Researchers at Seattle Children’s Hospital have paused testing of an experimental cancer cell therapy from biotechnology company 2Seventy Bio after a participant in an early-stage clinical trial died.
The trial, dubbed PLAT-08, is now on hold while researchers investigate the cause of the study volunteer’s death, and its potential link to 2Seventy’s treatment, which is made from patient T cells.
“The safety of every patient who participates in our studies or is treated with our therapies is the utmost priority for us, and we are in communication with [the Food and Drug Administration] while we assess the data surrounding this [severe adverse event], and the potential next steps for the study,” said Steve Bernstein, 2Seventy’s chief medical officer, in a Wednesday statement.
2Seventy’s treatment is designed to treat acute myeloid leukemia, a type of blood cancer that’s proven harder to target with cell therapy than other leukemias and lymphomas. The PLAT-08 study is the first time 2Seventy has tested a technology dubbed DARIC in humans.
The patient who died was the first to receive a higher dose after several others had been treated at an initial, lower level, 2Seventy said.
Acute myeloid leukemia, or AML, presents several challenges to cell therapy developers. Protein targets for AML cell therapies are expressed on healthy cells as well as cancerous ones, raising the risk of treatment-related toxicity. Past attempts to design an AML cell therapy have also had difficulty getting positive effects to last.
In response, 2Seventy designed its treatment, called SC-DARIC33, to be adjustable, capable of being turned on and off to minimize side effects. The company planned to test three doses after initial chemotherapy treatment, which is used to prepare patients for cell therapy.
Three participants in the study were treated with the low, initial dose through mid-March, 2Seventy showed in a presentation also posted Wednesday, and no dose-limiting toxicities were reported.
SC-DARIC33 is one of two experimental cell therapies 2Seventy has in clinical testing beyond its approved multiple myeloma medicine Abecma, which is sold by Bristol Myers Squibb. The company was spun out of Bluebird bio in November 2021, and is led by former Bluebird executives, including CEO Nick Leschly.
Shares in 2Seventy fell by more than 12% in Wednesday morning trading.