Mizuho on Atara Biotherapeutics – Distinguishing between small numbers and scientific failure

  • Atara Biotherapeutics Inc ATRA published its planned interim analysis communication for its phase 2 ATA188 trial in progressive multiple sclerosis. The shares fell more than 50%.
  • Mizuho thinks investors need to make a clear distinction when reassessing their position after these inconclusive results and reporting without sample size adjustments.
  • Is there a new risk with the science and the data itself? Mizuho writing :
  • Interim data was based primarily on Phase 1 data, which showed that improvement in EDSS at six months was >85% predictive of that at 12 months. But the study itself was small, with just 24 patients.
  • The data was even smaller, with EDSS data on 34 patients at six months and 15 patients at twelve months.
  • Analyst notes single-arm ATA188 Phase 1 dose and time-dependent response, sustained improvement in disability EDSS in the range of 33-50% in dose cohorts higher, and similar data from the autologous sister compound ATA190.
  • Mizuho maintains the price target at $39 with a buy rating.
  • Price action: ATRA shares are down 55% at $3.90 in the market’s last check session on Wednesday.

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