Long COVIDPhase 2FLINTLOCKNCT07899346
Study of VYD2311 for the Treatment of Adults With Long-COVID or Post-Vaccination Syndrome
A Phase 2 study testing VYD2311 in people with Long COVID and COVID-19 (SARS-CoV-2 Infection), run by Invivyd, Inc..
Trial summary
This Phase 2a, randomized, double-blind, placebo-controlled, proof-of-concept study is being conducted to investigate the safety (whether there are any side effects), tolerability (if it does cause side effects, how well your body handles them), pharmacokinetics (PK) (how a drug is taken into your body, spread… Read more about this study
- Who is it for?
- Ages 18 to 65 years
- Conditions the study is for
- Long COVID, COVID-19 (SARS-CoV-2 Infection), COVID 19 Vaccine
- What is being tested?
- VYD2311
- Type of treatment
- Injection or infusion
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 130 participants
- Where
- No sites listed yet
- Study dates
- Oct 2026to Jun 2027
- Phase
- Phase 2
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 65 years
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- An adult aged ≥18 to ≤65 years at the time of Screening with a BMI <50.0 kg/m2.
- Long-COVID (LC) Cohort: acute SARS-CoV-2 infection prior to onset of Long-COVID symptoms resulting in diagnosis of Long-COVID.
- Post-Vaccination Syndrome (PVS) Cohort: Administered at least a single dose of a SARS-CoV-2 vaccine prior to the onset of symptoms resulting in diagnosis of PVS.
- 3. Clinical evidence of at least 2 new or worsening LC or PVS symptoms with at least 1 symptom considered grade 3 or greater in severity which: (i) LC Cohort - presented between 6 and 24 months after inciting acute COVID-19 infection.
- PVS Cohort - presented and persisted after administration of a COVID-19 vaccine.
- are not primarily attributable to a pre-existing condition or alternative diagnosis confirmed by the investigator during screening: chest pain, diarrhea, abdominal pain, nausea, loss of smell or taste, palpitations, shortness of breath, cough, sleep apnea, swelling of legs, weakness, muscle pain, joint pain, back pain, foot pain, abnormal movements, tremor, headache, sleep disturbance, difficulty with memory/concentration ("brain fog"), fatigue, post-exertional malaise.
Who cannot join
- Has had an unplanned hospitalization or had major surgery (e.g., requiring general anesthesia or opening of a major body cavity) within 3 months of Screening or has a planned hospitalization or major surgery during the study period.
- Has any pre-existing disease, condition, or disorder that is associated with symptoms that overlap or could confound the evaluation of LC or PVS (e.g., fatigue, pain, cognitive impairment, dysautonomia, exercise intolerance), including but not limited to, myalgic encephalomyelitis/chronic fatigue syndrome, post-treatment Lyme disease, fibromyalgia, autonomic disorders (e.g., postural orthostatic tachycardia syndrome), disorders affecting cognitive function, primary sleep disorders, or other conditions that, in the opinion of the Investigator, could confound the results obtained from clinical activity evaluations.
- Has any current serious concomitant systemic disease, condition, or disorder that, in the opinion of the Investigator, may lead to new treatments, hospitalization, or death within the study period, including but not limited to, active malignancy, organ failure, recent cardiovascular disease or stroke, uncontrolled diabetes, major psychiatric disorders, that could confound the results of the study or confer an additional risk to the participant by their participation in the study.
- Has moderate to severe immune compromise due to a medical condition or immunosuppressing medications.
- Has known active Hepatitis B (HBV) or Hepatitis C (HCV) infection or known human immunodeficiency virus (HIV) infection with a currently detectable viral load, current HIV-related symptoms, or an unstable antiretroviral regimen (initiated or changed within the past 3 months prior to Screening).
