Ethical and legislative advances in xenotransplantation for clinical translation: focusing on cardiac, kidney and islet cell xenotransplantation

Genetically Modified Animal-Derived Products: From Regulations to Applications

Biotechnological advances applied to the generation of genetically modified (GM) animals have shown the potential to develop innovative solutions for different challenges in key areas such as agriculture and human medicine. Despite its enormous potential, the deployment of genetic modification in animals, and its subsequent commercialization, does not meet the same public acceptance as GM plant-derived products, which are currently widely adopted around the world. In this review, we highlight the main examples of GM and gene-edited animal-derived products already approved by the FDA and discuss the regulatory context inherent to such processes, including the risk-based assessment analysis based on a case-by-case evaluation. Moreover, cases of GM animals already approved by other jurisdictions around the world are also discussed.

Designer Organs: Ethical Genetic Modifications in the Era of Machine Perfusion

Gene therapy is a rapidly developing field, finally yielding clinical benefits. Genetic engineering of organs for transplantation may soon be an option, thanks to convergence with another breakthrough technology, ex vivo machine perfusion (EVMP). EVMP allows access to the functioning organ for genetic manipulation prior to transplant. EVMP has the potential to enhance genetic engineering efficiency, improve graft survival, and reduce posttransplant complications. This will enable genetic modifications with a vast variety of applications, while raising questions on the ethics and regulation of this emerging technology. This review provides an in-depth discussion of current methodologies for delivering genetic vectors to transplantable organs, particularly focusing on the enabling role of EVMP. Organ-by-organ analysis and key characteristics of various vector and treatment options are assessed. We offer a road map for research and clinical translation, arguing that achieving scientific benchmarks while creating anticipatory governance is necessary to secure societal benefit from this technology.

International Xenotransplantation Association (IXA) Position Paper on Kidney Xenotransplantation

Porcine kidney xenotransplantation for end-stage renal disease (ESRD) has reached the stage of clinical testing following major advances in donor pig genetic modifications and effective immunosuppressive strategies through decades of rigorous translational research. Reports of pig kidney xenograft survival beyond 1 year posttranplant in nonhuman primate (NHP) models justify optimism for its potential as an alternative to allotransplantation. In the United States, experimental transplantations of genetically engineered (GE) porcine kidneys into brain-dead subjects and a small number of ESRD patients have shown no evidence of hyperacute rejection and adequate pig kidney function for up to several months. Here we discuss pre-clinical/clinical results, infectious disease, ethical, and regulatory considerations, and propose evidence-based recommendations. For initial clinical trials in kidney xenotransplantation, we make the following recommendations: (i) transplantation with organs from a triple knockout (TKO) donor pig, preferably with added human transgenes, (ii) an immunosuppressive regimen with induction therapy to deplete T (and possibly B) cells, and maintenance therapy based on a cluster of differentiation (CD)40/CD154 co-stimulation pathway blockade, (iii) the patient should be fully acceptable as a candidate for allotransplantation but should be unlikely ever to receive an allograft. Patients aged 60-69 years (extendable to 40-75 years, if one of the criteria mentioned below is present), of blood group B or O, and with diabetes are most at risk in this regard. Other patients who could be considered are (i) those who have lost two or more previous kidney allografts from recurrent disease in the graft, (ii) those with broad human leukocyte antigen (HLA)-reactivity but no evidence of anti-pig antibodies, including swine leukocyte antigen (SLA), and (iii) those with failing vascular access. Clinical pilot studies in carefully and highly selected patients with no alternative therapy will provide the foundation upon which to base subsequent formal expanded clinical trials.

International Xenotransplantation Association (IXA) Position Paper on the History, Current Status, and Regulation of Xenotransplantation

Recent landmark clinical translation of xenotransplantation depended upon multiple innovations by the xenotransplant community, including the introduction of a variety of source pig genetic modifications, technical innovations, and novel immunosuppressive strategies, as well as the development of ethical and regulatory frameworks to support translation to the clinic. Each organ, tissue, or cell type intended for xenotransplantation will require application-specific preclinical milestones to be met in order to predict "success", as measured by ethical, safe, and efficacious translation to the clinic. Based on successful pre-clinical results and emerging evidence from decedent studies and initial clinical cases, evidence-based infectious disease, ethical, and regulatory considerations are emerging, and will be the foundations for the application-specific position papers that are currently under development. Here, we describe significant landmark events focusing upon safe and efficacious results underpinned by appropriate guidance documents developed over the past three decades that enabled recent translation to the clinic for heart and kidney xenografts. These steps have been undertaken over the past three decades by the xenotransplant community specifically led by the International Xenotransplantation Association (IXA) in consultation with the Transplantation Society (TTS) and the World Health Organization (WHO) to usher xenotransplantation to the clinic.

