Neoleukin Therapeutics, Inc. announced that on January 7, 2021, it received a clinical hold letter from the U.S. Food and Drug Administration (FDA) related to its Investigational New Drug (IND) Application to begin a Phase 1 clinical program of its immunotherapeutic candidate, NL-201. The FDA has informed Neoleukin that it needs to develop a new assay that more precisely measures the amount of protein being administered and demonstrate with this assay that dose and administration procedures will accurately deliver the intended dose of NL-201. The FDA also had additional requests not related to the clinical hold to be addressed by amendment of the IND.