More Gray Matter: Parkinson's Disease and Gene Transfer

Several groups are pursuing gene transfer strategies against Parkinson's disease. No small task, because for these approaches to work, investigators have to deliver vectors deep inside the brain using surgery. I have previously written that early phase studies using surgical delivery press the boundaries of acceptable risk, because patients can generally manage their disease adequately- though far from completely- with dopamine replacement, and study participation entails nontrivial surgical risks (by my calculations, about 0.5% chance of mortality, depending on the approach).

In the December issue of Lancet Neurology, Marks et al report results of a phase 2, sham controlled trial of CERE-120. The results were negative. That is, for the main measure in the study, improvement in symptoms at 12 months, patients receiving CERE-120 did not do significantly better than patients receiving sham. On the other hand, the product did not raise any major safety issues, apart from a hemorrhage during surgery in one patient.

The team performing the study has emphasized several "positive" outcomes. For one, patients receiving CERE-120 generally responded better than patients in the sham arm (though not significantly better- that is, differences may be attributable to chance). And on a secondary endpoint- response at 18 months- patients receiving CERE-120 did indeed perform significantly better. So did Ceregene score against Parkinson's disease? In an accompanying commentary, French Neurologist Alim Benabid says "the findings... provide the first clinical evidence of a clinical benefit of gene therapy in Parkinson's disease."

I ain't no neurologist, but I say: hold on a minute. When researchers start trials, they pick primary endpoints based on where they think they are most likely to succeed. In this case, the researchers picked improvement at 12 months, rather than at 18 months. From the looks of it, they backed the wrong horse- patients did significantly better at 18 rather than 12 months. What does this tell us? Success in a secondary endpoint might have occurred by chance, and the fact that researchers were unsuccessful on their primary endpoint indicates that they do not yet understand enough about their system to pick the "right" endpoints. So I see this as symptomatic of scientific uncertainty rather than a glimpse of medical destiny. [[One other issue to consider: it is possible that surgery itself (rather than gene transfer) may have caused symptomatic improvements.]]

The study was well reported and provides, yet again, evidence of the utility of sham comparator arms in studies involving Parkinson's disease. One disappointing feature, however, is that the authors did not report whether patients or clinicians could correctly guess their treatment allocation just prior to unblinding. Without this, it is difficult to exclude the possibility that any difference between groups- even at 18 months- was due to "placebo effect." (photo credit: Vin6, 2007)

Icarus, again: Adversity in another Gene Transfer Trial

Two weeks ago brought good news and bad news for gene transfer. First the good news. New England Journal of Medicine beatified a new gene transfer strategy for Wiskott-Aldrich Syndrome (WAS). WAS is a primary immunodeficiency that primarily affects boys. It is thus in the same family of disorders that have been, in varying degrees, successfully addressed using retroviral gene transfer. Like other immunodeficiencies, this represents relatively low hanging fruit for an approach like gene transfer, because scientists can access and target stem cells, and because corrected cells should be at a selective advantage for survival compared with uncorrected cells.

The NEJM article reported clinical, functional, and molecular outcomes for two boys in a trial based in Germany. Briefly the two boys were given a type of chemotherapy (in order to make space for genetically corrected cells), and then transplanted with “corrected” blood stem cells. The corrected blood stem cells contained a viral vector similar to those used in previous gene transfer trials of primary immune deficiency. The team saw: 1) stable levels of genetically corrected stem cells that expressed the WAS protein (indicating the genetically modified cells “took,” and produced WAS; 2) recovery of the function of a variety of immune cells; 3) reduction of disease symptoms, including improvement of eczema, and reduced severity of infections.

The article exhaustively ruled out events that have occurred in other, similar gene transfer trials in which children developed leukemias from the vector. Now the bad news. The same day NEJM published the results, American Society of Gene and Cell Therapy (the largest professional society devoted to gene transfer) released a statement saying that the German team just announced “a serious adverse event in a gene therapy trial for Wiskott-Aldrich syndrome (WAS)”- one of the ten children in the German trial developed a leukemia.

And so continues the saga of gene transfer: three steps forward, one back. (photo credit: vk-red 2009)

Ark, Troubled Waters, and Rainbows for Gene Transfer

This morning I awoke to a news report by National Public Radio's Joe Palca on promising developments in gene transfer. In it, Palca provided a good account of the field's travails, as well as some encouraging developments in the last few years. The story ended with the prediction that the coming "months and years" would bring landings for more common disorders like AIDS and cancer.

