A Phase 3 interventional study of MK-1406 and Placebo in Influenza, sponsored by Cidara Therapeutics Inc., a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA). Recruiting at 211 sites in 6 countries. Open to participants aged 12 Years and older. Per ClinicalTrials.gov, last updated 2026-11-13.
Sponsored by Cidara Therapeutics Inc., a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA) (part of Merck & Co., Inc) · Phase 3, Interventional, and Prevention
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Among 966 studies in Influenza, Human with a site in United States — 60 open to participants now, 85 under way, 7 of them phase 3. Influenza, Human · United States.
Among the 966 studies in Influenza, Human with a site in United States, this one is the 62nd largest by planned enrollment of the 843 interventional ones that give a count, is one of 29 that started in 2025, is one of 116 in phase 3, reaches primary completion later than 41 of the 83 other live ones, and was the 933rd registered.
2,358 studies on the registry are indexed under Influenza, Human; 184 are open to participants now.
Browse Influenza, Human studies →60 of the 966 studies in Influenza, Human with a site in United States are open now. Recruiting first, the newest first:
National Institute of Allergy and Infectious Diseases (NIAID) · Sites in United States
Ages 18–55 · Healthy volunteers
ModernaTX, Inc. · Sites in United States
Ages 65+ · Healthy volunteers
ModernaTX, Inc. · Sites in United States
Ages 9–17 · Healthy volunteers
National Institute on Deafness and Other Communication Disorders (NIDCD) · Sites in United States
Ages 18–99 · Healthy volunteers
David Moss · Sites in United States
Ages 18+ · Healthy volunteers
A study can be open while its sites in United States have not opened yet or have stopped. Only those recruiting at a site in United States →
Of the 121 Influenza, Human studies recruiting now, 66 (55%) set no upper age limit and 45 (37%) stop at 75 or younger; 33 take children under 18; 67 take healthy volunteers.
This study: 12 Years and older · all sexes · no healthy volunteers.
The full table on the hub →This tab as a report to print or save as PDF → With an account.
966 studies; the count open now beside each. This study's row is marked.
A study in two phases is counted once above. Listed by phase, each with its combined phases: Phase 1 249 · Phase 2 244 · Phase 3 127 · Phase 4 147
First in 1997; this study’s year is marked. 29 started in 2025.
By drug class, each counting the studies that test any of its medicines:
This study's planned enrollment of 10,000 is above the median of 227 across 1,957 interventional studies indexed under Influenza, Human.
Median enrollment 270 across the 843 interventional studies, 261 across the 122 observational. Of the 841 that completed or were terminated, 433 (51%) have results posted.
This tab as a report to print or save as PDF → With an account.
435 of 966 have an industry lead sponsor. The 10 most frequent:
This study is registered under Cidara Therapeutics Inc., a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA), one of the names counted as Merck & Co., Inc. Under that name alone:
Cidara Therapeutics Inc., a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA) is the lead sponsor of 4 studies on the registry; 2 are open to participants now.
Merck & Co., Inc has 7 studies filed under Influenza, Human — fewer than ten, so there is no comparison to draw.
41 of the studies in Influenza, Human with a site in United States that are under way reach primary completion within a year, 5 of them phase 3. Phase 3 first, then by date:
| Study | Primary completion |
|---|---|
| NCT07496450Phase 3ModernaTX, Inc.A Study of mRNA-1018-H5 Pandemic Influenza Vaccine in Healthy Adults | 2027-01-28 |
| NCT06094010Phase 3Hoffmann-La RocheA Surveillance Study of Susceptibility to Baloxavir Marboxil in Pediatric Participants With Influenza and Transmission of Influenza to Household Contacts | 2027-05-11 |
| NCT07159763Phase 3Cidara Therapeutics Inc., a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA)A Study to Evaluate the Safety and Efficacy of MK-1406/CD388 for Prevention of Influenza (MK-1406-005/CD388.SQ.3.06) | 2027-07-02 |
| NCT07851246Phase 3GlaxoSmithKlineA Study to Evaluate the Immune Response and Safety of a Vaccine Against Influenza in Adults 18-64 Years of Age | 2027-07-09 |
| NCT05624450Phase 3AstraZenecaEfficacy and Safety of Tozorakimab in Patients Hospitalised for Viral Lung Infection Requiring Supplemental Oxygen | 2027-11-04 |
Add all 41 to your calendar (.ics) → With an account.
Among the 966 studies in Influenza, Human with a site in United States, from their registry updates:
This tab as a report to print or save as PDF → With an account.
