Study of LAU-7b for the Treatment of Long COVID in Adults (ESSOR)

A DOUBLE-BLIND, RANDOMIZED, PLACEBO-CONTROLLED, ADAPTIVE PHASE 2/3 STUDY OF THE EFFICACY OF LAU-7b IN THE TREATMENT OF ADULTS WITH LONG COVID AND MODERATE TO SEVERE SYMPTOMS

ESSOR is a double-blind, placebo-controlled study of the orally-administered antiviral and inflammation-controlling LAU-7b for the treatment of adults with Long COVID and moderate to severe symptoms.

Study Overview

• Status: Completed
• Conditions: Long COVID
• Intervention / Treatment: Drug: LAU-7b for 3 cycles; Drug: LAU-7b for 1 cycle, then placebo; Other: Placebo for 3 cycles

Detailed Description

ESSOR is a multicenter, randomized, double-blind, placebo-controlled Phase 2/3 study of LAU-7b for the treatment of Long COVID in non-hospitalized adults with moderate to severe Long COVID symptoms.

The goal of the study is to evaluate the efficacy of LAU-7b therapy + stable symptomatic standard-of-care relative to placebo + stable symptomatic standard-of-care at reducing the overall Long COVID burden by improving multiple dimensions of quality-of-life and alleviating the symptoms.

This study is a logical extension of investigating LAU-7b as a potential therapeutic against various phases of COVID-19.

LAU-7b is therefore being proposed as a potential disease-modifying medication for the treatment of Long COVID.

• Study Type: Interventional
• Enrollment (Actual): 272
• Phase: Phase 2; Phase 3

Contacts and Locations

Study Locations

• Canada
  • Quebec
    • Chicoutimi, Quebec, Canada, G7H 5H6
      • CIUSS du Saguenay-Lac-St-Jean - Hôpital Chicoutimi
    • Montreal, Quebec, Canada, H2W 1R7
      • Institut de recherches cliniques de Montreal
    • Montreal, Quebec, Canada, H3G 1A4
      • Montreal General Hospital
    • Québec, Quebec, Canada, G1V 4T3
      • Diex Recherche Quebec Inc.
    • Sherbrooke, Quebec, Canada, J1H 5N4
      • Centre Hospitalier de l'Université de Sherbrooke

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

1. Subjects must be 18 years and older, of either gender, and able to give informed consent;
2. Subjects diagnosed with Long COVID and exhibiting persisting, relapsing or new Long COVID symptom(s) at least 12 weeks beyond the start (test positivity or symptom onset) of the causative COVID-19 infection;
3. At least one of the Long COVID symptoms must be from the core list of Long COVID symptoms, and be present for a minimum of 2 weeks prior to screening and of moderate or severe intensity as per the 4-level Likert severity scale (0 to 3; 0 = no symptoms; 1 = mild symptoms; 2 = moderate symptoms; 3 = severe symptoms);
4. If female, must be either post-menopausal (one year or greater without menses), surgically sterile, or, for female subjects of child-bearing potential who are capable of conception, must be: practicing a highly effective method of birth control (acceptable methods include intrauterine device, complete abstinence, spermicide + barrier, male partner surgical sterilization, or hormonal contraception) during the study treatment intake and through 30 days after the last dose of the study medication. Periodical abstinence is not classified as an effective method of birth control. A pregnancy test for female subjects of child-bearing potential must be negative at the Screening Visit;
5. Subjects deemed capable of adequate compliance including attending scheduled follow-up calls/visits for the duration of the study, have internet access and able to read and answer questionnaires on electronic Patient Reported Outcomes platform (ePRO) or paper;
6. Screening laboratory test and vital signs results within ranges compatible with the subject's health condition, as per investigator's judgement. See also the last exclusion for certain liver function tests;
7. Subjects deemed capable of swallowing the study treatment capsules

Exclusion Criteria:

