Salarius' rare cancer drug breaks free from one FDA partial hold, but another study remains in limbo

Seven months after the FDA placed two trials of Salarius Pharmaceuticals’ lead asset seclidemstat in rare cancer indications on hold in the wake of a patient death, the regulator has given the green light for one of the studies to proceed.

The Texas-based biotech paused enrollment on a phase 1/2 trial assessing the oral LSD1 inhibitor among patients with Ewing sarcoma—a rare and deadly pediatric cancer that forms in the bone or connective tissues. The FDA action followed a patient death amid the trial, one that was classified as a so-called suspected unexpected serious adverse reaction.

The biotech has since been working with the FDA to provide safety and clinical information on seclidemstat’s risk-benefit profile, Salarius President and CEO David Arthur said in a May 9 release. “We look forward to working with our clinical trial investigators to resume enrollment with the goal of advancing the development of seclidemstat as a potential treatment option,” Arthur said.

The three-arm trial is now in a dose-expansion stage and aims to enroll an arm of 30 patients with Ewing sarcoma who will receive seclidemstat in combination with chemotherapy. One of the trial’s other arms consists of a cohort of 15 patients with myxoid liposarcoma—a form of sarcoma that affects fat cells—receiving seclidemstat by itself.

The third arm had consisted of patients with FET-rearranged sarcomas, which share a similar biology to Ewing sarcoma, who are receiving seclidemstat alone. The biotech has already halted this arm after the drug failed to show an effect as a monotherapy in this cohort.

In addition to sarcoma, Salarius is exploring the therapy’s potential in several cancers with high unmet medical need, including a phase 1/2 study in hematologic cancers at MD Anderson Cancer Center. The FDA placed this study on hold at the same time, and Salarius said today that it's "supporting MD Anderson in its efforts to have its partial clinical hold lifted."

Salarius has one other asset in its pipeline: an oral, small-molecule protein degrader called SP-3164, which is designed to degrade oncoproteins implicated in hematological and solid tumors. SP-3164 is expected to enter the clinic in the second quarter.

Despite the FDA's decision, Salarius’ shares sunk 13% this morning, from $2.16 at market close Monday to $1.87 today at 10:30 a.m. ET May 9.