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)

California Dreamin: CIRM Announces New Stem Cell Awards

California's Institute for Regenerative Medicine just announced a series of large funding awards to fund translational research initiatives involving (mostly) stem cells. The projects funded are telling with respect to what was funded, and what they will attempt to achieve.

First, notwithstanding a press release containing the words "bringing stem cell therapies to the clinic," several projects are really dressed up gene transfer studies. Thus, one team will use gene transfer in hematopoietic stem cells for sickle cell anemia; another two will use gene transfer to stem cells for treating brain malignancies; another RNAi for HIV. All this is only further evidence that the field of stem cells is devouring gene transfer. Other projects are aimed more at getting "stem cells out of the clinic" by using small molecules or monoclonal antibodies to destroy stem cells causing malignancies.

Second is the sweeping ambition. As it stands today, only one clinical trial involving embryonic stem cell-derived tissues has been initiated. The projects funded under these awards are "explicitly expected to result in a filing with the FDA to begin a clinical trial." Given that these projects are funded for four years, CIRM seems to be banking on the prospect of at least a few of these initiating phase 1 trials within five years. Four of these proposals involve goals of implanting embryo-derived tissues, and two of these involve non-lethal conditions–macular degeneration and type I diabetes (technically, other awarded projects involve nonlethal, though extremely morbid conditions). Another involves implantation of embryo-derived tissues for Amyotrophic Lateral Sclerosis. It will be interesting to see how many of these meet their translational objectives, and how investigators will navigate the ethical, regulatory, and social complexity of initiating clinical testing. (photo credit: Michael Ransburg, 2008)

The Need for Speed: GAO Reports on Accelerated Approval

Several blog posts ago, I wrote about the policy of accelerated approval (briefly, a mechanism whereby new drugs can be approved for sale by the FDA before definitive evidence of efficacy and safety are available). In that post, I reported on a recent paper where the authors claimed that, all things considered, accelerated approval enabled patients to get quicker access to life saving drugs without major adverse impacts on patient safety.

Last week, the Government Accounting Office issued a report on the subject that took a less favorable view of the program. Rules require that companies receiving accelerated approval for new drugs complete post-marketing studies confirming their efficacy. The GAO investigated the frequency with which companies fail to submit post-marketing trial data. They found that over a third of FDA-required post-marketing studies aimed at confirming efficacy had not yet been completed. Many of these studies might be incomplete because accelerated approval was only recently granted, and it can take as long as five years to complete requested studies. Disturbingly, however, the report found that a quarter of these studies had been incomplete for over five years; other studies have been completed but not yet reviewed by the agency. The figures are worse for other types of post-marketing studies requested by the agency.

The "poster boy" drug singled out in the GAO report is the hypertension drug Proamatine, which earned Shire Pharmaceuticals $257M since it was approved under accelerated approval 13 years ago. Apparently, the drug has not been subject to adequate confirmatory testing in all this time, though FDA has issued warning letters to the company over its promotion practices.

The report saves its criticism for the FDA, which it says has not reviewed sponsors' submissions in a timely manner, does not adequately monitor progress of post-marketing studies, and has neither specified conditions under which it would exercise its authority to withdraw drugs from market, nor has it ever exercised its authority to do so. But isn't some criticism also warranted for companies exploiting FDA's deficiencies? (photo credit: lindsay kay photography 2009)

Remembrance of Things Past: Fetal Tissue Transplantation and Parkinson's Disease

In a recent article in Science magazine, Constance Holden reports that European researchers are contemplating a revival of fetal tissue transplantation for the treatment of Parkinson’s disease. As the article recounts, fetal transplants were subjected to sham controlled studies in the late 1990s; none performed better than sham, and several caused disabling dyskinesias. So should fetal tissue transplantation be revived, and if so, how?

The challenges seem all the more formidable today. We now understand that Parkinson’s disease is not restricted to the dopaminergic neurons in the basal ganglia, but instead involves diffuse pathology. And yet, studies will not involve implantation of tissues throughout the brain. As Holden’s article points out, previous fetal transplant studies revealed that brain pathology spreads to implanted tissues, suggesting that permanent responses may be difficult to achieve.

The ethical issues seem just as daunting. Deep brain stimulation has greatly improved the management of Parkinson’s for patients who are no longer responding to dopamine replacement. And yet, those pursuing fetal tissue transplantation will likely advocate pursuing trials in younger patients with less advanced disease. As pointed out by a European team of researchers, "A significant effort of bioethical research and conceptual clarification is required in anticipation of the first protocols involving human subjects." And in a recently published article in Movement Disorders, several coauthors and I outline various ethical challenges presented by such studies. These include a high degree of uncertainty about the safety of interventions, and a baseline risk associated with delivery that approaches levels of risk encountered in phase 1 cancer trials (for studies that involve eight inoculations to the brain, risk of intracerebral brain hemorrhage leading to permanent neurological deficits is on the order of 2%).

Advocates of the new wave of studies insist we know much more about the properties of fetal tissues than we did in the 1990s; they further note that such studies will provide a basis for later studies involving induced pluripotent stem cells and other tissues. Perhaps, but given the remaining uncertainties and promise of DBS, it’s hard to imagine how fetal graft experiments could credibly establish a claim of clinical equipoise with deep brain stimulation. For these reasons, a more prudent ethical course—if fetal transplant studies for Parkinson's are to be done at all—would be to pursue safety and feasibility studies in patients who are no longer responsive to standard care. Only once parameters are optimized and mechanisms well understood should clinicians consider studies in patients who are earlier in the disease process. (photo credit: Ethan Hein 2008)

Disclosure in Phase 1 Cancer Trials

Followers of this blog may recall my continuing concern with the way informed consent is obtained in phase 1 trials involving patient-volunteers (typically, these patients have exhausted standard care options and enter phase 1 trials as a final shot at managing their disease). Language used by investigators in these studies is often suggestive of therapeutic benefit, even though meta-analyses of phase 1 studies show that chances of major clinical benefit in phase 1 studies are exceedingly low. In previous posts, I described my own experience with an ethics review committee that actually defended giving patients vague and almost meaningless information about the therapeutic benefits of phase 1 trial participation. Meantime, evidence from surveys indicate that phase 1 cancer patient-volunteers tend to overestimate the probability of therapeutic benefit.

In the July-August 2009 edition of the ethics journal IRB, Shlomo Koyfman and co-authors at NIH offer up a "Consent Form Template for Phase I Oncology Trials." Their recommendations are comprehensive and excellent. Among the items they recommend are:

• use of more therapeutically neutral language, like "research agent" instead of "therapy"

• disclosure of dose escalation design; in particular, the authors recommend that patients be informed about risks and benefits relative to the cohort they are entering.

• a statement (where appropriate) that patient-volunteers will not have the option of adjusting their dose assignment in the study

• a statement that "the chances that this agent will... allow you to live longer [is] very low."

One can quibble with various particulars (I think, for example, discussion of subtherapeutic dosing should be more explicit). But on the whole, these recommendations provide an excellent standard– along with NIH Guidance on Informed Consent for Gene Transfer Research– against which typical phase 1 cancer study consent forms should be measured. (photo credit: banlon1964)

Quack You! Medical Tourism and Stem Cells

In the September 2009 issue of Nature Biotechnology, Jane Qiu reports on a thriving trade in nonvalidated stem cell interventions for incurable illnesses ("Trading on Hope"). The article provides numerous examples of overseas clinics that cater primarily to North American and European clientele in offering pricey, unproven stem cell transplants for incurable conditions like spinal cord injury, Parkinson's disease, and autism. Many of these clinics make extravagant claims in their promotion materials.

