Acalabrutinib Plus Rituximab for the Treatment of Elderly or Low- to Intermediate-Risk Younger Untreated Mantle Cell Lymphoma

The purpose of this study is to evaluate the efficacy and safety of Acalabrutinib plus Rituximab for the treatment of elderly or low- to intermediate-risk younger untreated mantle cell lymphoma Treatrment: 1. Acalabrutinib: 100 mg bid po, continue treatment until disease progression, intolerable toxicity, or completion of 24 months of treatment 2. Rituximab: 375 mg/m2 IV, once weekly during the first cycle, then once monthly for 12 months, followed by once every 2 months, for a maximum of 24 months. The primary study endpoint is the investigator-assessed complete response (CR) rate at 12 months.