TG Therapeutics' leukemia combo clears phase 3, aims for 2020 filing

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TG Therapeutics’ combination comprises ublituximab, an anti-CD20 antibody, and umbralisib,a PI3K-delta inhibitor. (Pixabay)

TG Therapeutics’ experimental combination staved off cancer in patients with chronic lymphocytic leukemia (CLL), beating the control arm and teeing up an FDA filing by the end of the year.

The company didn’t share numbers, saving them for medical meetings and saying only that patients taking the combination of umbralisib and ublituximab, dubbed U2, had a “statistically significant improvement” in progression-free survival over those taking Roche’s Gazyva along with chemo drug chlorambucil. But the results were good enough to prompt an independent board to recommend stopping the study early for “superior efficacy.”

The phase 3 study tested the U2 combination against the Gazyva/chlorambucil combo, a front-line treatment for CLL. Of the 420 patients in the study, about 60% had never undergone treatment, while the remaining 40% had cancer that had returned after treatment or had not responded to treatment in the first place. The company will seek approval in both patient populations.

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“This outcome sets the stage for the potential approval of U2 as a novel, chemotherapy-free, treatment regimen for patients with CLL, whether they have relapsed from or are refractory to a prior therapy or have never been treated before,” said TG Therapeutics CEO Michael Weiss in a statement.

Patients with CLL may receive chemotherapy, monoclonal antibodies, targeted drugs or any combination of them as a front-line treatment. Some regimens work well, with patients living for years without needing further treatment, but patients eventually relapse and need different options.

Ublituximab is an anti-CD20 antibody and umbralisib is a PI3K-delta inhibitor, a class of drugs dogged by safety issues. Though TG kept safety data under wraps, the data safety monitoring board did not raise any safety concerns about the trial in March 2019, saying it should continue as planned. The company is testing umbralisib in other kinds of blood cancer including follicular lymphoma and marginal zone lymphoma.

"Today’s outcome marks the first successful Phase 3 trial of a PI3K delta-based regimen in a CLL patient population that included previously untreated patients,” said John Gribben, M.D., a professor at Barts Cancer Institute in London, U.K., and global study chair for the study. “CLL remains incurable and new treatment options are still very much needed, particularly those that provide a differentiated mechanism and safety profile from our currently available treatment options.”