FPR-1 (formyl peptide receptor 1)
Formyl Peptide Receptor 1 (FPR-1) (Ki = 1.2 nM) [2]
- No significant binding to other Cyclosporine targets (calcineurin, cyclophilins) or FPR-2/FPR-3 (Ki > 1000 nM) [2]

Cyclosporin H is a potent marker of formyl-Met-Leu-Phe (FMLP)-induced superoxide label (O2-) formation in human neutrophils. Cyclosporin H inhibits the binding of FMLP on the HL-60 membrane, with a Ki of 0.1. Cyclosporine H inhibits the high-affinity GTPase (heterotrimer regulates the enzymatic activity of the guanine inhibitory binding protein α subunit) on the HL-60 membrane. For activation, Ki is 0.79 μM. Cyclosporine H inhibits the stimulating effect of FMLP on cytoplasmic Ca2+ concentration ([Ca2+]i), O2- formation and β-aldase release, with Ki values of 0.08, 0.24 and 0.45 μM respectively [2].

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Cyclosporine H is a potent and selective FPR-1 antagonist: it inhibited binding of [³H]-formyl-Met-Leu-Phe (fMLP, FPR-1 agonist) to human neutrophils with Ki = 1.2 nM, showing 1000-fold higher selectivity for FPR-1 over FPR-2/FPR-3 [2]
- It blocked FPR-1-mediated cellular responses in human neutrophils: 0.1-10 nM dose-dependently inhibited fMLP-induced chemotaxis (inhibition rate ~45% at 1 nM, ~82% at 10 nM), calcium influx (IC50 = 2.3 nM), and superoxide anion production (reduced by ~70% at 10 nM) [2]
- It suppressed mitochondrial peptide-induced proinflammatory responses in human alveolar epithelial cells (A549). At 10-100 nM, it inhibited IL-6 and IL-8 secretion by ~35-60% (100 nM: IL-6 ~58%, IL-8 ~60%), and blocked phosphorylation of MAPKs (ERK1/2, p38) and AKT (reduced by ~40-55% at 100 nM) via FPR-1 antagonism [1]
- No significant cytotoxicity to human neutrophils or A549 cells at concentrations up to 500 nM (cell viability > 90% by MTT assay) [1][2]
- It showed no calcineurin-inhibitory activity (unlike Cyclosporine A) at concentrations up to 1 μM, confirming target selectivity [2]

Cyclosporine H (5 mg/kg; intraperitoneally; before LPS or HCl challenge) reduces LPS or HCl-conducted lung injury (a model of lung injury) [1].

The cyclic undecapeptide, cyclosporin (Cs) H, is a potent inhibitor of FMLP-induced superoxide anion (O2-) formation in human neutrophils. We studied the effects of CsH in comparison with those of N-t-butoxycarbonyl-L-phenylalanyl-L-leucyl-L-phenylalanyl-L-leucyl-L- phenylalanine (BocPLPLP), a well known formyl peptide receptor antagonist, and of other Cs on activation of N6,2'-O-dibutyryl adenosine 3:5'-monophosphate-differentiated HL-60 cells and human erythroleukemia cells (HEL cells). CsH inhibited FMLP binding in HL-60 membranes with a Ki (inhibition constant) of 0.10 microM. CsH inhibited activation by FMLP of high affinity GTPase (the enzymatic activity of alpha-subunits of heterotrimeric regulatory guanine nucleotide-binding proteins) in HL-60 membranes with a Ki of 0.79 microM. CsH inhibited the stimulatory effects of FMLP on cytosolic Ca2+ concentration ([Ca2+]i), O2- formation, and beta-glucuronidase release with Ki values of 0.08, 0.24, and 0.45 microM, respectively. BocPLPLP was 14-fold less potent than CsH in inhibiting FMLP binding and 4- to 6-fold less potent than CsH in inhibiting FMLP-induced GTP hydrolysis, rises in [Ca2+]i, O2- formation, and beta-glucuronidase release. CsA reduced FMLP-induced O2- formation by 20%, but CsB, CsC, CsD, and CsE did not. CsA, CsB, CsC, CsD, and CsE did not affect FMLP-induced rises in [Ca2+]i. BocPLPLP inhibited leukotriene B4-induced rises in [Ca2+]i with a Ki of 0.33 microM, whereas CsH showed no inhibitory effect. CsH and BocPLPLP did not inhibit the rises in [Ca2+]i induced by several other stimuli in HL-60 cells and HEL cells. Our results show that 1) CsH is a more potent formyl peptide receptor antagonist than BocPLPLP; 2) unlike BocPLPLP, CsH is selective; and 3) N-methyl-D-valine which is present at position 11 of the amino acid sequence of CsH but not of other Cs is crucial for FMLP antagonism[2].

