---
schema_version: "secwatch.filing_event.v1"
accession: "0000950170-25-112898"
form_type: "8-K"
ticker: "ATRA"
cik: "0001604464"
company_name: "Atara Biotherapeutics, Inc."
filed_at: "2025-09-04T23:59:59+00:00"
generated_at: "2026-05-17T08:18:05.762473+00:00"
event_type: "leadership"
sentiment: "neutral"
materiality_score: 0.4
calibrated_materiality_score: 0.4
confidence: "high"
source: SEC EDGAR
---

# Three directors resign from Atara Biotherapeutics board; Ciongoli named Chair

## Summary
- Directors Ameet Mallik, Pascal Touchon, and Maria Grazia Roncarolo resigned voluntarily effective Sept 2, 2025.
- Board size reduced from 10 to 7 directors as of the same date.
- Gregory A. Ciongoli appointed as Chair to succeed Pascal Touchon.

## SEC filing metadata
- accession: 0000950170-25-112898
- form_type: 8-K
- ticker: ATRA
- cik: 0001604464
- company_name: Atara Biotherapeutics, Inc.
- filed_at: 2025-09-04T23:59:59+00:00
- event_type: leadership
- sentiment: neutral
- materiality_score: 0.4
- calibrated_materiality_score: 0.4
- confidence: high
- sec_items: 5.02
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1604464/000095017025112898/0000950170-25-112898-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1604464/000095017025112898/atra-20250902.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0000950170-25-112898
- JSON: https://secwatch.observer/filing/0000950170-25-112898.json
- Plain text: https://secwatch.observer/filing/0000950170-25-112898.txt

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