Bortezomib for the Management of Relapsed or Refractory Warm Autoimmune Hemolytic Anemia: A Scoping Review
Authors: Johnson Eric , Lesh Nicholas , Hildebrand Gregory , Shah Harsh , Osman Afaf , Abou-Ismail Mouhamed Yazan 
Published: November 2021

Abstract
Background:
Auto-immune hemolytic anemia (AIHA) may be complicated with a relapsed or refractory course and may lead to life-threatening complications. The management of severe cases refractory to multiple lines of therapy is challenging, and data on the use of subsequent therapeutic agents remains scarce. Plasma cells have been postulated as potential therapeutic targets due to their role in auto-antibody production. Studies on plasma-cell directed therapies, such as bortezomib (BTZ), for the management of AIHA are lacking, and clinical trials remain ongoing.
Objectives:
To perform a scoping review on existing literature on the use of BTZ in the management of warm AIHA (wAIHA) and its outcomes, and to report an additional case of successful use of BTZ at our institution.
Methods:
We performed an extensive literature search using MEDLINE (Ovid), Embase, Scopus, and PubMed on all existing reports on BTZ use in wAIHA. Patients with hematopoietic cell transplant-associated AIHA were excluded.
We defined complete response (CR) as a hemoglobin (Hb) &gt; 10 g/dL, Hb increase of &gt; 2 g/dL, and a complete cessation of corticosteroids (CS) or other immunosuppression (IS). We defined partial response (PR) as a Hb rise &gt; 2 g/dL, with stable or decreased long-term IS requirements. Onset of response was defined as the time in days after first BTZ dose when a Hb increase of &gt; 2 g/dL was first noted. Duration of response was defined as the time from response onset until relapse or cessation of follow-up. We applied our definitions uniformly across the original data (whenever reported) in the included studies. BTZ used as monotherapy or in addition to prior long-term IS was labeled "single-agent", and BTZ combined with rituximab (RTX) or cyclophosphamide (CTX) was labeled "combination regimen".
Case Description:
A 25-year-old male with Evans syndrome and prior therapy with CS, intravenous immunoglobulin (IVIG), splenectomy, cyclosporine, RTX and vincristine presented with severe thrombocytopenia and recurrent wAIHA. Despite receiving high-dose CS, IVIG, mycophenolate mofetil, RTX, CTX, and danazol, his AIHA persisted severely, while platelets normalized with romiplostim. He was then treated with BTZ 1.3 g/m2 (days 1, 4, 8, 11 every three weeks x 6 cycles) and his Hb improved from 5.8 g/dL to 14.4 g/dL currently, with an onset of response within 19 days and sustained response of 6 months until today. However, he continues to require maintenance BTZ and prednisone.
Results:
We identified 10 case series/reports (n=29, our patient included) in which BTZ was used to treat wAIHA, with a total of 32 evaluable incidents of BTZ use .
The median number of prior therapies was 5 (range: 1-8). BTZ was used in variable regimens and induction durations (Table 1), including single-agent BTZ (n=14), combination regimen (n=16), shorter induction (&lt;30 days) (n=13), and longer induction courses (n=13). 37.5% of responding patients required additional maintenance BTZ.
Response rates (Figure 1a):
Overall response rate (ORR) of cohort = 78%, CR = 43.8%, PR = 34.4%
CR with single-agent BTZ = 20%, combination regimen = 64.7%
Median onset of response (Figure 1b):
Overall cohort: 21 days [IQR: 13-35]
Single-agent BTZ: 21 days [IQR: 19-47]
Combination-regimen BTZ: 15 days [IQR: 7-21]
Duration of response (Figure 1c):
Overall cohort: 150 days [IQR: 120-426]
Single-agent BTZ: 272 days [IQR: 129-565]*, Combination-regimen: 150 days [IQR: 90-280]*
Short induction: 135 [IQR: 90-228], ongoing response at time of publication = 54%
Long induction: 365 [IQR: 132-555], ongoing response = 91%
*83% of single-agent arm received longer induction, vs 20% of combination group, potentially confounding results. Controlling for induction duration was not possible due to small numbers.
Safety:
No serious side effects were reported in our cohort. There were 2 deaths unrelated to BTZ.
Conclusion:
Limited data suggest that BTZ may be used as a subsequent therapy to treat relapsed or refractory wAIHA, and may offer complete or partial response in cases refractory to multiple therapeutic lines. BTZ combined with RTX or CTX seemed to offer higher rates of CR as well as faster onset of response in comparison to single-agent BTZ. The median time to onset of response was 2 to 3 weeks, and the median response duration was five months. Longer induction (&gt;30 days) was associated with longer durations of response. Our study is limited by publication bias, study heterogeneity, and small numbers.
Figure 1 Figure 1.

Disclosures
Shah: AstraZeneca: Research Funding; Seattle Genetics: Research Funding; Epizyme: Research Funding.

OffLabel Disclosure:
bortezomib for autoimmune hemolytic anemia