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Completed

NCT Number: NCT07086079

A Study of Doravirine/Islatravir in Healthy Lactating Females (MK-8591A-061)

The goal of this study is to learn what happens to doravirine (DOR) and islatravir (ISL) in a healthy lactating female's body over time. Researchers want to learn if DOR and ISL are in breast milk.

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Key information

Conditions

Healthy

Age range

18 year and older

Sex eligibility

Female

Study type

Interventional

Phase

Phase 1

Primary location

QPS Missouri ( Site 0001)

Springfield, Missouri, 65802, United States

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

The main inclusion criteria include but are not limited to the following:

  • Is at least 6-weeks postpartum at the time of administration of study drug, following the delivery of a healthy singleton neonate
  • Is willing and able to express breast milk using an electric pump prior to study drug administration and is expected to be able to express at least 4 times over a 24-hour period after study drug administration

Exclusion criteria

The main exclusion criteria include but are not limited to the following:

  • Has a history of clinically significant endocrine, gastrointestinal, cardiovascular, hematological, hepatic, immunological, renal, respiratory, genitourinary, psychiatric, or major neurological (including stroke and chronic seizures) abnormalities or diseases
  • Has had mastitis within 30 days prior to administration of study drug

Treatment and study plan

DOR/ISL

Drug

Oral tablet

Other names: MK-8591A

Primary outcomes

  1. Cumulative Amount of DOR Excreted in Breast Milk From 0 to 24 Hours (Ae0-24hrs)

    Time frame: Predose and at designated timepoints up to 24 hours postdose

    Breast milk samples will be collected to determine the Ae0-24hrs after administration of DOR.

  2. Body Weight Normalized Infant Theoretical Dose of DOR

    Time frame: Predose and at designated timepoints up to 24 hours postdose

    Breast milk samples will be collected to calculate the theoretical daily (24 hour) infant dose of DOR as normalized by participant-reported infant body weight.

  3. Relative Infant Theoretical Dose of DOR

    Time frame: Predose and at designated timepoints up to 24 hours postdose

    Breast milk samples will be collected to calculate the theoretical daily (24 hour) infant dose of DOR relative to the maternal dose.

  4. Cumulative Amount of Total ISL Excreted in Breast Milk From 0 to 24 Hours (Ae0-24hrs)

    Time frame: Predose and at designated timepoints up to 24 hours postdose

    Breast milk samples will be collected to determine the Ae0-24hrs after administration of total ISL.

  5. Body Weight Normalized Infant Theoretical Dose of ISL

    Time frame: Predose and at designated timepoints up to 24 hours postdose

    Breast milk samples will be collected to calculate the theoretical daily (24 hour) infant dose of ISL as normalized by participant-reported infant body weight.

  6. Relative Infant Theoretical Dose of ISL

    Time frame: Predose and at designated timepoints up to 24 hours postdose

    Breast milk samples will be collected to calculate the theoretical daily (24 hour) infant dose of ISL relative to the maternal dose.

Secondary outcomes

  1. Area Under the Concentration-Time Curve From 0 to 24 Hours (AUC0-24hrs) of DOR in Breast Milk

    Time frame: Predose and at designated timepoints up to 24 hours postdose

    Breast milk samples will be collected to determine the AUC0-24hrs of DOR.

  2. Maximum Concentration (Cmax) of DOR in Breast Milk

    Time frame: Predose and at designated timepoints up to 24 hours postdose

    Breast milk samples will be collected to determine the Cmax of DOR.

  3. Time to Maximum Concentration (Tmax) of DOR in Breast Milk

    Time frame: Predose and at designated timepoints up to 24 hours postdose

    Breast milk samples will be collected to determine the Tmax of DOR

  4. AUC0-24hrs of Total ISL in Breast Milk

    Time frame: Predose and at designated timepoints up to 24 hours postdose

    Breast milk samples will be collected to determine the AUC0-24hrs of total ISL.

  5. Cmax of Total ISL in Breast Milk

    Time frame: Predose and at designated timepoints up to 24 hours postdose

    Breast milk samples will be collected to determine the Cmax of total ISL.

  6. Tmax of Total ISL in Breast Milk

    Time frame: Predose and at designated timepoints up to 24 hours postdose

    Breast milk samples will be collected to determine the Tmax of total ISL.

  7. AUC0-24hrs of DOR in Plasma

    Time frame: Predose and at designated timepoints up to 24 hours postdose

    Plasma samples will be collected to determine the AUC0-24hrs of DOR.

  8. Cmax of DOR in Plasma

    Time frame: Predose and at designated timepoints up to 24 hours postdose

    Plasma samples will be collected to determine the Cmax of DOR.

  9. Tmax of DOR in Plasma

    Time frame: Predose and at designated timepoints up to 24 hours postdose

    Plasma samples will be collected to determine the Tmax of DOR.

  10. Concentration at 24 Hours (C24) of DOR in Plasma

    Time frame: Predose and at designated timepoints up to 24 hours postdose

    Plasma samples will be collected to determine the C24 of DOR.

  11. AUC0-24hrs of ISL in Plasma

    Time frame: Predose and at designated timepoints up to 24 hours postdose

    Plasma samples will be collected to determine the AUC0-24hrs of ISL.

  12. Cmax of ISL in Plasma

    Time frame: Predose and at designated timepoints up to 24 hours postdose

    Plasma samples will be collected to determine the Cmax of ISL.

  13. Tmax of ISL in Plasma

    Time frame: Predose and at designated timepoints up to 24 hours postdose

    Plasma samples will be collected to determine the Tmax of ISL.

  14. C24 of ISL in Plasma

    Time frame: Predose and at designated timepoints up to 24 hours postdose

    Plasma samples will be collected to determine the C24 of ISL.

Sponsors and collaborators

Lead sponsor

Merck Sharp & Dohme LLC

Industry

Registry information

Official study title

A Clinical Study to Evaluate the Breast Milk and Plasma Pharmacokinetics of MK-8591A in Healthy Lactating Female Participants

Important dates

Study start
2025
Primary completion
2025
Study completion
2026
First posted
Jul 25, 2025
Registry last updated
Feb 20, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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