Poly(ortho esters) (POE) are hydrophobic and bioerodible polymers that have
been under development since the early 1970s. Up to now, four generations
of such polymers have been described. Of most interest are poly(ortho ester
s) III and poly(ortho esters) IV. POE III is a semi-solid material that has
been shown to be highly biocompatible and is currently being investigated
as a carrier for sustained drug delivery to treat diseases of the posterior
segment of the eye. However, the polymerization is difficult to control an
d is not readily scaled up. POE IV can be easily prepared in a highly repro
ducible manner, is very stable provided moisture is rigorously excluded and
has also been shown to be biocompatible. It is currently under development
for a variety of applications, such as ocular delivery, protein release, a
nd periodontal disease treatment.