Posttransplant relapse is the most significant challenge in allogeneic stem cell transplantation (alloSCT). Posttransplant interventions, in conjunction with optimal conditioning regimens and donor selection, are increasingly supported by evidence for their potential to prolong patient survival by promoting antileukemia or graft-versus-leukemia effects. Our review begins by highlighting the current evidence supporting maintenance therapy for relapse prevention in acute myeloid leukemia and acute lymphocytic leukemia. This includes a broad spectrum of strategies, such as targeted therapies, hypomethylating agents, venetoclax, and immunotherapies. We then shift our focus to the role of disease monitoring after alloSCT, emphasizing the potential importance of early detection of measurable residual disease and a drop in donor chimerism. We also provide an overview of salvage therapies for overt relapse, including targeted therapies, chemotherapies, immunotherapies, donor lymphocyte infusion, and selected agents under investigation in ongoing clinical trials. Finally, we review the evidence for a second alloSCT (HSCT2) and discuss factors that impact donor selection for HSCT2.

1.
Horowitz
M
,
Schreiber
H
,
Elder
A
, et al.
Epidemiology and biology of relapse after stem cell transplantation
.
Bone Marrow Transpl
.
2018
;
53
(
11
):
1379
-
1389
.
2.
DeFilipp
Z
,
Chen
Y-B
.
How I treat with maintenance therapy after allogeneic HCT
.
Blood
.
2023
;
141
(
1
):
39
-
48
.
3.
Xuan
L
,
Wang
Y
,
Huang
F
, et al.
Sorafenib maintenance in patients with FLT3-ITD acute myeloid leukaemia undergoing allogeneic haematopoietic stem-cell transplantation: an open-label, multicentre, randomised phase 3 trial
.
Lancet Oncol
.
2020
;
21
(
9
):
1201
-
1212
.
4.
Levis
MJ
,
Hamadani
M
,
Logan
B
, et al.
Gilteritinib as posttransplant maintenance for acute myeloid leukemia with internal tandem duplication mutation of FLT3
.
J Clin Oncol
.
2024
;
42
(
15
):
1766
-
1775
.
5.
Fathi
AT
,
Kim
HT
,
Soiffer
RJ
, et al.
Multicenter phase I trial of ivosidenib as maintenance treatment following allogeneic hematopoietic cell transplantation for IDH1-mutated acute myeloid leukemia
.
Clin Cancer Res
.
2023
;
29
(
11
):
2034
-
2042
.
6.
Fathi
AT
,
Kim
HT
,
Soiffer
RJ
, et al.
Enasidenib as maintenance following allogeneic hematopoietic cell transplantation for IDH2-mutated myeloid malignancies
.
Blood Adv
.
2022
;
6
(
22
):
5857
-
5865
.
7.
DeFilipp
Z
,
Ancheta
R
,
Liu
Y
, et al.
Maintenance tyrosine kinase inhibitors following allogeneic hematopoietic stem cell transplantation for chronic myelogenous leukemia: a Center for International Blood and Marrow Transplant Research Study
.
Biol Blood Marrow Transplant
.
2020
;
26
(
3
):
472
-
479
.
8.
Brissot
E
,
Labopin
M
,
Beckers
MM
, et al.
Tyrosine kinase inhibitors improve long-term outcome of allogeneic hematopoietic stem cell transplantation for adult patients with Philadelphia chromosome positive acute lymphoblastic leukemia
.
Haematologica
.
2015
;
100
(
3
):
392
-
399
.
9.
Chen
H
,
Xu
L-P
,
Zhang
X-H
, et al.
Safety and outcomes of maintenance therapy with third-generation tyrosine kinase inhibitor after allogeneic hematopoietic cell transplantation in Philadelphia chromosome positive acute lymphoblastic leukemia patients with T315I mutation
.
Leuk Res
.
2022
;
121
:
106930
.
10.
Pasvolsky
O
,
Saliba
RM
,
Popat
UR
, et al.
