Serum Concentration of Trastuzumab Deruxtecan (T-DXd), Total Anti-Human Epidermal Growth Factor Receptor 2 Antibody and MAAA-1181a
Study of Trastuzumab Deruxtecan (T-DXd) vs Investigator's Choice Chemotherapy in HER2-low, Hormone Receptor Positive, Metastatic Breast Cancer · Source last updated 2026-03-04
Results reported by the registry submitting party. Population, time horizon, units and missing values must be read together.
Measure
MEAN
Unit
micrograms per milliliter (mcg/mL)
Interval / dispersion
Standard Deviation
Time frame
Pre-dose on Day 1 of Cycles 1, 2, 4, 6 and 8; 15 minutes post-dose on Day 1 of Cycles 1, 2 and 4; and 5 hours post-dose on Day 1 of Cycle 1 (each cycle is 21 days)
What was measured
Blood samples were collected at indicated time points to determine the concentration of T-DXd, total anti-HER2 antibody and MAAA-1181a in serum.
Analysis population: The Pharmacokinetic population included all participants who received at least 1 dose of T-DXd per the protocol for whom any post-dose data were available. Only participants with data collected in specified timepoints are reported.
Groups in this outcome
T-DXd
Participants received T-DXd 5.4 mg/kg via IV infusion every 3 weeks until PD, unacceptable toxicity, withdrawal of consent, or another criterion for discontinuation was met.
Group identifiers and denominators belong to this outcome only. They may differ in another outcome or in safety reporting.
Analysis denominator · Participants
Group
Source count
T-DXd
407
Reported measurements
T-DXd: Day 1: pre-dose, Cycle 1
Analysis denominator · Participants
Group
Source count
T-DXd
5
Values in micrograms per milliliter (mcg/mL) · Interval/dispersion: Standard Deviation
Group
Value
Spread
Lower
Upper
Comment
T-DXd
NA
NA
Not reported
Not reported
NA indicated that mean and standard deviation (SD) were not estimable as the values were below the lower limit of quantification (LLOQ). LLOQ was 0.4 mcg/mL.
T-DXd: Day 1: pre-dose, Cycle 2
Analysis denominator · Participants
Group
Source count
T-DXd
402
Values in micrograms per milliliter (mcg/mL) · Interval/dispersion: Standard Deviation
Group
Value
Spread
Lower
Upper
Comment
T-DXd
4.35225
8.958729
Not reported
Not reported
Not reported
T-DXd: Day 1: pre-dose, Cycle 4
Analysis denominator · Participants
Group
Source count
T-DXd
374
Values in micrograms per milliliter (mcg/mL) · Interval/dispersion: Standard Deviation
Group
Value
Spread
Lower
Upper
Comment
T-DXd
8.21037
9.464435
Not reported
Not reported
Not reported
T-DXd: Day 1: pre-dose, Cycle 6
Analysis denominator · Participants
Group
Source count
T-DXd
336
Values in micrograms per milliliter (mcg/mL) · Interval/dispersion: Standard Deviation
Group
Value
Spread
Lower
Upper
Comment
T-DXd
8.65950
4.753592
Not reported
Not reported
Not reported
T-DXd: Day 1: pre-dose, Cycle 8
Analysis denominator · Participants
Group
Source count
T-DXd
304
Values in micrograms per milliliter (mcg/mL) · Interval/dispersion: Standard Deviation
Group
Value
Spread
Lower
Upper
Comment
T-DXd
11.31496
22.894112
Not reported
Not reported
Not reported
T-DXd: Day 1: 15 minutes post-dose, Cycle 1
Analysis denominator · Participants
Group
Source count
T-DXd
367
Values in micrograms per milliliter (mcg/mL) · Interval/dispersion: Standard Deviation
Group
Value
Spread
Lower
Upper
Comment
T-DXd
135.90160
102.989325
Not reported
Not reported
Not reported
T-DXd: Day 1: 15 minutes post-dose, Cycle 2
Analysis denominator · Participants
Group
Source count
T-DXd
378
Values in micrograms per milliliter (mcg/mL) · Interval/dispersion: Standard Deviation
Group
Value
Spread
Lower
Upper
Comment
T-DXd
136.74872
108.860006
Not reported
Not reported
Not reported
T-DXd: Day 1: 15 minutes post-dose, Cycle 4
Analysis denominator · Participants
