Development of peptides as therapeutics to treat drug-resistant metastatic melanoma

Overview

Melanoma is a very aggressive cancer due to its metastatic potential, and the third most common in Australia. Many patients with metastatic melanoma have strong side effects, do not respond, or develop resistance to current therapies, which results in low survival rate (26% in 5-years). This project aims at developing a new class of therapeutic leads to tackle drug-resistance in metastatic melanoma.

Currently, the preferred first-line regimen given to patients with metastatic melanoma is immunotherapy with antibodies (i.e. ipilimumab and nivolumab), which activate the immune response against melanoma cells. Although immunotherapy can produce durable outcomes, 50% of the patients do not respond to this treatment. For patients who do not respond, or do not tolerate, immunotherapy and carry the mutant B-Raf V600E (which occurs in 50% of metastatic melanoma), the second-line treatment is targeted therapy with small molecule drug kinase inhibitors (e.g. verumafenib, dabrafenib) that inhibit the oncogenic BRAF/MEK pathway. In general, patients with this phenotype respond well to kinase inhibitors as a single agent therapy, but rapidly acquire drug-resistance and the disease progresses within six to ten months of treatment.

Aims and Hypotheses

Patients need alternative therapeutic approaches to attack metastatic melanoma tumours not treatable with current therapies. We propose to develop a specific anti-melanoma therapy less likely to induce drug-resistance by using stable host defense peptide able to specifically target melanoma cell membranes. In recent years, we have identified host defence peptides active against metastatic melanoma cells carrying the wild-type or mutant B-Raf, and not toxic towards tested healthy cells. In addition, these peptides have drug-like properties (e.g. resistance to proteases, cross cell membranes, very amenable to structural modifications). Our preliminary studies showed that these peptides are also active towards metastatic melanoma cells that have become drug-resistant (e.g. WM164 resistant to dabrafenib). Furthermore, metastatic melanoma cells did not to develop drug-resistance towards the tested peptides. Thus, these peptides are well suited for use as templates to design therapeutic leads to target drug-resistant metastatic melanoma cells. Aims: The specific goals of this project are to expand on our preliminary results and: 1) screen toxicity of a panel of peptides on their ability to target and kill drug-resistant metastatic melanoma cells; 2) characterise their mode-of-action; and 3) improve their therapeutic efficacy.

Research plan and methods

Aim 1. Toxicity of selected peptide analogues will be investigated against a panel of cells including melanoma cells with wild-type B-Raf, or with mutant B-RafV600E non-resistant and drug-resistant, primary non-cancerous melanocytes and ketanocytes, and primary blood cells. Co-treatment of peptides and small-molecule drugs (e.g. dabrafenib and verumafenib) will also be compared.

Aim 2. The mode-of-action used by active peptides and their selectivity for melanoma cells will be examined. In particular, we will investigate their ability to target and enter inside cells, and disrupt their membranes. This will be investigated using fluorescence spectroscopy methodologies, flow cytometry, confocal microscopy, and surface plasmon resonance. As cell membrane composition seems to govern selectivity of these peptides towards melanoma cells, we will characterise the peptide-lipid binding with vesicles prepared from membrane extracts of a panel of cells, including healthy cells, drug-resistant and non-resistant metastatic melanoma cells, using surface plasmon resonance.

Aim 3. Selected lead peptides will be tested for toxicity and activity in vivo using xenograft mice models (e.g. B16-F10 cells implanted directly into ears).

Based on activity (aim 1), mode-of-action (aim 2) and in vivo efficacy (aim 3), we will design new peptides with improved selectivity and efficacy. Conjugation, or co-treatment, with small molecule drugs, will be investigated.

Expected outcomes

This project will provide new knowledge in the field of melanoma membrane biology, in drug-resistance and in peptide drug research. This research may lead to next generation anticancer leads to treat drug-resistant metastatic melanoma.

Clinical significance/commercial impact

This project addresses the lack of specificity, drug-resistance and side effects of current therapeutics to treat metastatic melanoma. This research can advance the development of alternative leads to treat melanoma.

Keywords

• drug-resistance
• peptide therapeutics
• anti-cancer

Contact

Contact Sonia Troeira Henriques for more information.

Email: sonia.henriques@qut.edu.au Telephone: +61 7 34437342