Human Anti-HPN Recombinant Antibody (clone mAb55)

(A)Inhibition of hepsin activity by antibody mouse Mab 2.7.35 (= mH35) (squares), chimeric Mab 2.7.35 (= chH35) (circles) and Mab55 (= hH35) (triangles). After preincubation of antibodies with hepsin for 30 minutes, hydrolysis reaction was started with addition of Ac-KQLR-AMC peptide. Fluorescence increase was measured after 40 minutes incubation. The IC50 values were calculated after fitting the % inhibition data to a four-parameter equation. Error bars represent standard deviation from three experiments. (B) Adjusted surface plasmon resonance (Biacore) sensogram analyzing binding of hepsin to immobilized antibody Mab55 (= hH35). Hepsin was injected at concentrations 0-200 nM. Curve fittings using a 1:1 Langmuir binding model are shown by black lines. (C) Comparison of binding and dissociation constants for mouse Mab 2.7.35 (= mH35), chimeric Mab 2.7.35 (= chH35) and Mab5(= hH35) antibodies analyzed by surface-plasmon resonance measurement.

(A) HEK293 cell lines that stably overexpress full length hepsin with a C-terminal GFP fusion tag were analyzed by flow cytometry. By incubation with increasing amounts of Mab55, specific and saturable surface staining could be detected. (B) Surface staining is confirmed by confocal laser scanning microscopy analysis. Untransfected cells (HEK293 wt) did not display any detectable binding.

(A) Activity of hepsin antibodies against other serine proteases. For assessing the inhibitory potential of the antibodies on other serine proteases the same test conditions as for hepsin were used. Hepsin (1 nM), Matriptase (2 nM), HAT (2 nM), Enteropeptidase (0.7 nM), Trypsin (1.8 nM) were incubated with antibody (500 nM) for 30 minutes and reaction was started with 5 MM Ac-KQLR-AMC peptide. Data are shown for three replicate experiments. (B) Activity of antibody Mab55 analyzed in a FRET activity assay against human hepsin (blue), cynomolgus (brown) and mouse (magenta). Cross reactivity was found against cynomolgus, but not against mouse hepsin. IC50 values are stated accordingly. (C) Progress curve of hepsin inhibition by Mab55 (= hH35). Hepsin (1 nM) was added to a mixture of Ac-KQLR-AMC peptide (10 MM) and 0, 111.1, 333.3 and 1000 nM of Mab55. The increase of fluorescence was monitored at 10-second intervals over 200 seconds. The amidolytic activity of hepsin in absence of antibody shows a straight line (R2 = 0.9946). (D) Eadie-Hofstee plot of hepsin inhibition by mouse Mab 2.7.35. Hepsin (1 nM) was preincubated without (filled circles) or with Mab55 (= hH35) (20-0.31 nM in 2-fold dilution steps) for 15 min. After addition of Ac-KQLR-AMC peptide (40, 20, 10, 5, 2.5 MM) the linear rates of the increase in fluorescence were measured on a kinetic microplate reader. The plot for the top-ranked mixed tight inhibition model is shown (Vmax=0.81±0.01 MM AMC/min and Km=13.65±0.44 MM for control; alpha=1.3±0.3). Data are plotted as mean ±SD for n=3.