Background: In the CANDOR study (N = 466) of pts with relapsed or refractory multiple myeloma (RRMM), a statistically significant improvement in progression-free survival (HR = 0.63; 95% CI, 0.46-0.85; p = 0.0014) was observed in the KdD vs Kd arms. Here, we report a secondary endpoint of CANDOR evaluating HRQoL. Methods: HRQoL was assessed using the Global Health status (GHS)/Quality of Life (QoL) domain of the European Organisation for Research and Treatment of Cancer Quality of Life (EORTC QLQ-C30), which was completed on Day 1 of Cycle 1 and every 28±7 days through the first follow-up visit. The GHS/QoL was scored from 0–100, with higher scores indicating better QoL. The scores were compared between the KdD and Kd arms using a restricted maximum likelihood-based mixed effects model for repeated measures under the assumption of missing data at random. A minimally important difference of 5 points between arms was prespecified. An exploratory time-by-time sensitivity analysis by ANCOVA was used to evaluate the treatment effect on the GHS/QoL score among pts who remained on treatment until the specified visit (cycle 3 and every 3 cycles thereafter). Results: GHS/QoL completion rates from baseline through up to cycle 26 (study ongoing) for randomized pts who remained on treatment were > 81% for both the KdD and Kd arms; the median extent of missing GHS/QoL data was 5.3% for the KdD arm and 12.1% for the Kd arm. KdD was associated with higher GHS/QoL scores relative to Kd starting at Cycle 7 and this was maintained until Cycle 26 (by mixed effect model, overall LSME difference [95% CI], 0.06 [–2.39, 2.50]; p = 0.96). At Cycle 18, the mean difference between arms approached the prespecified clinically meaningful difference of 5 points (by ANCOVA, [difference: KdD–Kd (SE), 4.06 (2.45)]). In an exploratory analysis of pts who remained on treatment at each cycle, a higher rate of pts reported an improvement of ≥10 points in GHS/QoL score from baseline in the KdD vs Kd arms, with the greatest differences observed at Cycle 7 (Odds Ratio [OR] for KdD/Kd [95% CI], 2.37 [1.29, 4.34]), Cycle 9 (OR [95% CI], 2.96 [1.46–6.03]), Cycle 13 (OR [95% CI], 2.44 (1.15-5.17), and Cycle 16 (OR [95% CI], 2.77 [1.27–6.07]). Conclusions: In addition to the superior clinical benefit observed with KdD vs Kd, HRQoL was maintained with the KdD triplet. A higher rate of pts treated with KdD reported an improvement of ≥10 points from baseline. Clinical trial information: NCT03158688