Specific activity, total activity, and total antigen of hFIX variants expressed in different cell lines. Specific activity (A,C,E) and total activity and antigen (B,D,F) FIX variants expressed in the specified liver cell line. Bars or square points represent the mean specific activity of ≥3 independent transient transfections, and errors bars represent ± standard error of the mean. For clarity, variants are grouped as (1) high specific activity and total activity across all cell lines (L, E, Q, A, S, M, H; red and pink, respectively), (2) low specific activity and total activity across all cell lines (R, K, N, P; blue), (3) medium specific activity and total activity across all cell lines (C, Y, G, I, D; black), and (4) variable specific activity and total activity across all cell lines (F, W, V, T; green). Summary of specific activity (G) and total activity (H) across cell lines with each letter represents the average of ≥3 independent transient transfections.