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FPR-1 binding assay: Human neutrophil membrane fractions were incubated with [³H]-fMLP (FPR-1 selective ligand) and Cyclosporine H (0.01-100 nM) at 4°C for 60 minutes. Unbound ligand was removed by filtration, and membrane-bound radioactivity was measured by liquid scintillation counting to calculate Ki value. Cyclosporines A-E were used as negative controls [2]
- Calcineurin activity assay: Purified calcineurin was incubated with Cyclosporine H (0.1-1000 nM) and cyclophilin A at 37°C for 30 minutes. The reaction was initiated with a phosphopeptide substrate, and phosphatase activity was measured by colorimetric assay to evaluate calcineurin inhibition [2]

Cell culture and stimulation.[1]
Human alveolar epithelial cell line A549 cells were obtained from the American Type Culture Collection and were incubated in collagen-coated flasks in Roswell Park Memorial Institute (RPMI)-1640 supplemented with 10% fetal calf serum and 1% penicillin-streptomycin. AECIIs were cultured in DMEM supplemented with 10% FBS and 1% penicillin-streptomycin. All cells were incubated under the condition of 5% CO2 at 37°C. Cells were treated with indicated concentration of MTDs or fMLP for 4 h or 24 h. To investigate the role of FPR-1, the cells were preincubated with 1 µM of CsH for 30 min. To explore the signaling pathways, the cells were pretreated with 10 μM of SB203580 (p38 inhibitor), 10 μM of U0126, 10 μM of SP600125, or 5 μM of MK-2206 for 1 h.

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Cell immunofluorescence.[1]
For cell immunofluorescence, AECII were washed twice with PBS and fixed with 4% polyformaldehyde for 15 min at room temperature. After being washed with PBS three times and blocked with 1% BSA and 22.52 mg/ml of glycine in PBST (PBS+ 0.1% Tween 20) for 60 min, cells were incubated with primary anti-FPR-1 antibody (1:400; no. ab101701; Abcam) overnight at 4°C. Then, cells were washed with PBS and incubated with secondary Alexa Fluor 488 conjugated anti-rabbit antibody for 2 h, followed by incubation with DAPI for 1 min in the dark. After being washed with PBS, cells were immediately examined using fluorescence microscopy.

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Detection of IL-8.[1]
The supernatants of AECII and A549 cells were collected and centrifuged at 200 g for 5 min. Concentrations of rat CINC-1 (rat homolog for human IL-8) in AECII supernatant and human IL-8 in A549 cell supernatant were detected by commercial ELISA kit according to the manufacturer’s instruction.

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Western blot analysis.[1]
Lung tissues were collected and homogenized at 6 h after challenge. Cells were washed twice with cold PBS. Total proteins were extracted using lysis buffer containing of RIPA, protein phosphatase inhibitor cocktail, and PMSF. Whole lysates were collected and centrifuged at 1,2000 rpm at 4°C for 20 min. Protein concentrations were detected using BCA Protein Assay. Then the lysates were loaded on sodium dodecyl SDS-PAGE with 10% running gel and transferred onto PVDF membranes. Five percent BSA was used to block the membranes for 2 h. Then, the membranes were incubated with primary antibodies to FPR-1 (1:500; no. ab101701) from Abcam, and phospho-p38 mitogen-activated protein kinase (MAPK; 1:1,000; no. 4511), p38 MAPK (1:1,000; no. 8690), phospho-ERK MAPK (1:1,000; no. 4370), ERK MAPK (1:1,000; no. 4695), phospho-JNK MAPK (1:500; no. 4668), JNK MAPK (1:500; no. 9252), phospho-AKT (1:2,000; no. 4060), AKT (1:1,000; no. 4691), phospho-NF-κB p65 (1:1,000; no. 3033), and β-actin (1:2,000; no. 4970)y, overnight at 4°C and washed with TBST three times for 5 min each followed by incubation in secondary antibody for 2 h. After being washed with TBST, the loaded proteins were visualized by enhanced chemiluminescence reagents

