Venetoclax is already approved for adults with chronic lymphocytic leukemia, small lymphocytic leukemia, and as part of a treatment combination in certain patients with acute myeloid leukemia.
The new findings suggest that the drug could also be a chemotherapy-free treatment option for HCL patients after the failure of multiple prior lines of therapy, including vemurafenib plus rituximab, the investigators wrote in a letter to the editor published in the New England Journal of Medicine.
Treatment options for such patients are limited, they noted.
Enrico Tiacci, MD, of the University of Perugia (Italy), and colleagues decided to explore the use of venetoclax in this patient population after reports of in vitro findings showing a possible benefit.
The investigators administered the drug off-label to six patients who had received vemurafenib plus rituximab as their most recent prior therapy; one was resistant and five relapsed after that therapy, they reported. Venetoclax was delivered in 29-day cycles.
After 6 or 12 cycles, two patients experienced complete remission with minimal residual disease (MRD), and one had partial remission, although each had incomplete platelet recovery.
Adding rituximab at a dose of 375 mg per square meter of body-surface area for three to eight cycles improved the depth of response in a patient who had a previous minor response, further reduced MRD in one who had a complete remission to venetoclax, and led to hematologic remission in one who had no response to venetoclax, they noted.
Progression-free survival ranged from 23 to 53-plus months in all five patients who did not have early progression and was similar or better than PFS seen after vemurafenib plus rituximab.
The main toxic effect of venetoclax was worsening of baseline neutropenia, which was sometimes complicated by infections or febrile neutropenia and was managed by dose reductions and granulocyte colony-stimulating factor.
“Thus, venetoclax with or without rituximab may serve as a safe and effective salvage option after failure of vemurafenib plus rituximab treatment, especially in patients who do not require a rapid recovery of blood count,” they concluded.
The study was supported by grants from Fondazione Associazione Italiana per la Ricerca sul Cancro and the Italian Ministry of Health.
A version of this article first appeared on Medscape.com.