Next-generation calcineurin inhibitors for ophthalmic indications

Calcineurin inhibitors (CNIs) are potent immunosuppressants that reversibly inhibit T-cell proliferation and prevent the release of pro-inflammatory cytokines by blocking the activity of calcineurin, a ubiquitous enzyme that is found in cell cytoplasm. CNIs can be highly effective in immune-mediated ophthalmic diseases such as uveitis, dry eye syndrome and inflammatory blepharitis, as well as for the prevention of rejection in corneal transplants. ISA-247/LX-211 is a novel CNI that is in Phase III clinical development for the treatment of various forms of non-infectious uveitis. ISA-247/LX-211 is a rationally designed analog of ciclosporin A that exhibits more predictable pharmacokinetic and pharmacodynamic properties and a 4-fold greater calcineurin inhibition than its parent compound, ciclosporin A. ISA-247/LX-211 has been observed to be effective, well-tolerated, and safe in early clinical trials, exhibiting a much wider therapeutic window compared with classic CNIs, such as ciclosporin A and tacrolimus. An alternative approach to widening the therapeutic window for the therapy of ophthalmic disorders lies in local delivery of CNIs through polymeric implants that release the drug over long periods of time. The silicone matrix episcleral implant LX-201 is in Phase III development at present for the prevention of rejection in high-risk cornea transplantation.     

Tacrolimus: in heart transplant recipients

Tacrolimus is a calcineurin inhibitor recently approved in the US and throughout the EU for the prevention of allograft rejection in heart transplant recipients. It is commonly administered orally for long-term immunosuppression. The incidence of mild to severe acute rejection in the first 6 months following heart transplantation was significantly lower in tacrolimus recipients than in ciclosporin recipients (54% vs 66%) in a large, phase III trial conducted in Europe. A large, phase III trial conducted in the US did not show a significant difference between tacrolimus and ciclosporin in the incidence of severe rejection or haemodynamic compromise rejection requiring treatment within the first 6 months post-transplant (22% vs 32%), but did show a significant difference in the incidence at 1 year (23% vs 37%). In phase III trials, 1-year patient survival was similar between tacrolimus and ciclosporin recipients in the EU (93% vs 92%) and the US (95% vs 90%). Tacrolimus was shown to be effective in the prevention of rejection in paediatric and African American heart transplant recipients. The tolerability profile of tacrolimus in heart transplant recipients was broadly similar to that of ciclosporin, although tacrolimus was usually associated with lower incidences of post-transplant hypertension and dyslipidaemia.     

ISAtx-247 (Isotechnika/Roche)

ISAtx-247 is a ciclosporin A analog under development by Isotechnika and Roche as an immunosuppressant for the potential prevention of organ rejection after transplantation, and for the potential treatment of autoimmune diseases such as rheumatoid arthritis, psoriasis and type 1 diabetes. A phase II renal transplantation study had been completed by June 2003.     

Deciphering calcineurin inhibitor nephrotoxicity: a pharmacological approach

The calcineurin inhibitors ciclosporin and tacrolimus are used to prevent acute rejection of solid organs after transplantation. Their use can lead to chronic renal damage characterized by progressive and irreversible deterioration of renal function associated with interstitial fibrosis, tubular atrophy, arteriolar hyalinosis and glomerulosclerosis. Many approaches to better understand the mechanisms of this toxicity are in use. The aim of these approaches is to find biomarkers of early kidney injury and potential therapeutic targets. Despite these efforts, the biological processes leading to calcineurin inhibitor nephrotoxicity remain poorly understood. Furthermore, the diagnosis of chronic renal damage remains inaccurate without definitive diagnostic tools, no effective prevention exists and a therapy to treat the damage has yet to be developed. In this article, theories of pharmacodynamics, pharmacokinetics, therapeutic drug monitoring and pharmacogenetics are synthesized in ways that may improve the understanding of mechanisms leading to calcineurin inhibitor toxicity. The importance of global approaches such as toxicogenomics is emphasized to characterize early cellular responses implicated in calcineurin inhibitor nephrotoxicity.     

