Ocular inflammatory indications for immunosuppressive therapy
“Corticosteroid-sparing” therapy: when disease can be controlled with corticosteroids (usually oral, sometimes topical), but expected toxicity is unacceptably high at the dose required to maintain control of the inflammation
Inflammation recalcitrant to corticosteroids
For management of specific diseases
Behçet disease with posterior uveitis
Birdshot retinochoroiditis
Serpiginous choroiditis (unassociated with tuberculosis)
Necrotizing scleritis
Pemphigoid with cicatrizing conjunctivitis
Multifocal choroiditis with panuveitisa
Sympathetic ophthalmiaa
Immunosuppressive Therapies for Ocular Inflammation
The immunosuppressive drugs commonly used for treatment of ocular inflammation can be divided into general categories based on their mechanism: antimetabolites (methotrexate, azathioprine, and mycophenolate mofetil), T-cell inhibitors (cyclosporine, tacrolimus), and alkylating agents (cyclophosphamide and chlorambucil) (see Table 9.2). “Biological” agents are a more recent immunosuppressive drug category that is reported separately (see Chap. 4).
Table 9.2
Conventional immunomodulatory agents in uveitis and ocular inflammation
Class | Drug | Mechanism |
---|---|---|
Antimetabolite | Azathioprine | Alters purine metabolism |
Methotrexate | Dihydrofolate reductase inhibitor | |
Mycophenolate mofetil, mycophenolic acid | IMO dehydrogenase inhibitor (purine synthesis) | |
Leflunomide | Dihydroorotate dehydrogenase inhibitor (pyrimidine synthesis) | |
T-cell inhibitor | Cyclosporine-modified (Neoral) | T-cell inhibitor |
Cyclosporine (Sandimmune) | T-cell inhibitor | |
Tacrolimus | T-cell inhibitor | |
Alkylating agent | Cyclophosphamide | Lymphotoxicity |
Chlorambucil | Lymphotoxicity |
Antimetabolites
Methotrexate
Methotrexate is 4-amino-N-methylptereoylglutamic acid, a folic acid analog. It initially was developed as chemotherapy for treatment of acute leukemia in 1948 [13]. Methotrexate has been used as a mainstay of the treatment of autoimmune diseases such as rheumatoid arthritis, psoriasis, systemic lupus erythematosus (SLE), inflammatory bowel disease, ankylosing spondylitis, refractory juvenile idiopathic arthritis, and sarcoidosis for decades. It was first reported to treat ocular inflammatory diseases in 1965 by Wong and Hersh [14]. Methotrexate has been a first-line immunosuppressive agent for treatment of uveitis since the 1980s (see Table 9.3).
Table 9.3
Methotrexate
Methotrexate: pharmacology |
Folate analog |
Binds and completely inactivates the dihydrofolate reductase enzyme (DHFR) |
Inhibits thymidylate production and purine synthesis resulting in inhibition of DNA and RNA synthesis, cell division in S-phase cell cycle, and active cell proliferation |
Immunologic action: suppresses both B and T cells |
Methotrexate also inhibits other folate-dependent enzymes |
Methotrexate: metabolism |
Absorbed through a dose-dependent active transport system |
Mean absorption time is 1.2 h |
Half-life is 6 h |
Metabolized in the liver and excreted in urine |
High oral bioavailability |
Bioavailability of methotrexate is affected by nonsteroidal anti-inflammatory drugs (NSAIDS) or probenecid, both of which delay drug excretion potentially leading to toxicity especially with high methotrexate doses |
Coadministration of sulfonamides, trimethoprim, salicylates, tetracycline, chloramphenicol, and phenytoin can displace methotrexate from plasma protein and increase circulation plasma levels of methotrexate resulting in increased risk of toxicity |
Methotrexate: dosage and administration |
Dosage is 7.5–25 mg per week |
Oral, subcutaneous, intramuscular, intravenous route. Parenteral routes theoretically should reduce the risk of liver side effects and might achieve higher drug levels |
Folic acid 1 mg/day should be taken along with methotrexate to minimize side effects |
Often requires 3–6 months to take effect |
Methotrexate: side effects |
Gastrointestinal irritation is a common side effect |
Other side effects: hepatotoxicity, bone marrow suppression, secondary infection, and interstitial pneumonitis |
Relatively contraindicated in liver disease. Patients should restrict alcohol consumption |
