Role of siroliumus, a novel immunosuppressive drug in heart and lung transplantation

The change of immunosuppressive regimen from calcineurin inhibitors to mammalian target of rapamycin (mTOR) inhibitors and its effect on malignancy following heart transplantation

Malignancy is a significant cause of mortality after organ transplantation. There is an increased rate of malignancy following heart transplantation (HTx) compared to the general population and other organ transplant recipients. Post-HTx patients with a history of malignancy are also at a higher risk of developing new malignancies or exacerbation of their existing malignancies. Mammalian target of Rapamycin inhibitors (mTORIs) are newly introduced immunosuppressive drugs with a unique mechanism of action. By changing the immunosuppressive regimen from classic drugs, especially calcineurin inhibitors (CNIs) to mTORIs, the rate of developing de novo malignancies and the relapse of former malignancies is significantly reduced. However, issues like allograft function, total surveillance of patients, and post-transplantation complications should be considered during the conversion of drug regimens utilizing CNIs to drug regimens employing mTORIs. We reviewed different post-heart transplant maintenance immunosuppressive regimens and their effect on post-HTx malignancies with a focus on mTORIs, compared safety against effectiveness, and gathered conclusions based on our review of the literature, which may lead clinicians to make a better evidence-based decision regarding post-HTx maintenance immunosuppressive drug regimens. Overall, CNI to mTORI conversion in post-HTx maintenance immunosuppressive drug regimens was associated with a reduced rate of developing malignancy in post-HTx patients. Furthermore, nephrotoxicity decreased significantly while using mTORIs in combination with lower doses of CNIs and the rejection rate was equivalent to CNI-only regimens. In conclusion, mTORI-based maintenance immunosuppressive drug regimens seem to be safe and beneficial when considering efficacy vs. adverse effects, and all-cause mortality rates are significantly lower in patients switched to mTORIs when compared to CNI recipients.

Targeting the PI3K/AKT/mTOR signaling axis in children with hematologic malignancies

The phosphatidylinositiol 3-kinase (PI3K), AKT, mammalian target of rapamycin (mTOR) signaling pathway (PI3K/AKT/mTOR) is frequently dysregulated in disorders of cell growth and survival, including a number of pediatric hematologic malignancies. The pathway can be abnormally activated in childhood acute lymphoblastic leukemia (ALL), acute myelogenous leukemia (AML), and chronic myelogenous leukemia (CML), as well as in some pediatric lymphomas and lymphoproliferative disorders. Most commonly, this abnormal activation occurs as a consequence of constitutive activation of AKT, providing a compelling rationale to target this pathway in many of these conditions. A variety of agents, beginning with the rapamycin analogue (rapalog) sirolimus, have been used successfully to target this pathway in a number of pediatric hematologic malignancies. Rapalogs demonstrate significant preclinical activity against ALL, which has led to a number of clinical trials. Moreover, rapalogs can synergize with a number of conventional cytotoxic agents and overcome pathways of chemotherapeutic resistance for drugs commonly used in ALL treatment, including methotrexate and corticosteroids. Based on preclinical data, rapalogs are also being studied in AML, CML, and non-Hodgkin's lymphoma. Recently, significant progress has been made using rapalogs to treat pre-malignant lymphoproliferative disorders, including the autoimmune lymphoproliferative syndrome (ALPS); complete remissions in children with otherwise therapy-resistant disease have been seen. Rapalogs only block one component of the pathway (mTORC1), and newer agents are under preclinical and clinical development that can target different and often multiple protein kinases in the PI3K/AKT/mTOR pathway. Most of these agents have been tolerated in early-phase clinical trials. A number of PI3K inhibitors are under investigation. Of note, most of these also target other protein kinases. Newer agents are under development that target both mTORC1 and mTORC2, mTORC1 and PI3K, and the triad of PI3K, mTORC1, and mTORC2. Preclinical data suggest these dual- and multi-kinase inhibitors are more potent than rapalogs against many of the aforementioned hematologic malignancies. Two classes of AKT inhibitors are under development, the alkyl-lysophospholipids (APLs) and small molecule AKT inhibitors. Both classes have agents currently in clinical trials. A number of drugs are in development that target other components of the pathway, including eukaryotic translation initiation factor (eIF) 4E (eIF4E) and phosphoinositide-dependent protein kinase 1 (PDK1). Finally, a number of other key signaling pathways interact with PI3K/AKT/mTOR, including Notch, MNK, Syk, MAPK, and aurora kinase. These alternative pathways are being targeted alone and in combination with PI3K/AKT/mTOR inhibitors with promising preclinical results in pediatric hematologic malignancies. This review provides a comprehensive overview of the abnormalities in the PI3K/AKT/mTOR signaling pathway in pediatric hematologic malignancies, the agents that are used to target this pathway, and the results of preclinical and clinical trials, using those agents in childhood hematologic cancers.

The first year post-heart transplantation: use of immunosuppressive drugs and early complications

A large number of heart transplants are performed annually in different transplant centers in the United States. This is partly because of the improved survival of patients who undergo cardiac transplantation, thus making it a more viable option in the management of end-stage heart failure. The survival benefit after heart transplantation is a result of newer immunosuppressive drug regimens and a better understanding of their effects and interactions. Several studies, mostly involving a small number of patients, describe use and comparison of the many distinct immunosuppressive drugs available to date. Interestingly, many transplant centers perform in-house typical induction treatment regimens because of their own experience and intra-institutional preference. This review summarizes current practices of immunosuppressive drug therapy in the first year post-heart transplant based on the available clinical evidence and discusses future options of heart transplant immunosuppressive drug therapies.