1. Subject is currently hospitalized (any reason);
2. Pregnancy or breastfeeding;
3. Any COVID vaccination within 4 weeks of screening or planned during study participation;
4. Presence of any health condition judged by the investigator to be directly causing one or more of the most common Long COVID symptoms;

5. Health condition deemed to possibly interfere with the study endpoints and/or the safety of the subjects. For example, the following conditions should be considered contraindicated for participation in the study. In case of doubt, the Investigator should consult with the Sponsor's medical representative:

   • Febrile neutropenia;
   • Fibromyalgia deemed to interfere with generalized pain measurements;
   • Presence of end-stage cancer (palliative care).
6. Presence or suspicion of drug or alcohol abuse, as judged by the Investigator;
7. Known history of a severe allergy or sensitivity to retinoids, or with known allergies to excipients in the oral capsule formulation proposed to be used in the study;
8. Participation in another interventional drug, alimentary supplement, psychological or device...etc. clinical trial within 30 days (or a minimum of 5 elimination half-lives for drugs) prior to screening, except ongoing participation in non-interventional studies;
9. Presence of total bilirubin >1.5 x Upper Limit of Normal (in the absence of demonstrated Gilbert's syndrome), alanine aminotransferase and/or aspartate aminotransferase > 2.5 x Upper Limit of Normal (unless there are clinical evidences of hepatic steatosis).

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Quadruple

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: LAU-7b for 3 cycles; Each study arm will consist of three (3) cycles of 14 days of treatment intake each spaced by a treatment holiday of 14 days.	Drug: LAU-7b for 3 cycles; Three cycles of 14 days of once-a-day intake of LAU-7b, each followed by a treatment intake pause of 14 days.; Other Names: fenretinide
Experimental: LAU-7b for 1 cycle, then placebo; Each study arm will consist of three (3) cycles of 14 days of treatment intake each spaced by a treatment holiday of 14 days.	Drug: LAU-7b for 1 cycle, then placebo; One cycle of 14 days of once-a-day intake of LAU-7b followed by two cycles of 14 days of placebo administered similarly, each followed by a treatment intake pause of 14 days.; Other Names: fenretinide
Placebo Comparator: Placebo for 3 cycles; Each study arm will consist of three (3) cycles of 14 days of treatment intake each spaced by a treatment holiday of 14 days.	Other: Placebo for 3 cycles; Three cycles of 14 days of once-a-day intake of placebo, each followed by a treatment intake pause of 14 days; Other Names: sugar pill

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change From Baseline in Physical Component Summary (PCS) of the Medical Outcomes Study Short-Form-36 (SF-36) at Week 12	The SF-36 questionnaire consists of 36 items grouped in eight health domains, vitality, physical functioning, bodily pain, general health perceptions, physical role functioning, emotional role functioning, social role functioning, and mental health, that can be aggregated to two summary scales, physical component summary (PCS ) and mental component summary (MCS). The PCS summarizes the physical status and constitutes the primary outcome variable. Each health domain score consists of the sum scores of the assigned questions. Scores are weighted and transformed into a scale ranging from 0 (greatest possible health restrictions, ie, severe disability) to 100 (no health restrictions). A higher score means a better physical status. The calculation process for the PCS has been previously described by Taft et al. 2001.	Week 0 and 12

