A Monoselective Sphingosine-1-Phosphate Receptor-1 Agonist Prevents Allograft Rejection in a Stringent Rat Heart Transplantation Model

SummaryFTY720 is an immunomodulator with demonstrated efficacy in a phase II trial of relapsing multiple sclerosis. FTY720-phosphate, the active metabolite generated upon phosphorylation in vivo, acts as a potent agonist on four of the five known sphingosine-1-phosphate (S1P1) receptors. AUY954, an aminocarboxylate analog of FTY720, is a low nanomolar, monoselective agonist of the S1P1 receptor. Due to its selectivity and pharmacokinetic profile, AUY954 is an excellent pharmacological probe of S1P1-dependent phenomena. Oral administration of AUY954 induces a profound and reversible reduction of circulating lymphocytes and, in combination with RAD001 (Certican/Everolimus, an mTOR inhibitor), is capable of prolonging the survival of cardiac allografts in a stringent rat transplantation model. This demonstrates that a selective agonist of the S1P1 receptor is sufficient to achieve efficacy in an animal model of transplantation

Macrophage infiltration detected at MR imaging in rat kidney allografts: early marker of chronic rejection?

PURPOSE: To evaluate detection of iron-loaded macrophages at magnetic resonance (MR) imaging as a noninvasive means to monitor early signs of chronic allograft rejection in the life-supporting Fisher-to-Lewis rat kidney transplantation model. MATERIALS AND METHODS: Experiments followed the Swiss federal regulations of animal protection. Male Fisher (n = 37) and Lewis (n = 77) rats were used. After removal of a native recipient kidney and transplantation of a donor kidney, the recipient rat's contralateral kidney was removed. Allografts and control syngeneic grafts comprised, respectively, kidneys from Fisher and Lewis donors transplanted into Lewis rats. Recipients were imaged by using a gradient-echo MR sequence 24 hours after intravenous administration of superparamagnetic iron oxide (SPIO) particles. Biochemical analyses of blood and urine, as well as assessments of Banff scores (reference standard for histologic classification of graft rejection), were performed. Statistical tests used were analysis of variance for multiple comparisons with Bonferroni tests, Mann-Whitney tests, and Pearson correlations with Bonferroni corrections. RESULTS: A SPIO dose-dependent decrease in cortical MR signal intensity occurred in allografts between 8 and 16 weeks after transplantation. A strong significant negative correlation (P = .005 for 0.3 mL/kg SPIO dose, P = .003 for 1.0 mL/kg SPIO dose) was found between MR signal intensity and Banff scores, which deteriorated over the experimental period. Proteinuria occurred at 16 weeks. Blood and urine creatinine levels remained unchanged up to week 28. CONCLUSION: This MR imaging method is more robust than the usually adopted creatinine clearance method for the detection of early signs of allograft chronic rejection in the Fisher-to-Lewis rat kidney transplantation model

An oral S1P1 antagonist prodrug with efficacy in vivo: discovery, synthesis and evaluation

A prodrug approach to optimize the oral exposure of an S1P1 antagonist for chronic efficacy studies led to the discovery of (S)-2-{[3'-(4-Chloro-2,5-dimethyl-benzenesulfonylamino)-3,5-dimethyl-biphenyl-4-carbonyl]-methyl-amino}-4-dimethylamino-butyric acid methyl ester (BVM924). Due to the steric hindrance and the partial double bond character of the amide group and the resulting large rotational barrier around the amide bond two conformers of (BVM924) can be detected in solution and their equilibration was investigated by UPLC and 1H NMR. Methyl ester prodrug (BVM924) is hydrolyzed in vivo to the corresponding carboxylic acid (BVS819), a potent and selective S1P1 antagonist. Oral administration of the prodrug (BVM924) induces sustained peripheral lymphocyte depletion in rats. In a rat cardiac transplantation model co-administration of a nonefficacious dose of prodrug (BVM924) with a nonefficacious dose of sotrastaurin (AEB071), a protein kinase C inhibitor, or everolimus (RAD001), an mTOR inhibitor, effectively prolonged the survival time of rat cardiac allografts. This demonstrates that clinically useful immunomodulation mediated by the S1P1 receptor can be achieved with an S1P1 antagonist generated in vivo after oral administration of its prodrug

Evaluation of biomarker discovery approaches to detect protein biomarkers of acute renal allograft rejection.

Management of host responses to allografts by immunosuppressive therapy is the cornerstone of transplantation medicine, but it is still deficient in one important element: biomarkers that are readily accessible and predict the fate of the transplant early, specifically, and reliably. Using a Brown Norway (BN)-to-Lewis rat renal allograft model of kidney transplantation, this study aims at evaluating two proteomic approaches to discover biomarkers for acute rejection: SELDI-MS technology and 2D gel electrophoresis combined with mass spectrometry. Several novel potential serum biomarkers have been identified for follow up. Overall, the conclusion is that apparently at the serum protein level, dramatic changes only occur at a stage where kidney function is already severely affected. Multivariate analysis of serum profiles suggests that there is an ensemble of subtle changes, comprising a proteomic signature of acute rejection at an early stage, a more detailed evaluation of which might provide novel opportunities for the diagnosis of acute rejection. Profiling of the excreted proteins indicates that urine might even present the earliest signs of the rejection process

An Oral Sphingosine 1‑Phosphate Receptor 1 (S1P₁) Antagonist Prodrug with Efficacy in Vivo: Discovery, Synthesis, and Evaluation

A prodrug approach to optimize the oral exposure of a series of sphingosine 1-phosphate receptor 1 (S1P₁) antagonists for chronic efficacy studies led to the discovery of (<i>S</i>)-2-{[3′-(4-chloro-2,5-dimethylphenylsulfonylamino)-3,5-dimethylbiphenyl-4-carbonyl]­methylamino}-4-dimethylaminobutyric acid methyl ester <b>14</b>. Methyl ester prodrug <b>14</b> is hydrolyzed in vivo to the corresponding carboxylic acid <b>15</b>, a potent and selective S1P₁ antagonist. Oral administration of the prodrug <b>14</b> induces sustained peripheral blood lymphocyte reduction in rats. In a rat cardiac transplantation model coadministration of a nonefficacious dose of prodrug <b>14</b> with a nonefficacious dose of sotrastaurin (<b>19</b>), a protein kinase C inhibitor, or everolimus (<b>20</b>), an mTOR inhibitor, effectively prolonged the survival time of rat cardiac allografts. This demonstrates that clinically useful immunomodulation mediated by the S1P₁ receptor can be achieved with an S1P₁ antagonist generated in vivo after oral administration of its prodrug