Local immunotherapy with monobenzone and imiquimod cream (MI) for skin metastases in melanoma patients

Melanoma is an aggressive life-threatening type of cancer that still lacks effective treatment options for metastatic disease. Some patients also develop cutaneous metastases which are preferably surgically excised. In patients with large numbers of cutaneous metastases cold steel surgery no longer is an option and radiotherapy, isolated limb perfusion (ILP) carbon dioxide laser ablation, topical immune modifiers and intralesional therapy are used, often in an experimental, palliative setting. Clinical results vary; most therapies yield only temporary responses and fail to control disease.
Melanoma has shown to be a good candidate for immunotherapy, during which vitiligo development has been associated with a favourable clinical outcome. Recently, we developed a new therapy, based on the potent depigmentation agent monobenzone cream combined with imiquimod (MI). MI treatment induced effective melanoma-reactive immunity in established melanoma in mice. The topical immunostimulating compound imiquimod has been used as local therapy for cutaneous melanoma metastases in several experimental trials, showing an efficient anti-tumor response and sustained tumor regression after local application.

We aim at inducing immunity against melanocytes by skin-bleaching using monobenzone, combined with immunostimulation, using imiquimod, as means of local immunotherapy for cutaneous melanoma. The monobenzone/imiquimod (MI) regimen is a low-cost, simple therapy consisting of two creams. It is a non-invasive therapy and besides local skin irritation and depigmentation, no systemic side effects are expected to occur. It is applicable in broad range of patients as it requires no selection of HLA haplotypes. Based on our preclinical data, we expect MI therapy to be a good alternative or adjuvant for current local therapies used. The MI compounds have been registered and used for human skin application in the international dermatology practise, making the therapy easy applicable in the clinic. Melanoma patients with stable stage III-IV disease with unresectable cutaneous metastases will be asked to participate in this study. Treatment will consist of daily application of monobenzone 20% cream and 3x/week imiquimod cream (Aldara 5%) to cutaneous melanoma metastases during 12 weeks.

Immunotherapy by skin-bleaching agent monobenzone combined with immunostimulating agent imiquimod induces specific antimelanoma immunity and suppresses the growth of cutaneous melanoma metastases.

t=0 (baseline), 6 weeks, 12 weeks, 16 weeks.

Melanoma patients who meet the inclusion criteria will be treated with daily monobenzone 20% cream combined with 3 times a week imiquimod cream (Aldara 5% imiquimod). If this treatment regimen gives too much local toxicity, treatment will be temporally stopped. When the skin has healed, treatment can be continued. Patients will apply maximally 2 sachets of Aldara cream 3 times a week on all cutaneous metastases present on an appointed body part (arm, leg) including a 1-2 cm circumferential area of normal skin around the lesions. Skin is an important target for MI therapy, since monobenzone specifically interacts with melanocytes which reside in the skin. This interaction can induce specific immunity that is active against melanoma cells. Therefore, treatment of normal skin is an important component of MI therapy. Hereafter, daily monobenzone 20% cream will be applied to the same skin area. Application is preferably done at night before going to sleep. At the baseline visit the cutaneous lesions to be treated will be appointed and measured. Treatment will in principle be continued for 12 weeks.