What to use to treat AML: the role of emerging therapies

The development and approval of novel substances have resulted in substantial improvements in the treatment of acute myeloid leukemia (AML). In the current era of novel treatment options, genetic and molecular testing at the time of diagnosis and relapse becomes increasingly relevant. Midostaurin in combination with intensive chemotherapy is the standard of care as upfront therapy in younger AML patients with mutated fms-related tyrosine kinase 3 (FLT3). Gilteritinib, a second- generation FLT3 inhibitor, represents a key drug for relapsed/refractory (R/R) FLT3-mutated AML patients. Targeted therapy has also been developed for patients with mutated isocitrate dehydrogenase 1 (IDH1) and IDH2. The US Food and Drug Administration (FDA) approved ivosidenib as a monotherapy for newly diagnosed older adult IDH1-mutated patients and enasidenib for R/R IDH2-mutated AML patients. CPX-351, a liposomal formulation of daunorubicin and cytarabine, has become an important upfront treatment strategy for fit patients with therapy-related AML or AML with myelodysplasia-related changes that are generally challenging to treat. The antibody drug conjugate gemtuzumab ozogamicin was approved in combination with intensive therapy for patients with newly diagnosed (FDA/European Medicines Agency [EMA]) as well as R/R CD33+ AML. The combination of venetoclax, an oral selective B-cell leukemia/lymphoma-2 inhibitor, with hypomethylating agents or low-dose AraC (LDAC) has changed the treatment landscape and prognosis for older adult patients very favorably. The addition of glasdegib, a small-molecule hedgehog inhibitor, to LDAC is another example of novel options in older patients. Further substances have shown promising results in early clinical trials.

Replacing the Anthracycline By Gemtuzumab Ozogamicin in Older Patients with De Novo Standard-Risk Acute Myeloid Leukemia Treated Intensively - Results of the Randomized ALFA1401-Mylofrance 4 Study