ISA 247: trans-ISA 247, trans-R 1524, ISA(TX)247, ISAtx 247, ISATx247, LX 211, LX211, R 1524, R-1524

Isotechnika is developing the immunosuppressive drug ISA 247, a calcineurin inhibitor that is undergoing clinical development for the treatment of psoriasis (phase III) and prevention of organ rejection after transplantation (phase II). Preclinical development for uveitis is also underway. Other autoimmune disease indications that could be explored include arthritis, type I diabetes and Crohn's disease. ISA 247 was being co-developed as R 1524 by Isotechnika and Roche. However, Roche is no longer involved in the development of this compound. Based on analysis of previously collected data, the trans-ISA 247 isomer was found to be more bioavailable and it is expected that this isomer can be administered at a lower dose compared with the previous formulation that consisted of an equivalent mixture of the two geometric isomers (cis and trans). Preclinical observations indicate that ISA 247 has the potential to be more potent and less toxic than other marketed immunosuppressants in its class used for the prevention of transplant rejection. Experiments to date suggest that ISA 247 is about three times as potent as ciclosporin, while genotoxicity studies in animals have shown that the compound has a significantly reduced tendency to cause renal toxicity. The combination of reduced toxicity and improved potency would give ISA 247 a therapeutic benefit over existing calcineurin-based treatments. Isotechnika and Roche entered into a co-development and commercialisation agreement in April 2002, with Roche gaining the exclusive worldwide marketing rights for ISA 247; Isotechnika received milestone payments of $US4 million and $CAN21.9 million in September 2002 and May 2003, respectively. The agreement was restructured in April 2004, under which Isotechnika will now solely manage and fund the clinical development of trans-ISA 247. Upon successful completion of these trials, Isotechnika will conduct at its own expense a phase IIb study in renal transplantation and phase III studies in psoriasis. Roche will have the right to opt-in to the development and commercialisation of trans-ISA 247 for transplant indications up to the end of the phase IIb renal transplantation trial. Isotechnika retains all rights to develop and commercialise the product outside of transplant indications. Under an agreement signed with Cellgate Inc. on 25 April 2006, Isotechnika has the option to obtain an exclusive licence to develop and commercialise conjugates consisting of Cellgate's patented transporter technology, for the topical delivery of ISA 247 in patients with mild-to-moderate psoriasis. Cellgate will perform studies to evaluate the feasibility of using their technology to topically deliver ISA 247. In return, Isotechnika will pay Cellgate Inc. a total of $US500 000, with $US100 000 paid upfront, and the remainder at predetermined time points. Upon successful completion of the studies, Isotechnika has the option to further develop and commercialise conjugates for topical delivery of ISA 247. Isotechnika and Atrium Medical Corporation announced an exclusive worldwide licensing agreement for ISA 247 alone and in combination with TAFA 93 with respect to drug-eluting devices, in September 2005. Atrium's implantable products include those for the local, non-systemic treatment of vascular and cardiovascular disorders, soft tissue repair and other disorders. In May 2006, Isotechnika licensed ISA 247 to Lux Biosciences for ophthalmic indications. Under terms of the agreement, Lux Biosciences obtains the exclusive worldwide marketing rights to ISA 247 for treatment and prophylaxis of all ophthalmic indications. The company will be responsible for development, registration and marketing of the drug for ophthalmic indications and will make upfront and milestone payments to Isotechnika in addition to royalties on any sales. Isotechnika formalised a manufacturing agreement with Swiss-based Lonza Ltd in June 2004. Under the terms of the agreement, Lonza will manufacture sufficient quantities of trans-ISA 247 in a GMP environment for use in the company's upcoming clinical trials. Isotechnika completed the phase III SPIRIT trial of ISA 247 for psoriasis in Canada. The randomised, double-blind trial compared the efficacy of three doses of ISA 247 (0.2 mg/kg [low dose], 0.3 mg/kg [mid dose] and 0.4 mg/kg [high dose] twice daily) with placebo, with equal numbers of patients assigned to each of the four groups. Subsequent to the