Acute Myeloid Leukemia: Novel Therapy, excluding Transplantation: New Treatment Strategies

763  Complete Responses in Relapsed/Refractory Acute Myeloid Leukemia (AML) Patients on a Weekly Dosing Schedule of XmAb14045, a CD123 x CD3 T Cell-Engaging Bispecific Antibody: Initial Results of a Phase 1 Study

Farhad Ravandi, et al.

The Abstract concludes: XmAb14045 demonstrated evidence of antileukemic activity in heavily pretreated patients with relapsed/refractory AML treated in Part A at the 1.3 and 2.3 µg/kg doses administered once weekly, with a 23% CR/CRi rate. CRS was the most common toxicity but was generally manageable with premedications. The study is ongoing with further optimization of dose, schedule, and premedication regimen for CRS anticipated during accrual to dose escalation cohorts in Part B. Identifier: NCT02730312


764  Phase 1 Cohort Expansion of Flotetuzumab, a CD123×CD3 Bispecific Dart® Protein in Patients with Relapsed/Refractory Acute Myeloid Leukemia (AML)

Geoffrey L. Uy, et al.

The Abstract concludes: In conclusion, among this initial cohort of patients treated at the RP2D (500 ng/kg/day), FLZ demonstrates antileukemic activity with an acceptable safety profile, in particular, among refractory patients, a difficult-to-treat patient population that represents a significant area of unmet medical need. Enrollment to the current study has now been expanded to further define the antileukemic activity of FLZ in patients with refractory AML, and investigate candidate biomarkers to enable identification of patients more likely to respond to FLZ. In addition, studies are now being initiated to investigate opportunities to expand the antileukemic activity of FLZ via combined administration with either concurrent or sequenced anti-PD-1 checkpoint blockade.


765  Results of Pivotal Phase 2 Clinical Trial of Tagraxofusp (SL-401) in Patients with Blastic Plasmacytoid Dendritic Cell Neoplasm (BPDCN)

Naveen Pemmaraju, et al.

The Abstract concludes: The pivotal trial of tagraxofusp was the largest prospectively designed, multi-center trial specifically dedicated to patients with BPDCN. This study has met its primary endpoint, and also demonstrated high response rates that were generally achieved early in the course of treatment and maintained over multiple cycles of therapy. Safety profile demonstrated most common toxicities of transaminitis, hypoalbuminemia, and thrombocytopenia; occurrence of CLS was the most serious TRAE, which was overall manageable in this population. Patients with BPDCN are being enrolled in an additional cohort, Stage 4, to ensure ongoing access. Tagraxofusp is also being evaluated in other trials including in patients with chronic myelomonocytic leukemia (CMML) and myelofibrosis (MF).


766  Phase II Clinical Trial of Alisertib, an Aurora a Kinase Inhibitor, in Combination with Induction Chemotherapy in High-Risk, Untreated Patients with Acute Myeloid Leukemia

Andrew M. Brunner, et al.

The Abstract concludes: Alisertib, a novel aurora A kinase inhibitor, combined with conventional induction, is efficacious and demonstrates a promising rate of remission and survival among patients with previously untreated high-risk AML. Larger randomized studies are under consideration to better assess the promise of this novel combination.


767  Safety, Efficacy, Pharmacokinetic (PK) and Biomarker Analyses of BCL2 Inhibitor Venetoclax (Ven) Plus MDM2 Inhibitor Idasanutlin (idasa) in Patients (pts) with Relapsed or Refractory (R/R) AML: A Phase Ib, Non-Randomized, Open-Label Study

Naval G. Daver, et al.

The Abstract concludes: Ven+idasa has a tolerable safety profile with appropriate prophylaxis in this R/R AML population. An anti-leukemic response rate of 50% was seen at dose levels being considered for RP2D (Ven 600mg + idasa 150/200mg). Overall, responses appeared deep and durable. Preliminary biomarker data indicate that the relative ratio of BCL2 to BCLxL and MCL1 may be important for Ven+idasa activity, whereas pts with baseline TP53 muts had lower response rates. To confirm the clinical benefit and safety of Ven+idasa, the combination will be further evaluated in an expansion arm, after confirmation of the RP2D.


768  Mcl-1/CDK9 Targeting By AZD5991/AZD4573 Overcomes Intrinsic and Acquired Venetoclax Resistance in Vitro and In Vivo in PDX Model of AML through Modulation of Cell Death and Metabolic Functions

Bing Z Carter, et al.

The Abstract concludes: We demonstrate that Mcl-1 has metabolic functions in AML and that inhibition of Mcl-1 enhances ABT-199 apoptogenic activity and overcomes intrinsic and acquired ABT-199 resistance in vitro and in vivo in a PDX murine model of AML, suggesting that inhibition of Mcl-1 improves the efficacy of ABT-199, and overcomes established resistance to Bcl-2 inhibition. Suppressing metabolic activity and CXCR4 inhibition may also contribute to the efficacy of this combination against AML stem cells in the BM microenvironment.