Highlights
- ALG-000184, a Class-E capsid assembly modulator (CAM-E), achieved a 3–4 log10 IU/mL reduction in serum HBV DNA and up to a 3.0 log10 copies/mL reduction in HBV RNA over 28 days.
- The drug demonstrated a linear, dose-dependent pharmacokinetic profile and was well tolerated across all tested doses (10 mg to 300 mg).
- In HBeAg-negative participants, 83% reached HBV DNA levels below the lower limit of quantification (LLOQ), and 100% reached HBV RNA below LLOQ.
- Preliminary evidence of HBsAg reduction in HBeAg-positive participants suggests potential for ALG-000184 as a component of finite curative regimens.
Background
Chronic hepatitis B virus (HBV) infection remains a global health crisis, affecting over 250 million people and leading to significant morbidity and mortality from cirrhosis and hepatocellular carcinoma. While current standard-of-care nucleos(t)ide analogues (NAs) effectively suppress HBV DNA replication, they rarely achieve a functional cure—defined as sustained HBsAg loss with or without anti-HBs seroconversion. This limitation stems from the persistence of covalently closed circular DNA (cccDNA) in the nuclei of infected hepatocytes and the continuous production of viral antigens.
Capsid assembly modulators (CAMs) represent a promising new class of direct-acting antivirals designed to disrupt the viral lifecycle at multiple stages. CAMs are categorized into two primary classes based on their structural impact: Class-A (accelerant/aberrant) which lead to the formation of large, non-capsid polymers, and Class-E (empty), which induce the assembly of normal-sized but genome-deficient (empty) capsids. ALG-000184 (pevifoscorvir sodium) is an oral prodrug of ALG-001075, a potent Class-E CAM. By preventing the encapsidation of pregenomic RNA (pgRNA) and potentially interfering with the de novo establishment of the cccDNA pool, ALG-000184 aims to provide deeper viral suppression than NAs alone.
Key Content
Study Design and Patient Demographics
The ALG-000184-201 study was a Phase 1, multicenter, randomized, double-blind, dose-escalation trial. Part 3 of this trial focused specifically on participants with chronic HBV infection who were either treatment-naive or not currently receiving treatment. A total of 59 participants were randomized (4:1) to receive either daily oral doses of ALG-000184 (10 mg, 50 mg, 100 mg, or 300 mg) or a placebo for 28 days.
The cohort was diverse, with a median age of 37 years and 68% Asian representation. Importantly, the study included both HBeAg-negative (n=23 receiving active drug) and HBeAg-positive participants, allowing for an assessment of efficacy across different viral load baselines and disease states. Baseline HBV DNA levels were significantly higher in the HBeAg-positive groups, providing a rigorous test for the drug’s potency.
Pharmacokinetics: Dose Linearity and Predictability
Pharmacokinetic (PK) analysis revealed that ALG-000184 has a dose-dependent linear profile. This predictability is crucial for clinical development, as it allows for precise dose adjustments in subsequent Phase 2 and 3 trials. The prodrug was rapidly converted to its active moiety, ALG-001075, maintaining therapeutic concentrations sufficient to inhibit viral replication throughout the 24-hour dosing interval.
Antiviral Efficacy: Viral DNA and RNA Dynamics
The antiviral response was rapid and profound across all dose levels. Within 28 days, ALG-000184 monotherapy resulted in:
- HBV DNA: Reductions of approximately 3–4 log10 IU/mL. In HBeAg-negative participants, where baseline levels were lower, 83% achieved levels below the LLOQ (10 IU/mL).
- HBV RNA: Reductions of 0.5–3.0 log10 copies/mL. Notably, 100% of HBeAg-negative participants achieved HBV RNA levels below LLOQ (10 copies/mL).
While HBeAg-positive participants did not reach LLOQ within the short 28-day window due to higher initial viral loads, their rate of decline mirrored that of the HBeAg-negative group, suggesting that longer treatment durations would likely result in similar rates of total suppression.
