Prematurity in gene therapy.

Abstract

In 1972 Gunther S. Stent published an article in Scientific American entitled “Prematurity and Uniqueness in Scientific Discovery,” which advanced the thesis that certain scientific ideas were not appreciated in their time because their “implications cannot be connected by a series of simple logical steps to canonical or generally accepted knowledge” [1Stent G.S. Prematurity and uniqueness in scientific discovery.Sci. Am. 1972; 227: 84-93Crossref PubMed Scopus (191) Google Scholar]. Stent used the slow growth of molecular genetics during the nine years between the seminal publication of Avery, MacLeod, and McCarty [2Avery O.T. MacCleod C.M. McCarty M. Studies on the chemical nature of the substance inducing transfection of pneumococcal types.J. Exp. Med. 1944; 79: 137-157Crossref PubMed Scopus (1809) Google Scholar] and that of Watson and Crick [3Watson J. Crick F. Molecular structure of deoxypentose nucleic acids.Nature. 1953; 171: 737-738Crossref PubMed Scopus (8417) Google Scholar] to illustrate the prematurity of the central idea of the Avery et al. paper on the transforming properties of DNA. This year is the thirtieth anniversary of a paper that may be considered a founding statement of the field of human gene therapy, but also one that was also clearly premature with respect to the development of its field. That paper is “Gene Therapy of Human Genetic Disease?” by Theodore Friedmann and Richard Roblin [4Friedmann T. Roblin R. Gene therapy for human disease?.Science. 1972; 175: 949-955Crossref PubMed Scopus (509) Google Scholar], which was published in Science the same year as the Stent article. In this essay I shall attempt to explain why it took almost two decades for the ideas in that publication, and those of a few other contemporary thinkers, to lead to the intense interest in gene therapy that occurred in the 1990s. What were the major points of the Friedmann and Roblin paper? The first two pages described the contemporary status of the field of hereditary diseases, then of interest to a very small group of investigators, and the very limited efficacy of available therapies. They then discussed the possibility of genetic modification of eukaryotic cells mediated by transfer of DNA. Although the work until then had failed to demonstrate consistent modification of cells through uptake of exogenous DNA, the authors clearly thought that the studies from Renato Dulbecco's laboratory at the Salk Institute and his colleagues on oncogenic transformation of mammalian cells by the viral DNA of SV40 had important lessons for attempts to develop gene therapy [5Dulbecco R. Cell transformation by viruses.Science. 1969; 166: 962-968Crossref PubMed Scopus (68) Google Scholar]. These oncogenic viruses caused expression of one or more of their genes by integrating into the host genome by processes that suggested homologous genetic recombination—a mechanism that would be ideal if one had isolated normal genes, corresponding to those defective in a specific disease, for therapeutic attempts. Friedmann and Roblin, recent postdoctoral fellows from the Dulbecco laboratory, then discussed the contemporary work on isolating or synthesizing genes, reverse transcriptases, DNA transfections, artificial virus assembly, and related techniques from the Baltimore, Beckwith, Berg, Frankel-Conrat, and other laboratories as suggestive that the requisite techniques for DNAmediated gene therapy, using human genes rather than oncogenes, might soon be at hand. It is of significance, I believe, to explain this broad perspective to note that Friedmann was trained as a pediatrician as well as in several biochemistry research fellowships and Roblin had a recent doctorate in molecular genetics. However, despite the authors’ enormous enthusiasms for these studies at a time which, in retrospect, was to be the pre-dawn of eukaryotic molecular genetics, the second half of their paper turned to foreseeing the problems rather than the “unlimited potentials” of future gene therapy. These problems included both the technical and scientific ones, as well as, remarkably, the profound ethical issues. (To this end, the question mark in the title of the paper is of note, as is the subtitle: “Proposals for genetic manipulation in humans raise difficult scientific and ethical problems.”) The scientific problems included the need for targeting the specialized cell where the particular gene is active, the difficulty of regulating the expression of the gene, the problem of potential immunological reactivity, and the avoidance of deleterious side effects, including alteration of germ cell DNA. Based on the then-recently reported attempts to use injections of Shope papilloma virus to raise arginase levels in children suffering from hyperargininemia [reviewed in 6Friedmann