Significance: Alzheimer's disease is the most common form of dementia, currently the most expensive element in the healthcare system in developed countries. Alzheimer's disease is an irreversible, progressive neurodegenerative disorder characterized by gradual loss of memory and cognitive skills. The disorder in the metabolism of Aβ peptide is considered to be the central mechanism of Alzheimer's disease. For now, only ineffective symptomatic treatment is available and therefore the pharmaceutical industry is making great efforts to find a drug that would slow down progress or prevent the onset of Alzheimer's disease. Therefore, one of the main targets in drug research for Alzheimer's disease is the intramembrane protease γ-secretase which produces toxic Aβ peptides. Results: We first optimized the sandwich ELISA method for quantification of the intracellular Aβ 1-40 peptide in low physiological concentrations, to avoid use of genetically modified SH-SY5Y cells. Optimized high-sensitivity ELISA tests were used to investigate potential drugs from JIVA Pharma company. All of the tested JIVA compounds showed inhibition of γ-secretase activity at concentrations of 10 μM and 100 μM, and none of the compounds changed the cell morphology or caused their death. At a concentration of 10 μM, the highest inhibition was shown by the compound JIVA 025, while at a concentration of 100 μM, the highest inhibition was shown by JIVA 024 and JIVA 038. Although compounds JIVA 025, JIVA 027 and JIVA 042 showed inhibition of γ-secretase activity greater than 50% in both tested concentrations, differences in inhibition strength were not significant. Conclusion: Compounds JIVA 024 and JIVA 038 showed a significant difference in inhibition of γ-secretase activity when used at different concentrations and showed potential for further structure optimization.