The Food and Drug Administration (FDA) has placed a clinical hold on two late-stage trials run by Intellia Therapeutics. These trials test a one-time CRISPR-based therapy, nexiguran ziclumeran (nex-z), for the rare disease transthyretin amyloidosis.
The hold follows a serious adverse event: a patient developed grade 4 liver enzyme elevations and high bilirubin levels after receiving the treatment. The individual remains hospitalised under monitoring.
Intellia had already paused all dosing and screening in these trials earlier in the week. The FDA delivered the verbal hold and said a formal notice will arrive within 30 days.
The company’s shares plunged about 17 % in after-hours trading following the announcement. Some analysts believe the long-term impact may be limited given the earlier pause.
Transthyretin amyloidosis (ATTR) is a degenerative condition where misfolded proteins build up in the body and damage the heart or nerves. Nex-z was designed to offer a lasting one-dose gene-editing fix. The hold marks a critical safety checkpoint for this emerging class of therapies.
