A macrocyclic polypeptide represented by formula (I) or a pharmacologically acceptable salt thereof, wherein X aa1 is a residue of Arg, Lys, His, Gly, Ala, Asn, Thr, Ser, Met, Leu, Ile, Val, Gln, Phe, Tyr, Trp, or Cys, or is absent; X aa2 is a residue of Phe, Tyr, Trp, 2Nal, 4CF, or DCF; X aa3 is a residue of Ile, Leu, Nle, Tle, Trp, 2Nal, 4CF, or Arg; X aa4 is a residue of Ser; X aa5 is a residue of Gly; X aa6 is a residue of Arg, Lys, His, Ser, Cit, or MO2; X aa7 is a residue of Asn or Asp; X aa8 is a residue of Trp, 2Nal, or 6CW; X aa9 is a residue of Val, Nle, Ahp, or Met; X aa10 is a residue of Arg, Lys, His, AMF, Phg, or Val; X aa11 is a residue of Trp or 2Nal; X aa12 is a residue of Val, Tle, or Phe; wherein 2Nal represents , 4CF represents DCF represents Nle represents Tle represents Cit represents MO2 represents 6CW represents Ahp represents AMF represents Phg represents A is a linking group of the formula: wherein represents a point of attachment to the N-terminal amino group of X aa1 , or in the absence of X aa1 , represents a point of attachment to the N-terminal amino group of X aa2 , represents a point of attachment to the C-terminal carbonyl group of X aa12. or a pharmacologically acceptable salt thereof, wherein X aa1 is a residue of Arg, Lys, His, Gly, Ala, Asn, Thr, Ser, Met, Leu, Ile, Val, Gln, Phe, Tyr, Trp, or Cys, or is absent; X aa2 is a residue of Phe, Tyr, Trp, 2Nal, 4CF, or DCF; X aa3 is a residue of Ile, Leu, Nle, Tle, Trp, 2Nal, 4CF, or Arg; X aa4 is a residue of Ser; X aa5 is a residue of Gly; X aa6 is a residue of Arg, Lys, His, Ser, Cit, or MO2; X aa7 is a residue of Asn or Asp; X aa8 is a residue of Trp, 2Nal, or 6CW; X aa9 is a residue of Val, Nle, Ahp, or Met; X aa10 is a residue of Arg, Lys, His, AMF, Phg, or Val; X aa11 is a residue of Trp or 2Nal; X aa12 is a residue of Val, Tle, or Phe; wherein 2Nal represents , 4CF represents DCF represents Nle represents Tle represents Cit represents MO2 represents 6CW represents Ahp represents AMF represents Phg represents A is a linking group of the formula: wherein represents a point of attachment to the N-terminal amino group of X aa1 , or in the absence of X aa1 , represents a point of attachment to the N-terminal amino group of X aa2 , represents a point of attachment to the C-terminal carbonyl group of X aa12. X aa2 is a residue of Phe, Tyr, Trp, 2Nal, 4CF, or DCF; X aa3 is a residue of Ile, Leu, Nle, Tle, Trp, 2Nal, 4CF, or Arg; X aa4 is a residue of Ser; X aa5 is a residue of Gly; X aa6 is a residue of Arg, Lys, His, Ser, Cit, or MO2; X aa7 is a residue of Asn or Asp; X aa8 is a residue of Trp, 2Nal, or 6CW; X aa9 is a residue of Val, Nle, Ahp, or Met; X aa10 is a residue of Arg, Lys, His, AMF, Phg, or Val; X aa11 is a residue of Trp or 2Nal; X aa12 is a residue of Val, Tle, or Phe; wherein 2Nal represents , 4CF represents DCF represents Nle represents Tle represents Cit represents MO2 represents 6CW represents Ahp represents AMF represents Phg represents 2Nal represents , 4CF represents DCF represents Nle represents Tle represents Cit represents MO2 represents 6CW represents Ahp represents AMF represents Phg represents A is a linking group of the formula: wherein represents a point of attachment to the N-terminal amino group of X aa1 , or in the absence of X aa1 , represents a point of attachment to the N-terminal amino group of X aa2 , represents a point of attachment to the C-terminal carbonyl group of X aa12. <EOS>