A delivery system comprising a covering having at least two compartments is provided. A first compartment contains a first therapeutic agent and the second compartment can be unfilled and is configured to receive a second therapeutic agent. The first compartment and the second compartment are separated by at least one removable separation member, for example a drawstring, that can be pulled to allow the first and second therapeutic agents to mix prior to delivery at a selected surgical site. Either the first or second compartment of the covering define an opening further comprising a pre-attached sealing member, which can be a flap sealable by heat, sutures, pressing or interference fittings. The opening of the empty compartment can be configured to receive a filling member, such as a funnel fitted with a spring loaded clip for temporary attachment to the covering. A method of treating a bone defect in a patient utilizing the delivery system is also provided.