The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) requires the generation of a custom Single-Domain Antibody targeting the human Calcium-Sensing Receptor for use in parathyroid tumor imaging and treatment. The contractor must deliver 0.5 to 1 mg each of four purified, validated, and 3XFLAG-tagged sdAb clones, along with corresponding DNA minipreps and complete sequence information. The contract will be awarded as a Firm Fixed Price, with evaluation factors prioritizing technical approach and past performance over cost. Performance of the services will take place in Bethesda, MD. The closing response date for proposals is May 24, 2026, at 9:00 AM Eastern Daylight Time.