Atara's stock sinks as multiple sclerosis cell therapy fails in phase 2, prompting rethink

This time, it’s conclusive. Sixteen months after saying it lacked the results to draw firm conclusions, Atara Biotherapeutics is back with data showing its multiple sclerosis cell therapy was hammered by placebo, prompting the biotech to outline plans to slash its spending on the program.

Atara shared an interim update from the phase 2 trial last year. Back then, management told investors it lacked “a sufficient dataset to draw conclusions” and would continue the study through to the 12-month analysis. Atara released top-line data from the study of its off-the-shelf T-cell immunotherapy ATA188 in people with non-active progressive multiple sclerosis after the markets closed Wednesday.

The headline finding is that ATA188 failed to improve disability compared to placebo after 12 months. Digging deeper, Atara revealed that it saw a 6% disability improvement in the treatment arm compared to a 16% improvement in the placebo group.

Those figures raise questions for Atara. The biotech is looking into why the improvement rate in patients on ATA188 fell from 33% in phase 1 to 6% in the latest study as well as why the improvement rate on placebo exceeded the 4% to 6% it expected to see in the patient population. 

The outcome of the investigation will inform the next steps for ATA188, but Atara is already planning to “significantly reduce its expenses” related to the candidate and focus its resources on its CAR-T pipeline. Through the shift in its focus and changes to its tab-cel partnership with Pierre Fabre, Atara expects to “meaningfully” extend its cash runway beyond the third quarter of 2025.

Investors are downbeat about Atara’s prospects, sending its share price down 40% to 73 cents in premarket trading Thursday, but the biotech has the time to turn things around. Over the coming year, the company plans to post preclinical data on its CD19-CD20 CAR-T candidate ATA3431 and preliminary phase 1 data on its CD19 CAR-T ATA3219 in lymphoma patients. Atara wants to study ATA3219 in autoimmune patients, too.