Roche switched professional agencies for its top-selling hepatitis C therapy Pegasys to Omnicom’s Harrison & Star from echo Torre Lazur, part of Interpublic Group’s McCann Healthcare Worldwide.The move followed a three-way pitch among Harrison & Star, GSW and one other agency.Pegasys is the world’s best-selling treatment for chronic hepatitis C. The drug brought in $1.13 billion in revenue last year, a 17% increase over 2004.