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Safety of LAU-7b, Overview	Number of participants with adverse events. The safety was assessed through the monitoring of adverse events including laboratory test abnormalities, serious adverse events and adverse events leading to study treatment discontinuation. Treatment-emergent adverse event is defined as any adverse event with onset date on or after the first dose of study drug and on or before the Week 12 in person follow-up or until early termination or death, whichever occurred first.	From Week 0 to Week 12
Patient Global Impression of Change (PGI-C)	The PGI-C is a single item questionnaire that asks: "Overall, how would you rate the change in your ability to perform usual daily activities since you started the study?". These are the 7-point scale options: 1) "very much better", 2) "much better", 3) "minimally better", 4) "no change", 5) "minimally worse", 6) "much worse", or 7) "very much worse". Higher scores indicate a change for the worse and lower scores indicate a change for the better.	Weeks 4, 8 and 12
Proportion of Participants With Marked Improvement in PGI-C	Marked improvement includes "Very much improved" and Much improved". The PGI-C is a single item questionnaire that asks: "Overall, how would you rate the change in your ability to perform usual daily activities since you started the study?". These are the 7-point scale options: 1) "very much better", 2) "much better", 3) "minimally better", 4) "no change", 5) "minimally worse", 6) "much worse", or 7) "very much worse". Higher scores indicate a change for the worse and lower scores indicate a change for the better.	Weeks 4, 8 and 12
Change From Baseline in the Functional Assessment of Chronic Illness Therapy Fatigue (FACIT-F) Scale	This instrument was developed to characterize fatigue, in cancer and used in other conditions with a phenotype of fatigue. It is a 13-item measure that assesses self-reported fatigue and its impact upon daily activities and function. The recall period is 7 days and the response scale employs a 5-point Likert-type scale. The final total score is the sum of the responses for all 13 items and can range from 0 to 52. A higher score means less fatigue.	Weeks 0, 4, 8 and 12
Change From Baseline in the DePaul Post-Exertional Malaise Questionnaire (DPEMQ)	This instrument was developed to characterize and evaluate the debilitation caused by a physical exertion, whether a usual daily activity or a leisure activity. It is a 10-item questionnaire that assess both the nature of post-exertional malaise (PEM) and duration of symptom. In this study, the presence or not of PEM (based on frequency and severity of 5 PEM items) is determined by the questionnaire. The endpoint of the study is the proportion of participants with PEM at baseline and Week 12, compared between treatment groups.	Weeks 0 and 12
Change From Baseline in Physical Component Summary (PCS) of the Medical Outcomes Study Short-Form-36 (SF-36) at Weeks 4 and 8	The SF-36 questionnaire consists of 36 items grouped in eight health domains, vitality, physical functioning, bodily pain, general health perceptions, physical role functioning, emotional role functioning, social role functioning, and mental health, that can be aggregated to two summary scales, physical component summary (PCS ) and mental component summary (MCS). The PCS summarizes the physical status and constitutes the primary outcome variable. Each health domain score consists of the sum scores of the assigned questions. Scores are weighted and transformed into a scale ranging from 0 (greatest possible health restrictions, ie, severe disability) to 100 (no health restrictions). A higher score means a better physical status. The calculation process for the PCS has been previously described by Taft et al. 2001. The analysis is performed jointly with the primary outcome measure (Week 12). A positive change from baseline value means improvement, negative value means worsening.	Weeks 0, 4 and 8
Change From Baseline in the Other Aspects (Domain Scales) Than the PCS of the Medical Outcomes Study Short-Form-36 (SF-36)	The SF-36 questionnaire consists of 36 items grouped in eight health domains, vitality, physical functioning, bodily pain, general health perceptions, physical role functioning, emotional role functioning, social role functioning, and mental health, that can be aggregated to two summary scales, physical component summary (PCS ) and mental component summary (MCS). Scores are weighted and transformed into a scale ranging from 0 (greatest possible health restrictions, ie, severe disability) to 100 (no health restrictions). A higher score means a better outcome. The study endpoint is the change from baseline in score, a positive change from baseline value means improvement and a negative value means worsening outcome. For sake of conciseness, only Week 12 comparisons are presented.	Weeks 0, 4, 8 and 12
Proportion of Subjects Who Judge to Have Regained Their Daily Usual Activity Level of Pre-causative-infection.	This will be assessed by a single question with either yes or no as answer: "Do you judge that you have regained the daily usual activity level you had prior to being infected by COVID-19 back in Month xxxx? By daily usual activity we mean work, leisure, physical exercise...etc."	From Week 0 through Weeks 4, 8 and 12
Proportion of Subjects Achieving >=25% (>=50% and >=75% Presented Separately) Improvement in the Sum of Individual Core Long COVID Symptom Severity as Evaluated by a Standard 4-level Likert Scale.	The Core (most common) Long COVID symptoms are: fatigue, trouble sleeping, shortness of breath, general pain and discomfort, cognitive problems (most commonly known as brain fog or memory fog) and mental health symptoms. Each symptom is rated as: 0=No symptom, 1=Mild symptom (no interference with daily activities), 2=Moderate symptom (interfere and may limit daily activities), and 3=Severe symptom (strong interference preventing daily activities. The higher the rating is, worse is the symptom. 0 and 1 are deemed not burdensome, 2 and 3 are burdensome. A sum of the burdensome category is calculated for each visit and is the endpoint being evaluated for improvement since burdensome symptoms are those with highest impact on daily usual activity level.	Weeks 4, 8 and 12
