D. M. Lambert*, G. K. E. Scriba, B. Gallez, J. H. Poupaert and P. Dumont Pages 376 - 391 ( 16 )
Drug-lipid conjugates have been prepared in order to confer the attached drugs to the metabolic pathways of natural lipids. The drug can be covalently bound either to a fatty acid or to a glyceride. In glycerides, one or two fatty acid moieties have been replaced by a drug realizing pseudoglycerides. These pseudoglycerides exhibited some physicochemi cal properties and absorption characteristics similar to those of natural triglycerides resulting in a different pharmacokinetic and/or pharmacodynamic profile compared that of the parent drug. Non-steroidal anti-inflammatory drugs such as aspirin, indomethacin, ibuprofen, naproxen and aclofenac were covalently bound to diglycerides in order to reduce the ulcerogenicity of the compounds. Employing the absorption process of dietary fat, pseudoglycerides have been used for the targeting of the lymphatic route in order to avoid the first-pass metabolism of a drug (L-DOPA) and I or to target the lymphatic system for the treatment of lymphatic metastasis (chlorambucil, melphalan) or filiariasis (melphalan and GABA). Pseudoglycerides and other glyceride-like structures have been evaluated in order to increase the intestinal absorption of poorly water-soluble drugs such as phenytoin. An improvement of the blood-brain barrier penetration of GABA covalently bound to glycerides has been reported in the 80's, A similar approach was followed for L-dopa, glycine, valproate, and the enkephalinase inhibitor thiorphan including amide bio-isosteres of glycerides. Radioiodinated agents containing fluoride and nitroxyl moieties were coupled to glycerides and fatty acids as potential hepatographic agents in nuclear medicine, 19F- and 1H-nuclear magnetic resonance imaging, respectively. A variety of phospholipid-linked cytotoxic nucleosides and nucleoside analogues such as ara-C, AZT and acyclovir have been prepared. Compared to the parent drugs the phospholipid analogs exhibited increased antineoplastic activity in vitro and in vivo. The conjugates were also active against tumors and viruses that were resistant against the drug itself.