A phase IIb study [34] reported that HCV patients (genotypes 1 and 4) had significantly higher response rates to treatment with PEG-IFN-λ1 versus PEG-interferon α-2a, with the additional advantages of PEG-IFN-λ1 over PEG-interferon α-2a including lower frequency of adverse events, decreased frequency of flu-like symptoms, anemia, and musculoskeletal symptoms, and rarely observed neutropenia and thrombocytopenia. The gene discussed is IFNL1; the disease is anemia.