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CARiBOU Regimen Shows High Response Rates in Newly Diagnosed MCL

By MCLA Staff ·

Compiled by MCLA Staff. Reviewed by Annie Xiao, MD, City of Hope, Duarte, CA.

A new study found high response rates with a first-line treatment called CARiBOU for patients with mantle cell lymphoma (MCL). The regimen combines several established MCL treatments, including the chemotherapy drug cytarabine, with a targeted drug, BTK inhibitor acalabrutinib (Calquence). Among 41 patients, 90% achieved a complete metabolic response, meaning no active lymphoma could be detected on PET imaging after treatment.

Why is this study important to you?

Treatment for newly diagnosed MCL is changing. Researchers are increasingly studying ways to combine effective chemotherapy with newer targeted drugs, while trying to reduce some of the side effects associated with traditional intensive treatment.

CARiBOU is an example of this approach. It retains cytarabine, a chemotherapy drug that has long been an important part of intensive first-line MCL treatment, but uses it at a lower dose than some traditional regimens. At the same time, it adds acalabrutinib, a BTK inhibitor that blocks a signal MCL cells need to grow and survive.

What are the details of the study?

The phase 2 study included 41 previously untreated, fit patients with MCL. Patients received six cycles of treatment, alternating two multidrug combinations while taking acalabrutinib throughout treatment.

Results were encouraging:

  • 95% of patients responded to treatment.
  • 90% achieved a complete metabolic response.
  • Among patients who could be evaluated for measurable residual disease (MRD), 79% had no detectable MCL using a highly sensitive test capable of detecting approximately one cancer cell among one million cells (10⁻⁶). Using a less sensitive threshold (10⁻⁵), 94% were MRD negative.

The researchers initially used a higher dose of cytarabine but reduced it after several patients developed low platelet counts. After the dose was lowered, patients still had low platelet counts, but the percentage of cytarabine treatment cycles requiring platelet transfusions fell from 60% to 9%.

At 18 months, an estimated 79% of patients remained free from disease progression and 96% were alive.

Takeaway

CARiBOU produced very high complete response and MRD-negativity rates, suggesting that the regimen can produce deep remissions in previously untreated, fit patients with MCL.

The study also reflects two broader trends being explored in first-line MCL treatment: incorporating BTK inhibitors into initial treatment; and exploring modifications to intensive chemotherapy regimens to improve tolerability while preserving efficacy.

These early results are promising, but the study was small with 41 patients, and longer follow-up and additional research will be important to determine whether these deep responses translate into long-lasting remissions.

Sources

  • Smith SD, Sundaram S, Giri S, et al. Outcomes From the Multicenter ACCRU-LY-1804/CARiBOU Trial (Cytarabine, Acalabrutinib and Rituximab Integrated With Bortezomib-Based Outpatient Therapy) in 1st Line Mantle Cell Lymphoma. American Journal of Hematology. 2026;101(9):2190–2196.

  • OncLive. CARiBOU Regimen Drives Complete Metabolic Responses in First-Line Mantle Cell Lymphoma. September 6, 2026.

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