T. Stansfield Rogers: insights into virus vectors and failure of an early gene therapy model.Mol. Ther. 2001; 3: 819-820Abstract Full Text Full Text PDF PubMed Scopus (24) Google Scholar], Friedmann and Roblin then proposed “ethico-scientific criteria” for any further attempts at gene therapy in human patients. The criteria they proposed as a guide to attempting studies in people were as follows: 1) there should be adequate biochemical characterization of the prospective patient's genetic disorder; 2) there should be prior experience with untreated cases; 3) there must be an adequate characterization of the DNA vector; 4) there should be extensive studies in experimental animals; and 5) there should be studies in cells of the prospective patient when possible. Friedmann and Roblin then turned from these very comprehensive and still clearly relevant scientific considerations to the need for ethical oversight of such work. They discussed questions of informed consent, review of experiments by hospital committees, and even public input to the whole process, perhaps by the funding agencies. Their concluding section began, “In our view, gene therapy may ameliorate some human genetic diseases in the future.” In retrospect, this important paper—without a shred of hype or panic—laid out quite fully the field of human gene therapy as it has developed in the last three decades, despite the several periods of irrational exuberance. It should be noted that a few others were also beginning to think about the possibility of DNA therapeutics at this time. E. L. Tatum, Marshall Nirenberg, and Stansfield Rogers wrote or spoke on this in the late 1960s. H. Vasken Aposhian, then at the University of Maryland School of Medicine, introduced the use of polyoma pseudovirions for DNA transfer and, in a very important 1970 paper in Perspectives in Biology and Medicine [7Aposhian H.V. The use of DNA for gene therapy—the need, experimental approach, and implications.Perspect. Biol. Med. 1970; 14: 98-109Crossref PubMed Scopus (25) Google Scholar], presented some of the ideas developed further in the Friedmann and Roblin paper. Indeed these discussions led Maurice Fox and John Littlefield to publish an editorial in Science in 1971, “Reservations concerning gene therapy,” which cautioned against undue clinical expectations and urged further basic research [8Fox M.S. Littlefield J.W. Reservations concerning gene therapy.Science. 1971; 173: 195Crossref Scopus (7) Google Scholar]. Despite the efforts of all of these early gene therapy proponents, the recognition of their foresight has been greatly mitigated in that they were premature, in Stent's concept, from both the scientific and the ethical points of view. It took the remainder of the 1970s and much of the 1980s for the requisite technical knowledge and social structures to be achieved that allowed the rest of the scientific and medical worlds really to have the canonical framework to relate to what these investigators saw so clearly then, so that a new field could develop. Readers of this journal will most likely be familiar with the scientific breakthroughs that occurred in the years immediately following the 1972 paper, which brought us the current “recombinant DNA” era and which made scientifically feasible the ideas of isolating and transferring the DNA of normal genes, which was really still a pipe dream in 1972. These obviously included the 1973 Cohen, Chang, Boyer, and Helling paper [9Cohen S. Chang A. Boyer H. Helling R. Construction of biologically functional bacterial plasmids in vitro.Proc. Natl. Acad. Sci. USA. 1973; 70: 3240-3244Crossref PubMed Scopus (1140) Google Scholar] on ligating DNA and the 1977 papers from Maxam and Gilbert [10Maxam A. Gilbert W. A new method for sequencing DNA.Proc. Natl. Acad. Sci. USA. 1977; 74: 560-564Crossref PubMed Scopus (5450) Google Scholar] and Sanger, Nicklen, and Coulson [11Sanger F. Nicklen S. Coulson A. DNA sequencing with chain-terminating inhibitors.Proc. Natl. Acad. Sci. USA. 1977; 74: 5463-5467Crossref PubMed Scopus (52658) Google Scholar] on DNA sequencing. But in addition, those years quickly saw the immense technical achievements of characterizing restriction enzymes, constructing DNA libraries, developing transfection methodologies, and a multitude of others which changed the scientific context of the 1972 article from fiction to possibility. It may be less appreciated that this period witnessed the birth of the social institutions that were also invoked by Friedmann and Roblin as necessary for this new field of human experimentation. These were particularly necessary before gene therapy could “take off” because the 1970s were still characterized by great public fear of genetics applied to human beings or human populations—a result of the early twentieth century eugenics movement [12Kevles D.J. In the Nme of Eugenics: Genetics and the Use of Human Heredity. 