Introduction Based on the results of the ALFA-0701 trial (Castaigne et al. Lancet 2012), the addition of fractionated doses of the anti-CD33 antibody drug conjugate gemtuzumab ozogamicin (GO, Mylotarg®) to conventional chemotherapy has been approved in 2017 for frontline treatment of adults with CD33-positive acute myeloid leukemia (AML). Prolonged event-free survival (EFS) was observed in patients with AML of favorable or intermediate risk, while not in those with adverse cytogenetics. Nevertheless, more frequent added toxicities could make the addition of GO a questionable option in patients over 60-65 years of age. In this ALFA-1401/Mylofrance 4 trial (NCT02473146), we investigated if the replacement of the anthracycline by GO might also improve EFS in older patients. Methods Between January 2016 and March 2019, 225 patients were randomized 2:1 to receive an experimental GO-cytarabine combination (154 patients) or a standard anthracycline-cytarabine treatment (71 patients). Patients aged 65 to 80 years old (later extended to patients aged 60-64 years old), with previously untreated de novo AML of favorable or intermediate cytogenetics were eligible for the trial. Standard treatment arm consisted in a 7+3 using idarubicin at 12 mg/m 2/d on day 1 to 3 and cytarabine 200 mg/m 2/d on day 1 to 7. Experimental arm (GO arm) consisted of two doses of GO 3 mg/m 2/d on day 1 and 4 and cytarabine 200 mg/m 2/d on day 1 to 7. Post-remission therapy comprised two courses of intermediate-dose cytarabine (IDAC) at 1.5 g/m 2/12h on day 1, 3 and 5. In the GO arm, a third dose of 3mg/m 2/d GO was administered on day 1 of the first IDAC course. The first IDAC course could serve as second induction in patients not responding to the first one. The decision to perform allogeneic hematopoietic stem cell transplantation (allo-HSCT) in first remission was left to the discretion of the physician. The efficacy analysis was conducted in the modified intent-to-treat (mITT) population excluding patients who did not meet the cytogenetic eligibility criteria. The primary study endpoint was EFS. Secondary endpoints were response rate defined by complete remission (CR), CR with incomplete platelets recovery (CRp) and CR with incomplete hematological recovery (CRi), early mortality, relapse incidence, overall survival (OS) and safety. Results Among the 225 randomized patients, 214 (71 standard arm, 143 GO arm) were included in the mITT population. There were 126 men and 88 women. Median age was 70 years (61-80). Cytogenetics was of favorable and intermediate risk in 14 and 200 patients, respectively. One hundred and eighty-one patients reached CR/CRp/CRi, 64 (90%) in standard arm and 117 (82%) in GO arm (p=0.17). Median follow-up time was 38 months. At 2 years, estimated EFS was 38% [95% CI, 28-51] in the standard arm vs. 29% [22-37] in the GO arm (Hazard Ratio (HR), 1.37 [0.98-1.93]; p= 0.067) (Figure 1A). Overall, 118 patients relapsed, 36 (51%) in standard arm and 82 (57%) in GO arm. At 2 years, estimated cumulative incidence of relapse was 48% [36-61] in standard arm vs. 61% [52-70] in GO arm (csHR, 1.32 [0.90-1.93]; p= 0.078). Overall, 122 patients died, 38 (54%) in standard arm, 84 (59%) in GO arm. Sixty-day mortality was 4% in standard arm vs. 10% in GO arm (p=0.13). At 2 years, estimated OS was 65% [55-77] in standard arm vs. 52% [45-61] in GO arm (HR, 1.27 [0.86-1.87]; p= 0.23). In subgroup analysis for EFS (Figure 1B), we found a significant interaction with gender, GO having a detrimental effect in women which persisted after adjustment on known prognostic factors. A total of 33 patients received allo-HSCT in first remission, 19 (30%) in standard arm and 14 (12%) in GO arm (p=0.006). When censoring these patients at transplant time, HR of GO on EFS was 1.27 ([0.88-1.83]; p=0.19). Regarding safety, 76% and 80% of patients had at least one grade 3 to 5 adverse event (p=0.81), including infection in 30% vs. 21% and bleeding in 7% vs. 29% in standard arm and GO arm respectively. Serious adverse events were reported in 34% of patients in standard arm vs. 49% in GO arm (p=0.031). Sinusoidal obstruction syndrome occurred in 2 patients in the GO arm. Conclusion Frontline use of GO instead of idarubicin, when combined to cytarabine, does not benefit older patients with de novo standard-risk AML. At the reduced dose schedule used in this study, GO remains associated with significant toxicities while non-significant higher relapse incidence, shorter EFS and shorter OS were observed. Figure 1 Figure 1. Disclosures Lambert: ASTELLAS: Consultancy; CELGENE/BMS: Consultancy. Pautas: ABBVIE: Consultancy; PFIZER: Consultancy. Gastaud: PFIZER: Consultancy; CELGENE/BMS: Consultancy; ABBVIE: Consultancy; GSK: Consultancy. Barbieux: ASTRA-ZENECCA: Consultancy. Rousselot: Incyte, Pfizer: Consultancy, Research Funding. Castaigne: PFIZER: Consultancy. Dombret: Amgen: Honoraria, Research Funding; Incyte: Honoraria, Research Funding; Jazz Pharmaceuticals: Honoraria, Research Funding; Novartis: Research Funding; Pfizer: Honoraria, Research Funding; Servier: Research Funding; Abbvie: Honoraria; Daiichi Sankyo: Honoraria; BMS-Celgene: Honoraria.

Retrospective Analysis of the Outcomes of Patients with Relapsed/Refractory Acute Myeloid Leukemia Included in a Patient Named Program of Gemtuzumab Ozogamicin

