FKBP12; calcineurin; macrocyclic lactone

FK-506 and cyclosporin A block translocation of the cytoplasmic component without affecting synthesis of the nuclear subunit in T lymphocytes.[1] K-506 inhibits a Ca(2+)-dependent process necessary for the induction of interleukin-2 transcription, which stops T-cell proliferation. [2] Cyclophilins and FK 506-binding proteins (FKBPs) are two different families of intracellular proteins (immunophilins) that FK 506 binds to. At drug concentrations that prevent activated T cells from producing interleukin 2, FK-506 specifically inhibits cellular calcineurin. [3] By blocking the same subset of early calcium-associated events involved in lymphokine expression, apoptosis, and degranulation, FK-506 and CsA have nearly identical biological effects on cells. The FK-506 binding proteins (FKBPs), a family of intracellular receptors, are where FK-506 binds. [4]

FK-506 results in increase in the paw and tail withdrawal threshold as revealed by behavioral pain assessment in rats against hyperalgesic and allodynic stimuli. Additionally, FK-506 lowers serum nitrate and thiobarbituric acid reactive substance (TBARS) levels. It also lowers tissue myeloperoxidase (MPO) and total calcium levels, while raising tissue reduced glutathione levels in rats. In rats with ischemia reperfusion (I/R), FK-506 reduces the progression of neuronal edema and axonal degeneration. [5]

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The aim of this study was to elucidate the effect of tacrolimus (FK506) and of C-X-C chemokine receptor type 4 (CXCR4), which is a receptor specific to the stromal cell-derived factor-1α (SDF‑1α), on growth and metastasis of hepatocellular carcinoma (HCC). Following treatment with different concentrations of FK506, AMD3100 or normal saline (NS), the proliferation of Morris rat hepatoma 3924A (MH3924A) cells was measured by the MTT assay, the expression of CXCR4 was analyzed with immunohistochemistry, and the morphological changes and the invasiveness of cells were studied with a transwell assay and under a scanning electron microscope, respectively. In addition, August Copenhagen Irish rat models implanted with tumor were used to examine the pathological changes and invasiveness of tumor in vivo, the expression of CXCR4 in tumor tissues and the expression of SDF‑1α in the adjacent tissues to the HCC ones, using immunohistochemistry. In vitro, FK506 (100‑1,000 µg/l) significantly promoted the proliferation of MH3924A cells (P<0.01), and increased the expression of CXCR4 in MH3924A cells, albeit with no significance (P>0.05). By contrast, AMD3100 had no effect on the proliferation of MH3924A cells, but significantly reduced the expression of CXCR4 (P<0.05). The invasiveness of MH3924A cells was significantly (P<0.01) enhanced following treatment with FK506, SDF‑1α, FK506 + AMD3100, FK506 + SDF‑1α or FK506 + AMD3100 + SDF‑1α. In vivo, tumor weight (P=0.041), lymph node metastasis (P=0.002), the number of pulmonary nodules (P=0.012), the expression of CXCR4 in tumor tissues (P=0.048) and that of SDF‑1α in adjacent tissues (P=0.026) were significantly different between the FK506-treated and the NS group. Our results suggest that FK506 promotes the proliferation of MH3924A cells and the expression of CXCR4 and SDF‑1α in vivo. Therefore, inhibiting the formation of the CXCR4/SDF‑1α complex may partly reduce the promoting effect of FK506 on HCC [4].

Tacrolimus (FK506) inhibits calcium-dependent events, such as IL-2 gene transcription, NO synthase activation, cell degranulation, and apoptosis. Tacrolimus also potentiates the actions of glucocorticoids and progesterone by binding to FKBPs contained within the hormone receptor complex, preventing degradation. The agent may enhance expression of the TGFβ-1 gene in a fashion analogous to that demonstrated for CsA. T cell proliferation in response to ligation of the T cell receptor is inhibited by Tacrolimus. Treatment with a low concentration of Tacrolimus (FK506,10 μg/L) does not significantly affect the proliferation of MH3924A cells (P=0.135). Upon treatment with higher concentrations of Tacrolimus (100-1,000 μg/L), the proliferation of MH3924A cells is significantly enhanced (P<0.01). However, when different concentrations of AMD3100 are combined with 100 μg/L Tacrolimus, the in vitro proliferation of MH3924A cells is increased (P<0.01).