Coincidentally, the just released March issue of Nature Biotechnology ran a report on a front-runner for gene transfer commercialization: biotechnology company Ark Therapeutics gene transfer gliobastoma product Cerepro. The application for licensure of this product in Europe was unsuccessful (press release here). Recall that, last June, I described what seemed like unimpressive results from a phase 3 trial that were reported at an annual meeting of the American Society of Gene Therapy. Apparently, European drug regulators weren't impressed either (they cited flaws in trial design, including a small sample size and unconcealed allocation; Ark has asked the agency to re-examine their application).

But for those awaiting the first commercialization of a gene transfer product in a country with a robust drug regulatory system, there is still some indication that the rains may be subsiding: according to the report in Nature Biotechnology, Amsterdam Molecular Therapeutics has filed with EMEA for marketing authorization of their AAV product for a rare hereditary disorder, LPL deficiency; the company will soon file in Canada as well (the disorder is more prevalent in Quebec) (photo credit: Occhiovivo 2007)

Annus Mirabilis for Gene Transfer

Time to review the year 2009 for cutting edge clinical research. For the field of gene transfer, it has been an annus mirabilis: a year that has seen very encouraging results in a wide variety of human clinical studies, as well as preclinical studies. Indeed, I regret that this blog has only been able to cover a few of the former, and very little of the latter. Here are a few highlights from clinical studies:

• in March 2009, Italian researchers reported major clinical improvement in eight of ten children participating in a gene transfer study involving ADA-SCID. [discussed here]

• in June 2009, researchers at Penn / Scheie Eye Institute reported very encouraging outcomes in three children with hereditary blindness, including evidence of visual recovery. [discussed here]

• in September 2009, researchers reported "marginal effectiveness" in preventing HIV infection for a gene transfer-based vaccine. These findings from this trial (the "RV144 trial") were unexpected after abysmal trial results involving a related strategy (the STEP trials). These are the first encouraging results from any HIV vaccine study conducted to date. [described here and here].

• in November 2009, researchers at Paris-Necker reported very encouraging outcomes in two children with adreno leukodystrophy who received a vector derived from lentiviruses [discussed here]

The decade began with a series of very inauspicious clinical outcomes in gene transfer, and a sharp abatement in the volume of clinical testing. The decade ends with several highly encouraging results from well designed and executed clinical trials. (photo credit: Xavier Luque 2009)

More on Lenti's, Gene Transfer and Adrenoleukodystrophy

(...continued from the previous post). There are several features that make the recent Adrenoleukodystrophy (ALD) gene transfer study noteworthy.

1- A New Viral Vector Debuts: this is the first successful application of HIV-derived viruses in gene transfer (lentiviruses). These vectors have various advantages over retroviruses used in other protocols. One is that, in theory, at least, they are supposed to be safer. Previous trials of the same team (different disease) involving retroviruses triggered leukemia-like disorders in several volunteers. In this study, the authors do not detect any evidence that cells are poised to cause a malignancy. However, in a post this summer, I noted that another trial involving thalessemia and lentiviruses did, indeed, detect clonal enrichment. And the ALD study enrolled only two patients- if there were going to be safety problems detected, they'd need to be massive to be detected in so small a sample of patients. Thus, despite the encouraging findings in the ALD study, the safety of lentiviral gene transfer remains to be firmly established.

2- Prior Animal and Clinical Experience are Successfully Integrated: here is one instance where favorable clinical outcomes were achieved on the basis of limited preclinical evidence. Specifically, the authors previously tested their approach in mice, but because rodents do not develop the same pathology as human beings, they were uncertain whether the gene correction would be sufficient to correct the disorder in human patients. These animal studies were bootstrapped with extensive experience with bone marrow transplantation in children with ALD. Rarely is this transition from rodents into clinical applications so successful. All the more surprising- this is occurring within the realm of central nervous system disorders, which have a particularly high rate of failed drug development.