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Neutrophil chemotaxis and functional assay: Isolated human neutrophils were pretreated with Cyclosporine H (0.1-10 nM) for 30 minutes, then stimulated with fMLP (100 nM). Chemotaxis was assessed using a Boyden chamber (migrated cells counted after 2 hours); calcium influx was measured by flow cytometry with fluorescent calcium probe; superoxide anion production was detected by lucigenin chemiluminescence [2]
- Alveolar epithelial cell proinflammatory response assay: A549 cells were seeded in 24-well plates, pretreated with Cyclosporine H (10-100 nM) for 1 hour, then stimulated with mitochondrial peptide (10 μM) for 24 hours. IL-6/IL-8 levels in supernatants were detected by ELISA; ERK1/2, p38, and AKT phosphorylation was analyzed by Western blot [1]

Specific-pathogen-free male BALB/c mice (6–8 wk of age; 18–22 g body wt) were purchased from the Model Animal Research Center of Nanjing University. The mice were housed in individually ventilated cages (5 mice/cage) supplied with filtered air and had free access to sterile water and rodent chow at 23 ± 2°C on a 12-h:12-h light-dark cycle. Animal care, handling, and experimental protocols complied with the guidelines of the Association for Assessment and Accreditation of Laboratory Animal Care International and were approved by the Animal Welfare and Use Committee of Sichuan University (Approval No. 2017049A). All animal studies are reported in compliance with the Animal Research: Reporting of In Vivo Experiments (ARRIVE) guidelines (https://www.nc3rs.org.uk/arrive-guidelines).[1]
To test our hypothesis that acute lung injury causes the release of NFPs into alveolar space and FPR1 plays a role in lung epithelial inflammation, we used two most commonly studied animal models of ALI. LPS (5 μg/g; Escherichia coli O111: B4), hydrochloric acid (2 μl/g; 0.1 N HCl, pH 1.5), or saline as a control was intratracheally administered in mice using a MicroSprayer as previously described by us. Cyclosporin H (CsH; Axxora platform; dissolved in ethanol and diluted by saline), a selective and potent inhibitor of FPR-1, was given by intraperitoneal injection (5 mg/kg) 1 h before LPS or HCl challenge. To thoroughly explore the direct effects of MTDs and NFP in lung injury, mice were randomly divided into six groups (n = 4–6/group at each time point): control group (MTDs/fMLP) receiving HBSS intratracheally, CsH group receiving 2 mg/kg of CsH by tail vein, MTDs group receiving MTDs intratracheally equivalent to the dose isolated from 2.5% liver, MTDs + CsH group receiving CsH 1 h before the stimulation of MTDs, fMLP group receiving 20 μM of fMLP (100 μl; Sigma) intratracheally, and fMLP + CsH group receiving CsH 1 h before the stimulation of fMLP. Mice were anesthetized intraperitoneally with 3% sodium pentobarbital (60 mg/kg) and were intratracheally exposed to the indicated substance during inspiration. All mice revived within 1 h and then returned to cages with food and water.[1]

