Based on the established concept of prodrug formulation, we conceived the idea of codrugs, or mutual prodrugs. In a prodrug, a small, usually inert moiety, such as a valyl or dipivalyl group, is attached to the parent drug, often with an ester or carbamate bond. We reasoned that this inert moiety could be replaced by another active drug with the appropriate chemical and physical properties. Control Delivery Systems Inc (now pSivida Inc), the principal investigator’s previous company, has received a broad patent for the use of codrugs to achieve sustained release drug delivery. In January of 2007, pSivida licensed these patents to Auritec Pharmaceuticals. We are currently developing antiviral, antibiotic and anti-inflammatory products based on this technology.