Patients' Information Needs for Informed Consent to Participate in First-in-Human Pig Kidney Xenotransplant Clinical Trials: A Mixed Methods Study

BACKGROUND

Transplant programs preparing to initiate first-in-human pig kidney xenotransplant clinical trials must be especially careful when obtaining participants' informed consent. Little is known about the kind of information patients want for making an informed decision about trial participation.

METHODS

We conducted semi-structured telephone interviews with waitlisted kidney transplant patients about information needs regarding participating in a first-in-human pig kidney xenotransplant trial, which guided development of a prototype consent form. Subsequent usability testing interviews sought patient feedback on the consent form. We analyzed qualitative data by thematic analysis and quantitative data by descriptive statistics.

RESULTS

Twenty-eight patients participated in semi-structured interviews; 16 patients participated in usability testing interviews. Most interview participants were male (68%, 56%), White (54%, 56%), or Black (36%, 31%), respectively. Interview participants identified five types of information needs: (1) the potential for infection contraction and transmission; (2) risks, benefits, and impact of xenotransplant trials; (3) xenotransplant clinical trial and recipient experience; (4) clinical trial logistics; and (5) the pig and its kidney. Usability testing participants suggested adding details to the prototype. Participants' preparedness to make a decision about participating in a xenotransplant trial increased after reviewing the prototype (12.5% vs. 31.3%, n.s.).

CONCLUSION

We identified multiple unique types of information patients desired to make informed decisions about pig kidney xenotransplant trial participation. Transplant programs initiating xenotransplant trials should be prepared to address patients' information needs to optimize informed decision-making for trial participation. The prototype consent form may support a patient-centered approach to informed consent.

Current Advances and Future Directions of Pluripotent Stem Cells-Derived Engineered Heart Tissue for Treatment of Cardiovascular Diseases

Cardiovascular diseases resulting from myocardial infarction (MI) remain a leading cause of death worldwide, imposing a substantial burden on global health systems. Current MI treatments, primarily pharmacological and surgical, do not regenerate lost myocardium, leaving patients at high risk for heart failure. Engineered heart tissue (EHT) offers a promising solution for MI and related cardiac conditions by replenishing myocardial loss. However, challenges like immune rejection, inadequate vascularization, limited mechanical strength, and incomplete tissue maturation hinder clinical application. The discovery of human-induced pluripotent stem cells (hiPSCs) has transformed the EHT field, enabling new bioengineering innovations. This review explores recent advancements and future directions in hiPSC-derived EHTs, focusing on innovative materials and fabrication methods like bioprinting and decellularization, and assessing their therapeutic potential through preclinical and clinical studies. Achieving functional integration of EHTs in the heart remains challenging due to the need for synchronized contraction, sufficient vascularization, and mechanical compatibility. Solutions such as genome editing, personalized medicine, and AI technologies offer promising strategies to address these translational barriers. Beyond MI, EHTs also show potential in treating ischemic cardiomyopathy, heart valve engineering, and drug screening, underscoring their promise in cardiovascular regenerative medicine.

Pig Xenotransplantation in Beta Cell Replacement: Addressing Challenges and Harnessing Potential for Type 1 Diabetes Therapy

This opinion paper evaluates the potential of porcine islets as a promising alternative in beta cell replacement therapy for Type 1 Diabetes (T1D), juxtaposed with the current limitations of human donor islets. It analyzes the compatibility of pig islets with human glucose metabolism, their prospects as a limitless and high-quality source of beta cells, and the unique immunogenic challenges they present in xenotransplantation. Additionally, the paper discusses the regulatory and ethical considerations pertinent to the use of porcine islets. By synthesizing current research and expert perspectives, the paper highlights both the opportunities and significant barriers that need addressing to advance pig islets as a viable therapeutic option. The findings advocate for a balanced and forward-looking approach to the integration of pig islets in T1D treatment, underscoring the need for continued research and dialogue in this evolving field.

Xenotransplantation Literature Update December 2023-June 2024

This updated report highlights significant developments in the field of xenotransplantation since December 2023. Over the past 6 months, there has been a notable increase in discussions regarding the feasibility of clinical trials, with particular emphasis on their progression and associated ethical considerations. This review presents the most pertinent findings from December 2023 to June 2024.