396 | ONGOING PHASE 2, OPEN‐LABEL, MULTICENTER, SINGLE‐ARM STUDY ASSESSING AN EVERY‐4‐WEEK DOSING SCHEDULE OF MOGAMULIZUMAB IN CUTANEOUS T‐CELL LYMPHOMA: PRELIMINARY RESULTS

J. Scarisbrick and C. Querfeld equally contributing author. Introduction: Mogamulizumab is approved to treat relapsed/refractory mycosis fungoides/Sézary syndrome (MF/SS). In the phase 3 MAVORIC study (N = 372), mogamulizumab, given 1 mg/kg weekly in cycle (C) 1 and then biweekly (Q2W), demonstrated superior efficacy versus vorinostat and a manageable safety profile. We present preliminary results (data-cut Nov 2023) from an ongoing phase 2 study of mogamulizumab administered using a 2 mg/kg Q4W dosing schedule (NCT04745234) in patients with relapsed/refractory MF/SS after ≥ 1 systemic therapy. Methods: Primary objective was safety/tolerability. Secondary objectives included: pharmacokinetics/pharmacodynamics, overall response rate (ORR: complete/partial response [CR/PR] lasting ≥ 4 weeks), compartmental response, and time-to-response (TTR). Descriptive statistics were used. Results: 34 patients were enrolled (median age: 64.0 years; 64.7% male): 17.6% had SS, 82.4% MF (stage IB–IIA: 23.5%; IIB–IIIB: 58.8%; IVA–IVB: 17.6%). Median follow-up was 8.61 months. Treatment-emergent adverse events (AEs) occurred in 97.1% (33/34) of patients; 26.5% had serious AEs. In patients who completed C1 and received ≥ 1 dose at 2 mg/kg (n = 32), ORR was 37.5% (12/32; 1 CR): 66.7% (4/6; 1 CR) in SS; 30.8% (8/26) in MF. Compartmental response was 40.6% (13/32; 1 CR) in skin; 20.0% (2/10; 0 CR) in lymph nodes; 100% (9/9; 8 CR) in blood; 0% (0/1) in viscera. Median TTR was 1.82 months (range: 1.0–3.8). Pharmacokinetics/pharmacodynamics results showed increasing mogamulizumab concentrations with repeated doses, reaching steady state by C3 (C3–7, day 1 range: 17,972.8–21,046.0 ng/mL) and depletion of circulating CD7– and CD26– malignant T–cells. Conclusions: Preliminary results showed a promising safety profile and response rates of 2 mg/kg Q4W mogamulizumab. Research funding declaration: We would like to thank the study participants, the investigators, and Karen Dwyer. The study was supported by Kyowa Kirin, Inc. Medical writing and editorial assistance were provided by Doriana Di Bella of Excerpta Medica and funded by Kyowa Kirin, Inc. according to the Good Publication Practice guidelines. Encore Abstract: Regional or national meetings with up to 1000 attendees Keywords: molecular targeted therapies; cutaneous non-Hodgkin lymphoma Potential sources of conflict of interest: J. Scarisbrick Consultant or advisory role: Kyowa Kirin, Takeda, Recordat, 4SC, Innate Pharma, Helsinn C. Querfeld Consultant or advisory role: Helsinn, Kyowa Kirin, Citius Phramceuticals Other remuneration: Helsinn, Kyowa Kirin O. Akilo Consultant or advisory role: Trillium Therapeutics Other remuneration: Therapeutics, Pfizer M. Bagot Consultant or advisory role: Kyowa Kirin, Innate Pharma, Takeda, Recordati R. Cowan Consultant or advisory role: Kyowa Kirin A. Martín García-Sancho Consultant or advisory role: Abbvie, AstraZeneca, BMS, Genmab, Gilead/Kite, GSK, Ideogen, Incyte, Kyowa Kirin, Lilly, Miltenyi, Novartis, Regeneron, Roche, Sobi Honoraria: BeiGene, BMS, Eusa Pharma, Gilead/Kite, Ideogen, Incyte, Janssen, Kyowa Kirin, Roche, Sobi, Takeda Educational grants: Gilead/Kite, Janssen, Roche, BMS L. J. Geskin Consultant or advisory role: Kyowa Kirin A. O. Huen Other remuneration: Galderma Inc, Innate Pharmaceuticals, Kymera, Kyowa Kyrin, Rhizen Pharmaceuticals, Scitech J. Jadwani Employment or leadership position: Kyowa Kirin Y. Liu Employment or leadership position: Kyowa Kirin H. Zhao Employment or leadership position: Kyowa Kirin P. L. Ortiz-Romero Other remuneration: Actelion, Kyowa Kirin, Takeda A. Patel Employment or leadership position: Kyowa Kirin R. M. Pujol Stock ownership: Almirall, Helsinn, Kyowa Kirin, Recordati Rare Diseases, Takeda P. Quaglino Consultant or advisory role: Actelion, Helsinn, Innate Pharma, Kyowa Kirin, Takeda, Therakos Honoraria: Actelion, Helsinn, Innate Pharma, Kyowa Kirin, Takeda, Therakos R. Vuppugalla Employment or leadership position: Kyowa Kirin Y. H. Kim Consultant or advisory role: CRISPR, Drenbio, Innate, Kyowa Kirin Other remuneration: CRISPR, Drenbio, Innate, Kyowa Kirin, Seattle Genetics/Pfizer