BTK and mantle cell lymphoma: Agents targeting Bruton's tyrosine kinase (BTK), a core effector of the BCR signaling pathway (e.g., Ibrutinib) [6–8] and other BCR pathway members, such as phosphatidylinositol-3 kinase δ (PI3K-δ; e.g., Idelalisib) [9], have demonstrated high response rates in MCL [10]; however, these responses were not durable, suggesting a combinatory approach to enhance patient outcome.