Tuesday, December 29, 2009

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)

Friday, December 4, 2009

Finding Skew: Informed Consent and Bias in Clinical Trials

Clinical researchers have long claimed that patients who enter clinical trials are better off medically than those who don't. I'm open to the notion that patients might derive personal meaning from trial participation, but I've always been dubious of the suggestion that trial participation in itself is therapeutically beneficial–above and beyond drugs received– in part because this has never been demonstrated in a convincing way. I've also worried about the way the "trial effect" has been occasionally mobilized to recruit patients, or to apologize for studies of dubious design. Last, I've worried about the ethical implications of the prospect that, in order to receive top quality care, patients should be enrolling in (or have access to) clinical trials.

One reason I have been skeptical of the "trial effect" is that trials do not enroll a random sample of patients. Ethical research requires informed consent, and if patients who consent to trials have different characteristics than those who decline, it seems plausible that they will have different medical courses. UK researchers led by Andrew Clark recently put this thesis to the test (Eur J Heart Failure; also reported in the December issue of Nature Medicine). In their study, they asked a large sample of patients whether they were willing to enter a clinical trial. They then followed the clinical course of patients who declined, and compared them with patients who consented to participation but were never enrolled in a clinical trial. They found that patients who accepted enrollment had better clinical outcomes- even when factors like age, other sicknesses, or drug use.

The finding raises a number of interesting questions about tensions between study validity and informed consent. It does not suggest that we should relax consent standards to reduce bias- though some may be tempted to view the study in this way. It does, however, raise questions about how findings in clinical trials should be interpreted when applying them in real clinical settings. And it provides another problem for those who are attached to the position that trial participation is, in itself, therapeutic. (photo credit: funkandjazz, Skew, 2007)