Group
Source count
T-DXd
347
Values in micrograms per milliliter (mcg/mL) · Interval/dispersion: Standard Deviation
Group
Value
Spread
Lower
Upper
Comment
T-DXd
124.60481
39.812165
Not reported
Not reported
Not reported
T-DXd: Day 1: 5 hours post-dose, Cycle 1
Analysis denominator · Participants
Group
Source count
T-DXd
366
Values in micrograms per milliliter (mcg/mL) · Interval/dispersion: Standard Deviation
Group
Value
Spread
Lower
Upper
Comment
T-DXd
123.82288
30.513998
Not reported
Not reported
Not reported
Total anti-HER2 antibody: Day 1: pre-dose, Cycle 1
Analysis denominator · Participants
Group
Source count
T-DXd
3
Values in micrograms per milliliter (mcg/mL) · Interval/dispersion: Standard Deviation
Group
Value
Spread
Lower
Upper
Comment
T-DXd
NA
NA
Not reported
Not reported
NA indicated that mean and SD were not estimable as the values were below the LLOQ. LLOQ was 0.4 mcg/mL.
Total anti-HER2 antibody: Day 1: pre-dose, Cycle 2
Analysis denominator · Participants
Group
Source count
T-DXd
390
Values in micrograms per milliliter (mcg/mL) · Interval/dispersion: Standard Deviation
Group
Value
Spread
Lower
Upper
Comment
T-DXd
5.75841
11.351915
Not reported
Not reported
Not reported
Total anti-HER2 antibody: Day 1: pre-dose, Cycle 4
Analysis denominator · Participants
Group
Source count
T-DXd
370
Values in micrograms per milliliter (mcg/mL) · Interval/dispersion: Standard Deviation
Group
Value
Spread
Lower
Upper
Comment
T-DXd
12.00513
11.087226
Not reported
Not reported
Not reported
Total anti-HER2 antibody: Day 1: pre-dose, Cycle 6
Analysis denominator · Participants
Group
Source count
T-DXd
333
Values in micrograms per milliliter (mcg/mL) · Interval/dispersion: Standard Deviation
Group
Value
Spread
Lower
Upper
Comment
T-DXd
13.97891
8.720790
Not reported
Not reported
Not reported
Total anti-HER2 antibody: Day 1: pre-dose, Cycle 8
Analysis denominator · Participants
Group
Source count
T-DXd
302
Values in micrograms per milliliter (mcg/mL) · Interval/dispersion: Standard Deviation
Group
Value
Spread
Lower
Upper
Comment
T-DXd
17.47641
27.144299
Not reported
Not reported
Not reported
Total anti-HER2 antibody: Day 1: 15 minutes post-dose, Cycle 1
Analysis denominator · Participants
Group
Source count
T-DXd
367
Values in micrograms per milliliter (mcg/mL) · Interval/dispersion: Standard Deviation
Group
Value
Spread
Lower
Upper
Comment
T-DXd
141.27586
114.137606
Not reported
Not reported
Not reported
Total anti-HER2 antibody: Day 1: 15 minutes post-dose, Cycle 2
Analysis denominator · Participants
Group
Source count
T-DXd
377
Values in micrograms per milliliter (mcg/mL) · Interval/dispersion: Standard Deviation
Group
Value
Spread
Lower
Upper
Comment
T-DXd
146.17993
134.780719
Not reported
Not reported
Not reported
Total anti-HER2 antibody: Day 1: 15 minutes post-dose, Cycle 4
Analysis denominator · Participants
Group
Source count
T-DXd
345
Values in micrograms per milliliter (mcg/mL) · Interval/dispersion: Standard Deviation
Group
Value
Spread
Lower
Upper
Comment
T-DXd
131.06830
44.228380
Not reported
Not reported
Not reported
Total anti-HER2 antibody: Day 1: 5 hours post-dose, Cycle 1
Analysis denominator · Participants
Group
Source count
T-DXd
363
Values in micrograms per milliliter (mcg/mL) · Interval/dispersion: Standard Deviation
Group
Value
Spread
Lower
Upper
Comment
T-DXd
119.64619
26.591288
Not reported
Not reported
Not reported
MAAA-1181a: Day 1: pre-dose, Cycle 1
Analysis denominator · Participants
Group
Source count
T-DXd
3
Values in micrograms per milliliter (mcg/mL) · Interval/dispersion: Standard Deviation
Group
Value
Spread
Lower
Upper
Comment
T-DXd
NA
NA
Not reported
Not reported
NA indicated that mean and SD were not estimable as the values were below the LLOQ. LLOQ was 0.00001 mcg/mL.
