Since the introduction of recombinant human growth hormone and insulin a quarter century ago, protein therapeutics has greatly broadened the ho- zon of health care. Many patients suffering with life-threatening diseases or chronic dysfunctions, which were medically untreatable not long ago, can attest to the wonder these drugs have achieved. Although the ?rst generation of p- tein therapeutics was produced in recombinant Escherichia coli, most recent products use mammalian cells as production hosts. Not long after the ?rst p- duction of recombinant proteins in E. coli, it was realized that...