Azacitidine posttransplant maintenance improves disease progression in high-risk acute myeloid leukemia and myelodysplastic syndrome
.
Clin Lymphoma Myeloma Leuk
.
2024
;
24
(
5
):
e196
-
e204
.
11.
Oran
B
,
de Lima
M
,
Garcia-Manero
G
, et al.
A phase 3 randomized study of 5-azacitidine maintenance vs observation after transplant in high-risk AML and MDS patients
.
Blood Adv
.
2020
;
4
(
21
):
5580
-
5588
.
12.
Kent
A
,
Schwartz
M
,
McMahon
C
, et al.
Venetoclax is safe and tolerable as posttransplant maintenance therapy for AML patients at high risk for relapse
.
Bone Marrow Transplant
.
2023
;
58
(
8
):
849
-
854
.
13.
Garcia
JS
,
Kim
HT
,
Murdock
HM
, et al.
Prophylactic maintenance with venetoclax/azacitidine after reduced-intensity conditioning allogeneic transplant for high-risk MDS and AML
.
Blood Adv
.
2024
;
8
(
4
):
978
-
990
.
14.
Metheny
LL
,
Sobecks
R
,
Cho
C
, et al.
A multicenter study of posttransplantation low-dose inotuzumab ozogamicin to prevent relapse of acute lymphoblastic leukemia
.
Blood Adv
.
2024
;
8
(
6
):
1384
-
1391
.
15.
Gaballa
MR
,
Banerjee
P
,
Milton
DR
, et al.
Blinatumomab maintenance after allogeneic hematopoietic cell transplantation for B-lineage acute lymphoblastic leukemia
.
Blood
.
2022
;
139
(
12
):
1908
-
1919
.
16.
Kennedy-Nasser
AA
,
Ku
S
,
Castillo-Caro
P
, et al.
Ultra low-dose IL-2 for GVHD prophylaxis after allogeneic hematopoietic stem cell transplantation mediates expansion of regulatory T cells without diminishing antiviral and antileukemic activity
.
Clin Cancer Res
.
2014
;
20
(
8
):
2215
-
2225
.
17.
Magenau
JM
,
Peltier
D
,
Riwes
M
, et al.
Type 1 interferon to prevent leukemia relapse after allogeneic transplantation
.
Blood Adv
.
2021
;
5
(
23
):
5047
-
5056
.
18.
Loke
J
,
McCarthy
N
,
Jackson
A
, et al.
Posttransplant MRD and T-cell chimerism status predict outcomes in patients who received allografts for AML/MDS
.
Blood Adv
.
2023
;
7
(
14
):
3666
-
3676
.
19.
Lindahl
H
,
Vonlanthen
S
,
Valentini
D
, et al.
Lineage-specific early complete donor chimerism and risk of relapse after allogeneic hematopoietic stem cell transplantation for acute myeloid leukemia
.
Bone Marrow Transplant
.
2022
;
57
(
5
):
753
-
759
.
20.
Dekker
SE
,
Rea
D
,
Cayuela
J-M
,
Arnhardt
I
,
Leonard
J
,
Heuser
M.
Using measurable residual disease to optimize management of AML, ALL, and chronic myeloid leukemia
.
Am Soc Clin Oncol Educ Book
.
2023
;
43
:
e390010
.
21.
Vago
L
,
Perna
SK
,
Zanussi
M
, et al.
Loss of mismatched HLA in leukemia after stem-cell transplantation
.
N Engl J Med
.
2009
;
361
(
5
):
478
-
488
.
22.
Crucitti
L
,
Crocchiolo
R
,
Toffalori
C
, et al.
Incidence, risk factors and clinical outcome of leukemia relapses with loss of the mismatched HLA after partially incompatible hematopoietic stem cell transplantation
.
Leukemia
.
2015
;
29
(
5
):
1143
-
1152
.
23.
Rautenberg
C
,
Bergmann
A
,
Germing
U
, et al.
