Syndax’s lead cancer drug did not help patients with metastatic breast cancer live longer in a phase 3 study, leading the company to abandon an FDA filing in that indication.
The study tested the drug, a class I HDAC inhibitor called entinostat, in 600 patients with HR-positive, HER2-negative breast cancer that had spread to nearby tissues or elsewhere in the body. It found that adding entinostat to the hormone therapy exemestane did not extend patients’ lives compared to exemestane alone.
"We're disappointed that the combination of entinostat and exemestane did not demonstrate a survival benefit in this historically difficult-to-treat patient population," said Syndax CEO Briggs Morrison, M.D., in a statement.
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“Based on these results, we will not be filing a New Drug Application with the U.S. Food and Drug Administration for metastatic breast cancer,” he added.
The move comes a year after entinostat turned up disappointing results in a pair of phase 1b/2 trials combining it with checkpoint inhibitors. One study tested entinostat with Genentech’s Tecentriq in patients with triple-negative breast cancer, while the other paired it with Merck KGaA and Pfizer’s Bavencio in patients with ovarian cancer. The combinations failed to stave off cancer in both studies.
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At the time, Syndax put those trials on hold. It did the same for a pair of studies testing entinostat with Merck & Co.’s Keytruda in non-small cell lung cancer and melanoma. It put the PD-1 studies on hold to “prioritize our resources ahead of the [metastatic breast cancer] readout, at which time we will make a determination on next steps for the I-O combination program,” Morrison said at the time.
Needless to say, that bet has not paid off.
Moving forward, Syndax is working on a pair of earlier-stage programs: axatilimab, an anti-CSF-1R antibody for solid tumors and chronic graft-versus-host disease, and SNDX-5613, an inhibitor of the menin-MLL interaction for leukemias. The company presented early data for the latter at the first virtual session of the American Association for Cancer Research showing blocking menin could treat leukemia in patients with certain mutations.
“[We] believe SNDX-5613 has the potential to offer patients with both NPM1 mutant acute myeloid leukemia and MLL-r acute leukemias a much-needed, effective therapeutic option,” Morrison said. “We also anticipate the presentation of additional results from our ongoing Phase 1/2 trial of axatilimab in patients with chronic graft versus host disease in the fourth quarter of this year."