LY-411575, a potent γ-secretase inhibitor, is with IC50 of 0.078 nM in the membrane and 0.082 nM in cell-based. It also suppresses Notch clevage with IC50 of 0.39 nM.

Notch S3 cleavage:0.39 nM, γ-secretase (cell-based assay):0.082 nM, γ-secretase (membrane-based):0.078 nM

LY-411575 inhibits γ-secretase which can be assessed by the substrates like amyloid precursor protein (APP) and Notch S3 cleavage. [1] LY-411575, which blocks Notch activation, results in apoptosis in primary and immortalized KS cells. [2]

10 mg/kg oral dose of LY-411575 decreases brain and plasma Aβ40 and -42 dose-dependently. [1] LY-411575 reduces cortical Aβ40 in young (preplaque) transgenic CRND8 mice (ED50 ≈ 0.6 mg/kg) and produces significant thymus atrophy and intestinal goblet cell hyperplasia at higher doses (>3 mg/kg). The therapeutic window is similar after oral and subcutaneous administration and in young and aged CRND8 mice. Both the thymus and intestinal side effects are reversible after a 2-week washout period. Three-week treatment with 1 mg/kg LY411575 reduces cortical Aβ40 by 69% without inducing intestinal effects, although a previously unreported change in coat color is observed. [3]

Assays for Aβ and NICD: Procedures for measuring γ-secretase activity in membranes prepared from HEK293 cells expressing APP have been described previously (Zhang L et al Biochemistry 40, 5049-5055). Intact HEK293 cells expressing either APP or NΔE are treated with various concentrations of LY- 411,575 for 4 hours at 37 °C. In the case of cells expressing NΔE, cells are lysed, the cell lysates are separated on a 4-12% NuPAGE gel, and the processed NICD fragment is detected via Western blot with a cleavage site-specific antibody. The inhibition of NICD production is quantified by spot densitometric analysis using FluorChem. In the case of cells expressing APP, the conditioned medium is collected, centrifuged at 10,000 × g for 5 minutes to remove cell debris, and stored at -20 °C prior to the determination of Aβ levels. Aβ40 and -42 produced in HEK293 membrane- and cell-based assays, as well as plasma Aβ40 and cortex Aβ40 from TgCRND8 mice, are analyzed without pretreatment using an electrochemiluminescence detection-based immunoassay. Plasma Aβ42 is measured by enzyme-linked immunosorbent assay. A commercially available enzyme-linked immunosorbent assay kit is used to measure cortex Aβ42 according to the manufacturer''s instructions.

DNA/PI staining is performed using standard methodologies. Briefly, 1 × 106 cells are permeabilized with 100% ethanol in the presence of 15% FBS. The cells are washed and then treated for 15 minutes at 37 °C with 10 mg/mL RNAse. PI (5 mg/mL) is added, and the cells incubated for 1 hour at 4 °C prior to analysis by flow cytometry with 10 000 cells analysed per gated determination. The results are confirmed using the Immunotech Annexin V staining kit following the manufacturers’ instructions. At least three independent experiments are performed showing similar results.