Genomics Used to Improve DEpression Decisions

Major depressive disorder (MDD) is a highly prevalent (Hasin et al., 2005) mental disorder and a leading source of disease burden worldwide (Lopez et al., 2006). Epidemiological studies estimate 12-month and lifetime prevalence for MDD in the United States to be 5.3% and 13.2%, respectively (reviewed in Blanco et al., 2010). MDD is expected to be the second greatest cause of disability by 2020 and has been shown to cause significant morbidity, affecting people's ability to work, function in relationships, and engage in social activities. Moreover, MDD increases the risk of suicidal ideation, attempted suicide, and death by completed suicide. Prospective longitudinal studies of patient samples show that MDD is a chronic illness, characterized by remitting and recurrent depressive episodes (Solomon et al., 1997; Mueller et al., 1999). A major depressive episode is characterized by a low mood or an inability to experience pleasure (anhedonia), or both, for more than 2 weeks, combined with several cognitive and vegetative symptoms and the occurrence of distress or impairment (reviewed in Rot et al., 2009). In the US, nearly 1 in 5 people will experience a major depressive episode at some point in their lives (reviewed in Rot et al., 2009). Drugs currently available to treat depression fall into the categories of those that have their main effect by increasing norepinephrine (NE) (the tricyclic or tetracyclic antidepressants \[TCAs\]), those that increase serotonin (5-HT) (the selective serotonin reuptake inhibitors \[SSRIs\]), and those that increase both NE and 5-HT (the monoamine oxidase inhibitors \[MAOIs\] and the serotonin and norepinephrine reuptake inhibitors \[SNRIs\]). While all antidepressants achieve similar levels of efficacy, treatment failures are relatively high ranging from 30 to 60% (Simpson and DePaulo). Additionally, many of these compounds are associated with significant adverse events (AEs). The GeneSight Psychotropic product is a pharmacogenomic decision support tool that helps clinicians to make informed, evidence-based decisions about proper drug selection, based on the testing for clinically important genetic variants in multiple pharmacokinetic and pharmacodynamic genes that affect a patient's ability to tolerate or respond to medications. The GeneSight Psychotropic product contains the most commonly prescribed antidepressant and antipsychotic medications, including a full representation of the SSRI and SNRI drug classes. Tricyclic antidepressants, an MAOI, and typical and atypical antipsychotics are also represented. The clinical utility of GeneSight Psychotropic has been evaluated in three previous prospective trials. Hall-Flavin et al reported the results of an open-label pilot study (n = 44) comparing GeneSight guided treatment to treatment as usual (TAU) without the benefit of pharmacogenomic testing (2012). The GeneSight guided arm demonstrated a 30.8% improvement in HAM-D17 score by the end of the 8 week treatment period, compared to an 18.2% improvement in the TAU arm (p = 0.04). Results of the larger (n = 165) open-label trial (Hall-Flavin, et al 2013) mirrored these findings, demonstrating a 46.9% improvement in HAMD17 score in the GeneSight arm, compared to a 29.9% improvement in the TAU arm (p \< 0.0001). The third trial used a randomized, double-blind trial design (n = 51). Due to the small sample size, the trial was underpowered to detect a significant difference in improvement between the two arms (TAU and GeneSight). However, effect sizes of improvement reflected those seen in previous trials. The GeneSight group experienced a 30.8% improvement in HAMD17, compared to 20.7% in TAU. Odds ratios for response were calculated, showing that GeneSight-guided subjects had a 2.14 times greater likelihood of response compared to TAU subjects, which was similar to the 4.67 (smaller trial) and 2.06 (larger trial) odds ratios calculated for the other two studies. Previous studies utilizing an open-label design have shown significant improvement in patient outcomes following use of the GeneSight test. However, although effect sizes were similar to those seen in the open-label studies, a small (n = 51) blinded, randomized controlled trial did not detect a statistically significant outcome. Therefore, the primary rationale for this trial is to replicate previous findings of improvement in clinical outcomes in subjects treated with the benefit of GeneSight testing utilizing a double-blind, randomized control trial (RCT) design. It is expected that results from this trial will be used to inform guidelines for the use of pharmacogenomic testing for the treatment of major depressive disorder. Results may also be shared with regulatory bodies in the United States and abroad.