Study to Assess the Safety and Efficacy of NRP104 in Adults With Attention-Deficit Hyperactivity Disorder (ADHD)

This study is a randomized, phase III, multi-center, placebo-controlled, parallel-group, forced dose titration in which adult subjects (18-55 years of age inclusive) with ADHD will be randomized to NRP104 (30, 50, or 70 mg) or placebo for four weeks of double-blind evaluation of safety and efficacy. The study will have three phases: (1) screening and washout; (2) baseline; and (3) 4-week double-blind evaluation of NRP104 and placebo. The double-blind period will include a forced dose titration phase followed by a fixed dose phase. Subjects will be required to visit the site up to 6 times over a 5-8 week period, or longer in cases requiring a 28-day wash out. Screening and Washout: Subjects will be screened to establish eligibility for study participation. The Screening Visit (Visit 1) may take place over multiple days if needed to accommodate the subject's schedule. Those subjects who meet eligibility requirements will undergo medication washout, if applicable. The length of the ADHD medication washout period will range from 7-28 days. Baseline: Following medication washout, subjects will return to the clinic for reassessment of eligibility criteria and establishment of baseline measures. The interval between the first day of the Screening Visit (informed consent date) and the Baseline Visit (Visit 2) must not exceed 35 days. Eligible subjects with a baseline ADHD-RS score greater than or equal to 28 (performed using adult DSM-IV prompts) will be randomized to treatment. Double-blind treatment: Eligible subjects will be randomly assigned (in a 2:2:2:1 ratio of each of the three active doses vs. placebo) to a daily morning dose of NRP104 or placebo for 4 weeks. All NRP104 groups will start at a dose of 30 mg/day. Subjects randomized to 70 mg will be titrated to that dose over a 2-week period; those randomized to 50 mg will be titrated to that dose over a 1-week period; and those randomized to 30 mg will begin dosing on 30 mg per day during week one and will remain on that dose throughout the study. Double-blind assessment of the safety and efficacy of NRP104 will proceed for 4 weeks with weekly clinic visits scheduled for evaluations and medication disbursement. Follow-up period: Subjects who have completed at least 2 weeks of double-blind participation, will have the option to continue participation in an open-label extension study (Protocol NRP104.304: one-year safety study). Subjects who are not eligible or who choose not to participate in the extension study will continue to be followed for thirty days following their last dose of study drug. A telephone contact (or contact in person) will be initiated by the research site to collect any new or ongoing SAEs and to follow-up on any unresolved or related AEs from the Final Study Visit or Early Termination (ET) Visit (Visit 6). If the Principal Investigator determines AEs are not acceptably resolved, appropriate follow-up should continue until all safety concerns, in the opinion of the Investigator, are resolved.