Assembly Biosciences reported that its two long‑acting helicase‑primase inhibitors, ABI‑1179 and ABI‑5366, achieved impressive interim Phase 1b efficacy in participants with recurrent genital herpes. A 50 mg weekly dose of ABI‑1179 produced a 98 % reduction in HSV‑2 shedding, a >99 % reduction in high‑viral‑load shedding, and a 91 % reduction in virologically confirmed genital lesions over a 29‑day evaluation period. For ABI‑5366, the monthly dosing cohort showed a 76 % reduction in HSV‑2 shedding, an 88 % reduction in virologically confirmed lesions, and an 81 % reduction in high‑viral‑load shedding—data that represent the first published results for the monthly regimen and confirm the drug’s strong antiviral activity across multiple dosing schedules.
The results reinforce Assembly’s differentiated platform and support the company’s strategy to advance both weekly and monthly candidates into Phase 2 studies. They also strengthen the partnership with Gilead Sciences, which holds opt‑in rights to the helicase‑primase program and contributed ABI‑1179 to Assembly. The data suggest that the company’s long‑acting antivirals could offer a convenient dosing schedule and superior efficacy compared with the current nucleoside analogs, addressing an unmet need in a $5.42 billion market that is projected to grow to $7.28 billion by 2029. No new drugs have been approved for genital herpes in over 25 years, so these findings could position Assembly as a potential market leader if later‑stage trials confirm the Phase 1b results.
Chief Medical Officer Anuj Gaggar said, “We are thrilled with these Phase 1b findings for both highly promising candidates.” The comment signals confidence in the clinical program and underscores the company’s belief that the data exceed its internal targets and could accelerate the development timeline.
Analysts reacted positively to the data. Mizuho raised its price target on Assembly to $40 from $29, and Guggenheim reiterated its support for the company’s pipeline. The market reaction was driven by the strong efficacy data that exceeded expectations, the potential for convenient weekly and monthly dosing, and the reinforced partnership with Gilead, which could provide additional funding or commercialization support if the clinical trajectory remains favorable.
The interim Phase 1b results de‑risk Assembly’s pipeline and position the company for Phase 2 studies, but the candidates remain early‑stage. Continued success in later‑stage trials will be essential to confirm the clinical benefit and to translate the promising efficacy into a commercially viable product.
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