Methotrexate was not found to have an increased incidence of overall mortality (adjusted hazard ratio: 1.02, 95 % CI 0.78–1.34) or cancer-related mortality (adjusted hazard ratio: 0.89, 95 % CI 0.48–1.63) in a large cohort of ocular inflammation patients [17] |
Methotrexate: pregnancy and lactation |
Teratogenic (used “off-label” to induce abortion). Pregnancy class X |
Increase risk of congenital anomalies [18] |
Conception should be avoided by both men and women for at least 3 months after the last dose of methotrexate [18] |
An effective birth control strategy should be advised |
Excreted into human milk in low concentrations. Because of the potential for serious adverse reactions in breast-fed infants, it is contraindicated |
Outcomes in Ocular Inflammation
Methotrexate has been shown to be effective for treatment of ocular inflammation in general [15] as well as specific ocular diseases such as mucous membrane pemphigoid [19], rheumatoid arthritis-associated scleritis and episcleritis [20], sympathetic ophthalmia [21], Vogt–Koyanagi–Harada disease [22], anterior and intermediate uveitis [23], sarcoidosis-related panuveitis [24], birdshot retinochoroidopathy [25, 26], optic neuropathy associated with sarcoidosis [27], and orbital inflammatory disease [28]. In addition, the efficacy of methotrexate in treatment of ocular inflammation has been reported by many small case series. The largest series reported outcomes of methotrexate used in 384 patients with uveitis and ocular inflammation as a single immunosuppressive agent. In a conservative analysis, it was found to be effective in control of ocular inflammation in 66 % of patients and have a corticosteroid-sparing success in 58 % of patients within 1 year [15]. Several additional patients were controlled to a minimal/“trace” level of activity. Samson et al. evaluated outcomes in 160 patients; control of inflammation was found in 76 % of patients and a corticosteroid-sparing response in 64 % [16]. Other smaller retrospective case series found inflammation reduction in 56–100 % of patients [23, 24, 29–32] and corticosteroid reduction in 50–100 % of patients [24, 29, 33]. Baker et al. studied retention time of conventional immunosuppressive agents; there was a twofold risk of not continuing treatment with azathioprine, mycophenolate mofetil, and cyclosporin and a fourfold risk of not being retained on cyclophosphamide compared with methotrexate, which had the best retention time among these agents [34]. This study suggested that methotrexate may have a superior combination of effectiveness and tolerability over other immunosuppressive drugs. Methotrexate treatment has been reported to reduce the number of flare-ups in patients with recurrent anterior uveitis from 3.4 to 0.89/year [35]. It has been shown to be effective in treatment of uveitis-associated juvenile idiopathic arthritis [36–39] and is widely accepted as the first-line immunosuppressive agent used in children because of the extensive experience of safety and tolerability in this setting [37, 40].
There are other approaches to use of methotrexate for treatment of ocular diseases locally including intravitreal and periocular injection. Intravitreal methotrexate has been used for treatment of intraocular B-cell lymphoma [41]. It can be used with success in treatment of ocular inflammation [42–45]and uveitic macular edema, and a moderate amount of data exist suggesting this approach may lead to long-term remission in a substantial number of cases [43, 44]. Subconjunctival methotrexate has been used for treatment of leukemic infiltration [46].
Azathioprine
Azathioprine, developed in 1960s, has been widely used for prevention of organ transplant rejection as well as for autoimmune diseases such as rheumatoid arthritis, psoriatic arthritis, reactive arthritis, SLE, and inflammatory bowel disease. It is a purine analog which is a prodrug of 6–mercaptopurine (6-MP). Chemically, azathioprine is 6-((1-methyl-4-nitroimidazole-5-yl)) purine with a molecular weight of 277.3 g/mol. It has similar structure to hypoxanthine which is an important precursor in purine metabolism (Table 9.4).
