What happened
After reporting solid safety results for umbralisib as a monotherapy in chronic lymphocytic leukemia (CLL) patients who are intolerant to prior BTK (Imbruvica) or PI3K delta inhibitor (Zydelig) therapy, TG Therapeutics (TGTX 0.38%) 10.8% on Monday.
So what
The safety data was a poster presentation at this year's American Society of Clinical Oncology (ASCO) meeting in Chicago.
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In a study involving 47 evaluable patients who had discontinued Imbruvica or Zydelig because of intolerance, only 13% discontinued umbralisib because of an adverse event. It's also notable that at the time of the data cutoff, 47% of patients had been on umbralisib for longer than they had been on their prior treatment before discontinuing it.
The study's main goal is to evaluate progression-free survival (PFS) in this patient group. However, as of a median follow-up period of 9.5 months, PFS had not yet been reached.
Now what
We don't have PFS data in hand, but the fact that it hasn't been reached yet may indicate that the data will be good, particularly given that management noted in its presentation that nodal reductions were seen in "nearly all patients evaluable for response."
The fact umbralisib is well tolerated is a good thing, because while most people tolerate drugs like the mega-blockbuster Imbruvica, there's a significant need for other treatments in those who do discontinue it.
In mid-June, TG Therapeutics will report additional updated integrated safety data from umbralisib trials at the European Hematology Association annual congress. And then, topline data is expected from a phase 3 trial combining umbralisib with another of its drugs, ublituximab, in CLL this summer.
The two-drug combination (U2) is being compared head to head against the nine-figure-per-year Gazyva and chlorambucil, a chemotherapy. If TG Therapeutics' doublet outperforms Gazyva, and additional safety data remain good, then there's reason to believe that this stock's $1 billion valuation is low.