Cell Treatment and Lysis. Immunosuppressive agents were dissolved in ethanol at concentrations 1000-fold more than the concentration desired for cell treatments. Cells (106) were suspended in 1 ml of complete medium in microcentrifuge tubes; 1 Al of ethanol or of the ethanolic solution of FK 506, CsA, or rapamycin was added, and the cells were incubated at 37°C for 1 hr. Cells were washed twice with 1 ml of phosphate-buffered saline (PBS) on ice and lysed in 50 ,u of hypotonic buffer containing 50 mM Tris (pH 7.5); 0.1 mM EGTA; 1 mM EDTA; 0.5 mM dithiothreitol; and 50 ,ug of phenylmethylsulfonyl fluoride, 50 ,g of soybean trypsin inhibitor, 5 ,g of leupeptin, and 5 ,ug of aprotinin per ml. Lysates were subjected to three cycles of freezing in liquid nitrogen followed by thawing at 30°C and then were centrifuged at 4°C for 10 min at 12,000 x g.[3]

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Interleukin 2 (IL-2) Assay. Jurkat cells were cultured in complete medium at 106 cells per ml in 96-well flat-bottom plates. Cells were stimulated with OKT3 monoclonal antibody (1:4000 dilution of ascites) and 2 ng of phorbol 12- myristate 13-acetate (PMA) per ml for 24 hr in the presence or absence of FK 506 or CsA. IL-2 production was quantitated by measuring the ability of serial dilutions of cell supernatants to support the proliferation of the IL-2- dependent cell line CTLL-20 as described. One unit is defined as the amount of recombinant human IL-2 required to induce half-maximal proliferation of the CTLL-20 cells. FK 506 and CsA added directly to CTLL-20 cells do not inhibit IL-2-dependent proliferation. [3]

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The immunosuppressive agents cyclosporin A (CsA) and FK 506 bind to distinct families of intracellular proteins (immunophilins) termed cyclophilins and FK 506-binding proteins (FKBPs). Recently, it has been shown that, in vitro, the complexes of CsA-cyclophilin and FK 506-FKBP-12 bind to and inhibit the activity of calcineurin, a calcium-dependent serine/threonine phosphatase. We have investigated the effects of drug treatment on phosphatase activity in T lymphocytes. Calcineurin is expressed in T cells, and its activity can be measured in cell lysates. Both CsA and FK 506 specifically inhibit cellular calcineurin at drug concentrations that inhibit interleukin 2 production in activated T cells. Rapamycin, which binds to FKBPs but exhibits different biological activities than FK 506, has no effect on calcineurin activity. Furthermore, excess concentrations of rapamycin prevent the effects of FK 506, apparently by displacing FK 506 from FKBPs. These results show that calcineurin is a target of drug-immunophilin complexes in vivo and establish a physiological role for calcineurin in T-cell activation.[3]

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Cells were cultured in the presence of 10 nM FK 506 for 1 hr and washed, and phosphatase activity was measured in lysates.

Mice; Six-week-old male C57BL/6J mice are maintained in a temperature- and humidity-controlled room with a 12-h light-dark cycle. FTacrolimus 30 mg/kg is given orally to colitic mice (n=10) for either 7 or 14 days (Days 10 to 23) as part of the multiple dosing study. The same regimen is used to administer placebos to the control group (n = 10) and the normal group (n = 5). 10 mL/kg of placebo or tacrolimus is given. On the day after the final dose, mice are put to death by CO2 inhalation. For the single-dose study, colitic mice are given Tacrolimus or a placebo (n=8) orally once on Days 7, 10, 17, or 24. The same procedure is used to administer a placebo to normal mice (n = 4). Eight hours after dosing, mice are put to death by CO2 inhalation.

