The estimated mean effective radiation dose was 2.4 rem/mCi, “which is consistent with other zirconium-labeled antibody or minibody technologies,” Dr. Gordon said.
Study subjects ranged in age from 31 to 82 years and included nine men and six women with solid tumor malignancies who were eligible to receive checkpoint inhibitor therapy. Their primary cancer types were melanoma (eight patients), non–small-cell lung cancer (six patients), and hepatocellular carcinoma (one patient).
Two patients had received no prior treatment, three had discontinued prior checkpoint inhibitor therapy, and 10 were on immunotherapy.
No drug-related adverse events occurred during the course of the study, although one patient had a transient increase in anti-drug antibodies, Dr. Gordon said.
“Immunotherapy, and specifically checkpoint inhibitors (CPIs), have transformed the landscape of cancer care. Antitumor activity of CPIs is mediated by the CD8-positive T-cell cytotoxic effects, with preclinical and translational clinical studies demonstrating the importance of activated CD8-positive cells within the tumor microenvironment,” he explained, adding that currently available technology is limited in its ability to continually assess the presence of and change in the CD8 infiltrate; one biopsy may fail to capture the immunologic heterogeneity that exists among various tumors in an individual patient.
“As CPI therapy moves into front-line and earlier settings, the ability to have a noninvasive technology to assess whole body and intratumoral changes in CD8 trafficking or expansion in response to therapy is viewed as being crucial,” he said.
A phase 2 study to look closer at the potential for PET + 89Zr-IAB22M2C to fulfill that role will begin soon. The study will focus on correlating imaging with synchronous biopsies before and after primary immunotherapy to look for any predictive potential for this technology, he said.
This study was supported by ImaginAb and Parker Institute for Cancer Immunotherapy. Dr. Gordon reported having no disclosures.
SOURCE: Gordon M et al., SITC 2018: Abstract LB49.