Trastuzumab Deruxtecan Is Active in Desmoplastic Small Round Cell Tumor
Investigators used an antibody drug conjugate (ADC) called fam-trastuzumab deruxtecan (T-DXd), in which an antibody to HER2 (trastuzumab) is chemically linked to an inhibitor of a protein called topoisomerase (deruxtecan) which can kill the tumor cells. The ADC allows the deruxtecan to be targeted to the tumor increasing the concentration in the tumor while decreasing the side effects to the patient.
In this small study, the tumors of 19 DSRCT patients with DSRCT were tested by two method for HER2 expression when possible and received off-label T-DXd. Results indicate that 9 of 17 patients with measurable disease had a partial response by RECIST criteria and the other 8 patients had stable disease. However, the responses did not correlate with either of the HER2 test results indicating that these tests are not a good biomarker for response to this drug. These data are early and additional studies are needed and underway, but they indicate that TDXd may be a viable option for treatment in DSRCT.