Background: In a phase 1b trial, a SC formulation of DARA with recombinant human hyaluronidase PH20 (rHuPH20; ENHANZE drug delivery technology, Halozyme, Inc.) had adequate PK, low rates of infusion-related reactions (IRRs) and similar efficacy to DARA IV. This phase 3 study compared the efficacy, PK, and safety of DARA SC vs IV in pts with RRMM. Methods: DARA SC (1,800 mg DARA + rHuPH20 [2,000 U/mL]) and DARA IV (16 mg/kg IV) were given weekly for C1-2 (28-day cycles), every 2 weeks for C3-6, and every 4 weeks thereafter. DARA SC (15 mL) was given over 3-5 mins at alternating left/right abdominal sites. Pts (≥18 years) must have received ≥3 prior lines of therapy (LOT), including a PI and an IMiD, or were double refractory. Co-primary endpoints were ORR (analyzed by Farrington-Manning test, with non-inferiority = 60% retention of ORR) and pre-dose C3D1 DARA C_trough (non-inferiority = lower bound of 90% CI for the ratio of the geometric means [GM] ≥80%). Results: 522 pts were randomized (n=263 SC; n=259 IV). Median age was 67 yrs. Median baseline body weight was 73 kg. Pts received a median of 4 LOT and 100% had received both PI and IMiD; 17% had high cytogenetic risk at baseline. Median follow-up was 7.5 mos. ORR was 41% for DARA SC and 37% for DARA IV. DARA SC retained at least 89% of the benefit of DARA IV (97.5% confidence). The ratio of GM of C_trough for DARA SC over DARA IV was 108% (90% CI, 96%-122%). A significantly lower rate of IRRs was observed with DARA SC vs DARA IV (12.7% vs 34.5%; P<0.0001). Median duration of injection was 5 mins for DARA SC and median duration of infusion was 421/255/205 mins for the first/second/subsequent DARA IV infusions. Median PFS was 5.6 mos DARA SC vs 6.1 mos DARA IV (HR, 0.99; 95% CI, 0.78-1.26). Most common TEAEs (≥15%) were anemia, neutropenia, thrombocytopenia, and diarrhea. Primary reasons for treatment discontinuation included progressive disease (43% SC vs 44% IV) and AEs (7% SC vs 8% IV). Conclusions: Efficacy and PK co-primary endpoints were met, demonstrating non-inferiority of DARA SC to IV. DARA SC significantly decreased IRR rate and administration time, with a comparable safety profile to DARA IV. Clinical trial information: NCT03277105