A single magic bullet is not enough for treatment of metastatic cancers. However, administration of a combination of free drugs can be extremely challenging because of the inability to control the correct choice of dosages and definitive delivery of the effective drug ratio at the target tissue due to the differences in pharmacokinetics and biodistribution of individual drugs. Here we report an engineered biodegradable polymer Containing combination therapeutics that can be self-assembled into a controlled release nanoparticle with abilities to deliver multiple therapeutics in a predefined ratio following temporal release patterns. This platform technology can lead to a rationally designed combination therapy.