Treatment of refractory or relapsed acquired aplastic anemia: review of established and experimental approaches

Haploidentical BMT for severe aplastic anemia with intensive GVHD prophylaxis including posttransplant cyclophosphamide

Severe aplastic anemia (SAA) is a stem cell disorder often treated with bone marrow transplantation (BMT) to reconstitute hematopoiesis. Outcomes of related HLA-haploidentical (haplo) donors after reduced-intensity conditioning with intensive graft-versus-host disease (GVHD) prophylaxis including posttransplantation cyclophosphamide are presented here from 37 SAA, 20 relapsed/refractory (R/R), and 17 treatment-naïve (TN) SAA patients. Median follow-up is 32 months (90% confidence interval [CI], 29-44). The median age was 25 (range, 4-69) years. The median time to neutrophil recovery was 17 days (range, 15-88). Four of 37 patients (11%) experienced graft failure (GF). There was 1 primary GF of 20 patients in the R/R group and 3 of 17 in the TN group at 200 cGy (1 primary, 2 secondary), but none in the 10 patients who received 400 cGy total body irradiation. Two patients with GF succumbed to infection and 2 were rescued with second haplo BMT. The overall survival for all patients is 94% (90% CI, 88-100) at 1 and 2 years. The cumulative incidence of grade II-IV acute GVHD at day 100 is 11%. The cumulative index of chronic GVHD at 2 years is 8%. Similar results were seen in 10 SAA patients who received the identical nonmyeloablative regimen with posttransplant cyclophosphamide but matched donor transplants. Haplo BMT with posttransplant cyclophosphamide represents a potential cure in SAA, with all 20 R/R currently alive, disease-free, and with no evidence of active GVHD. Extending this approach to TN patients was associated with higher GF rates, but an increase in total body irradiation dose to 400 cGy was associated with durable engraftment without greater early toxicity. Nonmyeloablative haplo BMT in TN SAA could lead to a paradigm shift, such that essentially all patients can proceed quickly to safe, curative BMT. These trials were registered at www.cincialtrials.gov as #NCT02224872) and #NCT02833805.

Acquired severe aplastic anaemia: how medical therapy evolved in the 20th and 21st centuries

The progress in aplastic anaemia (AA) management is one of success. Once an obscure entity resulting in death in most affected can now be successfully treated with either haematopoietic stem cell transplantation (HSCT) or immunosuppressive therapy (IST). The mechanisms that underly the diminution of haematopoietic stem cells (HSCs) are now better elucidated, and include genetics and immunological alterations. Advances in supportive care with better antimicrobials, safer blood products and iron chelation have greatly impacted AA outcomes. Working somewhat 'mysteriously', anti-thymocyte globulin (ATG) forms the base for both HSCT and IST protocols. Efforts to augment immunosuppression potency have not, unfortunately, led to better outcomes. Stimulating HSCs, an often-sought approach, has not been effective historically. The thrombopoietin receptor agonists (Tpo-RA) have been effective in stimulating early HSCs in AA despite the high endogenous Tpo levels. Dosing, timing and best combinations with Tpo-RAs are being defined to improve HSCs expansion in AA with minimal added toxicity. The more comprehensive access and advances in HSCT and IST protocols are likely to benefit AA patients worldwide. The focus of this review will be on the medical treatment advances in AA.

Activity of eltrombopag in severe aplastic anemia

Since the approval of horse antithymocyte globulin (ATG) decades ago, there was a long hiatus in therapies with activity in severe aplastic anemia (SAA). This scenario changed in 2014 when eltrombopag, a thrombopoietin receptor agonist, was approved for SAA after an insufficient response to initial immunosuppressive therapy (IST). The basis for this approval was the observation of single-agent activity of eltrombopag in this patient population, where 40% to 50% recovered blood counts at times involving >1 lineage. The achievement of transfusion independence confirmed the clinical benefit of this approach. Increase in marrow cellularity and CD34+ cells suggested a recovery to a more functioning bone marrow. Further in its development, eltrombopag was associated with standard horse ATG plus cyclosporine in first line, producing increases in overall (at about 90%) and complete response rates (at about 40%) and leading to transfusion independence and excellent survival. Interestingly, best results were observed when all drugs were started simultaneously. The cumulative incidence of clonal cytogenetic abnormalities to date has compared favorably with the vast experience with IST alone in SAA. Longer follow-up will help in define these long-term risks. In this review, the development of eltrombopag in SAA will be discussed.

