Key Findings
Eleven out of 60 (18%) evaluable patients experienced tumor shrinkage, and 41 (68%) achieved clinical benefit (having at least stable disease). Nearly all the patients who responded to the treatment had elevated levels of DLL3 in their tumor.
Among the 26 patients with the highest levels of DLL3 in the tumor, 10 (39%) responded to the ADC, and had a median overall survival of 5.8 months and a 1-year survival of 32%. Within this group of patients, the 12 patients who were receiving the ADC as third-line therapy responded particularly well, with 50% having tumor shrinkage (confirmed objective response).
The most common severe treatment-related toxicities included serosal effusion (fluid build-up around the heart or lungs), low platelet counts, and skin reactions. These adverse effects appeared generally to be manageable with medications, or resolved without specific interventions.
Next Steps
The findings of this early-stage trial will need to be confirmed in larger clinical trials. A single-arm phase II pivotal trial in patients with DLL3-positive SCLC that has worsened despite at least two prior therapies was launched earlier this year. Other upcoming trials will evaluate rovalpituzumab tesirine in first line SCLC and other DLL3-expressing neuroendocrine cancers.
About Antibody-Drug Conjugates
Antibody-drug conjugates (ADCs) are large molecules in which anticancer drugs are attached to an antibody. The antibody targets a protein that is abundant on the surface of cancer cells, but is preferably rarely found on healthy cells.