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We investigated the effect of tacrolimus, a calcineurin inhibitor, on dextran sulfate sodium (DSS)-induced colitis. After inducing colitis in C57BL/6 mice by administering DSS solution as drinking water for 7 d, the animals were treated with tacrolimus. Severity of colonic inflammation was evaluated based on colon weight per unit length. Levels of cytokines (interferon (IFN)-γ, interleukin (IL)-1β, IL-2, IL-4, IL-5, IL-6, IL-12, and tumor necrosis factor (TNF)-α) released from isolated inflamed colons of mice treated with tacrolimus or vehicle were also measured. Treatment with tacrolimus for 14 d reduced the colon weight per unit length and suppressed the release of IFN-γ and IL-1β, but not other cytokines, in inflamed colons of colitic mice compared with vehicle-treated mice. A positive correlation was noted between colon weight per unit length and released level of IFN-γ or IL-1β. The release of IFN-γ and IL-1β was also suppressed after single dosing with tacrolimus to colitic mice. Taken together, these results suggested that tacrolimus ameliorated DSS-induced colitis by suppressing release of IFN-γ and IL-1β from inflamed colon.[4]

Absorption, Distribution and Excretion
Absorption of tacrolimus from the gastrointestinal tract after oral administration is incomplete and variable. The absolute bioavailability in adult kidney transplant patients is 17±10%; in adults liver transplant patients is 22±6%; in healthy subjects is 18±5%. The absolute bioavailability in pediatric liver transplant patients was 31±24%. Tacrolimus maximum blood concentrations (Cmax) and area under the curve (AUC) appeared to increase in a dose-proportional fashion in 18 fasted healthy volunteers receiving a single oral dose of 3, 7, and 10 mg. When given without food, the rate and extent of absorption were the greatest. The time of the meal also affected bioavailability. When given immediately after a meal, mean Cmax was reduced 71%, and mean AUC was reduced 39%, relative to the fasted condition. When administered 1.5 hours following the meal, mean Cmax was reduced 63%, and mean AUC was reduced 39%, relative to the fasted condition.
In man, less than 1% of the dose administered is excreted unchanged in urine. When administered IV, fecal elimination accounted for 92.6±30.7%, urinary elimination accounted for 2.3±1.1%.
2.6 ± 2.1 L/kg [pediatric liver transplant patients]
1.07 ± 0.20 L/kg [patients with renal impairment, 0.02 mg/kg/4 hr dose, IV]
3.1 ± 1.6 L/kg [Mild Hepatic Impairment, 0.02 mg/kg/4 hr dose, IV]
3.7 ± 4.7 L/kg [Mild Hepatic Impairment, 7.7 mg dose, PO]
3.9 ± 1.0 L/kg [Severe hepatic impairment, 0.02 mg/kg/4 hr dose, IV]
3.1 ± 3.4 L/kg [Severe hepatic impairment, 8 mg dose, PO]
0.040 L/hr/kg [healthy subjects, IV]
0.172 ± 0.088 L/hr/kg [healthy subjects, oral]
0.083 L/hr/kg [adult kidney transplant patients, IV]
0.053 L/hr/kg [adult liver transplant patients, IV]
0.051 L/hr/kg [adult heart transplant patients, IV]
0.138 ± 0.071 L/hr/kg [pediatric liver transplant patients]
0.12 ± 0.04 (range 0.06-0.17) L/hr/kg [pediatric kidney transplant patients]
0.038 ± 0.014 L/hr/kg [patients with renal impairment, 0.02 mg/kg/4 hr dose, IV]
0.042 ± 0.02 L/hr/kg [Mild Hepatic Impairment, 0.02 mg/kg/4 hr dose, IV]
0.034 ± 0.019 L/hr/kg [Mild Hepatic Impairment, 7.7 mg dose, PO]
0.017 ± 0.013 L/hr/kg [Severe hepatic impairment, 0.02 mg/kg/4 hr dose, IV]
0.016 ± 0.011 L/hr/kg [Severe hepatic impairment, 8 mg dose, PO]
The aim of this study was to assess tacrolimus levels in breast milk and neonatal exposure during breastfeeding. An observational cohort study was performed in two tertiary referral high-risk obstetric medicine clinics. Fourteen women taking tacrolimus during pregnancy and lactation, and their 15 infants, 11 of whom were exclusively breast-fed, were assessed. Tacrolimus levels were analyzed by liquid chromatography-tandem mass spectrometry. Samples from mothers and cord blood were collected at delivery and from mothers, infants, and breast milk postnatally where possible. All infants with serial sampling had a decline in tacrolimus level, which was approximately 15% per day (ratio of geometric mean concentrations 0.85; 95% confidence interval, 0.82-0.88; P<0.001). Breast-fed infants did not have higher tacrolimus levels compared with bottle-fed infants (median 1.3 ug/L [range, 0.0-4.0] versus 1.0 ug/L (range, 0.0-2.3), respectively; P=0.91). Maximum estimated absorption from breast milk is 0.23% of maternal dose (weight-adjusted). Ingestion of tacrolimus by infants via breast milk is negligible. Breastfeeding does not appear to slow the decline of infant tacrolimus levels from higher levels present at birth.
Maternal and umbilical cord (venous and arterial) samples were obtained at delivery from eight solid organ allograft recipients to measure tacrolimus and metabolite bound and unbound concentrations in blood and plasma. Tacrolimus pharmacokinetics in breast milk were assessed in one subject. Mean (+ or - SD) tacrolimus concentrations at the time of delivery in umbilical cord venous blood (6.6 + or - 1.8 ng ml(-1)) were 71 + or - 18% (range 45-99%) of maternal concentrations (9.0 + or - 3.4 ng ml(-1)). The mean umbilical cord venous plasma (0.09 + or - 0.04 ng ml(-1)) and unbound drug concentrations (0.003 + or - 0.001 ng ml(-1)) were approximately one fifth of the respective maternal concentrations. Arterial umbilical cord blood concentrations of tacrolimus were 100 + or - 12% of umbilical venous concentrations. In addition, infant exposure to tacrolimus through the breast milk was less than 0.3% of the mother's weight-adjusted dose. Differences between maternal and umbilical cord tacrolimus concentrations may be explained in part by placental P-gp function, greater red blood cell partitioning and higher haematocrit levels in venous cord blood.
Ten colostrum samples were obtained from six women in the immediate postpartum period (0-3 days) with a mean drug concentration of 0.79 ng/mL (range 0.3-1.9 ng/mL). The median milk:maternal plasma ratio was 0.5.
The plasma protein binding of tacrolimus is approximately 99% and is independent of concentration over a range of 5-50 ng/mL. Tacrolimus is bound mainly to albumin and alpha-1-acid glycoprotein, and has a high level of association with erythrocytes. The distribution of tacrolimus between whole blood and plasma depends on several factors, such as hematocrit, temperature at the time of plasma separation, drug concentration, and plasma protein concentration. In a US study, the ratio of whole blood concentration to plasma concentration averaged 35 (range 12 to 67). There was no evidence based on blood concentrations that tacrolimus accumulates systemically upon intermittent topical application for periods of up to 1 year. As with other topical calcineurin inhibitors, it is not known whether tacrolimus is distributed into the lymphatic system.
For more Absorption, Distribution and Excretion (Complete) data for Tacrolimus (9 total), please visit the HSDB record page.

