User:Mpagan2/Sandbox

Mechanism of action
The mechanism of thalidomide's teratogenic action has led to over 2000 research papers and the proposal of 15 or 16 plausible mechanisms. Angiogenesis is critical during limb development of the foetus. In 1998, it was found in vivo that during limb development thalidomide was able to inhibit the stimulatory effects of growth factors FGF-2 and IGF-1 that promote angiogenesis. Surface integrin αVβ3 is notably important in this process. Previous work showed thalidomide's ability to decrease integrin production on the cell surface, decreasing the cell's ability to stimulate new blood vessels, and inhibit angiogenesis stimulated by FGF-2. It was soon found that αVβ3 had several GC box sequences in its promoter region and the same was true for FGF-2 and IGF-1 and their receptors on the cell surface. Further investigation into this phenomenon found that at least eight other proteins in the growth-stimulating cascade too had promotors containing this region. Thalidomide has a high affinity for guanine, thus it was hypothesized that thalidomide intercalates into these GC boxes and prevents integrins from stimulating new blood vessels that support limb development, thereby exerting the tetratogenic effects seen in thalidomide-induced birth defects.

In 2009, research by other groups confirmed "conclusively that loss of newly formed blood vessels is the primary cause of thalidomide teratogenesis, and developing limbs are particularly susceptible because of their relatively immature, highly angiogenic vessel network".

TNF-α
Tumor necrosis factor alpha (TNF-α) is a cytokine that is chiefly involved in regulating white blood cells. Changes in the regulation of this protein has been found to be related to various diseases such as Alzheimer's disease and cancer.

In 1990, a group of researchers in Brazil noted that TNF-α levels went up in leprosy reactional states and observed that TNF levels decreased in some patients on treatment with thalidomide, hence potentially explaining the efficacy of thalidomide in treating ENL.

In light of this, further study of how this drug affected TNF-α were conducted. In 1993, thalidomide was found to selectively degrade TNF-α mRNA, however how it does so is unclear. This is compared to other known TFN-α inhibitors, some of which have been found to block transcription of the TNF-α gene, TNFA, or block translation of the mRNA. Further, this reduction in TNF-α lead to a decrease in inflammatory cytokine levels, suggesting thalidomide's use in treating other inflammatory infections.

Thalidomide analogs have been found to have even more profound effects on TNF-α inhibition than their parent molecule. Replacing thalidomide's carbonyls with thiones increased its ability to inhibit TNF-α in the following order:

trithiothalidomide > dithiothalidomide > monothiothalidomide > thalidomide

as seen in the structures to the right. It is hypothesized that this these analogs act on the 3'-UTR of TNFA to exert their effects.

Synthesis
Thalidomide is synthesized into a racemic mixture, however separating the mixture into a enatiomerically pure solution would prove fruitless as the racemization can occur in vivo. Celgene Corporation originally synthesized thalidomide using a three-step sequence starting with L-glutamic acid treatment, but this has since been reformed by the use of L-glutamine. As shown in the image below, N-carbethoxyphtalimide (1) can react with L-glutamine to yield N-Phthaloyl-L-glutamine (2). Cyclization of N-Phthaloyl-L-glutamine occurs using carbonyldiimidazole, which then yields thalidomide (3). Celegne Corporation's original method resulted in a 31% yield of S-thalidomide, whereas the two-step synthesis yields 85-93% product that is 99% pure.



Mechanism of action
The precise mechanism of action for thalidomide is unknown, but possible mechanisms include anti-angiogenic and oxidative stress-inducing effects. It also inhibits TNF-α, IL-6, IL-10 and IL-12 production, modulates the production of IFN-γ and enhances the production of IL-2, IL-4 and IL-5 by immune cells. It increases lymphocyte count, costimulates T cells and modulates natural killer cell cytotoxicity. It also inhibits NF-κB and COX-2 activity.

