Progress in the understanding of the biology and therapy of acute myeloid leukemia (AML) is occurring rapidly. Since 2017, nine agents have been approved for various indications in AML. These included several targeted therapies like venetoclax, FLT3 inhibitors, IDH inhibitors, and others. The management of AML is complicated, highlighting the need for expertise in order to deliver optimal therapy and achieve optimal outcomes. The multiple subentities in AML require very different therapies. In this review, we summarize the important pathophysiologies driving AML, review current therapies in standard practice, and address present and future research directions.

Patients with CML treated with TKI can have a life expectancy comparable to that of the general population. Due to the extended duration of TKI administration, treatment discontinuation has been increasingly sought. Medical records of 100 patients with CML who were in MR4.5 and discontinued their TKI outside clinical trials were reviewed. After a median follow-up of 30 months (range, 5–112 months) after discontinuation, 35% and 17% lost MR4.5 and major molecular response (MMR), respectively. Only six patients lost MMR 12 months or more after discontinuation. Loss of MR4.5 was observed in 29% and 7% of patients with sustained MR4.5 duration of more than 2 and 6 years before discontinuation, respectively. By univariate analysis, there was a higher risk of loss of MR4.5 for patients who were treated for less than 87 months, received second or subsequent line TKI, never received interferon, or those with sustained MR4.5 for less than 6 years. By multivariate analysis, sustained MR4.5 for 6 years or more was the only significant predictor for durable response. Overall, 30% of patients who discontinued while in MR4.5 were retreated with 93% regaining MR4.5 at a median of 5 months. These results demonstrate that under proper conditions, treatment discontinuation is feasible outside of clinical trial setting. MR4.5 duration of 6 years or more before discontinuation is associated with very low risk of loss of MR4.5.

Preclinical models have shown that blocking PD-1/PD-L1 pathways enhances antileukemic responses. Azacitidine upregulates PD-1 and IFNγ signaling. We therefore conducted this single-arm trial, in which patients with relapsed/refractory (R/R) acute myeloid leukemia (AML) were treated with azacitidine 75 mg/m2 days 1 to 7 intravenously or subcutaneously with nivolumab 3 mg/kg intravenously on days 1 and 14, every 4 to 6 weeks. For the seventy patients who were treated, the median age was 70 years (range, 22–90) and the median number of prior therapies received was 2 (range, 1–7). The overall response rate (ORR) was 33%, including 15 (22%) complete remission/complete remission with insufficient recovery of counts, 1 partial response, and 7 patients with hematologic improvement maintained >6 months. Six patients (9%) had stable disease >6 months. The ORR was 58% and 22%, in hypomethylating agent (HMA)–naïve (n = 25) and HMA-pretreated (n = 45) patients, respectively. Grade 3 to 4 immune-related adverse events occurred in 8 (11%) patients. Pretherapy bone marrow and peripheral blood CD3 and CD8 were significantly predictive for response on flow cytometry. CTLA4 was significantly upregulated on CD4+ Teff in nonresponders after 2 and 4 doses of nivolumab. Azacitidine and nivolumab therapy produced an encouraging response rate and overall survival in patients with R/R AML, particularly in HMA-naïve and salvage 1 patients. Pretherapy bone marrow aspirate and peripheral blood CD3 percentage may be biomarkers for patient selection. Significance: Azacitidine in combination with nivolumab appeared to be a safe and effective therapy in patients with AML who were salvage 1, prior hypomethylator-naïve, or had increased pretherapy CD3+ bone marrow infiltrate by flow cytometry or IHC. Bone marrow CD3 and CD8 are relatively simple assays that should be incorporated to select patients in future trials. This article is highlighted in the In This Issue feature, p. 305

Introduction: Venetoclax (VEN), a selective BCL2 inhibitor, has single‐agent activity in relapsed and refractory (R/R) acute myeloid leukemia (AML), and efficacy in lower intensity combinations for treatment‐naïve elderly AML patients. VEN treatment combinations in R/R AML have not been previously reported.Methods: All R/R myeloid patients (including AML, myelodysplastic syndrome (MDS), and blastic plasmacytoid dendritic cell neoplasm (BPDCN)) treated with VEN combinations in the salvage setting were reviewed.Results: Forty‐three patients with median age 68 (range, 25–83) were treated for AML (91%), MDS (5%), or BPDCN (5%). Most (n = 36, 84%) were ≥ salvage‐2 treatment status, including prior hypomethylating agent (HMA) in 77%. In combination with VEN, most patients received HMA therapy (n = 31, 72%); eight (19%) received low‐dose cytarabine (LDAC). Patients received a median of 2 treatment cycles (range, 1–4). Objective response was observed in 9 (21%) patients, including 2 complete responses (CR), 3 CRi, and 4 morphologic leukemia‐free state (MLFS). Median survival was 3.0 months (range, 0.5–8.0), and estimated 6‐month survival was 24%. Responses were observed in five (24%) of 21 patients with intermediate‐risk cytogenetics, 3 (27%) of 11 IDH1/2‐mutant, and 4 (50%) of 8 RUNX1‐mutated patients. Two (20%) of 10 TP53‐mutated patients responded; both had concurrent RUNX1 mutations. Of the 3 (15%) responding patients with adverse cytogenetics, all had concurrent RUNX1 mutations.Conclusion: Low‐intensity chemotherapy, including HMAs or LDAC, in combination with VEN is a viable salvage option, even in multiply relapsed/refractory patients with AML, MDS, and BPDCN. Notable responses were identified in patients with diploid/intermediate cytogenetics, RUNX1, and/or IDH1/2 mutations.

The therapeutic armamentarium of acute myeloid leukemia (AML) has rapidly expanded in the past few years, driven largely by translational research into its genomic landscape and an improved understanding of mechanisms of resistance to conventional therapies. However, primary and secondary drug resistance remains a substantial problem for most patients. Research into the mechanisms of resistance to these new agents is informing the development of the next class of AML drugs and the design of combination regimens aimed at optimally exploiting therapeutic vulnerabilities, with the ultimate goal of eradicating all subclones of the disease and increasing cure rates in AML.Significance: AML is a heterogeneous disease, characterized by a broad spectrum of molecular alterations that influence clinical outcomes and also provide potential targets for drug development. This review discusses the current and emerging therapeutic landscape of AML, highlighting novel classes of drugs and how our expanding knowledge of mechanisms of resistance are informing future therapies and providing new opportunities for effective combination strategies.