Specificity and activity of KY1070. (A) Cross-reactivity of KY1070 against human, rat, and mouse BMP6 was tested using a HepG2 Hamp luciferase reporter gene cell line. After assessing the assay window using a range of concentrations, a fixed concentration of recombinant human, rat, or mouse BMP6 of 10 nM was used. KY1070 inhibition curves were generated by titration starting at a final concentration of 600 nM. A human IgG4 isotype control was included in each assay. (B) KY1070 specificity was tested against human BMP5 and BMP7. HepG2 Hamp luciferase reporter gene cells were stimulated with a fixed concentration of recombinant human BMP5 or BMP7 of 10 nM. Inhibition curves for KY1070 were generated by titration starting at a final concentration of 600 nM. A titration of commercially available murine anti-BMP5 and anti-BMP7 antibodies as well as a human IgG4 isotype control was included. (C) BMPR1A/ BMPR2 dimerization assay performed in transfected U2OS cells. Dimerization was induced using human BMP6 (Peprotech 120-06) used at a fixed final concentration of 200 ng/mL. KY1070 inhibition curves were generated by titration starting at a final concentration of 600 nM. A human IgG4 isotype control was included. (D) Liver Hamp mRNA levels and plasma hepcidin levels of Bmp6 wild-type and Bmp6^−/− mice determined 3 days after a single injection of IgG4 isotype antibody (3 mg/kg; n = 4 [Bmp6 Wt]; n = 8 [Bmp6^−/−]) or KY1070 (3 mg/kg; n = 5 [Bmp6 wild type]; n = 9 [Bmp6^−/−]). Unpaired Student t test was applied for comparison between genotypes for panel D. Data are presented as means ± SEM. **P < .01. RLU, relative light units.