Cyclosporine analogues

Cis-trans isomerization in cyclosporin C dissolved in acetonitrile

Cyclosporin is an 11-amino acid cyclic peptide with pharmacologically valuable properties which has a variety of actual and potential applications. Its activity relies on the cell membrane permeability which, in turn, depends on the structure of cyclosporin and its ability to change the conformation. In this work, conformational exchange processes occurring in cyclosporin C were studied using one- and two-dimensional nuclear magnetic resonance spectroscopy. The free energy barrier separating two major conformers observed in polar solution (acetonitrile) was found to be 77 ± 2 kJ/mol. Less populated conformation states are also present in the solution, which agrees with the ease of formation of multiple forms revealed by MD simulations of cyclosporin C.

Identification of isocyclosporins by collision-induced dissociation of doubly protonated species

Nonribosomal cyclopeptide cyclosporin A (CsA), produced by fungus Tolypocladium inflatum, is an extremely important immunosuppressive drug used in organ transplantations and for therapy of autoimmune diseases. Here we report for the first time production of CsA, along with related cyclosporins B and C, by Tolypocladium inflatum strains of marine origin (White Sea). Cyclosporins A-C contain an unusual amino acid, (4R)-4-((E)-2-butenyl)-4,N-dimethyl-l-threonine (MeBmt), and are prone to isomerization to non-active isocyclosporin by N→O acyl shift of valine connected to MeBmt in acidic conditions. CsA and isoCsA are not distinguishable in MS analysis of [M+H]⁺ ions due to rapid [CsA + H]⁺→[isoCsA + H]⁺ conversion. We found that the N→O acyl shift is completely suppressed in cyclosporine [M+2H]²⁺ ions, and their collision-induced dissociation (CID) can be used for rapid and unambiguous analysis of cyclosporins and isocylosporins. Fragmentation patterns of [CsA+2H]²⁺ and [isoCsA+2H]²⁺ ions were analyzed and explained. The developed approach could be useful for MS analysis of other peptides containing β-hydroxy-α-amino acids.

Drug repurposing screens reveal cell-type-specific entry pathways and FDA-approved drugs active against SARS-Cov-2

There is an urgent need for antivirals to treat the newly emerged severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). To identify new candidates, we screen a repurposing library of ∼3,000 drugs. Screening in Vero cells finds few antivirals, while screening in human Huh7.5 cells validates 23 diverse antiviral drugs. Extending our studies to lung epithelial cells, we find that there are major differences in drug sensitivity and entry pathways used by SARS-CoV-2 in these cells. Entry in lung epithelial Calu-3 cells is pH independent and requires TMPRSS2, while entry in Vero and Huh7.5 cells requires low pH and triggering by acid-dependent endosomal proteases. Moreover, we find nine drugs are antiviral in respiratory cells, seven of which have been used in humans, and three are US Food and Drug Administration (FDA) approved, including cyclosporine. We find that the antiviral activity of cyclosporine is targeting Cyclophilin rather than calcineurin, revealing essential host targets that have the potential for rapid clinical implementation.

Assessing the Impact of Cyclosporin A on Lentiviral Transduction and Preservation of Human Hematopoietic Stem Cells in Clinically Relevant Ex Vivo Gene Therapy Settings

Improving hematopoietic stem and progenitor cell (HSPC) permissiveness to lentiviral vector (LV) transduction without compromising their biological properties remains critical for broad-range implementation of gene therapy as a treatment option for several inherited diseases. This study demonstrates that the use of one-hit ex vivo LV transduction protocols based on either cyclosporin A (CsA) or rapamycin enable as efficient gene transfer as the current two-hit clinical standard into bone marrow-derived CD34⁺ cells while better preserving their engraftment capacity in vivo. CsA was additive with another enhancer of transduction, prostaglandin E2, suggesting that tailored enhancer combinations may be applied to overcome multiple blocks to transduction simultaneously in HSPC. Interestingly, besides enhancing LV transduction, CsA also significantly reduced HSPC proliferation, preserving the quiescent G₀ fraction and the more primitive multipotent progenitors, thereby yielding the highest engraftment levels in vivo. Importantly, no alterations in the vector integration profiles could be detected between CsA and control transduced HSPC. Overall, the present findings contribute to the development of more efficient and sustainable LV gene therapy protocols, underscoring the benefits of scaling down required vector doses, as well as shortening the HSPC ex vivo culture time.

