HealthyPhase 1NCT07199452
A Study of Rifabutin and MK-4646 in Healthy Participants (MK-4646-004)
A Phase 1 study testing MK-4646 and Rifabutin in people with Healthy, run by Merck Sharp & Dohme LLC at 1 site in United States.
Trial summary
Researchers have designed a new study medicine called MK-4646 as a new way to treat human immunodeficiency virus (HIV). Rifabutin is a medication used to treat tuberculosis (TB). Researchers want to learn about MK-4646 when taken at the same time as Rifabutin. Read more about this study
- Who is it for?
- Ages 18 to 55 yearsHealthy volunteers can take part
- Conditions the study is for
- Healthy
- What is being tested?
- MK-4646 and Rifabutin
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 18 participants
- Where
- 1 siteUnited States
- Study dates
- 28 Oct 2025to 7 Jan 2026
- Phase
- Phase 1
- Are there results?
- None posted in the registry
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 55 years
- All sexes
- Healthy volunteers accepted
- Adult
The main inclusion criteria include but are not limited to:
- Is in good health
- Has a body-mass index (BMI) between 18 and 32 kg/m2
The main exclusion criteria include but are not limited to:
- Has a history of clinically significant endocrine, gastrointestinal, cardiovascular, hematological, hepatic, immunological, renal, respiratory, genitourinary, or major neurological (including stroke and chronic seizures) abnormalities or diseases
- Has a history of cancer (malignancy)
Trial locations and contacts
1 site in 1 country.
United States1 site
Fortea CRU Madison ( Site 0001)
Madison, Wisconsin, 53704
About this study
Official title: An Open-Label Clinical Study to Evaluate the Effects of Multiple Oral Doses of Rifabutin on the Single-Dose Pharmacokinetics of MK-4646 in Healthy Participants
Researchers have designed a new study medicine called MK-4646 as a new way to treat human immunodeficiency virus (HIV). Rifabutin is a medication used to treat tuberculosis (TB).
Researchers want to learn about MK-4646 when taken at the same time as Rifabutin.
They want to:
Measure a person's blood to find out if the amount of MK-4646 in the blood is the same when MK-4646 is taken alone or with Rifabutin Learn about the safety of MK-4646 when taken alone or with Rifabutin and if people tolerate it
- Conditions
- Healthy
- Being tested
- MK-4646, Rifabutin
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
MK-4646Drug
Oral Capsule
RifabutinDrug
Oral Capsule
| Study group | Role | What they receive |
|---|---|---|
| MK-4646 | Experimental | On Period 1 Day 1, a single oral dose of MK-4646 will be administered. Receives: Drug: MK-4646 |
| MK-4646 with Rifabutin | Experimental | Rifabutin will be administered orally once daily from Period 2 Day 1 through Period 2 Day 16. A single oral dose of MK-4646 will be administered on Period 2 Day 14. Receives: Drug: MK-4646; Drug: Rifabutin |
What is being measured
The primary outcome is the main question the study is designed to answer.
Area Under the Concentration-time Curve from Time 0 Extrapolated to Infinity (AUC0-inf) of MK-4646 in Plasma
Blood samples will be collected to determine the AUC0-inf of MK-4646 in plasma.
Measured: At designated timepoints (up to approximately 3 days post dose)
Secondary outcomes (2)
Number of Participants Who Experience an Adverse Event (AE)
An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a study intervention. The number of participants who experience an AE will be reported.
Measured: Up to approximately 5 weeks
Number of Participants Who Discontinue Study Treatment Due to an AE
An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a study intervention. The number of participants who discontinue study treatment due to an AE will be reported.
Measured: Up to approximately 3 weeks
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted30 Sep 2025
- Study start28 Oct 2025
- Primary completion27 Dec 2025
- Study completion7 Jan 2026
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for HealthyStudies of the same condition, open and under way.
- More trials run by Merck Sharp & Dohme LLCThe sponsor's other registered studies.