Proportion of Subjects Achieving >=50% (>=25% and >=75% Presented Separately) Improvement in the Sum of Individual Core Long COVID Symptom Severity as Evaluated by a Standard 4-level Likert Scale.	The Core (most common) Long COVID symptoms are: fatigue, trouble sleeping, shortness of breath, general pain and discomfort, cognitive problems (most commonly known as brain fog or memory fog) and mental health symptoms. Each symptom is rated as: 0=No symptom, 1=Mild symptom (no interference with daily activities), 2=Moderate symptom (interfere and may limit daily activities), and 3=Severe symptom (strong interference preventing daily activities. The higher the rating is, worse is the symptom. 0 and 1 are deemed not burdensome, 2 and 3 are burdensome. A sum of the burdensome category is calculated for each visit and is the endpoint being evaluated for improvement since burdensome symptoms are those with highest impact on daily usual activity level.	Weeks 4, 8 and 12
Proportion of Subjects Achieving >=75% (>=25% and >=50% Presented Separately) Improvement in the Sum of Individual Core Long COVID Symptom Severity as Evaluated by a Standard 4-level Likert Scale.	The Core (most common) Long COVID symptoms are: fatigue, trouble sleeping, shortness of breath, general pain and discomfort, cognitive problems (most commonly known as brain fog or memory fog) and mental health symptoms. Each symptom is rated as: 0=No symptom, 1=Mild symptom (no interference with daily activities), 2=Moderate symptom (interfere and may limit daily activities), and 3=Severe symptom (strong interference preventing daily activities. The higher the rating is, worse is the symptom. 0 and 1 are deemed not burdensome, 2 and 3 are burdensome. A sum of the burdensome category is calculated for each visit and is the endpoint being evaluated for improvement since burdensome symptoms are those with highest impact on daily usual activity level.	Weeks 4, 8 and 12
Change From Baseline in the EuroQol-5 Dimensions -5 Levels (EQ-5D-5L) Score	EQ-5D-5L is a self-report survey that measures quality of life across 5 domains: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression. Each dimension is scored on a 5-level severity ranking that ranges from no problems (Level 1); slight; moderate; severe; and extreme problems (Level 5). Higher values indicate worse outcomes, while lower indicate better outcomes. The subscales are combined to compute a total score index, adjusted for a standard value of general population in a country/region and averaged to produce the mean and SD. The Summary index value range is from 0 to 1, where 1 is considered the best possible health and 0 is the worst possible health. For the change in score, a positive number indicates that the scores improved from baseline.	Weeks 0, 4, 8 and 12
Proportion of Subjects With Relief of at Least One Core Burdensome Long COVID Symptom for a Minimum of 2 Weeks.	The core Long COVID symptoms are: fatigue, trouble sleeping, shortness of breath, general pain and discomfort, cognitive problems (most commonly known as brain fog or memory fog) and mental health symptoms. Each symptom is rated as: 0=No symptom, 1=Mild symptom (no interference with daily activities), 2=Moderate symptom (interfere and may limit daily activities), and 3=Severe symptom (strong interference preventing daily activities. The higher the rating is, worse is the symptom. 0 and 1 are deemed not burdensome, 2 and 3 are burdensome. Relief means a reduction of severity from moderate to none, or severe to mild/none (≥2-point Likert score change)	From Week 0 to Week 12
Time to Relief of the First Core Burdensome Long COVID Symptom for a Minimum of 2 Weeks, Among Those Symptoms Present at Baseline.	The core Long COVID symptoms are: fatigue, trouble sleeping, shortness of breath, general pain and discomfort, cognitive problems (brain fog or memory fog) and mental health symptoms. Each symptom is rated as: 0=No symptom, 1=Mild symptom (no interference with daily activities), 2=Moderate symptom (interfere and may limit daily activities), and 3=Severe symptom (strong interference preventing daily activities. The higher the rating is, worse is the symptom. 0 and 1 are deemed not burdensome, 2 and 3 are burdensome. This will be assessed through periodic inventory of the core Long COVID symptoms, performed at each visit. Relief means a reduction of severity from moderate to none, or severe to mild/none (≥2-point Likert score change). A longer time is worse than a short time to resolution.	From Week 0 to Week 12
Proportion of Subjects With a Sustained Clinical Recovery, Meaning a Relief of All Core Long COVID Symptoms.	The core Long COVID symptoms are: fatigue, trouble sleeping, shortness of breath, general pain and discomfort, cognitive problems (most commonly known as brain fog or memory fog) and mental health symptoms. Each symptom is rated as: 0=No symptom, 1=Mild symptom (no interference with daily activities), 2=Moderate symptom (interfere and may limit daily activities), and 3=Severe symptom (strong interference preventing daily activities. The higher the rating is, worse is the symptom. 0 and 1 are deemed not burdensome, 2 and 3 are burdensome. This will be assessed through periodic inventory of the core Long COVID symptoms, performed at each visit. Relief means a reduction of severity from moderate to none, or severe to mild/none (≥2-point Likert score change). A higher proportion is better than a lower proportion.	Weeks 4, 8 and 12
Change From Baseline in the Total Number of Long COVID Symptoms (Core and Non-core).	This will be assessed through periodic inventory of all the Long COVID symptoms, performed at each visit, relative to the baseline inventory. A lower total number is better than a higher total number.	Weeks 0, 4, 8 and 12, as well as the longer term visit at Week 24
Proportion of Subjects With Long COVID-related Unplanned Medical Visits	This will be assessed by probing the subjects at each visit. Long COVID-related unplanned medical visits includes visits to practitioner's office, urgent care visits, emergency room <24h, or hospitalization >24 hours. A higher proportion is worse than a lower proportion	From Week 0 to Week 12
Proportion of Subjects Deceased From Any Cause Through Week 12.	This will be assessed by probing the subjects at each visit, including caretakers or relatives if the subjects cannot be reached at a given visit. A higher proportion is worse than a lower proportion	From Week 0 to Week 12
Proportion of Subjects With Significant Cardiovascular Events	A significant cardiovascular event is one that results in at least an acute care visit, a hospitalization or an event-related death. A higher proportion is worse than a lower proportion	From Week 0 to Week 12 and including up to the long-term follow-up at Week 24