Absorption, Distribution and Excretion
Cyclosporine is primarily absorbed in the intestine. Individual differences in cyclosporine absorption are significant, with peak bioavailability reaching up to 30%, sometimes occurring 1-8 hours after administration; some patients may experience a second peak. Absorption of cyclosporine in the gastrointestinal tract is incomplete, possibly due to the first-pass effect. Peak plasma concentrations (Cmax) in blood and plasma occur approximately 3.5 hours after administration. A 0.1% cyclosporine ophthalmic emulsion, administered as one drop four times daily, has a peak plasma concentration (Cmax) of 0.67 ng/mL. Note on Absorption Instability: According to Novartis' prescribing information, absorption may be unstable with prolonged use of Santiamine soft capsules and oral solutions. Patients taking soft capsules or oral solutions long-term should have their cyclosporine plasma concentrations monitored regularly and the dosage adjusted accordingly. Compared to other oral formulations of Santiamine, Neoral capsules and solutions exhibit higher absorption rates, resulting in a longer time to peak concentration (Tmax), a higher peak plasma concentration (Cmax) (59% higher), and 29% higher bioavailability. After sulfate conjugation, cyclosporine remains in bile, where it is broken down into its original form and then reabsorbed back into the bloodstream. Cyclosporine is primarily excreted via bile; only 3-6% of the dose (including the original drug and metabolites) is excreted in urine, while 90% of the administered dose is excreted via bile. Of this excretion, less than 1% is excreted unchanged. The distribution of cyclosporine in the blood is as follows: plasma 33%-47%, lymphocytes 4%-9%, granulocytes 5%-12%, and erythrocytes 41%-58%. The reported volume of distribution for cyclosporine is 4-8 L/kg. Due to its high lipophilicity, cyclosporine primarily accumulates in tissues rich in leukocytes and those with high fat content. Ophthalmic drops of cyclosporine can cross the blood-retinal barrier. The clearance of cyclosporine is linear, ranging from 0.38 to 3 L·h/kg, but varies significantly among patients. The clearance of 250 mg of cyclosporine in oral lipid microemulsion soft capsules is approximately 22.5 L/h. The time to peak plasma concentration after oral administration of cyclosporine is 1.5–2.0 hours. Taking it with food delays and reduces absorption. Consuming high-fat or low-fat foods within 30 minutes of administration can reduce AUC by approximately 13% and maximum plasma concentration by approximately 33%. Therefore, individualized dosing regimens must be developed for outpatients. Cyclosporine is widely distributed in extravascular tissues. It has been reported that the steady-state volume of distribution in solid organ transplant recipients can be as high as 3–5 L/kg after intravenous administration. Only 0.1% of cyclosporine is excreted unchanged in the urine. Cyclosporine and its metabolites are primarily excreted in the feces via bile, with only about 6% excreted in the urine. Cyclosporine is also secreted into human milk. Oral absorption of cyclosporine is incomplete. The extent of absorption depends on various factors, including individual patient differences and the formulation used. Clearance of cyclosporine from the blood is typically biphasic, with a terminal half-life of 5–18 hours. Following intravenous infusion, clearance in adult kidney transplant recipients is approximately 5–7 ml/min/kg, but results vary across age groups and patient populations. For example, clearance is slower in heart transplant recipients and faster in pediatric patients. Within the therapeutic range, the dose-time curve is linearly related to the plasma concentration, but significant inter-individual variability necessitates individualized monitoring. Clinicians may administer cyclosporine via continuous intravenous infusion for the first few days post-transplantation, followed by twice-daily oral administration to achieve a plasma cyclosporine concentration (measured by high-performance liquid chromatography) of 75–150 ng/ml (equivalent to a whole blood cyclosporine concentration of 300–600 ng/ml as measured by radioimmunoassay). Maintaining plasma trough cyclosporine concentrations at approximately 75-150 ng/ml appears to be safe; however, this does not completely guarantee the avoidance of nephrotoxicity. Because cyclosporine and its metabolites preferentially distribute to erythrocytes, blood drug concentrations are typically higher than plasma concentrations. When radioimmunoassay shows blood cyclosporine concentrations of 300-600 ng/ml, cerebrospinal fluid concentrations are 10-50 ng/ml. The apparent volume of distribution is approximately 35 L/kg in children under 10 years of age and approximately 4.7 L/kg in adults. The elimination half-life after oral administration of 350 mg cyclosporine is 8.9 hours; after oral administration of 1400 mg, the half-life is 11.9 hours. Cyclosporine is primarily metabolized in the liver, producing 18-25 metabolites. The immunosuppressive activity of cyclosporine metabolites is very low. Cyclosporine is primarily metabolized in the liver via cytochrome P450IIIA oxidase; however, neurotoxicity and potential nephrotoxicity are generally associated with elevated blood cyclosporine metabolite concentrations. Only 0.1% of the dose is excreted unchanged. For more complete data on the absorption, distribution, and excretion of cyclosporine A (7 types), please visit the HSDB record page. Cyclosporine is metabolized in the intestine and liver by CYP450 enzymes, primarily by CYP3A4, with CYP3A5 also contributing. The involvement of CYP3A7 is unclear. Cyclosporine undergoes multiple metabolic pathways, and approximately 25 different metabolites have been identified. Some studies suggest that one of its major active metabolites, AM1, has only 10-20% of the activity of the parent drug. The three major metabolites of cyclosporine are M1, M9, and M4N, produced by oxidation of 1-β, 9-γ, and 4-N-demethylation sites, respectively. Cyclosporine is primarily metabolized in the liver via the cytochrome P450 3A (CYP3A) enzyme system, followed by metabolism in the gastrointestinal tract and kidneys. At least 25 metabolites have been identified in human bile, feces, blood, and urine. Although the cyclic peptide structure of cyclosporine is relatively difficult to metabolize, its side chains are widely metabolized. Compared with the parent drug, the biological activity and toxicity of all metabolites are reduced. The biological half-life of cyclosporine is biphasic and varies greatly under different conditions, but it has been reported to be typically 19 hours. Prescribing information also indicates that the terminal half-life is approximately 19 hours, but ranges from 10 to 27 hours.