3- Patients in the Service of Science: This study will no doubt be perceived as a story of "science in the service of patients:" a team of clinicians applying cutting edge discoveries to do the best they can for their patients. But it is as much- perhaps more- a story of patients in the service of science. The study is notable for how well it used the occasion of ALD to make more fundamental discoveries. For example, in a "Perspective" piece that accompanies the published trial, Luigi Naldini describes this as what "may be a first glimpse of live [generation of new blood and immune cells at the level of DNA]." Naldini also notes how the study developed and applied new techniques for ruling out clonal dominance that "will likely become a gold standard." Also intriguing is the hint that this approach may be applicable for other disorders involving the central nervous system, and the finding that only a small amount of gene correction is needed to arrest the pathology. (photo credit: photobunny 2007)

Gene Transfer and Adrenoleukodystrophy: There Will Always Be Paris

Last week's Science magazine reported what seems likely to count as one of gene transfer's greatest clinical successes to date: stabilization of adrenoleukodystrophy in two boys receiving genetically modified blood stem cells. Preliminary results of this study had been presented at this summer's American Society of Gene and Cell Therapy meeting.

Adrenoleukodystrophy (ALD) is a rare hereditary brain disorder in which a deficiency in a gene, ABCD1, causes degeneration of tissues (myelin) that insulate cells in the central nervous system. The disease is familiar to many because of its most famous patient, Lorenzo Odone, whose story was featured in the movie Lorenzo's Oil. Untreated, ALD is invariably fatal.

Because myelin cells originate from blood stem cells, researchers had previously used bone marrow transplantation to successfully halt progression of demyelination in ALD patients. However, bone marrow transplantation has two severe limitations: many patients lack matched bone marrow donors; second, even when a matched donor is available, the procedure is burdensome and risky.

In this most recent study, researchers at Hôpital Necker in Paris transplanted genetically modified bone marrow cells into two Spanish boys who lacked matched bone marrow donors. The boys were also given myeloablative conditioning- a type of chemotherapy that increases the likelihood that genetically modified cells will repopulate the bone marrow. The Science report showed:

1- genetically modified cells did, indeed, survive and were maintained at stable levels for two years.

2- the modified cells expressed the therapeutic gene, ABCD1, again for two years.

3- brain demyelination was halted after 14 months- the timing is similar to what would occur for patients receiving bone marrow transplantation.

4- the two boys did not appear to decline on various measures of neurological or verbal tests, as would almost certainly have occurred with the natural course of ALD.

5- the authors did not detect "clonal dominance" in their modified cells– that is, evidence that genetically modified cells were poised to cause a malignancy.

In an accompanying editorial, Luigi Naldini calls this study a "Comeback for Gene Therapy," describing it as a "long-sought rewarding achievement in the field of gene therapy." In my next post, I will discuss some implications, interpretations, and other interesting dimensions of this very encouraging study (photo credit: tgif28, chalk graffiti at Hopital Necker, 2009)

Safe Harbor? Leukemia, Gene Transfer, and Lentiviral Vectors

A few further observations from the American Society of Gene Therapy Meeting...

A recurrent theme in this blog is the frequency with which novel research fields encounter safety problems that confound laboratory predictions. One presentation at the 2009 ASGT meeting brought this point home.

Recall my entry on May 12 discussing various refinements to retroviral gene transfer that are aimed at reducing risk of malignancy. Researchers have postulated that HIV-derived lentiviral vectors might not cause the same leukemia-inducing mutations as retroviruses, and RAC recently passed a favorable judgment on a lentiviral vector gene transfer protocol for X-SCID.

How confident can we be that lentiviruses will not trigger leukemias? Some indication is provided in a May 2009 review by John Rossi in Molecular Therapy. It concluded "overall, the results of these [safety] analyses [of lentiviral vectors] are highly encouraging..." but "clearly, more careful analyses... are warranted in appropriate animal models."

At ASGT, researchers from France reported preliminary results from a phase 1 trial testing lentiviral vectors in patients with beta-thalassemia. The study involved two patients. Though no malignancies have been detected, tests in one patient showed signs that some cells were repopulating the patients blood much faster than others (what researchers call "clonal dominance"). This is a worrisome signal, as it might indicate a premalignant state.

The lessons here are not that lentiviral vectors are unsafe (we don't know whether this will lead to a malignancy), or that such vectors shouldn't be used in human beings (we can't say anything yet about the risk-benefit balance). Instead, I think the lesson is: in novel research areas, be very wary of anyone who makes emphatic claims that their system provides safe harbor. Expect the unexpected. (photo credit: dark matter, 2005)

Mice- Three Different Ones: Towards More Robust Preclinical Experiments

One of the most exciting and intellectually compelling talks thus far at the American Society of Gene Therapy meeting was Pedro Lowenstein's.  A preclinical researcher who works on gene transfer approaches to brain malignancies (among other things), Lowenstein asked the question: why do so many gene transfer interventions that look promising in the laboratory fail during clinical testing? His answer: preclinical studies lack "robustness."

