Low dose antithymocyte globulin for the treatment of older patients with aplastic anaemia

Comparable outcomes with low-dose and standard-dose horse anti-thymocyte globulin in the treatment of severe aplastic anemia

BACKGROUND

The standard dose (SD) of horse anti-thymocyte globulin (hATG) ATGAM (Pfizer, USA) or its biosimilar thymogam (Bharat Serum, India) for the treatment of Aplastic Anemia (AA) is 40 mg/kg/day for 4 days in combination with cyclosporine. Data on the impact of hATG dose on long-term outcomes are limited. Here, we describe our comparative experience using 25 mg/kg/day (low-dose [LD]) hATG for 4 days with SD for the treatment of AA.

METHODS

We retrospectively studied patients with AA (age > 12 years) who received two doses of hATG combined with cyclosporine. Among 93 AA patients who received hATG, 62 (66.7%) and 31 (33.3%) patients received LD and SD hATG with cyclosporine, respectively. Among these,seventeen(18.2%) patients also received eltrombopag with hATG and cyclosporine. Overall response rates [complete response (CR) and partial response (PR)] of LD and SD hATG groups at 3 months (50% vs. 48.4%; p = 0.88), 6 months (63.8% vs. 71.4%; p = 0.67), and 12 months (69.6% vs. 79.2%; p = 0.167) were comparable. The mean (Standard Deviation) 5-year Kaplan-Meier estimate of overall survival and event-free survival was 82.1 (4.6)% and 70.9 (5.5)% for the study population. The mean (standard deviation) 5-year Kaplan-Meier estimate of overall survival and event-free survival of those who received LD hATG versus SD hATG dose was 82.9 (5·3)% versus 74.8 (10·3)% (P = 0·439), and 75.2 (6.2)% versus 61.4(11.2)% (P = 0·441).

CONCLUSION

Our study revealed that the response rates of patients with AA and LD were similar to those of patients with SD to hATG combined with cyclosporine in a real-world setting.

Very severe aplastic anemia in an 80-year-old man

Although the patient with very severe aplastic anemia might be a fit elderly receiving standard therapy, there are factors which contribute to an adverse outcome such as severity of pancytopenia, absence of minor paroxysmal nocturnal hemoglobinuria clone and infective complications of therapy.

[Antithymocyte/Antilymphocyte globulin plus cyclosporine A therapy for the treatment of older patients with severe aplastic anemia]

目的

评估老年（≥60岁）重型再生障碍性贫血（SAA）患者接受兔抗人胸腺细胞球蛋白（rATG）／猪抗人淋巴细胞球蛋白（pALG）联合环孢素A(CsA）的强烈免疫抑制治疗（IST）方案的疗效和安全性。

方法

回顾性分析16例老年SAA患者接受rATG/pALG+CsA治疗的血液学反应率和安全性，分析影响疗效的相关因素。

结果

16例患者男13例，女3例，中位年龄63.5(60~79）岁，其中60~69岁13例，≥70岁3例；SAA患者9例，极重型AA(VSAA）患者7例；9例患者接受rATG治疗，7例患者接受pALG治疗。16例患者均顺利完成rATG/pALG治疗，治疗后早期死亡2例（12.5%），均为VSAA患者（2/7, 28.6%）；IST后6个月9例（56.3%）患者获得血液学反应，5例无治疗反应。9例应用rATG的患者有2例获得血液学反应，7例应用pALG患者全部获得血液学反应，差异有统计学意义（22.2％对100.0%，P=0.003）。rATG/pALG+CsA相关不良反应轻微，经对症治疗好转。

结论

老年SAA接受rATG/pALG联合CsA的IST方案仍可获较好血液学反应；VSAA患者早期死亡率高，治疗风险大；pALG治疗老年SAA疗效可能优于rATG。

Treatment of aplastic anaemia with lower-dose anti-thymocyte globulin produces similar response rates and survival as per standard dose anti-thymocyte globulin schedules

BACKGROUND

Aplastic anaemia (AA) is a rare acquired bone marrow failure syndrome resulting from the immune-mediated destruction of haemopoietic stem cells. For adults in whom first-line haemopoietic progenitor cell transplantation is not feasible, combination anti-thymocyte globulin (ATGAM) plus cyclosporine A is standard therapy; however, there are minimal data available regarding the optimal ATGAM dosage in terms of efficacy and survival.

