Biosimilars: recent developments

Biopharmaceuticals are recombinant protein drugs which are produced by biotechnology. The availability of such molecules has revolutionised the way we treat many diseases. However, the patents for many originator biopharmaceuticals are expiring, and a new generation of follow-on molecules, termed “biosimilars”, are under development. Health care providers perceive biosimilars to be cheap replacements for originator drugs such as recombinant human erythropoietin and human growth hormone. However, concerns have been raised about the comparability of biosimilars with originator products especially in light of the complex manufacturing process required to produce biopharmaceuticals. The complexity of protein molecules renders it impossible to produce identical copies; this in turn raises questions on the safety of follow-on biosimilar products, particularly with respect to immunogenicity. This review briefly outlines the process of biopharmaceutical production, potential problems that can arise from their long-term use in patients, and the issues facing regulatory bodies as they look to institute guidelines for new biosimilar molecules.     

成功抢救2例高龄胰肾联合移植患者严重PRCA并发症

目的 探讨高龄胰肾联合移植病人免疫抑制低下与发生纯红细胞再障(PRCA)的关系。方法 1998年12月，5例胰肾移植患者中2例并发PRCA及自身免疫溶血性贫血，监测微小病毒B19,T4／T8比值及骨髓象。采用调整免疫抑制剂、抗病毒、输注红细胞等综合疗法。结果 2例PRCA患者分别于2周、3周骨髓象恢复正常，并观察1年以上无复发。结论 高龄、免疫力低下、微小病毒B19感染、免疫抑制药物易诱发PRCA，临床综合治疗是有效措施。     

Successful treatment of tacrolimus‐related pure red cell aplasia and autoimmune hemolytic anemia with rituximab in a pediatric cardiac transplant patient

Acquired pure red cell aplasia (PRCA) and autoimmune hemolytic anemia (AIHA) are rare complications of immunosuppression in pediatric solid organ transplant patients. We report a 14‐month‐old female child who developed Coombs positive hemolytic anemia and reticulocytopenia while on tacrolimus after cardiac transplantation. She was successfully treated with rituximab after failing treatment with corticosteroids and intravenous immunoglobulins. Clinicians should consider PRCA differential diagnosis in a patient presenting with reticulocytopenia and hemolysis. In addition, the coexistence of PRCA with AIHA, and the response to therapy with rituximab, supports a common immune‐mediated pathogenesis for both disorders.     

Development of pure red cell aplasia by transmission and persistent infection of parvovirus B19 through a kidney allograft

We report a case of pure red cell aplasia (PRCA) caused by parvovirus B19 (PVB19) infection, which was transmitted through a kidney allograft. The patient underwent a living‐donor kidney transplant from his wife at the age of 60. Despite successful engraftment with a normal creatinine level, he developed severe anemia that required frequent blood transfusions 2 months after transplantation. Renal anemia was unlikely as his serum erythropoietin level was extremely high. A bone marrow aspiration test demonstrated the existence of large proerythroblasts. Although anti‐PVB19 IgM antibody levels were not increased, polymerase chain reaction (PCR) detected PVB19 DNA in his serum. Thus, he was diagnosed as having PRCA induced by PVB19 infection. PCR analysis of total DNA isolated from 0‐hour biopsy sections showed the existence of PVB19 DNA. Furthermore, PVB19 proteins was detected on renal tubules of 0‐hour allograft by immunoperoxidase staining. Thus, transmission of PVB19 through the allograft was confirmed. A single course of intravenous immunoglobulin (IVIG) therapy resulted in substantial improvement; however, the effect was limited, and severe anemia relapsed after 5‐6 months. Several courses of IVIG with adjustment of immunosuppressive drugs resulted in long‐term remission. Our case demonstrates that donor‐transmitted PVB19 infection should be suspected in kidney transplant recipients who develop refractory anemia during the early post‐operative phase.     

Diamond-Blackfan anemia: Clinical features and treatment results in 4 cases

Diamond-Blackfan anemia is a rare hematological disease characterized by selective marrow erythroid hypoplasia. We present the clinical and hematological profile and results of treatment in four children. The median age at presentation was 14 months with a median age of onset of pallor at 7.5 months. Mean Hb at presentation was 2.9 g/dl. All children were started on prednisolone with response in one child. One child was switched to dexamethasone and responded transiently relapsing in 4 months but responded to further dexamethasone. Two children required cyclosporin for 3 and 8 weeks for response. With median follow-up of 59 months, all four children continue in complete hematological remission with no further relapses.     

Changes of isoagglutinin titres after ABO-incompatible allogeneic stem cell transplantation

We investigated the changes in isoagglutinin titres in 62 patients who underwent ABO-incompatible allogeneic stem cell transplantation. After major [and/or (+/-) minor] ABO-incompatible transplantation, recipient-derived isoagglutinins against donor-type red blood cells (RBCs) disappeared more rapidly in unrelated recipients (P = 0.006) and in patients with acute graft-versus-host disease (GVHD, P = 0.025) than in sibling recipients and in patients without acute GVHD respectively. Pure red cell aplasia (PRCA) developed in 10 out of 35 evaluable patients who underwent major (+/- minor) ABO-incompatible transplantation, and the post-transplant increase of isoagglutinin titres was a significant predictor for the occurrence of PRCA. In five out of 36 patients who underwent minor (and/or (+/-) major) ABO-incompatible transplantation, donor-derived isoagglutinins against recipient RBCs were detectable without clinically overt haemolysis. Isoagglutinin titres against ABO antigens absent both on recipient and donor RBCs decreased during the early post-transplant period then rose subsequently in 24 out of 29 patients at (median) d 59 post transplant. Our study showed that changes in isoagglutinin titres might have clinical implications in the occurrence of immunohaematological complications such as PRCA or immune-mediated haemolysis, and might reflect immunohaematological reconstitution after transplantation. Furthermore, our data regarding time to disappearance of recipient-derived isoagglutinins against donor-type RBCs after major ABO-incompatible transplantation suggest the presence of a graft-versus-plasma cell effect.     

