DUROS® implant technology is coupled with proprietary drug delivery catheter and drug formulation technology. DURECT licensed the DUROS® technology for selected fields from ALZA Corporation in 1998. ALZA's Viadur® (leuprolide acetate implant) is the first approved product to be administered via the DUROS® System. The Food and Drug Administration approved the product in March 2000 as a palliative treatment for prostate cancer.

The DUROS system can be used for therapies requiring systemic or site-specific administration of a drug.

To deliver drugs systemically, the DUROS system is placed just under the skin, for example in the upper arm, in an outpatient procedure that is completed in just a few minutes using local anesthetic. Removal or replacement of the product is also a simple, quick procedure completed in the doctor's office. To deliver a drug to a specific site, DURECT is developing proprietary miniaturized catheter technology that can be attached to the DUROS system to direct the flow of a drug to the target organ, tissue or synthetic medical structure, such as a graft. Site-specific delivery enables a therapeutic concentration of a drug to be administered to the desired target without exposing the entire body to a similar dose. The precision, size and performance of the DUROS system will allow for continuous site-specific delivery to a variety of precise locations within the body. The DUROS system is the basis of our CHRONOGESIC® product candidate under development in collaboration with Endo in the U.S. and Canada.

The CHRONOGESIC (sufentanil) Pain Therapy System is a subcutaneous implant that is intended to continuously deliver sufentanil, an opioid medication, for an extended duration. This product under development is intended to treat chronic pain. Sufentanil is an FDA approved opioid that is currently used as an in-hospital anesthetic. CHRONOGESIC is intended for stable, opioid responsive chronic pain patients of malignant and non-malignant origin. Since the product is fully implanted under the skin, this product can allow for greater physician control over administering clinically necessary opioid therapy to chronic pain patients with potentially less risk of misuse, abuse and diversion than traditional pills or patches.

Chronic pain, defined as pain that lasts 6 months or longer, affects as many as one in eight people worldwide (34 million Americans annually). The market for strong opioids in the treatment of pain has been estimated to exceed $4 billion annually.