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Metabolism / Metabolites
The metabolism of tacrolimus is predominantly mediated by CYP3A4 and secondarily by CYP3A5. Tacrolimus is metabolized into 8 metabolites: 13-demethyl tacrolimus, 31-demethyl tacrolimus, 15-demethyl tacrolimus, 12-hydroxy tacrolimus, 15,31-didemethyl tacrolimus, 13,31-didemethyl tacrolimus, 13,15-didemethyl tacrolimus, and a final metabolite involving O-demethylation and the formation of a fused ring. The major metabolite identified in incubations with human liver microsomes is 13-demethyl tacrolimus. In in vitro studies, a 31-demethyl metabolite has been reported to have the same activity as tacrolimus.
Tacrolimus is extensively metabolized by the mixed-function oxidase system, primarily the cytochrome P-450 system (CYP3A). A metabolic pathway leading to the formation of 8 possible metabolites has been proposed. Demethylation and hydroxylation were identified as the primary mechanisms of biotransformation in vitro. The major metabolite identified in incubations with human liver microsomes is 13-demethyl tacrolimus. In in vitro studies, a 31-demethyl metabolite has been reported to have the same activity as tacrolimus.
Fk_506 has known human metabolites that include 13-O-Desmethyltacrolimus and 15-O-Desmethyltacrolimus.

