A Study to Learn About the Medicine (PF-07321332 or Nirmatrelvir/Ritonavir) in Healthy Lactating Women

April 28, 2026 updated by: Pfizer

A PHASE I, MULTIPLE DOSE, OPEN-LABEL PHARMACOKINETIC STUDY OF NIRMATRELVIR/RITONAVIR IN HEALTHY LACTATING WOMEN

The main purpose of this study is to measure the level of active ingredient of the study medicine (nirmatrelvir) that is secreted in human breast milk when it is given to healthy breastfeeding women. The study medicine consists of two medicines, nirmatrelvir and ritonavir. We are seeking female participants who are:

  • Actively breast-feeding (lactating) at least 12 weeks postpartum;
  • Age between 18 to 55 years and not currently pregnant;
  • Have a Body Mass Index (BMI): 17.5 kg/m2; and a total body weight >50 kg (110 lb).

Participants will take the study medicine by mouth for a total of 3 times over 2 days (2 morning doses and 1 evening dose) at the study clinic. We will periodically collect breast milk from day 2 to 4 to measure the level of nirmatrelvir and ritonavir in it. A safety follow up call will be conducted around 28-35 days from the last dose to monitor any reactions participants may have to the study medicine.

Study Overview

Status

Completed

Study Type

Interventional

Enrollment (Actual)

8

Phase

  • Phase 1

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

    • Bruxelles-capitale, Région de
      • Brussels, Bruxelles-capitale, Région de, Belgium, B-1070
        • Pfizer Clinical Research Unit - Brussels

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years to 55 years (Adult)

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • Healthy lactating females who are actively breast-feeding or expressing breast milk, at least 12 weeks post-partum and not currently pregnant between 18 and 55 years old
  • Body Mass Index (BMI): 17.5 kg/m2; and a total body weight >50 kg (110 lb)
  • Infants of women enrolled in the study must be able to feed successfully from a bottle or other age-appropriate alternative feeding method prior to the start of the study and must be able to tolerate infant formula if the mother does not have a supply of stored breast milk sufficient to cover the duration of the study
  • Participants must be willing to temporarily discontinue breast feeding their infants for a total of 4.5 days (108 hours)
  • Participants must be willing to regularly pump breasts throughout the study and express milk according to a schedule designed to maintain lactation throughout the study period

Exclusion Criteria:

  • Positive test result (RT-PCR) for SARS-CoV-2 infection at the time of screening or Day -1
  • Evidence or history of clinically significant findings
  • History of febrile illness or mastitis within 5 days prior to the first dose of study medication
  • Participants who have received a COVID-19 vaccine within 7 days before screening or admission, or who are to be vaccinated with a COVID-19 vaccine at any time during the study confinement period
  • History of HIV infection, hepatitis B, or hepatitis C; positive testing for HIV, HBsAg, or HCVAb. Hepatitis B vaccination is allowed
  • Abnormal vital signs such as blood pressure, 12-lead electrocardiogram
  • History of alcohol abuse and/or illicit drug use, tobacco use in excess of 5 cigarettes/day or 2 chews/day
  • Blood donation within 60 days

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Other
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: nirmatrelvir/ritonavir
nirmatrelvir/ritonavir will be given by mouth two times a day as a tablet
nirmatrelvir/ritonavir
Other Names:
  • PF-07321332/ritonavir
nirmatrelvir/ritonavir
Other Names:
  • PF-07321332/ritonavir

