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LFA-1 (leukocyte function-associated antigen-1), is a member of the beta2-integrin family and is expressed on all leukocytes. This letter describes the discovery and preliminary SAR of spirocyclic hydantoin based LFA-1 antagonists that culminated in the identification of analog 8 as a clinical candidate. We also report the first example of the efficacy of a small molecule LFA-1 antagonist in combination with CTLA-4Ig in an animal model of transplant rejection.

Angiogenesis, the process of blood vessel formation from pre-formed vessels, has recently become a primary target of anticancer therapy. This is due in part to the finding that removing the blood supply to a tumor can not only prevent further growth but can also starve the existing cells to death.2) In the past several years there have been many potential anti-angiogenic agents developed acting by many mechanisms including interruption of growth factor receptor phosphorylation, [3][4][5] growth factor-receptor binding, 6,7) cell adhesion molecule expression and signaling 8,9) and alterations in endothelial cell apoptosis. 10,11) In addition, several agents such as thalidomide have been shown to inhibit angiogenesis by an as yet not fully understood mechanism.12-18) Furthermore, thalidomide has been shown to reduce tumor growth both in model systems [19][20][21] and in patients. [22][23][24][25][26][27][28] Clinically, however, thalidomide has a fairly weak effect as a monotherapy in patients with solid tumors [22][23][24] but is showing tremendous promise against multiple myeloma.25-28) It has been shown that activation of thalidomide by human or rabbit liver enzymes, but not by rat liver enzymes, significantly enhances the anti-angiogenic effect of the drug in rat aortic sections or isolated endothelial cells.29) This is very interesting because thalidomide is virtually non-toxic to rats when given orally (PO). Intraperitoneal (IP), administration however, commonly associated with "first-pass" hepatic metabolism, 30) recapitulates the teratogenic effect of thalidomide in rats. 31)Kenyon et al. 19) also showed that thalidomide given IP was effective as an anti-angiogenic agent in the mouse corneal model, whereas thalidomide given PO was inactive. In addition, thalidomide teratogenesis was only found to occur after activation of the drug by liver enzymes. 13,[32][33][34][35] Furthermore, in a Xenopus oocyte assay of teratogenesis, activation of thalidomide by a single cytochrome P450 enzyme, CYP2E1, lead to a teratogenic compound whereas unactivated thalidomide was non-teratogenic.35) Thus metabolism of thalidomide is critical to its anti-angiogenic and teratogenic activity. However, the identity of the active anti-angiogenic and teratogenic moiety or moieties of thalidomide are still unknown.The goal of this work was to explore the effect of putative hydroxylated thalidomide metabolites on blood vessel density and target cell proliferation. Since the anti-angiogenic activity of thalidomide was first reported, 36) only a limited number of thalidomide metabolites have been tested for antiangiogenic activity. Figure 1 shows known and hypothesized metabolites of thalidomide (structures M1-M8) based on extensive literature review. [37][38][39][40][41][42][43][44][45] Thalidomide can be metabolized through hydrolysis at the glutarimide and/or phthalimide ring to yield metabolites such as M6-M8. Its hydroxylation can occur on glutarimide or phthalimide ring to yield metabolites M1-M5. Interestingly, only metabolites M5...

Inosine monophosphate dehydrogenase (IMPDH), a key enzyme in the de novo synthesis of guanosine nucleotides, catalyzes the irreversible nicotinamide-adenine dinucleotide dependent oxidation of inosine-5'-monophosphate to xanthosine-5'-monophosphate. Mycophenolate Mofetil (MMF), a prodrug of mycophenolic acid, has clinical utility for the treatment of transplant rejection based on its inhibition of IMPDH. The overall clinical benefit of MMF is limited by what is generally believed to be compound-based, dose-limiting gastrointestinal (GI) toxicity that is related to its specific pharmacokinetic characteristics. Thus, development of an IMPDH inhibitor with a novel structure and a different pharmacokinetic profile may reduce the likelihood of GI toxicity and allow for increased efficacy. This article will detail the discovery and SAR leading to a novel and potent acridone-based IMPDH inhibitor 4m and its efficacy and GI tolerability when administered orally in a rat adjuvant arthritis model.

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