Why is gene therapy tail coverage so expensive?

Gene-therapy tail is expensive because the window in which a claim can be reported is unusually long. FDA expects long-term follow-up of gene-therapy subjects for as long as 15 years, to detect delayed events such as insertional oncogenesis. Since clinical trial liability and products coverage are usually claims-made, the insurer providing the tail is on risk for claims that may not surface for a decade or more after the therapy was administered.

A tail (or extended reporting period) extends the time to report claims after a policy ends. For most indications a few years of tail is sufficient; for gene therapy, the tail may need to run many years to align with the long-term-follow-up period, and the longer the tail and the more severe the potential injury, the more it costs.

The practical takeaway is to treat the tail as a planned, budgeted cost from the start rather than a surprise at trial close-out, exit, or acquisition. Preserving the retroactive date across renewals and carriers, and budgeting the tail early, is the difference between a funded and an unfunded long-tail exposure.