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
The Maximum Observed Concentration of Nirmatrelvir in Breast Milk Over the Dosing Interval
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
The maximum observed concentration and was directly observed from data.
At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
Time to Reach Cmax of Nirmatrelvir in Breast Milk
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
Cmax was defined as maximum observed concentration of nirmatrelvir in breast milk.
At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
Area Under the Concentration-Time Profile From Time Zero to End of Dosing Interval for Nirmatrelvir in Breast Milk
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
Area under the concentration curve for nirmatrelvir in breast milk from time 0 to end of dosing interval.
At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
Terminal Half-Life of Nirmatrelvir in Breast Milk
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
The time measured for the breast milk nirmatrelvir concentration to decrease by one half.
At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
The Average Steady State Concentration of Nirmatrelvir in Breast Milk
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
The average concentration across time and can be calculated by dividing AUCtau by time. AUCtau was defined area under the concentration curve from time 0 to end of dosing interval.
At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
The Amount of Nirmatrelvir Excreted in Breast Milk Over the Dosing Interval Tau
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
The amount of nirmatrelvir excreted into breast milk over the dosing interval.
At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
The Percent of Amount of Nirmatrelvir Excreted in Breast Milk Over The Dosing Interval Tau
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
The percent of nirmatelvir excreted in breast milk to amount of breast milk over the dosing interval .
At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
Breast Milk Clearance of Nirmatrelvir
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
Clearance was defined as the apparent volume (Liter) of breast milk completely cleared the nirmatrelvir per hour.
At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
The Maximum Observed Concentration of Ritonavir in Breast Milk Observed Over the Dosing Interval
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
The maximum observed concentration and was directly observed from data.
At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
Time to Reach Cmax of Ritonavir in Breast Milk
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
Cmax was defined as maximum observed concentration of ritonavir in breast milk.
At Day -1 (24 Hours Prior to Dosing on Day 1), 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
Area Under the Concentration-Time Profile for Ritonavir in Breast Milk From Time Zero to End of Dosing Interval
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
Area under the concentration curve for ritonavir in breast milk from time 0 to end of dosing interval.
At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
Half-Life of Ritonavir in Breast Milk
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
The time measured for the breast milk ritonavir concentration to decrease by one half.
At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
The Average Steady State Concentration of Ritonavir in Breast Milk
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
The average concentration across time and can be calculated by dividing AUCtau by time. AUCtau was defined area under the concentration curve from time 0 to end of dosing interval.
At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
The Amount of Ritonavir Excreted in Breast Milk Over the Dosing Interval Tau
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
The amount of ritonavir excreted into breast milk over the dosing interval.
At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
The Percent of Ritonavir Excreted in Breast Milk Over The Dosing Interval Tau
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
The percent of ritonavir excreted in breast milk to amount of breast milk over the dosing interval.
At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
Breast Milk Clearance of Ritonavir
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
Clearance was defined as the apparent volume (L) of breast milk completely cleared the ritonavir per hour.
At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
The Maximum Observed Concentration of Nirmatrelvir in Plasma Observed Over the Dosing Interval
Time Frame: At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
The maximum observed concentration and was directly observed from data.
At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
The Maximum Observed Concentration of Ritonavir in Plasma Observed Over the Dosing Interval
Time Frame: At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
The maximum observed concentration and was directly observed from data.
At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
Area Under the Concentration-Time Profile for Nirmatrelvir in Plasma From Time Zero to End of Dosing Interval
Time Frame: At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
Area under the concentration curve for nirmatrelvir in breast milk from time 0 to end of dosing interval.
At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
