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

NCT05441215 · Status: COMPLETED · Phase: PHASE1 · Type: INTERVENTIONAL · Enrollment: 8

Last updated 2026-05-01

Study results available
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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

Interventions

DRUG

nirmatrelvir

nirmatrelvir/ritonavir

DRUG

ritonavir

nirmatrelvir/ritonavir

Sponsors & Collaborators

Principal Investigators

  • Pfizer CT.gov Call Center · Pfizer

Study Design

Allocation
NA
Purpose
OTHER
Masking
NONE
Model
SINGLE_GROUP

Eligibility

Min Age
18 Years
Max Age
55 Years
Sex
FEMALE
Healthy Volunteers
Yes

Timeline & Regulatory

Start
2022-12-12
Primary Completion
2023-12-15
Completion
2023-12-15
FDA Drug
Yes

Countries

  • Belgium

Study Locations

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Entities

Companies

Read the full study record

This page highlights key information. For complete eligibility criteria, study locations, investigator contacts, and the full protocol, visit the original record on ClinicalTrials.gov.

View NCT05441215 on ClinicalTrials.gov