GlaxoSmithKline (GSK) has developed a potential cure for severe combined immune deficiency, though it will cost $665,000 for a single dose. The drug, autologous CD34+ enriched cell fraction (Strimvelis), is a gene therapy for the inborn illness that leaves children unable to protect themselves against infection. Without treatment, children with the disease die before age 2 years. But a single administration of GSK's therapy kept 100% of patients alive after 3 years in a small clinical trial, and that was enough to convince European regulators to approve it in May. But GSK will need to convince payers to fork over huge, one-time sums for treatments whose long-term effects are still unknown. Some argue the rise of gene therapy demands new approaches to how drugs are reimbursed. One idea put forth is to require drug makers to issue a sort of warranty, promising to give a refund or pay for additional treatment if a gene therapy stops working. Meanwhile, drug companies and venture capitalists are pouring billions of dollars into gene therapy projects in hopes of shuttling more one-time treatments onto the market in the coming years.