PROBLEM TO BE SOLVED: To provide a sustained-release preparation of evocalcet or a pharmaceutically acceptable salt thereof. SOLUTION: A polyethylene glycol derivative is bonded to an amino group of evocalcet (4-(3S-(1R-(1-naphthyl)ethylamino)pyrrolidin-1-yl)phenylacetic acid represented by the following formula, Evocalcet polyethylene glycol derivative or pharmaceutically acceptable derivative of evocalcet, which has calcium-sensing receptor activating effect and is expected to show anti-parathyroid function by decreasing blood PTH (parathyroid hormone) concentration salt. [Selection diagram] None【課題】エボカルセト又はその薬学的に許容される塩の持続性製剤の提供。【解決手段】下記式で表される、エボカルセト（4-(3S-(1R-(1-ナフチル)エチルアミノ)ピロリジン-1-イル)フェニル酢酸）のアミノ基にポリエチレングリコール誘導体を結合させた、カルシウム感受性受容体活性化作用を有し、血中PTH（副甲状腺ホルモン）濃度の低下を通じて抗副甲状腺機能亢進作用を示すことを期待される、エボカルセトのポリエチレングリコール誘導体又はその薬学的に許容される塩。【選択図】なし
