Tolerability, Safety, and Activity of SRX246 in Irritable Subjects With Huntington's Disease

SRX246 is a first-in-class vasopressin 1a (V1a) receptor antagonist that crosses the blood-brain barrier following oral administration. The molecule exhibits high affinity and high selectivity for its target receptor. Preclinical pharmacology studies have demonstrated significant CNS effects in models of irritability, including impulsive aggression, depression, and anxiety. In an experimental medicine fMRI study in healthy volunteers, SRX246 treatment significantly attenuated the effect of intranasal AVP in brain circuits known to modulate emotional responses to stimuli that elicit aggression/fear. Together, these findings suggest that SRX246 has potential as a novel therapeutic agent for major neuropsychiatric symptoms seen in HD patients. This is a 3-arm, multicenter, randomized, placebo-controlled, double-blind, 12 week, dose escalation study of SRX246 in irritable Subjects with early symptomatic HD. Following an initial screening visit, Subjects fulfilling the study inclusion and exclusion criteria will enter a pre-treatment screening phase to permit evaluations to confirm eligibility for inclusion into the study. This screening phase will be no longer than 30 days. At the completion of the screening period, eligible Subjects will be randomized at baseline visit to receive either placebo or final doses of SRX246 of 120 mg twice daily or 160 mg twice daily during the double-blind treatment phase. At baseline, Subjects in the active groups will receive 80 mg twice daily for 2 weeks, then escalate to 120 mg twice daily for 4 weeks. Then one group of Subjects will continue to take 120 mg of SRX246 twice daily for an additional 6 weeks, and the second group of Subjects will increase their dose to 160 mg of SRX246 twice daily for 6 weeks. Total dosing duration is 12 weeks. Subjects in the placebo group will receive a similar number of capsules that are identical in appearance to the capsules that contain SRX246 during the trial, in order to preserve the blind. In all groups, dose escalation will occur (stepwise) if patients have not experienced dose-limiting adverse effects. Patients who cannot tolerate their final dose of drug (or placebo) can have this dose reduced without compromising the blinding. Subjects will have periodic visits either "in-person" or by "telephone", to assess tolerability, safety, and several measures of irritability and other problem behaviors, and clinical assessments for activity signals.