Activity of eltrombopag in severe aplastic anemia

Since the approval of horse antithymocyte globulin (ATG) decades ago, there was a long hiatus in therapies with activity in severe aplastic anemia (SAA). This scenario changed in 2014 when eltrombopag, a thrombopoietin receptor agonist, was approved for SAA after an insufficient response to initial immunosuppressive therapy (IST). The basis for this approval was the observation of single-agent activity of eltrombopag in this patient population, where 40% to 50% recovered blood counts at times involving >1 lineage. The achievement of transfusion independence confirmed the clinical benefit of this approach. Increase in marrow cellularity and CD34+ cells suggested a recovery to a more functioning bone marrow. Further in its development, eltrombopag was associated with standard horse ATG plus cyclosporine in first line, producing increases in overall (at about 90%) and complete response rates (at about 40%) and leading to transfusion independence and excellent survival. Interestingly, best results were observed when all drugs were started simultaneously. The cumulative incidence of clonal cytogenetic abnormalities to date has compared favorably with the vast experience with IST alone in SAA. Longer follow-up will help in define these long-term risks. In this review, the development of eltrombopag in SAA will be discussed.

Effects and Predictive Factors of Immunosuppressive Therapy Combined with Umbilical Cord Blood Infusion in Patients with Severe Aplastic Anemia

PURPOSE

To investigate the efficacy and safety of umbilical cord blood (UCB) infusion (UCBI) plus immunosuppressive therapy (IST) treatment in comparison to IST treatment, as well as predictive factors for clinical responses, in severe aplastic anemia (SAA) patients.

MATERIALS AND METHODS

Totally, 93 patients with SAA were enrolled in this cohort study. In the IST group, rabbit antithymocyte globulin (r-ATG) combined with cyclosporine A (CsA) was administered, while in the IST+UBCI group, r-ATG, CsA, and UCB were used.

RESULTS

After 6 months of treatment, UCBI+IST achieved a higher complete response (CR) rate (p=0.002) and an elevated overall response rate (ORR) (p=0.004), compared to IST. Regarding hematopoietic recovery at month 6, platelet responses in the UCBI+IST group were better than those in the IST group (p=0.002), and UCBI+IST treatment facilitated increasing trends in absolute neutrophil count (ANC) response (p=0.056). Kaplan-Meier curves illuminated UCBI+IST achieved faster ANC response (p<0.001) and platelet response (p<0.001), compared with IST therapy. There was no difference in overall survival (OS) between the two groups (p=0.620). Furthermore, logistic regression analysis demonstrated that UCBI+IST was an independent predicting factor for both CR (p=0.001) and ORR (p<0.001), compared to IST; meanwhile, very severe aplastic anemia (VSAA) and ANC could predict clinical responses as well. However, Cox proportional hazard regression indicated that VSAA (p=0.003), but not UCBI+IST, affected OS. Safety profiles showed that UCBI+IST therapy did not elevate adverse events, compared with IST treatment.

CONCLUSION

UCBI+IST achieved better clinical responses and hematopoietic recovery than IST, and was well tolerated in SAA patients.

Etanercept-associated transient bone marrow aplasia: a review of the literature and pathogenetic mechanisms

A patient with rheumatoid arthritis presented with increasing fatigue, fever, gingival bleeding, and petechial rash. Her symptoms started 1 week after the first injection of etanercept (Enbrel). Her only other medications (methotrexate and hydroxychloroquine) had been unchanged for years. Tests revealed severe pancytopenia and bone marrow aplasia. She recovered with supportive treatment within 12 days. The literature on serious blood dyscrasias associated with anti-tumor necrosis factor-α therapy is reviewed, an intriguing postulated mechanism is discussed, and selective patient monitoring is recommended.