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Biological Half-Life
The elimination half life in adult healthy volunteers, kidney transplant patients, liver transplants patients, and heart transplant patients are approximately 35, 19, 12, 24 hours, respectively. The elimination half life in pediatric liver transplant patients was 11.5±3.8 hours, in pediatric kidney transplant patients was 10.2±5.0 (range 3.4-25) hours.
In a mass balance study of IV administered radiolabeled tacrolimus to 6 healthy volunteers, ... the elimination half-life based on radioactivity was 48.1+ or - 15.9 hours whereas it was 43.5 + or- 11.6 hours based on tacrolimus concentrations. ... When administered PO, the elimination half-life based on radioactivity was 31.9 + or- 10.5 hours whereas it was 48.4 + or - 12.3 hours based on tacrolimus concentrations ... .
... A case of tacrolimus toxicity in a non-transplant patient /is presented/. ... /The/ patient's tacrolimus dose was 2.1 mg/kg/day for 4 days (therapeutic 0.03 to 0.05 mg/kg/day). Her tacrolimus elimination half-life was 16.5 hours, compared to a mean half-life in healthy volunteers of 34.2 +/- 7.7 hours. ...

Toxicity Summary
IDENTIFICATION AND USE: Tacrolimus is white to off-white crystalline powder. It is a calcineurin-inhibitor immunosuppressant available in several preparations. Tacrolimus in both oral capsules and a solution for IV injection is used for prophylaxis of organ rejection in patients receiving liver, kidney or heart transplants. Tacrolimus topical ointment is used as a second-line therapy for the short-term and non-continuous chronic treatment of moderate to severe atopic dermatitis in non-immunocompromised adults and children. HUMAN EXPOSURE AND TOXICITY: While most acute overdosages of tacrolimus at up to 30 times the intended dose have been asymptomatic and all patients recovered with no sequelae, some acute overdosages were followed by adverse reactions including tremors, abnormal renal function, hypertension, and peripheral edema. At therapeutic doses, patients receiving tacrolimus are at increased risk of developing lymphomas and other malignancies, particularly of the skin, as well as an increased risk of developing bacterial, viral, fungal, and protozoal infections, including opportunistic infections. These infections may lead to serious, including fatal, outcomes. While there are no adequate and well-controlled studies in pregnant women, the use of tacrolimus during pregnancy in humans has been associated with neonatal hyperkalemia and renal dysfunction. ANIMAL STUDIES: Both rats and baboons showed a similar toxicologic profile following oral or intravenous administration of tacrolimus. Toxicity following intravenous administration was evident at lower doses than after oral administration for both rats and baboons. Toxicity was seen at lower doses in rats than in baboons. The primary target organs were the kidneys, pancreatic islets of Langerhans and exocrine pancreas, spleen, thymus, gastrointestinal tract, and lymph nodes. In addition, decreases in erythrocyte parameters were seen. Tacrolimus also produced reproductive and developmental toxicity in both rats and rabbits. In rats, chronic oral administration of tacrolimus at high doses resulted in changes in sex organs, and glaucoma/eye changes. Oral doses of tacrolimus at 1 and 3.2 mg/kg/day produced overt signs of parental toxicity and changes in the fertility and general reproductive performance of rats. Effects on reproduction included some embryo lethality, reduced number of implantations, increased incidence of post-implantation loss, and reduced embryo and offspring viability. In a rabbit teratology study, signs of maternal toxicity including reduced body weight were produced at all oral doses of tacrolimus administered (0.1, 0.32, or 1 mg/kg/day). Doses of 0.32 and 1 mg/kg/day produced signs of developmental toxicity, such as increased incidence of post-implantation losses, reduced number of viable fetuses, and increased incidences of morphological variations. In a rat teratology study, increased post-implantation loss was observed at 3.2 mg/kg/day. Maternal doses of 1 mg/kg/day decreased the body weight of F1 offspring. Decreased body weight, reduced survival number, and some skeletal alterations were seen in F1 offspring at maternal doses of 3.2 mg/kg/day. Tacrolimus did not exhibit genotoxic activity in vitro in bacterial asaays in Salmonella typhimurium and Escherichia coli or mammalian assays in Chinese hamster lung-derived cells assays. No evidence of mutagenicity was observed in vitro in the CHO/HGPRT assay (the Chinese hamster ovary cell assay (CHO), which measures forward mutation of the HGPRT locus) or in vivo in clastogenicity assays performed in mice. Tacrolimus also did not cause unscheduled DNA synthesis in rodent hepatocytes.

