Microinvasive melanoma: cutaneous pharmacotherapeutic approaches

Topical Calcipotriol Plus Imiquimod Immunotherapy for Nonkeratinocyte Skin Cancers

Nonkeratinocyte cutaneous malignancies, including breast cancer cutaneous metastasis and melanoma in situ, are often poor surgical candidates. Imiquimod (IMQ), a toll-like receptor 7 agonist that activates innate immunity in the skin, is used to treat these cutaneous malignancies. However, IMQ's modest effect on the activation of adaptive immunity limits its efficacy as a monotherapy. In this study, we demonstrate that topical TSLP cytokine inducers-calcipotriol and retinoic acid-synergize with IMQ to activate CD4+ T-cell immunity against nonkeratinocyte cutaneous malignancies. Topical calcipotriol plus IMQ treatment reduced breast tumor growth compared with calcipotriol or IMQ alone (P < 0.0001). Calcipotriol plus IMQ-mediated tumor suppression was associated with significant infiltration of CD4+ effector T cells in the tumor microenvironment. Notably, topical calcipotriol plus IMQ immunotherapy enabled immune checkpoint blockade therapy to effectively control immunologically cold breast tumors, which was associated with induction of CD4+ T-cell immunity. Topical treatment with calcipotriol plus IMQ and retinoic acid plus IMQ also blocked subcutaneous melanoma growth. These findings highlight the synergistic effect of topical TSLP induction in combination with innate immune cell activation as an effective immunotherapy for malignancies affecting the skin.

Imiquimod in dermatology: an overview

Imiquimod is an immune response modifier commercially available as a 3.75 and 5% cream. Topical imiquimod stimulates the innate and adaptive immune responses and induces cytokine production. This allows its use for the treatment of a wide variety of benign and malignant skin conditions due to its potential antiviral, antitumor, and immunoregulatory effects. Currently, topical imiquimod is US Food and Drug Administration (FDA)-approved for the treatment of anogenital warts, actinic keratosis, and superficial basal cell carcinomas. However, it has also shown a beneficial effect in the treatment of many other skin disorders. In this review, we describe existing evidence on the mechanism of action of topical imiquimod, its FDA-approved indications, off-label uses, and side effects.

Developments in Intralesional Therapy for Metastatic Melanoma

BACKGROUND

Locoregional advanced melanoma poses a complex clinical challenge that requires a multidisciplinary, patient-centered approach. Numerous agents have been studied for their suitability as intralesional therapy in the past decades, but few have successfully completed phase 3 clinical trial testing.

METHODS

The relevant medical literature was searched for articles regarding use of intralesional therapies in metastatic melanoma. Therapies with data from phase 2 or higher studies were selected for review. This review also summarizes the mechanisms of action, adverse-event profiles, and clinical data for these agents.

RESULTS

Intralesional therapies demonstrate promising effects in select patients with advanced melanoma. The optimal approach should be individually tailored and consist of a combination of intralesional therapies, regional perfusions, systemic immunotherapies, targeted therapies, and surgery, if necessary.

CONCLUSIONS

Due to its relatively good local response rates and tolerable adverse-event profile, intralesional therapy may be a treatment option for select patients with unresectable, locally advanced or metastatic melanoma.

Intralesional therapy for metastatic melanoma

INTRODUCTION

Intralesional therapy for metastatic melanoma has some advantages over systemic therapy. Local drug administration allows for delivery of an increased concentration of the agent and reduced systemic exposure, thereby increasing local efficacy and limiting toxicity. Moreover, since in vivo tumor nodules contain the tumor antigens, this tumor tissue may serve as an autologous vaccine to induce systemic immunity. This so-called 'bystander effect', where uninjected distant lesions exhibit a response, has been reported in select intralesional therapy trials.

AREAS COVERED

This review will give an overview of the working mechanisms, clinical evidence and side effects for available intralesional and topical therapies and summarize the most recent developments in this field.

EXPERT OPINION

The ideal treatment approach for locoregionally advanced melanoma should be multidisciplinary and tailored to the patient, taking into consideration patient-related, tumor-related factors (such as location, tumor burden, mutation status) and previous treatments received. It will likely not be a single therapy, but rather a combination of injectable treatments, regional perfusions and systemic therapies.