In short,  first-in-human trials are typically launched on the basis of a pivotal laboratory study showing statistically significant differences between treatment and control arms. In addition to decrying the "p-value" fetish- in which researchers, journal editors, and granting agencies view "statistical significance" as having magical qualities- Lowenstein also urged preclinical researchers to test the "nuances" and "robustness" of their systems before moving into human studies.

He provided numerous provocative examples where a single preclinical study showed very impressive, "significant" effects on treating cancer in mice. When the identical intervention was tried with seemingly small variations (e.g. different mouse strains used, different gene promotors tried, etc.), the "significant effects" vanished.  In short, Lowenstein's answer to the question of why so many human trials fail to recapitulate major effects seen in laboratory studies is: we aren't designing and reviewing preclinical studies properly. Anyone (is there one?) who has followed this blog knows: I completely agree. This is an ethical issue in scientific clothing. (photo credit: Rick Eh, 2008)

Yellow Light on Gene Transfer Studies

Among the greatest heartbreaks in the field of gene transfer have been problems encountered in trials involving a rare, hereditary immune disorder, X-SCID (known popularly as "Bubble Boy" syndrome).  As is well known, a team of researchers based in Paris– and then in London– successfully reversed severe immunodeficiencies in 20 or so children using retroviral gene transfer starting around year 2000.  Shortly thereafter, however, the Paris team began observing rare leukemic disorders that were causally related to the gene transfer. To date, the Paris team has reported 4 cases of leukemia, with one leading to death. The London team has reported one leukemia.

In response to these events, the U.S. Recombinant DNA Advisory Committee (RAC) recommended that investigators only use retroviral gene transfer in the most severe situations– namely, where patients are ineligible for even high risk alternative care options like haploidentical stem cell transplantation.  RAC's recommendations were stricter than those in the U.K., which allowed children to enter a study even if they were candidates for haploidentical transplants.  

As reported in the current issue of Molecular Therapy, the RAC recently decided to liberalize its recommendations, allowing retroviral gene transfer in children who are eligible for halploidentical transplantation. RACs recommendations are still somewhat stricter than those of the UK, because the former recommends against retroviral gene transfer in children who are candidates for haploidentical transplantation but under 3.5 years age (children in this category respond better to haploidentical transplants). RAC additionally supported a similar trial involving a different vector that integrates its genome into the host's (lentiviral vectors, which are derived from HIV).

Is this gentle liberalization of standards justified?  Some will argue that the benefits of haploidentical transplantation are variable and undependable, and that since initial leukemias have been reported, researchers have made progress in improving the safety of their vectors. All this might be true, if one were evaluating this as a clinical judgment.

However, the judgment is better viewed through the lens of research rather than therapy. Though laboratory testing indicates that new retroviral and lentiviral vectors are safer than the old ones, there remain substantial uncertainties. For example, current assays for determining the oncogenicity of integrating vectors are not well worked out. Neither the new retroviral vectors nor lentiviral vectors have been used in blood stem cell gene transfer in a pediatric population. The effect of lentiviral vectors on gene sequences near their integrating sites remains poorly understood. In short, the null hypothesis of new trials is that these new vectors are no better than the old ones.

What's the safest way to refute this null hypothesis and confirm what many think, on laboratory evidence, will be the case? In my view, the safest approach– for patients as well as the field in general, which stands to lose much from another major toxicity– is to begin with the most narrow medical indication possible, which means excluding children who stand a chance of benefiting from standard (albeit suboptimal) care.  (photo credit: Jamelah 2007)

Toxic Waste?

Before testing new drugs in human beings, drug developers must first perform a series of safety tests in animals. Unfortunately, these preclinical toxicology studies are typically protected as trade secrets. In fact, many countries have laws that specifically bar drug regulators from releasing preclinical toxicology data submitted by drug developers.

Unless you take the extreme view that animal experimentation raises no ethical concerns, this represents a terrible waste of animals and a failure of researchers to enable the sacrifice of animals to enrich the bank of human knowledge. As an afterthought, it's worth mentioning that this also comes with certain opportunity costs for human beings, since such nondisclosure potentially 1-frustrates efforts by researchers to improve their knowledge about drug safety, 2- results in duplicative expenditure of human resources.

