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Updated: Aug 28, 2025
Microfluidics in Assessing Platelet Function
Published on: November 8, 2024
Effect of Ado-Trastuzumab Emtansine on Autologous Platelet Kinetics and Function
Ali M Ansary1, Moritz Stolla2,3, Jill Corson3
1Clinical Research Division, Fred Hutchinson Cancer Center, Seattle, WA.
Purpose:
Ado-trastuzumab emtansine (T-DM1) treatment results in grade 3-4 thrombocytopenia in 8%-13% of patients. Prior in vitro studies reported T-DM1 inhibition of megakaryocyte maturation as the cause of decreased platelet production. The current observational study was initiated to evaluate causes of thrombocytopenia in patients with metastatic breast cancer.
Materials And Methods:
Patients with human epidermal growth factor receptor 2-positive metastatic breast cancer (N = 11) were enrolled in this postmarket safety study. 111-Indium- radiolabeled autologous platelet recoveries and survivals as well as serial platelet counts, bleeding time assays, and platelet aggregation responses to a wide range of agonists were performed at baseline (BL) and during two consecutive cycles of the drug (3.6 mg/kg IV once every 3 weeks).
Results:
Platelet nadirs occurred earlier in cycle 2 than in cycle 1. Average nadir counts (% BL) in cycles 1 and 2 were 116,000/µL (53% ± 6%) and 115,000/µL (51% ± 9%), respectively, with return to BL by D15 in both cycles. BL platelet survival averaged 8.8 (± 0.3) days but progressively shortened to 5.5 (± 0.5) days during cycle 1 and to 4.6 (± 0.3) days during cycle 2 (P < .001 compared with BL for both cycles). Aggregation responses to all agonists decreased during the study, both in cycle 1 and cycle 2.
Conclusion:
Following T-DM1 administration, we observed statistically significant progressive decreases in platelet survivals and decreased platelet function from BL values. In distinction to published in vitro studies, these unexpected results indicate a direct toxic effect of T-DM1 on patients' autologous circulating platelets.
Insights
Ado-trastuzumab emtansine (T-DM1) treatment causes thrombocytopenia by directly harming platelets, not just by reducing production. This study found T-DM1 significantly shortens platelet survival and impairs function in patients.
Area of Science:
- Oncology
- Pharmacology
- Hematology
Background:
- Ado-trastuzumab emtansine (T-DM1) is associated with significant thrombocytopenia in patients with metastatic breast cancer.
- Previous in vitro studies suggested T-DM1 impairs megakaryocyte maturation, leading to reduced platelet production.
Purpose of the Study:
- To investigate the underlying causes of thrombocytopenia in patients receiving T-DM1 for metastatic breast cancer.
- To evaluate the direct effects of T-DM1 on platelet production, survival, and function in vivo.
Main Methods:
- An observational study involving 11 patients with HER2-positive metastatic breast cancer.
- Assessment of autologous platelet recovery and survival using 111-Indium labeling, serial platelet counts, bleeding time, and platelet aggregation.
- Measurements were taken at baseline and during two cycles of T-DM1 treatment.
Main Results:
- Platelet nadirs were observed in both cycles, with average counts around 51-53% of baseline.
- Platelet survival significantly decreased from a baseline of 8.8 days to 5.5 days in cycle 1 and 4.6 days in cycle 2 (P < .001).
- Platelet aggregation responses to various agonists were reduced during T-DM1 treatment.
Conclusions:
- T-DM1 administration leads to a statistically significant decrease in platelet survival and function.
- Contrary to in vitro findings, these in vivo results suggest a direct toxic effect of T-DM1 on circulating platelets.