MAAA-1181a: Day 1: pre-dose, Cycle 2
Analysis denominator · Participants
Group
Source count
T-DXd
407
Values in micrograms per milliliter (mcg/mL) · Interval/dispersion: Standard Deviation
Group
Value
Spread
Lower
Upper
Comment
T-DXd
0.261850
0.2096642
Not reported
Not reported
Not reported
MAAA-1181a: Day 1: pre-dose, Cycle 4
Analysis denominator · Participants
Group
Source count
T-DXd
380
Values in micrograms per milliliter (mcg/mL) · Interval/dispersion: Standard Deviation
Group
Value
Spread
Lower
Upper
Comment
T-DXd
0.401004
0.2825761
Not reported
Not reported
Not reported
MAAA-1181a: Day 1: pre-dose, Cycle 6
Analysis denominator · Participants
Group
Source count
T-DXd
336
Values in micrograms per milliliter (mcg/mL) · Interval/dispersion: Standard Deviation
Group
Value
Spread
Lower
Upper
Comment
T-DXd
0.446237
0.2957478
Not reported
Not reported
Not reported
MAAA-1181a: Day 1: pre-dose, Cycle 8
Analysis denominator · Participants
Group
Source count
T-DXd
307
Values in micrograms per milliliter (mcg/mL) · Interval/dispersion: Standard Deviation
Group
Value
Spread
Lower
Upper
Comment
T-DXd
0.432894
0.2819292
Not reported
Not reported
Not reported
MAAA-1181a: Day 1: 15 minutes post-dose, Cycle 1
Analysis denominator · Participants
Group
Source count
T-DXd
367
Values in micrograms per milliliter (mcg/mL) · Interval/dispersion: Standard Deviation
Group
Value
Spread
Lower
Upper
Comment
T-DXd
6.014366
3.1859583
Not reported
Not reported
Not reported
MAAA-1181a: Day 1: 15 minutes post-dose, Cycle 2
Analysis denominator · Participants
Group
Source count
T-DXd
376
Values in micrograms per milliliter (mcg/mL) · Interval/dispersion: Standard Deviation
Group
Value
Spread
Lower
Upper
Comment
T-DXd
2.985606
1.9276120
Not reported
Not reported
Not reported
MAAA-1181a: Day 1: 15 minutes post-dose, Cycle 4
Analysis denominator · Participants
Group
Source count
T-DXd
348
Values in micrograms per milliliter (mcg/mL) · Interval/dispersion: Standard Deviation
Group
Value
Spread
Lower
Upper
Comment
T-DXd
2.411409
1.5862547
Not reported
Not reported
Not reported
MAAA-1181a: Day 1: 5 hours post-dose, Cycle 1
Analysis denominator · Participants
Group
Source count
T-DXd
363
Values in micrograms per milliliter (mcg/mL) · Interval/dispersion: Standard Deviation
Group
Value
Spread
Lower
Upper
Comment
T-DXd
13.917874
6.5178612
Not reported
Not reported
Not reported
Complete source fields
classes
categories
measurements
comment
NA indicated that mean and standard deviation (SD) were not estimable as the values were below the lower limit of quantification (LLOQ). LLOQ was 0.4 mcg/mL.