Cyclosporine H Overcomes Innate Immune Restrictions to Improve Lentiviral Transduction and Gene Editing In Human Hematopoietic Stem Cells

Innate immune factors may restrict hematopoietic stem cell (HSC) genetic engineering and contribute to broad individual variability in gene therapy outcomes. Here, we show that HSCs harbor an early, constitutively active innate immune block to lentiviral transduction that can be efficiently overcome by cyclosporine H (CsH). CsH potently enhances gene transfer and editing in human long-term repopulating HSCs by inhibiting interferon-induced transmembrane protein 3 (IFITM3), which potently restricts VSV glycoprotein-mediated vector entry. Importantly, individual variability in endogenous IFITM3 levels correlated with permissiveness of HSCs to lentiviral transduction, suggesting that CsH treatment will be useful for improving ex vivo gene therapy and standardizing HSC transduction across patients. Overall, our work unravels the involvement of innate pathogen recognition molecules in immune blocks to gene correction in primary human HSCs and highlights how these roadblocks can be overcome to develop innovative cell and gene therapies.

Discovery of cyclosporine A and its analogs as broad-spectrum anti-influenza drugs with a high in vitro genetic barrier of drug resistance

As the number of drug-resistant influenza viruses continues to increase, antivirals with novel mechanisms of action are urgently needed. Among the two classes of FDA-approved antiviral drugs, neuraminidase (NA) inhibitors, oseltamivir, zanamivir, and peramivir, are currently the only choice for the prevention and treatment of influenza virus infection. Due to the antigenic drift and antigenic shift, it will only be a matter of time before influenza viruses become completely resistant to these NA inhibitors. In pursuing the next generation of antiviral drugs with complementary mechanisms of action to those of the NA inhibitors, we have identified a natural product, cyclosporine A (CsA) (1), as a desired drug candidate. In this study, we discovered that CsA (1) and its analogs have broad-spectrum antiviral activity against multiple influenza A and B strains, including strains that are resistant to either NA or M2 inhibitors or both. Moreover, CsA (1) displays a high in vitro genetic barrier of drug resistance than oseltamivir carboxylate Mechanistic studies revealed that CsA (1) acts at the intermediate step of viral replication post viral fusion. Its antiviral mechanism is independent of inhibiting the isomerase activity of cyclophilin A (CypA), and CsA (1) has no effect on the viral polymerase activity The potent antiviral efficacy of CsA (1), coupled with the high in vitro genetic barrier of drug resistance and novel mechanism of action, renders CsA (1) a promising anti-influenza drug candidate for further development.

Beyond cyclosporine A: conformation-dependent passive membrane permeabilities of cyclic peptide natural products

Many cyclic peptide natural products are larger and structurally more complex than conventional small molecule drugs. Although some molecules in this class are known to possess favorable pharmacokinetic properties, there have been few reports on the membrane permeabilities of cyclic peptide natural products. Here, we present the passive membrane permeabilities of 39 cyclic peptide natural products, and interpret the results using a computational permeability prediction algorithm based on their known or calculated 3D conformations. We found that the permeabilities of these compounds, measured in a parallel artificial membrane permeability assay, spanned a wide range and demonstrated the important influence of conformation on membrane permeability. These results will aid in the development of these compounds as a viable drug paradigm.

Cyclophilin inhibitors as a novel HCV therapy

A critical role of Cyclophilins, mostly Cyclophilin A (CyPA), in the replication of HCV is supported by a growing body of in vitro and in vivo evidence. CyPA probably interacts directly with nonstructural protein 5A to exert its effect, through its peptidyl-prolyl isomerase activity, on maintaining the proper structure and function of the HCV replicase. The major proline substrates are located in domain II of NS5A, centered around a “DY” dipeptide motif that regulates CyPA dependence and CsA resistance. Importantly, Cyclosporine A derivatives that lack immunosuppressive function efficiently block the CyPA-NS5A interaction and inhibit HCV in cell culture, an animal model, and human trials. Given the high genetic barrier to development of resistance and the distinctness of their mechanism from that of either the current standard of care or any specifically targeted antiviral therapy for HCV (STAT-C), CyP inhibitors hold promise as a novel class of anti-HCV therapy.

