ADCs Toxins, Cordycepin from Cordyceps militaris. Cordycepin blocks revovery of non-heat-shock mRNA translation following heat shock in Drosophilla. Antileukemic activity and mechanism of action of cordycepin against terminal deoxynucleotide transferase-positive leukemic cells has been reported. Cordycepin blocks the Smad signaling by 3`-deoxyadenosine (a mechanism for its anti-fibriotic potential).