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There are still no approved agents for preventing severe acute (a) graft-versus-host disease (GvHD), which is a major cause of non-relapse mortality (NRM). For patients undergoing hematopoietic stem cell transplantation, especially human leukocyte antigen (HLA)-mismatched unrelated donor transplant (MMUD), severe aGvHD remains a significant cause of morbidity and mortality.
In an article published in the Journal of Clinical Oncology, Benjamin Watkins and colleagues describe the results of the phase II ABA2 trial (NCT01743131), which investigated adding abatacept, a T-cell costimulation blocker currently approved for rheumatoid arthritis, to a calcineurin inhibitor and methotrexate (CNI/MTX) for GvHD prophylaxis.1
A subanalysis was presented by Muna Qayed at the Transplantation and Cellular Therapy (TCT) 2021 Meetings of ASTCT and CIBMTR comparing the outcome of abatacept treatment in patients with MMUD transplant with placebo-treated patients who had received a matched unrelated donor (MUD) transplant.2
Three cohorts were included in this study (see also Table 1). Patients undergoing transplant with stem cells from 8/8 HLA-matched unrelated donors (MUD study cohort, n = 148 enrolled) were randomly assigned (1:1) to receive CNI/MTX plus placebo or abatacept. Patients transplanted with 7/8 HLA-mismatched donor stem cells (MMUD study cohort, n = 46 enrolled) received CNI/MTX plus abatacept, and these were compared with a prespecified control cohort from the Center for International Blood and Marrow Transplant Research (CIBMTR).
Patients were given:
Other endpoints included Grade III–IV aGvHD at Day +180; Grade II–IV aGvHD at Days +100 and +180; cGvHD at 1 year; NRM; relapse; relapse-free survival (RFS); overall survival (OS); cytomegalovirus reactivation and disease; Epstein-Barr virus reactivation and post-transplant lymphoproliferative disease; hematologic recovery; and donor engraftment.
Table 1. Baseline patient and transplant characteristics1
MMUD |
MUD |
||||
---|---|---|---|---|---|
Aba |
CIBMTR control |
Aba |
Placebo |
||
Median age, years (range) |
36.7 (6.6−76.5) |
45 (6.0−74.4) |
44.1 (6.9−71.9) |
41 (7.6−74.2) |
|
Age > 21 years, % |
57.9 |
69.3 |
78.1 |
75.4 |
|
White ethnicity, % |
68.4 |
82.7 |
86.3 |
87.0 |
|
Performance scores > 90%, % |
76.3 |
74.8 |
71.2 |
75.4 |
|
CIBMTR disease stage, % |
Advanced |
13.2 |
15.7 |
15.1 |
20.3 |
Intermediate |
15.8 |
14.2 |
19.2 |
23.2 |
|
Early |
68.4 |
69.3 |
64.4 |
55.0 |
|
Chemosensitive |
2.6 |
0.8 |
1.3 |
1.4 |
|
Conditioning intensity, % |
MAC |
73.7 |
68.5 |
75.3 |
71.0 |
RIC |
26.3 |
31.5 |
24.7 |
29.0 |
|
CNI, % |
Tacrolimus |
68.4 |
75.6 |
84.9 |
84.1 |
Cyclosporine |
31.6 |
24.4 |
15.1 |
15.9 |
|
Graft type, % |
Peripheral blood |
47.4 |
62.2 |
54.8 |
62.3 |
Bone marrow |
52.6 |
37.8 |
45.2 |
37.7 |
|
Aba, abatacept; CIBMTR, Center for International Blood and Marrow Transplant Research; CNI, calcineurin inhibitor; MAC, myeloablative conditioning; MMUD, mismatched unrelated donor; MUD, matched unrelated donor; RIC, reduced intensity conditioning. *Data from patients matched to the CIBMTR control group. |
The most common malignancy experienced in this patient population was acute myeloid leukemia, followed by acute lymphoid leukemia and myelodysplastic syndromes. As listed in Table 1, most patients received myeloablative conditioning. Controls were well matched for patient characteristics, and the majority of patients received tacrolimus as CNI – this was especially prominent in the 8/8 cohort.
Sex matching of donors and recipients was achieved in roughly 50% of patients across all groups, and graft source was split between peripheral blood and bone marrow across the whole population. However, in the historical CIBMTR control group, data on sex matching was missing in 28% of patients and data on the donor-recipient Epstein-Barr virus status was not available.