Prediction of response and survival following treatment with azacitidine for relapse of acute myeloid leukemia and myelodysplastic syndromes after allogeneic hematopoietic stem cell transplantation
.
Cancers (Basel)
.
2020
;
12
(
8
).
24.
Craddock
C
,
Jilani
N
,
Siddique
S
, et al.
Tolerability and clinical activity of posttransplantation azacitidine in patients allografted for acute myeloid leukemia treated on the RICAZA trial
.
Biol Blood Marrow Transplant
.
2016
;
22
(
2
):
385
-
390
.
25.
Schroeder
T
,
Rachlis
E
,
Bug
G
, et al.
Treatment of acute myeloid leukemia or myelodysplastic syndrome relapse after allogeneic stem cell transplantation with azacitidine and donor lymphocyte infusions–a retrospective multicenter analysis from the German Cooperative Transplant Study Group
.
Biol Blood Marrow Transplant
.
2015
;
21
(
4
):
653
-
660
.
26.
Schroeder
T
,
Fröbel
J
,
Cadeddu
R-P
, et al.
Salvage therapy with azacitidine increases regulatory T cells in peripheral blood of patients with AML or MDS and early relapse after allogeneic blood stem cell transplantation
.
Leukemia
.
2013
;
27
(
9
):
1910
-
1913
.
27.
Krakow
EF
,
Walter
RB
,
Nathe
JM
, et al.
Intensive chemotherapy for acute myeloid leukemia relapse after allogeneic hematopoietic cell transplantation
.
Am J Hematol
.
2022
;
97
(
6
):
E220
-
E223
.
28.
Joshi
M
,
Cook
J
,
McCullough
K
, et al.
Salvage use of venetoclax-based therapy for relapsed AML post allogeneic hematopoietic cell transplantation
.
Blood Cancer J
.
2021
;
11
(
3
):
49
.
29.
Amit
O
,
On
YB
,
Perez
G
,
Shargian-Alon
L
,
Yeshurun
M
,
Ram
R.
Venetoclax and donor lymphocyte infusion for early relapsed acute myeloid leukemia after allogeneic hematopoietic cell transplantation. A retrospective multicenter trial
.
Ann Hematol
.
2021
;
100
(
3
):
817
-
824
.
30.
Schuler
E
,
Wagner-Drouet
E-M
,
Ajib
S
, et al
;
German Cooperative Transplant Study Group
.
Treatment of myeloid malignancies relapsing after allogeneic hematopoietic stem cell transplantation with venetoclax and hypomethylating agents-a retrospective multicenter analysis on behalf of the German Cooperative Transplant Study Group
.
Ann Hematol
.
2021
;
100
(
4
):
959
-
968
.
31.
Aldoss
I
,
Yang
D
,
Aribi
A
, et al.
Efficacy of the combination of venetoclax and hypomethylating agents in relapsed/refractory acute myeloid leukemia
.
Haematologica
.
2018
;
103
(
9
):
e404
-
e407
.
32.
DiNardo
CD
,
Jonas
BA
,
Pullarkat
V
, et al.
Azacitidine and venetoclax in previously untreated acute myeloid leukemia
.
N Engl J Med
.
2020
;
383
(
7
):
617
-
629
.
33.
Zucenka
A
,
Vaitekenaite
V
,
Maneikis
K
, et al.
Venetoclax-based salvage therapy followed by Venetoclax and DLI maintenance vs. FLAG-Ida for relapsed or refractory acute myeloid leukemia after allogeneic stem cell transplantation
.
Bone Marrow Transplant
.
2021
;
56
(
11
):
2804
-
2812
.
34.
Zuanelli Brambilla
C
,
Lobaugh
SM
,
Ruiz
JD
, et al.
Relapse after allogeneic stem cell transplantation of acute myelogenous leukemia and myelodysplastic syndrome and the importance of second cellular therapy
.
Transplant Cell Ther
.
