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Post-transplantation cyclophosphamide (PTCy) has been shown to effectively control graft-versus-host disease (GvHD) in haploidentical (Haplo) transplantations. In this retrospective registry study, we compared GvHD organ distribution, severity, and outcomes in patients with GvHD occurring after Haplo transplantation with PTCy GvHD prophylaxis (Haplo/PTCy) versus HLA-matched unrelated donor transplantation with conventional prophylaxis (MUD/conventional). We evaluated 2 cohorts: patients with grade 2 to 4 acute GvHD (aGvHD) including 264 and 1163 recipients of Haplo and MUD transplants; and patients with any chronic GvHD (cGvHD) including 206 and 1018 recipients of Haplo and MUD transplants, respectively. In comparison with MUD/conventional transplantation ± antithymocyte globulin (ATG), grade 3-4 aGvHD (28% versus 39%, P = .001), stage 3-4 lower gastrointestinal (GI) tract aGvHD (14% versus 21%, P = .01), and chronic GI GvHD (21% versus 31%, P = .006) were less common after Haplo/PTCy transplantation. In patients with grade 2-4 aGvHD, cGcHD rate after Haplo/PTCY was also lower (hazard ratio [HR] = .4, P < .001) in comparison with MUD/conventional transplantation without ATG in the nonmyeloablative conditioning setting. Irrespective of the use of ATG, non-relapse mortality rate was lower (HR = .6, P = .01) after Haplo/PTCy transplantation, except for transplants that were from a female donor into a male recipient. In patients with cGvHD, irrespective of ATG use, Haplo/PTCy transplantation had lower non-relapse mortality rates (HR = .6, P = .04). Mortality rate was higher (HR = 1.6, P = .03) within, but not after (HR = .9, P = .6) the first 6 months after cGvHD diagnosis. Our results suggest that PTCy-based GvHD prophylaxis mitigates the development of GI GvHD and may translate into lower GvHD-related non-relapse mortality rate.

Chronic graft vs. host disease (GVHD) treatment response is assessed using NIH Consensus criteria in clinical trials, and by clinician assessment in routine practice. Patient-reported treatment response is central to the experience of chronic GVHD manifestations as well as treatment benefit and toxicity, but how they correlate with clinician- or NIH-responses has not been well studied. We aimed to characterize 6-month patient-reported response, determine associated chronic GVHD baseline organ features and changes, and evaluate which patientreported quality of life and chronic GVHD symptom burden measures correlated with patientreported response. From two nationally representative Chronic GVHD Consortium prospective observational studies, 382 subjects were included in this analysis. Patient and clinician responses were categorized as improved (completely gone, very much better, moderately better, a little better) vs. not improved (about the same, a little worse, moderately worse, very much worse). At 6 months, 270 (71%) patients perceived chronic GVHD improvement, while 112 (29%) perceived no improvement. Patient-reported response had limited correlation with either clinician-reported (kappa 0.37) or NIH chronic GVHD response criteria (kappa 0.18). Notably, patient-reported response at 6 months was significantly associated with subsequent failure-free survival. In multivariate analysis, NIH responses in eye, mouth, and lung had significant association with 6-month patient-reported response, as well as a change in Short Form 36 general health and role physical domains and Lee Symptom Score skin and eye changes. Based on these findings, patient-reported responses should be considered as an important complementary endpoint in chronic GVHD clinical trials and drug development.

Key Points Variation in initial systemic therapy for chronic graft-versus-host disease includes varied prednisone dose and use of nonsteroid agents.Prospective trials are needed to verify efficacy of reduced-dose prednisone or prednisone-free initial therapy approaches., Visual Abstract, Prior clinical trials largely considered prednisone 1 mg/kg per day with or without calcineurin inhibitor as standard initial therapy for chronic graft-versus-host disease (cGVHD), but uncertainty remains regarding the extent of practice variation and whether this affects subsequent outcomes. We assembled a cohort of 745 patients with cGVHD treated with initial systemic immune suppressive (IS) therapy from 3 prior cGVHD Consortium observational studies. Initial therapy was defined as first IS therapy started for cGVHD or prednisone increased to ≥0.4 mg/kg per day from lower doses within 30 days before cGVHD diagnosis to any time afterward. Initial therapies were nonprednisone IS therapies (n = 137, 18%), prednisone alone (n = 411, 55%), or prednisone plus other IS therapy (n = 197, 26%). In multivariate analysis, initial therapy group was not associated with failure-free survival (FFS; a composite of death, relapse, and new IS therapy), overall survival (OS), or nonrelapse mortality (NRM). Among the prednisone-based approaches, steroid dose was 1.25 mg/kg per day (13%). Prednisone dose within the patients treated with steroids was not significantly associated with FFS, OS, or NRM. No significant interactions were detected between overall cGVHD severity and either initial therapy group or prednisone dose for the outcomes of FFS, OS, or NRM. These observational data document heterogeneity in more contemporary cGVHD initial treatment practices, including prednisone dose and use of nonsteroid approaches. This variation was not associated with FFS, OS, or NRM. Prospective trials are needed to verify efficacy of reduced-dose prednisone or prednisone-free initial therapy approaches.

Chronic graft-versus-host disease (cGVHD) is the leading cause of late morbidity and mortality after allogeneic hematopoietic cell transplantation. To better understand patients at highest risk for nonrelapse mortality (NRM), we analyzed patient-, transplant-, and cGVHD-related variables, risk factors, and causes of nonrelapse deaths in an updated cohort of 937 patients enrolled on 2 prospective, longitudinal observational studies through the Chronic GVHD Consortium. The median follow-up of survivors was 4 years (range, 0.1 months to 12.5 years). Relapse accounted for 25% of the 333 deaths. The cumulative incidence of NRM was 22% at 5 years, and it increased over time at a projected 40% (95% confidence interval, 30%-50%) at 12 years. Centers reported that cGVHD (37.8%) was the most common cause of NRM and was associated with organ failure, infection, or additional causes not otherwise specified. The next most frequent causes without mention of cGVHD were infection (17%) and respiratory failure (10%). In multivariable analysis, an increased risk for NRM was significantly associated with the use of reduced intensity conditioning, higher total bilirubin, National Institutes of Health (NIH) skin score of 2 to 3, NIH lung score of 1 to 3, worse modified Human Activity Profile adjusted activity score, and decreased distance on walk test. To summarize, cGVHD NRM does not plateau but increases over time and is most commonly attributed to GVHD or infection, presumably associated with immunocompromised status. Severe skin and lung cGVHD remain challenging manifestations associated with increased NRM, for which novel therapeutic options that do not predispose patients to infections are needed.

When multiple haploidentical donors are available for transplantation, those of younger generations are generally selected over those of older generations. However, it is unclear who is the optimal donor when selecting candidates from within a generation, such as father versus mother, son versus daughter, or brother versus sister. Although traditionally male donors are favored over female donors, particularly for male recipients, and significant associations of individual HLA mis(matches) on outcomes are being increasingly recognized, the hierarchy of factors for donor selection is indeterminate. To assess whether HLA factors take precedence over non-HLA factors and to isolate the influence of specific characteristics on outcomes, we analyzed 412 patients stratified by donor relationship: child donor (son [n = 202] versus daughter [n = 96]), parent (father [n = 28] versus mother [n = 29]), and sibling (noninherited maternal [NIMA; n = 29] versus paternal [NIPA; n = 28] mismatched). Among siblings, NIMA mismatch was associated with a lower risk of acute graft-versus-host disease (aGVHD); B-leader mismatch was associated with high nonrelapse mortality (NRM), poor progression-free survival, and a trend toward poor overall survival (OS), whereas A-mismatch was associated with lower aGVHD. Among parent donors, the relationship did not impact any outcome; B-leader mismatch was associated with higher NRM and a trend toward poor OS, whereas A-mismatch was associated with lower NRM and improved progression-free survival and OS. Among child donors, no individual HLA mismatch was predictive of any outcome, and daughter donors were not associated with any adverse outcomes in multivariate analyses. Our data suggest that certain HLA factors may be more significant in some cases and should be given priority over simply selecting a donor based on relationship/sex.

Positive results from recent clinical trials have significantly expanded current therapeutic options for patients with chronic graft-versus-host disease (GVHD). However, new insights into the associations between clinical characteristics of chronic GVHD, pathophysiologic mechanisms of disease, and the clinical and biological effects of novel therapeutic agents are required to allow for a more individualized approach to treatment. The current report is focused on setting research priorities and direction in the treatment of chronic GVHD. Detailed correlative scientific studies should be conducted in the context of clinical trials to evaluate associations between clinical outcomes and the biological effect of systemic therapeutics. For patients who require systemic therapy but not urgent initiation of glucocorticoids, clinical trials for initial systemic treatment of chronic GVHD should investigate novel agents as monotherapy without concurrently starting glucocorticoids, to avoid confounding biological, pathological, and clinical assessments. Clinical trials for treatment-refractory disease should specifically target patients with incomplete or suboptimal responses to most recent therapy who are early in their disease course. Close collaboration between academic medical centers, medical societies, and industry is needed to support an individualized, biology-based strategic approach to chronic GVHD therapy.

The incidence of graft-versus-host disease (GVHD) after cord blood (CB) transplantation (CBT) is lower than expected given the marked degree of human leukocyte antigen (HLA)-mismatch of CB grafts. While the exact mechanism that underlies this biology remains unclear, it is hypothesized to be due to the low number of mostly immature T-cells infused as part of the graft1,2, and increased tolerance of CB-derived lymphocytes induced by the state of pregnancy. Nevertheless, acute GVHD (aGVHD) is a significant complication of CBT. In contrast, the incidence of chronic GVHD (cGVHD) following CBT is lower than what is observed following matched related or unrelated donor HSC transplantation (HSCT)3-6. This review outlines the guidelines for the prevention and management of acute and chronic GVHD following CBT.

Clonal hematopoiesis (CH) is associated with older age and an increased risk of myeloid malignancies and cardiovascular complications. We analyzed donor DNA samples in patients with AML/MDS who underwent first allogeneic stem cell transplant (SCT) to investigate the association between donor CH and transplant outcomes. We performed targeted deep sequencing of 300 genes on donor blood samples and identified CH with the minimum variant allele frequency of 2%. Among 363 donors, 65 (18%) had CH. The most frequently mutated genes were DNMT3A (31 of 65; 48%), TET2 (16 of 65; 25%), PPM1D (5 of 65, 8%), and ASXL1 (7 of 65; 11%). Transplant outcomes: time to neutrophil and platelet recovery, relapse incidence, transplant-related mortality and progression-free survival, were comparable by donor CH. However, risk of grade II-IV and III-IV acute graft versus host disease (aGvHD) at 6 months after transplant was higher with donor CH vs. without donor CH (hazard ratio (HR) = 2.4, 95% Confidence Interval (CI) = 1.6-3.6, p < 0.001 and HR = 3.8, 95% CI = 1.6-8.9, p = 0.003). In this homogenous population of AML/MDS patients, donor CH was associated with increased risk of grade II-IV and III-IV aGvHD. Further studies to investigate the mechanisms of increased aGvHD and therapeutic interventions to improve aGvHD in the context of donor CH are warranted.

High-dose chemotherapy and autologous stem-cell transplant (HDC/ASCT) is standard treatment for chemosensitive relapsed classical Hodgkin lymphoma, although outcomes of high-risk relapse (HRR) patients remain suboptimal. We retrospectively analyzed all HRR classical Hodgkin lymphoma patients treated with HDC/ASCT at our institution between 01/01/2005 and 12/31/2019. HRR criteria included primary refractory disease/relapse within 1 year, extranodal extension, B symptoms, requiring more than one salvage line, or positron emission tomography (PET)-positive disease at ASCT. All patients met the same ASCT eligibility criteria. We treated 501 patients with BEAM (n=146), busulphan/melphalan (BuMel) (n=38), gemcitabine( Gem)/BuMel (n=189) and vorinostat/Gem/BuMel (n=128). The Gem/BuMel and vorinostat/Gem/BuMel cohorts had more HRR criteria and more patients with PET-positive disease at ASCT. Treatment with brentuximab vedotin (BV) or anti-PD1 prior to ASCT, PET-negative disease at ASCT, and maintenance BV increased over time. BEAM and BuMel predominated in earlier years (2005-2007), GemBuMel and BEAM in middle years (2008-2015), and vorinostat/GemBuMel and BEAM in later years (2016-2019). The median follow-up is 50 months (range, 6-186). Outcomes improved over time, with 2-year progressionfree survival (PFS)/overall survival (OS) rates of 58%/82% (2005-2007), 59%/83% (2008-2011), 71%/94% (2012-2015) and 86%/99% (2016- 2019) (P

Despite low nonrelapse mortality (NRM) at day 100 after allogeneic hematopoietic cell transplantation (HCT), NRM at 1 year remains substantial. In this study, we retrospectively analyzed 199 patients who were treated on a phase II clinical trial assessing safety and efficacy of myeloablative fractionated busulfan and fludarabine conditioning regimen for hematologic malignancies. The goal of the study was to identify factors associated with NRM occurring between days 101 and 365 post-HCT and generate a hypothesis for future studies to reduce the risk of NRM at 1 year. We found that a vast majority (83%) of patients who experienced NRM between days 101 and 365 had prior grade II-IV acute graft-versus-host disease (GVHD), which was the leading cause of death either by itself (33.3%) or complicated by infections (37.5%). In multivariate analysis, grade II-IV acute GVHD (hazard ratio (HR) 2.9, 95% confidence interval (CI) 1.3–6.6, p = 0.01) was the only significant predictor of NRM between days 101 and 365. Measures to reduce the risk of acute GVHD could lower the risk of NRM at 1 year and improve overall survival.

Steroids remain the initial therapy for acute graft-vs.-host disease (AGVHD). Strategies to improve response and minimize steroid exposure are needed. We report results of a randomized, adaptive, Bayesian-designed, phase II trial of prednisone with or without extracorporeal photopheresis (ECP) as an initial therapy for patients with newly diagnosed AGVHD. The primary endpoint was success at day 56 defined as: alive, in remission, achieving AGVHD response without additional therapy, and on

The use of post-transplantation cyclophosphamide (PTCy) for graft-versus-host disease (GVHD) prophylaxis is increasing in patients undergoing HLA-matched sibling (MSD) or unrelated (MUD) donor hematopoietic cell transplantation (HCT), but data about its comparative efficacy against the traditional GVHD prophylaxis are scarce. Two broad questions assessed in this study were (a) comparison of PTCy-based GVHD prophylaxis versus Tac/MTX (without ATG) in the MSD and (b) comparison of PTCy-based GVHD prophylaxis versus Tac/MTX (with ATG) in the MUD group. This retrospective single-center study analyzed the outcomes of 964 patients who received Tac/MTX (n = 578) versus PTCy-based (n = 386) GVHD prophylaxis. All MUD recipients in the Tac/MTX group also received ATG; thus separate analyses were conducted for MSD (n = 412) and MUD (n = 552) cohorts. In the MUD cohort, 306 patients received Tac/MTX/ATG and 246 received PTCy-based GVHD prophylaxis. In the MSD cohort, 272 received Tac/MTX and 140 received PTCy-based prophylaxis. Both PTCy groups included somewhat older patients than the Tac/MTX groups and more patients had myeloid malignancy (85%-90% versus 59%-64%, respectively). A majority of patients in all groups received myeloablative conditioning and peripheral blood graft. Both PTCy groups had a significantly delayed neutrophil engraftment, higher risk of hemorrhagic cystitis, and higher risk of bacterial infections than the Tac/MTX groups. The risks of viral infections and related deaths were significantly higher in Tac/MTX group in the MUD cohort. In multivariate analysis, the risk of grade III-IV acute GVHD was similar in PTCy and Tac/MTX groups in both MSD and MUD cohorts, but the risk of chronic GVHD was significantly lower with PTCy in the MSD cohort. PTCy was associated with a significantly lower risk of non-relapse mortality and better progression-free survival in the MUD. PTCy was associated with improved GVHD-free relapse-free survival in both MSD and MUD groups. Our data suggest a benefit of using PTCy-based GVHD prophylaxis in both MSD (versus Tac/MTX) and MUD (versus Tac/MTX/ATG) HCT.

This study investigated the efficacy and safety of azacitidine maintenance in the posttransplant setting based on the encouraging phase 1/2 reports for azacitidine maintenance in patients with acute myeloid leukemia/myelodysplastic syndrome (AML/MDS). Between 2009 and 2017, a total of 187 patients aged 18 to 75 years were entered into a randomized controlled study of posttransplant azacitidine if they were in complete remission. Patients randomized to the treatment arm (n = 93) were scheduled to receive azacitidine, given as 32 mg/m2 per day subcutaneously for 5 days every 28 days for 12 cycles. The control arm (n = 94) had no intervention. Eighty-seven of the 93 patients started azacitidine maintenance. The median number of cycles received was 4; a total of 29 patients relapsed on study, and 23 patients withdrew from the study due to toxicity, patient’s preference, or logistical reasons. Median relapse-free survival (RFS) was 2.07 years in the azacitidine group vs 1.28 years in the control group (P = .43). There was also no significant difference for overall survival, with a median of 2.52 years vs 2.56 years in the azacitidine and control groups (P = .85), respectively. Multivariate Cox regression analysis revealed no improvement in RFS or overall survival with the use of azacitidine as maintenance compared with the control group (hazard ratios of 0.73 [95% confidence interval, 0.49-1.1; P = .14] and 0.84 [95% confidence interval, 0.55-1.29; P = .43]). This randomized trial with azacitidine maintenance showed that a prospective trial in the posttransplant setting was feasible and safe but challenging. Although RFS was comparable between the 2 arms, we believe the strategy of maintenance therapy merits further study with a goal to reduce the risk of relapse in patients with AML/MDS. This trial was registered at www.clinicaltrials.gov as #NCT00887068.

How to best use tyrosine kinase inhibitors (TKIs) of BCR-ABL after allogeneic stem cell transplantation for Philadelphia chromosome–positive acute lymphoblastic leukemia (ALL) is unknown but will almost certainly not be addressed by a definitive randomized trial. Saini and colleagues provide a large body of observational data to reinforce earlier circumstantial evidence favoring prophylactic use of TKIs for at least 2 years posttransplant.

The optimal conditioning regimen for older patients with acute myeloid leukemia (AML) remains unclear. In this study, we compared outcomes of AML patients >60 years of age undergoing allogenic hematopoietic stem cell transplantation at our institution. All 404 consecutively treated patients received 1 of the following conditioning regimens: (1) fludarabine+melphalan 100 mg/m2 (FM100), (2) fludarabine+melphalan 140 mg/m2 (FM140), (3) fludarabine+IV busulfan AUC ≥ 5000/d × 4 d (Bu≥20000), and (4) fludarabine+IV busulfan AUC 4000/d × 4 d (Bu16000). A propensity score analysis (PSA) was used to compare outcomes between these 4 groups. Among the 4 conditioning regimens, the FM100 group had a significantly better long-term survival with 5-year progression-free survival of 49% vs 30%, 34%, and 23%, respectively. The benefit of the FM100 regimen resulted primarily from the lower nonrelapse mortality associated with this regimen, an effect more pronounced in patients with lower performance status. The PSA confirmed that FM100 was associated with better posttransplantation survival, whereas no significant differences were seen between the other regimen groups. In summary, older patients with AML benefited from a reduced-intensity conditioning regimen with lower melphalan doses (FM100), which was associated with better survival, even though it was primarily used in patients who could not receive a more intense conditioning regimen.

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a potentially curative therapy for hematologic malignancies. Alloreactivity after HSCT is known to be mediated by adaptive immune cells expressing rearranging receptors. Recent studies demonstrated that the innate immune system could likewise sense the non-self signals and subsequently enhance the alloimmune response. We recently demonstrated that the donor/recipient mismatch of signal regulatory protein α (SIRPα), an immunoglobulin receptor exclusively expressed on innate cells, is associated with a higher risk of cGVHD and relapse protection in a cohort of acute myeloid leukemia patients who underwent allo-HSCT. Whether these effects also occur in other hematologic malignancies remains unclear. In the present study, we compared outcomes by SIRPα match status in a cohort of 310 patients who received allo-HSCT from an HLA matched-related donor for the treatment of lymphoid malignancies. Multivariable analysis showed that SIRPα mismatch was associated with a significantly higher rate of cGVHD (hazard ratio [HR] 1.8, P= .002), cGVHD requiring systemic immunosuppressive therapy (HR 1.9, P= .005), a lower rate of disease progression (HR 0.5, P= .003) and improved progression-free survival (HR 0.5, P= .001). Notably, the effects of SIRPα mismatch were observed only in the patients who achieved >95% of donor T-cell chimerism. The mismatch in SIRPα is associated with favorable relapse protection and concurrently increased risk of cGVHD in patients who undergo allo-HSCT for lymphoid malignancies, and the optimal donor could be selected based on the finding of the study to mitigate the risk of GVHD and relapse.

Background CPX-351 is a liposomal formulation of cytarabine (araC) and daunorubicin at a fixed molar ratio that is currently approved for the treatment of patients with therapy-related AML or secondary AML (s-AML) arising from prior myelodysplastic syndrome (MDS). Compared to 7+3, CPX-351 demonstrated higher response rates (ORR), better tolerability, and better survival (OS) in patients with s-AML. The OS benefit was also observed after stem cell transplant (SCT). The dose-finding study of CPX-351 in R/R AML demonstrated an ORR of 23%. Recently, addition of the BCL-2 inhibitor venetoclax (Ven) to hypomethylating agents (HMAs) was shown to improve ORR and OS over HMAs alone. We designed this study to investigate the safety and efficacy of Ven combined with CPX-351 in patients with AML. Methods The dose of CPX-351 was constant: (daunorubicin 44 mg/m2 + araC 100 mg/m2) IV on D1,3,5 of induction and (daunorubicin 29 mg/m2 + araC 65 mg/m2) IV on D1,3 during consolidation. The starting effective dose of Ven was 300mg (at the -1 dose level) on D2-21 for the safety lead-in cohort, composed of patients with R/R AML. Interruption of Ven after D14 was allowed if a D14 bone marrow (BM) was hypocellular and without evidence of leukemia. Dose adjustments for Ven were made for concomitant moderate and strong CYP3A inhibitors. Upon encountering 3/6 patients with DLT (cytopenias >43 days), dose level -2 was explored (Ven 300mg on D2-8) and expanded. Once safety was confirmed, two expansions cohorts were opened to confirm safety and efficacy: Cohort A for pts with R/R AML and Cohort B for pts with newly diagnosed AML. Patients with adequate organ function, ECOG PS < 2 were allowed on study and prior Ven exposure was allowed. Results 18 patients have been treated on study, with a median age of 51 yrs (range, 29-71): 12 (67%) in the lead-in cohort, 5 (28%) in Cohort A and 1 (6%) in cohort B. Overall 17 (94%) had R/R AML with a median of 2 (1-8) prior therapies, and 1 (6%) patient with newly diagnosed treated-secondary AML. Patient characteristics are summarized in Table 1. Nine (50%) pts had adverse karyotype including 6 (33%) with complex karyotype and 6 (33%) with TP53 mutations; 7 (41%) pts with R/R AML had prior Ven. Outcomes are summarized in Table 1. The 1 pt with newly diagnosed AML (who had prior HMA+Ven and SCT for MDS) achieved an MRD (-) CR. Of 16 pts with R/R AML evaluable for response, there was 1 (6%) CR, 5 (31%) CRi, and 1 (6%) MLFS for an ORR of 44%. ORR was 60% (6/10) in pts without prior Ven exposure, compared to just 17% (1/6 evaluable) among those who had prior Ven. 86% of responding pts (6/7) went on for SCT. The median OS overall was 6.4 months with a 6m OS rate of 53% (Figure 1). Among responders, the median OS and RFS were NR and the 6m-OS and RFS were 86% and 86%, respectively (Figure 2). Figure 3 shows the OS of pts who did and did not receive prior Ven. The 4- and 8-week mortality rates were 11% and 22%, respectively. The starting dose level -1 was above the maximum tolerated dose of the combination; DLTs were prolonged neutropenia and thrombocytopenia. Serious adverse events are summarized in Table 2. The most frequent grade 3/4 serious adverse events were infection, nausea, pneumonia, and myelosuppression. Conclusion CPX-351 plus 7 days of Ven is tolerable, with acceptable toxicities in patients with R/R AML. Within this high risk AML cohort, CPX + Ven demonstrated encouraging activity, particularly in those who had not received prior Ven. Almost all responders were able to move on to SCT. The study continues to enroll relapsed and frontline cohorts. Disclosures Kadia: Astellas: Research Funding; Celgene: Research Funding; Pulmotec: Research Funding; Astra Zeneca: Research Funding; Novartis: Honoraria; Incyte: Research Funding; Cellenkos: Research Funding; Ascentage: Research Funding; Amgen: Research Funding; BMS: Honoraria, Research Funding; Cyclacel: Research Funding; Pfizer: Honoraria, Research Funding; JAZZ: Honoraria, Research Funding; Genentech: Honoraria, Research Funding; Abbvie: Honoraria, Research Funding. Borthakur:PTC Therapeutics: Research Funding; Incyte: Research Funding; Novartis: Research Funding; Abbvie: Research Funding; Jannsen: Research Funding; GSK: Research Funding; Cyclacel: Research Funding; BioLine Rx: Research Funding; BMS: Research Funding; AstraZeneca: Research Funding; Polaris: Research Funding; Xbiotech USA: Research Funding; Oncoceutics: Research Funding; Curio Science LLC: Consultancy; FTC Therapeutics: Consultancy; Argenx: Consultancy; PTC Therapeutics: Consultancy; BioLine Rx: Consultancy; BioTherix: Consultancy; Nkarta Therapeutics: Consultancy; Treadwell Therapeutics: Consultancy. DiNardo:Daiichi Sankyo: Consultancy, Honoraria, Research Funding; Agios: Consultancy, Honoraria, Research Funding; Jazz: Honoraria; Takeda: Honoraria; Syros: Honoraria; Novartis: Consultancy; Celgene: Consultancy, Honoraria, Research Funding; MedImmune: Honoraria; Notable Labs: Membership on an entity's Board of Directors or advisory committees; Calithera: Research Funding; ImmuneOnc: Honoraria; AbbVie: Consultancy, Honoraria, Research Funding. Daver:Bristol-Myers Squibb: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Karyopharm: Research Funding; Servier: Research Funding; Genentech: Research Funding; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novimmune: Research Funding; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Trovagene: Research Funding; Fate Therapeutics: Research Funding; ImmunoGen: Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Jazz: Consultancy, Membership on an entity's Board of Directors or advisory committees; Trillium: Consultancy, Membership on an entity's Board of Directors or advisory committees; Syndax: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; KITE: Consultancy, Membership on an entity's Board of Directors or advisory committees; Agios: Consultancy, Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Pemmaraju:Pacylex Pharmaceuticals: Consultancy; MustangBio: Honoraria; DAVA Oncology: Honoraria; Samus Therapeutics: Research Funding; Cellectis: Research Funding; Affymetrix: Other: Grant Support, Research Funding; Roche Diagnostics: Honoraria; Incyte Corporation: Honoraria; SagerStrong Foundation: Other: Grant Support; AbbVie: Honoraria, Research Funding; Daiichi Sankyo: Research Funding; LFB Biotechnologies: Honoraria; Celgene: Honoraria; Blueprint Medicines: Honoraria; Novartis: Honoraria, Research Funding; Stemline Therapeutics: Honoraria, Research Funding; Plexxikon: Research Funding. Jabbour:Adaptive Biotechnologies: Other: Advisory role, Research Funding; AbbVie: Other: Advisory role, Research Funding; Takeda: Other: Advisory role, Research Funding; BMS: Other: Advisory role, Research Funding; Genentech: Other: Advisory role, Research Funding; Pfizer: Other: Advisory role, Research Funding; Amgen: Other: Advisory role, Research Funding. Jain:Genentech: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Research Funding; AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Incyte: Research Funding; BeiGene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Servier: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Adaptive Biotechnologies: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Research Funding; Verastem: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Aprea Therapeutics: Research Funding; Precision Bioscienes: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; ADC Therapeutics: Research Funding; TG Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Fate Therapeutics: Research Funding; Pharmacyclics: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Cellectis: Research Funding; AstraZeneca: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Short:Takeda Oncology: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy; Amgen: Honoraria; Astellas: Research Funding. Alvarado:MEI Pharma: Research Funding; BerGenBio ASA: Research Funding; Tolero Pharmaceuticals: Research Funding; Daiichi-Sankyo: Research Funding; Astex Pharmaceuticals: Research Funding; FibroGen: Research Funding; Sun Pharma: Research Funding; Jazz Pharmaceuticals: Research Funding. Alousi:Therakos: Research Funding; Alexion: Honoraria; Incyte: Honoraria, Research Funding. Popat:Bayer: Research Funding; Novartis: Research Funding. Khouri:Pfizer: Research Funding; Bristol Myers Squibb: Research Funding. Garcia-Manero:Merck: Research Funding; Astex Pharmaceuticals: Consultancy, Honoraria, Research Funding; H3 Biomedicine: Research Funding; AbbVie: Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Helsinn Therapeutics: Consultancy, Honoraria, Research Funding; Amphivena Therapeutics: Research Funding; Jazz Pharmaceuticals: Consultancy; Acceleron Pharmaceuticals: Consultancy, Honoraria; Onconova: Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Novartis: Research Funding. Konopleva:Agios: Research Funding; Stemline Therapeutics: Consultancy, Research Funding; Reata Pharmaceutical Inc.;: Patents & Royalties: patents and royalties with patent US 7,795,305 B2 on CDDO-compounds and combination therapies, licensed to Reata Pharmaceutical; Eli Lilly: Research Funding; Sanofi: Research Funding; AstraZeneca: Research Funding; Amgen: Consultancy; Rafael Pharmaceutical: Research Funding; F. Hoffmann La-Roche: Consultancy, Research Funding; Ablynx: Research Funding; Kisoji: Consultancy; Genentech: Consultancy, Research Funding; AbbVie: Consultancy, Research Funding; Ascentage: Research Funding; Cellectis: Research Funding; Forty-Seven: Consultancy, Research Funding; Calithera: Research Funding. Cortes:Daiichi Sankyo: Consultancy, Research Funding; Astellas: Research Funding; Amphivena Therapeutics: Research Funding; Arog: Research Funding; BiolineRx: Consultancy, Research Funding; Bristol-Myers Squibb: Research Funding; Merus: Research Funding; Telios: Research Funding; BioPath Holdings: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Sun Pharma: Research Funding; Takeda: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Immunogen: Research Funding; Jazz Pharmaceuticals: Consultancy, Research Funding. Ravandi:BMS: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria; Orsenix: Consultancy, Honoraria, Research Funding; Astellas: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy, Honoraria; Jazz Pharmaceuticals: Consultancy, Honoraria, Research Funding; Xencor: Consultancy, Honoraria, Research Funding; Macrogenics: Research Funding; Abbvie: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding. Kantarjian:Amgen: Honoraria, Research Funding; Daiichi-Sankyo: Research Funding; Novartis: Research Funding; Agios: Honoraria, Research Funding; AbbVie: Honoraria, Research Funding; BMS: Research Funding; Pfizer: Honoraria, Research Funding; Ariad: Research Funding; Cyclacel: Research Funding; Actinium: Honoraria, Membership on an entity's Board of Directors or advisory committees; Astex: Research Funding; Jazz Pharma: Research Funding; Immunogen: Research Funding; Takeda: Honoraria. OffLabel Disclosure: CPX-351 is not indicated in combination with venetoclax nor for patients with relapsed AML. This trials describes and investigational use.

Background: Myeloablative conditioning can be given safely to older patients by simply administering busulfan over a longer period (fractionated busulfan regimen) than the standard four-day regimen (Popat et al Lancet Haematology 2018). This longer duration of conditioning regimen allows addition of targeted agents like Venetoclax, which may be synergistic with conditioning chemotherapy and may further improve disease control with this regimen. We therefore added Venetoclax to our ongoing prospective clinical trial with f-Bu-Flu-Cladribine conditioning (NCT02250937). After enrolling 83 patients, the study was amended and venetoclax was added for the next 33 patients. Here we report the safety and preliminary efficacy of venetoclax and fractionated busulfan regimen. Methods: Between 2/2019 and 3/2021, 33 patients with AML (n=21) or MDS (n=10) up to 70 years of age with adequate organ function and 8/8-HLA matched related or unrelated donor were enrolled on a prospective trial. The conditioning regimen was f-Bu to target an area under the concentration vs time curve (AUC) of 20,000 ± 12% μmol.min given over a period of 2-3 weeks. The first two doses of busulfan (80 mg/m2 IV each) were administered either consecutively (days -13 and -12) or with further fractionation, one week apart (days -20 and -13) on outpatient basis. Then, inpatient fludarabine 10 mg/m 2, and cladribine 10 mg/m 2 were given followed by Bu on days -6 to -3. Venetoclax 400mg daily was given from day -22 to -3. Azoles were avoided during this period. GVHD prophylaxis was PTCy 50mg/kg on days 3 and 4 and tacrolimus from day 5. Results: The median age was 59 years (range, 23-69); High or very high disease risk index was present in 21%; Comorbidity index score of >3 was present in 45%; Donor was a sibling in 39%; and peripheral blood stem cells was the graft source in 100%. The median follow up was 8 months. At 1-year, overall survival was 84% (95% confidence interval, 71-100), progression-free survival 77% (64-94), relapse 13% (1-25), and non-relapse mortality 10% (0-20) [Table 1, Figure 1]. Incidence of acute GVHD grade 2-4 was 28% (12-43) and grade 3-4 acute GVHD was 3% (0-9) at day 100. All patients engrafted. The median time to neutrophil engraftment was 15 days (13 -19) and median time to platelet engraftment was 23 days (11-85). Full donor chimerism at day 30 was noted in 76%. Common grade 3 or 4 toxicity were neutropenic fever (58%), mucositis (18%) and pulmonary toxicity in 21%. Conclusion: Venetoclax can be safely added to the fractionated busulfan regimen. Early data on efficacy appear promising. Figure 1 Figure 1. Disclosures Popat: Bayer: Research Funding; Abbvie: Research Funding; Novartis: Research Funding; Incyte: Research Funding. Mehta: CSLBehring: Research Funding; Syndax: Research Funding; Incyte: Research Funding; Kadmon: Research Funding. Hosing: Nkarta Therapeutics: Membership on an entity's Board of Directors or advisory committees. Gulbis: EUSA Pharma: Other: Advisory board participation. Rezvani: AvengeBio: Other: Scientific Advisory Board ; Pharmacyclics: Other: Educational grant, Research Funding; GemoAb: Other: Scientific Advisory Board ; Navan Technologies: Other: Scientific Advisory Board; Bayer: Other: Scientific Advisory Board ; Caribou: Other: Scientific Advisory Board; Takeda: Other: License agreement and research agreement, Patents & Royalties; Virogin: Other: Scientific Advisory Board ; GSK: Other: Scientific Advisory Board ; Affimed: Other: License agreement and research agreement; education grant, Patents & Royalties, Research Funding. Qazilbash: Bristol-Myers Squibb: Other: Advisory Board; Oncopeptides: Other: Advisory Board; Amgen: Research Funding; Angiocrine: Research Funding; NexImmune: Research Funding; Biolline: Research Funding; Janssen: Research Funding. Kadia: Cure: Speakers Bureau; Novartis: Consultancy; Dalichi Sankyo: Consultancy; Cellonkos: Other; Ascentage: Other; Genfleet: Other; Sanofi-Aventis: Consultancy; Genentech: Consultancy, Other: Grant/research support; Astellas: Other; Liberum: Consultancy; BMS: Other: Grant/research support; Amgen: Other: Grant/research support; Aglos: Consultancy; Pfizer: Consultancy, Other; AstraZeneca: Other; AbbVie: Consultancy, Other: Grant/research support; Pulmotech: Other; Jazz: Consultancy. Konopleva: Calithera: Other: grant support, Research Funding; AbbVie: Consultancy, Honoraria, Other: Grant Support, Research Funding; Ascentage: Other: grant support, Research Funding; Cellectis: Other: grant support; Ablynx: Other: grant support, Research Funding; Agios: Other: grant support, Research Funding; Rafael Pharmaceuticals: Other: grant support, Research Funding; Eli Lilly: Patents & Royalties: intellectual property rights, Research Funding; AstraZeneca: Other: grant support, Research Funding; Stemline Therapeutics: Research Funding; F. Hoffmann-La Roche: Consultancy, Honoraria, Other: grant support; Forty Seven: Other: grant support, Research Funding; Sanofi: Other: grant support, Research Funding; Genentech: Consultancy, Honoraria, Other: grant support, Research Funding; Novartis: Other: research funding pending, Patents & Royalties: intellectual property rights; Reata Pharmaceuticals: Current holder of stock options in a privately-held company, Patents & Royalties: intellectual property rights; KisoJi: Research Funding. Shpall: Axio: Consultancy; Magenta: Consultancy; Novartis: Consultancy; Bayer HealthCare Pharmaceuticals: Honoraria; Adaptimmune: Consultancy; Navan: Consultancy; Takeda: Patents & Royalties; Novartis: Honoraria; Affimed: Patents & Royalties; Magenta: Honoraria.