As expected, AstraZeneca has discontinued further development of an antidepressant licensed from Targacept following more disappointing Phase III results.

The companies announced top-line results from the remaining Phase III studies investigating the drug, TC-5214, as an adjunct therapy to an antidepressant in patients with major depressive disorder (MDD) who did not respond adequately to initial treatment.

Two efficacy and tolerability trials, Renaissance 4 and 5, both efficacy and tolerability studies, did not meet the primary endpoint of topping placebo after eight weeks of adjunct treatment. In Renaissance 7, a one-year study, TC-5214 was overall well tolerated.

These results come on the back of disappointing data from the first two Phase III trials at the end of last year, which resulted in AstraZeneca taking a partial impairment charge of $96.5 million "based on the lower probability of success for the remaining TC-5214 studies". Given the latest failure, and "the totality of the results", the firms will not pursue a regulatory filing  and AstraZeneca will take an intangible asset impairment charge of $50 million.

The Anglo-Swedish drugmaker had had high hopes for the drug, a first-in-class nicotinic channel modulator and paid $200 million upfront in December 2009 for the rights.