Introduction: In 2010 the French Health Agency opened a compassionate patient named program of gemtuzumab ozogamicin (GO, Mylotarg®) in relapsed/refractory (R/R) patients with acute myeloid leukemia (AML). Of note, since 2012, it was recommended to use GO at the dose of 3 or 6 mg/m 2 in addition to chemotherapy. We conducted a retrospective trial (NCT03287128) to evaluate the efficacy and the safety of GO-based regimen in R/R adult AML patients. Patients and methods: We retrospectively collected data of patients older than 18 years treated with GO-based regimen for AML in first relapse or for refractory AML, defined by failure after a prior standard intensive chemotherapy, in 18 French centers between December 15, 2011 and November 10, 2016. The primary objective was to assess the response to GO-based regimen. Patients were considered in response if reaching complete remission (CR), CR without platelet recovery (CRp) or CR with incomplete hematological recovery (CRi). Secondary objectives were the cumulative incidence of allogeneic hematopoietic stem cell transplantation (allo-HSCT) and the safety of the use of GO-based regimen. Results: Three hundred and thirty-five adult patients with R/R AML were included. Median age was 58 years (20 to 80 years). At diagnosis, cytogenetics was favorable in 50 (17%) patients, intermediate in 173 (59%) and adverse in 60 (20%). ELN distribution was favorable: 35%, intermediate: 42% and unfavorable: 23%. NPM1 mutation was present in 29% of patients and FLT3 mutation in 23%. Most patients had de novo AML (84%). Two hundred and thirty-eight patients (79%) were in first relapse and 65 (21%) had a refractory AML. The time between first diagnosis of AML and treatment with GO-based regimen was 4 to 16 months (median 9.4 months). Most patients (88%) received GO in combination with various intensive chemotherapy scheme including "7+3" with anthracycline/cytarabine (n=39 patients), intermediate and high-dose cytarabine (n=68), cytarabine in continuous intravenous infusion (n=78), mitoxantrone/cytarabine (n=49) and fludarabine/cytarabine and/or amsacrine and/or etoposide chemotherapy (n=35). Median follow-up time was 11 months. Among the 305 patients, 191 responded to GO-based regimen: 110 (36%) were in CR, 62 (20%) were in CRp and 19 (6%) in CRi for an overall response rate (CR+CRp+CRi, ORR) of 63%. In multivariate analysis, response was associated with age <50 years, de novo AML and relapse status. Among the 191 responders, 110 received additional courses of chemotherapy, 69 with GO. Main reason to not receive additional course (with or without GO) was allo-HSCT project. In the whole population, median overall survival (OS) after day 1 of treatment with GO was 11.2 months. In the population of responders, median OS after response was 20.4 months. In multivariate analysis, longer survival was associated with age < 50 years, de novo AML and favorable ELN group. Cumulative incidence of relapse at 24 months after response was 46%. One hundred and forty-seven patients received allo-HSCT, including 122 responders after GO-based regimen and 25 patients in treatment failure. Cumulative incidence of allo-HSCT at 18 months was 48%. Four-year OS was 48% in transplanted patients versus 19% in non-transplanted patients (Figure 1). Regarding safety of GO-based regimen, early deaths occurred within <30 days after the first dose of GO in 14 patients, and within <60 days in 35 patients. Myelosuppression was observed in all patients. Mean duration of thrombocytopenia <100 G/L was 35 days in responders. Bleeding grade 3 or more was observed in 22 patients (7%). Infection grade 3 or more was observed in 112 patients (30%). Sinusoidal obstruction syndrome (SOS) after GO treatment was reported in 6 patients, resolving in 4 of them. Four cases of fatal SOS were reported after allo-HSCT. Toxic deaths, i.e., not related to worsening leukemia, were reported in 20 patients after the first course of chemotherapy, 3 after additional courses and 33 after allo-HSCT. Conclusion. Our study is the first to report efficacy data in the real-world setting of R/R AML adult patients treated with GO-based regimen. In our cohort of 305 patients, response rate was 63% and GO-based regimen appears as a valuable bridge-to-transplant option. Safety analysis showed toxicities consistent with the known safety profile of GO and chemotherapy. Figure 1 Figure 1. Disclosures Lambert: ASTELLAS: Consultancy; CELGENE/BMS: Consultancy. Pautas: PFIZER: Consultancy; ABBVIE: Consultancy. Raffoux: ASTELLAS: Consultancy; PFIZER: Consultancy; ABBVIE: Consultancy; CELGENE/BMS: Consultancy. Legrand: Servier: Consultancy. Gastaud: PFIZER: Consultancy; CELGENE/BMS: Consultancy; ABBVIE: Consultancy; GSK: Consultancy. Pigneux: Amgen: Consultancy; Sunesis: Consultancy, Research Funding; BMS Celgene: Consultancy, Research Funding; Roche: Consultancy, Research Funding; Novartis: Consultancy, Research Funding. Mathilde: SERVIER: Consultancy; ABBVIE: Consultancy. Dombret: Amgen: Honoraria, Research Funding; Incyte: Honoraria, Research Funding; Jazz Pharmaceuticals: Honoraria, Research Funding; Novartis: Research Funding; Pfizer: Honoraria, Research Funding; Servier: Research Funding; Abbvie: Honoraria; BMS-Celgene: Honoraria; Daiichi Sankyo: Honoraria. Rousselot: Incyte, Pfizer: Consultancy, Research Funding. Castaigne: PFIZER: Consultancy.

