Rationale for New Checkpoint Inhibitor Combinations in Melanoma Therapy

Melanoma therapeutics: a literature review

Melanoma is a relentless type of skin cancer which involves myriad signaling pathways which regulate many cellular processes. This makes melanoma difficult to treat, especially when identified late. At present, therapeutics include chemotherapy, surgical resection, biochemotherapy, immunotherapy, photodynamic and targeted approaches. These interventions are usually administered as either a single-drug or in combination, based on tumor location, stage, and patients' overall health condition. However, treatment efficacy generally decreases as patients develop treatment resistance. Genetic profiling of melanocytes and the discovery of novel molecular factors involved in the pathogenesis of melanoma have helped to identify new therapeutic targets. In this literature review, we examine several newly approved therapies, and briefly describe several therapies being assessed for melanoma. The goal is to provide a comprehensive overview of recent developments and to consider future directions in the field of melanoma.

Novel Targets in Melanoma: Intralesional and Combination Therapy to Manipulate the Immune Response

Clinical outcomes for metastatic melanoma have been dramatically altered by recent developments in immunotherapy and targeted strategies, but response to these therapies is not uniform, the majority of patients do not respond, and clinical response can be self-limited. Current directions in melanoma treatment aim to leverage a combination of therapies for tumors refractory to monoimmunotherapy, to include tumor-directed strategies, such as intralesional therapy and inhibitors designed for novel targets, which may augment current systemic agents when used in combination. Here, we summarize new classes of agents and emerging multimodal combination strategies that demonstrate significant promise in future melanoma management.

PD-1 and beyond to Activate T Cells in Cutaneous Squamous Cell Cancers: The Case for 4-1BB and VISTA Antibodies in Combination Therapy

Non-melanoma skin cancers (NMSC) have a higher incidence than all other cancers combined with cutaneous squamous cell carcinoma (cSCC), capable of metastasis, representing approximately 20% of NMSCs. Given the accessibility of the skin, surgery is frequently employed to treat localized disease, although certain localities, the delineation of clear margins, frequency and recurrence of tumors can make these cancers inoperable in a subset of patients. Other treatment modalities, including cryotherapy, are commonly used for individual lesions, with varying success. Immunotherapy, particularly with checkpoint antibodies, is increasingly a promising therapeutic approach in many cancers, offering the potential advantage of immune memory for protection against lesion recurrence. This review addresses a role for PD-1, 4-1BB and VISTA checkpoint antibodies as monotherapies, or in combination as a therapeutic treatment for both early and late-stage cSCC.

Different expression of BRAFV600E, ALK and PD-L1 in melanoma in children and adolescents: a nationwide retrospective study in Finland in 1990-2014

BACKGROUND

Pediatric melanoma may have a different biological background and more favorable prognosis compared with melanoma in adults. The aim of this study was to investigate melanoma in children and adolescents in the Finnish population in terms of incidence, clinical course, treatment, prognosis and BRAFV600E-, ALK- and PD-L1-positivity of the primary tumors.

MATERIALS AND METHODS

Primary tumor samples and clinical records of all patients aged 0-19 years diagnosed with cutaneous melanoma in Finland in 1990-2014 were collected using the Finnish Cancer Registry database, Finnish hospitals and private pathology laboratories. BRAFV600E, ALK and PD-L1 were analyzed from 54 primary tumors and BRAFV600E from six metastasis samples.

RESULTS

A total of 122 patients diagnosed with cutaneous melanoma were retrieved from the Cancer Registry database. The primary tumor samples of 73 patients were obtained for the review, and 56 cases were included in the study. The incidence of pediatric melanoma increased from 0.02 to 0.1/100 000 during the period 1990-2014. Spitzoid melanoma was the most common subtype (66%). The 10-year cancer-specific survival (CSS) was 88.7% in all patients. The 10-year-CSS did not differ in SLNB-positive or -negative groups. BRAFV600E was positive in 48%, ALK in 9% and PD-L1 in 2% of the tumors. BRAFV600E mutation was associated with 83% of melanoma deaths.

CONCLUSIONS

Young melanoma patients had more favorable prognosis and a different staining profile for BRAFV600E, ALK, and PD-L1 in primary tumor than reported in adults. SLNB status was not an indicator for survival. BRAFV600E-positive patients have worse prognosis and could benefit from surveillance and treatment similarly to adults.

Construction of a core-shell microneedle system to achieve targeted co-delivery of checkpoint inhibitors for melanoma immunotherapy

Synergistic anti-tumor effect of anti-PD-1/L1 antibody (aPD-1/aPD-L1) and 1-methyl-D,L-tryptophan (1-MT) in melanoma has been well demonstrated, while efficient topical delivery systems are still largely unexplored. Here, a highly drug-concentrated hybrid core-shell microneedle (CSMN) system for co-delivery of checkpoint inhibitors was developed. Based on the specific drug-matrix interaction, the system concentrated aPD-L1 in the tips of microneedles through electrostatic interactions, and increased the amount of 1-MT loaded in CSMN by preventing its premature crystallization using PVA, the material used to prepare CSMN core. The prepared CSMN exhibited high transdermal delivery efficiency and long topical retention time of aPD-L1 for 2 days. Drug-loaded CSMN achieved better anti-tumor efficacy than the intra-tumor injection group at the same dose, which was likely because the former recruited more T lymphocytes to the tumor site. These findings suggested that this CSMN system was a promising local delivery system of both aPD-L1 and 1-MT for melanoma immunotherapy, and its unique core-shell structure could be readily adapted as a modular platform for various diseases, where combination therapy of both biomacromolecular drugs and other small-molecular agents were required. STATEMENT OF SIGNIFICANCE: In the present study, a core-shell microneedle (CSMN) system was constructed to achieve targeted co-delivery of checkpoint inhibitors to melanoma, while preventing significant systemic exposure. To overcome the drawback of insufficient drug loading of microneedles and effectively encapsulate two drugs simultaneously, microneedles were divided into two independent functional areas, a charged shell and a hydrophilic core and encapsulated drugs based on respective drug-matrix interaction. The charged shell prepared by chitosan could concentrate aPD-L1 in the tips of microneedles through electrostatic interactions. The core prepared by PVA successfully increased the amount of 1-MT loaded in microneedles by preventing its premature crystallization. The prepared CSMN exhibited high transdermal delivery efficiency and better anti-tumor efficacy than intra-tumor injection at the same dose.

The COX2 Effector Microsomal PGE2 Synthase 1 is a Regulator of Immunosuppression in Cutaneous Melanoma

PURPOSE

Microsomal prostaglandin E2 synthase 1 (mPGES1) was evaluated as an important downstream effector of the COX2 pathway responsible for tumor-mediated immunosuppression in melanoma.

EXPERIMENTAL DESIGN

The analysis of a stage III melanoma tissue microarray (n = 91) was performed to assess the association between mPGES1, COX2, CD8, and patient survival. Pharmacologic inhibitors and syngeneic mouse models using PTGES-knockout (KO) mouse melanoma cell lines were used to evaluate the mPGES1-mediated immunosuppressive function.

RESULTS

We observed correlations in expression and colocalization of COX2 and mPGES1, which are associated with increased expression of immunosuppressive markers in human melanoma. In a syngeneic melanoma mouse model, PTGES KO increased melanoma expression of PD-L1, increased infiltration of CD8a+ T cells, and CD8a+ dendritic cells into tumors and suppressed tumor growth. Durable tumor regression was observed in mice bearing PTGES KO tumors that were given anti-PD-1 therapy. Analysis of a stage III melanoma tissue microarray revealed significant associations between high mPGES1 expression and low CD8+ infiltration, which correlated with a shorter patient survival.

CONCLUSIONS

Our results are the first to illustrate a potential role for mPGES1 inhibition in melanoma immune evasion and selective targeting in supporting the durability of response to PD-1 checkpoint immunotherapy. More research effort in this drug development space is needed to validate the use of mPGES1 inhibitors as safe treatment options.

Rational combination of cancer immunotherapy in melanoma

The recent advances in cancer immunotherapy with unprecedented success in therapy of advanced melanoma represent a turning point in the landscape of melanoma treatment. Given the complexity of activation of immunological system and the physiologic multifactorial homeostatic mechanisms controlling immune responses, combinatorial strategies are eagerly needed in melanoma therapy. Nevertheless, rational selection of immunotherapy combinations should be more biomarker-guided, including not only the cancer immunogram, PD-L1 expression, interferon gene expression signature, mutational burden, and tumor infiltration by CD8+ T cells but also intratumoral T cell exhaustion and microbiota composition. In this review, we summarize the rationale to develop combination treatment strategies in melanoma and discuss biological background that could help to design new combinations in order to improve patients' outcome.

Melanoma treatment in review

Melanoma represents the most aggressive and the deadliest form of skin cancer. Current therapeutic approaches include surgical resection, chemotherapy, photodynamic therapy, immunotherapy, biochemotherapy, and targeted therapy. The therapeutic strategy can include single agents or combined therapies, depending on the patient’s health, stage, and location of the tumor. The efficiency of these treatments can be decreased due to the development of diverse resistance mechanisms. New therapeutic targets have emerged from studies of the genetic profile of melanocytes and from the identification of molecular factors involved in the pathogenesis of the malignant transformation. In this review, we aim to survey therapies approved and under evaluation for melanoma treatment and relevant research on the molecular mechanisms underlying melanomagenesis.