Germline gene therapy is a potential method of treatment for rare genetic disorders and other common diseases that delivers a specific gene to target cells that would change a person's genomic structure. It has not been available outside of clinical trials.
Germline gene therapy modifies existing germ cells (sperm and egg) by introducing genes and integrating these genes into their genomes. This is envisioned to transfer inheritance to offspring, thereby changing those genes forever.
Hurdles to germline gene therapy are influenced by how the gene is transferred to the cell, oftentimes through viruses which cause other responses.