Stable pharmaceutical formulations and drug delivery devices are disclosed. In certain embodiments, the drug delivery device contains a reservoir when implanted into a patient is in partial contact with the tissue environment. The reservoir remains in contact with the environment via a porous structure in the housing of the delivery device. The reservoir contains a combination of the therapeutic biomolecule and a second molecule that serves to stabilize and restrict the solubility of the therapeutic biomolecule, thereby controlling the amount of therapeutic biomolecule that is in solution. The concentration of the soluble therapeutic biomolecule or the size of the surface area of the porous structure controls the rate of delivery of the therapeutic biomolecule to the target tissue.