The mechanism of thalidomide's teratogenic action has led to over 2000 research papers and the proposal of 15 or 16 plausible mechanisms. Angiogenesis is critical during limb development of the foetus. In 1998, it was found in vivo that during limb development thalidomide was able to inhibit the stimulatory effects of growth factors FGF-2 and IGF-1 that promote angiogenesis. Surface integrin αVβ3 is notably important in this process. Previous work showed thalidomide's ability to decrease integrin production on the cell surface, decreasing the cell's ability to stimulate new blood vessels, and inhibit angiogenesis stimulated by FGF-2. It was soon found that αVβ3 had several GC box sequences in its promoter region and the same was true for FGF-2 and IGF-1 and their receptors on the cell surface. Further investigation into this phenomenon found that at least eight other proteins in the growth-stimulating cascade too had promotors containing this region. Thalidomide has a high affinity for guanine, thus it was hypothesized that thalidomide intercalates into these GC boxes and prevents integrins from stimulating new blood vessels that support limb development, thereby exerting the tetratogenic effects seen in thalidomide-induced birth defects.

In 2009, research by other groups confirmed "conclusively that loss of newly formed blood vessels is the primary cause of thalidomide teratogenesis, and developing limbs are particularly susceptible because of their relatively immature, highly angiogenic vessel network".

Thalidomide is racemic; the individual enantiomers can racemize due to the acidic hydrogen at the chiral centre, which is the carbon of the glutarimide ring bonded to the phthalimide substituent. The racemization process can occur in vivo  so that any plan to administer a purified single enantiomer to avoid the teratogenic effects will most likely be in vain.

TNF-α
Tumor necrosis factor alpha (TNF-α) is a cytokine that is chiefly involved in regulating white blood cells. Changes in the regulation of this protein has been found to be related to various diseases such as Alzheimer's disease and cancer. .

In 1990, a group of researchers in Brazil noted that TNF-α levels went up in leprosy reactional states and observed that TNF levels decreased in some patients on treatment with thalidomide, hence potentially explaining the efficacy of thalidomide in treating ENL.

In light of this, further study of how this drug affected TNF-α were conducted. In 1993, thalidomide was found to selectively degrade TNF-α mRNA, however how it does so is unclear. This is compared to other known TFN-α inhibitors, some of which have been found to block transcription of the TNF-α gene, TNFA, or block translation of the mRNA. Further, this reduction in TNF-α lead to a decrease in inflammatory cytokine levels, suggesting thalidomide's use in treating other inflammatory infections.

Thalidomide analogs have been found to have even more profound effects on TNF-α inhibition than their parent molecule. Replacing thalidomide's carbonyls with thiones increased its ability to inhibit TNF-α in the following order:

trithiothalidomide > dithiothalidomide > monothiothalidomide > thalidomide

as seen in the structures to the right. It is hypothesized that this these analogs act on the 3'-UTR of TNFA to exert their effects.

Cereblon
Several studies have shown that the mechanism of action for thalidomide involves binding to the protein cereblon, a ubiquitin ligase substrate adapter protein, which is important in limb formation and the proliferative capacity of myeloma cells. Ubiquitin ligases function by reducing the cellular levels of proteins and thalidomide has been shown to alter the set of proteins which CRBN can degrade. Cereblon's relevance to human congenital defects was confirmed in studies that reduced the production of cereblon in developing chick and zebrafish embryos using genetic techniques. These embryos had defects similar to those treated with thalidomide. Interestingly, mice treated with thalidomide do not display teratogenicity of their offspring as seen in humans.

Other actions
Thalidomide binds to and acts as an antagonist of the androgen receptor (AR). In accordance, it can produce gynecomastia and sexual dysfunction as side effects in men. DIMP is a non-steroidal antiandrogen which was one of the first antiandrogens to be developed, and is structurally related to thalidomide.

Synthesis
Thalidomide is synthesized into a racemic mixture, however separating the mixture into a enatiomerically pure solution would prove fruitless as the racemization can occur in vivo. Celgene Corporation originally synthesized thalidomide using a three-step sequence starting with L-glutamic acid treatment, but this has since been reformed by the use of L-glutamine. As shown in the image below, N-carbethoxyphtalimide (1) can react with L-glutamine to yield N-Phthaloyl-L-glutamine (2). Cyclization of N-Phthaloyl-L-glutamine occurs using carbonyldiimidazole, which then yields thalidomide (3). Celegne Corporation's original method resulted in a 31% yield of S-thalidomide, whereas the two-step synthesis yields 85-93% product that is 99% pure.