---
schema_version: "secwatch.filing_event.v1"
accession: "0001193125-24-246627"
form_type: "8-K"
ticker: "SPRO"
cik: "0001701108"
company_name: "Spero Therapeutics, Inc."
filed_at: "2024-10-29T23:59:59+00:00"
generated_at: "2026-05-30T09:19:03.390851+00:00"
event_type: "other_material"
sentiment: "negative"
materiality_score: 0.8
calibrated_materiality_score: 0.8
confidence: "high"
source: SEC EDGAR
---

# Spero suspends SPR720 development after Phase 2a miss; cuts workforce 39%, extends cash runway to mid-2026

## Summary
- SPR720 Phase 2a interim analysis did not meet primary endpoint; 3 cases of reversible grade 3 hepatotoxicity at 1,000 mg dose.
- Company restructuring with ~39% workforce reduction; expects ~$1.1M in cash restructuring charges.
- Unaudited Q3 2024 cash ~$76.3M; cash runway extended into mid-2026.
- Tebipenem HBr PIVOT-PO Phase 3 trial on track for enrollment completion in 2H 2025.
- IND cleared for SPR206 Phase 2 trial in HABP/VABP, contingent on non-dilutive funding.

## SEC filing metadata
- accession: 0001193125-24-246627
- form_type: 8-K
- ticker: SPRO
- cik: 0001701108
- company_name: Spero Therapeutics, Inc.
- filed_at: 2024-10-29T23:59:59+00:00
- event_type: other_material
- sentiment: negative
- materiality_score: 0.8
- calibrated_materiality_score: 0.8
- confidence: high
- sec_items: 2.02, 2.05, 7.01, 8.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1701108/000119312524246627/0001193125-24-246627-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1701108/000119312524246627/d889032d8k.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001193125-24-246627
- JSON: https://secwatch.observer/filing/0001193125-24-246627.json
- Plain text: https://secwatch.observer/filing/0001193125-24-246627.txt

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