Assembly Biosciences

What Assembly Biosciences does

Assembly Biosciences (NASDAQ: ASMB) is a clinical-stage biopharmaceutical company developing oral, small-molecule antiviral therapeutics for serious viral and liver diseases. The company's pipeline rests on three proprietary mechanistic platforms: HSV helicase-primase inhibitors (ABI-5366 and ABI-1179, designed for once-weekly oral dosing for recurrent genital herpes), an NTCP inhibitor (ABI-6250, the only oral HDV entry inhibitor in clinical development, with a 4-day half-life enabling once-daily oral dosing and expansion into PBC/PSC), and a next-generation HBV capsid assembly modulator (ABI-4334, designed to disrupt both viral replication and cccDNA replenishment). All four candidates are investigational and none are commercially approved; ABI-1179 demonstrated a 98% reduction in HSV-2 shedding rate in Phase 1b (exceeding the company's 80-85% target), and ABI-5366 achieved a 76% reduction over 29 days.

The business is structurally pre-revenue and monetized through strategic collaboration rather than product sales. Under a 12-year collaboration signed in October 2023, Gilead Sciences provided a $100 million upfront payment, holds opt-in rights on multiple programs, increased its equity stake to 29.9% via a December 2024 $30.1 million investment, and exercised its option on the HSV helicase-primase program in December 2025 for $35 million plus up to $330 million in milestones. Gilead leads development and commercialization of optioned programs, while Assembly Bio retains US co-promotion and profit/cost-share election rights. The company has raised over $445 million in capital since 2023, including a $175 million public/private placement in August 2025 and a $115 million underwritten offering in May 2026, with cash runway extended into 2027.

Assembly Bio is headquartered in South San Francisco, California, employs 51-100 staff, and is led by CEO Jason Okazaki. Its lead customer base is effectively a single counterparty (Gilead Sciences) under a co-development/licensing structure; the patient populations it ultimately serves include individuals with recurrent genital herpes (>4 million in US and EU5), chronic HDV (12-72 million globally), chronic HBV (254 million globally, up to 1.1 million annual deaths), and cholestatic liver diseases such as PBC and PSC. The company has no approved products, no manufacturing infrastructure, and no consumer-facing channel — its marketing consists of scientific publications, investor relations, and clinical-trial listings.

Name

Assembly Biosciences

Legal name

Assembly Biosciences, Inc.

Website

https://assemblybio.com

Company type

Public

Founded year

2017

Operating status

Operating

Headcount range

51–100 employees

Short description

Assembly Biosciences is a clinical-stage biopharmaceutical company developing oral small-molecule antivirals for recurrent genital herpes, chronic hepatitis D and B, and cholestatic liver diseases, monetized through a 12-year Gilead Sciences collaboration rather than product sales.

Ownership category

akta.pro rank

Product category

Antiviral Therapeutics

NAICS

Research and Development in Biotechnology (except Nanobiotechnology) (541714), Pharmaceutical and Medicine Manufacturing (32541)

SIC

Pharmaceutical Preparations (2834), Services-Commercial Physical & Biological Research (8731)

akta.pro primary industry

Gene Therapy for Rare/Monogenic Diseases (HLAAACAE)

Keywords

• Antiviral therapeutics
• Hepatitis B treatment
• Hepatitis D treatment
• Helicase-primase inhibitors
• Capsid assembly modulators

Headquarters

HQ city

Carmel

HQ country

United States

HQ region

North America

Offices1 record

Markets served

GTM type

B2B

Offering type

Hardware or Manufacturing

Cost components

Technology or R&D, Personnel, Operations, Marketing or Sales

Revenue model

1. Licensing and Milestone Payments: As a clinical-stage biopharmaceutical company, Assembly Biosciences does not currently generate product revenue. The company receives funding through strategic collaborations, including upfront payments, milestone payments, and potential royalties from partners like Gilead Sciences. In 2023, Gilead provided a $100 million upfront payment under a 12-year collaboration agreement.

Go-to-market motion1 record

Distribution channels1 record

Marketing channels5 records

Core offering

Assembly Biosciences develops and advances through clinical trials a portfolio of oral, small-molecule antiviral therapeutics targeting serious viral and liver diseases, including helicase-primase inhibitors for recurrent genital herpes, an NTCP entry inhibitor for chronic hepatitis D and cholestatic liver diseases, and a next-generation capsid assembly modulator for chronic hepatitis B. The company is clinical-stage, has no commercialized products, and relies on a long-term partnership with Gilead Sciences for late-stage development and commercialization of selected programs.

Product overview

Assembly Biosciences is a clinical-stage biopharmaceutical company developing novel antiviral therapeutics targeting serious viral and liver diseases. The company's clinical pipeline consists of four main candidates: ABI-5366 and ABI-1179 (HSV helicase-primase inhibitors for recurrent genital herpes with once-weekly oral dosing potential), ABI-6250 (NTCP inhibitor for chronic hepatitis D and cholestatic liver diseases), and ABI-4334 (capsid assembly modulator for chronic hepatitis B). The company operates through a strategic partnership with Gilead Sciences, which has optioned the HSV helicase-primase inhibitor programs. Research programs focus on discovering additional novel small molecules for serious viral and liver diseases.

