Voxtalisib, an investigational agent that targets both mTOR and multiple isoforms of PI3K, showed “promising” efficacy with acceptable safety in patients with relapsed or refractory follicular lymphoma (FL), results of a phase 2 trial indicate.
Among 46 patients with FL, the overall response rate was 41.3%, including five (10.9%) complete responses. The median progression-free survival in this group was 58 weeks, reported Jennifer R. Brown, MD, PhD, of the Dana-Farber Cancer Institute in Boston, and her colleagues.
“The observed activity of voxtalisib in relapsed or refractory follicular lymphoma, notable for inducing complete responses in 10.9% of patients, warrants further study,” the investigators wrote in a study published in the Lancet Haematology.
Efficacy of the drug was limited, however, against aggressive malignancies, including mantle cell lymphoma (MCL), diffuse large B-cell lymphoma (DLBCL), or chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL).
Voxtalisib (XL765) is a potent inhibitor of all four class I PI3Ks, as well as a less robust inhibitor of the mammalian target of rapamycin (mTOR). In contrast, idelalisib (Zydelig) – which is approved by the Food and Drug Administration for treatment of relapsed/refractory FL or for CLL, in combination with rituximab – inhibits only the delta isoform of PI3K, and does not have marked anti–mTOR properties.
The investigators conducted an open-label, nonrandomized trial of voxtalisib in 30 centers in the United States, Belgium, France, Germany, the Netherlands, and Australia.
Adults 18 years or older with relapsed or refractory MCL, FL, DLBCL or CLL/SLL with Eastern Cooperative Oncology Group performance status of 2 or less were enrolled. All patients received voxtalisib 50 mg orally twice daily in 28-day continuous dosing cycles until progression or unacceptable toxicity.