Phase 3, multicentre, double-blind, randomised, parallel-group, placebo-controlled study of camostat mesilate (FOY-305) for the treatment of COVID-19 (CANDLE study)
Authors: Kinoshita Taku , Shinoda Masahiro , Nishizaki Yasuhiro , Shiraki Katsuya , Hirai Yuji , Kichikawa Yoshiko , Tsushima Kenji , Sinkai Masaharu , Komura Naoyuki , Yoshida Kazuo , Kido Yasutoshi , Kakeya Hiroshi , Uemura Naoto , Kadota Junichi 
Published: April 2022

Background

In vitro drug-screening studies have indicated that camostat mesilate (FOY-305) may prevent SARS-CoV-2 infection into human airway epithelial cells. This study was conducted to investigate whether camostat mesilate is an effective treatment for SARS-CoV-2 infection (COVID-19).

Methods

This was a phase 3, multicentre, double-blind, randomised, parallel-group, placebo-controlled study. Patients were enrolled if they were admitted to a hospital within 5 days of onset of COVID-19 symptoms or within 5 days of a positive test for asymptomatic patients. Severe cases (e.g., those requiring oxygenation/ventilation) were excluded. Patients were administered camostat mesilate (600 mg qid; four to eight times higher than the clinical doses in Japan) or placebo for up to 14 days. The primary efficacy endpoint was the time to the first two consecutive negative tests for SARS-CoV-2.

Findings

One-hundred and fifty-five patients were randomised to receive camostat mesilate (n=78) or placebo (n=77). The median time to the first test was 11 days in both groups, and conversion to negative status was observed in 60·8% and 63·5% of patients in the camostat mesilate and placebo groups, respectively. The primary (Bayesian) and secondary (frequentist) analyses found no significant differences in the primary endpoint between the two groups. No additional safety concerns beyond those already known for camostat mesilate were identified.

Interpretation

Camostat mesilate is no more effective, based on upper airway viral clearance, than placebo for treating patients with mild to moderate SARS-CoV-2 infection with or without symptoms.

Funding

Ono Pharmaceutical Co., Ltd.

RESEARCH IN CONTEXT PANEL

Evidence before this study

SARS-CoV-2 infection (COVID-19), as a significant global health threat, is characterised by broad symptoms and varying disease severity. At the time of planning this study, there were no specific treatments for COVID-19 beyond the use of antiviral drugs, steroids and, in severe cases, ventilation with oxygen. Pre-clinical screening studies revealed the spike (S) protein of SARS-CoV-2 bind to angiotensin converting enzyme II (ACE2) on the host cell membrane. The S protein is then cleaved by a type II transmembrane serine protease (TMPRSS2) as an essential enzyme for the viral entry into host cells. In vitro drug-screening studies have shown that drugs that block binding of the S protein to ACE2 can prevent viral entry into a cell line derived from human airway epithelium. The studies identified 4-(4-guanidinobenzoyloxy)phenylacetic acid, the active metabolite of a serine protease inhibitor (camostat mesilate, FOY-305), as a candidate inhibitor of SARS-CoV-2 entry into humans. A retrospective study of critically ill COVID-19 patients with organ failure revealed a decline in disease activity within 8 days of admission among patients treated with camostat mesilate. In consideration of the preclinical and early clinical evidence, it was hypothesised that camostat mesilate is an effective treatment for patients with COVID-19. Therefore, we planned and executed a phase 3, randomised, double-blind, placebo-controlled study to investigate the efficacy and safety of camostat mesilate for the treatment of patients with mild to moderate COVID-19 infection with or without symptoms. The primary endpoint was the time to the first two consecutive negative tests for SARS-CoV-2. No controlled clinical studies of camostat mesilate had been conducted at the time of planning this study.

Added value of this study

The results of this randomised controlled trial revealed that camostat mesilate, administered at a dose of 600 mg qid for up to 14 days, was no more effective than placebo, based on upper airway viral clearance in patients with mild to moderate SARS-CoV-2 infection with or without symptoms. Furthermore, there were no differences between the study groups in terms of other efficacy endpoints. This study used a dose that was four to eight times higher than the clinical doses of camostat mesilate used in Japan for the acute symptoms of chronic pancreatitis and postoperative reflux oesophagitis. The study identified no additional safety concerns beyond those already known for camostat mesilate.

Implications of all available evidence

After starting this study, another randomised, placebo-controlled study reported the efficacy and safety of camostat mesilate for the treatment of patients with COVID-19, albeit at a lower dose of 200 mg three times daily. That study also found no difference between camostat mesilate and placebo for the primary endpoint (the time to discharge or a clinical improvement in clinical severity of at least two points on a seven-point ordinal scale). Along with this evidence, our study did not support the use of camostat mesilate as a treatment option for COVID-19. However, since the administration of camostat mesilate was started after the onset of symptoms and presumably the peak viral load, we cannot exclude the possibility that camostat mesilate may be effective if administration is started earlier in the course of infection, or perhaps as prophylactic use in close contacts.