MCL1 and acute myeloid leukemia: The phase 1 trial assessing the safety, tolerability, pharmacokinetics, and efficacy of AMG-397 in patients with MM, NHL, and AML (NCT03465540) (Table 4) was placed on hold by the FDA in September 2019 after the discovery of a safety signal for cardiac toxicity, prompting Amgen, the drug manufacturer, to voluntarily halt the phase 1 studies of AMG-176 as a precaution, emphasizing the importance of clinical trials in establishing whether a wide enough therapeutic window can be found for MCL1 inhibitors to allow the use of this novel subclass of BH3 mimetics in patients.