Eppin

Also known as: Cancer/testis antigen 71, Epididymal protease inhibitor, Protease inhibitor WAP7, Serine protease inhibitor-like with Kunitz and WAP domains 1, WAP four-disulfide core domain protein 7, EPPIN, O95925

**Mechanism of Action** Eppin (Epididymal protease inhibitor) is a serine protease inhibitor predominantly expressed in the male reproductive tract, particularly in the epididymis and testis. It contains both Kunitz-type and WAP (whey acidic protein) four-disulfide core domains, enabling it to inhibit serine proteases such as prostate-specific antigen (PSA) and acrosin. This inhibition is critical for regulating sperm motility, capacitation, and the acrosome reaction. Eppin also binds to the sperm surface via interactions with semenogelin and other seminal plasma proteins, contributing to the formation of a protective coating that modulates sperm function during transit through the female reproductive tract. **Key Research Findings** Preclinical studies demonstrate that Eppin is essential for male fertility; targeted disruption of the Eppin gene in animal models leads to impaired sperm motility, abnormal acrosome integrity, and reduced fertilization capacity. Immunocontraceptive approaches using Eppin as an antigen have shown promise in inducing reversible infertility in male primates without significant hormonal side effects. Additionally, Eppin expression has been detected in certain cancers (e.g., lung, breast, and ovarian tumors), where it may function as a cancer/testis antigen, though its role in oncogenesis remains under investigation. **Clinical Relevance** Eppin is primarily investigated as a target for non-hormonal male contraceptives, given its restricted expression in the reproductive tract and its critical role in sperm function. Its immunogenicity also positions it as a candidate for cancer vaccine development, particularly for tumors expressing this antigen. However, all applications remain at the experimental stage, with no approved therapies or diagnostics currently available. For research purposes only — not medical advice.

Key data

Mechanism of action

Serine protease inhibitor that plays an essential role in male reproduction and fertility. Modulates the hydrolysis of SEMG1 by KLK3/PSA (a serine protease), provides antimicrobial protection for spermatozoa in the ejaculate coagulum, and binds SEMG1 thereby inhibiting sperm motility

Research & studies

Frequently asked questions

Related peptides