Recent Progress in Polymer Therapeutics as Nanomedicines - Harnessing Biomaterials in Nanomedicine: Preparation, Toxicity, and Applications - page 91

biomedicine has seen significant growth [79]. Polymeric drugs
off er selective recognition and sequestration of molecular and
macromolecular species. The presence of detrimental substances in
the human GI beyond a certain concentration has been implicated as
the causative agent for diff erent diseases. The well-established and
FDA-approved polymeric drugs are specified to other diseases than
cancer. However, it is inevitable that further research will be carried
out regarding treatment of cancer by polymeric drugs.
One family of polymeric drugs has been found to be eff ective
in removing those undesired agents from the body at acceptable
therapeutic doses and has shown therapeutic benefits in various
human diseases. For the treatment of cardiovascular diseases,
several cholesterol-lowering agents were developed [80-86], which
have also showed efficiency in the control of hyperglycemia [87-89].
Welchol ® is a cholesterol-binding polymer, which was approved in
2000 for the reduction of elevated LDL-C and in 2008 for the reduction
of glucose type-2 diabetes. For the treatment of renal diseases,
amines containing cationic hydrogels or cross-linked polymers were
designed and synthesized. These polymers act as safe and eff ective
phosphate binders, and their discovery led to the development and
approval of Renagel ® in 1998 [90-94]. Similarly, this family off ers
several iron chelators in the case of iron overload disorders [95-99]
and polymeric sequestrants of C. difficile toxins, such as Tolevamer,
which has shown efficacy in human clinical trials [100].
Another family of polymeric drugs is based on chemically
modified biomedical polymers as treatments for osteoarthritis
[101-103]. The onset of this disease is characterized by degradation
of hyaluronan (HA), which is an anionic biopolymer that provides
the viscoelastic properties for the normal function of the joints. A
variety of HA and chemically cross-linked HA have been approved
as visco-supplements for patients with osteoarthritis (i.e., Artz ® ,
Hyalgan ® , and Synvisc ® ). In addition, HA-based products are also
used in the area of reducing the extent and severity of post-surgical
adhesion [104-106].
The design and synthesis of functional polymers showed inherent
therapeutic efficacy. In spite of the progress in this area (Table 4.3),
there are some underlying concerns attributed to polymers as new
chemical entities for therapeutic applications, including the issue
of broad molecular weight distribution and compositional and
structural heterogeneity. These features were considered to impede