first 12 weeks, those patients who received placebo moved into the mid-dose group for the remaining 12 weeks of the study. Patients already receiving ISA 247 remained in their respective dosing groups for the final 12 weeks of the trial. Patients completing the 24-week SPIRIT trial were given the opportunity to continue therapy for an addditonal 36 weeks or to discontinue therapy. Those patients who chose to enrol in the extension trial were moved from the 0.2 mg/kg bid (low-dose) or 0.4 mg/kg bid (high-dose) groups into the the 0.3 bid mg/kg bid (mid dose) group. Patients who commenced the SPIRIT trial in the mid-dose group remained on the same dosage regimen for the duration of the extension trial. The goal of the extension trial is to demonstrate continued therapeutic benefit to psoriasis patients while gathering long-term safety data. So far, data has been received on 193 patients receiving treatment for a total of 48 weeks. A phase IIa trial investigating the safety and efficacy of ISA 247 in renal transplantation was completed in the US and Canada in January 2003. The trial compared ISA 247 with ciclosporin (Neoral in approximately 130 stable renal transplant patients who underwent transplantation at least 6 months prior to enrolment; patient recruitment was completed in October 2002. Half of the patients were treated with ciclosporin and the other half received ISA 247 over a 90-day period. An extension trial was then initiated in which another 200 patients were treated with ISA 247 for up to 6 months from the time of transplantation. Results from the trial were reported. All endpoints were achieved in a multiple ascending dose study of trans-ISA 247 in November 2004. The study, initiated in June 2004, was conducted by SFBC Anapharm in Montreal, Canada and involved 43 healthy volunteers. Final dosing recommendations are to be determined in phase III trials in patients with psoriasis. Interim results reported in September 2004, of a double-blind, parallel-group, placebo and moxifloxacin controlled, randomised single-dose QTc trial in healthy volunteers, showed no evidence of QTc prolongation when trans-ISA 247 was administered at therapeutic doses. A single ascending dose (SAD) trial for trans-ISA 247 was completed in July 2004. The SAD trial was conducted among healthy volunteers to assess the appropriate dosage of trans-ISA 247 for further clinical evaluations. The trial commenced in March 2004 with approximately 46 subjects enrolled under the supervision of MDS Pharma Services in Phoenix, Arizona, USA. Isotechnika received US FDA approval for the SAD trial in February 2004. A European patent (No. EP 0 991 660) entitled 'Deuterated and Undeuterated Cyclosporine Analgoues and Their Use as Immunomodulating Agents' was issued to Isotechnika for ISA 247, in October 2006. A US patent entitled 'Novel Cyclosporin Analogue Formulations' was issued to Isotechnika (No. 7 060 672) for ISA 247 in June 2006. The patent claims have been filed in 36 countries, and in the US it is the first patent to be issued in this patent family. Isotechnika was issued a US patent (No. 6 998 385, entitled 'Cyclosporine Analogue Mixtures and their use as Immunomodulating Agents') in February 2006 covering mixtures of cis- and trans- isomers of ISA 257. This patent is the first US patent to be issued in this family of patents. These patent claims have been filed in 36 countries. Three patents relating to this claim were previously issued in the following countries; Morocco (No. 26337 issued 1 October 2004); Pakistan (No. 138338 issued 30 September 2004) and South Africa (No. 2004/2270 issued 25 May 2005). A US patent (No 6 686 454) was issued in February 2004 entitled 'Antibodies to Specific Regions of Cyclosporine Related Compounds'. This patent covers a novel, simple and cost-effective assay used in the use and management of ISA 247. It also received another US patent entitled 'Deuterated Cyclosporine Analogs and their Use as Immunomodulating Agents'. Isotechnika has received patents for chemical composition of ISA 247 in New Zealand (November 2001; New Zealand Patent No. 502362), Canada (December 2001; Canadian Patent No. 2 298 572), South Korea (June 2006; South Korean Patent No. 585348) and Australia (November 2002; Australian Patent No. 750245). In addition, Isotechnika announced in August 2003 that it had been granted US patent No. 6 605 593, entitled 'Deuterated Ciclosporine Analogs and their use as Immunomodulating Agents'. An additional US patent covering ISA 247 was granted in September 2003.     