Comparison of sirolimus and everolimus in their effects on blood lipid profiles and haematological parameters in heart transplant recipients

The mTOR (mammalian target of rapamycin) inhibitors sirolimus (SRL) and everolimus (EVL) are potent immunosuppressive agents, which allow reducing the dose of the nephrotoxic calcineurin inhibitors cyclosporin and tacrolimus (TAC) in solid organ transplant recipients. However, there is evidence that mTOR inhibitors may lead to myelosuppression and dyslipidemia/hyperlipidemia. We therefore performed a retrospective analysis in heart transplant recipients with renal insufficiency, who received 3.0 mg/d SRL (SRL group; n = 28) or 1.5 mg/d EVL (EVL group; n = 27) each in combination with a reduced TAC dose for at least one yr. Fewer cardiac rejections, but a similar rate of infections occurred in the EVL group compared with the SRL group indicating that the administered EVL dose resulted in a potent immunosuppression. Serum triglyceride and total cholesterol concentrations rose significantly in the SRL group but not in the EVL group. In the SRL group only, the frequency of statin use increased significantly during follow-up. The EVL group showed a significant rise in HDL cholesterol levels during follow-up. There was a slight transient fall in haemoglobin concentrations in the SRL group but not in the EVL group. Leucocyte counts fell significantly in both study groups. However, no cases of leucopenia and also no cases of thrombopenia occurred. In summary, we could demonstrate that in heart transplant recipients with renal insufficiency the introduction of 1.5 mg/d EVL in combination with a reduced TAC dose is effective in preventing cardiac rejections and has less adverse effects on lipid metabolism than the usually prescribed SRL dose, whereas both therapy regimens are not associated with major haematological side-effects.

Critical care perspective on immunotherapy in lung transplantation

Lung transplantation is now a viable therapeutic option in the care of patients with advanced pulmonary parenchymal or pulmonary vascular disease. Lung transplantation, however, with chronic posttransplant immunosuppression, creates a uniquely vulnerable population of patients likely to experience significant life-threatening complications requiring intensive care. The introduction of several novel immunosuppressive agents, such as sirolimus and mycophenolate mofetil, in conjunction with more established agents such as cyclosporine and tacrolimus, has greatly increased treatment options for lung transplant recipients and likely contributed to improved short-term transplant outcomes. Modern transplant immunosuppression, however, is associated with a host of complications such as opportunistic infections, renal failure, and thrombotic thrombocytopenic purpura. The main focus of this review is to provide a comprehensive summary of modern immunotherapy in lung transplantation and to increase awareness of the serious and potentially life-threatening complications of these medications.

An open prospective pilot study on the use of rapamycin after penetrating high-risk keratoplasty

BACKGROUND

The purpose of this study was to prove efficacy and safety of systemic immunosuppression with rapamycin following penetrating high-risk keratoplasty. Rapamycin has shown its immunosuppressive potential in the rat keratoplasty model and is a component of several immunosuppressive protocols after solid organ transplantation. In this pilot study, we compared the efficacy and safety of rapamycin and mycophenolate mofetil (MMF).

METHODS

Ten patients (group 1) undergoing high-risk keratoplasty were included in this study, receiving rapamycin as postoperative immunoprophylaxis. Rapamycin was administered orally once daily (blood trough level 4-10 ng/ml) for 6 months. Thereafter, it was tapered over 2 weeks. The control group (group 2) consisted of 24 patients who received 1000 mg MMF twice daily for 6 months. All of the patients received postoperative medication with fluocortolone 1 mg/kg/day (tapered over 3 weeks) and prednisolone acetate eyedrops 5 times per day (tapered over 5 months).

RESULTS

Mean follow-up of all patients (n=34) was 739 days. No immune reaction was observed in groups 1 and 2 during the first 6 months under immunosuppression. Two immune reactions occurred in group 1, and five in group 2 within a 2-year follow-up. All of the immune reactions were reversible. The side effects observed in both groups were mostly reversible.

CONCLUSIONS

Rapamycin and mycophenolate mofetil seem to be similarly efficacious in preventing immune reactions after high-risk keratoplasty, as long as they are administered. However, we observed a broad spectrum of side effects from rapamycin.

Rapamycin in lung transplantation

INTRODUCTION

Rapamycin (RAPA) is a powerful immunosuppressant that also acts as an antiproliferative, which, therefore, could be useful in the treatment and prevention of bronchiolitis obliterans (BOS) in lung transplant recipients. We sought to report our experiences with RAPA in lung transplant patients with BOS that has not responded to the administration of other drugs.

MATERIALS AND METHODS

We performed a retrospective analysis of the clinical characteristics, pulmonary function, and complications among patients with BOS who received RAPA.

RESULTS

RAPA was administered to 11 patients, three single-lung transplant and eight bilateral lung transplant recipients, of whom five were women and six men, of mean age 48 years (26 to 65). The median posttransplant time to the initiation of RAPA for progressive BOS was 32 months (4 to 69) with a posttreatment follow-up of 15 months (3 to 34). RAPA was administered to all patients in association with a calcineurin inhibitor (tacrolimus in seven cases, and cyclosporine in four and steroids. Eight of the 11 patients (72%) with progressive deterioration of pulmonary function showed improved and/or stabilized FEV1 figures after introduction of RAPA. Eight patients developed adverse effects, which were possibly related to RAPA, leading to treatment withdrawal in two cases. The most frequent adverse effects were infections among 6 of the 12 cases, and myelosuppression in three.

CONCLUSIONS

RAPA may be useful to stabilize or improve pulmonary function in patients with BOS. Nevertheless, it was necessary for patients to be closely monitored so that possible adverse effects, and especially infections, may be detected early.