Differentiator

Problem solved

Functional benefit

Products and services

• ABI-5366 ABI-5366 is an oral HSV helicase-primase inhibitor in clinical development for the treatment of recurrent genital herpes, targeting the helicase-primase complex conserved across HSV-1 and HSV-2 with once-weekly or longer oral dosing intervals.
• ABI-1179 ABI-1179 is an oral HSV helicase-primase inhibitor in clinical development for the treatment of recurrent genital herpes, targeting the same viral helicase-primase complex as ABI-5366 with weekly or longer oral dosing.
• ABI-6250 ABI-6250 is an oral, small-molecule NTCP (sodium taurocholate cotransporting polypeptide) inhibitor in development for chronic hepatitis D infection and cholestatic liver diseases, blocking viral entry via the NTCP receptor with a 4-day half-life supporting once-daily oral dosing.
• ABI-4334 ABI-4334 is an oral, small-molecule next-generation capsid assembly modulator in development for chronic hepatitis B virus (HBV) infection, optimized to potently disrupt both viral replication and replenishment of cccDNA, the viral reservoir driving HBV persistence.

Quantifiable outcome

• ABI-1179 demonstrated 98% reduction in HSV-2 shedding rate (exceeding company's 80-85% target) and greater than 99% reduction in high viral load shedding rate in Phase 1b study
• +4 more outcomes

Segments4 records

Ideal customer profiles4 records

Technology focussed Yes

API detail

Has API

No

API docs

API detail

Core technology

AI maturity

App detail

Feature3 records

Partnerships

Two partnerships are on record, tiered core.

• Gilead SciencescoreOEM/ Whitelabel/ Licensing Partner · 22 December 2025Gilead Sciences exercised its option to license Assembly Biosciences' herpes simplex virus helicase-primase inhibitor programs, including candidates ABI-1179 and ABI-5366, for recurrent genital herpes. The licensing agreement involves a $35 million payment with potential milestones up to $330 million. Gilead leads further development and commercialization.
• Gilead SciencescoreStrategic or Co-development Partner · 17 October 2023Gilead Sciences and Assembly Biosciences entered into a 12-year collaboration to develop antiviral therapeutics targeting serious viral diseases including herpesviruses, HBV, and HDV. Assembly Bio receives a $100 million upfront payment with potential for additional milestone payments. Gilead holds options for future programs. Gilead controls research, development and commercialization of programs it opts into, while Assembly Bio may elect to certain profit/cost share and co-promotion options in the US.

Scale indicators10 records

Recent moves6 records

Expansion highlights5 records

Emerging players

• Brii Biosciences: Brii Biosciences is a clinical-stage biopharmaceutical company developing therapies for infectious diseases with a focus on chronic HBV and HDV in the China and global markets. It is a relevant peer in Assembly Bio's HDV and HBV target indications.
• Cocrystal Pharma: Cocrystal Pharma is a clinical-stage biotechnology company developing novel antiviral therapeutics for influenza, coronaviruses, and norovirus using structure-based drug design. It is an emerging peer in the small-molecule antiviral therapeutic space where Assembly Bio operates.
• NanoViricides: NanoViricides is an emerging clinical-stage company developing nanoviricide antiviral therapeutics for HSV, influenza, and other viral diseases. It is a partial peer in the HSV antiviral space with a different mechanism than Assembly Bio's helicase-primase inhibitors.

Direct peers

• AiCuris Anti-infective Cures: AiCuris is a clinical-stage biopharmaceutical company developing novel antiviral therapeutics, including pritelivir for HSV in immunocompromised patients. It is a direct peer to Assembly Bio in the HSV antiviral space targeting unmet needs in herpesvirus treatment.
• Vir Biotechnology: Vir Biotechnology is a clinical-stage immunology company developing therapeutics for serious infectious diseases including chronic hepatitis B and hepatitis delta. It directly competes with Assembly Bio in the HBV/HDV antiviral space with overlapping mechanisms and target indications.
• Arbutus Biopharma: Arbutus Biopharma is a clinical-stage biopharmaceutical company focused on developing a functional cure for chronic hepatitis B, including capsid assembly modulators and RNAi therapies. It directly competes with Assembly Bio's ABI-4334 HBV capsid assembly modulator program.
• Aligos Therapeutics: Aligos Therapeutics is a clinical-stage biopharmaceutical company developing therapeutics for chronic hepatitis B and NASH, including capsid assembly modulators and other antiviral mechanisms. It is a direct peer to Assembly Bio in the HBV space with overlapping mechanism classes.

Broad incumbents

• Roche: Roche is a global pharmaceutical incumbent with a major virology franchise including chronic hepatitis B products. It competes broadly in Assembly Bio's HBV target indication and represents the dominant standard-of-care provider in the space.
• Gilead Sciences: Gilead Sciences is a large biopharmaceutical company with a dominant antiviral franchise including HBV/HDV products. As Assembly Bio's strategic partner and 29.9% owner, Gilead is both a key collaborator and the most significant commercial incumbent in Assembly Bio's target indications.
• GlaxoSmithKline: GlaxoSmithKline is a global pharmaceutical incumbent with antiviral products including treatments for herpesviruses. It represents the broad incumbent competitor in Assembly Bio's HSV recurrent genital herpes target market.

Market position

Strengths4 records

Weaknesses4 records

Competitive moat4 records

Key risks5 records

Key highlights6 records

Customer concentration

• LinkedInlinkedin.com/company/assembly-bio
• Xx.com/assemblybio

Revenue estimate

Valuation estimate

Number of profiles

Profiles14 records

Funding overview

Funding rounds7 records

Investors12 records

Funding detail is available on the Subscription and Enterprise plan.Contact sales →

M&A

Investments

M&A and investment is available on the Subscription and Enterprise plan.Contact sales →

Frequently asked questions about Assembly Biosciences