Therapeutic monitoring of immunosuppressive drugs: interest of calcineurin activity assessment in liver transplantation

Therapeutic monitoring of calcineurin inhibitors (ciclosporin and tacrolimus) consists in pharmacokinetic monitoring. Pharmacodynamics based on calcineurin activity may be particularly interesting in liver transplantation due to the large intra- and interindividual variability of pharmacokinetics of ciclosporin and tacrolimus. A recent investigation on the pharmacokinetic-pharmacodynamic relationship of tacrolimus showed that monitoring of calcineurin activity in PBMC may be particularly relevant within the first three post-transplantation months. Thereafter, the monitoring of trough blood concentrations of tacrolimus remains adequate. Moreover, two clinical investigations carried out within the early and late post-transplantation periods reported a promising result which is a positive correlation between calcineurin activity and incidence of graft rejection, whatever graft type and calcineurin inhibitors. In each study, transplanted recipients with a graft rejection exhibited a greater trough calcineurin activity compared to patients without graft rejection. However, prospective investigations are required because of the small cohorts of patients enrolled in both studies. The aim of these investigations will be to confirm the interest of calcineurin activity monitoring as a marker of cellular immunity and its positive link with pharmacokinetic monitoring.     

Belatacept

Immunosuppressive therapy designed to prevent kidney graft rejection usually consists of a triple-drug combination including a corticosteroid, a calcineurin inhibitor (ciclosporin or tacrolimus) and a drug that inhibits cell proliferation (azathioprine or mycophenolate mofetil). Belatacept is closely related to abatacept, an immunosuppressant marketed for rheumatic diseases. It is now authorised in the European Union for the prevention of kidney graft rejection, as a replacement for the calcineurin inhibitor. Two randomised controlled trials compared belatacept (2 doses) versus ciclosporin as part of the immunosuppressive regimen in respectively 666 and 534 patients. After 3 years of follow-up, survival with a functioning graft did not differ between the groups (about 80% in the trial closest to European protocols). Only the use of a high dose of belatacept instead of ciclosporin resulted in better preservation of renal function, but this is not the authorised dose. Lymphomas, particularly those affecting the central nervous system, were more frequent with belatacept in both trials (1.4% versus 0.9%). The risk was particularly high in patients receiving the high dose of belatacept, and in patients who were seronegative for Epstein-Barr virus. Overall, the risk of infections seems to be similar with belatacept and ciclosporin, but certain severe infections were more frequent with belatacept, including progressive multifocal leukoencephalopathy and tuberculosis. Unlike ciclosporin, belatacept plasma concentrations do not need to be monitored. However, intravenous belatacept administration is less convenient than oral ciclosporin administration, especially during long-term treatment. Overall, it is better to continue to use ciclosporin, a better-documented drug, as part of immunosuppressive therapy after kidney transplantation.     

Ciclosporin use in dry eye disease patients

Background: Dry eye disease is one of the most commonly encountered conditions in eye care, and inflammation is a frequent finding. Ciclosporin has long been used systemically to decrease the deleterious effects of inflammation. Ciclosporin is a calcineurin inhibitor that acts by primarily blocking the action of T cells, decreasing the release of pro-inflammatory cytokines, and preventing the apoptosis of goblet cells. Objective: This article reviews the clinical trials and safety profile of an ophthalmic preparation of ciclosporin in the treatment of dry eye. Results/conclusion: Clinical trials have demonstrated that ciclosporin minimizes the signs and symptoms of dry eye disease and is not associated with any significant systemic or ocular adverse reaction.     

Benefit-risk assessment of ciclosporin withdrawal in renal transplant recipients.