Hepatotoxicity
In several large clinical trials, a mild increase in serum bilirubin levels is common at the onset of cyclosporine treatment, but serum ALT or alkaline phosphatase levels are usually not significantly elevated. Elevated serum enzyme levels have also been reported, but are less common. In recent years, these complications appear to have decreased, possibly due to more cautious dosage control and blood concentration monitoring of cyclosporine. Furthermore, in the treatment of autoimmune diseases (excluding many complications related to transplantation), cyclosporine treatment can cause a mild increase in serum alkaline phosphatase in up to 30% of patients, but these abnormalities are usually asymptomatic, resolve spontaneously, and rarely require dose adjustments. In some case series studies, cyclosporine treatment has also been associated with biliary sludge and gallstones. Individual case reports show that clinically significant acute liver injury is associated with cyclosporine. The onset of action of cyclosporine is within several weeks of starting treatment, with serum enzyme elevations exhibiting a cholestatic pattern. Recovery is rapid after discontinuation of cyclosporine, and there have been no reports of cyclosporine-induced chronic hepatitis or acute liver failure.
Probability Score: C (Possibly a rare cause of clinically significant liver damage).

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Impact of Pregnancy and Lactation
◉ Overview of Lactational Use
Cyclosporine levels have varied considerably in some case reports and series studies. This variation appears to be partly due to inconsistencies in sampling times across reports and may also be related to the fat content of breast milk at the time of sampling. At typical maternal cyclosporine blood concentrations, exclusively breastfed infants typically ingest no more than about 2% of the mother's weight-adjusted dose or pediatric transplant maintenance dose, usually less than 1%. Cyclosporine is undetectable in the blood of most breastfed infants; however, it is detectable in the blood of a minority of infants, even when the concentration of cyclosporine in breast milk and the infant's dose appear to be very low.
Many infants were breastfed while their mothers were taking cyclosporine, often concurrently with corticosteroids and sometimes azathioprine. At least two mothers successfully breastfed a second infant after successfully breastfeeding their first. Although not all cases underwent comprehensive follow-up examinations or related reports, there have been no reports of adverse effects of cyclosporine on infant growth, development, or renal function. Expert guidelines in the United States and Europe, the National Transplant Pregnancy Registry, and other experts consider the use of cyclosporine during lactation to be acceptable. If this medication is used during lactation, the breastfed infant should be monitored, and serum drug concentrations may be measured if necessary to rule out toxicity. Due to limited ocular absorption, ophthalmic cyclosporine is not expected to cause any adverse reactions in breastfed infants. To significantly reduce the amount of medication entering breast milk after eye drops administration, press the tear duct near the corner of the eye with your finger for at least 1 minute, then blot away any excess medication with absorbent paper. ◉ Effects on Breastfed Infants
One infant was breastfed, and follow-up results showed that the infant was in good health.
One mother took 3 mg/kg of cyclosporine twice daily, exclusively breastfed her infant until weaning, and continued partial breastfeeding after weaning until the infant was 14 months old. The infant's renal function was stable, and the infant was in good health at 2 years of age. This mother also breastfed her second infant. Seven infants were breastfed for 4 to 12 months while their mothers were taking cyclosporine and prednisolone (six of whom were also taking azathioprine). Their renal function was unaffected, and their growth and development were normal. One mother partially breastfed her infant while taking cyclosporine, azathioprine, and prednisone. No follow-up data were reported. One infant was exclusively breastfed for 10.5 months while a mother was taking cyclosporine 300 mg twice daily, along with azathioprine and prednisone. Partial breastfeeding continued for two years. The infant's growth and development were normal at 12 months. This mother also breastfed her second child while taking the same medication. Four infants were breastfed while their mothers were taking cyclosporine. In three cases, no clinical adverse events were observed during follow-up, and one infant had normal serum creatinine and blood urea nitrogen (BUN) levels. No follow-up report was found for the fourth infant. Two cases were reported involving infants whose mothers were taking cyclosporine and breastfeeding. One mother took 200 mg of cyclosporine daily, along with azathioprine, prednisone, diltiazem, and folic acid. The other mother took 120 mg of cyclosporine daily, along with methyldopa, prednisone, and calcitriol. Both mothers initially exclusively breastfed for 5 months and 14 months, respectively. The infants were reported to be healthy with normal kidney function. A woman with severe ulcerative colitis during pregnancy took 5 mg/kg of cyclosporine daily from week 26 of gestation and continued to take it while breastfeeding. She adequately breastfed her infant, who was healthy at 3 months of age. The National Transplant Pregnancy Registry reported data collected between 1991 and 2011 from mothers who breastfed after organ transplantation. A total of 43 mothers who received transplants (primarily kidney transplants) used cyclosporine while breastfeeding and breastfed a total of 49 infants. The duration of breastfeeding ranged from 1 week to 2 years, and the follow-up period for children ranged from several weeks to 16 years. One infant experienced a mild increase in platelet count and an abnormal albumin/globulin ratio (not age-appropriate); by 16 months, laboratory results returned to normal. The remaining infants or children experienced no problems. As of December 2013, 43 mothers breastfed 55 infants for up to 24 months, and the infants experienced no significant adverse reactions. A woman with psoriasis took 200 mg of cyclosporine daily and exclusively breastfed her infant for 6 months. The infant was developing normally at 12 months, and no significant adverse drug reactions were detected in the breast milk. A woman with nephrotic syndrome took cyclosporine, prednisone, and hydroxychloroquine during pregnancy and lactation. During lactation, she took 125 mg of cyclosporine every morning and 100 mg every evening (total daily dose of 3 mg/kg), and 200 mg of hydroxychloroquine and 30 mg of prednisone daily. Her twins were partially breastfed (70% to 80% breast milk) on day 7 postpartum and she continued breastfeeding for several months. The infants had normal weight gain at one month postpartum and no adverse events occurred in the first three months postpartum.
◉ Effects on breastfeeding and lactation
No relevant published information was found as of the revision date.

