---
schema_version: "secwatch.filing_event.v1"
accession: "0001739410-25-000052"
form_type: "8-K"
ticker: "RLYB"
cik: "0001739410"
company_name: "Rallybio Corp"
filed_at: "2025-04-08T23:59:59+00:00"
generated_at: "2026-05-23T19:05:50.572163+00:00"
event_type: "other_material"
sentiment: "negative"
materiality_score: 0.85
calibrated_materiality_score: 0.85
confidence: "high"
source: SEC EDGAR
---

# Rallybio discontinues RLYB212 for FNAIT after Phase 2 PK misses efficacy targets

## Summary
- Phase 2 PK results: RLYB212 concentrations near/ below assay LLoQ, missing minimum target of 3 ng/mL and predicted 6-10 ng/mL.
- No further enrollment; safety follow-up of sentinel participant continues; dose adjustment not feasible.
- RLYB116 confirmatory PK/PD study to initiate Q2 2025 with data from Cohorts 1 and 2 in 3Q/4Q 2025.
- REV102 (ENPP1 inhibitor, JV with Recursion) in IND-enabling studies; Phase 1 expected 2026; preclinical data 2H 2025.
- RLYB332 (long-acting matriptase-2 antibody) preclinical development ongoing for iron overload diseases.

## SEC filing metadata
- accession: 0001739410-25-000052
- form_type: 8-K
- ticker: RLYB
- cik: 0001739410
- company_name: Rallybio Corp
- filed_at: 2025-04-08T23:59:59+00:00
- event_type: other_material
- 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/1739410/000173941025000052/0001739410-25-000052-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1739410/000173941025000052/rlyb-20250408.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001739410-25-000052
- JSON: https://secwatch.observer/filing/0001739410-25-000052.json
- Plain text: https://secwatch.observer/filing/0001739410-25-000052.txt

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