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ASH 2021: Phase II Study of Acalabrutinib and High-Frequency Low-Dose Subcutaneous Rituximab in Patients with Previously Untreated Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma (CLL / SLL)

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Dr. Danielle Wallace and colleagues presented this research at the American Society for Hematology annual meeting, which was held in December 2021 (ASH 2021).


The combination of the Bruton tyrosine kinase (BTK) inhibitor ibrutinib and the anti-CD20 monoclonal antibody rituximab is more effective than chemoimmunotherapy, and it is approved for the frontline treatment of chronic lymphocytic leukemia (CLL) and small lymphocytic lymphoma (SLL). However, ibrutinib can have serious cardiovascular side effects and off-target effects that can potentially interfere with the monoclonal antibody activity. Acalabrutinib is a more specific second-generation BTK inhibitor, has a better safety profile, and may make a better partner with rituximab.


  • This was a phase 2 clinical trial of acalabrutinib plus rituximab in patients with previously untreated CLL / SLL.
  • Acalabrutinib was taken orally twice per day.
  • Rituximab was given as high-frequency, low-dose subcutaneous injections, which has similar efficacy as standard intravenous injections but can be self-administered at home and limits loss of CD20 from CLL cell membranes.
  • 37 patients have been treated with a median follow-up of 14 months.
  • 27 patients have completed 12 cycles and been evaluated for response.
  • All patients responded with 1 complete response, 20 partial responses, and 6 partial responses with increased lymphocyte counts.
  • One patient with del17p and TP53 mutation had progressive disease after 25 cycles of therapy. All other patients remain in treatment.
  • No patients discontinued therapy due to adverse events, and no deaths were during treatment.
  • The most common adverse events were infusion-related reactions (62%), infections (57%), fatigue (51%), anemia (51%), headache (43%), rash or other skin changes (32%), low platelet levels (30%), bruising (27%), and diarrhea (22%).


Acalabrutinib plus high-frequency, low-dose subcutaneous rituximab is tolerable and effective. In addition, because it can be administered at home, it is more convenient and can decrease patient infection risk during pandemics. However, while it does control disease, it does not lead to undetectable measurable residual disease (uMRD).

Here is the link to the ASH 2021 abstract for more details.

Take care of yourself first.

Ann Liu, PhD