- Has received a COVID-19 vaccine within 60 days before Screening or planned receipt during the study period, or any non-COVID-19 vaccine within 14 days before Screening or within 7 days before or after each study dose. Note: Vaccination during the study period should be avoided unless medically indicated, such as a seasonal vaccine or if the vaccine cannot be deferred until after the study.
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- Has been treated with or anticipates being treated during the study period with any of the following medications:
- A mAb with activity against SARS-CoV-2 within 12 months before Screening.
- An antiviral with activity against SARS-CoV-2 within 30 days before Screening.
- Convalescent plasma or intravenous immunoglobulin (IVIg) within 60 days before Screening.
- Systemic corticosteroids at doses >20 mg per day of prednisolone or equivalent for >14 consecutive days within 30 days before Screening.
- Other systemic immunosuppressive medications, such as biologics, immunomodulators, or cancer chemotherapy, within 90 days before Screening. Note: Topical, inhaled, intranasal, ophthalmic, or locally injected corticosteroids or other immunosuppressants are permitted, provided there is no evidence of clinically meaningful systemic immunosuppressive effect.
- NOTE: The above information is not intended to contain all considerations relevant to a participant's potential eligibility in the clinical trial.
Trial locations and contacts
No sites are listed yet. Contact the study team or a site near you to ask about taking part.
About this study
Official title: A Phase 2a, Randomized, Double-Blind, Placebo-Controlled, Proof-of-Concept Study to Evaluate the Safety, Pharmacokinetics, and Clinical Activity of VYD2311 for the Treatment of Adults With Long-COVID or Post-Vaccination Syndrome (FLINTLOCK)
This Phase 2a, randomized, double-blind, placebo-controlled, proof-of-concept study is being conducted to investigate the safety (whether there are any side effects), tolerability (if it does cause side effects, how well your body handles them), pharmacokinetics (PK) (how a drug is taken into your body, spread throughout, broken down, and eliminated), clinical activity (does the drug make patients feel better), immunogenicity (how the immune system responds to the drug), and serum virus neutralizing antibody response (antibodies that block a virus from infecting cells) of VYD2311, the investigational monoclonal antibody being studied, in adults with Long-COVID or Post-Vaccination Syndrome.
Participants will receive an intravenous (IV) infusion on Day 1 of either the investigational drug or placebo followed by two intramuscular (IM) injections (a shot in the upper arm), one on day 30 and the other on Day 60. The IM injections will also either be investigational drug or placebo. The participants will be then asked to complete a 30-day follow up period and end the study on day 90.
- Being tested
- VYD2311, Placebo
- Keywords
- Post-Vaccination Syndrome, PVS
- Medical subject headings
- Post-Acute COVID-19 Syndrome, COVID-19
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
VYD2311Drug
Dosing via intravenous (IV) infusion on Day 1 follow by dosing via intramuscular (IM) injection on Day 30 and Day 60 with VYD2311
PlaceboDrug
Dosing via intravenous (IV) infusion on Day 1 follow by dosing via intramuscular (IM) injection on Day 30 and Day 60 with placebo (normal saline)
| Study group | Role | What they receive |
|---|---|---|
| VYD2311 | Experimental | Dosing via intravenous (IV) infusion on Day 1 follow by dosing via intramuscular (IM) injection on Day 30 and Day 60 with VYD2311 Receives: Drug: VYD2311 |
| Placebo | Placebo comparator | Dosing via intravenous (IV) infusion on Day 1 follow by dosing via intramuscular (IM) injection on Day 30 and Day 60 with Placebo - 0.9% sodium chloride (normal saline) Receives: Drug: Placebo |
What is being measured
The primary outcome is the main question the study is designed to answer.