Table 9.4
Azathioprine
Azathioprine: pharmacology |
Converted to 6-mercaptopurine (6-MP) in the liver |
6-MP is metabolized in cells to thioinosinic and thioguanylic acid |
Thiopurine nucleotides interfere with de novo synthesis of purine nucleotides |
Inhibition of aminotransferase enzymes and purine ribonucleotide interconversion and incorporation into DNA and RNA results in inhibition of DNA replication and RNA transcription |
Immunologic actions: |
Inhibits T-lymphocyte functions |
Suppresses homing in circulating T cells |
Decreases development of monocyte precursors and participation of natural killer cells in the antibody-dependent cytotoxicity reaction |
Suppresses delayed-type hypersensitivity reaction (type IV) and both T-cell and B-cell activity |
Affects the afferent arm of immune response when given before antigenic challenge |
Decreases the number of peripheral T cell and B cells and reduces lymphocyte activity in interleukin-2 and IgM production |
Azathioprine: metabolism |
Metabolized in the liver to its metabolite (6-mercaptopurine) |
Xanthine oxidase and thiopurine methyltransferase (TPMT) metabolizes azathioprine into inactive form |
Xanthine oxidase catalyzes the formation of 6-thiouric acid, and approximately 10 % of azathioprine is cleaved to form 1-methyl-4-nitro-5 thioimidazole |
Thiopurine methyltransferase (TPMT) is the main enzyme inactivating the toxic metabolites |
TPMT activity exhibits genetic polymorphism (TPMT deficiency is about 0.3 % [47].); low levels of TPMT increase chance of severe drug toxicity. Therefore, genotype analysis of TPMT enzyme activity may be useful before starting azathioprine |
Allopurinol (an inhibitor of xanthine oxidase) is contraindicated |
Medications that inhibit or induce hepatic microsomal enzyme system such as ketoconazole, erythromycin, phenytoin, rifampin, and phenobarbital can affect its clearance, raising levels |
Use of angiotensin-converting enzyme inhibitors may be associated with severe leukopenia |
Azathioprine: dosage and administration |
1–3 mg/kg/day |
Oral and intravenous forms are available, 50 mg per tablets for oral administration |
Response occurs approximately 1–3 months after starting the therapy |
Azathioprine: side effects |
Tolerability: 24 % of ocular inflammation patients stopped azathioprine within 1 year due to side effects [48] |
Most common side effect is gastrointestinal discomfort |
Other reported adverse effects include bone marrow suppression, hepatotoxicity, interstitial pneumonitis, hepatocellular necrosis, pancreatitis, stomatitis, alopecia, and secondary infection |
Azathioprine was not found to increase the incidence of overall (adjusted hazard ratio = 0.99, 95 % CI 0.72–1.38) or cancer mortality (adjusted hazard ratio = 1.13, 95 % CI 0.60–2.14) in an ocular inflammation cohort [17] |
Azathioprine: pregnancy and lactation |
D classification for using in pregnancy [18] |
Avoid this medication in pregnant women; conception should be avoided until at least 12 weeks after discontinuation in male and female [18] |
Using this medication in breastfeeding women is not recommended |
Outcomes in Ocular Inflammation
Azathioprine has been used for treatment of noninfectious uveitis [49], sympathetic ophthalmia [50], Vogt–Koyanagi–Harada disease [51], iridocyclitis [52], Behçet disease [53–55], juvenile idiopathic arthritis [56], scleritis with relapsing polychondritis [57], mucous membrane pemphigoid [58], retinal vasculitis, [59] and serpiginous choroiditis [60, 61]. A 2-year double masked, randomized, controlled study patients with Behçet disease demonstrated that azathioprine reduced development of new eye disease and decrease occurrence of the second eye disease [53]. Moreover, the long-term follow-up of the clinical trial showed early use of azathioprine may benefit the long-term prognosis of patients with Behçet disease (with respect to placebo) [54]. Small retrospective studies have reported improvement of inflammation in 55–96 % of patients with chronic uveitis [49, 55, 62, 63]. Recently, data from the SITE Cohort Study retrospectively studied 145 patients with ocular inflammatory diseases who were treated with azathioprine. In this conservative analysis, azathioprine was found to be effective in control of ocular inflammation in 62 % of patients and to have corticosteroid-sparing success in 47 % of patients within 1 year with additional patient gain improvement to “trace” levels of inflammation [48].
Mycophenolate Mofetil
Mycophenolate mofetil is the two morpholinoethyl ester of mycophenolic acid, which is an inhibitor of inosine monophosphate dehydrogenase. Its molecular weight is 433.5 g/mol. It was first used as an immunosuppressant to treat psoriasis in 1975 [64]. After that it has been used widely to prevent organ rejection in renal transplant and also increasingly used for autoimmune disease. The effectiveness of mycophenolate mofetil for treatment of ocular inflammation was first described in 1999 [65] (Table 9.5).
