This invention provides pharmaceutical compositions comprising polymeric matrices, especially those comprising IL-6 as an active ingredient. Specific novel poly(ethylene carbomate) polymers are also provided for more general use as matrix materials in sustained release compositions containing pharmacologically active compounds, as are methods of using of IL-6 for treatment of conditions mediated by IL-1 and/or TNF á, e.g., certain autoimmune and inflammatory conditions, as well as septic shock.