There is currently great interest in developing acid-sensitive materials for drug delivery because of their ability to hydrolyze in the acidic environment of phagosomes and release drugs into the cytoplasm. In this presentation, we introduce a new acid-sensitive polymer for drug delivery, poly(cyclohexane-1,4-diyl acetone dimethylene ketal) (PCADK), which is ideal for treating inflammatory diseases because of its biocompatible degradation products. PCADK was synthesized using the acetal exchange reaction between 1,4-cyclohexanedimethanol and 2,2-dimethoxypropane. PCADK hydrolyzes into innocuous compounds, 1,4-cyclohexanedimethanol and acetone, which have FDA approval for human use. The hydrolysis half-life of PCADK is 24.1 days at pH 4.5 and over 4 years at pH 7.4, which is suitable for targeting chronic diseases. The therapeutic enzyme superoxide dismutase (SOD), which scavenges reactive oxygen species, was encapsulated into PCADK-based microparticles using a double emulsion procedure. Cell culture experiments demonstrated that PCADK-based microparticles significantly improved the ability of SOD to scavenge reactive oxygen species produced by macrophages. We anticipate the use of PCADK to treat a wide variety of chronic inflammatory diseases such as lung fibrosis, arthritis, and congestive heart failure.