SOUTH SAN FRANCISCO, Calif. (AP) _ Atara Biotherapeutics Inc. (ATRA) on Wednesday reported a loss of $50.9 million in its second quarter.

On a per-share basis, the South San Francisco, California-based company said it had a loss of $1.15.

The results did not meet Wall Street expectations. The average estimate of three analysts surveyed by Zacks Investment Research was for a loss of 97 cents per share.

Atara Biotherapeutics shares have more than doubled since the beginning of the year. The stock has more than doubled in the last 12 months.

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This story was generated by Automated Insights (http://automatedinsights.com/ap) using data from Zacks Investment Research. Access a Zacks stock report on ATRA at https://www.zacks.com/ap/ATRA