Table 9.5
Mycophenolate mofetil
Mycophenolate mofetil: pharmacology |
Reversible inhibitor of inosine monophosphate dehydrogenase (IMPDH) |
Interferes with guanosine nucleotide synthesis, disrupting the de novo pathway of purine synthesis |
Immunological actions: |
Suppresses proliferation of T-cell and B-cell lymphocytes |
Suppresses antibody synthesis |
Interferes with cellular adhesion to vascular endothelium |
Inhibits recruitment of lymphocytes |
Decreases production of proinflammatory cytokines [66] |
Mycophenolate mofetil: drug metabolism |
Rapidly absorbed after oral administration, has high bioavailability |
97 % bound to plasma protein |
Converted by ester hydrolysis in the liver to an active drug, mycophenolic acid (MPA) |
Half-life is 16 h |
Metabolites are excreted in urine |
Antacids reduce the bioavailability by 15 % |
Acyclovir, ganciclovir, and mycophenolate metabolic product may compete for renal tubular secretion Cholestyramine decreases plasma levels by 40 % after administration |
Mycophenolate mofetil: dosage and administration |
1 g orally twice a day |
Total dose of 3 g per day or above may increase risk of toxicity |
Available in oral and IV forms |
Should be taken in an empty stomach (1 h before or 2 h after eating) |
Mycophenolate mofetil: side effects |
Tolerability: 12 % of patients discontinued mycophenolate mofetil within 1 year because of toxicity [67] |
Most common side effects are gastrointestinal symptoms: diarrhea, nausea, abdominal pain, vomiting, and bone marrow suppression |
Other reported adverse effects are secondary infection, impotence, anorexia, alopecia, and headache. Progressive multifocal leukoencephalopathy (PML) has been reported rarely [68] (not in ocular inflammation) and is included on the drug label |
Mycophenolate mofetil was not found to have a significant increase incidence of overall mortality (adjusted hazard ratio = 0.90 (95 % CI 0.48–1.68)) or cancer-related mortality (adjusted hazard ratio = 0.83 (0.20–3.52)) in a cohort of patients with ocular inflammation [17]. It is popular for prevention of transplant rejection in part because of a theoretical reduction in cancer risk |
Mycophenolate mofetil: pregnancy and lactation |
Associated with increased risk of pregnancy loss and congenital anomalies |
Should not be used in pregnancy, should be stopped at least 3 months before planned pregnancy [18] |
Effective birth control is mandatory during therapy |
Not recommended to use this medication while breastfeeding |
Outcomes in Ocular Inflammation
Mycophenolate mofetil has been used in chronic ocular inflammatory diseases, scleritis [69–71], uveitis in children [72], and mucous membrane pemphigoid [73, 74]. Eighty-two percent of the patients had treatment success in a retrospective study [75]. Other small retrospective studies found 77–91 % [65, 76, 77] of the patients had a favorable response, 65–71 % [65, 78, 79] of the patients had inflammation reduction, and 54–100 % [72, 76, 78, 79] of the patients had decreased corticosteroid use. A direct comparison of efficacy and side effects of methotrexate, azathioprine, and mycophenolate mofetil in 257 patients with active uveitis (anterior, intermediate, or posterior) or scleritis found the proportion of patients with treatment success after 6 months of treatment to be highest in the MMF group (70 %) [80]. Teoh and colleagues reported efficacy in 100 patients and showed 68.4 % and 84.6 % of the patients achieving corticosteroid-sparing success after 6 months and 1 year, respectively [81]. The largest retrospective review of efficacy of mycophenolate mofetil used in 236 patients found control of inflammation achieved 53 and 73 % within 6 months and 1 year and corticosteroid-sparing effects in 55 % of the patients in a conservative analysis with more patients achieving “trace” levels of inflammation [67].
Leflunomide
Leflunomide (Arava) is N(4′-trifluoromethylphenyl)-s-methylisoxazole-4-carboxamide which is a pyrimidine synthesis inhibitor. It is a prodrug and has molecular weight of 270.2 g/mol. It is FDA approved for treatment of rheumatoid arthritis [82, 83]. It has been reported to decrease ocular inflammation in sarcoidosis [84], juvenile idiopathic arthritis-associated uveitis [85, 86], and idiopathic orbital inflammation [87] (Table 9.6).