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Health and Survival Follow-up (Week 24), Long COVID Symptom Count	This is now presented as part of Outcome #17. Initially planned to be separate from the reporting and analysis of the Week 12 outcomes, a longer term contact was made at Week 24 to assess the following: Presence or not of Long COVID symptoms (total number of Long COVID symptoms).	Week 24
Health and Survival Follow-up (Week 24), Significant Cardiovascular Events	General health check-up: Assess significant cardiovascular events (one that results in at least an acute care visit, a hospitalization or an event-related death) and survival.	Week 24
Baseline Values of Systemic Biomarkers of Hematologic Function (Except Hemoglobin & Hematocrit)	These will be assessed by blood samples taken at randomization visit in a subgroup of participants consented to contribute samples.	Week 0
Baseline Values of Systemic Biomarkers of Hematologic Function (Hemoglobin)	These will be assessed by blood samples taken at randomization visit in a subgroup of participants consented to contribute samples.	Week 0
Baseline Values of Systemic Biomarkers of Hematologic Function (Hematocrit)	These will be assessed by blood samples taken at randomization visit in a subgroup of participants consented to contribute samples.	Week 0
Changes Relative to Baseline (Percent Change) of Systemic Biomarkers of Hematologic Function	These will be assessed by blood samples taken at specific visits of the study in a subgroup of participants consented to contribute samples.	Weeks 0, 2 and 10
Baseline Values of Systemic Biomarkers of Inflammation and Immunologic Function (Parameters in pg/mL)	These will be assessed by blood samples taken at randomization visits of the study in a subgroup of participants consented to contribute samples.	Week 0
Baseline Values of Systemic Biomarkers of Inflammation and Immunologic Function (Calprotectin, C-reactive Protein)	These will be assessed by blood samples taken at randomization visits of the study in a subgroup of participants consented to contribute samples.	Week 0
Baseline Values of Systemic Biomarkers of Inflammation and Immunologic Function (Serotonin, Tryptophan and Taurine)	These will be assessed by blood samples taken at randomization visits of the study in a subgroup of participants consented to contribute samples.	Week 0
Changes Relative to Baseline (Percent Change) of Systemic Biomarkers of Inflammation and Immunologic Function	These will be assessed by blood samples taken at specific visits of the study in a subgroup of participants consented to contribute samples.	Weeks 0, 2 and 10
Biomarkers of Pharmacodynamic Activity - Plasma Retinol	These will be assessed by blood samples taken at specific visits of the study in a subgroup of participants consented to contribute samples.	Weeks 0, 2 and 10
Biomarkers of Pharmacodynamic Activity - Systematic Inflammation Index (SII)	These will be assessed by blood samples taken at specific visits of the study in a subgroup of participants consented to contribute samples. SII = (N × P)/L, where N, P and L (cells*10^9/L) represent absolute neutrophil counts, platelet counts and lymphocyte counts. Since SII is a ratio of concentrations, it is unitless.	Weeks 0, 2 and 10
Changes Relative to Baseline (Percent Change) of Biomarker of Pharmacodynamic Activity - Retinol	These will be assessed by blood samples taken at specific visits of the study in a subgroup of participants consented to contribute samples.	Weeks 0, 2 and 10

