'Encouraging': Antiviral ziresovir shows promise against RSV in infants
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Key takeaways:
- Infants who received ziresovir had greater reductions in bronchiolitis scores and viral load compared with placebo.
- The most common adverse events were diarrhea, elevated liver-enzyme level and thrombocytosis.
The investigational antiviral ziresovir showed promise for the treatment of respiratory syncytial virus infection in infants during a phase 3 trial in China, researchers reported in The New England Journal of Medicine.
“Ziresovir is a potent, selective orally administered RSV F protein inhibitor,” Shunying Zhao, MD, PhD, from the department of respiratory medicine at Beijing Children’s Hospital, the National Center for Children’s Health and National Clinical Research Center for Respiratory Diseases, and colleagues wrote. “A recent phase 2 trial involving 72 participants 1 to 24 months of age showed that treatment with ziresovir was associated with greater reductions in the RSV viral load and in scores representing signs and symptoms than placebo, with no evident safety concerns.”
In an editorial published about the results of the phase 3 trial, Edward E. Walsh, MD, a professor of medicine at the University of Rochester, wrote that although a maternal vaccine and monoclonal antibody are now available to prevent RSV hospitalization among infants, “the need remains for an effective antiviral agent to treat infants and older children who are ineligible for or do not benefit from these new interventions.”
The double-blind randomized placebo-controlled trial included 302 infants aged 1 to 24 months (74% boys) who had been hospitalized for RSV between Sept. 22, 2020, and Jan. 19, 2022. The researchers randomly assigned participants in a roughly 2:1 ratio to receive ziresovir (n = 200) or placebo (102).
Infants in the ziresovir group received 10 mg to 40 mg of the antiviral medication every 12 hours for 5 days. The researchers followed up 9 days after treatment for safety data.
The researchers evaluated efficacy from baseline to day 3 using the Wang bronchiolitis clinical score, which ranges from 0 to 12, with 12 indicating the most severe symptoms. They also tested infants’ viral load from baseline to day 5.
At baseline, participants’ mean Wang bronchiolitis score was 6.7±1.6 points, and their average viral load was 7.4±1.1 log10 copies/mL.
By day 3, the infants’ bronchiolitis scores decreased by 3.4 points (95% CI, –3.7 to –3.1) in the ziresovir group — a 30% greater reduction than in the placebo group (–2.7; 95% CI, –3.1 to –2.2; P = .002).
Infants in the ziresovir group also experienced a greater reduction in viral load after 5 days, compared with placebo (–2.5±0.2 log10 copies/mL vs. –1.9±0.2 log10 copies/mL, respectively).
More than half of participants in the ziresovir (61%) and placebo (53%) groups experienced adverse events during the treatment period, but the researchers found that 16% and 13% were related to ziresovir or placebo, respectively. The most common adverse events related to treatment were diarrhea, elevated liver-enzyme level and thrombocytosis.
“Overall, the results are encouraging, and further studies of ziresovir in more diverse settings and populations are warranted,” Walsh wrote. “Ziresovir offers the potential to augment the recently approved maternal vaccination and monoclonal antibody approaches for reducing the burden of RSV infection.”
References:
- Walsh, EE. New Eng J Med. 2024;doi:10.1056/NEJMe2410371.
- Zhao S, et al. New Eng J Med. 2024;doi:10.1056/NEJMoa2313551.
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