Table 9.5
Mycophenolate mofetil
Mycophenolate mofetil: pharmacology |
Reversible inhibitor of inosine monophosphate dehydrogenase (IMPDH) |
Interferes with guanosine nucleotide synthesis, disrupting the de novo pathway of purine synthesis |
Immunological actions: |
Suppresses proliferation of T-cell and B-cell lymphocytes |
Suppresses antibody synthesis |
Interferes with cellular adhesion to vascular endothelium |
Inhibits recruitment of lymphocytes |
Decreases production of proinflammatory cytokines [66] |
Mycophenolate mofetil: drug metabolism |
Rapidly absorbed after oral administration, has high bioavailability |
97 % bound to plasma protein |
Converted by ester hydrolysis in the liver to an active drug, mycophenolic acid (MPA) |
Half-life is 16 h |
Metabolites are excreted in urine |
Antacids reduce the bioavailability by 15 % |
Acyclovir, ganciclovir, and mycophenolate metabolic product may compete for renal tubular secretion Cholestyramine decreases plasma levels by 40 % after administration |
Mycophenolate mofetil: dosage and administration |
1 g orally twice a day |
Total dose of 3 g per day or above may increase risk of toxicity |
Available in oral and IV forms |
Should be taken in an empty stomach (1 h before or 2 h after eating) |
Mycophenolate mofetil: side effects |
Tolerability: 12 % of patients discontinued mycophenolate mofetil within 1 year because of toxicity [67] |
Most common side effects are gastrointestinal symptoms: diarrhea, nausea, abdominal pain, vomiting, and bone marrow suppression |
Other reported adverse effects are secondary infection, impotence, anorexia, alopecia, and headache. Progressive multifocal leukoencephalopathy (PML) has been reported rarely [68] (not in ocular inflammation) and is included on the drug label |
Mycophenolate mofetil was not found to have a significant increase incidence of overall mortality (adjusted hazard ratio = 0.90 (95 % CI 0.48–1.68)) or cancer-related mortality (adjusted hazard ratio = 0.83 (0.20–3.52)) in a cohort of patients with ocular inflammation [17]. It is popular for prevention of transplant rejection in part because of a theoretical reduction in cancer risk |
Mycophenolate mofetil: pregnancy and lactation |
Associated with increased risk of pregnancy loss and congenital anomalies |
Should not be used in pregnancy, should be stopped at least 3 months before planned pregnancy [18] |
Effective birth control is mandatory during therapy |
Not recommended to use this medication while breastfeeding |
Outcomes in Ocular Inflammation
Experience in the use of leflunomide for treatment of ocular inflammatory disease has been limited. Animal studies have shown leflunomide to be effective in inhibiting experimental autoimmune uveitis [89, 90] and in suppressing corneal allograft rejection in the rat [91]. Leflunomide was shown to decrease ocular inflammation in 23 of 28 patients (82 %) in patients with sarcoidosis [84]. Molina et al. studied efficacy of leflunomide in juvenile idiopathic arthritis-associated uveitis and found 61.5 % achieved and maintained an ocular response to the drug [86].
T-Cell Inhibitors
Cyclosporine
Cyclosporine is an 11-amino acid peptide derived from the fungus, Tolypocladium inflatum Gams (a fungal antimetabolite). Its primary use is in prevention of solid organ transplant rejection. Cyclosporine is FDA approved for graft rejection, rheumatoid arthritis, and psoriasis. It was first used for treatment of ocular inflammation in 1983 [92] (Table 9.7).
