Assembly Biosciences, Inc.

What they do

Assembly Bio develops therapeutics for viral and liver diseases, with a pipeline led by two long-acting helicase-primase inhibitors (HPIs), 5366 and 1179, for recurrent genital herpes, now exclusively licensed to Gilead. Internal programs include ABI-6250, an oral NTCP inhibitor for chronic HDV and for cholestatic liver diseases PBC and PSC, and ABI-4334, a capsid assembly modulator for HBV, for which the company is seeking a partner. ABI-7272, an oral broad-spectrum non-nucleoside polymerase inhibitor for transplant-associated herpesviruses, is in regulatory filing-enabling studies.

Revenue drivers

• Gilead collaboration — Gilead exercised its December 2025 option to license the HPI program (1179 and 5366) and controls development; Assembly Bio's revenue reflects collaboration payments, with a first $75 million extension payment due in Q4 2026.
• ABI-6250 (HDV) — Internal NTCP inhibitor for chronic hepatitis delta virus; a Phase 2 study is planned to initiate by year-end 2026. No product revenue to date.
• ABI-6250 (cholestatic liver diseases) — Expanded indication set covering PBC and PSC, with Phase 2 initiation expected in Q1 2027; adds a second development path for the same asset.
• ABI-7272 / ABI-4334 — Pre-revenue programs: 7272 in filing-enabling studies for transplant-associated herpesviruses, and 4334 in a partner-search process that the company will not advance without a partner.

Recent performance

Second quarter 2026 revenue was $13.4 million, following $8.2 million in Q1 2026 and $42.5 million in Q4 2025. Full-year 2025 revenue was $72.3 million against a net loss of $6.1 million, versus $28.5 million of revenue and a $40.2 million net loss in 2024. Operating cash flow was negative $41.1 million for 2025. At June 30, 2026, cash, cash equivalents and marketable securities were $320.4 million, up from $226.6 million at March 31, 2026, after a $115 million gross financing. Total assets were $330.8 million and shareholder equity $305.6 million at June 30, 2026.

Strategy

The company is transitioning its HPI program to Gilead, which has selected GS-1179 to advance into Phase 2 by end-2026 and does not intend to develop 5366 further. Assembly Bio must decide by year-end 2026 whether to opt in to a 40% U.S. cost-and-profit share instead of U.S. milestones and royalties, pending Gilead's commercial cost estimates. Internally, it is preparing Phase 2 studies of ABI-6250 in HDV (Q4 2026) and cholestatic liver diseases (Q1 2027) and continuing regulatory filing-enabling studies for ABI-7272. ABI-4334 is being marketed for partnering and will not advance without a partner.

Risks

• Dependence on Gilead — Gilead controls development of the HPI program and has sole rights to further clinical development and commercialization, so Assembly Bio's herpes economics depend on Gilead's decisions, including its choice not to advance 5366.
• Profit-share opt-in decision — The company must decide by year-end 2026 whether to accept a 40% U.S. cost-and-profit share in lieu of milestones and royalties, a capital commitment based on cost estimates not yet received.
• Early-stage pipeline — ABI-6250, ABI-7272 and ABI-4334 remain investigational and unapproved, with no product revenue; the company has recorded annual net losses including $6.1 million in 2025 and $40.2 million in 2024.
• Partnering risk for ABI-4334 — The HBV capsid assembly modulator will not be advanced without a partner, so its progress depends on the partner-search process initiated in Q1 2026.

Outlook

Management expects to determine by year-end 2026 whether to opt in to the 40% U.S. cost-profit share for the HSV HPI program after receiving Gilead's commercial cost estimates. It plans to initiate a Phase 2 study of ABI-6250 in chronic HDV by year-end 2026 and in cholestatic liver diseases in Q1 2027. The company states its cash position, including the first $75 million Gilead extension fee due in Q4 2026, projects a runway into 2029 covering the planned ABI-6250 Phase 2 studies.