Ciclosporin is associated with significant toxicity, including nephrotoxicity, and with an increased risk of cardiovascular events. Many attempts have been made to wean patients from ciclosporin. Before the availability of new immunosuppressive drugs, the acute rejection rate observed after ciclosporin withdrawal did not permit the widespread use of withdrawal regimens even though meta-analysis did not show that they adversely affected patient or graft survival. Nevertheless, maintenance therapy with azathioprine and corticosteroids has not become routine practice. The introduction of mycophenolate mofetil and subsequently sirolimus has increased the number of clinical studies of the effects of ciclosporin withdrawal. In stable patients, this withdrawal is associated with a small but significant increase in the incidence of acute rejection episodes. Declining renal function and other forms of ciclosporin-related toxicity have improved. However, this improvement was also observed when ciclosporin was only reduced (and not withdrawn), which did not increase the risk of acute rejection. More precise definition of the patients who could benefit from ciclosporin-withdrawal may help to optimise the immunosuppressive regimen in this setting. In patients with chronic allograft deterioration, ciclosporin withdrawal together with mycophenolate mofetil introduction has been shown to improve renal function significantly in many small studies, and a large prospective randomised study. For the time being, ciclosporin withdrawal is a good therapeutic option for patients with declining renal function and signs of chronic ciclosporin nephrotoxicity on renal biopsy. Finally, recent preliminary studies have reported the results of complete avoidance of calcineurin inhibitors after renal transplantation. These results are promising as regards the incidence of acute rejection, renal function and safety, but need confirmation in larger trials with a longer follow-up. Nevertheless, it has become clear that the concept of an immunosuppressive regimen with little or no nephrotoxicity after renal transplantation is more and more important and plays a crucial part in tailoring immunosuppression to the needs of specific patient populations.     

钙调磷酸酶抑制剂环孢素A和他克莫司药效的监测方法进展

目前临床常用血药浓度来监测移植术后患者钙调神经磷酸酶抑制剂（CNIs）环孢素A和他克莫司的药效，但由于CNIs 的药动学及药效学个体差异大，仍需更有效的方法来监测其生物学效应。CNIs 药效的测定方法可分为非特异性测定和特异性测定。常见的非特异性药效靶标有：T细胞增殖水平、T细胞表面抗原、T细胞亚群、CD4+中ATP水平、抗HLA抗体以及可溶性CD30等。CNIs药效通路上其主要的特异性药效参数包括：CaN活性、NFAT核转位、细胞因子释放和细胞因子基因表达等。这些不同水平上的生物靶标仍需更多的前瞻性介入研究来验证。在未来，有望通过这些生物靶标，监测CNIs的免疫抑制效果，优化CNIs个体化给药。     

Clinical implementation of pharmacogenetics in kidney transplantation: calcineurin inhibitors in the starting blocks

Pharmacogenetics has generated many expectations for its potential to individualize therapy proactively and improve medical care. However, despite the huge amount of reported genetic associations with either pharmacokinetics or pharmacodynamics of drugs, the translation into patient care is still slow. In fact, strong evidence for a substantial clinical benefit of pharmacogenetic testing is still limited, with a few exceptions. In kidney transplantation, established pharmacogenetic discoveries are being investigated for application in the clinic to improve efficacy and to limit toxicity associated with the use of immunosuppressive drugs, especially the frequently used calcineurin inhibitors (CNIs) tacrolimus and ciclosporin. The purpose of the present review is to picture the current status of CNI pharmacogenetics and to discuss the most promising leads that have been followed so far.     

The pharmacological mechanism underlying the apoptosis of human hepatic stellate cells LX-2 induced by NF-κB inhibitor PDTC

