Because of the economics of drug development, there's no stockpile of ZMapp or any other drug known or thought to be effective in the fight against of Ebola. “A stockpile sounds great,” said Alan Barrett, director of the UTMB’s Sealy Center for Vaccine Development. “But you can only stockpile for so long. Nothing is stockpiled beyond three years.” Small companies rely on government and nonprofit funding to pay for the years of clinical trials and testing required to ensure the drugs and vaccines they develop are effective and safe for humans. Development costs can surpass $1 billion. They start by producing a few doses, not hundreds of thousands, said Barrett.