September 2021: For adult patients with Waldenström’s macroglobulinemia, the FDA has approved zanubrutinib (Brukinsa, BeiGene) (WM).
In ASPEN (NCT03053440), zanubrutinib was compared to ibrutinib in patients with MYD88 L265P mutation (MYD88MUT) WM. Cohort 1 (n=201) patients were randomly assigned to receive either zanubrutinib 160 mg twice day or ibrutinib 420 mg once daily until disease progression or intolerable toxicity. Patients in Cohort 2 were given zanubrutinib 160 mg twice daily and were either MYD88 wildtype (MYD88WT) or MYD88 mutation unknown WM (n=26 and 2, respectively).
Response rate, defined as a partial response (PR) or better as judged by an independent review committee using conventional consensus response criteria from the International Workshop on Waldenström’s Macroglobulinemia-6, was the primary efficacy outcome used to support approval. The length of reaction was another efficacy outcome metric (DOR).
The zanubrutinib arms were approved based on a non-comparative evaluation of response and DOR. The zanubrutinib arm had a response rate of 77.5 percent (95 percent confidence interval: 68.1,85.1). The zanubrutinib group had a 94.4 percent event-free DOR at 12 months (95 percent CI: 85.8, 97.9). Response (CR+VGPR+PR) was detected in 50% of the Cohort 2 participants, according to IRC (13 out of 26 response evaluable patients; 95 percent CI: 29.9, 70.1).
Neutrophil count decreased, upper respiratory tract infection, platelet count decreased, rash, haemorrhage, musculoskeletal pain, haemoglobin decreased, bruising, diarrhoea, pneumonia, and cough are the most common adverse reactions, including laboratory abnormalities, reported with zanubrutinib (20 percent).
The recommended dose of zanubrutinib is 160 mg twice a day or 320 mg once a day.