The outcomes of clinical trials for drugs to treat depression (Blier, 2008; Kirsch, 2009; Kramer, 2005; Leventhal & Martell, 2005) have been a controversial topic with considerable focus on placebo responses. A meta-analysis (Kirsch, Moore, Scoboria, & Nicholls, 2002) of the efficacy data from 47 clinical trials covering the six most widely prescribed antidepressants approved between 1987 and 1999 - fluoxetine, paroxe-tine, sertraline, venlafaxine, nefazodone, and citalopram - determined that approximately 80% of the effect ascribed to drug was also seen in the placebo controls. This led to the oft-repeated claim that four out of six clinical trials for approved antidepressants routinely fail. In a follow-up analysis focusing on fluoxetine, paroxetine, venlafaxine, and nefazodone (Kirsch et al., 2008), it was further established that baseline severity was a critical component for drug-related responses, and that a decreased response to placebo rather than an increased drug response was frequently responsible for positive clinical results in this area. It was additionally determined that patients recruited into clinical trials were not representative of the average individual treated in practice (Wisniewski et al., 2009). The issue of antidepressant efficacy has been further clouded by the selective reporting of data in published findings (Turner & Rosenthal, 2008; Turner et al., 2008). Thus, publications covering 37 out of 74 FDA-registered trials indicated that 94% of these yielded positive results. However, an FDA analysis of the full cohort of 74 trials revealed that only 51% of the trials were positive, suggesting that antidepressants were less effective than the published data indicated. The issue of the placebo effect in clinical trials for psychiatric medications remains a highly controversial topic (Silberman, 2009).
Thus while considerable evidence exists as to why the translation of NCEs to the clinic based on non-clinical efficacy and safety data to the clinic may be flawed, it is equally possible that the actual data from clinical trials may also be flawed, reinforcing - to a major degree - the need for a bidirectional flow of information (Sung et al., 2003) on NCE efficacy as a planned part of the translational process through Phase IIa rather than a typical binary fault finding exercise across the translational divide.
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