VIP

Vasoactive intestinal peptide (VIP) is a 28-amino-acid neuropeptide belonging to the secretin/glucagon superfamily. It was isolated and identified by Sami Said and Victor Mutt in 1970 and is widely expressed throughout the central and peripheral nervous systems, gastrointestinal tract, lungs, cardiovascular system, and immune tissues. It functions simultaneously as a neurotransmitter, vasodilator, bronchodilator, exocrine secretagogue, and immunomodulator. Synthetic human VIP, known commercially as aviptadil, has been investigated in clinical trials across several indications. Its most established approved use is a niche intracavernosal injection for erectile dysfunction (Invicorp, approved in the UK and EU since 2000), in combination with phentolamine. Inhaled aviptadil has been studied in a small but encouraging pilot trial for primary pulmonary hypertension. Intravenous aviptadil (branded as RLF-100/ZYESAMI) attracted significant attention during the COVID-19 pandemic as a potential lung-protective agent, but a definitive Phase 3 randomised controlled trial (the TESICO trial, n=461) reported no benefit on the primary endpoint, and the FDA declined emergency use authorisation twice. Because VIP is an endogenous peptide, it is also studied in the context of its endogenous role in sarcoidosis, inflammatory lung disease, and autoimmune conditions, where VIP deficiency has been detected. Research-use-only synthetic VIP peptide is available from laboratory suppliers; its use outside clinical trial contexts carries uncharacterised risks. This entry is for research and educational purposes only.