Peptidyl-prolyl isomerase inhibitors

Designed peptidyl-prolyl isomerase (PPIase) inhibitors of Pin1, cyclophilin (CyP), and FK506 binding protein (FKBP) are reviewed. Emphasis is placed on the design, structure, and biological activity of the inhibitors. While CyP and FKBP inhibitors have been explored fairly thoroughly, inhibitors of the relatively new Pin1 cell cycle regulator are in their infancy. Ligands designed for Pin1 and CyP have primarily been ground state analogues: alkenes and bicyclic compounds. For FKBP, more of the focus has been on analogues of bonds at the reactive center, the prolyl amide, because of the idea that the alpha-ketoamide of FK506 is an analogue of the twisted amide in the transition state.

Effects of low and high density lipoproteins on renal cyclosporine A and cyclosporine G disposition in the isolated perfused rat kidney

PURPOSE

This study investigated the effects of low (LDL) and high density lipoproteins (HDL) on renal cyclosporine A (CsA) and cyclosporine G (CsG) disposition in the isolated perfused rat kidney model.

METHODS

Kidneys were perfused with CsA or CsG in perfusion medium containing 6% protein, bovine serum albumin only (BSA) (Control), LDL (200 mg/dl) and BSA, or HDL (200 mg/dl) and BSA. In vitro protein binding studies were conducted with CsA and CsG in the same media.

RESULTS

The unbound fractions (fu) of CsA and CsG were significantly reduced with LDL and HDL in the perfusion media. In the presence of LDL, fu for CsA and CsG was 3.9% and 5.9%, respectively. With HDL, fu was 2.1% for CsA and 1.8% for CsG. fu for the controls was 14.7% for CsA and 11.9% for CsG. Renal clearance (CLR) of CsA and CsG was significantly reduced when perfused with perfusion medium containing LDL and HDL. LDL and HDL had similar effects on reducing CsA and CsG CLR, and were approximately four-fold lower when compared to controls (approximately 0.006 Vs. 0.023 ml/min). Renal CsA and CsG tissue (whole organ, cortex and medulla) concentrations were lower than corresponding controls when perfused with LDL or HDL.

CONCLUSIONS

The interaction of CsA and CsG with LDL and HDL significantly reduced the CLR and extent of renal tissue distribution of both compounds.

Metabolism of the new immunosuppressor cyclosporin G by human liver cytochromes P450

Cyclosporin G is a new immunosuppressor structurally similar to cyclosporin A. Although this drug is pharmacologically as active as cyclosporin A, it is less toxic, in particular at the kidney level. The aim of this work was to identify the enzyme system(s) involved in the oxidative metabolism of cyclosporin G in man: (1) in a bank of human liver microsomes (n = 22), cyclosporin G oxidase activity correlated significantly with cyclosporin A oxidase activity (P < 0.0001) and with the level of CYP3A4 (P < 0.002), determined by immunoblot; (2) specific inhibitors of CYP3A4, troleandomycin, and ketoconazole, inhibited cyclosporin G oxidase activity by more than 80%; (3) antiCYP3A4 antibodies specifically inhibited this activity by nearly 90%; (4) cyclosporin A was a competitive inhibitor of cyclosporin G oxidase and vice versa; (5). Among a battery of cDNA-expressed CYPs, only CYP3A4 was able to generate detectable amounts of metabolites of cyclosporin G and cyclosporin A with a turnover number close to that calculated from experiments with liver microsomes; (6) in human hepatocytes in culture, pretreatment of cells with rifampicin and phenobarbital, 2 inducers of CYP3A4, produced a great increase in cyclosporin G oxidase activity, while beta-naphthoflavone, an inducer of CYP1As, did not. We conclude that CYP3A4 is the major enzyme involved in the oxidative metabolism of cyclosporin G in human liver.