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Interactions
With a given dose of mycophenolic acid (MPA) products, exposure to MPA is higher with Prograf co-administration than with cyclosporine co-administration because cyclosporine interrupts the enterohepatic recirculation of MPA while tacrolimus does not. Clinicians should be aware that there is also a potential for increased MPA exposure after crossover from cyclosporine to Prograf in patients concomitantly receiving MPA-containing products.
Grapefruit juice inhibits CYP3A-enzymes resulting in increased tacrolimus whole blood trough concentrations, and patients should avoid eating grapefruit or drinking grapefruit juice with tacrolimus.
Since tacrolimus is metabolized mainly by CYP3A enzymes, drugs or substances known to inhibit these enzymes may increase tacrolimus whole blood concentrations. Drugs known to induce CYP3A enzymes may decrease tacrolimus whole blood concentrations. Dose adjustments may be needed along with frequent monitoring of tacrolimus whole blood trough concentrations when Prograf is administered with CYP3A inhibitors or inducers. In addition, patients should be monitored for adverse reactions including changes in renal function and QT prolongation.
Verapamil, diltiazem, nifedipine, and nicardipine inhibit CYP3A metabolism of tacrolimus and may increase tacrolimus whole blood concentrations. Monitoring of whole blood concentrations and appropriate dosage adjustments of tacrolimus are recommended when these calcium channel blocking drugs and tacrolimus are used concomitantly.
For more Interactions (Complete) data for Tacrolimus (18 total), please visit the HSDB record page.

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Non-Human Toxicity Values
LD50 Rat iv 23,600 ug/kg /Tacrolimus hydrate/
LD50 Rat oral 134 mg/kg /Tacrolimus hydrate/

[1]. Nature. 1991 Aug 29;352(6338):803-7.

[2]. Nature. 1992 Jun 25;357(6380):692-4.

[3]. Proc Natl Acad Sci U S A. 1992 May 1;89(9):3686-90.

[4]. Tacrolimus promotes hepatocellular carcinoma and enhances CXCR4/SDF 1α expression in vivo. Mol Med Rep. 2014 Aug;10(2):585-92.

Therapeutic Uses
Immunosuppressive Agents
Prograf is indicated for the prophylaxis of organ rejection in patients receiving allogeneic kidney transplants. It is recommended that Prograf be used concomitantly with azathioprine or mycophenolate mofetil (MMF) and adrenal corticosteroids. /Included in US product label/
Prograf is indicated for the prophylaxis of organ rejection in patients receiving allogeneic liver transplants. It is recommended that Prograf be used concomitantly with adrenal corticosteroids. Therapeutic drug monitoring is recommended for all patients receiving Prograf. /Included in US product label/
Prograf is indicated for the prophylaxis of organ rejection in patients receiving allogeneic heart transplants. It is recommended that Prograf be used concomitantly with azathioprine or mycophenolate mofetil (MMF) and adrenal corticosteroids. /Included in US product label/
For more Therapeutic Uses (Complete) data for Tacrolimus (13 total), please visit the HSDB record page.

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Drug Warnings
/BOXED WARNING/ MALIGNANCIES AND SERIOUS INFECTIONS. Increased risk of development of lymphoma and other malignancies, particularly of the skin, due to immunosuppression. Increased susceptibility to bacterial, viral, fungal, and protozoal infections, including opportunistic infections. Only physicians experienced in immunosuppressive therapy and management of organ transplant patients should prescribe Prograf. Patients receiving the drug should be managed in facilities equipped and staffed with adequate laboratory and supportive medical resources. The physician responsible for maintenance therapy should have complete information requisite for the follow-up of the patient.
/BOXED WARNING/ WARNING: Long-term Safety of Topical Calcineurin Inhibitors Has Not Been Established Although a causal relationship has not been established, rare cases of malignancy (e.g., skin and lymphoma) have been reported in patients treated with topical calcineurin inhibitors, including Protopic Ointment. Therefore: Continuous long-term use of topical calcineurin inhibitors, including Protopic Ointment, in any age group should be avoided, and application limited to areas of involvement with atopic dermatitis; Protopic Ointment is not indicated for use in children less than 2 years of age; Only 0.03% Protopic Ointment is indicated for use in children 2-15 years of age.
Topical tacrolimus therapy should be avoided for malignant or premalignant skin conditions (e.g., cutaneous T-cell lymphoma (CTCL)), which may appear clinically similar to dermatitis.
Because of a potential increased risk for skin cancer, patients /using topical tacrolimus/ should be advised to limit exposure to sunlight or other UV light by wearing protective clothing and using a broad-spectrum sunscreen with a high protection factor.
For more Drug Warnings (Complete) data for Tacrolimus (42 total), please visit the HSDB record page.