1995; Google Scholar] and the medical experimentation record of the Third Reich [13Nussenblatt R.B. Gottesman M.M. Symposium on medical research ethics at the millennium: what have we learned?.Perspect. Biol. Med. 2000; 43: 305-398Crossref Google Scholar]. A PubMed search of the scientific literature of the time finds frequent titles such as “genetic engineering” or “genetic manipulation,” almost always in a very negative context. The public discussion that resulted from the 1973 development of DNA recombination methods led to a self-declared (by scientists) moratorium on certain types of research, the 1975 Asilomar conference, and the creation of the NIH Recombinant DNA Advisory Committee (RAC) [14Fredrickson D.S. The Recombinant DNA Controversy, a Memoir: Science, Politics and the Public Interest. 2001; : 388Google Scholar, 15Schechter A.N. Perlman R.L. Symposium on science, ethics and society: the 25th anniversary of the Asilomar Conference.Perspect. Biol. Med. 2001; 44: 159-249Crossref Google Scholar]. I believe that these events, widely followed by the press, resulted after a period of heightened concern to the gradual lessening of public fears. This public discussion made the advent of clinical trials in gene therapy much less threatening in the 1990s than they would have been in the 1970s. In particular, in 1984 the RAC set up a Working Group on Human Gene Therapy, which soon issued guidelines: “Points to consider in the design and submission of human somatic-cell gene therapy protocols.” These guidelines were accepted by the NIH Director in 1990 as the basis, with concomitant FDA review, for vetting human protocols and are still so used. To general surprise, the NIH, which had long avoided direct responsibility for clinical research oversight, was effectively following the suggestion of the 1972 Friedmann and Roblin paper that “[p]rocedures to be used for gene therapy might also be controlled by the committees and organizations approving and funding research grants.” (In the 1990s, then-NIH Director Harold Varmus tried to eliminate this and other RAC functions and was rebuffed in the attempt.) In parallel to these public responses to the fears about genetic manipulation of organisms, this time period also saw the beginning of adoption of general policies concerned with informed consent and local institutional review of all clinical protocols. A 1966 paper by Beecher [16Beecher H.K. Ethics and clinical research.N. Engl. J. Med. 1966; 74: 1354-1360Crossref Scopus (1274) Google Scholar] had detailed many questionable experiments in published clinical studies and, along with other revelations, resulted in the United States Public Health Service issuing guidelines covering all federally funded research involving human experimentation that year. In 1974 the first national Commission for the Protection of Human Subjects was established, leading eventually to multiple other commissions and reports on this topic, most importantly the Belmont Report. The period from 1966 to 1976 is generally considered key in the development of standards, such as informed consent and institutional review boards, for safeguarding patients in clinical studies [17Rothman D.J. Strangers at the Bedside: A History of How Law and Bioethics Transformed Medical Decision-Making. 1991; : 303Google Scholar]—the ethical side of the constraints presented in 1972 as being necessary to allow gene therapy protocols to go forward. In 1980, several attempts at gene therapy in thalassemia patients in Italy and Israel were reported in the news media. These reports led to intense, largely negative, discussions in the medical and scientific literature, as well as the general press, about the scientific and ethical basis of these studies. It is remarkable how few of those commentators then proposing guidelines for future gene therapy studies appear to have known of the papers of Aposhian, Friedmann and Roblin, or any of their contemporaries, despite the prominent places of their publication. Although another decade passed before the next attempt at gene therapy in patients was reported, one can see in retrospect that a significant sea change in scientific and public attitudes was beginning to be evident at the time of this contretemps. The scientific technologies and social structures were now well developed to make this approach seem feasible. Yet another decade would pass before the first clinical successes were achieved, but the field of gene therapy was now moving from gestation to birth—not, however, without considerable pains and difficulties. But at least maturation as a scientific discipline—with a society (the American Society of Gene Therapy), a journal (Molecular Therapy), and all the other professional requisites—had occurred.