<b>Abstract</b>— <p>Modular nanotransporters are a drug delivery system developed for targeted cancer treatment. Modular nanotransporters are macromolecules made up of several transport modules. They can transfer active principles to susceptible compartments of cancer target cells. Their endosomolytic module promotes pH-dependent pore formation in endosomal membranes, ensuring the modular nanotransporters endosome escapes into the cytosol of the target cell following receptor-mediated endocytosis. The membranolytic activity of modular nanotransporters can be assessed by their ability to cause leakage of phosphatidylcholine liposomes loaded with a fluorescent dye in a concentration that causes fluorescence self-quenching. To study the kinetics of the process, we used sulfo-cyanine dye, the fluorescence of which does not depend on pH. Using this approach, we investigated the membranolytic kinetics of two modular nanotransporters for targeted delivery of drugs within cells overexpressing the epidermal growth factor receptor. A modular nanotransporter with an endosomolytic module at the N-terminus of the molecule has significantly faster kinetics compared to a modular nanotransporter that has a ligand module at the N-terminus. Our results helped us better understand the early stages of the interaction of modular nanotransporters with the phospholipid bilayer and identified the settings that are more suitable for further investigation.</p>