Neurogen, Branford, Conn, has suspended dosing in the trial of its insomnia drug, adipiplon. The company has stated that the bilayer form of the tablet may not be performing as expected.

The company commenced a phase 2/3 clinical trial in chronic insomnia patients with the company’s insomnia agent, adipiplon, but based on reports from initial dosing of a higher than anticipated rate of unwanted next day effects, Neurogen suspended dosing in the study.

“We do not yet know whether there is a path forward with lower doses of the existing formulation or whether further formulation development would be required. Until we further assess the situation and determine whether there is a path forward we can and should take, we will carefully limit our resource commitments to this program,” says Stephen R. Davis, president and CEO of Neurogen.

Adipiplon comes in two forms: one controlled release form and one immediate release form. Previous studies by the company have administered various doses of both forms simultaneously; however, this study is the first to use the two forms laminated together into one bilayer tablet.

The company plans additional investigation of the bilayer tablet before proceeding further.