Study of Acalabrutinib and Rituximab in Untreated Elderly and/or Frail Patients With DLBCL

Treatment-naïve elderly and/or frail patients with DLBCL will be treated with acalabrutinib in combination with rituximab in a single arm. Study details include the following: * The study duration will be up to 108 weeks for each patient, including up to 28 days for screening and 104 weeks of treatment and follow-up. * The treatment duration will be up to 8 cycles for rituximab and 28 cycles for acalabrutinib both beginning at cycle 1.