In the present study, we aimed to confirm whether NF-κB inhibitor pyrrolidine dithiocarbamate (PDTC) could induce apoptosis of human hepatic stellate cells (HSCs) LX-2 and explore the potential pharmacological mechanism underlying these effects. In this study, LX-2 cells were cultured in vitro, and the experiment was divided into two groups, including the control and PDTC groups. The viability of LX-2 cells was measured by CCK8 assay after the cells were exposed to PDTC. The anti-apoptotic effect of PDTC was detected by AO/EB double assay staining kit. Additionally, the activities of NF-κB, Fas/FasL, apoptosis-related proteins, as well as the cellular localization of AIF, were determined by Western blotting analysis and immunofluorescence staining respectively. After PDTC treatment for 12 and 24 h, AO/EB dual staining showed typical apoptotic changes, such as cell volume reduction, cell shrinkage, nuclear fragmentation, and so on. PDTC at 60 μmol/L significantly increased the proliferation inhibition rate and decreased the secretion of collagen I, collagen III, and α-SMA in LX-2 cells. The Western blotting analysis and RT-PCR showed no significant difference in the expression of AIF between the control group and PDTC group, and the expressions of Fas and FasL were not observed in all groups (P > 0.05). Further results showed that PDTC could promote the displacement of AIF from mitochondria to the nucleus, activate the apoptotic signaling in the cell nucleus, and possibly participate in the apoptosis process of LX-2 cells. In conclusion, the pharmacological mechanism of PDTC against hepatic fibrosis might be to promote the displacement of AIF from mitochondria to the nucleus, then activate the apoptotic signaling in the cell nucleus, and finally induce the apoptosis of LX-2 cells. Meanwhile, these results also revealed that the Fas/FasL-mediated apoptosis pathway was not involved in the PDTC-induced apoptosis process of LX-2 cells.     

Calcineurin inhibitor-free immunosuppression in pediatric renal transplantation: a viable option?

The introduction, in the mid-1980s, of calcineurin inhibitors - namely ciclosporin (cyclosporine) and later tacrolimus - has significantly improved short-term renal graft survival by lowering acute rejection rates in both adult and pediatric kidney transplantation. Nonetheless, long-term transplant survival is still not satisfactory, with calcineurin inhibitor-induced chronic nephrotoxicity being one of the main causes of progressive nephron loss and declining renal transplant function. Hence, different immunosuppressant regimens have been proposed to avoid or ameliorate calcineurin inhibitor-induced nephrotoxicity. These comprise the use of non-depleting or depleting antibodies for calcineurin inhibitor minimization, calcineurin inhibitor avoidance, or calcineurin inhibitor withdrawal from mycophenolate mofetil-based immunosuppressant protocols. De novo use of a mammalian target of rapamycin (mTOR) inhibitor (sirolimus or everolimus) or conversion from a calcineurin inhibitor to an mTOR inhibitor may constitute another therapeutic option to avoid or reduce calcineurin inhibitor-induced nephrotoxicity. To date, complete calcineurin inhibitor avoidance seems to be inappropriate because other relatively potent immunosuppressant agents such as lymphocyte-depleting antibodies are needed for rejection prophylaxis, which are frequently accompanied by a higher incidence of infections and an unacceptably high acute rejection rate under calcineurin inhibitor avoidance. In some studies, calcineurin inhibitor withdrawal in adult and pediatric kidney allograft recipients with stable or declining transplant function has been associated with an amelioration of renal function; however, this is attained at the cost of a higher acute rejection rate in 10-20% of patients. It has been frequently stressed that conversion from a calcineurin inhibitor-based regimen to an mTOR inhibitor-based immunosuppressant regimen should be performed early (e.g. 3 or 6 months post-transplant) in patients with well-preserved renal transplant function without significant proteinuria in order to prevent, or at least limit, calcineurin inhibitor-induced tissue damage and provide long-term benefit. It should be borne in mind though that the use of an mTOR inhibitor carries the risk of potential adverse events such as aggravation of proteinuria, hyperlipidemia, myelosuppression, and hypergonadotropic hypogonadism. Even though everolimus may be better tolerated than sirolimus, studies on everolimus for calcineurin inhibitor-free immunosuppression in the pediatric kidney transplant patient population are lacking. At present, the safest therapeutic strategy for pediatric renal allograft recipients with chronic calcineurin inhibitor-induced nephrotoxicity appears to be a mycophenolate mofetil-based regimen with low-dose calcineurin inhibitor therapy and corticosteroids; available published data show that dual immunosuppression with mycophenolate mofetil and corticosteroids, as well as an mTOR inhibitor plus mycophenolate mofetil plus corticosteroid-based regimens, are associated with an increased risk of acute rejection episodes. In individual patients with evidenced chronic allograft dysfunction and over-immunosuppression leading to recurrent infections, dual maintenance immunosuppression with mycophenolate mofetil and corticosteroids may be appropriate. As stated in the annual report issued by the North American Pediatric Renal Trials and Collaborative Studies (NAPRTCS) Registry, currently the most popular immunosuppressant protocol consists of a calcineurin inhibitor combined with mycophenolate mofetil and corticosteroids: 59.1% and 53.2% of patients with a functioning graft receive a calcineurin inhibitor plus mycophenolate mofetil plus corticosteroid-based immunosuppression at 1 and 5 years post-transplant, respectively. 91.4% and 87.8% of patients are administered a calcineurin inhibitor-containing regimen 1 and/or 5 years after transplantation, respectively. Undoubtedly, the use of calcineurin inhibitor-free immunosuppressant regimens with or without antibody induction, plus an mTOR inhibitor and mycophenolate mofetil, requires more comprehensive long-term investigations to determine whether acceptable rejection rates and conservation of renal function can be achieved.     

