As far as our digestive system is concerned, peptides are foodstuffs to be broken down, not therapeutics to be kept intact until they enter the bloodstream. Peptide drugs, then, must run a gauntlet of countless degradative enzymes. Few have what it takes to stand the punishment. To give peptide drugs a sturdier backbone, researchers at the Ecole Polytechnique Fédérale de Lausanne (EPFL) have been developing double-bridged peptides, that is, peptides that are cyclized by two chemical bridges.