Background: Patients (pts) with BCG-unresponsive NMIBC have limited treatment options and are at an increased risk for cystectomy. Nogapendekin alfa inbakicept (NAI, also known as N-803), is an interleukin-15 superagonist (IL-15RαFc), which synergizes with BCG to elicit innate immune memory resulting in durable complete responses (CRs) in this patient population. In an open-label, 3-cohort, multicenter Phase 2/3 study of intravesical BCG plus NAI in BCG-unresponsive high-grade NMIBC (QUILT 3.032; NCT03022825), pts with carcinoma in situ (CIS; Cohort A) have a CR rate of 71% (median duration 26.6 months), 89.2% cystectomy avoidance and 100% bladder cancer specific survival at 24 months. We submit here the first quality of life (QOL) data report in the same pts cohort. Methods: Cohort A: 86 pts (median age 73 years; 87% male) with histologically confirmed BCG-unresponsive CIS with or without Ta/T1 disease, treated with intravesical BCG 50 mg plus NAI 400 μg. Mean baseline ECOG score was 0.183, with 82% of pts having score = 0. QOL was measured by the EORTC QOL Questionnaire Core 30 (QLQ-C30) and QOL NIMBC-Specific 24 Questionnaire (QLQ-NMIBC24). Results: Multivariate analyses have shown no significant changes over time for any of the measured QOL domains. Mild worsening vs. baseline in feeling ill was reported by 6% and 3% of pts by week 27 and 52, while 4% and 6% reported improvement. By week 78 and 104, 7% and 9% of pts reported improvement vs. baseline in their wellbeing with the majority being stable (non-significant). No statistically significant variations were detected in the physical function (PF) score (baseline vs. week 27, 52, 78 and 104). Higher PF scores were observed in pts responding to the therapy vs. non-responders; however, baseline value of PF was also higher in responders vs. non-responders. In contrast to historical results of BCG alone, week 27 physical function scores were numerically higher than baseline, with a subsequent nadir at week 78 and recovery to baseline by week 104 (non-significant). Hospitalizations for any reason remained low (0% - 6% per assessments) during the study. Conclusions: QOL measurement supports good tolerability of the intravesical NAI plus BCG in BCG-unresponsive, high-grade NMIBC pts with CIS. These results further strengthen the evidence of a favorable benefit: risk ratio of this novel combination immunotherapy, in a challenging disease. Clinical trial information: NCT03022825.