An Exploratory Evaluation of the Safety and Efficacy of Vorinostat in Pitt Hopkins Syndrome

The study is an exploratory evaluation of the safety and efficacy of vorinostat in Pitt Hopkins syndrome. Each patient will be self-controlled in an adapted N-of-1 study design methodology with three treatment arms, including a 4-week placebo phase and two vorinostat dose arms, including every 8 weeks of daily dosing at a low dose of 80mg/m2/day and 8 weeks of a higher dose at 160mg/m2/day. Key objectives of the study include: * To confirm the safety and tolerability of oral vorinostat 80mg/m2/day and 160mg/ m2/day dose levels when administered to PTHS patients * To identify the nature and magnitude of treatment response to vorinostat, as measured by changes in clinical and laboratory parameters indicative of trend towards benefit, as well as changes in mRNA expression (transcriptome response) * Provide a data-driven justification for future study design and statistical analysis plan for subsequent clinical studies assessing safety and efficacy of vorinostat in PTHS