The investigational anti-CD20 monoclonal antibody ublituximab is safe and has good antitumor activity in patients with B-cell non-Hodgkin lymphoma (B-NHL) or chronic lymphocytic leukemia (CLL) who have previously received the anti-CD20 antibody rituximab, results from a phase I/II trial suggest.

Ublituximab is engineered to have a low fucose content. This feature gives it enhanced antibody-dependent cellular cytotoxicity relative to other anti-CD20 antibodies, especially against tumors having low expression of that protein, as may occur in the development of rituximab resistance.

In the trial, nearly half of the 35 patients studied had a complete or partial response to ublituximab, including nearly one-third of those whose disease was refractory to rituximab (Rituxan) ( Br J Haematol. 2017 Apr;177[2]:243-53 ). The main adverse events were infusion-related reactions, fatigue, pyrexia, and diarrhea, but almost all were lower grade.

“Ublituximab was well tolerated and efficacious in a heterogeneous and highly rituximab–pretreated patient population,” said the investigators, who were led by Ahmed Sawas, MD , at the Center for Lymphoid Malignancies, Columbia University Medical Center, N.Y.

The observed response rate is much the same as those seen with two other anti-CD20 antibodies – obinutuzumab (Gazyva)and ofatumumab (Arzerra)– in similar patient populations, and ublituximab may have advantages in terms of fewer higher-grade infusion-related reactions and shorter infusion time.

“Enhanced anti-CD20 [monoclonal antibodies] that are well tolerated and active in rituximab-resistant disease can provide meaningful clinical benefit to patients with limited treatment options,” the investigators noted.

The trial enrolled 27 patients with B-NHL and 8 patients with CLL (or small lymphocytic lymphoma) who had rituximab-refractory disease (defined by progression on or within 6 months of receiving that agent) or rituximab-relapsed disease (defined by progression more than 6 months after receiving it). They had received a median of three prior therapies.

The patients were treated on an open-label basis with ublituximab at various doses as induction therapy (3-4 weekly infusions during cycles 1 and 2) and then as maintenance therapy (monthly during cycles 3-5, then once every 3 months for up to 2 years). All patients received an oral antihistamine and steroids before infusions.

By the end of the trial, 60% of patients had discontinued treatment because of progression; 23% had discontinued because of adverse events, physician decision, or other reasons; and the remaining 17% had received all planned treatment, Dr. Sawas and his coinvestigators reported.

None of the patients experienced dose-limiting toxicities or unexpected adverse events. The rate of any-grade adverse events was 100%, and the rate specifically of grade 3/4 adverse events was 49%. The rate of serious adverse events (most commonly pneumonia) was 37%.

The leading nonhematologic adverse events were infusion-related reactions (40%; grade 3/4, 0%), fatigue (37%; grade 3/4, 3%), pyrexia (29%; grade 3/4, 0%), and diarrhea (26%; grade 3/4, 0%).

The leading hematologic adverse events were neutropenia (14%; grade 3/4, 14%), with no associated infections; anemia (11%; grade 3/4, 6%); and thrombocytopenia (6%; grade 3/4, 6%), with no associated bleeding.

The overall response rate was 45% (44% in the B-NHL cohort and 50% in the CLL cohort); the majority of responses were partial responses. Notably, the rate was 31% among the subset of patients who had rituximab-refractory disease.

The median duration of response to ublituximab was 9.2 months, and the median progression-free survival was 7.7 months.

“Anti-CD20 therapy has demonstrated the greatest benefit in combination, traditionally with multidrug chemotherapy–based regimens,” the investigators noted. “While the introduction of novel targeted therapies has shifted the treatment paradigm of CLL and indolent lymphoma, the activity of these agents is likely to be potentiated by the addition of an anti-CD20 [monoclonal antibody], given their different mechanisms of action.”

In fact, several multidrug, non–chemotherapy-based regimens are showing promising efficacy and milder toxicity in early trials, they pointed out. “In similar fashion, ublituximab is being evaluated for the treatment of NHL or CLL in combination with other agents,” such as the immunomodulator lenalidomide (Revlimid) and the Bruton tyrosine kinase inhibitor ibrutinib (Imbruvica).

TG Therapeutics funded the trial. Dr. Sawas disclosed that he receives research funds from TG Therapeutics.