The FDA issued draft guidance recommending that biopharma firms can, in many cases, reduce or avoid long-duration nonhuman primate (NHP) studies during preclinical monoclonal antibody development. The agency suggested that studies beyond three months in nonrodent species are often unnecessary when supplemented with a weight-of-evidence risk assessment and other supporting data. The guidance aims to modernize nonclinical safety packages and reduce reliance on NHPs where scientific justification supports alternatives. Regulators framed the move as aligning study durations with risk while encouraging sponsors to leverage mechanistic and comparative data. The draft will be open for comments as the agency balances animal welfare, scientific rigor, and international harmonization.