FIELD: medicine. SUBSTANCE: described is narrow poly-and mono-dispersed water- soluble oligomer which has polydispersity ratio from 1.0 to 1.3 and is polyurea of formula I: 
wherein R is hydrogen atom, C1-C4 alkyl group, phenyl group or phenyl group substituted by 1 to 2 fragments of R1 and having up to 3 substituents independently selected from chlorine or bromine atoms or C1-C4 alkyl groups; R1 is SO3R2, -CO2R2, -PO3(R2)2 or -OPO3R2; R2 is hydrogen atom or pharmaceutically acceptable cation; m is integer of 0 or 1 provided that if m is O, R is hydrogen atom, X is aromatic substituent which is defined in claim 1, Y is CO2-, -C=C-, -N=N- or (a) 
n is integer of 3-15, and R3 is R or -X-NH2, wherein R and X are as defined above. Compounds have biological activity against virus of human immunodeficit. Also described are pharmaceutical agent based thereon, method of preparing oligomer, method of inhibiting activity of viruses. EFFECT: improved properties of the pharmaceutical agent, and more efficient inhibition method. 27 cl, 15 dwg, 6 ex, 3 tbl
