Found Figures: Picking up the Pieces after an HIV Vaccine Trial Fails

In the November 29, 2008 issue of Lancet, two reports (plus a commentary) report the famously disappointing outcome of a recent placebo-controlled study testing adenoviral vector-based vaccines against HIV. News reports over a year ago reported that the study was halted after an interim analysis failed to show any prospect of proving effective. More troubling, subgroup analysis suggested that vaccine recipients who had high pre-existing immunity to the adenoviral vectors showed higher rates of sero-conversion compared with placebo. As this vaccine was among the most promising and advanced in terms of development, these results were seen as a major setback.

The recent Lancet reports paint a complicated picture: if I read them correctly, the inference that vector might enhance sero-conversion is muddied by the finding that circumcision status might also have played a role in sero-conversion (men with higher rates of adenoviral immunity were also, coincidentally, less likely to be circumcised).

What is clear, from what I gather, is that this is a good example where rigorous preclinical testing, coupled with rigorous trial design, permits meaningful interpretation of (unfortunately) negative human trial results. As Merlin Robb notes in a commentary accompanying the Lancet reports "the predictive value of the non-human SHIV-challenge model is not supported by this experience. The benchmarks for advancing candidate vaccines to efficacy testing and the priorities for vaccine research have been re-examined."

Well-designed studies, supported by rigorous preclinical testing, should always produce valuable, findings– like the unexpected "found figures" in the bark of a tree  (photo credit: Readwalker, Found figures, 2006)

Prime Time for Embryonic Stem Cells?

According to a recent report in the Washington Post, researchers at Geron have received approval from FDA to initiate the first ever human trial involving stem cells derived from human embryos.  A story in the most recent issue of Nature provides more background.

Briefly, the study will involve transplanting tissues derived from human embryonic stem cells into patients who have recently suffered severe spinal cord injury. The principle behind the study is that the embryo-derived oligodendrocytes might repair myelin and restore the ability for nerves to transmit impulses.  According to the Nature report, Geron, submitted 22,000 pages of material to FDA, including data from 24 studies involving over 2000 animals.

So is the decision to initiate studies at this juncture prudent?  That's impossible to know without seeing the supporting data. What I can comment on, however, is the recurrence of a rhetoric that glosses trial initiation– rather than trial outcome– as a medical achievement in itself.  Whereas the former is a regulatory event, the latter is a clinical event. In my book about gene transfer, I argue that this sets up a cycle of expectation that is difficult to sustain given the scientific and clinical uncertainties. We saw this in the early days of gene transfer. Some examples of this "trial initiation"="medical achievement":

• "This... marks the dawn of a new era in medical therapeutics. This approach is one that reaches beyond pills and scalpels to achieve a new level of healing." (Thomas Okarma, Geron chief executive)

• "Today's news... is a milestone in the new era of hope..." (Amy Comstock Rick, Coalition for the Advancement of Medical Research)

• "This is what we've all been waiting for" (Robert Lanza, Advanced Cell Technology)

• "The announcement boosted the price of shares in [Geron]... up 56% from the day before the announcement" (Meridith Wadman, Nature, Jan 27, 2009)

I wish Geron, and the patients enrolled in this study, all the best.  But if embryonic stem cell work is anything like practically every other major medical advancement, be prepared for a very long, tough slog with lots of setbacks.  In one of the stories, Sean Tipton from the Coalition for the Advancement of Medical Research, commented  "This is a trial of one particular application, not a trial of all embryonic stem cells." That sounds just about right. (photo credit: no typographic man, UlamSpiral (negative), 2006)

Age of Risk: Biologicals

Approving new drugs is a risky business. Despite best efforts (and frankly, some less than best efforts), newly approved drugs frequently turn out to have unexpected toxicities. One example is unexpected heart toxicity associated with the use of the common pain-killers like rofecoxib (i.e. Vioxx).  Another is the surprising heart toxicity associated with the wonder drug for AML (a type of leukemia), imatinib mesylate (i.e. Gleevec).

According to a  2002 paper in JAMA, 8% of new drugs approved by FDA receive "black box" labels warning of toxicities that were not originally detected in drug trials. Another 3% are withdrawn from the market because of safety concerns. 

But what about biologics- vaccines, monoclonal antibodies, recombinant protein products, cell derived agents, etc.? There are a number of reasons why one might anticipate even higher rates of "unexpected" toxicities with this class of therapeutics. For one, they frequently cause immune reactions that are exceedingly difficult to anticipate in animal studies. For another, small alterations in production can dramatically change the composition and properties of a biologic product. For still another, biologics often have a very high degree of species specificity, limiting the predictive value of animal studies.

