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

NCT05441215 | Completed Phase 1 Results FDA Drug

• 2 other identifiers: C46710392022-001020-15
• Study Type: interventional
• Target: 8
• Locations: 1 country
• Sites: 1

Brief Summary

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.

Conditions

Healthy Participants

Keywords

Severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2); Lactation; COVID-19; Breastfeeding; Protease Inhibitor

Outcome Measures

Primary Outcomes (8)

• The Maximum Observed Concentration of Nirmatrelvir in Breast Milk Over the Dosing Interval

  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

  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

  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

  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

  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

  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

  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

  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 Outcomes (41)

• The Maximum Observed Concentration of Ritonavir in Breast Milk 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

• Time to Reach Cmax 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

  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

  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

  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

Study Arms (1)

nirmatrelvir/ritonavir

EXPERIMENTAL

nirmatrelvir/ritonavir will be given by mouth two times a day as a tablet

Drug: nirmatrelvir; Drug: ritonavir

Interventions

nirmatrelvir DRUG

nirmatrelvir/ritonavir

Also known as: PF-07321332/ritonavir

nirmatrelvir/ritonavir

ritonavir DRUG

nirmatrelvir/ritonavir

Also known as: PF-07321332/ritonavir

nirmatrelvir/ritonavir

Eligibility Criteria

• Age: 18 Years - 55 Years
• Gender Eligibility Details: Healthy lactating women
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• 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

You may not qualify if:

• 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

Sponsors & Collaborators

• Pfizer: lead

Study Sites (1)

Pfizer Clinical Research Unit - Brussels

Brussels, Bruxelles-capitale, Région de, B-1070, Belgium

Location

Related Links

• To obtain contact information for a study center near you, click here.

MeSH Terms

Conditions

Breast Feeding; COVID-19

Interventions

nirmatrelvir; nirmatrelvir and ritonavir drug combination; Ritonavir

Condition Hierarchy (Ancestors)

Feeding Behavior; Behavior; Pneumonia, Viral; Pneumonia; Respiratory Tract Infections; Infections; Virus Diseases; Coronavirus Infections; Coronaviridae Infections; Nidovirales Infections; RNA Virus Infections; Lung Diseases; Respiratory Tract Diseases

Intervention Hierarchy (Ancestors)

Thiazoles; Sulfur Compounds; Organic Chemicals; Azoles; Heterocyclic Compounds, 1-Ring; Heterocyclic Compounds

Results Point of Contact

• Title: Pfizer ClinicalTrials.gov Call Center
• Organization: Pfizer, Inc.

ClinicalTrials.gov_Inquiries@pfizer.com

1-800-718-1021

Study Officials

• Pfizer CT.gov Call Center

  Pfizer

  STUDY DIRECTOR

Publication Agreements

• PI is Sponsor Employee: Yes
• Restriction Type: OTHER
• Restrictive Agreement: Yes

Study Design

• Study Type: interventional
• Phase: phase 1
• Allocation: NA
• Masking: NONE
• Purpose: OTHER
• Intervention Model: SINGLE GROUP
• Sponsor Type: INDUSTRY
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: June 28, 2022
• First Posted: July 1, 2022
• Study Start: December 12, 2022
• Primary Completion: December 15, 2023
• Study Completion: December 15, 2023
• Last Updated: May 1, 2026
• Results First Posted: May 1, 2026

Record last verified: 2026-04

Data Sharing

• IPD Sharing: Will not share

Locations

BE (1)