A new drug being tested in patients with advanced melanoma, the most dangerous form of skin cancer, has shown significant antitumor activity, according to preliminary results of a new study.

The research, conducted by a team of experts from UCLA’s Jonsson Comprehensive Cancer Center, led by Dr. Antoni Ribas, professor of medicine in the division of hematology-oncology, demonstrated that the novel drug comes with “very manageable side effects.”

The results were presented at the 2013 meeting of the American Society of Clinical Oncology and was published in The New England Journal of Medicine.

The drug is called lambrolizumab, also referred to as MK3475, and was discovered and developed by Merck. In April 2012, lambrolizumab was given “Breakthrough Therapy” designation from the U.S. FDA (Food and Drug Administration).

This was the first clinical trial of lambrolizumab in patients with metastatic melanoma and involved a total of 135 individuals who were split into 3 groups with different treatment regimens.

The scientists found that overall, across all dose levels received, lambrolizumab resulted in 38% of patients having confirmed improvement of their cancer.

Patients who were given the highest dose of the drug experienced a 52% improvement, while those who were given the lowest dose experienced a 25% improvement.

Across all subjects, the rate of any tumor response was 77%. “The average duration of response to the drug has not been reached because only five patients who had initial responses have been taken off the study because their cancers got worse. At this point the longest response has been over 1 year,” the authors said.

Adverse reactions with lambrolizumab are generally mild and easy to manage. They include:

More serious side effects, such as inflammation of the lung or kidney and thyroid problems, were only seen in 13% of the patients.

Ribas said:

“This study is showing the highest rate of durable melanoma responses of any drug we have tested thus far in this cancer, and it is doing it without serious side effects in the great majority of patients.”

T cells are important to the immune system because they identify and destroy invaders that lead to infections and illnesses in the human body.

However, cancers such as melanoma are not normally identified by the immune system, and therefore, spread without T cells harming them.

One trouble might be, according to the investigators, that a protein known as PD-L1 on the surface of cancer cells allows them to stay away from T cells that express the protein PD-1 on their surfaces.

PD-1 is blocked by lambrolizumab, an antibody that reactivates an immune reaction to the cancer cells.

Ribas said:

“Lambrolizumab turns on the body’s immune system to attack the cancer, and the immune system seems to remember that the melanoma is the enemy and continues to control it long term.”

These results have resulted in a series of additional trials analyzing lambrolizumab in patients with melanoma as well as other cancers, including lung cancer.

A different study, also presented at American Society of Clinical Oncology (ASCO) meeting, showed that AstraZeneca’s experimental drug, selumetinib, is the first targeted medication to show a notable clinical benefit for patients with melanoma of the eye (metastatic uveal melanoma).

Written by Sarah Glynn