Prospective Pilot Evaluation of the Efficacy and Safety of Topical Ingenol Mebutate Gel for Localized Patch/Plaque Stage Mycosis Fungoides

Mycosis Fungoides (MF) is the most frequent type of the primary cutaneous NK/T-cell lymphomas. Ingenol mebutate (IM) displays in vitro pro-apoptotic properties on neoplastic lymphocytes.

To evaluate the efficacy and safety of IM gel as topical treatment for MF.

Ten male patients with longstanding classic type MF (n=9) and follicular MF (FMF; n=1), T2bN0M0B0, stage Ib, resistant to systemic methotrexate or acitretin therapies for at least 3 months, were included in this pilot study. In these patients, 11 target patch/plaque stage lesions with an area ≤ 25 cm² were selected for IM therapy (0,05%, 2 weekly applications). The primary endpoint was the improvement of the CAILS scores. Biopsies were performed before and after treatment from 10 target lesions. Relapse rates were evaluated at 6 months.

The mean CAILS score of treated target lesions was reduced by 58.2%. The mean erythema, scaling and plaque elevation scores were improved by 73.6%, 93.9% and 97.9% (p<0.0001), respectively, while the lesion size remained unchanged (p=0.34). A complete or partial clearance of histological and immunohistochemical features was observed in 6/10 (60%) and 4/10 (40%) of the MF or FMF target lesions, respectively. Monoclonal TCR rearrangement was evidenced in 100% (7/7) of the patients and in 3/7 (43%) after treatment. The relapse rate at 6 months was 18%. All the patients experienced burning sensations, oozing and crusting.

IM gel warrants further investigation and development as a potential topical treatment for localized patch/plaque stage MF and FMF.