Collaborators and Investigators

• Sponsor: Laurent Pharmaceuticals Inc.
• Investigators: Study Director: Jean-Marie Houle, PhD, Laurent Pharmaceuticals Inc.

Study record dates

Study Major Dates

• Study Start (Actual): November 15, 2023
• Primary Completion (Actual): August 5, 2024
• Study Completion (Actual): November 30, 2024

Study Registration Dates

• First Submitted: August 11, 2023
• First Submitted That Met QC Criteria: August 16, 2023
• First Posted (Actual): August 21, 2023

Study Record Updates

• Last Update Posted (Actual): January 6, 2026
• Last Update Submitted That Met QC Criteria: December 15, 2025
• Last Verified: December 1, 2025

More Information

Terms related to this study

• Keywords: COVID-19; Long COVID; Antiviral; Inflammation control
• Additional Relevant MeSH Terms: Post-Infectious Disorders; Pathologic Processes; Chronic Disease; Disease Attributes; Respiratory Tract Infections; Infections; RNA Virus Infections; Virus Diseases; Respiratory Tract Diseases; Lung Diseases; Pneumonia, Viral; Pneumonia; Coronavirus Infections; Coronaviridae Infections; Nidovirales Infections; Pathological Conditions, Signs and Symptoms; COVID-19; Post-Acute COVID-19 Syndrome; Organic Chemicals; Retinoids; Carotenoids; Polyenes; Alkenes; Hydrocarbons, Acyclic; Hydrocarbons; Cyclohexenes; Cyclohexanes; Cycloparaffins; Hydrocarbons, Alicyclic; Hydrocarbons, Cyclic; Terpenes; Pigments, Biological; Biological Factors; Carbohydrates; Fenretinide; Sugars
• Other Study ID Numbers: LAU-23-01

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No