Definition

An agent composed of substance P (SP) conjugated to the ribosome-inactivating protein and neurotoxin saporin (SAP), isolated from the seeds of the plant Saponaria officinalis (SP-SAP), with potential analgesic activity. Upon administration, SP-SAP targets the SP receptor, neurokinin-1 receptor (NK-1R), located on neurons. When SP-SAP binds NK-1R and the receptor/conjugate complex internalizes, the saporin moiety inactivates ribosomes and prevents protein synthesis, which causes cell death, destroys NK-1R-expressing nerves and decreases pain perception.