SAFETY AND JUSTICE IN FUTURE CLINICAL RESEARCH WITH HUMAN EMBRYONIC STEM (ES) CELLS
Frequently Asked Questions
A: The Working Group on Criteria for Cell-Based Therapies was created by the Johns Hopkins University Program in Cell Engineering, Ethics and Public Policy(PCEEPP), with a grant from the Greenwall Foundation, to evaluate the "next generation" of ethical issues likely to face research with human embryonic stem cells. The panel of experts in science, ethics and law focused on issues of safety -- for future participants in clinical research with the cells or their derivatives -- and justice -- or how make access to clinical trials and, once those are complete, therapies using the cells as fair and equitable as possible. The working group completed their project and is publishing their conclusions in two papers in November 2003.
A: The Working Group was composed of eight internationally known experts from outside Hopkins, the scientists and ethicists in the PCEEPP at Hopkins and one additional Hopkins faculty member.
A: Through a project funded by the Greenwall Foundation, individual meetings, group discussions, two full working group sessions, and continual dialogue, the Working Group identified and evaluated the next generation of ethical issues likely to face human embryonic stem cell research. The issues identified by the panel members were largely related to safety of eventual clinical trials and justice in biological access to ES cell based therapies should they prove useful. Concerns about safety ranged from basic research questions that are still unanswered to the risk of cross-species (mouse to human) infections. Biological access concerns revolved around how to design collections of human ES cells to ensure that all benefit from clinical research and that patients have fair biological access to new ES cell based therapies once developed.
A: The panel reports their conclusions on safety in the November issue of Fertility and Sterility. First, there are many fundamental aspects of human ES cell lines that need to be understood before the cells could be used in people. Among the concerns identified by the panel include the risk the transplanted cells might form tumors, travel to the wrong place in the body, or become undesired cell types. Decades of experience with other tissue transplants also demonstrate that the risks of rejection and so-called graft versus host disease (GVHD) -- reduced by properly "matching" the transplanted tissue and the recipient -- are also likely to affect some applications of human ES cell transplants. Basic science investigations should provide some answers to these concerns in the coming years.
Second, the panel evaluated whether federally approved human ES cell lines, which are the only ones that can be used in federally funded research, are suitable for use in humans. The panel's answer was no. A major issue was that all of the approved cell lines have been grown on mouse cells, which may have contained a virus or other infectious agent that could now be hiding in the human ES cell lines. If so, transplantation of these cell lines into people could introduce a new, difficult-to-treat infection because people's immune systems likely wouldn't be prepared to fight off a virus normally found only in mice. If human ES cells were ready to enter clinical trials and the approved cell lines were the only ones available to treat incurable and fatal conditions like Lou Gehrig's disease or Parkinson's disease, the risk of creating a new infection might be worth taking. However, new cell lines have been created that have never been exposed to mouse cells, but these newer lines would not qualify for research with federal funds because they were created after 9 p.m. Eastern Time, Aug. 9, 2001 -- President Bush's cut-off for federal approval.
A: These conclusions are reported in the November/December issue of The Hastings Center Report. Even though clinical trials with human ES cells, or more specialized cells obtained from them, are still many years away, the panel tried to determine the fairest, or most just, way to conduct clinical trials and therapies after the trials conclude. The panel members all agreed that clinical trials, the first attempts to see if human ES cells are safe and effective, should happen as fast as possible once they are ready to begin.
Speed is obtained, in part, by being able to rapidly enroll participants into the clinical trial. If "matching" human ES cells and the recipient is important for these clinical trials, as currently expected, then the available ES cell lines should match as many people as possible. The panel recommends creating an ES stem cell "bank" that would match the most Americans with the fewest number of cell lines. Because the biology of "matching" depends largely on ancestry, the resulting bank would primarily match white Americans, so cell lines representing minority groups should be purposely included, the panel said.
Matching depends on the combination of a person's versions of proteins called human leukocyte antigens (HLA), so the cell lines would need to contain common HLA combinations. There are many, many versions of each of the HLA proteins, and many combinations of those versions. Each racial or ethnic group has its own set of most common HLA "types," and sometimes there's little overlap between groups. For example, white Americans and Asian-Americans share none of the other's top-25 HLA types.
Once proven useful, human ES cell lines should be available equitably to people of all ancestry in the United States, the panel decided. Most panel members concluded that ES cell lines in a "bank" for therapy should match equal percentages of each ancestry group, but three panel members had slightly different opinions. (Dan Brock preferred a modified version of what the panel called the "equal chances" strategy; Mark Greene felt it was premature to make recommendations related to a therapeutic bank; and LeRoy Walters felt that an option was needed that didn't compromise efficiency as it supported justice.)
Here as well, the policy limiting federal funding to only those cell lines established prior to 9 p.m. ET, August 9, 2001, conflicts with the panel's recommendations. The limited number of approved cell lines and their derivation from embryos created for in vitro fertilization likely point to their HLA diversity being inadequate, the panel said.
A: Panel members recognized the fundamental moral tension at the heart of current political debates about stem cell research. This tension comes from balancing the value of early human life -- the embryo destroyed to obtain stem cells -- and the potential to save the lives of seriously ill children and adults through development of cell-based therapies. While this basic dilemma has received a great deal of attention, it is unlikely to be solved for a broad population.
Instead, the panel wanted to be able to focus on the next set of ethical dilemmas likely to face research with these cells, while keeping in mind this fundamental tension. The panel members believe that research with human ES cells will continue in the United States and overseas, and that there is considerable value in publicly considering and discussing ethical issues before being faced with the actual situation.
The panel took care to note that in many instances, satisfying ethical concerns related to safety and justice for clinical trials of these cells once again require consideration of the tension between embryos' moral status and developing and testing potential new therapies. For example, the panel's recommended designs for research and therapeutic "banks" of human ES cells that satisfy requirements of justice would clearly mean deriving new stem cell lines. Quite possibly, establishing the banks quickly might also mean needing to create embryos in order to obtain the HLA types necessary (rather than relying on those types to appear in embryos donated by couples who had undergone in vitro fertilization). Both of these implications of the panel's recommendations would be problematic for those morally opposed to the creation or destruction of human embryos for any reason.
A: While the panel members discussed research that needs to be completed before clinical trials would be indicated, they did not come to any conclusion about how long such research would take. However, John Gearhart, a member of the Working Group, believes that within three to five years clinical work with human ES cells will be occurring somewhere in the world. While the publication rate of papers involving human ES cells is much slower than the corresponding period of time after mouse ES cells were first announced (based on an analysis by James Thomson at the University of Wisconsin), it is anticipated that the rate will increase rapidly over the next few years as research that started a year or so ago is ready to be reported.