Area Under the Concentration-Time Profile for Ritonavir in Plasma From Time Zero to End of Dosing Interval
Time Frame: At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
Area under the concentration curve for ritonavir in plasma from time 0 to end of dosing interval.
At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
Half-Life of Nirmatrelvir in Plasma
Time Frame: At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
The time measured for the plasma nirmatrelvir concentration to decrease by one half.
At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
Half-Life of Ritonavir in Plasma
Time Frame: At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
The time measured for the plasma ritonavir concentration to decrease by one half.
At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
The Minimum Plasma Concentration of Nirmatrelvir Observed Over the Dosing Interval
Time Frame: At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
The minimum observed concentration and was directly observed from data.
At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
The Minimum Plasma Concentration of Ritonavir Observed Over the Dosing Interval
Time Frame: At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
The minimum observed concentration and was directly observed from data.
At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
Time to Reach Cmax of Nirmatrelvir in Plasma
Time Frame: At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
Cmax was defined as maximum observed concentration of nirmatrelvir in plasma.
At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
Time to Reach Cmax of Ritonavir in Plasma
Time Frame: At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
Cmax was defined as maximum observed concentration of ritonavir in plasma.
At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
Apparent Clearance of Nirmatrelvir From Plasma
Time Frame: At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
Clearance was defined as the apparent volume (L) of plasma completely cleared the nirmatrelvir per hour.
At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
Apparent Clearance of Ritonavir From Plasma
Time Frame: At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
Clearance was defined as the apparent volume (L) of plasma completely cleared the ritonavir per hour.
At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
Apparent Volume of Nirmatrelvir Distribution
Time Frame: At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
Volume of distribution was defined as the theoretical volume in which the total amount of drug would need to be uniformly distributed to produce the desired plasma concentration of a drug. Apparent volume of distribution after oral dose was influenced by the fraction absorbed.
At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
Apparent Volume of Ritonavir Distribution
Time Frame: At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
Volume of distribution was defined as the theoretical volume in which the total amount of drug would need to be uniformly distributed to produce the desired plasma concentration of a drug. Apparent volume of distribution after oral dose was influenced by the fraction absorbed.
At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
The Average Steady State Concentration of Nirmatrelvir in Plasma
Time Frame: At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
The average concentration across time and can be calculated by dividing AUCtau by time. AUCtau was defined area under the concentration curve from time 0 to end of dosing interval.
At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
The Average Steady State Concentration of Ritonavir in Plasma
Time Frame: At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
The average concentration across time and can be calculated by dividing AUCtau by time. AUCtau was defined area under the concentration curve from time 0 to end of dosing interval.
At 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 32, 40, 48 Hours Post Dose on Day 2
Daily (24 Hour) Amount of Nirmatrelvir Excreted in Breast Milk
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
Amount of nirmatrelvir excreted in breast milk in 24 hours.
At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
Daily (24 Hour) Amount of Ritonavir Excreted in Breast Milk
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
Amount of ritonavir excreted in breast milk in 24 hours.
At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
Milk to Plasma Ratio of Nirmatrelvir for AUCtau During Dosing Interval
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
The ratio of area under the concentration-time profile for nirmatrelvir in milk to those in plasma from time zero to end of dosing interval.
At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
Milk to Plasma Ratio of Ritonavir for AUCtau During Dosing Interval
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
The ratio of area under the concentration-time profile for ritonavir in milk to those in plasma from time zero to end of dosing interval.
At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
Milk to Plasma Ratio of Nirmatrelvir for Cmax During Dosing Interval
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
The ratio of the maximum concentration of nirmatrelvir in breast milk to those in plasma observed over the dosing interval.
At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
Milk to Plasma Ratio of Ritonavir for Cmax During Dosing Interval
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