Approximately one billion cases of seasonal influenza occur annually. Of these, 3 to 5 million illnesses are severe and responsible for up to 650,000 deaths per year (WHO 2025). Yearly administration of an influenza vaccine for the prevention of influenza is currently recommended. However, the real-world vaccine effectiveness varied from 10% to 60% in the general population across the years of 2004 to 2024, with effectiveness in most years below 50% (CDC 2025) and decreasing to as low as 5% in immunocompromised individuals (Hughes 2021).
The goal of this study is to learn whether MK-1406 (CD388) can help prevent the flu in people who are at higher risk of becoming seriously ill from influenza. Researchers want to find out if MK-1406 dosed at a single study visit can provide protection against influenza compared with placebo. The study will include adolescents and adults who may be more vulnerable to complications from influenza because of their age, health conditions, or weakened immune systems. Researchers will also evaluate the safety of MK-1406 and how well participants tolerate the study medicine.
This is a Phase 3, randomized, double-blind, placebo-controlled, parallel-group, multicenter study to evaluate the efficacy, safety, and tolerability of MK-1406 (CD388) administered as a single dose via 3 subcutaneous (SC) injections in adult and adolescent participants who are at higher risk of developing complications from influenza.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
The main inclusion criteria include but are not limited to the following:
Primary Stratum A (non- participants who have chronic stable medical conditions) and Primary Stratum B (participants who are immunocompromised either due to underlying disease or receipt of immunosuppressive medications)
Primary Stratum A only
Primary Stratum B only
Participants who have had a solid organ transplant (SOT) must satisfy all of the following:
Participants who have had a hematopoietic stem cell transplant () must satisfy at least one of the following:
Exclusion Criteria:
The main exclusion criteria include but are not limited to the following:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Stem cell (bone marrow) transplants. Allogeneic uses cells from a donor; autologous uses your own cells, collected earlier and given back.
After a transplant from a donor, the donor’s immune cells attack the recipient’s body, often the skin, gut or liver.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Blood cells that help blood clot. Too few raises the risk of bleeding and bruising. A usual adult range is about 150–400 × 10⁹/L (150,000–400,000 per µL); each lab has its own reference range.
Immunosuppression
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Cancer (malignancy)
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Allogeneic and autologous transplant
Stem cell (bone marrow) transplants. Allogeneic uses cells from a donor; autologous uses your own cells, collected earlier and given back.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
GVHD (graft-versus-host disease)
After a transplant from a donor, the donor’s immune cells attack the recipient’s body, often the skin, gut or liver.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HIV
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Platelets
Blood cells that help blood clot. Too few raises the risk of bleeding and bruising. A usual adult range is about 150–400 × 10⁹/L (150,000–400,000 per µL); each lab has its own reference range.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants will receive 450 milligrams (mg) dose of MK-1406 (CD388) by subcutaneous (SC) injection.
Combination Product: MK-1406
Participants will receive placebo by SC injection.
Combination Product: Placebo
MK-1406 liquid for injection administered subcutaneously (SC)
Also known as: CD388
MK-1406 matched liquid for SC injection
Number of Participants Experiencing Protocol-defined Influenza-like Illness (ILI) Occurring ≥7 Days after and up to 24 Weeks after Administration of Study Drug
Protocol-defined ILI includes: 1) Influenza infection confirmed by a reverse transcriptase-polymerase chain reaction positive (RT-PCR +) result from nasopharyngeal (NP) swab assayed at a central laboratory AND 2) New onset or worsening of ≥ 2 respiratory symptoms (nasal congestion, sore throat, or cough) OR New onset or worsening of 1 respiratory symptom (nasal congestion, sore throat, or cough) AND new onset of ≥ 1 systemic symptom (headache, feeling feverish or chills, body aches/pains, or fatigue). Number of participants experiencing protocol-defined ILI occurring after administration of MK-1406 (CD388), with influenza infection confirmed by an RT-PCR+ result based on a NP swab assayed at a central laboratory (first occurrence only), as compared to placebo will be assessed.
Time frame: Up to approximately 24 weeks post dose
Number of participants with ≥1 Adverse Event (AE)
An AE is defined as any untoward medical occurrence in a participant administered a pharmaceutical product temporally associated with the use of study treatment, whether or not considered related to the study treatment. The number of participants with ≥1 AE will be assessed.
Time frame: Up to approximately Day 197
Number of Participants Who Discontinued from the Study Due to an AE
An AE is defined as any untoward medical occurrence in a participant administered a pharmaceutical product temporally associated with the use of study treatment, whether or not considered related to the study treatment. The number of participants who discontinued the study because of an AE will be assessed.