Comparative evaluation of in vitro and in vivo immunosuppressive potential of cyclosporin G with cyclosporin A and FK-506

Cyclosporin G (CsG), a promising cyclosporin A (CsA) analogue, was examined and compared with two reference immunosuppressive drugs: CsA and FK-506, regarding their inhibitory effects on different lymphocyte activation pathways as well as on graft-versus-host reaction (GvHR) across differences at major or minor histocompatibility loci. The results showed that, at different concentrations, CsG efficiently inhibited proliferation induced by alloantigens (mixed lymphocyte culture), mitogens (concanavalin A, pokeweed mitogen) and the combination of phorbol myristate acetate + ionomycin, to the same extent as observed with CsA and FK-506. It was also shown that CsG exhibited the same strong inhibitory effects as the two other immunosuppressants upon stimulation triggered by viral (MLs-1a) or bacterial (staphylococcal enterotoxin B) superantigen. Determination of IL-2 activity in the supernatant of MLC also confirmed similar strong inhibitory effects, exerted by CsG compared to CsA and FK-506. In systemic and local GvHR across major or minor histocompatibility barriers, CsG as well as CsA and FK-506 presented an equivalent immunosuppressive potential. In conclusion, from various experiments involving different modes of activation, it was shown that CsG was as strongly immunosuppressive as CsA and FK-506.

Analysis of whole-blood cyclosporin G by liquid chromatography in renal transplant recipients

Cyclosporin G (CsG) is less nephrotoxic than Cyclosporin A (CsA) and is undergoing clinical trials for use as an immunosuppressive agent after renal transplantation. In this study, CsG was measured by a rapid high-performance liquid chromatography (HPLC) technique in blood samples (n = 107) received from renal transplant recipients. The HPLC assay proved to be analytically suitable in that it was sensitive, linear, and precise and had high recovery (102%). However, interference was observed from some potentially co-administered drugs such as calcitriol, ferrous sulfate, hydrazaline, and minoxidil. The HPLC assay for CsG correlated well with a FPIA (Abbott TDx), FPIA = 0.964 (HPLC) + 33.59, r = 0.9819, Sy/x = 36.66 for patients receiving a low dose of CsG (5 mg/kg/day) and a high dose (10 mg/kg/day). Furthermore, the HPLC technique was capable of measuring predictable CsG concentrations when the drug was tapered to lower doses at various stages of the 16 week clinical trial. The HPLC for CsG has the further advantage that the same system and mobile phase can be used to measure CsA while using CsC as the interval standard.

Experimental nephrotoxicity, hepatotoxicity and pharmacokinetics of cyclosporin G versus cyclosporin A

Cyclosporin G (CsG) is an analogue of cyclosporin A (CsA) with strong immunosuppressive activity. We compared these two drugs in a rat model in which salt depletion promotes irreversible renal interstitial fibrosis with renal dysfunction in animals given CsA for three weeks. When both drugs were given in the same dosage on a weight basis (15 mg/kg/day, subcutaneously), CsA blood levels were higher than CsG (3305 vs. 1824 ng/ml, P < 0.001). This could be explained by a higher CsG clearance (6.4 vs. 4.3 ml/min/kg in CsA, P < 0.0001) resulting in smaller CsG area under the curve. There was also lower renal and hepatic CsG tissue concentrations. CsA induced a dramatic decrease in GFR, 0.14 in CsA versus 0.67 ml/min/100 g in control, P < 0.001, and increased urinary excretion of N-acetyl beta-D-glucosaminidase (NAG), 21 in CsA versus 13 IU/gCr in control rats, P < 0.001. CsG-treated and control rats had similar GFR and urinary NAG. When CsA dosage was decreased to 7.5 mg/kg blood levels were similar to those found with CsG 15 mg/kg. CsA at this dose caused a reduced GFR (0.29 ml/min/100 g) and an increased urinary NAG (20 IU/gCr) (P < 0.01 vs. control for both). Both dosages of CsA induced considerable cortical and medullary injury (interstitial fibrosis and tubular atrophy), more severe than the histological damage found in CsG-treated rats. Neither drug promoted significant changes in liver function or histology.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro comparative study on nephrotoxicity of cyclosporine A, its metabolites M1, M17, M21, and its analogues cyclosporines C and D in suspensions of rabbit renal cortical cells

