A Study of Micro Dose Ambrisentan in Hospitalized Patients With Respiratory Insufficiency Due to COVID-19

Patients with COVID-19 frequently develop lower respiratory complications. Difficulty breathing and a low concentration of oxygen in the blood are of concern in patients with COVID-19, as they indicate that the lungs may be significantly affected. In some patients, respiratory symptoms may progress to the point where oxygen support is needed (i.e. use of an oxygen prongs, mask or ventilator).

The exact mechanism of why patients with COVID-19 develop low concentrations of oxygen in blood is not fully understood. Some data suggest that the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the virus causing Coronavirus Disease 2019 (COVID-19), can affect the body's blood vessels directly and extensively. In the lung, blood vessels participate in the absorption of oxygen.

Endothelin is a potent hormone produced by human blood vessels. When increased, endothelin can result in the narrowing of blood vessels in the lung and decrease the volume of blood flowing through the lungs. This decrease in in blood flow through the lungs may be one of many factors affecting normal lung function. Ambrisentan can block the effects of endothelin in the body, and this could theoretically improve blood flow through the lungs.

This study will evaluate whether ambrisentan, by blocking the effects of the hormone endothelin in the lungs, improves the breathing capacity of patients with COVID-19, increases the concentration of oxygen in the blood and prevents the progression to respiratory failure and death. Ambrisentan is a drug that is currently used to treat patients with pulmonary hypertension, a disease where blood flow through the lungs is decreased.

Subjects participating in this study are those patients hospitalised with severe respiratory symptoms related to COVID-19, and are considered to be at high-risk of developing respiratory complications. Ambrisentan will be administered in the hospital, and will be continued at home for up to 28 days. In this study, ambrisentan will be administered at much lower doses that those used in patients with pulmonary hypertension.

This is a randomized, double-blind, placebo-controlled, multi-centre trial to evaluate the safety and efficacy of ambrisentan for the treatment of severe COVID-19. The population consists of hospitalized subjects who have a confirmed SARS-CoV-2 (a coronavirus (CoV) ) infection, are at high-risk of progression to respiratory failure or death and have low oxygen saturation and/or require oxygen supplementation at the time of admission. Pregnant or lactating women will not be allowed to participate in this study given the teratogenic potential of ambrisentan. Subjects requiring mechanical ventilation or intubation at the time of enrolment are considered to have respiratory failure and will not be allowed into the study, as one primary objective of the study is to evaluate the effect of ambrisentan in preventing respiratory failure.

Enrolled subjects will be randomly assigned to the treatment arm or control arm at a 1:1 ratio. In the treatment arm, subjects will receive ambrisentan on top of the standard-of-care. In the control arm, subjects will receive the administration vehicle only (i.e., placebo) and on top of the standard of care. The study medication (ambrisentan or placebo) will be administered for up to 28 days. In the event that the subject is discharged between Day 4 and Day 28, the subject will continue the study treatment at home until completion of the 28-day study medication regimen. Investigators, the Sponsor and the subject will be blinded to the treatment assignment. A Drug Safety Monitoring Board will be monitoring the safety of the study.

Eligibility Criteria:
Inclusion Criteria:

* Subject (or legally authorized representative) provides informed consent (written or oral) prior to initiation of any study procedures.
* Male or non-pregnant, non-lactating female. Women of child-bearing potential must have a confirmed negative serum pregnancy test at the time of screening and must use a highly effective contraceptive method throughout the study (such as implants, injectables, hormonal contraceptives and condom, double barrier contraception \[i.e., condom + diaphragm/spermicidal gel or foam\]) and until one month after completing treatment with the study medication. In the case of hormonal contraception, women should have been on a stable regimen for a minimum of three months before study enrolment. Women not of child-bearing potential include post-menopausal females (defined as having a history of amenorrhea for at least one year) or a documented status as being surgically sterile (hysterectomy, bilateral oophorectomy, tubal ligation/salpingectomy). Men must use an effective contraception method (i.e., condom + diaphragm/spermicidal gel or foam, or vasectomy), and should not donate semen during the study. Men are considered to be fertile from the time of puberty, except for those men with permanent sterility secondary to bilateral orchiectomy.
* At least 18 years of age and not older than 85 years of age at time of enrolment
* Confirmed SARS-CoV-2 infection defined as: Positive Real-Time Polymerase Chain Reaction (RT-PCR) result in sample collected in the 10 days prior to randomisation, OR positive antigenic test result in sample collected in the 10 days prior to randomisation.
* Radiological confirmation of pneumonia.
* Subject receiving low-flow oxzgen supplementation of at least 2 L/min and not more than 15 L/min.
* Subject (or legally authorized representative) understands and agrees to comply with planned study procedures.
* Subject (or legally authorized representative) agrees to not participate in any other clinical trial, including clinical trials for the treatment or prevention of COVID-19 or SARS-CoV-2 through Day 30.

Exclusion Criteria:

* Subject at a high risk of death, according to investigator's opinion, in the 3 months following enrollment from other causes than Acute Respiratory Distress Syndrome (e.g., severe neurological damage or cancer patients in terminal stages of the disease).
* Subject currently being treated with an endothelin receptor antagonist.
* Subject currently being treated with another pulmonary vasodilator.
* Anticipated need for high-flow oxygen supplementation, non-invasive mechanical ventilation, endotracheal intubation or tracheostomy at the time of screening.
* History of mechanical ventilation (invasive or non-invasive) in the last 7 days.
* Documented history of end-stage liver disease, cirrhosis or idiopathic pulmonary fibrosis (IPF) with or without pulmonary arterial hypertension.
* Aspartate Aminotransferase (AST) or Alanine Aminotransferase (ALT) \> 3-times the upper limit of normal (ULN).
* Anticipated discharge from the hospital or transfer to another hospital which is not a study site within 96 hours.
* Participation in another interventional clinical trial in the 15 days prior to enrollment.
* Known hypersensitivity to ambrisentan or propylene glycol.