Impact on HBsAg and Viral Antigens
A hallmark challenge for CAMs has been the reduction of HBsAg, which is often produced from integrated HBV DNA in HBeAg-negative patients. However, in this study, several HBeAg-positive participants receiving the 100 mg and 300 mg doses showed modest HBsAg declines ranging from 0.2 to 0.8 log10 IU/mL. While these reductions are preliminary, they provide a signal that Class-E CAMs might influence antigen production or release more effectively than previously anticipated, particularly in HBeAg-positive states where cccDNA-derived transcription is dominant.
Safety and Tolerability Profile
The primary objective of this Phase 1 trial was safety. ALG-000184 demonstrated a manageable safety profile with no deaths or drug-related serious adverse events (SAEs). Two SAEs occurred (mild spinal pain and spontaneous pneumothorax) but were deemed unrelated to the study drug.
The most common treatment-emergent adverse events (TEAEs) included elevations in alanine aminotransferase (ALT) and aspartate aminotransferase (AST). ALT elevations occurred in 31% of the ALG-000184 group compared to 18% in the placebo group. In the context of HBV therapy, ALT elevations (flares) can be difficult to interpret; they may represent drug-induced liver injury or, conversely, a beneficial immune-mediated clearance of infected hepatocytes triggered by the rapid decline in viral replication. The transient nature of these elevations and the lack of concurrent bilirubin increases suggest they were generally well-tolerated.
Expert Commentary
The results of the ALG-000184-201 trial are highly encouraging for the HBV research community. The potency of Class-E CAMs in reducing both HBV DNA and HBV RNA confirms their role as superior inhibitors of viral replication compared to NAs. By stopping the formation of pgRNA-containing capsids, ALG-000184 effectively halts the cycle of intracellular cccDNA replenishment, which is a critical step toward achieving a finite treatment duration.
A point of controversy in the field remains whether CAMs should be used as monotherapy or in combination with other agents. While ALG-000184 showed remarkable efficacy as monotherapy, the long-term goal for a functional cure will likely necessitate a “triple-threat” approach: viral suppression (via NAs or CAMs), antigen reduction (via siRNA or antisense oligonucleotides), and immune stimulation (via interferon or therapeutic vaccines). The HBsAg declines observed in the 300 mg cohort suggest that ALG-000184 could play a pivotal role in such combinations.
One limitation of this study is its short duration (28 days). The long-term safety of CAMs, particularly regarding the risk of late ALT flares or potential off-target effects of empty capsid accumulation, remains to be seen. Furthermore, the higher incidence of hyperuricemia and amylase elevation, although mostly low-grade, warrants close monitoring in Phase 2 studies.
Conclusion
ALG-000184 (pevifoscorvir sodium) has emerged as a highly potent and well-tolerated Class-E capsid assembly modulator. In this Phase 1 trial, it demonstrated the ability to rapidly suppress HBV DNA and RNA across different patient subtypes. These findings strongly support the continued development of the 300 mg dose in larger, longer-term Phase 2 studies. Whether used as a cornerstone for chronic suppressive therapy or as part of an ambitious curative cocktail, ALG-000184 represents a significant step forward in the quest to eliminate chronic hepatitis B.
References
- Yuen MF, Agarwal K, Jucov A, et al. ALG-000184 (pevifoscorvir sodium) monotherapy in participants with chronic HBV infection: a phase 1, multicentre, randomised, dose escalation trial. Lancet Gastroenterol Hepatol. 2026;11(3):218-231. PMID: 41554267.
- Zoulim F, Durantel D. Antiviral therapies: Hepatitis B virus. Cold Spring Harb Perspect Med. 2015;5(6):a021485. PMID: 25934461.
- Chow N, et al. Mechanism of Action of Capsid Assembly Modulators. J Hepatol. 2023;78(2):401-415.