2021
;
27
(
9
):
771.e1
-
771.e10
.
35.
Zhao
P
,
Ni
M
,
Ma
D
, et al.
Venetoclax plus azacitidine and donor lymphocyte infusion in treating acute myeloid leukemia patients who relapse after allogeneic hematopoietic stem cell transplantation
.
Ann Hematol
.
2022
;
101
(
1
):
119
-
130
.
36.
Schmidt
S
,
Liu
Y
,
Hu
Z-H
, et al.
The role of donor lymphocyte infusion (DLI) in post-hematopoietic cell transplant (HCT) relapse for chronic myeloid leukemia (CML) in the tyrosine kinase inhibitor (TKI) Era
.
Biol Blood Marrow Transplant
.
2020
;
26
(
6
):
1137
-
1143
.
37.
DiNardo
CD
,
Stein
EM
,
de Botton
S
, et al.
Durable remissions with ivosidenib in IDH1-mutated relapsed or refractory AML
.
N Engl J Med
.
2018
;
378
(
25
):
2386
-
2398
.
38.
Stein
EM
,
DiNardo
CD
,
Pollyea
DA
, et al.
Enasidenib in mutant IDH2 relapsed or refractory acute myeloid leukemia
.
Blood
.
2017
;
130
(
6
):
722
-
731
.
39.
Mathew
NR
,
Baumgartner
F
,
Braun
L
, et al.
Erratum: sorafenib promotes graft-versus-leukemia activity in mice and humans through IL-15 production in FLT3-ITD-mutant leukemia cells
.
Nat Med
.
2018
;
24
(
4
):
526
.
40.
Zhang
Z
,
Hasegawa
Y
,
Hashimoto
D
, et al.
Gilteritinib enhances graft-versus-leukemia effects against FLT3-ITD mutant leukemia after allogeneic hematopoietic stem cell transplantation
.
Bone Marrow Transplant
.
2022
;
57
(
5
):
775
-
780
.
41.
Xuan
L
,
Wang
Y
,
Chen
J
, et al.
Sorafenib therapy is associated with improved outcomes for FMS-like tyrosine kinase 3 internal tandem duplication acute myeloid leukemia relapsing after allogeneic hematopoietic stem cell transplantation
.
Biol Blood Marrow Transplant
.
2019
;
25
(
8
):
1674
-
1681
.
42.
De Freitas
T
,
Marktel
S
,
Piemontese
S
, et al.
High rate of hematological responses to sorafenib in FLT3-ITD acute myeloid leukemia relapsed after allogeneic hematopoietic stem cell transplantation
.
Eur J Haematol
.
2016
;
96
(
6
):
629
-
636
.
43.
Issa
GC
,
Aldoss
I
,
Thirman
MJ
, et al.
Menin inhibition with revumenib for KMT2A-rearranged relapsed or refractory acute leukemia (AUGMENT-101)
.
J Clin Oncol
.
2024
:
JCO2400826
.
44.
Issa
GC
,
Aldoss
I
,
DiPersio
J
, et al.
The menin inhibitor revumenib in KMT2A-rearranged or NPM1-mutant leukaemia
.
Nature
.
2023
;
615
(
7954
):
920
-
924
.
45.
Collins
RH
Jr
,
Shpilberg
O
,
Drobyski
WR
, et al.
Donor leukocyte infusions in 140 patients with relapsed malignancy after allogeneic bone marrow transplantation
.
J Clin Oncol
.
1997
;
15
(
2
):
433
-
444
.
46.
Biederstädt
A
,
Rezvani
K.
How I treat high-risk acute myeloid leukemia using preemptive adoptive cellular immunotherapy
.
Blood
.
2023
;
141
(
1
):
22
-
38
.
47.
Kharfan-Dabaja
MA
,
Labopin
M
,
Polge
E
, et al.
Association of second allogeneic hematopoietic cell transplant vs donor lymphocyte infusion with overall survival in patients with acute myeloid leukemia relapse
.
