Business Context and Reporting Period
Company: Assembly Biosciences, Inc.
Filing Type: Form 8-K (Current Report)
Date: August 8, 2025
Subject: Interim results from the Phase 1b portion of the Phase 1a/b clinical study for ABI-5366, an investigational long-acting herpes simplex virus (HSV) helicase-primase inhibitor candidate for recurrent genital herpes.
Key Financial Metrics
This filing is a Regulation FD disclosure regarding clinical trial results and does not contain financial statements. The filing text does not provide values for revenue, profit, cash flow, margins, debt, or liquidity.
Material Changes and Clinical Results
The Company reported highly potent antiviral activity for ABI-5366 in the Phase 1b study cohort evaluating a 350 mg weekly dose over a 29-day period. Key interim results include:
- HSV-2 Shedding Rate (Primary Endpoint): 94% reduction compared to placebo (p < 0.001), exceeding the study target of 80%-85% reduction.
- Genital Lesion Rate (Secondary Endpoint): 94% reduction compared to placebo (p < 0.001).
- High Viral Load Episodes: Episodes with >10,000 copies/mL HSV DNA were reduced by 98% compared to placebo (p < 0.001).
- Safety and Tolerability: ABI-5366 was well-tolerated at oral doses up to 350 mg weekly in HSV-2 seropositive participants.
- Pharmacokinetics: Profile supports once-weekly dosing and potential for once-monthly oral dosing regimens.
Outlook, Management Commentary, and Next Steps
Based on these data, the Company expects to move directly into Phase 2 clinical study preparation in parallel with the completion of the current Phase 1b study. This includes an ongoing cohort evaluating a monthly oral dosing regimen. Additionally, the in-life portions of chronic toxicology studies for ABI-5366 are complete and are expected to support longer-term dosing in Phase 2.
Investor Verification Checklist
- Verify the full text of the press release attached as Exhibit 99.1 for detailed statistical analysis.
- Confirm the timeline for the initiation of the Phase 2 clinical study.
- Monitor the completion status of the ongoing monthly dosing cohort within the Phase 1b study.
- Review future filings for updates on the chronic toxicology study reports.