According to a recent report in JAMA led by Thijs Giezen (October 22/29, 2008), 24% of biologics approved for marketing in Europe received "black box" warnings.  For first-in-class agents, five of eight compounds were subject to regulatory action following approval.  A story in the January 2009 issue of Nature Biotechnology (Jim Kling) provides some perspective on these findings: most biologics are used to treat life threatening illnesses, which may make people more susceptible to toxic reactions (on the other hand, toxicity might be difficult to detect amidst the noise of disease course).

Bottom line: as translational researchers pursue biologics, uncertainty will continue to present a major challenges, necessitating new approaches to pharmacovigilence and trial design. (photo credit: teotwawki 2005)

What Will the New Year Bring?

My hope is that, with a new Presidential administration, certain research and ethics policies of the U.S. government might be revisited. One such policy is the FDA's replacement of the Declaration of Helsinki with the International Conference on Harmonization's Guideline for Good Clinical Practice (GCP) for foreign studies.  Recall that, in May, I lamented what at that time was a proposed policy change (it was finalized on October 27, 2008).

In the January 3 issue of Lancet, Charles Weijer, Eric Meslin, and I briefly lay out reasons why FDA's action is regrettable, and how GCP and Helsinki differ.  We urge the incoming administration to review this policy, and for medical societies to take action now and endorse Helsinki.  Our comment is featured, and is thus accessible for free at Lancet. (photo credit: Vilhelm Sjostrom, "Happy New Year 2009 from Helsinki, Finland," last seconds of 2008)

Stems and Blossoms (part 2): Really Informed Consent

There is a strain within the clinical and bioethics community that takes a minimal view of informed consent: investigators are supposed to provide requisite information to volunteers; if research subjects fail to comprehend this information, pity for them. This view brings to mind a memorable exchange between Inspector Clouseau and a hotel clerk (Clouseau: "does your dog bite?" Clerk: "No."  Clouseau then extends a hand; the dog lunges at him.  "I thought you said your dog doesn't bite." Clerk: "Zat is not my dog.")

The ISSCR guidelines take a bold stand on informed consent. "Investigators involved in clinical research must carefully assess whether participants understand the essential aspects of the study."  The guidelines go on to state "ideally, the subject's comprehension of information should be assessed through a written test or an oral quiz during the time of obtaining consent." Once again, ISSCR shows vision here in going well beyond the legalistic conception of informed consent described above.

The ISSCR guidelines also urge researchers to:

• explain possible irreversibility of some toxicities

• describe the sources of stem cells

• inform patients that researchers "do not know whether they will work as hoped"

These laudable recommendations aside, I might have hoped for more guarded language about the therapeutic value of early phase studies. For one, the guidelines use mostly "therapeutic" language, for example, using the aspirational term "cell therapy" instead of the neutral term "cell transfer." Second, the third item above logically means that the probability of benefit is less than 100%; experience tells us, however, that when interventions are highly novel, major therapeutic benefits for early phase trials are very improbable. (photo credit: Helen K, Stems, 2008)

Stems and Blossoms (part 1): Justice

Shortly before I left for holiday, the International Society for Stem Cell Research (ISSCR) issued a policy paper, "Guidelines for the Clinical Translation of Stem Cells," outlining ethical and scientific considerations for researchers designing translational trials involving stem cells (whether stem cell derived, adult, or embryonic).

In my opinion, the document wins the award for most forward thinking and comprehensive statement on the ethics of a translational enterprise. It shows that the stem cell research leadership has closely studied mistakes made by translational researchers in other highly innovative fields.  But the guidelines do more than look backwards; they proactively contemplate fairness and justice considerations as well.  Here are a few justice-related excerpts:

On responsiveness: "The ISSCR strongly discourages conduct of trials in a foreign country solely to benefit patients in the home country of the sponsoring agency. The test therapy, if approved, should realistically be expected to become available to the population participating in the clinical trial through existing health systems or those developed on a permanent basis in connection with the trial."

On reasonable availability: "As far as possible, groups or individuals who participate in clinical stem cell research should be in a position to benefit from the results of this research."

On diversity: "Stem cell collections with genetically diverse sources of cell lines should be established"

On access and licensing: "Commercial companies, subject to their financial capability, should offer affordable therapeutic interventions to persons living in resource-poor countries who would otherwise be wholly excluded from benefiting from that stem cell-based therapy. Academic and other institutions that are licensing stem cell therapeutics and diagnostic inventions should incorporate this requirement in their intellectual property license"

On review: "Regulatory and oversight agencies (local, national, and international) must explicitly include the consideration of social justice principles into their evaluations."

On trial participation: "... the sponsor and principal investigator have an ethical responsibility to make good faith, reasonable efforts whenever possible to secure sufficient funding so that no person who meets eligibility criteria is prevented from being considered for enrollment because of his or her inability to cover the costs of the experimental treatment."

In upcoming posts, I will comment on other aspects of the ISSCR guidelines. (photo credit: Helen K, Stems, 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)