Thalidomide-based TNF-alpha inhibitors for neurodegenerative diseases.

Inflammatory processes associated with the over-production of cytokines, particularly of TNF-alpha, accompany numerous neurodegenerative diseases, such as Alzheimer's disease, in addition to numerous systemic conditions, exemplified by rheumatoid arthritis and erythema nodosum leprosum (ENL). TNF-alpha has been validated as a drug target with Remicade and Enbrel available as prescription medications. Both, however, are large macromolecules, require injection and have limited brain access. The classical drug, thalidomide is being increasingly used in the clinical management of a wide spectrum of diseases. As its clinical value in treating ENL derives from its TNF-alpha inhibitory activity, thalidomide was chosen for structural modification for the discovery of novel and more potent isosteric analogues with appropriate lipophilicity to insure high brain penetration. TNF-alpha inhibitory activity was evaluated against lipopolysacharide (LPS) stimulated peripheral blood mononuclear cells (PBMC) in cell culture, whose viability was quantified to differentiate reductions in TNF-alpha secretion from that associated with cellular toxicity. Specific analogues potently inhibited TNF-alpha secretion, compared to thalidomide. This involved a post-transcriptional mechanism, as they decreased TNF-alpha mRNA stability via its 3'-untranslated region (UTR), as determined by luciferase activity in stably transfected cells with and without the 3'-UTR of human TNF-alpha.

Thiothalidomides: novel isosteric analogues of thalidomide with enhanced TNF-alpha inhibitory activity.

Thalidomide is being increasingly used in the clinical management of a wide spectrum of immunologically-mediated and infectious diseases, and cancers. However, the mechanisms underlying its pharmacological action are still under investigation. In this regard, oral thalidomide is clinically valuable in the treatment of erythema nodosum leprosum (ENL) and multiple myeloma and effectively reduces tumor necrosis factor-alpha (TNF-alpha) levels and angiogenesis in vivo. This contrasts with its relatively weak effects on TNF-alpha and angiogenesis in in vitro studies and implies that active metabolites contribute to its in vivo pharmacologic action and that specific analogues would be endowed with potent activity. Our focus in the structural modification of thalidomide is toward the discovery of novel isosteric active analogues. In this regard, a series of thiothalidomides and analogues were synthesized and evaluated for their TNF-alpha inhibitory activity against lipopolysacharide (LPS)-stimulated peripheral blood mononuclear cells (PBMC), This was combined with a PBMC viability assay to differentiate reductions in TNF-alpha secretion from cellular toxicity. Two isosteric analogues of thalidomide, compounds 15 and 16, that mostly reflect the parent compound, together with the simple structure, dithioglutarimide 19, potently inhibited TNF-alpha secretion, compared to thalidomide, 1. The mechanism underpinning this most likely is posttranscriptional, as each of these compounds decreased TNF-alpha mRNA stability via its 3'-UTR. The potency of 19 warrants further study and suggests that replacement of the amide carbonyl with a thiocarbonyl may be beneficial for increased TNF-alpha inhibitory action. In addition, an intact phthalimido moiety appeared to be requisite for TNF-alpha inhibitory activity.