But when making decisions on drugs to treat a very rare disease -- known as orphan drugs -- the agency tends to be more flexible. Orphan drugs won't be used in large numbers of people, and often the diseases they treat are fatal, so patients are willing to accept more risk from the drug than would the general population.
Members of the panel heard from a dozen FAP patients urging approval of tafamidis. In some cases, patients' family members -- a grandparent, aunts, uncles, cousins, and a parent -- were all suffering or had already died from FAP, which is highly hereditary.
"This is a disease that wipes out families," one patient told the panel.
Although the tafamidis's efficacy wasn't particularly good, it also doesn't have many side effects, and patients with FAP need some therapeutic option, the patients said.
"If we do approve it, a lot of people will be helped and no one will be hurt," FAP patient Geri O'Brien told the panel. "If we don't approve it, no one will be helped, research will be stymied, and we will have to wait for another 10 years."