Abstract
In sight of different pharmacokinetics between races, the recommended dose is 75mg/d for Asian using eltrombopag [1]. However, the efficacy and safety of antithymocyte immunoglobulin (ATG) and cyclosporin A (CsA) with eltrombopag are still largely unknown for adult Asian patients with severe aplastic anemia (SAA).
From May 2014 to March 2021, 121 Chinese adult patients with SAA were treated with IST (r-ATG, 3.5mg/kg/d × 5d and CsA 3-5 mg/kg/d) or in conjunction with eltrombopag (75mg/d, from day 1 to 6 months) prospectively and non-randomly. The adverse events (≥3 grades) referring to Common Terminology Criteria for Adverse Events version (CTCAE) 5.0 within 6 months.
In pretreatment evaluation of clinical and laboratory characteristics. Median age (39 years and 40 years) was comparable. The complete blood count with differential and quantification of CD4/CD8 T-cell subsets were similar in both groups, but median time from diagnosis to treatment (16 d and 28 d, P=0.038) was different significantly (Table 1).
The Chi-Squared test was used to compare the efficacy. The overall response rates (ORR) of IST alone or in combination with eltrombopag in the 1st, 3rd, 6th and 12th month after IST were 12% vs 35% (P=0.002), 44% vs 64% (P=0.028), 61% vs 85% (P=0.006) and 73% vs 91% (P=0.031), respectively. The complete response (CR) rates in the 3rd, 6th and 12th month after IST are 7% vs 17% (P=0.069), 14% vs 27% (P=0.11) and 33% vs 32% (P=0.92) (Table 2).
We analyzed factors associated with the efficacy at 6 months by the Binary-Logistic regression model. Elements would be listed in multivariate analysis whether the factors might impact on the efficacy or had P value lower than 0.2 in univariate analysis. It was suggested that ORR was significantly related with the use of eltrombopag (P=0.011, OR=3.600, 95%CI 1.345-9.638) (Table 3).
The overall survival (OS) and factors related to survival were analyzed by Kaplan-Meier method and Cox regression model. The OS in IST combined with eltrombopag group was 98% compared to 88% for IST alone (P=0.078). No significant intergroup differences were noted in multivariate analysis of OS.
The nonhematologic adverse events (≥3 grades) were infrequent, occurring in 16% patients. 8 in IST plus E-PAG cohort and 11 in IST alone cohort (15% vs 16%, P=0.80). Hepatic injury was prevalent complication (6% vs 8%, P=0.96), relatively. But none showed significant difference between two groups.
Discussion
It has been reported that eltropopag promoted the response of megakaryocytic or even three lineages in refractory SAA [2]. The 6th month CR rate and ORR of our study are lower than the results of Townsley's research with 35% and 94% in the cohort of IST plus eltrombopag [1]. But the CR rate ORR is comparable to De Latour's results with 21.9% and 59.4% in the 3rd month [3]. Median age and dosage of eltrombopag needs to be considered with caution between different researchs, whist the efficacy of horse ATG (hATG) and rATG remained a subject of some debate [4]. Townsley et al. had reported that hepatic impairment (≥3 grades) was 18% [1], but our research showed lower rate of liver impairment with 6%. We should increase the sample volume to analyze the adverse events.
Reference
[1] Townsley DM, et al. Eltrombopag Added to Standard Immunosuppression for Aplastic Anemia [J]. N Engl J Med, 2017, 376 (16): 1540-1550.
[2] Desmond R, et al. Eltrombopag restores trilineage hematopoiesis in refractory severe aplastic anemia that can be sustained on discontinuation of drug [J]. Blood, 2014, 123 (12): 1818-1825.
[3] De Latour, RP, et al. Results of the EBMT SAAWP Phase III Prospective Randomized Multicenter RACE Study of Horse ATG and Ciclosporin with or without Eltrombopag in naive SAA patients. EBMT 2020 abstract O018.
[4] Vallejo, C., et al., Rabbit antithymocyte globulin versus horse antithymocyte globulin for treatment of acquired aplastic anemia: a retrospective analysis. Annals of Hematology, 2015. 94(6): p. 947-954.
He: F. Hoffmann-La Roche Ltd.: Consultancy; LongBio Pharma: Consultancy, Research Funding.
