Why Atara Biotherapeutics Shares Are Plummeting Today - Atara Biotherapeutics (NASDAQ:ATRA)

Atara Biotherapeutics Inc ATRA completed the planned Interim Analysis of the ATA188 Phase 2 study (EMBOLD) in progressive multiple sclerosis patients.
The analysis' primary focus was on expanded disability status scale (EDSS) improvement at six months and overall safety, and also included evaluation of EDSS beyond six months for patients.
The analysis was also designed to assess if a sample size increase was needed. It was planned to occur before enrolling patient 80 to enable an increased sample size if needed.
EDSS improvement appeared to be predictive of improvement at 12 months.
Also See: Read Why Did HC Wainwright Cut Price Target On Atara Biotherapeutics.
There was no sufficient dataset to draw conclusions about the predictive value of six months EDSS improvements for 12 months.
The safety monitoring committee believes the six-month interim endpoint may be an inaccurate measure. It recommended continuing the study without sample size adjustment until the final analysis.
The final read-out of the study's primary endpoint of confirmed EDSS improvement at 12 months is planned for October 2023.
Price Action: ATRA shares are down 52% at $4.16 during the premarket session on the last check Wednesday.

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Atara Biotherapeutics Shares Are Plummeting - Read Why