 Dose escalation in solid tumors utilizing a 33 design with intra-subject dose escalation. 3 dose levels of rSIFN-co are planned for determining the RD. 3-6 subjects will be assigned to each dose level and followed up for 4 weeks after starting administration in Cycle 1. Each cohort will be started after the tolerability of that dose level has been confirmed in subjects with advanced solid tumors. For subjects starting in the lower dose cohorts, intra-subject dose escalation will be allowed till grade 34 toxicity is encountered or 24μg TIW is reached. In order to minimize the risk of allergic reactions, the sponsor has advised a lead-in period starting from 15μg. When the tolerability of each dose level has been confirmed by the observation of no DLT among 3 subjects, escalation to the next dose level will occur. 