Assessment of safety based on treatment emergent adverse events, injection site reactions, and hypersensitivity reactions through Day 90
Measured: 90 days
Serum concentrations of VYD2311 through Day 90
Measured: 90 days
Secondary outcomes (7)
Change in score of the PROMIS-29+2 from baseline through Day 90
Measured: 90 days
Change in score of the PCFS from baseline through Day 90
Measured: 90 days
Change in score of the PGI-C from baseline through Day 90
Measured: 90 days
Change in score of the PGI-S from baseline through Day 90
Measured: 90 days
Change in score of the SDMT from baseline through Day 90
Measured: 90 days
Incidence of ADAs against VYD2311 through Day 90
Measured: 90 days
sVNA titers (VYD2311 serum concentration/variant IC50) against relevant SARS-CoV-2 variants through Day 90
Measured: 90 days
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted27 Oct 2026
- Study startOct 2026 (estimated)
- Primary completionJun 2027 (estimated)
- Study completionJun 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Long COVIDStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 2
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Quadruple blind
- Who is masked
- Participant, Care provider, Investigator, Outcomes assessor
- Enrolment
- 130 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Invivyd, Inc.
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07899346
- Sponsor's protocol ID
- VYD2311-COV-201
- Acronym
- FLINTLOCK
- Status last verified
- Oct 2026
- First submitted
- 20 Oct 2026
- Last updated
- 27 Oct 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 27 Oct 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A Phase 2a, Randomized, Double-Blind, Placebo-Controlled, Proof-of-Concept Study to Evaluate the Safety, Pharmacokinetics, and Clinical Activity of VYD2311 for the Treatment of Adults With Long-COVID or Post-Vaccination Syndrome (FLINTLOCK)
- ClinicalTrials.gov ID
- NCT07899346
- Acronym / sponsor ID
- FLINTLOCK / VYD2311-COV-201
- Keywords
- Post-Vaccination Syndrome, PVS
- Phase
- Phase 2
- Study type
- Interventional
- Recruitment status
- Not yet recruiting
- Enrolment
- 130 participants (estimated)
- Lead sponsor
- Invivyd, Inc.Industry (pharma, biotech, devices)
- Study start
- Oct 2026 (estimated)
- Primary completion
- Jun 2027 (estimated)
- Study completion
- Jun 2027 (estimated)
- First posted
- 27 Oct 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
This Phase 2a, randomized, double-blind, placebo-controlled, proof-of-concept study is being conducted to investigate the safety (whether there are any side effects), tolerability (if it does cause side effects, how well your body handles them), pharmacokinetics (PK) (how a drug is taken into your body, spread throughout, broken down, and eliminated), clinical activity (does the drug make patients feel better), immunogenicity (how the immune system responds to the drug), and serum virus neutralizing antibody response (antibodies that block a virus from infecting cells) of VYD2311, the investigational monoclonal antibody being studied, in adults with Long-COVID or Post-Vaccination Syndrome.
Participants will receive an intravenous (IV) infusion on Day 1 of either the investigational drug or placebo followed by two intramuscular (IM) injections (a shot in the upper arm), one on day 30 and the other on Day 60. The IM injections will also either be investigational drug or placebo. The participants will be then asked to complete a 30-day follow up period and end the study on day 90.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Quadruple blind (participant, care provider, investigator, outcomes assessor)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| VYD2311 | Experimental | Drug: VYD2311Dosing via intravenous (IV) infusion on Day 1 follow by dosing via intramuscular (IM) injection on Day 30 and Day 60 with VYD2311 |
| Placebo | Placebo comparator | Drug: PlaceboDosing via intravenous (IV) infusion on Day 1 follow by dosing via intramuscular (IM) injection on Day 30 and Day 60 with Placebo - 0.9% sodium chloride (normal saline) |
Who may qualify
- Ages
- 18 to 65 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (6 listed)
- An adult aged ≥18 to ≤65 years at the time of Screening with a BMI <50.0 kg/m2.
- Long-COVID (LC) Cohort: acute SARS-CoV-2 infection prior to onset of Long-COVID symptoms resulting in diagnosis of Long-COVID.
