Silverman, Margarida

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.

Introduction: Front-line immunochemotherapy (IC) with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) is expected to cure 60-70% of newly diagnosed DLBCL. Up to one third of newly diagnosed DLBCL patients will have relapsed or refractory (r/r) disease.1 Current standard of care for these patients is salvage chemotherapy and, if chemosensitive, to be followed by high dose chemotherapy with hematopoietic cell rescue (autoHCT).2,3 Event-free survival at 24 months (EFS24) after frontline IC is associated with excellent long-term outcomes with overall survival (OS) similar to that of age- and sex-matched controls.4 In comparison, those achieving EFS24 following autoHCT for relapsed or refractory disease may have increased risk for late-mortality compared to the general population with advanced age and intensive salvage therapy contributing to the risk of late complications.5 We sought to better characterize EFS24 after autoHCT to determine the utility of this end-point for informed clinical decisions, patient management, and future clinical trials. Methods: Patients were prospectively enrolled onto the Molecular Epidemiology Resource (MER) of the University of Iowa/ Mayo Clinic Specialized Program of Research Excellence (SPORE). Patients were followed for relapse, retreatment, and death; all events were validated by medical record review. For this analysis patients were included if they were consented within 9 months of initial diagnosis of DLBCL between 2002-2012, had received anthracycline-based IC (R-CHOP, or similar), and eventually had undergone autoHCT for r/r DLBCL. Patients with primary central nervous system (CNS) lymphoma or post-transplant lymphoproliferative disorders (PTLD) were excluded. Overall survival (OS) was defined as time from autoHCT until death due to any cause. Event-free survival (EFS) was defined as time from autoHCT until progression, relapse, retreatment, or death due to any cause. OS from achieving EFS24 after autoHCT was compared to age- and sex-matched general US population. Results: 108 patients underwent autoHCT for relapsed DLBCL between 2002 and 2017. Median age at autoHCT of the patients was 60 years (range 20-78) and 72 (67%) were male. The most common transplant conditioning regimen was BEAM (82%). At a median follow-up after autoHCT of 85 months (range 1-171), 72 patients (67%) had an event and 64 patients (59%) had died. Kaplan-Meier estimates for EFS and OS at 24 months from the time of autoHCT were 49% (95% CI: 40-59) and 61% (95% CI: 52-71), respectively. 52 patients had a progression within 24 months of autoHCT; OS from progression was poor (median OS=2.8 months, 95% CI: 1.8-6.0; 5 year OS = 9%, 95% CI: 2-22). 48 patients achieved EFS24 after autoHCT; median OS from achieving EFS24 was 136 months (95% CI: 92-NE) and 5 year OS was 79% (95% CI: 68-93). This was inferior to the background population (Figure 1, SMR=3.64, 95% CI: 2.11-6.27, p<0.0001). Eight patients had a progression after achieving EFS24 from autoHCT. OS from progression in these 8 patients (median OS=27.3 months, 95% CI: 14.4-NE; 5 year OS = 16%, 95% CI: 3-93) was improved compared to progression within 24 months of autoHCT (p=0.072, figure B). Cause of death (COD) in EFS24 achievers was progression of lymphoma (n=6), infection (n=1), secondary malignancy related to therapy (n=3), heart disease (n=1), and unknown (n=1). Conclusions: Patients achieving EFS24 after salvage chemotherapy and autoHCT have a favorable long-term prognosis; however, overall survival remained inferior to the general population. Most common COD after achieving EFS24 was progression of lymphoma. In spite of this, EFS24 remains a valuable end-point for informed clinical decisions, patient management, and future clinical trials. Figure 1 Disclosures Maurer: Morphosys: Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding; Nanostring: Research Funding. Ansell:Mayo Clinic Rochester: Employment; Bristol-Myers Squibb: Research Funding; Affimed: Research Funding; Trillium: Research Funding; Regeneron: Research Funding; Seattle Genetics: Research Funding; Mayo Clinic Rochester: Employment; Affimed: Research Funding; Bristol-Myers Squibb: Research Funding; LAM Therapeutics: Research Funding; Regeneron: Research Funding; Seattle Genetics: Research Funding; Trillium: Research Funding; LAM Therapeutics: Research Funding. Cerhan:Celgene: Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees; NanoString: Research Funding. Farooq:Celgene: Honoraria; Kite Pharma: Research Funding.

Introduction: Allogeneic hematopoietic stem cell transplant is curative in several benign and malignant hematological disorders with predominant complications of graft versus host disease (GVHD) and infections. Antithymocyte globulin (ATG) has been shown in a number of prospective trials to be effective in decreasing acute and chronic GVHD. Recently, it has been suggested that recipient peripheral blood absolute lymphocyte count (ALC) on the day of ATG administration interacts with the dose of ATG administered and predicts transplantation outcomes. This interaction may depend on the preparative regimen and the dose of ATG used. We sought to determine if ALC at time of administration of ATG could impact clinical outcomes in a population treated with busulfan fludarabine myeloablative regimen and a fixed dose of 4mg/kg of ATG. Methods: Seventy consecutive pts who underwent a matched unrelated donor transplant with ATG at the University of Iowa were retrospectively analyzed. All pts received rabbit ATG (Thymoglobulin®) at 0.5 mg/kg on day -3, 1.5 mg/kg on day -2 and 2 mg/kg on day -3 in addition to tacrolimus and methotrexate. All received a myeloablative preparative regimen with busulfan (130 mg/m2 days -6 to -3) and fludarabine (40 mg/m2 daily for 4 days). All but one pt received peripheral blood as graft source. The effect of patient, disease, and transplant characteristics on 2-year outcomes was evaluated using Cox and Fine and Gray regression models. For relapse, GVHD, and infections, death was considered a competing risk. Estimated effects of predictors are reported as hazard ratios (HR) along with 95% confidence intervals. Results: Median age was 59 years (range 20-68). Underlying diagnoses were AML (n=47), MDS (n=20) and CML (n=3). Disease Risk index showed 25 high risk, 24 intermediate risk and 21 low risk patients in this study. The median peripheral blood ALC on day -3 was 100 × 102/µL (range 0-1144 × 102/µL). Univariate analysis showed no significant impact of ALC (100+ vs <100) on 2-year risk of developing GVHD (HR 1.49, 95%CI: 0.77 - 2.86), 2-year overall infection risk (HR 0.86, 95%CI: 0.51-1.46), 2-year bacterial (HR 0.78, 95%CI: 0.43-1.42), viral (HR 0.81, 95%CI: 0.41-1.60) and fungal (HR 0.63, 95% CI: 0.17-2.33) infections. Univariate analysis also showed no significant influence on 2-year relapse-free survival (HR 0.67, 95%CI: 0.21-2.14) and overall survival (HR 0.84, 95%CI: 0.34-2.06). Significantly worse survival is seen in MDS in comparison to leukemic pts, and high disease risk in comparison to low disease risk. Conclusion: Our single center experience using busulfan and fludarabine myeloablative regimen and rabbit ATG dosed at 4 mg/kg showed no interaction between the recipient peripheral blood ALC and ATG to predict GVHD, infections, overall and relapse free survival. Disclosures Farooq: Celgene: Honoraria; Kite Pharma: Research Funding.