Table 9.7
Cyclosporine
Cyclosporine: pharmacology |
Forms a complex with cyclophilin |
The cyclosporine:cyclophilin complex binds to calcineurin, a calcium/calmodulin-dependent serine–threonine phosphatase, which inhibits translocation of a cytosolic nuclear factor of activated T cells (NFAT) to nucleus |
Disrupt the transcription of genes for T-cell activation as well as production of important cytokines for activation of T cells such as interleukin 2, interferon-γ, and tumor necrosis factor α |
Immunologic actions: |
Inhibits activation of T cells (mainly T-helper cells), natural killer cells, and antigen-presenting cells |
Reduces antibody production to T-cell-dependent antigens |
Inhibits T-cell cytotoxic activity |
Cyclosporine: metabolism |
Absorbed through the gastrointestinal system, absorption increases when taken with high-fat meals |
Half-life is 8 h |
Metabolized in the liver via cytochrome P-450 3A (CYP3A) system and excreted in bile |
Drugs that slow the rate of metabolism and affect microsomal enzymes, especially CYP3A, may have an impact on increasing cyclosporine blood concentrations, including Ca2+ channel blockers (verapamil, nicardipine), antifungal agents (fluconazole, ketoconazole), antibiotics (erythromycin), glucocorticoids (methylprednisolone), HIV-protease inhibitors (indinavir), and other drugs (allopurinol, metoclopramide) |
Grapefruit juice inhibits CYP3A and the P-glycoprotein multidrug efflux pump, intake should be minimized (increases cyclosporine blood concentrations) |
Drugs that induce CYP3A activity can increase cyclosporine metabolism and decrease blood concentrations: some antibiotics (nafcillin, rifampin) and anticonvulsants (phenobarbital, phenytoin), as well as other drugs (octreotide, ticlopidine) |
Cyclosporine: dosage and administration |
2–5 mg/kg/day divided twice daily |
Target serum cyclosporine level (trough level) is 150–250 mg/day, although most uses for ocular inflammation have not monitored trough levels routinely |
Oral and intravenous forms are available |
Two preparations, oil-based gelatin capsules (Sandimmune) and a microemulsion (Neoral); the latter has greater bioavailability and is more widely used. Generic preparations of both are available |
Available as 25 and 100-mg soft gelatin capsules and a 100-mg/mL oral solution |
Cyclosporine dosage should be reduced by 25–50 % if serum creatinine increases >30 % above baseline and should be discontinued if creatinine does not return to within 30 % of baseline levels within 1 month [93] |
Cyclosporine: side effects |
Tolerability: 10 % of patients with ocular inflammation had toxicity leading to discontinuation of therapy within 1 year; older adults over 55 years of age were substantially more likely to discontinue for toxicity [94] |
Renal toxicity and hypertension are the most common adverse effects (especially with higher doses (10 mg/kg/day)) |
Other side effects include gastrointestinal upset, hepatotoxicity, gum hyperplasia, tremor, paresthesia, hirsutism, hyperkalemia, hypomagnesemia, and hyperuricemia |
Cyclosporine was not significantly associated with an increased risk of overall (fully adjusted hazard ratio = 0.79, 95 % CI 0.57–1.10) or cancer mortality (fully adjusted hazard ratio = 0.82, 95 % CI 0.40–1.67) [17] |
Cyclosporine: pregnancy and lactation |
The drug can cross the placenta and is detected in amniotic fluid and fetal blood and is also present in breast milk [93] |
Cyclosporine is safer than antimetabolites in pregnancy [18] |
Breastfeeding potentially could be allowed if some drug delivery to infants was acceptable |
Outcomes in Ocular Inflammation
Cyclosporine has been reported to be effective in Behçet disease, Vogt–Koyanagi–Harada syndrome, birdshot retinochoroiditis, serpiginous choroiditis, multifocal choroiditis and panuveitis, and intermediate uveitis [98, 99]. Masuda et al. conducted a double-blinded study of 96 patients comparing cyclosporine to colchicine in the treatment of Behçet disease and demonstrated better outcomes with cyclosporine [100]. Nussenblatt and colleagues reported a randomized controlled trial demonstrating cyclosporine was effective in controlling inflammation in endogenous uveitis [101]. This group subsequently showed that cyclosporine used as monotherapy in corticosteroid-resistant patients was effective in decreasing inflammation [102]. The doses of cyclosporine used in early studies were high (8–10 mg/kg/day). However, low-dose therapy (2–5 mg/kg/day) also has been found to be effective and with fewer side effects compare to high-dose therapy [98, 103]. Vitale et al. found low-dose cyclosporine controlled inflammation in 74 % of the patients [104]. Mathews and associates also reported efficacy of low-dose cyclosporine and found intraocular inflammation was improved or stable in 97 % of patients [105]. Cyclosporine is well tolerated when used in children. An uncontrolled, retrospective study of 15 children with uveitis treated with cyclosporine reported that 82 % of those patients had an improvement or stabilization of visual acuity [106]. In the SITE Cohort Study report of 373 patients with noninfectious uveitis and ocular inflammation using cyclosporine as a single agent, 33.4 % achieved control of inflammation by 6 months and 51.9 % by 1 year [94]. Corticosteroid-sparing success was achieved by 22.1 % at 6 months and 36.1 % at 1 year [94]. Success was about 20 % higher if “trace” activity was considered a success.
