title: FDA seeks "comfort factors" before removing hold on porcine xenotransplantation trials.
authors.forename: J L
authors.initials: JL
authors.lastname: Fox
mesh_terms: D000818:Animals; D002986:Clinical Trials as Topic; D017408:Guidelines as Topic; D006801:Humans; D008099:Liver / Q000166:cytology; D017093:Liver Failure / Q000628:therapy; D012190:Retroviridae / Q000472:pathogenicity*; D012307:Risk Factors; D013552:Swine / Q000821:virology*; D014183:Transplantation, Heterologous; D014481:United States; D014486:United States Food and Drug Administration / Q000331:legislation & jurisprudence*