Jenrin Discovery is a privately-held pharmaceutical company developing a pipeline of proprietary ‘first-in-class’ small molecule drugs designed to selectively target peripheral tissues. Many marketed drugs, with efficacy not dependent on brain penetration are plagued by a sub-optimal safety profile, due to accompanying psychiatric and neurologic side effects. Jenrin has applied its medicinal chemistry expertise to structurally modify such agents so as to prevent penetration across the blood-brain barrier, resulting in negligible or no brain levels of compound. The new peripherally restrictive (PR) chemical entities retain the pharmacological activity and many of the drug properties of the parent therapeutic with little or no risk of the neuropsychiatric liabilities that accompanied the original agents. The Jenrin strategy of ‘rational drug re-design’ capitalizes on the years of medicinal chemistry that optimized the pharmacodynamic and PK properties of the original drug, significantly shortening discovery timelines and lowering development risk of the new proprietary agents.