---
schema_version: "secwatch.filing_event.v1"
accession: "0001193125-23-169508"
form_type: "8-K"
ticker: "ACLX"
cik: "0001786205"
company_name: "Arcellx, Inc."
filed_at: "2023-06-20T23:59:59+00:00"
generated_at: "2026-06-13T21:34:03.761562+00:00"
event_type: "regulatory"
sentiment: "negative"
materiality_score: 0.85
calibrated_materiality_score: 0.85
confidence: "high"
source: SEC EDGAR
---

# Arcellx receives FDA clinical hold on CART-ddBCMA after patient death in Phase 2 trial

## Summary
- FDA placed clinical hold on CART-ddBCMA IND for relapsed/refractory multiple myeloma on June 16, 2023, after a recent patient death.
- FDA cleared continued dosing of patients who have already undergone lymphodepletion.
- Company believes limitations on bridging therapy are a contributing factor; working with FDA to amend protocol to expand options.
- Manufacturing success rate remains 100% while ramping Lonza to full scale; 14 clinical sites opened and enrollment tracking to expectations.
- Partners include Kite Pharma; CEO expresses confidence in best-in-class potential based on clinical profile to date.

## SEC filing metadata
- accession: 0001193125-23-169508
- form_type: 8-K
- ticker: ACLX
- cik: 0001786205
- company_name: Arcellx, Inc.
- filed_at: 2023-06-20T23:59:59+00:00
- event_type: regulatory
- sentiment: negative
- materiality_score: 0.85
- calibrated_materiality_score: 0.85
- confidence: high
- sec_items: 8.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1786205/000119312523169508/0001193125-23-169508-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1786205/000119312523169508/d443230d8k.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001193125-23-169508
- JSON: https://secwatch.observer/filing/0001193125-23-169508.json
- Plain text: https://secwatch.observer/filing/0001193125-23-169508.txt

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