{HEAD ~ A prodrug} comprises {TAIL ~ a polyhydroxylated polyamine} to which a drug is linked by the intermediary of a peptidyl group 
comprises
{ HEAD ~ A prodrug } comprises { TAIL ~ a polyhydroxylated polyamine } to which a drug is linked by the intermediary of a peptidyl group
HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH