Kebriaei, Partow

Abstract The cumulative impact of baseline comorbidities on outcomes of chimeric antigen receptor T-cell (CAR-T) therapy is not well established. Therefore, we developed and validated a Cellular Therapy Comorbidity Index (CT-CI) to predict outcomes following CD19-directed CAR-T therapy for large B-cell lymphoma (LBCL). Patients aged 18 or older receiving commercial CAR-T therapy for LBCL during 2017 to 2020 were selected from the Center for International Blood and Marrow Transplant Research registry. Patients were randomly assigned to training or validation cohorts. Comorbidities given weighted scores comprised the CT-CI, which was then validated for overall survival (OS) prognostication. A total of 1916 patients from 97 medical centers were included, with a median age of 64 years (19-91 years). About 70% of patients had comorbidities, such as cardiac disease (12%); diabetes (14%); hepatic dysfunction (mild, 8%; moderate to severe, 2%); psychiatric disturbance (18%); and pulmonary dysfunction (moderate, 15%; severe, 12%). The CT-CI was calculated, stratified patients in 3 categories, and was associated with increased mortality. Patients with higher CT-CI scores had worse OS (CT-CI 1: hazard ratio [HR], 1.37 [95% confidence interval [CI], 1.16-1.62; P< .001]; CT-CI 2: HR, 1.49 [95% CI, 1.17-1.89; P = .001]; CT-CI ≥ 3: HR, 2.55 [95% CI, 1.90-3.42; P< .001]). Higher CT-CI scores predicted treatment-related mortality and relapse. There was no correlation between the CT-CI score and CAR-T–related toxicities. The novel CT-CI score stratifies the effect of patient comorbidities on survival after CAR-T therapy and can be used for clinical decision-making and treatment selection in high-risk populations. However, comorbidities and fear of increased toxicity should not preclude patients from this effective therapy.

Introduction: NPM1 mutations, seen in up to 30% of adults with acute myeloid leukemia (AML), often co-occur with FLT3 internal tandem duplication (FLT3-ITD). Measurable residual disease (MRD) testing before allogeneic hematopoietic cell transplant (alloHCT) for persistence of mutated NPM1 and/or FLT3-ITD can identify patients with AML in complete remission (CR) at highest risk of relapse and death. Quantitative RT-PCR assays are currently recommended for NPM1 MRD testing, while FLT3-ITD MRD testing is DNA-based using next generation sequencing (NGS). DNA-based NGS assays for mutated NPM1 MRD testing may have several advantages but require validation. We performed NPM1 MRD detection in blood collected from patients with AML during first CR (CR1) prior to alloHCT on a subset of patients from the Pre-MEASURE study (PMID: 36881031) using a highly-sensitive, commercially available DNA-based NPM1 NGS MRD assay. Methods: Of the 531 patients aged 18 or older from the Pre-MEASURE study who received an alloHCT for NPM1mutated AML during CR1 at a CIBMTR reporting site in the USA between the years of 2013-2019, a subset of 190 were randomly selected to be included in this analysis. A commercially available research testing kit (IVS, Invivoscribe, San Diego, CA), which can detect DNA-based NPM1 MRD, was used to establish a workflow following clinical testing standards and validated to detect NPM1 insertion variants down to a variant allele fraction (VAF) of at least 0.005%. Results were compared to those previously reported using an anchored multiplex PCR-based (AMP) targeted NGS assay (detection limit 0.01%) and FLT3-ITD MRD results, where applicable. Overall survival (OS) and cumulative incidence of relapse were estimated with the day of transplant as time 0 using Kaplan-Meier estimation (log-rank tests), Fine and Gray model, and Cox proportional hazards models. Results: NPM1 NGS MRD testing was successful for 186 (98%) patients, of which 48 (26%) relapsed (median: 4.0 months; range: 0.7-52.5) and 64 (34%) died (median: 9.7 months; range: 0.4-58.9) post-alloHCT. The IVS assay detected NPM1 insertion variants in 71 patients with a median VAF of 0.0026% (range:0.0002-2.1%). Using a VAF threshold of ≥0.01% for MRD positivity, the IVS test showed that 24 patients tested positive for NPM1 MRD pre-alloHCT, which was associated with significantly increased rates of relapse (52% vs 20% at 3yrs; HR=4.3; P<0.001) and decreased OS (34% vs 71% at 3yrs; HR=3.6; P<0.001) compared to testing negative, in close alignment with those previously reported using the AMP assay. After removing the VAF threshold, an additional 47 patients were classified as NPM1 MRD positive, which remained associated with increased rates of relapse (40% vs 15% at 3yrs; HR=3.4; P<0.001) and decreased OS (50% vs 75% at 3yrs; HR=2.9; P<0.001). In multivariable analysis, residual NPM1 MRD burden prior to alloHCT was associated with risk of relapse and death in a dose-dependent manner. Patients were further subdivided based on their reported FLT3-ITD mutational status at baseline. Increased risk of relapse was seen for NPM1 MRD positive patients regardless of baseline FLT3-ITD. 123 (66%) patients were co-mutated for FLT3-ITD at baseline and previously tested for FLT3-ITD MRD using the IVS assay (PMID: 38696205). Defining MRD based on the presence of NPM1 vs NPM1 and/or FLT3-ITD revealed equivalent levels of relapse (45% vs 44%) and OS (45% vs 46%) at 3 years, with NPM1 MRD evaluation identifying 5 additional relapses. These results were confirmed in the full Pre-MEASURE cohort (n=317) using the AMP assay. NPM1 MRD positive patients receiving nonmyeloablative conditioning or reduced-intensity conditioning (RIC) without melphalan (mel) had increased risk of relapse or death compared to patients receiving myeloablative conditioning or RIC with mel, regardless of FLT3-ITD co-mutational status (3yrs: relapse 87% vs 55%, P=0.006; OS 15% vs 42%, P=0.013). Conclusions: In patients with NPM1 mutated AML from the Pre-MEASURE study, we show that detection of residual NPM1 variants in pre-transplant blood during CR1 using a highly sensitive DNA-based assay is associated in a dose-dependent manner with a significantly increased risk of relapse and death after allo-HCT, which can be mitigated in part by conditioning regimen. In patients co-mutated for both FLT3-ITD and NPM1 at diagnosis, NPM1 should be prioritized as a target for NGS-MRD if only one test is available.

PURPOSE Older patients with relapsed or refractory AML (RR AML) have dismal prognoses without allogeneic hematopoietic cell transplantation (alloHCT). SIERRA compared a targeted pretransplant regimen involving the anti-CD45 radioconjugate 131 I-apamistamab with conventional care. METHODS SIERRA (ClinicalTrials.gov identifier: NCT02665065 ) was a phase III open-label trial. Patients age ≥55 years with active RR AML were randomly assigned 1:1 to either an 131 I-apamistamab–led regimen before alloHCT or conventional care followed by alloHCT if initial complete remission (CR)/CR with incomplete platelet recovery (CRp) occurred. Initial response was assessed 28-56 days after alloHCT in the 131 I-apamistamab group and 28-42 days after salvage chemotherapy initiation; patients without CR/CRp or with AML progression could cross over to receive 131 I-apamistamab followed by alloHCT. The primary end point was durable complete remission (dCR) lasting 180 days after initial CR/CRp. Secondary end points were overall survival (OS) and event-free survival (EFS), assessed hierarchically in the intention-to-treat (ITT) population. RESULTS The ITT population included 153 patients ( 131 I-apamistamab [n = 76]; conventional care [n = 77]). In total, 44/77 conventional care arm patients crossed over and 40/77 (52%) received 131 I-apamistamab and alloHCT, with six patients (13.6%) experiencing a dCR. In the ITT population, the dCR rate was significantly higher with 131 I-apamistamab (17.1% [95% CI, 9.4 to 27.5]) than conventional care (0% [95% CI, 0 to 4.7]; P < .0001). The OS hazard ratio (HR) was 0.99 (95% CI, 0.70 to 1.41; P = .96), and the EFS HR was 0.23 (95% CI, 0.15 to 0.34), with HR <1 favoring 131 I-apamistamab. Grade ≥3 treatment-related adverse events occurred in 59.7% and 59.2% of the 131 I-apamistamab and conventional care groups, respectively. CONCLUSION The 131 I-apamistamab–led regimen was associated with a higher dCR rate than conventional care in older patients with RR AML. 131 I-apamistamab was well tolerated and could address an unmet need in this population.

ImportancePersistence of FLT3 internal tandem duplication (ITD) in adults with acute myeloid leukemia (AML) in first complete remission (CR) prior to allogeneic hematopoietic cell transplant (HCT) is associated with increased relapse and death after transplant, but the association between the level of measurable residual disease (MRD) detected and clinical outcome is unknown.ObjectiveTo examine the association between pre–allogeneic HCT MRD level with relapse and death posttransplant in adults with AML in first CR.Design, Setting, and ParticipantsIn this cohort study, DNA sequencing was performed on first CR blood from patients with FLT3-ITD AML transplanted from March 2013 to February 2019. Clinical follow-up was through May 2022. Data were analyzed from October 2022 to December 2023.ExposureCentralized DNA sequencing for FLT3-ITD in pre–allogeneic HCT first CR blood using a commercially available kit.Main Outcomes and MeasuresThe primary outcomes were overall survival and cumulative incidence of relapse, with non–relapse-associated mortality as a competing risk post–allogeneic HCT. Kaplan-Meier estimations (log-rank tests), Cox proportional hazards models, and Fine-Gray models were used to estimate the end points.ResultsOf 537 included patients with FLT3-ITD AML from the Pre-MEASURE study, 296 (55.1%) were female, and the median (IQR) age was 55.6 (42.9-64.1) years. Using the variant allele fraction (VAF) threshold of 0.01% or greater for MRD positivity, the results closely aligned with those previously reported. With no VAF threshold applied (VAF greater than 0%), 263 FLT3-ITD variants (median [range] VAF, 0.005% [0.0002%-44%]), and 177 patients (33.0%) with positive findings were identified. Multivariable analyses showed that residual FLT3-ITD was the variable most associated with relapse and overall survival, with a dose-dependent correlation. Patients receiving reduced-intensity conditioning without melphalan or nonmyeloablative conditioning had increased risk of relapse and death at any given level of MRD compared with those receiving reduced-intensity conditioning with melphalan or myeloablative conditioning.Conclusions and RelevanceThis study provides generalizable and clinically applicable evidence that the detection of residual FLT3-ITD in the blood of adults in first CR from AML prior to allogeneic HCT is associated with an increased risk of relapse and death, particularly for those with a VAF of 0.01% or greater. While transplant conditioning intensification, an intervention not available to all, may help mitigate some of this risk, alternative approaches will be necessary for this high-risk population of patients who are underserved by the current standard of care.

Background : Allogeneic hematopoietic cell transplant (alloHCT) is the only potentially curative therapy for patients (pts) with relapsed or refractory (R/R) AML. Only a minority undergo alloHCT as they typically have dismal outcomes due to high relapse rates, especially those with TP53 mutations and active disease. Additionally, older pts cannot tolerate intensive treatment and hence are not eligible for alloHCT. 131I-apamistamab, an anti-CD45 radioimmunoconjugate, delivers high dose targeted radiation to hematopoietic cells, allowing for myeloablation and eradication of leukemic cells. 131I-apamistamab led induction and conditioning can thus provide these pts access to alloHCT potentially leading to better disease control and outcomes even in pts with the TP53 mutation. Methods: The SIERRA trial (NCT02665065) is a multi-center, randomized, controlled Phase 3 study comparing the rate of durable complete remission (dCR) lasting ≥6 months (mos) after complete remission with/without platelet recovery (CR/CRp) between two groups: 131I-apamistamab led induction and conditioning followed by alloHCT vs physician's choice of conventional care (CC). Pts were randomized (1:1) to CC or 131I-apamistamab with fludarabine and total body irradiation (2 Gy) followed by alloHCT. CR/CRp assessment was 28-56 days post alloHCT or 28-42 days post initiation of therapy in the CC group. Pts in the CC group not achieving leukemia-free state could crossover (CO) to 131I-apamistamab. We report the characteristics and outcomes of all pts with TP53 mutation who were enrolled in the SIERRA trial. Results: In total, 153 pts were randomized (CC, n=77; 131I-apamistamab, n=76). All pts who received the therapeutic dose of 131I-apamistamab (n=66) underwent HCT vs 14 (18.2%) in the CC group. Of evaluable pts, dCR rates at 6 months were 22% in the 131I-apamistamab group vs 0% in the CC group (95% CI;12.29, 34.73; p&lt;0.0001). A total of 37 pts with TP53 mutation were enrolled (CC=20; 131I-apamistamab =17) with a prevalence of 24.2%. Table 1 shows the baseline characteristics of these pts. Median overall survival (OS) for pts in the 131I-apamistamab group, who were TP53 negative was 6.37 mos compared to 5.72 mos for the TP53 mutation positive pts (HR=0.66; 95% CI [0.37, 1.18]; p=0.16). In the CC group (including CO pts), the median OS for TP53 positive pts was 2.96 mos. When the CC group without CO were analyzed, the median OS was 6.51 mos and 1.66 mos for the TP53 mutation negative and positive groups respectively (HR=0.28; 95% CI [0.12, 0.67]; p=0.0022). For TP53 mutation positive pts who received 131I-apamistamab ( 131I-apamistamab plus CO pts), the median OS was 5.49 mos compared to a median 1.66 mos in pts who did not receive 131I-apamistamab (CC pts without CO) [(HR=0.23; 95% CI [0.10, 0.52]; p=0.0002) (Figure 1)]. Conclusion: Pts with TP53 mutated R/R AML have a dismal prognosis and are seldom offered alloHCT due to high post-transplant relapse rates. 131I-apamistamab led alloHCT significantly improves survival outcomes in pts with TP53 mutations, commensurate with rates observed in pts with wildtype TP53, thereby overcoming the negative impact of this mutation. These data clearly support the use of 131I-apamistamab led induction and conditioning and alloHCT in R/R AML, including in patients with a TP53 mutation.

Background: Most older patients (pts) with relapsed or refractory (R/R) AML cannot tolerate intensive treatment and are not eligible for curative allogeneic hematopoietic cell transplant (alloHCT). 131I-apamistamab, an anti-CD45 radioimmunoconjugate, delivers high dose targeted radiation to hematopoietic cells, allowing for myeloablation and eradication of leukemic cells. 131I-apamistamab led induction and conditioning can provide these pts with access to alloHCT. Methods: SIERRA (NCT02665065) was a multi-center, randomized, controlled phase 3 study comparing the efficacy of 131I-apamistamab led induction and conditioning versus physician's choice of conventional care (CC) in pts ≥55 years of age with active, R/R AML. Pts were randomized (1:1, n=153) to CC or 131I-apamistamab with fludarabine and total body irradiation (2 Gy) followed by alloHCT. Primary endpoint was durable complete remission (dCR), defined as CR ≥6 mos with or without platelet recovery (CRp). Pts not achieving CR in CC could crossover (CO) to receive 131I-apamistamab. Treatment with 131I-apamistamab was prescribed as an individualized dose for each pt following a dosimetric infusion and biodistribution analysis, with the prescribed activity of 131I set to deliver a maximum estimated radiation dose to the liver as the dose limiting organ of 24 Gy (determined as the maximum tolerable dose (MTD)) in earlier studies), thereby providing the highest dose to the diseased bone marrow and circulating leukemic cells without exceeding individual organ radiation dose tolerances. Here, we performed an analysis to determine whether a radiation dose-response relationship could be established based on either 1) administered radiation dose to liver and the rate of achieving the primary endpoint of dCR (with 95% binomial confidence intervals) or 2) dCR rate and the ratio of bone marrow/liver absorbed radiation dose as an indicator of favorable biodistribution between target/risk organ. Results: All pts receiving the therapeutic dose of 131I-apamistamab (n=66) were able to receive an alloHCT, and the primary endpoint (dCR) was achieved in 13 pts receiving 131I-apamistamab vs 0 pts in CC (p&lt;0.0001). The median absorbed liver dose was 21.6 Gy (IQR: 21.0 - 22.8 Gy), median absorbed dose to bone marrow was 16.0 Gy (IQR: 11.5 - 22.3 Gy), and median ratio between marrow/liver dose was 0.79 (IQR: 0.52 - 1.02). Table 1 shows the distribution and rate of dCR for pts who received above or below 22 Gy administered dose to liver (24 Gy to liver was the established MTD from earlier studies, in which doses were escalated in 2 Gy increment and thus, 22 Gy represented MTD-1), and for pts stratified by marrow/liver dose ratio (higher ratio representing more favorable biodistribution). Pts with ≤22 Gy liver dose had a dCR rate of 13.5% vs. 27.6% for pts with &gt;22 Gy liver dose, and pts with &lt;median dose to bone marrow had a dCR rate of 12.1% vs. 27.3% for pts with ≥median estimated marrow dose. Importantly, pts with increasingly favorable biodistribution had nominally higher dCR rates of 10.0%, 20.0% and 26.9% for a marrow/liver ratio &lt;0.6, 0.6-0.9 and &gt;0.9, respectively, as illustrated in Figure 1. Taken together this demonstrates a radiation dose-response for the primary endpoint in this study. Overall, safety was similar across doses to the liver. Conclusion: 131I-apamistamab led induction and conditioning followed by alloHCT resulted in statistically significant improvement in dCR at 6 mos vs conventional care. A dose-response was demonstrated for pts receiving 131I-apamistamab with those receiving a liver dose closer to the MTD of 24 Gy having about twice the dCR rate compared to pts 22 Gy (MTD-1) or less. We also found pts with higher marrow/liver ratio experienced considerably higher rates of dCR which highlights the importance of maximizing the dose to target tissues, within the limits of established risk organ dose tolerances.

Background: Ph-like ALL is a high-risk subset of B-lineage ALL that responds poorly to standard chemotherapy regimens. While allogeneic hematopoietic cell transplantation (HCT) is routinely recommended for patients with Ph-like ALL, large multicenter data addressing its role is limited. Here, we conducted a multicenter study to evaluate the role of HCT in adolescent and young adult (AYA) and adult patients (pts) with Ph-like ALL and compare their outcomes to pts with Ph-pos and Ph-neg (non-Ph-like) ALL. Methods: The study included pts (age ≥18) with B-lineage ALL who received HCT in first complete remission (CR1) at 3 academic centers (MD Anderson Cancer Center, City of Hope and Mayo Clinic) between 2006 and 2021. Pts were divided into 3 main subgroups: Ph-like, Ph-pos and Ph-neg ALL. Ph-like ALL cases were identified using cumulative data obtained by targeted RNA sequencing, conventional cytogenetics, FISH studies, whole genome chromosomal microarray and flow cytometry. Measurable residual disease (MRD) prior to HCT was measured using flow cytometry with a sensitivity of 0.01% for Ph-neg and Ph-like ALL, and with a PCR assay for BCR::ABL1 for Ph-pos ALL. MRD-negativity was defined as &lt;0.01%. Predictors of relapse were evaluated in univariate and multivariate analysis using Fine-Gray sub-distribution hazard models considering non-relapse mortality (NRM) as a competing risk. Results: 673 patients were identified, 83 (12.3%) had Ph-like ALL, of which 73% had CRLF2-alterations. The remaining patients were classified either as Ph-pos (N=271, 40.3%) or Ph-neg ALL (N=319, 47.4%). Patients with Ph-like ALL were younger (median age 40 years vs 48 and 46 years for Ph-pos and Ph-neg ALL, respectively, p=0.01), more likely to be of Hispanic ethnicity (69% vs 32% and 48% for Ph-pos and Ph-neg ALL respectively, p&lt;0.001). Patients with Ph-like ALL were also more likely to have induction failure (24% vs 2% and 11% for Ph-pos and Ph-neg ALL, respectively, p=0.001). A summary of pts characteristics for each subgroup can be found in Table 1. The median follow-up was 30, 52 and 48 months for patients with Ph-like, Ph-pos and Ph-neg ALL, respectively. In univariate analysis, 3-yr OS and PFS did not differ significantly (66% and 59% vs 59% and 54%, p=0.1) between patients with Ph-like and Ph-neg ALL, respectively. Similarly, the cumulative incidence of relapse was comparable between patients with Ph-like and Ph-neg ALL (22% vs 20%, respectively, p=0.7). In contrast, the 3-yr OS (75%, p&lt;0.001) and PFS (70%, p=0.001) were significantly higher and relapse rate significantly lower (12%, p=0.003) in pts with Ph-pos ALL compared with Ph-like or Ph-neg ALL (Figure 1). The inferior survival in patients with Ph-like and Ph-neg ALL was likely attributable to higher relapse rates (22% and 20% vs 12%, respectively, p=0.003) compared to Ph-pos ALL. Finally, the 3-yr NRM rate in patients with Ph-like ALL was comparable (20% vs 18% and 23%, respectively, p&gt;0.1) to Ph-pos and Ph-neg ALL. We confirmed that the relapse rate in patients with Ph-like ALL was comparable to the rate in pts with Ph-neg ALL (HR=1.02, 95% CI 0.6-1.8, p=0.9) on multivariate analysis (MVA). Ph-pos ALL was associated with a significantly lower relapse rate compared with Ph-neg ALL (HR=0.4, 95% CI 0.3-0.7, p&lt;0.001). MRD positivity prior to allo-HCT was the only additional significant predictor for relapse on MVA (HR=2.9, 95% CI 1.8-4.7, p&lt;0.001). Conclusions: HCT appears to overcome the poor prognosis of patients with Ph-like ALL. Despite higher induction failure rates, patients with Ph-like ALL undergoing HCT in CR1 had similar outcomes to other Ph-neg ALL subsets. The impact of effective salvage therapy leading to MRD-negativity in CR1 in this group is under investigation and will be reported. Further studies are needed to assess the impact of different Ph-like alterations on HCT outcomes. Outcomes for patients with Ph-pos ALL are significantly better than other groups, likely due to the use of TKIs pre- and post-HCT.

Introduction: Next-generation sequencing (NGS) represents a promising modality for measurable residual disease (MRD) testing in patients with acute myeloid leukemia (AML), but systematic efforts are required to define the appropriate targets, test characteristics, and clinical implications. We recently reported that detection of persistent NPM1 or FLT3 internal tandem duplication (ITD) mutations in adults with AML in first complete remission (CR1) prior to allogeneic hematopoietic cell transplantation (alloHCT) is associated with increased relapse and death compared with those testing negative (JAMA 2023, PMID: 36881031). FLT3 tyrosine kinase domain (TKD) variants are present in 7-10% of adult patients with AML but the utility of this target for AML MRD testing in CR1 prior to alloHCT was previously unknown. Methods: Patients aged 18 or older who underwent alloHCT for AML in CR1 between 2013 and 2019 reported to have a FLT3-TKD variant at diagnosis and a pre-conditioning remission blood sample available in the CIBMTR biorepository were eligible for this study. Single-amplicon NGS (SA-NGS) library generation utilizing UMI-tagged primers targeting the D835 and I836 codons of FLT3 was performed on 400ng genomic DNA sequenced with unique dual indices, with error-corrected variant calling. Primary outcomes were overall survival (OS) and cumulative incidence of relapse (CIR). Secondary outcomes were relapse-free survival (RFS) and non-relapse mortality (NRM), with NRM being considered as a competing risk. Results: A total of351 patients met inclusion criteria for this study, and 342 (97.4%) had sufficient DNA for SA-NGS and were analyzed for clinical outcomes. Of these patients, 81 (23.7%) experienced relapse at a median of 5 months post-alloHCT. Using the current ELN-recommended variant allele fraction (VAF) threshold of 0.1% for NGS-based AML MRD, 14 patients (4.1%) tested positive. Patients with FLT3-TKD MRD VAF≥0.1% experienced higher rates of relapse (73.8% vs. 20.5%, p &lt; 0.0001) and decreased OS (11.4% vs. 66.8%, p &lt; 0.001) compared to VAF&lt;0.1%. The highly sensitive SA-NGS method allowed for exploration to determine if a deeper VAF threshold of 0.01% (previously validated for NPM1 and FLT3-ITD in the Pre-MEASURE study) was prognostic for FLT3-TKD as an MRD target. This led to an additional 20 patients being reclassified as positive (n = 34 with VAF above 0.01%, =9.9%). However, there was no significant difference in CIR (33.6% vs. 19.7%, p = 0.089) or OS (65.2% vs. 66.9%, p = 0.267) between patients with 0.01%≤VAF&lt;0.1% and VAF&lt;0.01% ( Figure). Out of 28 SA-NGS positive calls, 6 could not be validated by orthogonal digital droplet PCR testing, and interestingly, none of those 6 patients experienced relapse. Site-reported pre-transplant remission multiparametric flow cytometry (MFC) was available for 335 patients (98%). Results of MFC were not associated with differences in CIR (HR 1.2, 95% CI 0.52 - 2.76, p = 0.67) or OS (HR 0.78, 95% CI 0.34 - 1.77, p = 0.551).In multivariable analysis, FLT3-TKD NGS-MRD VAF≥0.1% remained prognostic for CIR (HR 6.1, 95% CI 3.1 - 12.0, p &lt; 0.001) and OS (HR 3.2, 95% CI 1.7 - 5.9, p &lt; 0.001). Conclusions: Detectable persistence of FLT3-TKD variants in blood from AML patients in first remission prior to first alloHCT is rare, but at a VAF level of 0.1% was strongly associated with increased relapse and death after transplant compared to those testing negative. In contrast to FLT3-ITD NGS-MRD, no evidence was found to support lowering the NGS-MRD VAF threshold from 0.1% to 0.01% for FLT3-TKD. Alternative methodology may further improve NGS-MRD test performance. Site-reported MFC prior to alloHCT did not stratify for post-transplant relapse or survival. Optimal NGS-MRD testing for patients with AML will likely require a multi-target approach and testing for persistence of FLT3-TKD MRD is shown here to represent an important component of this strategy.

Background : Most older patients (pts) with relapsed or refractory (R/R) AML cannot tolerate intensive treatment and are not eligible for curative allogeneic hematopoietic cell transplant (alloHCT). 131I-apamistamab, an anti-CD45 radioimmunoconjugate, delivers high dose targeted radiation to hematopoietic cells, allowing for myeloablation and eradication of leukemic cells while sparing toxicity to healthy organs. 131I-apamistamab led induction and conditioning can thus provide these pts with access to alloHCT. Methods: The SIERRA trial (NCT02665065) is a multi-center, randomized, controlled Phase 3 study comparing the rate of durable complete remission (dCR) lasting &gt;6 months (mos) after complete remission with/without platelet recovery (CR/CRp) between two groups: 131I-apamistamab led induction and conditioning followed by alloHCT vs physician's choice of conventional care (CC). Pts were randomized (1:1) to CC or 131I-apamistamab with fludarabine and total body irradiation (2 Gy) followed by alloHCT. CR/CRp assessment was 28-56 days post alloHCT or 28-42 days post initiation of therapy on the CC group. Pts in the CC group not achieving leukemia-free state could crossover (CO) to 131I-apamistamab. Here we report the results of a post hoc analysis to determine if the presence of various risk factors (i.e., Karnofsky Performance Status (KPS) &lt;90, HCT Comorbidity Index &gt;3, age &gt;65, adverse-risk cytogenetics, venetoclax failure prior to randomization) influenced achievement of dCR in pts treated with 131I-apamistamab. Results: In total, 153 pts were randomized (CC, n=76; 131I-apamistamab, n=77). All pts who received the therapeutic dose of 131I-apamistamab (n=66) underwent alloHCT vs 14 (18.2%) in the CC group. Of evaluable pts, dCR rates at 6 mos were 22% in the 131I-apamistamab group vs 0% in the CC group (95% CI;12.29, 34.73; p&lt;0.0001). A total of 19 pts (13, 131I-apamistamab group; 6, CO) achieved dCR. Table 1 shows the pt, disease, and transplant characteristics of dCR vs. non-dCR pts. Eight of the 19 pts (42.1%) had primary induction failure and the median time to randomization from diagnosis was 5.4 mos. Approximately 50% of pts (9/19) had adverse-risk cytogenetics. Over 35% (7/19) of the pts had failed prior venetoclax and the median number of prior treatments was 3 (range 1-5). A total of 10/19 (52%) pts had KPS of &lt;90% and a comorbidity index of &gt;3. There was no difference in the rate of dCR when stratifying by number of risk factors for a given pt (0 to 5) with 27% for pts with 0-1 risk factors, 14% for pts with 2-3 risk factors, and 11% for pts with 4-5 risk factors (p=0.251). Conclusion: Pts with R/R AML who have multiple risk factors such as adverse risk cytogenetics, age &gt;65, venetoclax failure, high comorbidity index or poor KPS are typically not considered for alloHCT due to high transplant-related mortality and post-transplant relapse rates. 131I-apamistamab was effective in achieving durable responses in R/R AML pts irrespective of the presence of multiple risk factors and successfully enabled alloHCT in such pts due to its targeted mechanism of action.

Introduction: Detection of measurable residual disease (MRD) prior to allogeneic hematopoietic cell transplant (alloHCT) in patients with acute myeloid leukemia (AML) in remission is associated with increased relapse and inferior survival after transplant. We recently reported that next-generation sequencing (NGS) detection of mutated NPM1 or FLT3-ITD in first complete remission (CR1) blood prior to alloHCT is strongly associated with increased relapse and death (PMID: 36881031). However, the prognostic implications of detecting persistence of other common AML-associated mutations at this treatment landmark remain incompletely defined. Around 20% of patients diagnosed with AML have variants in isocitrate dehydrogenase ( IDH) genes (~7% for IDH1) and clinical outcomes are known to differ due to co-occurrence of other mutations, IDH subtypes, treatment strategies, and patient factors. Studies have examined the relationship between residual IDH1 variants ( IDH1m) in CR and subsequent clinical outcomes, but definitive standardized evidence to inform decision-making for the clinical utility of IDH1m as a target for AML MRD testing was not previously available. Methods: Adult patients undergoing alloHCT for IDH1 mutated AML in CR1 at CIBMTR sites in the USA between 2013-2019 were eligible for the study if remission blood sample collected within 100 days before alloHCT and outcome data were available. Ultrasensitive error-corrected NGS (NGS-MRD) targeting IDH1, NPM1, and FLT3 genes was performed on DNA from pre-conditioning blood to identify residual variants. Detected IDH1m were validated by digital droplet PCR (ddPCR). The day of transplant was considered as day 0. Median follow-up time was calculated for censored patients. Overall survival (OS) was estimated using Kaplan-Meier (log-rank tests) and Cox proportional hazards models (forward selection); cumulative incidence of relapse was examined using Fine-Gray regression models with non-relapse mortality as a competing risk. Results: A total of 148 patients were included in the study, with a median follow-up time of 24 months. Relapse was observed in 37 (25%) patients, with the majority occurring within 1 year after alloHCT (n = 28, 76%). Pre-transplant flow cytometry results were reported by the transplant centers for 97% of patients (n = 144), but no statistically significant differences in clinical outcomes were observed between the positive and negative groups (OS: p = 0.3; relapse: p = 0.07). 53 patients (36%) tested positive for IDH1m persistence in CR1, with a 100% validation rate by ddPCR for variants with an orthogonal assay available. Logistic regression indicated that IDH1m persistence in remission was more likely to occur in patients older than 40 years (OR: 1.02 with every 1-year increase after 40, p = 0.04). Clinical outcomes showed no statistically significant difference between the pre-alloHCT IDH1m positive and negative groups (Figure 1A), and this remained true after further subgroup analysis by age. The variant allele fraction (VAF) of the residual IDH1m ranged from 0.09% to 48.5% (median: 1.5%), and no differences in clinical outcomes were observed when stratifying by high (≥2.5%) or low VAF (&lt;2.5%). Among patients with co-mutated NPM1 and/or FLT3-ITD at baseline (n=69), those with residual mutated NPM1 and/or FLT3-ITD in pre-transplant remission had significantly higher rates of relapse compared to those with residual IDH1m only or NGS-negative groups (p = 0.01, Figure 1B). The cohort excluding patients with co-mutated NPM1 and/or FLT3-ITD did not show any significant clinical outcome differences based on IDH1m persistence. Conditioning intensity did not show an association with clinical outcomes, and multivariable analysis for overall survival and relapse did not identify residual IDH1m as an important marker. Conclusion: Detection of persistent IDH1 variants in the blood of adult patients with AML in CR1 prior to first alloHCT is common, but not associated with increased relapse or death after transplant compared with those testing negative. For those patients with IDH1 mutated AML co-mutated with either NPM1 and/or FLT3-ITD, detection of persistent NPM1 and/or FLT3-ITD was associated with higher rates of relapse. These findings, from the largest study to date, do not support the detection of isolated IDH1 variants in CR1 blood prior to alloHCT as evidence of AML MRD or increased post-transplant relapse risk.