In this study, common variable immunodeficiency (CVID) patients will all receive the study drug, leniolisib, for a treatment period of 6 months. Participants will start on a lower dose of leniolisib, followed by a mid and then a higher dose level. The primary goal is to assess the safety and tolerability of leniolisib, and secondary goal is to assess the potential for leniolisib to provide benefits for patients.