Unlike a drug delivery pump, which typically remains attached to the body and has only a feeder line implanted into the patient with all the device controls and access ports being available on the outside, a fully implanted device would be expected to remain autonomous for extended periods of time. Under such conditions, issues such as drug stability, reliability of drug release, acceptance of the device by the host, and stability of communication to control the drug delivery regimen, will all have to be resolved. The present work provides key evidence that producing such small, fully implanted, remotely controlled drug delivery devices is possible.
Robert Langer's team used human parathyroid hormone fragment 1–34 (hPTH(1–34)) as the proof-of-concept drug in a clinical trial of an implanted microchip-based drug delivery device controlled through wireless communication (Figure 1). hPTH(1–34) is the active ingredient of teriparatide, a drug used to treat osteoporosis in patients with elevated risk of bone fractures. The delivery of teriparatide needs to be controlled very carefully because its continuous administration can lead to the unwanted effect of promoting bone loss. The implanted delivery device therefore consisted of two microchips containing 10 small drug delivery reservoirs each; these were designed to deliver individual drug doses of 40 μg upon electrothermal ablation of a thin metallic membrane that covered each reservoir.