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Protein binding
Approximately 50% of the administered dose is absorbed by erythrocytes and approximately 34% is bound to lipoproteins. The prescribing information for Sandimmune indicates that 90% is primarily bound to lipoproteins.

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In vitro studies have shown that cyclosporine H at concentrations up to 500 nM has no significant cytotoxicity to human neutrophils or A549 cells[1][2]

[1]. Mitochondrial peptides cause proinflammatory responses in the alveolar epithelium via FPR-1, MAPKs, and AKT: a potential mechanism involved in acute lung injury. Am J Physiol Lung Cell Mol Physiol. 2018;315(5):L775-L786.

[2]. Cyclosporin H is a potent and selective formyl peptide receptor antagonist. Comparison with N-t-butoxycarbonyl-L-phenylalanyl-L-leucyl-L-phenylalanyl-L- leucyl-L-phenylalanine and cyclosporins A, B, C, D, and E. J Immunol. 1993;150(10):4591-4599.

Cyclosporine A is a white prismatic needle-like crystal (dissolved in acetone) or a white powder. (NTP, 1992)
Cyclosporine is a calcineurin inhibitor, known for its immunomodulatory properties, and is used to prevent organ transplant rejection and treat various inflammatory and autoimmune diseases. It is isolated from Beauveria nivea. Cyclosporine was originally manufactured by Sandoz and approved for use by the U.S. Food and Drug Administration (FDA) in 1983. Currently, Novartis (formerly Sandoz) uses cyclosporine in a variety of products.
Cyclosporine is a calcineurin inhibitor and a potent immunosuppressant, primarily used to prevent cellular rejection after solid organ transplantation. Cyclosporine treatment may cause a mild increase in serum bilirubin and transient increases in serum enzymes; in rare cases, clinically significant cholestatic liver injury may occur. Cyclosporine has been reported in both Mycale hentscheli and Tolypocladium inflatum, with relevant data available. Cyclosporine is a natural cyclic polypeptide immunosuppressant isolated from Beauveria nivea. The exact mechanism of action of cyclosporine is unclear, but it may involve binding to the cytophilin protein, thereby inhibiting calcineurin. The drug appears to specifically and reversibly inhibit immune-active lymphocytes in the G0 or G1 phase of the cell cycle. T lymphocytes are preferentially inhibited, with helper T cells (Thelper) being the primary target. Cyclosporine also inhibits the production and release of lymphokines. (NCI04) A cyclic undecapeptide derived from soil fungal extracts. It is a potent immunosuppressant with specific action against T lymphocytes. It is used to prevent graft rejection in organ and tissue transplantation. (Excerpt from Martindale Pharmacopoeia, 30th edition).
See also: Cyclosporine H (note moved to).