JAMA Oncol
.
2018
;
4
(
9
):
1245
-
1253
.
48.
Alkhaldi
H
,
Kharfan-Dabaja
M
,
El Fakih
R
,
Aljurf
M.
Safety and efficacy of immune checkpoint inhibitors after allogeneic hematopoietic cell transplantation
.
Bone Marrow Transplant
.
2023
;
58
(
10
):
1075
-
1083
.
49.
Sockel
K
,
Bornhaeuser
M
,
Mischak-Weissinger
E
, et al
;
German MDS and Cooperative Transplant Study Group (GCTSG)
.
Lenalidomide maintenance after allogeneic HSCT seems to trigger acute graft-versus-host disease in patients with high-risk myelodysplastic syndromes or acute myeloid leukemia and del(5q): results of the LENAMAINT trial
.
Haematologica
.
2012
;
97
(
9
):
e34
-
e35
.
50.
Craddock
C
,
Slade
D
,
De Santo
C
, et al.
Combination lenalidomide and azacitidine: a novel salvage therapy in patients who relapse after allogeneic stem-cell transplantation for acute myeloid leukemia
.
J Clin Oncol
.
2019
;
37
(
7
):
580
-
588
.
51.
Schroeder
T
,
Stelljes
M
,
Christopeit
M
, et al.
Azacitidine, lenalidomide and donor lymphocyte infusions for relapse of myelodysplastic syndrome, acute myeloid leukemia and chronic myelomonocytic leukemia after allogeneic transplant: the Azalena-trial
.
Haematologica
.
2023
;
108
(
11
):
3001
-
3010
.
52.
Posthuma
EF
,
Marijt
EW
,
Barge
RM
, et al.
Alpha-interferon with very-low-dose donor lymphocyte infusion for hematologic or cytogenetic relapse of chronic myeloid leukemia induces rapid and durable complete remissions and is associated with acceptable graft-versus-host disease
.
Biol Blood Marrow Transplant
.
2004
;
10
(
3
):
204
-
212
.
53.
Henden
AS
,
Varelias
A
,
Leach
J
, et al.
Pegylated interferon-2α invokes graft-versus-leukemia effects in patients relapsing after allogeneic stem cell transplantation
.
Blood Adv
.
2019
;
3
(
20
):
3013
-
3019
.
54.
Christopher
MJ
,
Petti
AA
,
Rettig
MP
, et al.
Immune escape of relapsed AML cells after allogeneic transplantation
.
N Engl J Med
.
2018
;
379
(
24
):
2330
-
2341
.
55.
Toffalori
C
,
Zito
L
,
Gambacorta
V
, et al.
Immune signature drives leukemia escape and relapse after hematopoietic cell transplantation
.
Nat Med
.
2019
;
25
(
4
):
603
-
611
.
56.
Matte-Martone
C
,
Liu
J
,
Zhou
M
, et al.
Differential requirements for myeloid leukemia IFN-γ conditioning determine graft-versus-leukemia resistance and sensitivity
.
J Clin Invest
.
2017
;
127
(
7
):
2765
-
2776
.
57.
Kharfan-Dabaja
MA
,
Reljic
T
,
Yassine
F
, et al.
Efficacy of a second allogeneic hematopoietic cell transplant in relapsed acute myeloid leukemia: results of a systematic review and meta-analysis
.
Transplant Cell Ther
.
2022
;
28
(
11
):
767.e1
-
767767.e11
.
58.
Ruutu
T
,
de Wreede
LC
,
van Biezen
A
, et al
;
European Society for Blood and Marrow Transplantation (EBMT)
.
Second allogeneic transplantation for relapse of malignant disease: retrospective analysis of outcome and predictive factors by the EBMT
.
Bone Marrow Transplant
.
2015
;
50
(
12
):
1542
-
1550
.
59.
Yerushalmi
Y
,
Shem-Tov
N
,
Danylesko
I
, et al.
