Mutations in Bruton’s tyrosine kinase (BTK) are associated with progression of chronic lymphocytic leukemia (CLL) in patients taking ibrutinib, according to a new study.
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Researchers analyzed a “real-life” cohort of CLL patients taking ibrutinib for about 3 years and found that patients with BTK mutations were significantly more likely to progress (P = .0005).
“Our findings support that mutational analysis should be considered in patients receiving ibrutinib who have residual clonal lymphocytosis, and that clinical trials are needed to evaluate whether patients with a BTK mutation may benefit from an early switch to another treatment,” wrote Anne Quinquenel, MD, PhD, of Hôpital Robert Debré, Université Reims (France) Champagne-Ardenne, and colleagues. Their report is in Blood.
The researchers studied 57 CLL patients who were still on ibrutinib after at least 3 years and provided fresh blood samples. The median time between the start of ibrutinib and sample collection was 3.5 years.
All 57 patients had minimal residual disease at baseline. Of the 55 patients with response data available, 48 had a partial response, and 7 had a partial response with lymphocytosis.
Mutational profiling was possible in 30 patients who had a CLL clone greater than or equal to 0.5 x 109/L.
BTK mutations were present in 17 of the 30 patients (57%). There were 20 BTK mutations in total, all were at C481, and 14 were at C481S.
The researchers also identified 15 patients with TP53 mutations and 4 patients with phospholipase Cg2 (PLCG2) mutations. All 4 patients with PLCG2 mutations also had a BTK mutation and a TP53 mutation.
However, there were no significant associations between BTK mutations and other mutations. BTK mutations were not associated with the number of previous therapies a patient received or the need for ibrutinib dose interruptions or reductions.
The researchers assessed CLL progression at median of 8.5 months from sample collection and found the presence of a BTK mutation was significantly associated with progression (P = .0005).
Of the 17 patients with a BTK mutation, 14 progressed with one case of Richter’s syndrome. Three patients who progressed were still on ibrutinib, nine patients received venetoclax, and two patients died without further treatment.
Of the 13 patients without BTK mutations, just two patients progressed. One patient died without further treatment, and the other received venetoclax.
The event-free survival was significantly shorter in patients with a BTK mutation than in those without (P = .0380), but there was no significant difference in overall survival.
This research was supported by Sunesis Pharmaceuticals and the Force Hemato (fonds de recherche clinique en hématologie) foundation. The researchers reported relationships with Janssen, Gilead, Roche, and AbbVie.
SOURCE: Quinquenel A et al. Blood. 2019 Jun 26. doi: 10.1182/blood.2019000854.