Mitra AP, Narayan VM, Mokkapati S, et al. - Serum antiadenovirus antibody levels could be a novel predictive marker for nadofaragene firadenovec response durability.

• In a recent phase 3 trial of intravesical nadofaragene firadenovec, a promising complete response rate has been observed for patients with bacillus Calmette-Guérin–unresponsive non–muscle-invasive bladder cancer.

• In this study of 91 patients from the phase 3 trial, of whom 47 (52%) were high-grade recurrence free at 12 mo (responders), the ability of antiadenovirus antibody levels to predict the durability of therapeutic response to nadofaragene firadenovec was investigated.

• A higher likelihood of durable response was observed in relation to 3-mo titer >800.

• Peak post-treatment titers >800 were detected in 42 (89%) responders vs 26 (59%) nonresponders (assay sensitivity, 89%; negative predictive value, 78%).

• A combination of peak post-treatment titers >800 and peak antibody fold change >8 was found in 22 (47%) responders vs eight (18%) nonresponders (assay specificity, 82%; positive predictive value, 73%).

• Following the first 6 mo of therapy, presence of post-treatment antibody titers >800 was evident in most of the responders.