This is a non-competitive, sole-source combined synopsis/solicitation in which NIH/NLM intends to award without full and open competition to Progenics Pharmaceuticals Inc. for tau radiotracers, justified by scientific continuity. The contractor would provide 70 tau radiotracers, with pricing for an optional 80 radiotracers, to support the Baltimore Longitudinal Study on Aging. The Government anticipates a firm-fixed-price purchase order with delivery 30 days after receipt of order. The anticipated award date is November 20, 2026. Evaluation, if competition is pursued based on responses, would be lowest-priced technically acceptable.