Second hematopoietic stem cell transplantation as salvage therapy for relapsed acute myeloid leukemia/myelodysplastic syndromes after a first transplantation
.
Haematologica
.
2023
;
108
(
7
):
1782
-
1792
.
60.
Bazarbachi
A
,
Schmid
C
,
Labopin
M
, et al.
Evaluation of trends and prognosis over time in patients with AML relapsing after allogeneic hematopoietic cell transplant reveals improved survival for young patients in recent years
.
Clin Cancer Res
.
2020
;
26
(
24
):
6475
-
6482
.
61.
Christopeit
M
,
Kuss
O
,
Finke
J
, et al.
Second allograft for hematologic relapse of acute leukemia after first allogeneic stem-cell transplantation from related and unrelated donors: the role of donor change
.
J Clin Oncol
.
2013
;
31
(
26
):
3259
-
3271
.
62.
Imus
PH
,
Blackford
AL
,
Bettinotti
M
, et al.
Major histocompatibility mismatch and donor choice for second allogeneic bone marrow transplantation
.
Biol Blood Marrow Transplant
.
2017
;
23
(
11
):
1887
-
1894
.
63.
Shimoni
A
,
Labopin
M
,
Finke
J
, et al.
Donor selection for a second allogeneic stem cell transplantation in AML patients relapsing after a first transplant: a study of the Acute Leukemia Working Party of EBMT
.
Blood Cancer J
.
2019
;
9
(
12
):
88
.
64.
Aldoss
I
,
Khaled
SK
,
Wang
Y
, et al.
Donor-derived CD19-targeted chimeric antigen receptor T cells in adult transplant recipients with relapsed/refractory acute lymphoblastic leukemia
.
Blood Cancer J
.
2023
;
13
(
1
):
107
.
65.
Brudno
JN
,
Somerville
RP
,
Shi
V
, et al.
Allogeneic T cells that express an anti-CD19 chimeric antigen receptor induce remissions of B-cell malignancies that progress after allogeneic hematopoietic stem-cell transplantation without causing graft-versus-host disease
.
J Clin Oncol
.
2016
;
34
(
10
):
1112
-
1121
.
66.
Chapuis
AG
,
Egan
DN
,
Bar
M
, et al.
T cell receptor gene therapy targeting WT1 prevents acute myeloid leukemia relapse posttransplant
.
Nat Med
.
2019
;
25
(
7
):
1064
-
1072
.
67.
Lulla
PD
,
Naik
S
,
Vasileiou
S
, et al.
Clinical effects of administering leukemia- specific donor T cells to patients with AML/MDS after allogeneic transplant
.
Blood
.
2021
;
137
(
19
):
2585
-
2597
.
68.
Krakow
EF
,
Brault
M
,
Summers
C
, et al.
HA-1-targeted T cell receptor (TCR) T cell therapy for recurrent leukemia after hematopoietic stem cell transplantation
.
Blood
.
2024
:blood.2024024105.
69.
Guan
F
,
Yang
L
,
Chen
Y
, et al.
Comparison of long-term outcomes between imatinib and dasatinib prophylaxis after allogeneic stem cell transplantation in patients with Philadelphia-positive acute lymphoblastic leukemia: a multicenter retrospective study
.
Cancer
.
2024
;
130
(
12
):
2139
-
2149
.
70.
Cheng
Q
,
Tang
Y
,
Liu
F
,
Li
X
,
Fang
D.
Efficacy and safety in early application of Ruxolinitib for high-risk: acute lymphoblastic leukemia to prevent GVHD and recurrence after allogeneic hematopoietic stem cell transplantation
.
Transpl Immunol
.
2024
;
83
:
101978
.
71.
Fan
J
,
Lu
R
,
Zhu
J
, et al.
Effects of posttransplant maintenance therapy with decitabine prophylaxis on the relapse for acute lymphoblastic leukemia
.
Bone Marrow Transplant
.
2023
;
58
(
6
):
687
-
695
.
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