It needn't be this way, and the field of gene transfer shows one modest way toxicology data could be published and pooled. Since it was established, the National Gene Vector Laboratories, at Indiana University, have invited gene transfer researchers to submit summary data on toxicology studies to their database (the laboratory recently was eliminated and replaced with the National Gene Vector Biorepository-- NGVB for short). As described by NGVB director Ken Cornetta and project coordinator Lorraine Matheson in Molecular Therapy (April 2009), the database is intended to provide a resource for researchers so that they can cross-reference toxicology experiments in their FDA filings and avoid duplicative studies. The authors also envision the database as a resource for grant reviewers.

The database contains 27 toxicology studies in all. This number seems small when you consider the volume of gene transfer studies pursued since the database was established. The fact that every institution that has contributed to the database is a nonprofit suggests that the private sector has not taken an interest in this worthy resource. One question I have is how many private companies have used data contained in this databank in their FDA filings (this should be easy to determine).

These questions aside, other fields should create similar resources to pool data and create opportunities for data linkage. I would go so far as to say that ethics policies should require that, at a minimum, such summary data be published on a public database. The failure to do so seem a toxic waste for animals, scientists, funders, and patients alike.  (photo credit: drp, Waste Not, 2004)

Centralized Revue

In the most recent issue of Molecular Therapy, U Penn researcher Hildegrund Ertl provides a strong and eloquent defense of the Recombinant DNA Advisory Committee (RAC).  RAC was initially formed to evaluate the safety of studies involving recombinant DNA. In the last decade, however, its most visible function has been to provide advise to researchers pursuing novel gene transfer protocols in human beings.

Many researchers resent RAC, viewing it as yet another layer of oversight for their clinical studies. Understandably, they question whether it makes sense to have a separate review track for gene transfer. Other scientists and ethicists might question whether gene transfer is so exceptional as to be singled out for separate review, but would nevertheless argue that the RAC model should be extended to other ethically contentious areas of medical research. Nevertheless, the RAC model of centralized review of trial protocols has yet to be extended to comparably novel and contentious human clinical research areas like cell transfer, embryonic stem cell research, or tissue engineering.

Ertl provides a clear and persuasive description of RAC's role in improving gene transfer trial safety, enhancing scientific value of studies, and ensuring appropriate informed consent practices. But the structure of her argument embeds three assumptions that, in my view, need to be questioned.

1- Why demand solid preclinical evidence? Ertl answers "if such data are not available, the risk outweighs the potential benefit for human volunteers– and that is not acceptable." I would argue that preclinical evidence is of greater use in improving the scientific value of clinical studies. 

2- How are risks justified in early phase studies? In the above quote, Ertl seems to suggest the answer is therapeutic benefit for the volunteer. In my view, risks in first-in-human trials are justified by the potential for scientific gain, not direct medical benefit.

3- What is the purview of ethics? Ertl, like many others, partitions "technical" concerns like study validity / value / preclinical evidence from "ethical" concerns like informed consent and conflict of interest. But why is the former any less ethical than the latter, given that technical questions implicate problems of risk-benefit balance and the ultimate ends of research. In my view, there is no clear division between the technical and ethical, and few if any decisions in designing and executing clinical protocols are devoid of ethical content. (photo credit: 416style, 2005)

Departing Milano Stazione? ADA-SCID and Gene Transfer

Greetings after a hiatus for teaching, grants, committees, book deadlines, wiping runny noses, and more. Much has happened since my last posting, and in the next two or three weeks, I hope to catch up.

First item on the agenda is a Jan 29 report in New England Journal of Medicine (NEJM) describing successful reconstitution of immune function in eight of ten children receiving gene transfer for adenosine deaminase severe combined immune deficiency (ADA-SCID). The paper follows on a previous report in Science, 2002, and almost certainly counts as gene transfer's greatest clinical accomplishment to date.

I have previously argued in Lancet and Developing World Bioethics, as well as in my forthcoming book, that this study raised important justice concerns because it recruited volunteers from economically disadvantaged settings without clearly fulfilling the requirement, articulated in the Declaration of Helinki, of responsiveness. The NEJM article does not say where subsequent volunteers were recruited, though the fact that all but one new volunteer received PEG-ADA (a very expensive standard of care available only in high-income countries) suggests that later patients were not economically disadvantaged.

Rather than dwell on justice, I'd like to focus on the significance of this study. As indicated, eight of ten children with a life threatening immune disorder had their immune systems reconstituted. Five of these children had T-cell counts that were "above the lower limits of normal." These children were able to enjoy normal social relations parents and other children.

