The most interesting drugs in development are the small molecules, inhibitors of the HCV enzymes of virus replication: protease, helicase and polymerase. An oral HCV serine protease inhibitor (BILN 2061, Boehringer Ingelheim Pharma KG, Biberach, Germany) was administered to 31 patients of genotype 1 without extensive fibrosis (25, 200 and 500mg) over 2 days versus placebo in an open sequential group comparison.126 Viral load decreased by at least 1 log in 25 out of 26 treated patients, and no response was observed in five patients receiving the placebo. Viral load returned to baseline levels within 1-7 days. In another randomized, double-blind comparison, 10 patients of genotype 1 with extensive fibrosis, but without decompensated cirrhosis, were treated orally with 200mg BILN 2061 or placebo over 2 days. Viral load decreased by at least 2 logs in 8/8 patients treated and 0/2 in the placebo group (Figure 16.3). Analysis of adverse events, vital signs, routine laboratory tests and ECG did not reveal relevant druginduced changes in any of these 34 treated patients.