Unique problems for the design of the first trials of transplanting porcine kidneys into humans

Xenotransplantation: future frontiers and challenges

PURPOSE OF REVIEW

Recent advancements in genetic engineering have propelled the field of xenotransplantation from preclinical models to early compassionate use cases. As first-in-human clinical trials (FIHCTs) approach, we examine recent developments, ethical and regulatory challenges, immunological considerations, and the clinical infrastructure necessary for successful xenotransplantation trials.

RECENT FINDINGS

Expanded access transplants of pig hearts, kidneys, and livers have identified key challenges. Heart xenotransplants revealed risks of antibody-mediated rejection and zoonotic infections, while kidney xenotransplants suggest that patient selection, rather than immune rejection, may have caused failures. While there has been a report of auxiliary liver transplantation conducted abroad, profound thrombocytopenia poses an obstacle. As FIHCTs draw near, critical clinical challenges include determining the optimal donor genetic constructs and immunosuppressive regimens. Enrollment criteria and patient selection pose additional complexity, alongside ethical concerns such as lifelong zoonosis monitoring. Only a limited number of centers have the expertise needed to conduct these complex trials.

SUMMARY

Xenotransplantation holds great promise as a solution to organ shortages, but success in FIHCTs will require careful design, multidisciplinary collaboration, and strong infrastructure. Addressing immunologic, ethical, and patient selection challenges will be critical. With proper preparation, xenotransplantation could transform organ transplantation.

Transplant Patients' Perceptions About Participating in First-in-Human Pig Kidney Xenotransplant Clinical Trials: A Mixed Methods Study

First-in-human pig xenotransplant clinical trials may soon begin, which raises ethical concerns about patients' decision-making to participate in such trials. We assessed kidney transplant candidates' attitudes and hypothetical decision-making about participating in xenotransplant trials through semi-structured telephone interviews and an online survey. We analyzed qualitative data by thematic analysis and quantitative data by descriptive statistics. Twenty-eight patients participated in interviews; 142 patients participated in the survey. Most interview and survey respondents were male (68%, 56%), White (54%, 61%), or Black (36%, 22%). Although interview participants appreciated xenotransplantation research's potential to advance science, they expressed concerns about infection transmission and graft function. Few survey respondents were willing to participate in a pig kidney trial to test the safety of pig kidneys (12.6%) or pig kidney function (16.9%). Interview participants would be more likely to participate in a first-in-human pig kidney trial if receiving a human kidney was unlikely and their health status declined. Willingness would also depend on how long the pig kidney would function. Most interview participants were receptive to long-term monitoring, but not to family monitoring. Transplant programs planning xenotransplant trials should anticipate these types of concerns for optimizing human subject protections and conducting a robust informed consent process.

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.

Xenotransplantation Clinical Trials and Equitable Patient Selection

Xenotransplant patient selection recommendations restrict clinical trial participation to seriously ill patients for whom alternative therapies are unavailable or who will likely die while waiting for an allotransplant. Despite a scholarly consensus that this is advisable, we propose to examine this restriction. We offer three lines of criticism: (1) The risk-benefit calculation may well be unfavorable for seriously ill patients and society; (2) the guidelines conflict with criteria for equitable patient selection; and (3) the selection of seriously ill patients may compromise informed consent. We conclude by highlighting how the current guidance reveals a tension between the societal values of justice and beneficence.

Close contacts of xenograft recipients: Ethical considerations due to risk of xenozoonosis

With decades of pre-clinical studies culminating in the recent clinical application of xenotransplantation, it would appear timely to provide recommendations for operationalizing oversight of xenotransplantation clinical trials. Ethical issues with clinical xenotransplantation have been described for decades, largely centering on animal welfare, the risks posed to the recipient, and public health risks posed by potential spread of xenozoonosis. Much less attention has been given to considerations relating to potentially elevated risks faced by those who may care for or otherwise have close contact with xenograft recipients. This paper examines the ethical and logistical issues raised by the potential exposure to xenozoonotic disease faced by close contacts of xenotransplant recipients-defined herein as including but not limited to caregivers, household contacts, and sexual partners-which warrants special attention given their increased risk of exposure to infection compared to the general public. We discuss implications of assent or consent by these close contacts to potentially undergo, along with the recipient, procedures for infection screening and possible quarantine. We then propose several options and recommendations for operationalizing oversight of xenotransplantation clinical trials that could account for and address close contacts' education on and agency regarding the risk of xenozoonosis.

Revisiting the Use of Ulysses Contracts in Xenotransplantation

BACKGROUND

Xenotransplantation clinical trials may begin soon. A persistent risk of xenotransplantation, known for decades, is the possibility that a xenozoonotic infection could be transferred from a xenograft to its recipient and then to other human contacts. Because of this risk, guidelines and commentators have advocated for xenograft recipients to agree to either long-term or lifelong surveillance mechanisms.

METHODS

For the past few decades, one solution that has been proposed to ensure that xenograft recipients will comply with surveillance protocols is the use of a heavily modified Ulysses contract, which we review.

RESULTS

These contracts are most often used in psychiatry, and their application to xenotransplantation has been espoused several times with minimal criticism.

CONCLUSIONS

In this article, we argue against the applicability of Ulysses contracts in xenotransplantation based upon (1) the telos of the advance directive that may not be applicable to this clinical context, (2) the suspect nature of enforcing Ulysses contracts in xenotransplantation, and (3) the ethical and regulatory hurdles that such enforcement would require. Although our focus is on the US regulatory landscape in preparation for clinical trials, there are applications globally.