MCL1 and leukemia: For example, the addition of the MCL-1 inhibitor obatoclax to bortezomib was able to overcome resistance to proteasome inhibition and restore sensitivity to this agent.33 Likewise, there is evidence suggesting that a similar approach would be efficacious with the second-generation proteasome inhibitor carfilzomib.35 Finally, the identification of leukemia subtypes in which proteasome inhibition is likely to have a beneficial effect is of high priority.