Time frame: Up to approximately Day 197
Number of Participants with Injection Site Reactions (ISRs)
Participants will complete the injection site reaction questionnaire in the eDiary Day 1 through Day 8 following the study intervention administration to assess for reactogenicity, based on the US Food and Drug Administration (FDA) toxicity grading scale used for vaccine trials. Injection site reactions are graded on a scale from 1 to 5 where Grade 1 is mild, Grade 2 is moderate, Grade 3 is severe and Grade 4 is potentially life threatening. The injection-site reactions assessed are pain, tenderness, erythema/redness, and induration/swelling.
Time frame: Up to approximately Day 8 post dose
Number of Stratum B Participants Experiencing Protocol-defined Influenza-like Illness (ILI) Occurring ≥7 Days after and up to 24 Weeks after Administration of Study Drug
Protocol-defined ILI includes: 1) Influenza infection confirmed by a reverse transcriptase-polymerase chain reaction positive (RT-PCR +) result from nasopharyngeal (NP) swab assayed at a central laboratory AND 2) New onset or worsening of ≥ 2 respiratory symptoms (nasal congestion, sore throat, or cough) OR New onset or worsening of 1 respiratory symptom (nasal congestion, sore throat, or cough) AND new onset of ≥ 1 systemic symptom (headache, feeling feverish or chills, body aches/pains, or fatigue). Number of Stratum B ((immunocompromised participants) experiencing protocol-defined ILI occurring after administration of CD388, with influenza infection confirmed by an RT-PCR+ result based on an NP swab assayed at a central laboratory (first occurrence only), as compared to placebo will be assessed.
Time frame: Up to approximately 24 weeks post dose
Number of Participants with All-cause Hospitalization within 30 Days after the Onset of Symptomatic Laboratory-Confirmed Influenza
Hospitalizations are defined as an overnight admission in a hospital or similar acute care facility, including emergency rooms due to any cause within 30 days after the onset of symptomatic laboratory-confirmed influenza infection which occurred from ≥ 7 days after and up to 24 weeks after study intervention administration. Number of participants with all-cause hospitalization within 30 days after the onset of symptomatic influenza will be assessed.
Time frame: Up to 30 days after onset of symptomatic laboratory-confirmed influenza
Number of Participants with All-cause Mortality within 30 Days after the Onset of Symptomatic Laboratory-Confirmed Influenza
Number of participants with mortality due to any cause within 30 days after the onset of symptomatic laboratory-confirmed influenza infection which occurred from ≥ 7 days after and up to 24 weeks after study intervention administration will be determined.
Time frame: Up to 30 days after onset of symptomatic laboratory-confirmed influenza
Plasma Concentrations Following Administration of MK-1406 (CD388)
Blood samples will be collected at multiple time points to assess the plasma concentrations of MK-1406.
Time frame: Day 1 (pre-dose), Day 29, and Day 197 post dose
Number of Participants with Treatment Emergent Anti-Drug Antibodies (ADAs)
The number of participants with confirmed anti MK-1406 antibodies post-baseline (i.e. treatment-emergent ADAs) will be determined via evaluation of blood samples collected at multiple time points.
Time frame: Day 1 (pre-dose), Day 29, and Day 197 post dose
Number of Participants with Treatment Boosted ADAs
The number of participants with an increase in ADA titer over an initial positive baseline titer (i.e., treatment-boosted ADAs) will be determined will be determined via evaluation of blood samples collected at multiple time points.
Time frame: Day 1 (pre-dose), Day 29, and Day 197 post dose
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Showing the first 100 of 211 sites across 6 countries. Choose a country and city above to see the rest.
Plan to share: Yes — https://trialstransparency.msdclinicaltrials.com/pdf/ProcedureAccessClinicalTrialData.pdf
Data sharing details ↗ · externaldatasharing-msd.com
Started Sep 2025 (actual). Primary completion is estimated for Jul 2027, 21 months after the start.
Of 119 industry-sponsored phase 3 interventional studies under Influenza, Human, half reached primary completion within 8 months of starting (the median), counting those still running; a quarter within 3 and three quarters within 14. This study's planned 21 months is above that.
Counting every sponsor, half of 154 studies reached it within 8 months; a quarter within 4 and three quarters within 15.
Since we started tracking on Sep 25, 2026, the dates moved once, on Nov 13, 2026: primary completion Jun 2027 → Jul 2027 and completion Jun 2027 → Jul 2027.
Earlier changes are on the record history on ClinicalTrials.gov ↗
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
Eligibility is decided by the study team. Share this record with your doctor or contact the team directly.
Contact study teamGet an email when the registry record changes — status, dates, results — or when someone posts here.
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Nothing here yet. If you are running this trial, taking part in it, or weighing whether to, this is the place to say so.
Studies of the drug tested here: MK-1406
Cidara Therapeutics Inc., a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA) →