FIELD : medicine. SUBSTANCE : group of inventions relates to medicine, specifically to oncology, and can be used to obtain a conjugate for the treatment of a subject with a proliferative disorder. Conjugate ʺderivative of monomeric N-acetyl-gamma calicheamicin / anti-CD22 antibodyʺ is represented by formula Pr(-X-W)m, where : Pr is an anti-CD22 antibody. Antibody contains SEQ ID NO : 1 for CDR-H1, SEQ ID NO : 2 or SEQ ID NO : 13, or SEQ ID NO : 15, or SEQ ID NO : 16, or the sequence GINPGNQYTTYKRNLKG, or the sequence GINPGNNYATYRRKFQG for CDR-H2, SEQ ID NO : 3 for CDR-H3, SEQ ID NO : 4 for CDR-L1, SEQ ID NO : 5 for CDR-L2 and SEQ ID NO : 6 for CDR-L3. X is a bifunctional linker containing 4-(4-acetylphenoxy)butanoic acid (AcBut). W is N-acetyl-gamma calicheamicin, m is the average load for the purified conjugation product, such that calicheamicin is 4–10 % by weight of the conjugate and (-X-W)m is a dimethyl hydrazide of AcBut-acetyl-gamma-calicheamicin. Group of inventions also relates to a method of treating a subject with a proliferative disorder. EFFECT : use of this group of inventions allows to obtain a conjugate ʺderivative of monomeric N-acetyl-gamma calicheamicin / anti-CD22 antibodyʺ with a high drug load and with a low content of low-conjugated fraction (LCF). 32 cl, 8 ex, 13 tbl, 29 dwg