The ratio of the maximum concentration of ritonavir in breast milk to those in plasma observed over the dosing interval.
At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
Body Weight Normalized Infant Dose (BWNID) of Nirmatrelvir in mg/kg/Day
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
BWNID = MPAUCtau * Cav * 150 mL/kg/day, where 150 mL/kg/day^2 is the standardized milk consumption for an infant. MPAUCtau: Milk to plasma ratio for AUCtau. Cav: Average concentration.
At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
BWNID of Ritonavir in mg/kg/Day
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
BWNID = MPAUCtau * Cav * 150 mL/kg/day, where 150 mL/kg/day^2 is the standardized milk consumption for an infant. MPAUCtau: Milk to plasma ratio for AUCtau. Cav: Average concentration.
At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
Body Weight Normalized Maternal Dose (BWNMD) of Nirmatrelvir in mg/kg/Day
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
Maternal dose in mg/day (300 mg BID = 600 mg/day for nirmatrelvir and 100 mg BID = 200 mg/day for ritonavir) / maternal weight in kg at screening.
At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
BWNMD of Ritonavir in mg/kg/Day
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
Maternal dose in mg/day (300 mg BID = 600 mg/day for nirmatrelvir and 100 mg BID = 200 mg/day for ritonavir) / maternal weight in kg at screening.
At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
Infant Dose Expressed As % of Body Weight Normalized Maternal Dose (BWNIDPCM) for Nirmatrelvir
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
BWNIDPCM = 100 * BWNID / BWNMD.
At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
BWNIDPCM for Ritonavir
Time Frame: At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
BWNIDPCM = 100 * BWNID / BWNMD.
At Day -1 (24 Hours Prior to Dosing on Day 1), Pre-dose on Day 1, 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 32, 32 to 40 and 40 to 48 Hours Post-dose on Day 2
Number of Participants With Treatment Emergent Adverse Events
Time Frame: From the first dose of study treatment on Day 1 to up to 28 days after the last dose of study intervention on Day 2 (maximum to 30 days)
An adverse event (AE) was any untoward medical occurrence in a participant or clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. AEs might arise from symptoms or other complaints reported to the investigator by the participant (or, when appropriate, by a caregiver, surrogate, or the participant's legally authorized representative), or they might arise from clinical findings of the investigator or other healthcare providers (clinical signs, test results, etc.). TEAEs were those with initial onset or increasing in severity after the first dose of study treatment.
From the first dose of study treatment on Day 1 to up to 28 days after the last dose of study intervention on Day 2 (maximum to 30 days)
Number of Participants With Laboratory Abnormalities (Without Regard to Baseline Abnormality)
Time Frame: At Screening (Day -28 to Day -2), Day -1, and Day 4
The laboratory abnormality parameters included urinalysis: urine bilirubin (>=1), urine hemoglobin (>=1) and leukocyte esterase (>=1).
At Screening (Day -28 to Day -2), Day -1, and Day 4
Number of Participants With Vital Signs Abnormalities
Time Frame: At Screening (Day -28 to Day -2), Pre-dose and 12 Hours post-dose on Day 1, Pre-dose and 48 Hours Post-dose on Day 2
Single supine blood pressure (BP), and pulse rate (PR) were performed following approximately a 5-minute rest in a supine position. BP, and PR assessments will be performed after collection of electrocardiogram (ECGs) and prior to collection of blood draws if scheduled at the same time. Vital signs abnormality included supine systolic BP <90mmHg.
At Screening (Day -28 to Day -2), Pre-dose and 12 Hours post-dose on Day 1, Pre-dose and 48 Hours Post-dose on Day 2
Number of Participants With ECG Abnormalities
Time Frame: At Screening (from Day -28 to Day -2)
Standard 12-lead ECGs utilizing limb leads (with a 10 second rhythm strip) were collected. All ECG assessments were made after at least a 5-minute rest in a supine position and prior to any blood draws or vital sign measurements.
At Screening (from Day -28 to Day -2)
Number of Participants With Physical Examination Abnormalities
Time Frame: At Screening (from Day -28 to Day -2) or Day -1
Physical examination included height, weight and body mass index (BMI, BMI = weight [kg] / height [m^2]) obtained for eligibility criteria. Physical examination abnormalities: BMI <17.5 kg/m^2; and a total body weight <=50 kg (110 lb).
At Screening (from Day -28 to Day -2) or Day -1

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Investigators

  • Study Director: Pfizer CT.gov Call Center, Pfizer

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

December 12, 2022

Primary Completion (Actual)

December 15, 2023

Study Completion (Actual)

December 15, 2023

Study Registration Dates

First Submitted

June 28, 2022

First Submitted That Met QC Criteria

June 28, 2022

First Posted (Actual)

July 1, 2022

Study Record Updates

Last Update Posted (Actual)

May 1, 2026

Last Update Submitted That Met QC Criteria

April 28, 2026

Last Verified

April 1, 2026

More Information

Terms related to this study

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical_trials/trial_data_and_results/data_requests.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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