Uses and safety profile of ciclosporin in ophthalmology

Ciclosporin is a calcineurin inhibitor that acts by primarily inhibiting the action of T cells. Clinical trials in the early 1980s demonstrated that systemic ciclosporin was a promising steroid-sparing agent and was also effective in patients who are refractory to treatment with corticosteroids. However, recent years have witnessed the emergence of safer immunosuppressive agents due to the poor side-effect profile of systemic ciclosporin. Topical ciclosporin, however, has a much improved safety profile and is still used to treat a variety of ocular surface disorders including dry eye syndrome, vernal and atopic keratoconjunctivitis, severe blepharitis and high-risk corneal graft patients. This article reviews the uses and safety profile of systemic and topical ciclosporin in ophthalmology, as well as discussing alternative therapeutic agents available.     

环孢素A眼用制剂的研究近况

环孢素A(cyclosporin A,CyA)为新一代强效免疫抑制剂,目前已应用于眼科临床。临床研究证实,CyA在治疗干眼症、葡萄膜炎、巩膜炎、春季过敏性结膜炎、角膜移植排斥反应等眼部疾病方面具有显著的疗效。综述CyA眼用制剂的研究现状,包括滴眼液、凝胶等常规眼用制剂,以及乳剂、微球、纳米粒等新型眼用制剂的特点和应用,以期为进一步开发高效、低毒、稳定、方便的新型CyA眼用制剂提供参考。     

Immunosuppression for long-term maintenance of renal allograft function

The incidence and severity of acute rejection episodes was markedly reduced by the introduction of new immunosuppressive drug regimens for renal transplantation, resulting in improved graft survival at 1 year. However, only modest improvement has been shown in long-term graft function rates.This overview evaluates the efficacy of currently used immunosuppressive drugs and drug combinations for long-term maintenance therapy. Prospective controlled trials rarely extend beyond 5 years; therefore, registry data and retrospective reports have also been employed. From currently available data it may be concluded that the initial beneficial effect of ciclosporin (cyclosporin) is lost 10 years after transplantation. Tacrolimus is an alternative to ciclosporin with a different profile of adverse effects and a higher efficacy in acute rejection treatment. For long-term maintenance, projected half-lives of kidney graft function are in favour of tacrolimus. Mycophenolate mofetil (MMF) has been shown to significantly reduce the incidence of early rejections. However, the improved long-term graft survival reported in retrospective studies has still to be confirmed in controlled trials. There is no convincing evidence for superiority of triple therapy including prednisone (or prednisolone), calcineurin inhibitors and azathioprine/MMF over dual therapy without azathioprine/MMF with respect to long-term outcome. Withdrawal of corticosteroids or calcineurin inhibitors clearly reduces adverse drug effects but carries the risk of acute rejection episodes. Avoidance of corticosteroids by using new immunosuppressive drug combinations may be an option to minimise toxic adverse effects in the future.At present, it seems unjustified to convert renal transplant recipients with stable graft function and tolerable adverse effects from one drug to another solely in expectation of future benefits. Acute early or late rejection episodes and intolerable adverse effects are good reasons for conversions between calcineurin inhibitors or cytotoxic agents. Chronic allograft nephropathy with slowly deteriorating graft function remains an unresolved problem.     