The potential nephrotoxicity of cyclosporine A (CsA), its three main metabolites: M1, M17 and M21, and its two analogues: cyclosporines C and D (CsC, CsD) was evaluated in vitro in suspensions of freshly isolated rabbit renal proximal tubular cells. This assessment involved the measure of enzyme release in the incubation media and the determination of Na+/K(+)-ATPase activity and glutathione content directly in the tubular cells. In vitro nephrotoxicity results of the six compounds tested could be respectively schematized as: CsA > CsD > CsC > M21 > M17, M1 It would be interesting to promote the study of promising CsC because of its low nephrotoxicity and its high immunosuppressive potency as previously reported.

New immunosuppressive agents for pediatric transplantation

Pediatric transplantation has always been challenging for transplant surgeons. Although the higher immunoreactivity and the faster metabolism showed by this unique population when compared with adults requires a heavy immunosuppressive regimen, the possibility of disrupting the delicate balance of correct psychophysical development calls for a regimen of more selective and less toxic immunosuppressive drugs. In the past decade several new drugs have been investigated and some of them appear to be very promising, although pleiotropic toxicities have not yet been eliminated. An appropriate pharmacokinetic approach and the evaluation of synergistic multi-drug combinations by rigorous mathematical models would lead to highly selective immunosuppressive regimens which may result in virtually no toxicity.

In vitro and in vivo comparative studies on immunosuppressive properties of cyclosporines A, C, D and metabolites M1, M17 and M21

Cyclosporine A (CsA) and its major metabolites: M1, M17 and M21 and two analogues: cyclosporines C (CsC) and D (CsD), were studied for their capacity to interfere with different in vitro activation pathways. Their inhibition potentials against the reaction of Graft-versus-Host (GvH) were also studied. The results showed: CsA, CsC and metabolite M17 were the most active compounds upon the inhibition of lymphocyte proliferation induced by different mitogens (ConA, PHA, PWM) and also on the proliferation of mixed lymphocyte cultures (MLC). The same results were observed concerning the direct activation by protein kinase C using a combined action of phorbol ester + calcium ionophore. In vivo using local GvH reaction, CsA and CsC proved more active than M17 in the two different combinations: H-2d --> (H-2b x H-2d)F1 and H-2k --> (H-2b x H-2k)F1 CsD and two metabolites M1 and M21 showed no or weak immunosuppressive effects. Overall, the immunosuppressive potency of six compounds could be schematized as: CsA > or = CsC > M17 > M1 > or = CsD > M21.

Effect of cyclosporin A and its metabolites and analogs on lipid peroxidation in rabbit renal microsomes

Rabbit renal microsomes were used to investigate the effect on lipid peroxidation (LPO) of cyclosporin A (CsA) and its first generation metabolites M1, M17 and M21, and of two natural CsA analogs: cyclosporins C and D (CsC & CsD respectively), at concentrations of 1 to 10 micrograms/ml. No induction of lipid peroxidation was observed with these substances except CsA at a high level (10 microgram/ml); but at a concentration of CsA that would be reached in vivo, no inductive effect on LPO was noted. A moderate inhibitory effect upon LPO was observed with CsC and M21, but its biological significance is questionable.

Comparative study of effects of cyclosporins A and G on collagen arthritis in mice

The effects of the immunosuppressive agents cyclosporin G (CsG) and cyclosporin A (CsA) on collagen arthritis were compared in mice. When administered subcutaneously daily on days 0-13 after immunization with type II collagen, CsG and CsA were both capable of suppressing the development of collagen arthritis in mice as well as the immunological response to native type II collagen in a dose-dependent manner. Histopathologically, no marked inflammatory lesions were observed in diarthroidal joints from mice treated with 100 mg/kg per day of CsA or 800 mg/kg per day of CsG. However, an analysis of dose response showed CsG to be 8 times less potent than CsA in inhibiting the development of arthritis.