes51. Currently they have 4 HLA homozygous iPSC lines, which cover 40% of Japan’s population. In addition, using genome editing technology, they estimated to generate 10-12 iPSC lines that will cover more than 90% of world population. “My iPS cells” project is next in the line to begins from 2025 as disclosed by Yamanaka during his presentation at ISSCR 2019 annual meeting held between 26-29 June 2019 at Los Angeles, US. Interestingly, Akitsu and his colleagues generated HLA-C retained iPSCs by allele-specific genome editing to make immune compatible iPSC that will benefit to most of the global population. First HLA class I pseudo-homozygous iPSCs were generated from HLA heterozygous donors. Then, both allele of HLA-A and HLA-B and mono allele of HLA-C were deleted to retain one HLA-C allele to generated HLA-C retained iPSCs which greatly expand donor compatibility with larger populations52.

Furthermore, with increase in number for iPSC research in global scenario, several iPSC online databases, such as eagle-I53, hPSC54, RIKEN BRC55, SKIP56 were established. Recently, CiRA professor Wataru Fujibuchi combined all those databases and released Integrated Collection of Stem Cell Bank Data (ICSCB) by MIACARM (Minimum Information About a Cellular Assay for Regenerative Medicine)57.ICSCB database provides the uniform, accurate and user-friendly data exchange that will facilitate the accelerated access to iPSCs data for research.