---
schema_version: "secwatch.filing_event.v1"
accession: "0001140361-21-040395"
form_type: "8-K"
ticker: "CSTL"
cik: "0001447362"
company_name: "CASTLE BIOSCIENCES INC"
filed_at: "2021-12-06T23:59:59+00:00"
generated_at: "2026-06-28T03:28:23.421727+00:00"
event_type: "m_and_a"
sentiment: "neutral"
materiality_score: 0.6
calibrated_materiality_score: 0.6
confidence: "high"
source: SEC EDGAR
---

# Castle Biosciences completes acquisition of Cernostics for $30M upfront cash, up to $50M earnout

## Summary
- Acquisition closed December 3, 2021; upfront cash consideration approximately $30 million.
- Up to $50 million additional earnout payable in cash or stock upon achieving 2022 commercial milestones.
- Merger agreement amended to cap stock issuance at 19.9% of outstanding shares for Nasdaq compliance.
- Cernostics becomes wholly owned subsidiary; post-closing adjustments and escrow apply.
- Financial statements of acquired business to be filed by amendment within 71 calendar days.

## SEC filing metadata
- accession: 0001140361-21-040395
- form_type: 8-K
- ticker: CSTL
- cik: 0001447362
- company_name: CASTLE BIOSCIENCES INC
- filed_at: 2021-12-06T23:59:59+00:00
- event_type: m_and_a
- sentiment: neutral
- materiality_score: 0.6
- calibrated_materiality_score: 0.6
- confidence: high
- sec_items: 1.01, 2.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1447362/000114036121040395/0001140361-21-040395-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1447362/000114036121040395/brhc10031497_8k.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001140361-21-040395
- JSON: https://secwatch.observer/filing/0001140361-21-040395.json
- Plain text: https://secwatch.observer/filing/0001140361-21-040395.txt

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