- Post-Vaccination Syndrome (PVS) Cohort: Administered at least a single dose of a SARS-CoV-2 vaccine prior to the onset of symptoms resulting in diagnosis of PVS.
- 3. Clinical evidence of at least 2 new or worsening LC or PVS symptoms with at least 1 symptom considered grade 3 or greater in severity which: (i) LC Cohort - presented between 6 and 24 months after inciting acute COVID-19 infection.
- PVS Cohort - presented and persisted after administration of a COVID-19 vaccine.
Key exclusion criteria (13 listed)
- Has had an unplanned hospitalization or had major surgery (e.g., requiring general anesthesia or opening of a major body cavity) within 3 months of Screening or has a planned hospitalization or major surgery during the study period.
- Has any pre-existing disease, condition, or disorder that is associated with symptoms that overlap or could confound the evaluation of LC or PVS (e.g., fatigue, pain, cognitive impairment, dysautonomia, exercise intolerance), including but not limited to, myalgic encephalomyelitis/chronic fatigue syndrome, post-treatment Lyme disease, fibromyalgia, autonomic disorders (e.g., postural orthostatic tachycardia syndrome), disorders affecting cognitive function, primary sleep disorders, or other conditions that, in the opinion of the Investigator, could confound the results obtained from clinical activity evaluations.
- Has any current serious concomitant systemic disease, condition, or disorder that, in the opinion of the Investigator, may lead to new treatments, hospitalization, or death within the study period, including but not limited to, active malignancy, organ failure, recent cardiovascular disease or stroke, uncontrolled diabetes, major psychiatric disorders, that could confound the results of the study or confer an additional risk to the participant by their participation in the study.
- Has moderate to severe immune compromise due to a medical condition or immunosuppressing medications.
- Has known active Hepatitis B (HBV) or Hepatitis C (HCV) infection or known human immunodeficiency virus (HIV) infection with a currently detectable viral load, current HIV-related symptoms, or an unstable antiretroviral regimen (initiated or changed within the past 3 months prior to Screening).
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| VYD2311Dosing via intravenous (IV) infusion on Day 1 follow by dosing via intramuscular (IM) injection on Day 30 and Day 60 with VYD2311 | Drug | VYD2311 |
| PlaceboDosing via intravenous (IV) infusion on Day 1 follow by dosing via intramuscular (IM) injection on Day 30 and Day 60 with placebo (normal saline) | Drug | Placebo |
Primary outcome
Assessment of safety based on treatment emergent adverse events, injection site reactions, and hypersensitivity reactions through Day 90
Time frame: 90 days
Serum concentrations of VYD2311 through Day 90
Time frame: 90 days
7 secondary outcomes
Change in score of the PROMIS-29+2 from baseline through Day 90
Time frame: 90 days
Change in score of the PCFS from baseline through Day 90
Time frame: 90 days
Change in score of the PGI-C from baseline through Day 90
Time frame: 90 days
Change in score of the PGI-S from baseline through Day 90
Time frame: 90 days
Change in score of the SDMT from baseline through Day 90
Time frame: 90 days
Incidence of ADAs against VYD2311 through Day 90
Time frame: 90 days
sVNA titers (VYD2311 serum concentration/variant IC50) against relevant SARS-CoV-2 variants through Day 90
Time frame: 90 days
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 27 Oct 2026.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Questions about this trial
What is this clinical trial studying?
A Phase 2 study testing VYD2311 in people with Long COVID and COVID-19 (SARS-CoV-2 Infection), run by Invivyd, Inc..
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 6 inclusion and 13 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: opening soon, as of the sponsor's last update on 27 Oct 2026. Status can change between updates, so confirm with the study contact before making plans.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Study Inquiry (781-819-0080, flintlockstudy@invivyd.com), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Assessment of safety based on treatment emergent adverse events, injection site reactions, and hypersensitivity reactions through Day 90 (time frame: 90 days). The study lists 2 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 27 Oct 2026.