The Bruton's tyrosine kinase (BTK) inhibitor zanubrutinib (Brukinsa), which was previously approved by the FDA for treatment of mantle cell lymphoma, Waldenström's macroglobulinemia, and relapsed or refractory marginal zone lymphoma, has now been approved for treatment of chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL) in adults. The BTK inhibitors ibrutinib (Imbruvica) and acalabrutinib (Calquence) were approved earlier for treatment of CLL and SLL.

The Bruton's tyrosine kinase (BTK) inhibitor pirtobrutinib (Jaypirca – Lilly) has received accelerated approval from the FDA for treatment of relapsed or refractory mantle cell lymphoma (MCL) in adults who received ≥2 prior lines of systemic therapy, including a BTK inhibitor. Accelerated approval was based on the response rate. The BTK inhibitors ibrutinib (Imbruvica), acalabrutinib (Calquence), and zanubrutinib (Brukinsa) are also approved for treatment of MCL.

The FDA has approved the Bruton tyrosine kinase (BTK) inhibitor acalabrutinib (Calquence – AstraZeneca) for oral treatment of relapsed or refractory mantle cell lymphoma. Acalabrutinib is the second BTK inhibitor to be approved for this indication; ibrutinib (Imbruvica) was approved in 2013.

Ibrutinib inhibits other kinases in addition to BTK and has been associated with severe adverse effects, particularly atrial fibrillation, infection, rash, and bleeding, that may be related to inhibition of kinases other than BTK.1 Acalabrutinib is a more selective BTK inhibitor than ibrutinib; whether this improved selectivity results in fewer adverse events is unclear.2

FDA approval of acalabrutinib was based on the results of a single-arm trial in 124 patients who had received a median of 2 previous therapies for mantle cell lymphoma. After a median follow-up of 15.2 months, 81% of patients treated with acalabrutinib 100 mg twice daily achieved an overall response and 40% achieved a complete response. The Kaplan-Meier estimated median overall survival rate at 12 months was 87%.3

The most common severe adverse events in the pivotal trial were neutropenia (10%), anemia (9%), and pneumonia (5%). There were no cases of atrial fibrillation and one case of severe hemorrhage. No head-to-head trials comparing acalabrutinib with ibrutinib are available to date.

The cost of 30 days' treatment with Calquence (100 mg bid) is $14,064 and with Imbruvica (560 mg once daily) is $12,180.4

1. AP Bye et al. Severe platelet dysfunction in NHL patients receiving ibrutinib is absent in patients receiving acalabrutinib. Blood Adv 2017; 1:2610.
2. J Wu et al. Acalabrutinib (ACP-196): a selective second-generation BTK inhibitor. J Hematol Oncol 2016; 9:21.
3. M Wang et al. Acalabrutinib in relapsed or refractory mantle cell lymphoma (ACE-LY-004): a single-arm, multicentre, phase 2 trial. Lancet 2018; 391:659.
4. Approximate WAC. WAC = wholesale acquisition cost or manufacturer's published price to wholesalers; WAC represents a published catalogue or list price and may not represent an actual transactional price. Source: AnalySource® Monthly. October 5, 2018. Reprinted with permission by First Databank, Inc. All rights reserved. ©2018. www.fdbhealth.com/policies/drug-pricing-policy.

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The FDA has approved idelalisib (Zydelig – Gilead), an oral kinase inhibitor, for use in combination with rituximab (Rituxan) for treatment of relapsed chronic lymphocytic leukemia (CLL). It is also approved as monotherapy for treatment of relapsed follicular lymphoma and relapsed small lymphocytic lymphoma (both are subtypes of indolent non-Hodgkins lymphoma) in patients who have received at least two prior systemic therapies.

Obinutuzumab (Gazyva – Genentech), a humanized anti-CD20 monoclonal antibody, has been approved by the FDA for use in combination with chlorambucil (Leukeran) in patients with previously untreated chronic lymphocytic leukemia (CLL). Two other anti-CD20 antibodies, rituximab (Rituxan) and ofatumumab (Arzerra), were previously approved for treatment of CLL.

The FDA has approved ibrutinib (eye broo' ti nib; Imbruvica – Janssen/Pharmacyclics), an oral kinase inhibitor, for second-line treatment of chronic lymphocytic leukemia (CLL). It is the first kinase inhibitor to be approved for CLL. Ibrutinib was approved earlier for second-line treatment of mantle cell lymphoma, a rare form of B-cell non-Hodgkins lymphoma.