Novel treatments for melanoma brain metastases

BACKGROUND

The development of brain metastases is common in patients with melanoma and is associated with a poor prognosis. Treating patients with melanoma brain metastases (MBMs) is a major therapeutic challenge. Standard approaches with conventional chemotherapy are disappointing, while surgery and radiotherapy have improved outcomes.

METHODS

In this article, we discuss the biology of MBMs, briefly outline current treatment approaches, and emphasize novel and emerging therapies for MBMs.

RESULTS

The mechanisms that underlie the metastases of melanoma to the brain are unknown; therefore, it is necessary to identify pathways to target MBMs. Most patients with MBMs have short survival times. Recent use of immune-based and targeted therapies has changed the natural history of metastatic melanoma and may be effective for the treatment of patients with MBMs.

CONCLUSIONS

Developing a better understanding of the factors responsible for MBMs will lead to improved management of this disease. In addition, determining the optimal treatments for MBMs and how they can be optimized or combined with other therapies, along with appropriate patient selection, are challenges for the management of this disease.

Advances in therapy for melanoma brain metastases

Melanoma cells frequently metastasize to the brain, and approximately 50% of patients with metastatic melanoma develop intracranial disease. Historically, central nervous system dissemination has portended a very poor prognosis. Recent advances in systemic therapies for melanoma, supported by improved local therapy control of brain lesions, have resulted in better median survival for these patients. We review current local and systemic approaches for patients with melanoma brain metastases.

Advances in the management of melanoma: targeted therapy, immunotherapy and future directions

Metastatic melanoma is an aggressive, immunogenic and molecularly heterogeneous disease for which most patients require systemic treatment. Recently, significant clinical breakthroughs have revolutionized the treatment of advanced melanoma, leading to the licensing of ipilimumab, a monoclonal antibody targeting cytotoxic T-lymphocyte-associated antigen 4, and vemurafenib, a BRAF inhibitor used in patients whose tumors contain a V600 mutation in the BRAF gene. This recent success has led to optimism and momentum has gathered with updated trial results from these therapies, next-generation compounds that target validated molecular pathways and novel agents that are mechanistically distinct. This review summarizes the recent advances and updated results since the licensing of vemurafenib and ipilimumab, the benefits and limitations of these agents, future strategies to improve upon existing treatments and overcome acquired resistance, in-progress and future clinical trials, as well as novel therapeutic targets, pathways and therapies that hold promise in advancing clinical benefit.

Immunomodulating antibodies in the treatment of metastatic melanoma: the experience with anti-CTLA-4, anti-CD137, and anti-PD1

Clinical activity of anti-CTLA-4 (cytotoxic T-lymphocyte antigen-4) monoclonal antibodies (mAb) has changed the approaches for the treatment of cancer in terms of patterns of response, duration of response, and adverse event profiles. In fact, antibodies that block the interaction of CTLA-4 with its ligands B7.1 and B7.2 can enhance immune responses, including anti-tumor immunity. Two recent studies using ipilimumab (an anti-CTLA-4 mAb) demonstrated improvements in overall survival in the treatment of advanced melanoma. These studies utilized two different schedules of treatment in different patient categories (first and second line of treatment). However, the results were quite similar despite the different dosage used and the combination with dacarbazine in the first line treatment. Ongoing clinical studies will establish the efficacy of ipilimumab as monotherapy or in combination with other drugs for the treatment of metastatic melanoma and a variety of other cancers. Other antibodies, such as CD137 agonists and PD-1 antagonists, are currently in various stages of pre-clinical and clinical development. Agonist antibodies directed against CD137 (4-1BB) on the surface of antigen-primed T-lymphocytes increase tumor immunity that is curative against some transplantable murine tumors. Programmed death-1 (PD1) is a surface molecule delivering inhibitory signals important to maintain T-cell functional silence against their cognate antigens. Interference with PD1 or its ligand PD-L1 (B7-H1) increases anti-tumor immunity. As a result, human mAbs anti-PD1 and anti-PD-L1 are under clinical development. This paper reviews recent studies in the treatment of advanced melanoma with these types of monoclonal antibodies. Ipilimumab can be considered a cornerstone of a new era in melanoma treatment. However, the aim is to optimize the therapy with anti-CTLA-4 antibodies to define the best schedule for next combination regimens (other immunomodulatory antibodies, BRAF/MEK inhibitors, vaccines, etc.) that represent the natural evolution of future melanoma therapy.

Ipilimumab: a novel immunostimulatory monoclonal antibody for the treatment of cancer

Ipilimumab (Yervoy, developed by Medarex and Bristol-Myers Squibb) is a fully human monoclonal IgG1κ antibody against the cytotoxic T-lymphocyte antigen-4 (CTLA-4), an immune-inhibitory molecule expressed in activated T cells and in suppressor T regulatory cells. Interaction of the monoclonal antibody with CTLA-4 blocks inhibitory signals generated through this receptor and enhances T cell activation, leading to increased antitumor responses. Ipilimumab has been approved by FDA in March 2011 as monotherapy (3mg/kg every 3 weeks for 4 doses) for the treatment of advanced (unresectable or metastatic) melanoma both in pre-treated or chemotherapy naïve patients. Four months later, ipilimumab has received a rapid approval by the European Commission, after a positive opinion from the Committee for Medicinal Products for Human Use. However, the indication in the EU is limited to previously-treated patients with advanced melanoma. Ipilimumab is the first agent that has demonstrated to improve overall survival in patients with metastatic melanoma, which has a very poor prognosis, in randomized phase III clinical trials. The patterns of tumour response to ipilimumab differ from those observed with cytotoxic chemotherapeutic agents, since patients may have a delayed yet durable response and obtain long-term survival benefit despite an initial tumour growth. The major draw-back of ipilimumab is the induction of immune-related adverse effects; the latter can be life-threatening, unless promptly managed with immunosuppressive agents (most frequently corticosteroids) according to specific guidelines. Further development of ipilimumab includes its use in the neoadjuvant or adjuvant high-risk melanoma setting and for the treatment of other refractory and advanced solid tumours, either as single agent or in combination with additional immunostimulating agents or molecularly targeted therapies.