---
schema_version: "secwatch.filing_event.v1"
accession: "0000950170-25-030832"
form_type: "8-K"
ticker: "ATRA"
cik: "0001604464"
company_name: "Atara Biotherapeutics, Inc."
filed_at: "2025-03-03T23:59:59+00:00"
generated_at: "2026-05-25T17:46:42.562471+00:00"
event_type: "other_material"
sentiment: "negative"
materiality_score: 0.75
calibrated_materiality_score: 0.75
confidence: "high"
source: SEC EDGAR
---

# Atara Biotherapeutics cuts 50% of workforce, discontinues two CAR T programs

## Summary
- Reducing workforce by ~50%; expected to substantially complete by June 2025.
- Discontinuing all development for ATA3219 and ATA3431, including CAR T clinical studies.
- Estimated severance and related benefits of $3.0 million, primarily one-time cash charges.
- Additional details to be provided in the Q1 2025 10-Q filing.

## SEC filing metadata
- accession: 0000950170-25-030832
- form_type: 8-K
- ticker: ATRA
- cik: 0001604464
- company_name: Atara Biotherapeutics, Inc.
- filed_at: 2025-03-03T23:59:59+00:00
- event_type: other_material
- sentiment: negative
- materiality_score: 0.75
- calibrated_materiality_score: 0.75
- confidence: high
- sec_items: 2.05, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1604464/000095017025030832/0000950170-25-030832-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1604464/000095017025030832/atra-20250303.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0000950170-25-030832
- JSON: https://secwatch.observer/filing/0000950170-25-030832.json
- Plain text: https://secwatch.observer/filing/0000950170-25-030832.txt

This AI-assisted summary is a reading aid. Review the linked SEC EDGAR filing before relying on any specific claim.