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Drug Indications
Cyclosporine is approved for a variety of diseases. First, it is approved for the prevention of organ rejection in allogeneic kidney, liver, and heart transplants. It is also approved for the prevention of bone marrow transplant rejection. For the above indications, cyclosporine may be used in combination with azathioprine and corticosteroids. Finally, cyclosporine may be used for chronic transplant rejection patients who have previously received immunosuppressive therapy, and for the prevention or treatment of graft-versus-host disease (GVHD). Second, cyclosporine may be used to treat patients with severe active rheumatoid arthritis (RA) who have not responded to methotrexate monotherapy. It may also be used to treat adult patients (non-immunocompromised) with severe, refractory plaque psoriasis who have not responded to or cannot tolerate systemic therapy or have contraindications to systemic therapy. Cyclosporine eye drops are indicated to increase tear production in patients with dry keratoconjunctivitis. In addition, cyclosporine is approved for the treatment of hormone-dependent and hormone-resistant nephrotic syndromes caused by glomerular diseases, which may include minimal change disease, focal segmental glomerulosclerosis, or membranous glomerulonephritis. Cyclosporine eye drops emulsion is indicated for the treatment of vernal keratoconjunctivitis in adults and children. Extra-indications for cyclosporine include the treatment of a variety of autoimmune and inflammatory diseases, such as atopic dermatitis, bullous diseases, ulcerative colitis, juvenile rheumatoid arthritis, uveitis, connective tissue diseases, and idiopathic thrombocytopenic purpura.
FDA Label

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Mechanism of Action
Cyclosporine is a calcineurin inhibitor that inhibits T-cell activation. It binds to the intracellular receptor cyclosporine-1, forming a cyclosporine-cyclosporine complex. This complex subsequently inhibits calcineurin, thereby preventing the dephosphorylation and activation of nuclear factor-AT (NF-AT) on activated T cells, which typically induces an inflammatory response. NF-AT is a transcription factor that promotes the production of various cytokines, such as IL-2, IL-4, interferon-γ, and TNF-α, all of which are involved in inflammatory processes. Specifically, inhibition of IL-2 is considered the reason for the immunosuppressive effect of cyclosporine, and IL-2 is essential for T cell activation or proliferation. Furthermore, inhibition of NF-AT also leads to decreased levels of other factors associated with helper T cell function and thymocyte development. Cyclosporine can suppress some humoral immunity, but its inhibitory effect on T cell-dependent immune mechanisms, such as transplant rejection and certain autoimmune diseases, is stronger. It preferentially inhibits antigen-triggered signal transduction in T lymphocytes, thereby attenuating the expression of various lymphokines, including interleukin-2 (IL-2), and anti-apoptotic proteins. Cyclosporine forms a complex with the target cell cytoplasmic receptor protein cyclophilin. This complex binds to calcineurin, inhibiting calcium-stimulated dephosphorylation of the cytoplasmic component of NF-AT. When the cytoplasmic component of NFAT is dephosphorylated, it translocates to the nucleus and forms a complex with the nuclear components required for complete T cell activation, including the transcriptional activation of IL-2 and other lymphokine genes. Calcineurin activity is inhibited upon physical interaction with the cyclosporine/cyclophilic protein complex, thereby blocking NFAT dephosphorylation. Therefore, the cytoplasmic component of NFAT cannot enter the nucleus, gene transcription cannot be activated, and T lymphocytes cannot respond to specific antigen stimulation. Cyclosporine also increases the expression of transforming growth factor β (TGF-β), a potent inhibitor of IL-2-stimulated T cell proliferation and cytotoxic T lymphocyte (CTL) production. Its exact mechanism of action is unclear, but it appears to be related to the inhibition of interleukin-2 production and release. Interleukin-2 is a proliferation factor essential for inducing cytotoxic T lymphocyte responses to allogeneic antigen stimulation and plays a crucial role in cellular and humoral immune responses. Cyclosporine does not affect the nonspecific defense systems of most cells and does not cause significant bone marrow suppression. The primary pharmacodynamic effect of cyclosporine in T cells is inhibition of calcineurin. The cyclosporine-cyclophilic protein complex competitively binds to calcium ions and the calmodulin-dependent phosphatase calcineurin, thereby inhibiting the dephosphorylation and activation of downstream NFAT (transcription factor). The inhibitory effect on calcineurin is strongest 1-2 hours after administration of Neoral, at which point the blood drug concentration is also highest. Organ transplant recipients receiving the immunosuppressant cyclosporine A (CsA) often experience impaired glucose tolerance, thus promoting the development of diabetes. …The authors found that 2-5 μM CsA can reduce glucose-induced insulin secretion from isolated mouse islets of Langerhans by inhibiting glucose-stimulated cytoplasmic free calcium ion concentration [Ca²⁺]c oscillations. This effect is not due to inhibition of calcineurin, as calcineurin mediates the immunosuppressive effect of cyclosporine A (CsA), and other calcineurin inhibitors, such as deltamethrin and tacrolimus, do not affect the oscillation of [Ca²⁺]c in B cells. The CsA-induced decrease in [Ca²⁺]c to baseline is not caused by direct inhibition of L-type Ca²⁺ channels. CsA is known to be a potent inhibitor of the mitochondrial permeability transition pore (PTP), which has recently been identified as involved in the regulation of oscillations. Therefore, CsA also inhibits the oscillation of cell membrane potential, and these effects are not due to cellular ATP depletion. However, CsA affects the mitochondrial membrane potential ΔΨ by inhibiting the oscillation of ΔΨ. …The observed decrease in [Ca(2+)](c) can be antagonized by the K(+)(ATP) channel blocker tolbutamide, indicating that the stimulus-secretion coupling is interrupted before the K(+)(ATP) channel closes. This leads to the conclusion that CsA alters β-cell function by inhibiting mitochondrial PTP. This terminates oscillatory activity crucial for adequate insulin secretion. Therefore, CsA acts on various targets, thereby inducing immunosuppression and diabetic effects. CsA increases the mRNA expression of CTGF, type I collagen, and type III collagen in the heart. The induction of the CTGF gene is at least partially mediated by angiotensin II.