Calcineurin inhibitor sparing in paediatric solid organ transplantation : managing the efficacy/toxicity conundrum

Despite their efficacy, the calcineurin inhibitors (CNIs) ciclosporin and tacrolimus carry a risk of debilitating adverse effects, especially nephrotoxicity, that affect the long-term outcome and survival of children who are given organ transplants. Simple reduction in dosage of CNI has little or no long-term benefit on their adverse effects, and complete withdrawal without threatening graft outcome may only be possible after liver transplantation. Until the last decade, the only option was to increase corticosteroid and/or azathioprine doses, which imposed additional long-term hazards. Considered here are the emerging generation of new agents offering an opportunity for improving long-term graft survival, minimizing CNI-related adverse events and ensuring patient well-being.A holistic, multifaceted strategy may need to be considered - initial selection and optimized use and monitoring of immunosuppressant regimens, early recognition of indicators of patient and graft dysfunction, and, where applicable, early introduction of CNI-sparing regimens facilitating CNI withdrawal. The evidence reviewed here supports these approaches but remains far from definitive in paediatric solid organ transplantation. Because de novo immunosuppression uses CNI in more than 93% of patients, reduction of CNI-related adverse effects has focused on CNI sparing or withdrawal.A recurring theme where sirolimus and mycophenolate mofetil have been used for this purpose is the importance of their early introduction to limit CNI damage and provide long-term benefit: for example, long-term renal function critically reflects that at 1 year post-transplant. While mycophenolic acid shows advantages over sirolimus in preserving renal function because the latter is associated with proteinuria, sirolimus appears the more potent immunosuppressant but also impairs early wound healing. The use of CNI-free immunosuppressant regimens with depleting or non-depleting antibodies plus sirolimus and mycophenolic acid needs much wider investigation to achieve acceptable rejection rates and conserve renal function.The adverse effects of the alternative immunosuppressants, particularly the dyslipidaemia associated with sirolimus, needs to be minimized to avoid replacing one set of adverse effects (from CNIs) with another. While we can only conjecture that judicious combinations with the second generation of novel immunosuppressants currently in development will provide these solutions, a rationale of low-dose therapy with multiple immunosuppressants acting by complementary mechanisms seems to hold the promise for efficacy with minimal toxicity until the vision of tolerance achieves reality.     

Pharmacodynamic monitoring of calcineurin phosphatase activity in transplant patients treated with calcineurin inhibitors

Calcineurin inhibitors, tacrolimus and cyclosporine, have been widely used to prevent the rejection or graft-versus-host disease after transplantations. Since these drugs have a narrow therapeutic range and show large inter- and intraindividual pharmacokinetic variability, frequent therapeutic drug monitoring is required to control their blood concentrations. Even with blood concentrations within the therapeutic range, some patients still experience acute rejection or infections. Tacrolimus and cyclosporine form a complex with their respective binding proteins, immunophilins, which in turn inhibit the phosphatase activity of calcineurin, a key enzyme in the activation of T lymphocytes. Pharmacodynamic assessment of calcineurin phosphatase activity in combination with the monitoring of blood concentrations has been studied. The inhibitory effects on calcineurin activity in peripheral blood mononuclear cells differed between tacrolimus and cyclosporine in transplant patients. The pharmacodynamics of both drugs shows great inter- as well as intraindividual variation, and acute rejection was associated with calcineurin activity. Calcineurin activity at trough time points was suggested as a single surrogate predictor for overall calcineurin activity throughout dosing periods. Monitoring of calcineurin phosphatase activity might be useful to determine the therapeutic range of tacrolimus and cyclosporine concentrations for an individual patient treated with a calcineurin inhibitor.