Tacrolimus
Tacrolimus is macrolide antibiotic produced by Streptomyces tsukubaensis and is a 822 kDa molecule (C44H69NO12H2O). It inhibits activation of T lymphocytes. Tacrolimus is approved by FDA for prevention of liver transplant rejection and has been used to prevent rejection for many organ transplants such as heart, kidney, and small bowel transplant (Table 9.8).
Table 9.8
Tacrolimus
Tacrolimus: pharmacology |
Similar to cyclosporine, but 100 times more potent than cyclosporine |
Binds to FK-binding protein (an intracellular binding protein) instead of cyclophilin |
This inhibits translocation of cytosolic nuclear factor of activated T cells to nucleus, disrupting transcription of genes for T-cell activation and production of cytokines such as interleukin 2 |
Tacrolimus: metabolism |
Absorption of tacrolimus from gastrointestinal system is poor (variable from 4 to 93 %) |
Rate of absorption is limited when the drug is taken with food |
Half-life is 34.8 ± 11.4 h |
Serum concentrations peak in 0.5 to 2 h, decreasing to the basal level over 8–10 h |
99 % plasma protein binding |
Metabolized by cytochrome P-450 system; undergoes hepatic demethylation and hydroxylation |
Excreted in the bile [107] |
Tacrolimus: dosage and administration |
The initial dose is 0.05–0.15 mg per kg per day |
The trough drug level (between 15 and 25 mg/mL) seems to correlate better with clinical events [108] |
Monitoring for blood concentration is recommended because the absorption varies widely |
Available for oral administration as capsules (0.5, 1, and 5 mg) and as a solution for injection (5 mg/mL) |
Tacrolimus: side effects |
Other reported side effects: hyperglycemia, hypomagnesemia, tremor, headache, ophthalmoplegia, meningitis-like symptoms, insomnia, and paresthesias |
Tacrolimus: pregnancy and lactation |
Increase risk of abortion and congenital anomalies [113] |
Contraception should be recommended |
Excreted into human milk. Unknown effects in the nursing infant. However, breastfeeding should not be discouraged [114] and advise to mother should balance risks and benefits |
Outcomes in Ocular Inflammation
Tacrolimus has been shown to be effective for the treatment of noninfectious uveitis such as Behçet disease, Vogt–Koyanagi–Harada syndrome, and sympathetic ophthalmia [115]. A randomized trial of 37 patients studied the efficacy of tacrolimus in treatment of posterior segment intraocular inflammation, showing no significant differences between cyclosporine and tacrolimus in terms of improvement of ocular inflammation and visual acuity. The response rate, defined by an improvement in visual acuity of at least two lines in either eye or a decrease in binocular indirect ophthalmoscope (BIO) score to zero in either eye within 3 months of commencing treatment, occurred in 68 % of the patients taking tacrolimus [111]. Mochizuki et al. found the efficacy of tacrolimus in refractory uveitis to be 76.5 % at 12 weeks [108]. Lee et al. conducted a randomized controlled trial comparing tacrolimus and tacrolimus with corticosteroid and demonstrated the proportion of patients who tolerated treatment and maintained disease remission for 9 months was similar in both groups (monotherapy, 62.5 %; dual therapy, 68.4 %; P = 0.694) [116]. Sloper and colleague reported a case series of six patients refractory to cyclosporine; tacrolimus controlled inflammation in all patients [117]. Hogan and associates reported 85 % of 62 patients had corticosteroid-sparing success (prednisone taper to 10 mg daily) after 1 year and 2 months of treatment, 81 % probability of taking ≤5 mg daily, and a 61 % probability of discontinuing systemic corticosteroid therapy completely [118].
Alkylating Agents
Cyclophosphamide
Cyclophosphamide is 2-bis((2-chloroethyl)amino) tetrahydro-2H-1,3,2-oxazophosphorine 2-oxide monohydrate, a nitrogen mustard. It has molecular mass of 261.09 g/mol. It is approved by the FDA for childhood nephrotic syndrome and is used widely for treatment of severe systemic lupus erythematosus and other vasculitides such as granulomatosis with polyangiitis. In 1952, Roda-Perez first reports use of nitrogen mustard for treatment of uveitis [119]. Cyclophosphamide is especially widely used for treatment of systemic vasculitides with ocular involvement (Table 9.9).
Table 9.9
Cyclophosphamide