Mogamulizumab (ATLL)

Background

Phase II, single-arm, multicenter Japanese pivotal study. 26 evaluable patients with relapsed/refractory adult T-cell leukemia/lymphoma (ATLL), an aggressive HTLV-1-driven malignancy with CCR4 expression in >90% of cells. Mogamulizumab is a defucosylated anti-CCR4 monoclonal antibody with enhanced ADCC. This study established mogamulizumab as the first targeted therapy for ATLL.

Interventions and follow up

Regimen: Mogamulizumab 1.0 mg/kg IV weekly × 8 doses in R/R adult T-cell leukemia/lymphoma (ATLL)
Primary endpoint: Overall response rate
Median follow-up: updated analysis at ~25 months

Results

ORR (primary): 50% (95% CI 30–70%)
CR rate: 31%
Median PFS: 5.2 months
Median OS: 13.7 months

Adverse events

Infusion/dermatologic: Infusion reactions any grade 89% (grade ≥3 8%); skin rash any grade 63% (grade ≥3 11%), reflecting CCR4+ skin T-cell depletion
Infectious/hematologic: Grade ≥3 infections 23%; lymphopenia expected from CCR4+ regulatory T-cell depletion
Mortality: No treatment-related deaths

Conclusions

Mogamulizumab achieved a 50% ORR (31% CR) in heavily pretreated R/R ATLL with some durable responses, establishing CCR4 targeting as an effective strategy in this otherwise treatment-refractory disease. The unique skin rash is a class-effect toxicity requiring dermatologic management.

Key Limitations

Very small single-arm study (n=26) in a Japanese population. Short median PFS (5.2 months) indicates limited durability for most patients. Pre-allograft mogamulizumab has been associated with increased severe GVHD, complicating its use as a bridge to transplant.

Clinical Context

Mogamulizumab was approved in Japan for R/R ATLL (2012); the US FDA later approved it (2018) for R/R mycosis fungoides and Sezari syndrome based on the MAVORIC trial, not for ATLL. ESMO recognizes it as an option in CCR4-positive T-cell lymphomas, with caution regarding subsequent allogeneic transplant.

References