23例儿童纯红细胞再生障碍性贫血临床分析

目的探讨儿童单纯红细胞再生障碍性贫血（pure red cell aplasia，PRCA）的发病机制、诊断和治疗。方法对我院1994年至2004年期间收治的23例PRCA患者进行回顾性分析。总结其病因、临床特点及治疗。结果先天性PRCA 10例，获得性PRCAl3例，其中5例继发于病毒感染，8例未找到明确病因。实验室检查：血红蛋白及网织红细胞均下降，白细胞、血小板正常。骨髓检查红系增生低下17例，停滞6例。骨髓干细胞培养10例，7例生长不良。染色体检查8例均正常。治疗以单纯激素口服，甲基强的松龙冲击，激素联合丙种球蛋白以及其他免疫抑制剂为主。目前停药9例，小剂量激素维持11例，无效3例。长期应用激素有多毛、骨质疏松、高血压、身材矮小、白内障等副作用。结论儿童PRCA大部分病因不明确，部分病人与病毒感染相关。诊断需依靠血像及骨髓像。肾上腺皮质激素治疗效果良好，联合丙球治疗可获得更好的疗效。病毒感染继发的PRCA是可治愈的，应首先在抗病毒治疗的同时应用免疫抑制剂。长期口服激素需注意其副作用。     

A sustained response to low dose interferon-alpha in a case of refractory pure red cell aplasia

Acquired pure red cell aplasia (PRCA) may be the result of a cellular or humoral autoimmune process. One proposed mechanism is the destruction of erythroid progenitors by self-reactive, cytotoxic T cells or natural killer (NK) cells. These cells normally express MHC class I receptors (KIR) which inhibit cytotoxicity when the target cell expresses the HLA class I antigen(s) they bind. Therefore, loss of these antigens on maturing erythroid progenitors may render them susceptible to destruction by the pathogenic cells. Interferon-alpha (INF-alpha) increases HLA class I expression on hematopoietic precursor cells. Therefore, we initiated a trial of INF-alpha in a patient with refractory PRCA. Following treatment, he developed transfusion independence, and a sustained normal hematocrit. Analysis of bone marrow erythroid cells revealed an increase in expression of HLA class I molecules. INF-alpha should be used in a controlled trial in patients with PRCA to determine its activity and mechanism of action.     

Computed tomography of renal cell carcinoma in patients with terminal renal impairment

Purpose

An increased incidence of renal tumors has been observed in patients with end-stage-renal-disease (ESRD). The very strong association with acquired renal cystic disease (ACRD) and increased incidence of the renal tumors (conventional renal cell carcinoma (CRCC), papillary renal cell carcinoma (PRCC) or papillary renal cell adenoma (PRCA)) was reported. This study discusses the role of computed tomography (CT) in detecting renal tumors in patients with renal impairment: pre-dialysis, those receiving dialysis or with renal allograft transplants.

Materials and methods

Ten patients (nine male, one female) with renal cell tumors were enrolled into a retrospective study; two were new dialysis patients, three on long-term dialysis, and five were renal transplant recipients with history of dialysis. All patients underwent helical CT, a total of 11 procedures were performed. Sixteen-row detector system was used five times, and a 64-row detector system for the six examinations. All patients underwent nephrectomy of kidney with suspected tumor, 15 nephrectomies were performed, and 1 kidney was assessed during autopsy. CT findings were compared with macroscopic and microscopic assessments of the kidney specimen in 16 cases.

Results

Very advanced renal parenchyma atrophy with small cysts corresponding to ESRD was found in nine patients, chronic pyelonephritis in remained one. A spontaneously ruptured tumor was detected incidentally in one case, patient died 2 years later. In the present study, 6.25% (1/16) were multiple PRCA, 12.5% (2/16) were solitary PRCC, 12.5% tumors (2/16) were solitary conventional renal cell carcinomas (CRCC's), 12.5% tumors (2/16) were multiple conventional renal cell carcinomas (CRCC's), 25% (4/16) were CRCC's combined with multiple papillary renal cell carcinomas with adenomas (PRCC's and PRCA's), and 25% (4/16) of the tumors were multiple PRCC's combined with PRCA's without coexisting CRCC's. Bilateral renal tumors were found in our study in 60% (6/10) confirmed in six cases, one kidney left on follow-up due to the small tumors.

Conclusions

With the use of a multi-detector row system, it is possible to detect smaller foci suspected to originate in multiple tumors, especially when up to 3-mm thin multi-planar reconstructions are used. Two cases demonstrated the possibility the development of RCC in impaired kidneys may start before dialysis initiation.