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Pharmacodynamics
Tacrolimus acts by reducing peptidyl-prolyl isomerase activity by binding to the immunophilin FKBP-12 (FK506 binding protein) creating a new complex. This inhibits both T-lymphocyte signal transduction and IL-2 transcription. Tacrolimus has similar activity to cyclosporine but rates of rejection are lower with tacrolimus. Tacrolimus has also been shown to be effective in the topical treatment of eczema, particularly atopic eczema. It suppresses inflammation in a similar way to steroids, but is not as powerful. An important dermatological advantage of tacrolimus is that it can be used directly on the face; topical steroids cannot be used on the face, as they thin the skin dramatically there. On other parts of the body, topical steroid are generally a better treatment.

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Cyclosporin A and FK506 inhibit T- and B-cell activation and other processes essential to an effective immune response. In T lymphocytes these drugs disrupt an unknown step in the transmission of signals from the T-cell antigen receptor to cytokine genes that coordinate the immune response. The putative intracellular receptors for FK506 and cyclosporin are cis-trans prolyl isomerases. Binding of the drug inhibits isomerase activity, but studies with other prolyl isomerase inhibitors and analysis of cyclosporin-resistant mutants in yeast suggest that the effects of the drug result from the formation of an inhibitory complex between the drug and isomerase, and not from inhibition of isomerase activity. A transcription factor, NF-AT, which is essential for early T-cell gene activation, seems to be a specific target of cyclosporin A and FK506 action because transcription directed by this protein is blocked in T cells treated with these drugs, with little or no effect on other transcription factors such as AP-1 and NF-kappa B. Here we demonstrate that NF-AT is formed when a signal from the antigen receptor induces a pre-existing cytoplasmic subunit to translocate to the nucleus and combine with a newly synthesized nuclear subunit of NF-AT. FK506 and cyclosporin A block translocation of the cytoplasmic component without affecting synthesis of the nuclear subunit. [1]

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Antigen recognition by the T-cell receptor (TCR) initiates events including lymphokine gene transcription, particularly interleukin-2, that lead to T-cell activation. The immunosuppressive drugs, cyclosporin A (CsA) and FK-506, prevent T-cell proliferation by inhibiting a Ca(2+)-dependent event required for induction of interleukin-2 transcription. Complexes of FK-506 or CsA and their respective intracellular binding proteins inhibit the calmodulin-dependent protein phosphatase, calcineurin, in vitro. The pharmacological relevance of this observation to immunosuppression or drug toxicity is undetermined. Calcineurin, although present in lymphocytes, has not been implicated in TCR-mediated activation of lymphokine genes or in transcriptional regulation in general. Here we report that transfection of a calcineurin catalytic subunit increases the 50% inhibitory concentration (IC50) of the immunosuppressants FK-506 and CsA, and that a mutant subunit acts in synergy with phorbol ester alone to activate the interleukin-2 promoter in a drug-sensitive manner. These results implicate calcineurin as a component of the TCR signal transduction pathway by demonstrating its role in the drug-sensitive activation of the interleukin-2 promoter.[2]

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The immunosuppressive agents cyclosporin A (CsA) and FK 506 bind to distinct families of intracellular proteins (immunophilins) termed cyclophilins and FK 506-binding proteins (FKBPs). Recently, it has been shown that, in vitro, the complexes of CsA-cyclophilin and FK 506-FKBP-12 bind to and inhibit the activity of calcineurin, a calcium-dependent serine/threonine phosphatase. We have investigated the effects of drug treatment on phosphatase activity in T lymphocytes. Calcineurin is expressed in T cells, and its activity can be measured in cell lysates. Both CsA and FK 506 specifically inhibit cellular calcineurin at drug concentrations that inhibit interleukin 2 production in activated T cells. Rapamycin, which binds to FKBPs but exhibits different biological activities than FK 506, has no effect on calcineurin activity. Furthermore, excess concentrations of rapamycin prevent the effects of FK 506, apparently by displacing FK 506 from FKBPs. These results show that calcineurin is a target of drug-immunophilin complexes in vivo and establish a physiological role for calcineurin in T-cell activation.[3]

