Figure 10.

Cell culture assays responsive to human interferon-α (IFN-α; A) or human erythropoietin (EPO; B) were used to compare the potencies in vitro of analogous conjugates of these cytokines with HO-PEG and mPEG. A: Human lymphoma cells (Daudi cells) were treated for 3 days with serial dilutions of IFN-α (◆), with monoPEGylated conjugates of IFN-α made with 20 kDa mPEG (▲; mPEG₁-IFN-α) or 20 kDa HO-PEG (△; HO-PEG₁-IFN-α), or with diPEGylated conjugates of IFN-α made with 20 kDa mPEG (■) or with 20 kDa HO-PEG (□). After incubation of the cells with Alamar Blue, the fluorescent signal was measured to quantify cell growth, from which the percent of inhibitable cell growth was calculated. (B) Human erythroleukemic cells (TF-1 cells) were treated for 3 days with serial dilutions of EPO (◆), with a monoPEGylated conjugate with 30 kDa mPEG (▲; mPEG₁-EPO; Mircera), or with a monoPEGylated conjugate with 30 kDa HO-PEG (△; HO-PEG₁-EPO). After incubation of the cells with Alamar Blue, the fluorescent signal was measured to quantify cell growth, from which the percent of maximal cell growth was calculated.