Merck is abandoning its efforts to develop the substance P antagonist aprepitant (MK-0869) for treatment of depression.

"The Phase III clinical program was halted because the compound failed to demonstrate efficacy for the treatment of depression," Merck said Nov. 12.

The announcement marks the end of a high-profile R&D project at Merck. The company unveiled the substance P research program during its annual analysts meeting in 1997, calling the agent a "totally novel breakthrough in the field of mental health" (¹ Also see "MERCK WANTS PIECE OF ANTIDEPRESSANT BOOM: UNVEILS SUBSTANCE P ANTAGONIST "MEDICAL BREAKTHROUGH" TO ANALYSTS; VIOXX COX-2 INHIBITOR NDA SLATED FOR '98" - Pink Sheet, 8 December, 1997., p. 10).

The depression program, then entering Phase IIb, was intended to be the next blockbuster market for Merck to follow the COX-2 inhibitor Vioxx , then approaching the NDA filing stage.

However, in 1999, Merck was forced to change direction with the product when it failed to show significant improvement compared to a "high placebo response rate." The company moved into Phase III with MK-0869 as an anti-emetic (² Also see "Merck MK-869" - Pink Sheet, 25 January, 1999., In Brief).

The drug was approved under the trade name Emend in March as add-on therapy for prevention of emesis (³ Also see "Emend Risk Program To Ensure Prescribers Understand Approved Indication" - Pink Sheet, 31 March, 2003., p. 3). Emend has posted $19 mil. in sales so far this year.

Merck said it remains committed to neuroscience research, including depression. The company is not disclosing whether it intends any further research on substance P in depression.

Several other companies have Phase II programs for substance P (neurokinin 1) antagonists in depression, according to F-D-C Reports' ⁴ NDA Pipeline.

Two companies, Novartis and TAP, terminated development of compounds after Phase II.

Roche is currently in Phase II trials for depression and anxiety; the company has projected a 2006 NDA filing. GSK is also in Phase II trials for depression and anxiety. Pfizer and Sanofi-Synthelabo have also conducted clinical trials in the category.

Merck Discontinues Substance P Depression Compound After Failed Trial

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