Arbaclofen: Phase II data

In the per protocol (PP) population (n=25) of an open-label, U.S. Phase II trial, STX209 met the primary endpoint of significantly improving irritability subscale scores on the ABC-I from baseline to week 8 (p<0.001). STX209 also significantly improved global and specific neurobehavioral outcomes from baseline, including the Social Withdrawal subscale of the ABC (ABC-SW) (p<0.001) and the ABC-Total scale (p<0.001). Additionally, STX209 significantly improved investigators' assessments of Clinical Global Impressions of Improvement (CGI-I) (p=0.001) and Severity (CGI-S) (p=0.002) from baseline to week 8. Seaside said a broad range of behavioral and cognitive endpoints were included in the study to add to the company's knowledge of potential efficacy measures in patients with ASD.

STX209 was well tolerated with no metabolic side effects observed. There was 1 serious adverse event of worsening of aggression during taper of the compound. Patients received a 1 mg twice daily starting dose of STX209 that was gradually increased up to 10 mg thrice daily for subjects >11 years old as a flexible titration over 2 weeks until the optimal titrated dose was reached. The optimal titrated dose was continued for the remainder of the 8-week treatment period. An open-label extension study is ongoing. Seaside said it plans to start "late-stage" clinical trials of STX209 in both fragile X syndrome and autism later this year after meeting with FDA. ...