Sumitomo Pharmaceuticals Company Limited

Yoshiharu Ikeda

Keiichi Ono

Yoshiyuki Kai

Polyethylene glycol derivatives of the formula ##STR1## wherein R.sub.1 and R.sub.2 are the same or different and each represents a lower alkyl, m and n are the same or different and each represents a positive integer and p is 0 or a positive integer, peptides modified by the polyethylene glycol derivatives, methods for producing them and use of the modified peptides. The peptides modified by the polyethylene glycol derivatives (I) of the invention, as compared with the corresponding non-modified peptides, show decreased antigenicity, are considerably delayed in biological clearance, and exhibit their physiological activities effectively over a long period, rendering them very effective as pharmaceuticals as well as drugs for animals.

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Somerville, MA, United States of America

Yoshiharu Ikeda