MANCHESTER, ENGLAND – A new treatment option may soon be available for patients with chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL).
Zanubrutinib (Brukinsa), an irreversible, next-generation Bruton tyrosine kinase (BTK) inhibitor, is designed to minimize the off-target cardiovascular toxicities, such as atrial fibrillation and hypertension, seen with the first-generation ibrutinib (Imbruvica).
Zanubrutinib is already approved for use in mantle cell and marginal zone lymphomas and Waldenström’s macroglobulinemia.
Now it has also shown efficacy in CLL.
However, experts question whether the drug will find its place in an increasingly crowded space for the management of CLL.
Data from two phase 3 trials
The new data from two phase 3 clinical trials were presented recently at the British Society for Haematology 62nd annual scientific meeting, held in Manchester, England.
The ALPINE trial compared zanubrutinib with ibrutinib in 415 patients with CLL/SLL and showed that the novel drug was associated with a significant improvement in overall response rate, at 78% versus 63%.
This first interim analysis also showed that there was an increase in progression-free survival (PFS) with zanubrutinib, and crucially, it was associated with a lower atrial fibrillation/flutter rate than ibrutinib.
“These data support that more selective BTK inhibition, with more complete and sustained BTK occupancy, results in improved efficacy and safety outcomes,” said lead author Peter Hillmen, MBChB, FRCP, PhD, St. James’s University Hospital, Leeds, England.
The SEQUOIA study looked at zanubrutinib versus bendamustine plus rituximab in patients with untreated CLL/SLL with a 17p deletion and showed that PFS was improved with zanubrutinib by 58%.
Zanubrutinib was also associated with improved overall response rates and was well tolerated.
The results therefore “support the potential utility of zanubrutinib in the frontline management of patients with previously untreated CLL/SLL,” said lead author Talha Munir, MBBS, also of St. James’s University Hospital.
Improvement over ibrutinib
Ibrutinib, the first BTK inhibitor, “truly revolutionized the way we treat CLL,” commented Renata Walewska, MRCP, PhD, consultant hematologist at the Royal Bournemouth (England) Hospital and chair of the UKCLL Forum.
“But it has got quite a lot of, especially cardiac, problems, with atrial fibrillation and hypertension,” she said in an interview. The problem is that it acts not only as an inhibitor of Bruton kinase, but also affects other kinases, she explained.
Zanubrutinib is “much cleaner,” continued Dr. Walewska, who was lead author of the recently published British Society of Haematology guideline for the treatment of CLL.
However, the drug “is not that groundbreaking,” she commented, as acalabrutinib (Calquence), another next-generation BTK inhibitor, is already available for use in the clinic.
“We’re really lucky in CLL,” Dr. Walewska said, “we’ve got so many new drugs available, and it’s getting quite crowded. Trying to find a place for zanubrutinib is going be tricky.”
Lee Greenberger, PhD, chief scientific officer at the Leukemia & Lymphoma Society, commented that he “gives a lot of credit” to BeiGene, the company behind zanubrutinib, for “taking on these big studies.”
He said that, with the improvements in PFS and reduced atrial fibrillation with the drug, “there will be many clinicians paying attention to this and zanubrutinib could be preferred over conventional options.”
However, he agreed that it will have to compete with acalabrutinib, adding that, beyond BTK inhibitors, there are “a lot of options” for patients with CLL.
“That makes it very difficult for physicians to figure out what is the best type of therapy” to use in these patients, he added.
Dr. Greenberger told this news organization that further studies will need to demonstrate that zanubrutinib is associated with extended survival, which is “just not possible to show” at the moment with the current follow-up period.
He also noted that, in 10 years, ibrutinib will be off-patent, but zanubrutinib will not, at which point the “substantial” cost of the medication, which is a source of “hardship to patients,” will be increasingly relevant.