AIMS

Our institutions have historically used different dosing protocols of ATGAM in the treatment of AA. We aimed to review the outcome of AA patients treated with these protocols and compare them to the published literature.

METHODS

We conducted a retrospective study of 31 adults who received first-line ATGAM for AA and compared response rates and survival between cohorts who received standard (40 mg/kg/day D1-4) versus lower-dose (15 mg/kg/day D1-5) ATGAM schedules.

RESULTS

There were similar rates of response (64 vs 71%, P = 1.0), relapse (33 vs 33%, P = 1.0), transformation (14 vs 24%, P = 0.66) or infection (43 vs 47%, P = 1.0), respectively, between standard and lower-dose cohorts. At a median follow up of 24 months, there was no statistical difference between standard and lower-dose cohorts in either event-free (42.2 vs 64.7%, P = 0.91) or overall survival (73.1 vs 88.2%, P = 0.75).

CONCLUSION

Our experience suggests that lower-dose ATGAM at 15 mg/kg/day D1-5 as treatment of AA produces similar responses and outcomes as per standard-dose ATGAM schedules. Prospective trials comparing ATGAM dose schedules in AA are warranted.

Rabbit ATG but not horse ATG promotes expansion of functional CD4+CD25highFOXP3+ regulatory T cells in vitro

Regulatory T cells (Treg) play important roles in suppressing immune responses and maintaining tolerance. Rabbit antithymocyte globulin (rATG) and horse ATG (hATG) are widely used in the treatment of immune-mediated syndromes, but their effects on Treg are unknown. We show here that in vitro culture of normal human peripheral blood mononuclear cells (PBMCs) with a low-dose rATG resulted in marked expansion of functional Treg by converting CD4+CD25- T cells to CD4+CD25+ T cells. hATG did not expand but rather decreased Treg. Immuno-blot showed increased expression of FOXP3 and NFAT1 in CD4+CD25- and CD4+CD25+ T cells exposed to rATG. PBMCs treated with rATG displayed increased interleukin-10 in culture supernatants than those treated with hATG. Furthermore, rATG and hATG showed differences in their potential to stimulate CD4+ T cells as examined using different activation markers. Microarray revealed that rATG induced markedly different gene-expression patterns in PBMCs, compared with hATG-treated or untreated PBMCs. Our findings indicate that rATG expanded Treg, probably through transcriptional regulation by enhanced NFAT1 expression, in turn conferring CD4+CD25- T cell FOXP3 expression and regulatory activity. The therapeutic effects of rATG may occur not only because of lymphocyte depletion but also enhanced Treg cell number and function.

Making therapeutic decisions in adults with aplastic anemia

The management of adults presenting with aplastic anemia (AA) requires careful exclusion of other causes of bone marrow failure. Late-onset inherited forms of AA may present in adulthood with subclinical disease. Recent long-term studies of HLA identical sibling donor BMT show excellent survival for patients under the age of 40 years, but chronic graft-versus-host disease (GVHD) is still a major problem, impacting on quality of life. Recent improvements in outcome after matched unrelated donor BMT may reflect better donor matching and use of reduced intensity conditioning regimens. For patients treated with immunosuppressive therapy (IST), antithymocyte globulin (ATG) and cyclosporin (CSA) remain the standard regimen with excellent overall survival but less impressive failure-free survival due to nonresponse, relapse and later clonal disorders. The benefit of adding granulocyte colony-stimulating factor (G-CSF) to ATG and CSA is unclear and being assessed in a further prospective European study. Patients who are refractory to conventional IST and currently ineligible for BMT represent difficult management problems. For these patients, new approaches to transplantation are being evaluated, such as fludarabine-based conditioning regimens and the potential use of double umbilical cord blood transplants, but there is a need for new immunosuppressive agents. Improved supportive care is likely to be a major factor in improved outcome of all AA patients whether treated with IST or BMT. Robust predictive factors for response to IST are needed to help in decision making at diagnosis and to help justify exploring novel approaches to therapy.