LAUSR

e19031 Background: In the MAVORIC Phase 3 study, patients (pts) with previously treated mycosis fungoides (MF)/Sezary syndrome (SS) stage IB-IVB who received mogamulizumab (MOGA) had significantly prolonged progression-free survival and greater overall response rates (ORR) compared to pts on vorinostat (VORI) (Kim et al. Lancet Oncol 2018). Less advanced MF (stage IB/IIA) is a chronic skin malignancy that can involve blood and nodes and may require many lines of systemic therapy over the disease course. This post-hoc analysis specifically examined efficacy and safety of the recently approved MOGA in stage IB/IIA MF pts. Methods: In MAVORIC, stage IB-IVB MF/SS pts who were treated with ≥1 prior systemic therapy were randomized to MOGA or oral VORI. In the post-hoc analysis, time to next treatment (TTNT) was defined as time to any therapy excluding topical steroids or focal radiation treatment. ORR was based on global composite response in 4 disease compartments – skin, blood, lymph nodes, and viscera – achieved at 2 consecutive visits at least 8 weeks apart. Individual compartment responses were also assessed. Results: A total of 85 pts with stage IB/IIA MF were included (MOGA, IB n = 15, IIA n = 21; VORI, IB n = 27, IIA n = 22). Overall, 24% (10/42) of IB pts and 28% (12/43) of IIA pts had received ≥6 prior therapies. Median TTNT with MOGA in IB pts was 11.5 months (mo) (95% CI, 1.4,16.0) compared to 3.1 mo (95% CI, 2.7, 5.3) with VORI; in IIA pts, median TTNT was 10.1 mo (95% CI, 5.5, 12.6) and 4.9 mo (95% CI, 2.4, 8.0), respectively. ORR in IB pts receiving MOGA and VORI was 20% (3/15) and 18.5% (5/27), respectively; ORR in IIA was 19% (4/21) and 0% (0/22), respectively. With respect to stage IB and IIA, compartmental response rates with MOGA were: skin (20% [3/15], 38% [8/21]), blood (0% [0/2], 75% [6/8]), and lymph node (0% [0/0], 15% [3/20]), respectively. Adverse events were generally manageable and consistent with the ITT population. Conclusions: Though MAVORIC was not powered to determine treatment effect by disease stage, this post-hoc analysis of TTNT, ORR, and compartmental response in stage IB/IIA demonstrates meaningful clinical benefit with MOGA in previously treated, less advanced MF pts. Clinical trial information: NCT01728805.