Cyclosporin A-Derivative 2

Valspodar (PSC-833) is a derivative of cyclosporin but devoid of the immunosuppressive and nephrotoxic properties seen in cyclosporin A. It exhibited high affinity binding to Mdr1 P-glycoprotein (P-gp) and demonstrated multidrug resistance-reversing activity superior to cyclosporin A and verapamil both in vitro and in vivo. Preclinical and phase I/II clinical data have indicated that plasma levels of PSC-833 with multidrug resistance-reversing activities are achievable. Potent inhibition of intestinal, hepatobiliary and blood-brain barrier P-gp function has been demonstrated. Since valspodar is also a substrate of cytochrome P450 3A (CYP3A), dual interactions of this compound with P-gp and CYP3A are the basis for the pharmacokinetic interactions seen in preclinical and clinical studies. A new formulation of the drug has recently been developed with better oral bioavailability (60%) and less interindividual variability. The toxicity profiles of valspodar are acceptable and dose-limited by transient and reversible cerebellar ataxia. It has shown multidrug resistance-modulating activities towards acute myeloid leukemia, multiple myeloma and ovarian cancer in phase I/II clinical trials. Phase III studies with respect to these three diseases are ongoing.

HCV infection is the primary cause of chronic liver disease. Host cell cyclophilins (Cyps) are essential for efficient HCV replication in hepatocytes, and thus Cyps are regarded as a new target for anti-HCV therapy. Alisporivir (Debio-025), a non-immunosuppressive cyclosporine A derivative that selectively inhibits Cyps, is being developed by Debiopharm SA for the potential oral treatment of HCV infection. In the HCV subgenomic replicon system, alisporivir suppressed viral replication more potently than cyclosporine A. A phase II clinical trial demonstrated that treatment with alisporivir alone or combined with PEGylated IFNalpha2a reduced the viral load in patients with chronic HCV infection. The drug was also generally well tolerated. In contrast, a phase I trial of alisporivir monotherapy in patients with HIV-1 infection suggested that the drug has a limited effect on HIV-1 viral load. Alisporivir was also investigated in animal models of muscular dystrophy, acute myocardial infarction and brain disorders. At the time of publication, two phase II trials, evaluating alisporivir alone and in combination with PEGylated IFNalpha2a or with PEGylated IFNalpha2a and ribavirin, were ongoing in treatment-naïve patients with HCV-1 infection and in patients with chronic HCV-1 infection who were prior non-responders to PEGylated IFNalpha or ribavirin.

Key points: ·Bile acids, ethanol and fatty acids affect pancreatic ductal fluid and bicarbonate secretion via mitochondrial damage, ATP depletion and calcium overload. ·Pancreatitis-inducing factors open the membrane transition pore (mPTP) channel via cyclophilin D activation in acinar cells, causing calcium overload and cell death; genetic or pharmacological inhibition of mPTP improves the outcome of acute pancreatitis in animal models. ·Here we show that genetic and pharmacological inhibition of mPTP protects mitochondrial homeostasis and cell function evoked by pancreatitis-inducing factors in pancreatic ductal cells. ·The results also show that the novel cyclosporin A derivative NIM811 protects mitochondrial function in acinar and ductal cells, and it preserves bicarbonate transport mechanisms in pancreatic ductal cells. ·We found that NIM811 is highly effective in different experimental pancreatitis models and has no side-effects. NIM811 is a highly suitable compound to be tested in clinical trials. Abstract: Mitochondrial dysfunction plays a crucial role in the development of acute pancreatitis (AP); however, no compound is currently available with clinically acceptable effectiveness and safety. In this study, we investigated the effects of a novel mitochondrial transition pore inhibitor, N-methyl-4-isoleucine cyclosporin (NIM811), in AP. Pancreatic ductal and acinar cells were isolated by enzymatic digestion from Bl/6 mice. In vitro measurements were performed by confocal microscopy and microfluorometry. Preventative effects of pharmacological [cylosporin A (2 µm), NIM811 (2 µm)] or genetic (Ppif-/- /Cyp D KO) inhibition of the mitochondrial transition pore (mPTP) during the administration of either bile acids (BA) or ethanol + fatty acids (EtOH+FA) were examined. Toxicity of mPTP inhibition was investigated by detecting apoptosis and necrosis. In vivo effects of the most promising compound, NIM811 (5 or 10 mg kg-1 per os), were checked in three different AP models induced by either caerulein (10 × 50 µg kg-1 ), EtOH+FA (1.75 g kg-1 ethanol and 750 mg kg-1 palmitic acid) or 4% taurocholic acid (2 ml kg-1 ). Both genetic and pharmacological inhibition of Cyp D significantly prevented the toxic effects of BA and EtOH+FA by restoring mitochondrial membrane potential (Δψ) and preventing the loss of mitochondrial mass. In vivo experiments revealed that per os administration of NIM811 has a protective effect in AP by reducing oedema, necrosis, leukocyte infiltration and serum amylase level in AP models. Administration of NIM811 had no toxic effects. The novel mitochondrial transition pore inhibitor NIM811 thus seems to be an exceptionally good candidate compound for clinical trials in AP.