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 Type
INTERVENTIONAL
Allocation
NA
Purpose
OTHER
Masking
NONE
Enrollment
8
nirmatrelvir/ritonavir
nirmatrelvir/ritonavir
Pfizer Clinical Research Unit - Brussels
Brussels, Bruxelles-capitale, Région de, Belgium
Maximum Breastmilk Concentration (Cmax) of nirmatrelvir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Time to Reach Maximum Breastmilk Concentration (Tmax) of nirmatrelvir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Area under the breastmilk concentration time profile from time 0 to the time of the end of the dosing interval (tau) of nirmatrelvir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Terminal phase half life (t½) of nirmatrelvir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Average breastmilk concentration (Cav) of nirmatrelvir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Amount excreted in breast milk over the dosing interval (Aetau) of nirmatrelvir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Percent of dose excreted in breast milk during the dosing interval (Aetau %) of nirmatrelvir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Breast milk clearance (CLbm) of nirmatrelvir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Cmax of ritonavir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Tmax of ritonavir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Area under the breastmilk concentration time profile from time 0 to the time of the end of the dosing interval (Auc tau) of ritonavir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
t½ of ritonavir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Cav of ritonavir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Aetau of ritonavir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Aetau % of ritonavir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
CLbm of ritonavir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Cmax of nirmatrelvir and ritonavir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Cav of nirmatrelvir and ritonavir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Pre-dose concentration (Ctrough) of nirmatrelvir and ritonavir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Tmax of nirmatrelvir and ritonavir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
AUC tau of nirmatrelvir and ritonavir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Minimum Observed Breastmilk Concentration (Cmin) of nirmatrelvir and ritonavir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
t½ of nirmatrelvir and ritonavir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Apparent plasma clearance (CL/F) of nirmatrelvir and ritonavir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Apparent volume of distribution (Vz/F) of nirmatrelvir and ritonavir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Daily (24 hour) amount of nirmatrelvir excreted in breast milk (Ae 24bm)
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Breast milk to plasma ratio for AUC tau (MPAUC tau) for both nirmatrelvir and ritonavir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Breast milk to plasma ratio for AUC tau (MPCmax during dosing interval tau) for both nirmatrelvir and ritonavir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
CLbm for both nirmatrelvir and ritonavir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Milk to plasma ratio (M/P) of both nirmatrelvir and ritonavir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Body weight normalized infant dose in μg/kg/day (BWNID) of both nirmatrelvir and ritonavir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Body weight normalized maternal dose in μg/kg/day (BWNMD) of both nirmatrelvir and ritonavir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Infant dose expressed as % of body weight normalized maternal dose (BWNIDPCM) of both nirmatrelvir and ritonavir
Time frame: Day 2 (0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 hours) and Day 3 (18, 24, 32, 40 hours) Day 4 (48 hours)
Participants reporting treatment emergent adverse events
Time frame: Baseline to 28 days after last dose
Participants reporting abnormal clinical laboratory lab tests
Time frame: Baseline to 28 days after last dose
Participants reporting abnormal vital signs
Time frame: Baseline to 28 days after last dose
Participants reporting abnormal physical examination results
Time frame: Baseline to 28 days after last dose
Participants reporting abnormal electrocardiograms
Time frame: Baseline to 28 days after last dose
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