- 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 1
- Primary purpose
- Basic science
- Allocation
- Non-randomised
- Intervention model
- Crossover
- Masking
- None (open label)
- Enrolment
- 18 participants (actual)
Sponsor and investigators
- Lead sponsor
- Merck Sharp & Dohme LLC
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
- Investigators
- Medical Director, Study director, Merck Sharp and Dohme LLC
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07199452
- Sponsor's protocol ID
- 4646-004
- Other IDs
- MK-4646-004
- Status last verified
- Jan 2026
- First submitted
- 22 Sep 2025
- Last updated
- 29 Jan 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- Yes: https://trialstransparency.msdclinicaltrials.com/pdf/ProcedureAccessClinicalTrialData.pdf
Study at a glance
From the registry record, last updated by the sponsor on 29 Jan 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- An Open-Label Clinical Study to Evaluate the Effects of Multiple Oral Doses of Rifabutin on the Single-Dose Pharmacokinetics of MK-4646 in Healthy Participants
- ClinicalTrials.gov ID
- NCT07199452
- Acronym / sponsor ID
- 4646-004
- Conditions
- Healthy
- Phase
- Phase 1
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 18 participants (actual)
- Lead sponsor
- Merck Sharp & Dohme LLCIndustry (pharma, biotech, devices)
- Study start
- 28 Oct 2025 (actual)
- Primary completion
- 27 Dec 2025 (actual)
- Study completion
- 7 Jan 2026 (actual)
- First posted
- 30 Sep 2025 (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.
Researchers have designed a new study medicine called MK-4646 as a new way to treat human immunodeficiency virus (HIV). Rifabutin is a medication used to treat tuberculosis (TB).
Researchers want to learn about MK-4646 when taken at the same time as Rifabutin.
They want to:
Measure a person's blood to find out if the amount of MK-4646 in the blood is the same when MK-4646 is taken alone or with Rifabutin Learn about the safety of MK-4646 when taken alone or with Rifabutin and if people tolerate it
Study design
- Primary purpose
- Basic science
- Allocation
- Non-randomised
- Intervention model
- Crossover
- Masking
- None (open label)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| MK-4646 | Experimental | Drug: MK-4646On Period 1 Day 1, a single oral dose of MK-4646 will be administered. |
| MK-4646 with Rifabutin | Experimental | Drug: MK-4646, Drug: RifabutinRifabutin will be administered orally once daily from Period 2 Day 1 through Period 2 Day 16. A single oral dose of MK-4646 will be administered on Period 2 Day 14. |
Who may qualify
- Ages
- 18 to 55 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
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 |
|---|---|---|
| MK-4646Oral Capsule | Drug | MK-4646, MK-4646 with Rifabutin |
| RifabutinOral Capsule | Drug | MK-4646 with Rifabutin |
Primary outcome
Area Under the Concentration-time Curve from Time 0 Extrapolated to Infinity (AUC0-inf) of MK-4646 in Plasma
Time frame: At designated timepoints (up to approximately 3 days post dose)
Blood samples will be collected to determine the AUC0-inf of MK-4646 in plasma.
2 secondary outcomes
Number of Participants Who Experience an Adverse Event (AE)
Time frame: Up to approximately 5 weeks
Number of Participants Who Discontinue Study Treatment Due to an AE
Time frame: Up to approximately 3 weeks
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 29 Jan 2026.
- Merck Clinical Trials InformationLink provided by the sponsor.
- Individual participant dataSharing planned: Yes. https://trialstransparency.msdclinicaltrials.com/pdf/ProcedureAccessClinicalTrialData.pdf
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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. This study is not recruiting at the moment.
Medical Director study director
Merck Sharp and Dohme LLC
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 1 study testing MK-4646 and Rifabutin in people with Healthy, run by Merck Sharp & Dohme LLC at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
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: finished, as of the sponsor's last update on 29 Jan 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. 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 1 studies test a treatment in a small group of people for the first time or in a new way, mainly to check safety and find the right dose.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Area Under the Concentration-time Curve from Time 0 Extrapolated to Infinity (AUC0-inf) of MK-4646 in Plasma (time frame: At designated timepoints (up to approximately 3 days post dose)). 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 29 Jan 2026.