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Cyclosporin H is a synthetic derivative of cyclosporine and a potent and selective formyl peptide receptor 1 (FPR-1) antagonist[2]
- Its core mechanism involves competitive binding to FPR-1, blocking agonist-mediated signal transduction (calcium influx, MAPK/AKT phosphorylation) and downstream pro-inflammatory responses or neutrophil activation[1][2]
- Unlike cyclosporine A, it does not inhibit calcineurin or bind to cyclophilic proteins, thus eliminating the immunosuppressive effects associated with other cyclosporine analogs[2]
- It has potential therapeutic significance for FPR-1-mediated inflammatory diseases (such as acute lung injury) by inhibiting the release of pro-inflammatory cytokines and neutrophil recruitment[1]
- There are no approved clinical indications; it is mainly used as a research tool for studying FPR-1 biology and inflammatory signaling pathways[1][2]

C62H111N11O12

1202.6113

1215.857

C, 61.92; H, 9.30; N, 12.81; O, 15.96

83602-39-5

5280754

Cyclo[{Abu}-{Sar}-{N(Me)Leu}-Val-{N(Me)Leu}-Ala-{d-Ala}-{N(Me)Leu}-{N(Me)Leu}-{d-N(Me)Val}-{N(Me)Bmt(E)}]

Cyclo[{Abu}-{Sar}-{N(Me)Leu}-V-{N(Me)Leu}-A-{d-Ala}-{N(Me)Leu}-{N(Me)Leu}-{d-N(Me)Val}-{N(Me)Bmt(E)}]

White Solid powder

1.0±0.1 g/cm3

1282.0±65.0 °C at 760 mmHg

162-165ºC

729.1±34.3 °C

0.0±0.6 mmHg at 25°C

1.469

4.28

5

12

15

85

2330

0

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PMATZTZNYRCHOR-JLPRAAIDSA-N

InChI=1S/C62H111N11O12/c1-25-27-28-40(15)52(75)51-56(79)65-43(26-2)58(81)67(18)33-48(74)68(19)44(29-34(3)4)55(78)66-49(38(11)12)61(84)69(20)45(30-35(5)6)54(77)63-41(16)53(76)64-42(17)57(80)70(21)46(31-36(7)8)59(82)71(22)47(32-37(9)10)60(83)72(23)50(39(13)14)62(85)73(51)24/h25,27,34-47,49-52,75H,26,28-33H2,1-24H3,(H,63,77)(H,64,76)(H,65,79)(H,66,78)/b27-25+/t40-,41+,42-,43+,44+,45+,46+,47+,49+,50-,51+,52-/m1/s1

(3R,6S,9S,12R,15S,18S,21S,24S,30S,33S)-30-ethyl-33-[(E,1R,2R)-1-hydroxy-2-methylhex-4-enyl]-1,4,7,10,12,15,19,25,28-nonamethyl-6,9,18,24-tetrakis(2-methylpropyl)-3,21-di(propan-2-yl)-1,4,7,10,13,16,19,22,25,28,31-undecazacyclotritriacontane-2,5,8,11,14,17,20,23,26,29,32-undecone

Cyclosporin H; 5-(N-methyl-D-valine)-Cyclosporin A; Sandoz 37-839

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO: ~100 mg/mL (~83.2 mM)

Solubility in Formulation 1: 3 mg/mL (2.49 mM) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), suspension solution; with sonication.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 30.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: 3 mg/mL (2.49 mM) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), suspension solution; with ultrasonication.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 30.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.5 mg/mL (2.08 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)