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A new targeted intravenous conjugate of nystatin with pentaerythritol poly(ethylene glycol)ether has been prepared and characterised (NY4–sPEG, M = 25 160). The conjugate contains a β-d-glucopyranoside molecular switch sensitive to β-glucosidases (E.C.188.8.131.52), which are specifically present in the enzyme outfit of fungal pathogens. The investigated conjugate is stable under in vitro conditions for 24 h (solution of phosphate buffer pH = 7.4). Spectrophotometrically controlled releasing of nystatin in model medium containing β-glucosidase ((Aspergillus niger) 2 mg/mL, 66.6 units/g; pH 7.4, 2 × 10−2 M), reported decomposition half-life of conjugate τ1/2 = (88 ± 2) s. This implies that releasing of nystatin is controlled only enzymatically.