Encouragingly, policy makers are beginning to take notice. China, for example, has issued new regulations on clinical application of novel interventions; it requires licensing for clinics that provide unproven stem cells. India has issued guidelines on stem cell research and therapy. As noted previously in this blog, the scientific society ISSCR issued guidelines urging clinicians to offer nonvalidated stem cell interventions to patients only in the context of clinical trials designed to test safety and efficacy. Problem is (according to the article), guidelines are sporadically enforced, if that.

I think there is much more that governments and professional societies can and should do to stem this unethical conduct. Though most of these clinics are located outside of North American and Europe, some overseas clinics have reputable, North American / European scientists and clinicians on their advisory board or have partnerships with biotechnology companies that are based in North America / Europe. Examples include Stemedica (which includes several Stanford and UCSD faculty on its advisory board), and Theravitae (which has involved close collaboration with University of Pittsburgh clinicians), and Vescell (which includes Nobelist Aaron Ciechanover on its scientific advisory board). All of these companies offer stem cell interventions to large numbers of patients outside trials, and make claims that their interventions are effective when, in fact, they remain unproven.

1- Research ethics policies should condemn scientist-clinicians who travel or collaborate abroad in delivering nonvalidated, potentially risky interventions overseas outside the context of a clinical trial. Policies should state clearly the imperative of subjecting nonvalidated interventions to systematic study.

2- Institutions should not allow these clinics to trade on their reputations, and should sanction faculty members who are involved in such activities.

3- professional societies in medical fields (e.g. cardiology) and research areas (stem cells, gene transfer) should steward the standing and credibility of their research field by developing policies and standards that discourage inappropriate activities-- through social pressure-- by providing a benchmark against which the conduct of scientists and clinicians can be judged.

(photo credit: Insert Photographer Here, 2006)

Accelerated Approval: Safe at Any Speed?

Drug regulatory authorities like the FDA have a mandate to protect public health by requiring and evaluating evidence of safety and efficacy before licensing new drugs for commercial sale. But for decades now, patient advocates have argued that FDA bureaucracy kills by keeping promising drugs from the IV's of terminal patients. In response to these criticisms, FDA and others have created new pathways for drug approval whereby drugs can be partially approved for sale on the basis of smaller, Phase 2 trials using surrogate endpoints (tumor shrinkage) instead of survival– provided drug companies confirm efficacy in subsequent trials.

This pathway, called "accelerated approval," is controversial because it allows companies to sell drugs whose efficacy and safety is not yet well established. True- the companies are obliged to run confirmatory studies, but a) how will confirmatory trials enroll enough subjects if patients know they might be randomized to standard, ineffective drugs, and they can get the drug outside a clinical trial? b) drug companies will not have sufficient incentive to run confirmatory studies once their drug is provisionally approved. c) drug companies stand to make lots of money selling unproven drugs to desperate patients in search of a cure.

In the most recent issue of Journal of Clinical Oncology, Elizabeth Richey and coauthors put these concerns to the test in an analysis "Accelerated Approval of Cancer Drugs: Improved Access to Therapeutic Breakthroughs or Early Release of Unsafe and Ineffective Drugs." They find that:

• a very large percentage of new cancer drugs are initially approved under "accelerated approval." (37% approvals between 1995 and 2008)

• 63% of drugs receiving accelerated approval have their clinical benefit confirmed in subsequent studies

• drugs involving very rare cancers are often not subjected to confirmatory testing (42%); drugs for more common cancers are tested in confirmatory studies typically (71%-- though the percentage I calculated from their figures is actually higher- 86%)

• drugs receiving accelerated approval are twice as likely to receive black box warnings compared with drugs approved by the standard mechanism (21% vs. 10%)

• about half of non-orphan drugs approved under accelerated approval (47%) become first line treatment regimens in the National Comprehensive Cancer Network.

The authors see the glass half full on accelerated approval: to the title question of their article, the authors answer "Improved Access to Therapeutic Breakthroughs." (photo credit: Marxpix 2008)