The rs35112940 CD33 Polymorphism Reduces CD33 Internalization and Efficacy of CD33-Directed Gemtuzumab Ozogamicin

Background CD33 is a myeloid-specific cell surface protein widely expressed on acute myeloid leukemia (AML) cells making it an excellent immunotherapeutic target. Current CD33-directed immunotherapeutic treatment strategies include gemtuzumab ozogamicin (GO), an antibody-drug conjugate (ADC) which was approved for the treatment AML in 2017 and has demonstrated promising results thus far. The mechanism of action of GO begins with recognition of CD33 by the antibody portion of GO, followed by internalization of the CD33-GO complex, and finally delivery of free calicheamicin molecules to the cell to induce cellular apoptosis. As such, modifications that impact these steps on any level presumably impact the response and overall efficacy of GO. Indeed, previous studies from our group have identified germline variations in CD33 that are associated with differences in CD33 structure, CD33 cell surface expression levels, and clinical outcomes in response to GO. Among these germline variations is rs35112940 (G>A; Arg304Gly), a missense polymorphism which is located in exon five of CD33 adjacent to the cytoplasmic immunoreceptor tyrosine-based inhibitory motif (ITIM) domain, a critical feature for CD33 internalization. While our previous work identified statistical associations between the A allele of rs35112940 and lower CD33 expression and reduced benefit from treatment using GO, these results are yet to be validated functionally. Additionally, it still remains unknown if the impact of the rs35112940 variation is due to reduced CD33 expression alone or if the rs35112940 variation also impacts CD33 internalization thereby modulating CD33 efficacy. Methods To functionally validate the effect of the rs35112940 variant, we used CRISPR/cas9 to knockout CD33 in HL60 cells and subsequently engineered the HL60-CD33 KO cells to express either wildtype CD33 (HL60-CD33 FL) or CD33 encoding the rs35112940 variant (HL60-CD33 FL-rs35112940). The engineered cells were then treated with GO for 48 hours to capture the impact of the rs35112940 variation on the efficacy of GO. To assess the impact of the rs35112940 variation on CD33 internalization, we performed a flow cytometry-based internalization assay using secondary antibodies to capture the remaining amounts of CD33 present on the cell surface after 4 hours allowing us to determine the internalization of CD33 over time. Results All engineered cells expressed CD33 with less than 1-log fold difference in median fluorescence intensity (MFI) (HL60-CD33 FL MFI vs HL60-CD33 FL-rs35112940 MFI: 22536 vs 24882, Figure 1) and thus we were able to characterize the impact of the rs35112940 variant independent of its impact on CD33 cell surface expression. After 48-hour treatment with 250 ng/mL of GO, we observed that HL60-CD33 FL-rs35112940 cells were more resistant to GO than HL60-CD33 FL cells (66.4% vs 46.5% cell viability, P = 0.02, Figure 2A). Similar results were observed at multiple concentrations of GO. Given the proximity of the rs35112940 loci to the ITIM domain of CD33, we hypothesized that the rs35112940 variation may impact CD33 internalization as well. In a flow cytometry-based internalization assay over a 4-hour window, we observed that that HL60-CD33 FL-rs35112940 cells had an approximate 10% reduction in CD33 internalization in comparison to HL60-CD33 FL cells (Figure 2B). Taken together these results provide insight into the effect of the rs35112940 variant on GO efficacy and CD33 biology, corroborating our previous findings, and support the use of CD33 polymorphisms to guide patient selection for treatment with GO. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

FLT3-Mutated Acute Myeloid Leukemia Using a Novel Regimen of Gemtuzumab Ozogamicin and Midostaurin in Combination with Standard Cytarabine and Daunorubicin Induction Therapy

Introduction Approximately 25-30% of adult acute myeloid leukemias (AMLs) have FLT3 mutation. Among the two main types, internal tandem duplication (ITD) and tyrosine kinase domain (TKD) point mutations, FLT3-ITD is associated with poorer clinical outcomes. Recently, midostaurin was found to improve survival when combined with 7+3 induction for FLT3-ITD or FLT3-TKD AML. Additionally, increased CD33 expression in AML patient samples has been linked to FLT3-ITD+ blasts. This suggests the combined targeting of CD33 and FLT3 in AML patients as a novel treatment approach. Hence, we introduce a combination therapy of gemtuzumab ozogamicin (GO) - a humanized CD33 antibody conjugated to a calicheamicin derivative - and midostaurin with 7+3 (cytarabine + daunorubicin) for newly diagnosed FLT3-mutated AML. Methods This Phase I open-label, dose-finding study was designed to determine the maximum tolerated dose schedule of GO administered with midostaurin and 7+3 induction and to assess the safety and preliminary efficacy of this combination. Patients needed to be >18 years old, have newly diagnosed AML, be fit for 7+3 induction, and harbor a FLT3-ITD or -TKD mutation per next-generation sequencing or PCR testing. In cohorts of 3, patients were assigned to 1 of 4 dose levels according to the "keyboard" Bayesian toxicity probability interval design (Table 1) applied to a target dose-limiting toxicity (DLT) rate of 20%. Non-hematologic DLTs were defined as study drug-related grade ≥3 toxicities, with exceptions for infections, elevated liver enzymes (that resolve in ≤5 days), GI symptoms (≤3 days), and electrolyte abnormalities (≤1 day). Hematologic DLTs were grade 4 neutropenia or grade ≥3 thrombocytopenia at 6 weeks after the start of the induction cycle and in the absence of AML. The DLT evaluation period covered the induction and, if applicable, re-induction cycles. Clinical responses were determined by 2017 ELN criteria. CD33 expression on AML blasts was quantified before and after treatment. Upon completion of 1 or 2 induction cycles, patients with a CR or CRi could receive up to 2 cycles of consolidation therapy, consisting of cytarabine (HiDAC or MiDAC depending on age <60), midostaurin, and GO on Day 1 of the first cycle, or proceed to allogenic hematopoietic cell transplantation (HCT). Results Eight patients have been enrolled out of the planned accrual of 24. The median age was 59 (range: 35-72) years, and every patient identified as White and Non-Hispanic. At screening, all patients had FLT3-ITD mutations. The median bone marrow blast percentage was 64% (range 17%-91%), with the majority of blasts expressing CD33 (median 96%, range 80-100%, 2 patients missing data due to recent enrollment). The current numbers of patients treated by dose level (DL) were: 3 on DL1 (IV GO 3 mg/m 2 Day 1), 3 on DL2 (IV GO 3 mg/m 2 Day 1 and 4), and 2 on DL3 (IV GO 3 mg/m 2 Day 1, 4, and 7). No DLTs were observed among the six patients in DL1 or DL2. Likewise, no DLTs were observed in the two patients in DL3. The most common treatment-emergent adverse events included grade 3 febrile neutropenia (75% of patients), grade 3/4 mucositis (25%), grade 3 sepsis (25%), and grade 3 esophagitis (12.5%). One patient had a serious adverse event: a GO-related Grade 4 sinusoidal obstruction syndrome occurring ~4 months into treatment and lasting 23 days. The median duration of study therapy was 62 days (range 20-95 days); reasons for discontinuation were disease progression (n=2), non-compliance (n=1), and allogeneic HCT (n=5). The overall response rate and composite complete remission rate were both 75% (95% CI: 34.9% - 96.8%). There were no treatment-related deaths in the first 30 days. Due to the early nature of this study, survival outcomes have not been calculated and post-induction CD33 expression data are not available. Conclusions In newly diagnosed FLT3-mutated AML patients, induction chemo/immunotherapy with GO, midostaurin, and 7+3 has yielded promising responses and has been well tolerated with no DLTs thus far. Additional patients and correlative analyses of CD33 expression will provide further insight into the safety and efficacy of this regimen for a patient population with historically poor prognosis. Figure 1 Figure 1. Disclosures Borate: Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding; Blueprint Medicine: Membership on an entity's Board of Directors or advisory committees; Jazz Pharma: Research Funding; Genentech: Membership on an entity's Board of Directors or advisory committees, Other: Advisory Board; AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding; Daiichi-Sankyo: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees; incyte: Membership on an entity's Board of Directors or advisory committees, Research Funding; Rampal: Membership on an entity's Board of Directors or advisory committees; Galecto, Inc.: Consultancy; Promedior: Consultancy. Saultz: IKENA: Research Funding. Traer: ImmunoGen: Membership on an entity's Board of Directors or advisory committees; Servier/Agios: Membership on an entity's Board of Directors or advisory committees; Incyte: Research Funding; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Schrodinger: Research Funding; Genentech: Membership on an entity's Board of Directors or advisory committees; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees. Walter: Amgen: Research Funding; Aptevo: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Immunogen: Research Funding; Macrogenics: Consultancy, Research Funding; Jazz: Research Funding; Pfizer: Consultancy, Research Funding; Selvita: Research Funding; Amphivena: Consultancy, Other: ownership interests; Agios: Consultancy; Astellas: Consultancy; BMS: Consultancy; Genentech: Consultancy; Janssen: Consultancy; Kite: Consultancy.