Table 2. Outcome of treatment1
Outcomes |
MMUD |
MUD |
||||
---|---|---|---|---|---|---|
Aba |
CIBMTR |
p value |
Aba |
Placebo |
p value |
|
Acute GvHD at Day 100, % (80% CI) |
||||||
Grade II−IV |
39.5 (29.2−49.6) |
53.2 (47.3−58.7) |
0.06 |
43.1 (35.5−50.6) |
62.1 (53.9−69.3) |
0.006 |
Grade III-IV |
0 (0−0) |
30.2 (25.0−35.5) |
< 0.001 |
6.8 (3.7−11.3) |
14.8 (9.7−20.8) |
0.13 |
Acute GvHD at Day 180, % (80% CI) |
||||||
Grade II−IV |
39.5 (29.2−49.6) |
57.4 (51.3−62.9) |
0.03 |
44.8 (37−52.3) |
63.7 (55.5−70.8) |
0.006 |
Grade III−IV |
0 (0−0) |
32.1 (26.7−37.5) |
< 0.001 |
6.8 (3.7−11.3) |
14.8 (9.7−20.8) |
0.13 |
Chronic GvHD at 1 year, % (80% CI) |
||||||
Mild-severe |
62.2 (50.0−72.2) |
45.9 (39.6−51.9) |
0.74 |
51.9 (43.8−59.3) |
45.3 (36.8−53.3) |
0.55 |
Mod-severe |
N/A |
44.6 (36.8−52.2) |
36 (28.2−44) |
0.32 |
||
Other outcome measures, % (80% CI) |
||||||
SGFS at Day 180 |
100 (100−100) |
58.7 (52.7−64.2) |
< 0.001 |
93.2 (88.2−96.1) |
82 (75−87.2) |
0.05 |
Relapse |
7.9 (3.4−14.8) |
21.4 (16.7−26.5) |
0.21 |
21.5 (15.4−28.1) |
23.6 (17.2−30.5) |
0.66 |
RFS at 2 years |
75.9 (64.1−84.1) |
38.3 (32.4−44.1) |
0.001 |
65.7 (57.8−72.5) |
60.3 (52.2−67.5) |
0.28 |
NRM at 2 years |
16.3 (8.5−26.3) |
40.3 (34.4−46.1) |
0.01 |
12.8 (8.2−8.5) |
16.1 (10.9−22.3) |
0.45 |
OS at 2 years |
76.9 (64.4−85.2) |
45.3 (39.3−51.1) |
0.002 |
74.3 (66.9−80.4) |
64 (55.9−71) |
0.15 |
Aba, abatacept; CI, confidence interval; CIBMTR, Center for International Blood and Marrow Transplant Research control group; GvHD, graft-versus-host disease; MMUD, mismatched unrelated donor; mod, moderate; MUD, matched unrelated donor; NRM, non-relapse mortality; OS, overall survival; RFS, relapse free survival; SGFS, severe aGvHD-free survival. Significant values are highlighted in bold. |
The focus of this subanalysis was to compare safety of 43 abatacept-treated patients with MMUD transplant with 69 placebo-treated patients who had received an MUD transplant in the ABA2 trial.2 This subanalysis confirmed that the MMUD cohort treated with abatacept showed a significantly reduced risk of aGvHD Grade II−IV compared with the MUD cohort treated with placebo (p = 0.013). This significant reduction was also seen for severe aGvHD (Grade III−IV) with a cumulative incidence of 2.3% for the MMUD cohort vs 14.8% for the MUD cohort (p = 0.033). As in the main analysis, no impact was seen on the incidence of cGvHD following abatacept treatment. No statistical difference was found between both cohorts for TRM, survival outcomes, relapse, engraftment, immune reconstitution, and viral reactivation.
The subanalysis concluded that due to the reduced risk of severe aGvHD in MMUD transplanted patients receiving abatacept, the disadvantages of using MMUD can be overcome. This may mitigate the racial/ethnic differences in outcomes following HSCT which are partly due to the decreased availability of MUD for Black people. Muna Qayed also reported on the initiation of a trial (NCT04380740) to investigate the impact of extending the duration of treatment of abatacept on cGvHD.
Safe and effective GvHD prophylaxis strategies for patients without HLA-matched sibling donors are desperately needed. In ABA2, abatacept was shown to reduce the incidence of aGvHD in patients receiving MMUD and MUD transplants and greatly improve survival outcomes for the MMUD cohort when compared to a matched historical control. The safety profile for this treatment was also shown to be acceptable. However, using a four-dose regimen of abatacept in this trial was not shown to have any impact on the incidence of chronic GvHD. In order to assess if a longer dosing schedule would improve the risk of cGvHD development, further trials are necessary.
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