There do not appear to have been any adverse events relating to the gene transfer vector. A major concern was the possibility that gene transfer might trigger a leukemia-like syndrome observed in two X-SCID studies. Blood tests of children in this ADA-SCID study, however, do not evidence of either the leukemia syndrome or its precursors– at least within the time frame of the study (median follow-up of 4 years; range: 1.8-8 years).

So is ADA-SCID gene transfer ready to leave Milan and conquer ADA-SCID?  For children lacking haplo-identical bone marrow donors, maybe so given the morbidity associated with marrow  transplantation. Still, there are lingering concerns. First, though these results are encouraging, risks of malignancy remain unquantified. Second, this gene transfer regime requires several ancillary treatments- like bone marrow conditioning- that expose patients to risk of infection until the gene transfer intervention kicks in. Several volunteers in this study developed infections and neutropenia, for example. In an accompanying editorial in NEJM, Donald Kohn and Fabio Candotti describe several ways that retroviral gene transfer to blood stem cells might be made safer. Last, it is important to remember that ADA-SCID is a multi-system disorder, with neurological, skeletal, and other effects. Though this approach seems to address what is by far the largest cause of morbidity and mortality in children with ADA-SCID, it does eradicate their condition.

The results of Aiuti et al have been widely celebrated in the gene transfer community.  Kohn and Candotti's editorial, for example, is titled "Gene Therapy Fulfilling its Promise."  More than any single gene transfer study I can think of, this one seems to have earned the vindicating headlines. (photo credit: Paolo Margari, Milano Sazione Centrale Ferrovi, 2008)

GenetEx Cathedra

On December 12, the Catholic Church issued what the New York Times called "the most sweeping document on bioethical issues," its Dignitas Personae.  The document– the summary of which is available on the web– is dominated by discussion of in vitro fertilization, embyro research, and stem cells. But there is a section on gene transfer– and following on my previous post, the degree to which gene transfer has receded from the public discussion is striking (for example, gene transfer gets nary a mention in the New York Times coverage on Friday).

Here is what the document has to say about gene transfer.  It defines "gene therapy" in a rather un-(small-'c')atholic way, as "techniques of genetic engineering applied to human beings for therapeutic purpses, that is to say, with the aim of curing gentically based diseases."  This excludes lots of what goes on in gene transfer, like cancer and cardiovascular disease gene transfer and gene marking.  It also excludes much of what is morally contested about gene transfer– namely, enhancement applications.  About "somatic gene therapy," the statement says that "in order to proceed to a therapeutic intervention, it is necessary to establish beforehand that the person being treated will not be exposed to risks to his health or physical integrity which are excessive or disproportionate to the gravity of the pathology for which a cure is sought. The informed consent of the patient or his legitimate representative is also required." Nothing startling about this statement. But a careful reading raises interesting questions. What, for example, is meant by "establish beforehand?" What type and degree of evidence is required? Are gene transfer applications not aimed at "therapeutic intervention," like gene marking or vaccines, exempt? Another question: why the word "cure" given that few if any gene transfer strategies actually cure. Why not the more inclusive "treat?"

The statement on germ line cell therapy is somewhat intriguing. The document stops far short of categorically condemning such practices, and instead advises against them given that "the risks... are considerable and as yet not fully controllable." In principle, then, the Catholic Church does not oppose germline gene transfer applied surgically to adults, fetuses, gametes, and embryos provided risks are manageable. But it is hard to imagine how these risks could be reduced for embryos without research that destroys embryos. It is also hard to imagine how the safety of gamete gene transfer could be established without the creation of "injured" embryos. If my analysis is correct, embryonic and gamete germline gene transfer are obliquely banned, leaving permissible application of germline gene transfer to fetuses with genetic illness provided benefits outweigh risks.

The document goes on to warn against "genetic engineering... with the presumed aim of improving and strengthening the gene pool." Such techniques "promote a 'eugenic mentality';" many disabilities activists (and medicalsocial constructivists) will be heartened by the admonition that these techniques "introduce an 'indirect social stigma with regard to people who lack certain qualities, while privileging qualities that happen to be appreciated by a certain culture or society...." Still, one wonders what, exactly, this condemns other than heavy handed state, or large collective efforts, to improve the gene pool (that is, genetic engineering with the aim of creating individuals who can fly, see in the dark, or think more clearly is not explicitly banned).

Somewhat surprisingly, the document contains no language on somatic gene transfer applied towards the ends of enhancement, though the spirit of the prohibition on cosmetic germline alteration would seem to rule out the use of such techniques. (photo credit: Vatican stairs, tintalle* 2007)