C44H69NO12

804.0182

803.481

C, 57.92; H, 5.69; Cl, 3.64; F, 5.85; N, 7.19; O, 9.85; S, 9.87

104987-11-3

Tacrolimus monohydrate;109581-93-3;Tacrolimus-13C,d2;1356841-89-8

445643

White to off-white solid powder

1.2±0.1 g/cm3

871.7±75.0 °C at 760 mmHg

113-115°C

481.0±37.1 °C

0.0±0.6 mmHg at 25°C

1.549

fungus Streptomyces tsukubaensis.

3.96

3

12

7

57

1480

14

O1[C@]2(C(C(N3C([H])([H])C([H])([H])C([H])([H])C([H])([H])[C@@]3([H])C(=O)O[C@]([H])(/C(/C([H])([H])[H])=C(\[H])/[C@]3([H])C([H])([H])C([H])([H])[C@]([H])([C@@]([H])(C3([H])[H])OC([H])([H])[H])O[H])[C@]([H])(C([H])([H])[H])[C@]([H])(C([H])([H])C([C@]([H])(C([H])([H])C([H])=C([H])[H])C([H])=C(C([H])([H])[H])C([H])([H])[C@]([H])(C([H])([H])[H])C([H])([H])[C@@]([H])([C@]1([H])[C@]([H])(C([H])([H])[C@@]2([H])C([H])([H])[H])OC([H])([H])[H])OC([H])([H])[H])=O)O[H])=O)=O)O[H] |c:78|

QJJXYPPXXYFBGM-LFZNUXCKSA-N

InChI=1S/C44H69NO12/c1-10-13-31-19-25(2)18-26(3)20-37(54-8)40-38(55-9)22-28(5)44(52,57-40)41(49)42(50)45-17-12-11-14-32(45)43(51)56-39(29(6)34(47)24-35(31)48)27(4)21-30-15-16-33(46)36(23-30)53-7/h10,19,21,26,28-34,36-40,46-47,52H,1,11-18,20,22-24H2,2-9H3/b25-19+,27-21+/t26-,28+,29+,30-,31+,32-,33+,34-,36+,37-,38-,39+,40+,44+/m0/s1

(1R,9S,12S,13R,14S,17R,18E,21S,23S,24R,25S,27R)-1,14-dihydroxy-12-[(E)-1-[(1R,3R,4R)-4-hydroxy-3-methoxycyclohexyl]prop-1-en-2-yl]-23,25-dimethoxy-13,19,21,27-tetramethyl-17-prop-2-enyl-11,28-dioxa-4-azatricyclo[22.3.1.04,9]octacos-18-ene-2,3,10,16-tetrone

FR900506;FR 900506; FR-900506; FK 506; FK-506; FK506; fujimycin; Prograf; Protopic; Advagraf; Astagraf XL; Fujimycin; 104987-11-3; Prograf; Tsukubaenolide; Tacrolimus anhydrous; Protopic; Anhydrous Tacrolimus;

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: This product requires protection from light (avoid light exposure) during transportation and storage.

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

DMSO: ~94 mg/mL (~116.9 mM)
Water: <1 mg/mL
Ethanol: ~83 mg/mL (~103.2 mM)

Solubility in Formulation 1: 2.75 mg/mL (3.42 mM) in 5% DMSO + 40% PEG300 + 5% Tween80 + 50% Saline (add these co-solvents sequentially from left to right, and one by one), suspension solution; with sonication.
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: ≥ 2.5 mg/mL (3.11 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (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 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 3: 2.5 mg/mL (3.11 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 25.0 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 4: ≥ 2.5 mg/mL (3.11 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 corn oil and mix evenly.

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Solubility in Formulation 5: 5% DMSO+corn oil: 15mg/mL

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