New Antiviral ensitrelvir Shows Promise in COVID-19 Trials, Offers potential Advantages Over Existing Treatments
Vientiane, Laos – Trial data released today demonstrate that the antiviral drug ensitrelvir exhibits potent activity against COVID-19, accelerating viral clearance adn symptom resolution in patients. A study conducted at Mahosot Hospital in Laos, involving 604 patients, compared ensitrelvir to ritonavir-boosted nirmatrelvir (a key component of Paxlovid) and a no-treatment control group.
The research, detailed in recent reports, showed both ensitrelvir and nirmatrelvir significantly sped up viral clearance. By day 3,median viral densities where 2.9-fold lower in the ensitrelvir group and 2.4-fold lower in the nirmatrelvir group compared to those receiving no study drug. Viral clearance rates were 82% faster with ensitrelvir and 116% faster with nirmatrelvir by day 5, relative to the control group. While ensitrelvir demonstrated non-inferiority to nirmatrelvir, viral clearance was 16% slower with ensitrelvir in comparison.
Symptom resolution also improved with both antivirals, with the ensitrelvir group experiencing a 32% faster recovery and the nirmatrelvir group a 38% faster recovery compared to the control group. Viral rebound occurred in 15 (7%) of 207 patients taking nirmatrelvir and 10 (5%) of 202 patients taking ensitrelvir. Importantly, no patients in any group developed severe disease.
A meta-analysis encompassing data from 1,157 patients in Thailand and Laos, comparing ensitrelvir and nirmatrelvir to other tested antivirals (remdesivir, molnupiravir, favipiravir, and ivermectin), revealed that ensitrelvir and nirmatrelvir demonstrated the largest antiviral effects.
Researchers highlight potential advantages of ensitrelvir over ritonavir-boosted nirmatrelvir, including a lower pill burden (one pill daily versus two) and the absence of the unpleasant taste reported with Paxlovid. Moreover, ensitrelvir could serve as an alternative for immunocompromised patients or those taking medications with potential interactions with ritonavir.
“This first comparative in-vivo pharmacodynamic assessment of ensitrelvir and ritonavir-boosted nirmatrelvir confirms that ensitrelvir has potent antiviral activity in treating COVID-19,” the study authors stated.
While the immediate threat of COVID-19 has diminished for many, the researchers emphasize the continued risk for vulnerable populations. “Meanwhile COVID-19 can still be a risky illness in frail, older, or immunocompromised patients,” they wrote. “these are the patients who may still benefit from effective therapeutics.”
Shionogi, the drug’s manufacturer, submitted a New Drug Request (NDA) to the FDA in September seeking approval of ensitrelvir not only for treatment but also for prevention of COVID-19, based on a phase 3 trial showing a 67% reduced risk of infection after exposure. A decision on broader approval remains pending.
