The depression treatment that Targacept (NASDAQ:TRGT) has identified as its lead drug candidate has failed in a phase 3 clinical trial, the second failure in less than two months for the compound.
Put simply, the drug candidate TC-5214 was no better than a placebo in the late-stage trial. If Targacept is to see success for the compound, being developed with drug partner AstraZeneca (NYSE:AZN), the Winston-Salem, North Carolina company will need better results from a different type of dosing for the drug candidate. The phase 3 failure of TC-5214 in November and the most recent clinical trial failure were both flexible dose studies. The next two clinical trials are administering the drug on a fixed-dosing schedule.
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There’s a reason that Targacept is conducting four phase 3 clinical trials on a single antidepression compound. The psychiatric community remains undecided whether flexible or fixed dosing is better to show statistical significance compared with a placebo. So, in designing the clinical trials, Targacept planned to do two of each. Like the first flexible dosing phase 3 trial, the second showed that TC-5214 did not outperform a placebo. Now TC-5214’s future rests entirely on results from the two fixed-dosing trials.
Targacept is a spinout from tobacco giant R.J. Reynolds. The compounds in Targacept’s drug pipeline all affect nicotinic receptors in the nervous system. The company is counting on this novel mechanism to become a medical breakthrough in antidepression drugs, which comprise an estimated $20 billion global market. TC-5214 is hoped to be an alternative to treatment for those patients who don’t respond to commonly prescribed serotonin reuptake inhibitors, SSRIs, or serotonin/norepinephrine reuptake inhibitors, SNRIs.
AstraZeneca recognized the opportunity and the potential of Targacept’s nicotine research. The companies entered into a collaboration and license agreement in 2009 that paid Targacept $200 million up front with the potential of an additional $540 million in milestones.
From the TC-5214 trial results, it now looks like flexible dosing of antidepressants isn’t superior to fixed dosing in a clinical trial. Or the compound may not be effective at all. Targacept expects results from the two fixed-dose trials, as well as a long-term safety study, in the first half of 2012. The results won’t end the debate over flexible versus fixed dosing. But it’s now clearer which side of the debate Targacept is pulling for.
