Gossamer Bio is ending development of a lymphoma med after reports of two deaths and other serious adverse events in a phase 2 trial that was paused in March citing the “benefit/risk profile observed to date.”
In a short Securities and Exchange Commission filing Monday, Gossamer revealed that the safety issues included atrial fibrillation, a sudden death and a fatal brain bleed. The FDA has now placed a clinical hold on all trials of GB5121, which was being tested for primary central nervous system lymphoma.
March 17, Gossamer paused enrollment in the phase 1 portion of the trial, partly because of the benefit/risk profile and also to conserve cash for lead asset seralutinib. Now, all work related to GB5121 has been discontinued and the ongoing studies shelved.
Gossamer revealed GB5121, a central nervous system-penetrant Bruton’s tyrosine kinase (BTK) inhibitor, in October 2021, hoping to patch up a hole left in its pipeline by a two-time failed lead asset. At the time, CEO Faheem Hasnain called BTK a “validated target” but one that has yet to prove its abilities in the CNS.
GB5121, as well as another candidate GB7208, were “specifically optimized and designed” to overcome the limitations of other BTK inhibitors, with potential applications in oncology and autoimmune disorders, according to the chief executive. The goal was for GB5121 to address disease without causing side effects elsewhere.
Fellow BTK inhibitor GB7208 has been directed toward multiple sclerosis and remains in the discovery phase, according to Gossamer’s pipeline. Seralutinib, meanwhile, is in phase 2 testing for pulmonary arterial hypertension.
Gossamer's shares had dropped almost 10% to $1.01 in premarket trading Tuesday morning from a closing price of $1.12 on Monday—a day that also saw the stock sink over 10%.