TG clears board data review on way to key PFS readout

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TG expects to have data on PFS, the primary endpoint, late in 2019 or early in 2020. (CC0 Public Domain)

A data safety monitoring board has recommended the continuation of TG Therapeutics’ phase 3 chronic lymphocytic leukemia trial. The board made the call after assessing the safety and efficacy data generated to date.

The trial, UNITY-CLL, is subject to periodic, preplanned reviews to assess whether it should carry on, or if its inability to meet the primary endpoint or safety problems necessitate an early halt. At the latest review, the board did not raise any safety concerns, found the study was not futile and said it should continue as planned.

TG welcomed the news.

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"We are highly encouraged that based on the progression-free survival data accumulated to date, the UNITY-CLL DSMB determined that the study was not futile and supported continuation of the trial as planned,” TG CEO Michael Weiss said in a statement.

The news sent TG’s stock up 9% in premarket trading, although the stock is still down on the price it traded at prior to the board’s previous assessment of the trial in September. Back then, TG dropped plans to seek an accelerated approval based on overall response data because they “were not sufficiently mature to conduct the analysis.”

That lengthened TG’s path to market and raised questions about how its ublituximab-umbralisib (U2) combination is performing in the phase 3. TG expects to have data on PFS, the primary endpoint, late in 2019 or early in 2020 that will either quash or confirm doubts about the efficacy of U2. 

The trial is advancing in parallel to a phase 2b study that is assessing U2 in non-Hodgkin’s lymphoma patients. The board reviewed safety data from the phase 2b and phase 3 trials and found no reason to stop the studies.

That lessens one of the concerns about U2. Umbralisib is a PI3K delta inhibitor, a class of drug that has been held back by toxicity. Autoimmune and infectious toxicities dogged the first FDA-approved PI3K inhibitor, Gilead’s Zydelig, and have restricted its use.