The International Journal of Neuropsychopharmacology

Research Article

Lack of efficacy of L-759274, a novel neurokinin 1 (substance P) receptor antagonist, for the treatment of generalized anxiety disorder

David Michelsona1 c1, Richard Hargreavesa1, Robert Alexandera1, Paulette Ceesaya1, Jarmo Hietalaa2, Christopher Linesa1 and Scott Reinesa1

a1 Merck Sharp and Dohme Corp., Whitehouse Station, NJ, USA

a2 Department of Psychiatry and Turku PET Centre, University of Turku, Turku, Finland


Preclinical studies suggest that substance P acting at neurokinin 1 (NK1) receptors may be involved in stress responses and NK1 receptor antagonists show activity in tests of anxiety. These data raise the possibility that NK1 receptor antagonists could be potential anxiolytic treatments in humans. We evaluated this hypothesis clinically using the NK1 antagonist L-759274. This is a randomized, double-blind, placebo- and active-controlled, multicentre, proof-of-concept trial. Patients with generalized anxiety disorder were randomized 1:1:1 to 6 wk of treatment with 40 mg L-759274 (n = 73), 1–6 mg lorazepam (n = 69) or placebo (n = 71). Efficacy was assessed using the Hamilton Anxiety Scale (HAMA). A positron emission tomography (PET) study was also performed in 16 healthy subjects to determine the relationship between NK1 receptor occupancy and plasma levels of L-759274 to verify adequate target engagement by the doses tested during the clinical trial. No statistically significant difference in mean change from baseline HAMA score at 6 wk was seen for L-759274 vs. placebo [difference = 1.0 (95% confidence intervals (CI) −1.2 to 3.2), p = 0.359] whereas the lorazepam group did show a significant improvement vs. placebo (difference = −2.7, 95% CI −5.0 to −0.4, p = 0.020) and L-759274 (difference = 3.7, 95% CI 1.5–6.0, p = 0.001]. Results from the PET study indicated that the L-759274 dosing regimen used in the clinical trial likely provided high levels of NK1 receptor occupancy (>90%), supporting the view that it was an adequate proof-of-concept trial. The NK1 receptor antagonist L-759274 does not appear to be efficacious for the treatment of generalized anxiety disorder.

(Received July 28 2011)

(Reviewed November 07 2011)

(Revised December 02 2011)

(Accepted December 21 2011)

(Online publication March 21 2012)

Key words

  • Generalized anxiety disorder;
  • lorazepam;
  • neurokinin 1 receptors substance P;
  • randomized controlled trial


c1 Author for correspondence: Dr D. Michelson, Merck Sharp & Dohme Corp., 351 North Sumneytown Pike, North Wales, PA 19454, USA. Tel.: (001) 267 305 6222 Fax: (011) 267 305 6454 Email: