High surface expression of CD49d (VLA-4) and CD79b prior to and after therapy correlates with acalabrutinib resistance in pts with CLL. Targeting CD49d may prove an effective strategy to overcome acalabrutinib resistance in CD49d high pts….CD49d may contribute to acalabrutinib resistance in CLL by enhancing cell survival through adhesion to the tumor microenvironment and may serve as a predictive marker to identify pts at high risk of developing resistance to acalabrutinib.