Pharmacokinetics of injectable favipiravir: phase I, randomized, double-blind, placebo-controlled study in healthy East Asian subjects
- 1Department of Clinical Infectious Diseases, Asahi University Hospital, Gifu, Japan
- 2Department of Clinical Infectious Diseases, Aichi Medical University, Nagakute, Aichi, Japan
- 3Development Division, FUJIFILM Toyama Chemical Co., Ltd, Chuo City, Tokyo, Japan
Abstract
Favipiravir, an oral antiviral medication, has been approved in Japan for the treatment of patients with novel or re-emerging influenza and severe fever with thrombocytopenia syndrome (SFTS). Randomized, double-blind, placebo-controlled trials were conducted in an East Asian population to characterize the pharmacokinetics and tolerability of an injectable favipiravir formulation. In the single-ascending dose trial, subjects received a single intravenous (IV) dose of 300–2,400 mg of favipiravir. In the multiple dose trial, 1,800 mg was administered twice daily on the first day, followed by 800 mg twice daily for the subsequent 10 days, which is the approved tablet dose for SFTS in Japan. This multiple-dose trial was divided into a cohort receiving intravenous administration throughout the treatment period (IV cohort) and a cohort switching to oral administration from Day 6 (Switching cohort). After a single administration of ≤2,400 mg, the pharmacokinetic parameters increased in a dose-dependent manner but showed slight deviation from linearity. The geometric mean maximum plasma concentration following a single 2,400 mg dose was 126 (range: 110 to 138) μg/mL. In the IV cohort, the trough (at 12 h post-dose) plasma concentrations were maintained at approximately 85 μg/mL after Day 2. These concentrations were approximately 20% higher than those achieved with the same oral doses. In the Switching cohort, these concentrations were maintained throughout the treatment. No serious adverse events were observed. These findings support advancing injectable favipiravir into clinical evaluation.
CLINICAL TRIALS: This study is registered with the Japan Registry of Clinical Trials as jRCT2071210042 and jRCT2071210126.
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BibTeX
@article{mikamo2026pharmacokinetics,
title = {{Pharmacokinetics of injectable favipiravir: phase I, randomized, double-blind, placebo-controlled study in healthy East Asian subjects}},
author = {Hiroshige Mikamo and Masahiro Nakabayashi and Tsutomu Sakurai},
journal = {Antimicrobial Agents and Chemotherapy},
year = {2026},
month = jul,
doi = {10.1128/aac.00463-26},
url = {https://doi.org/10.1128/aac.00463-26},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Pharmacokinetics of injectable favipiravir: phase I, randomized, double-blind, placebo-controlled study in healthy East Asian subjects
AU - Hiroshige Mikamo
AU - Masahiro Nakabayashi
AU - Tsutomu Sakurai
PY - 2026
DA - 2026/07/21
JO - Antimicrobial Agents and Chemotherapy
DO - 10.1128/aac.00463-26
UR - https://doi.org/10.1128/aac.00463-26
AB - Favipiravir, an oral antiviral medication, has been approved in Japan for the treatment of patients with novel or re-emerging influenza and severe fever with thrombocytopenia syndrome (SFTS). Randomized, double-blind, placebo-controlled trials were conducted in an East Asian population to characterize the pharmacokinetics and tolerability of an injectable favipiravir formulation. In the single-ascending dose trial, subjects received a single intravenous (IV) dose of 300–2,400 mg of favipiravir. In the multiple dose trial, 1,800 mg was administered twice daily on the first day, followed by 800 mg twice daily for the subsequent 10 days, which is the approved tablet dose for SFTS in Japan. This multiple-dose trial was divided into a cohort receiving intravenous administration throughout the treatment period (IV cohort) and a cohort switching to oral administration from Day 6 (Switching cohort). After a single administration of ≤2,400 mg, the pharmacokinetic parameters increased in a dose-dependent manner but showed slight deviation from linearity. The geometric mean maximum plasma concentration following a single 2,400 mg dose was 126 (range: 110 to 138) μg/mL. In the IV cohort, the trough (at 12 h post-dose) plasma concentrations were maintained at approximately 85 μg/mL after Day 2. These concentrations were approximately 20% higher than those achieved with the same oral doses. In the Switching cohort, these concentrations were maintained throughout the treatment. No serious adverse events were observed. These findings support advancing injectable favipiravir into clinical evaluation. CLINICAL TRIALS: This study is registered with the Japan Registry of Clinical Trials as jRCT2071210042 and jRCT2071210126.
SN - 0066-4804
SN - 1098-6596
ER -