Understanding Reason for Drug Resistance May Lead to Increased Effectiveness of Mesothelioma Drug

• Nancy Meredith
• Featured News

Researchers report they better understand why patients eventually develop resistance to the anti-cancer drug Tagrisso (osimertinib) that targets the epidermal growth factor receptor (EGFR) mutation in lung cancer patients. Using quantum and molecular mechanics, the researchers found “subtle changes” in the biomarker that left the drug ineffective. This finding could point researchers to a way to enhance the drug’s effectiveness for lung cancer and mesothelioma patients.

EGFR is a protein that is an anti-cancer drug target due to its role in cell proliferation. Osimertinib is an EGFR inhibitor for the way it binds to the EGFR protein and switches off a cancer cell‘s ability to spread and divide. The drug is generally effective in stopping the spread of cancer, however, according to researchers from the University of Bristol in the UK, most patients develop resistance within one year of treatment. Drug resistance arises, note the researchers, “because the EGFR protein mutates, so that the drug binds less tightly.”

The researchers took a closer diagnosis at why one particular mutation, the L718Q EGFR mutation in which just a single amino acid was changed, led the cancer to fight off, or resist, osimertinib. It took a unique collaboration “between medicinal and computational chemists and clinical oncologists” from the Universities of Bristol and Parma in Italy to resolve the reason for the resistance, according to a Feb. 12 press release from the University of Bristol.

Through a series of sophisticated molecular simulations the team revealed that the mutant protein L718Q “changes in a way that stops the drug reacting and binding to it.” The simulations ultimately allowed them to delve into the chemical reactions in EGFR, and reveal the “mechanisms” behind the drug resistance that, according to the researchers, “can be subtle and non-obvious.”

“Now the challenge is to exploit this discovery in the development of novel drugs targeting EGFR mutants for cancer treatment in the future,” said Adrian Mulholland, Professor of Chemistry at the University of Bristol.

According to a 2009 article in Current Drug Targets, EGFR overexpression has been shown in more than 50% of pleural mesothelioma patients. Approximately 15% of patients with lung cancer in the U.S. express EGFR mutations.

Lung cancer is the leading cause of cancer death in the United States, with an estimated 234,030 new diagnoses and 154,050 deaths in 2018, according to the American Cancer Society. Pleural mesothelioma is a form of lung cancer, affecting the lining of the lungs, with 3,000 new diagnoses each year, and nearly the same number of Americans dying from the terminal cancer. These grim statistics make continued research into increasing the efficacy of cancer drugs critical.

Read the study in the Feb. 3 issue of Chemical Science.