group Id
OG000
spread
NA
value
NA
denoms
counts
group Id
OG000
value
5
units
Participants
title
T-DXd: Day 1: pre-dose, Cycle 1
categories
measurements
group Id
OG000
spread
8.958729
value
4.35225
denoms
counts
group Id
OG000
value
402
units
Participants
title
T-DXd: Day 1: pre-dose, Cycle 2
categories
measurements
group Id
OG000
spread
9.464435
value
8.21037
denoms
counts
group Id
OG000
value
374
units
Participants
title
T-DXd: Day 1: pre-dose, Cycle 4
categories
measurements
group Id
OG000
spread
4.753592
value
8.65950
denoms
counts
group Id
OG000
value
336
units
Participants
title
T-DXd: Day 1: pre-dose, Cycle 6
categories
measurements
group Id
OG000
spread
22.894112
value
11.31496
denoms
counts
group Id
OG000
value
304
units
Participants
title
T-DXd: Day 1: pre-dose, Cycle 8
categories
measurements
group Id
OG000
spread
102.989325
value
135.90160
denoms
counts
group Id
OG000
value
367
units
Participants
title
T-DXd: Day 1: 15 minutes post-dose, Cycle 1
categories
measurements
group Id
OG000
spread
108.860006
value
136.74872
denoms
counts
group Id
OG000
value
378
units
Participants
title
T-DXd: Day 1: 15 minutes post-dose, Cycle 2
categories
measurements
group Id
OG000
spread
39.812165
value
124.60481
denoms
counts
group Id
OG000
value
347
units
Participants
title
T-DXd: Day 1: 15 minutes post-dose, Cycle 4
categories
measurements
group Id
OG000
spread
30.513998
value
123.82288
denoms
counts
group Id
OG000
value
366
units
Participants
title
T-DXd: Day 1: 5 hours post-dose, Cycle 1
categories
measurements
comment
NA indicated that mean and SD were not estimable as the values were below the LLOQ. LLOQ was 0.4 mcg/mL.
group Id
OG000
spread
NA
value
NA
denoms
counts
group Id
OG000
value
3
units
Participants
title
Total anti-HER2 antibody: Day 1: pre-dose, Cycle 1
categories
measurements
group Id
OG000
spread
11.351915
value
5.75841
denoms
counts
group Id
OG000
value
390
units
Participants
title
Total anti-HER2 antibody: Day 1: pre-dose, Cycle 2
categories
measurements
group Id
OG000
spread
11.087226
value
12.00513
denoms
counts
group Id
OG000
value
370
units
Participants
title
Total anti-HER2 antibody: Day 1: pre-dose, Cycle 4
denoms
counts
group Id
OG000
value
407
units
Participants
description
Blood samples were collected at indicated time points to determine the concentration of T-DXd, total anti-HER2 antibody and MAAA-1181a in serum.
dispersion Type
Standard Deviation
groups
description
Participants received T-DXd 5.4 mg/kg via IV infusion every 3 weeks until PD, unacceptable toxicity, withdrawal of consent, or another criterion for discontinuation was met.
id
OG000
title
T-DXd
param Type
MEAN
population Description
The Pharmacokinetic population included all participants who received at least 1 dose of T-DXd per the protocol for whom any post-dose data were available. Only participants with data collected in specified timepoints are reported.
reporting Status
POSTED
time Frame
Pre-dose on Day 1 of Cycles 1, 2, 4, 6 and 8; 15 minutes post-dose on Day 1 of Cycles 1, 2 and 4; and 5 hours post-dose on Day 1 of Cycle 1 (each cycle is 21 days)
title
Serum Concentration of Trastuzumab Deruxtecan (T-DXd), Total Anti-Human Epidermal Growth Factor Receptor 2 Antibody and MAAA-1181a
Triangle