Addition of ublituximab to ibrutinib improves response in r/r CLL

Other adverse events of all grades occurring in 10% of patients or more for the combination and monotherapy arms, respectively, were: diarrhea (42% and 40%), fatigue (27% and 33%), insomnia (24% and 10%), nausea (22% and 21%), headache (20% and 28%), arthralgia (19% and 17%), cough (19% and 24%), abdominal pain (15% and 9%), stomatitis (15% and 9%), upper respiratory infection (15% and 12%), dizziness (15% and 22%), contusion (15% and 29%), anemia (14% and 17%), and peripheral edema (10% and 21%).

Neutropenia was higher in the experimental arm, 22% any grade, compared with 12% in the ibrutinib arm, although grade 3 or higher neutropenia was similar in the 2 arms. Other laboratory abnormalities were similar between the arms.

Efficacy

 The best ORR in the combination arm was 78%, with 7% achieving CR compared with 45% in the monotherapy arm with no CRs (P<0.001).

Nineteen percent of the combination arm achieved MRD negativity in peripheral blood compared with 2% of the monotherapy arm (P<0.01).

The reduction in lymph node size was similar between the arms.

In contrast, lymphocytosis was very different between the arms.

“As has been reported multiple times with targeted B-cell receptor signaling inhibitors,” Dr Sharman said, “patients treated with ibrutinib experienced rapid increase in their lymphocytes, returning approximately to baseline by 3 months and decreasing thereafter.”

“By contrast,” he continued, “those patients treated with the additional antibody had much more rapid resolution of their lymphocytosis. This was true whether patients were considered rituximab refractory or not.”

The investigators performed an additional analysis of ORR, this time including patients who achieved partial response with lymphocytosis (PR-L). These patients were not included in the primary endpoint because the iwCLL 2008 criteria had not yet been updated to include PR-L.

The best overall response including active PR-L patients was 83% in the experimental arm and 59% in the ibrutinib monotherapy arm (P<0.01).

PFS showed a trend toward improvement in the patients treated with the combination, with a hazard ratio of 0.559, which was not of statistical significance at the time of analysis.

The investigators concluded that the study met its primary endpoint, with a greater response rate and a greater depth of response than ibrutinib alone.

And the addition of ublituximab did not alter the safety profile of ibrutinib monotherapy.

TG Therapeutics, Inc, funded the study. 

*Data in the abstract differ from the meeting presentation.