If you follow news about skin cancer (we know that many of our readers are well-informed patients), you may have heard about a new medication that was recently FDA approved for cutaneous squamous cell carcinoma (CSCC). Libtayo (cemiplimab-rwlc) is a type of immunotherapy called a checkpoint blockade inhibitor, and it’s the first one approved to treat certain cases of CSCC. This is exciting news, so let’s break down how this new drug works and whom it might help.
First, Some Basics
Cutaneous squamous cell carcinoma is the second most common type of skin cancer, with about 1.8 million cases in the U.S. each year. Cutaneous means “on the skin,” and these cancers are primarily caused by cumulative, long-term exposure to ultraviolet (UV) light from the sun or indoor tanning. At The Skin Cancer Foundation, where we focus only on skin, we often just use the acronym SCC. But it’s important to know that CSCCs are different from the squamous cell carcinomas you may have heard about in the mouth, throat, genitals or lungs. Those may be linked to the human papillomavirus, smoking or other causes.
Approximately 95 percent of CSCCs are detected early enough that they are usually curable with prompt treatment. The other 5 percent, though, may advance or metastasize, spreading to other parts of the body. As many as 15,000 people in the U.S. die from these cancers each year — about 61 percent more than die of melanoma, the third most common type of skin cancer.
Despite the greater number of CSCC deaths, you’ve probably heard more news about melanoma than about CSCC in recent years. That’s because immunotherapies, which enable a patient’s own immune system to attack invading cancer cells, have revolutionized the treatment of advanced melanoma, extending life for many patients and garnering hopes for a cure. Use of these breakthrough drugs has expanded to other types of cancer as well.
What Is Checkpoint Blockade Therapy?
Until September 2018, however, patients with metastatic or locally advanced CSCC had few options. Libtayo is the first medication approved specifically for these patients. Here’s how a checkpoint blockade therapy works: When something attacks your body, like an infection or cancer cells, it stimulates your immune system to fight it. At the same time, the body has “immune checkpoints” that don’t allow the stimulated immune system to go out of control, because that could result in problems like autoimmune disease.
Cancer cells have the ability to keep those checkpoints active, suppressing the immune system so the cancer can grow and thrive. Libtayo blocks a particular checkpoint called PD-1. It removes the shackles on the immune system and allows your body’s T cells to hunt down and kill the CSCC tumor cells.
How Do Patients Respond to Libtayo?
Early in the clinical trials on Libtayo, many of the patients participating felt discouraged, knowing that other attempts to treat their cancer had not worked, says Michael R. Migden, MD, professor in the Departments of Dermatology and Head and Neck Surgery at The University of Texas MD Anderson Cancer Center and a lead investigator in the studies. After receiving the medication, which is given as an intravenous infusion every three weeks, sometimes they would notice a reaction, such as the tumor appearing more inflamed, and wonder if it was getting worse. “But in many cases I treated, we found that it actually was an early exuberant reaction that started out looking worse but ultimately led to improvement,” he explains.
“Once the patients got past that, when they saw their tumors getting smaller, their spirits improved. I had more than one patient say, ‘Believe it or not, Doc, my tumor actually fell off!’
“I had another patient, he continues, “who had a large tumor on his head. On one of the later visits, I went to touch the area, and the tumor literally collapsed under my hand, as if it were papier-mâché.”
While those results seem miraculous, about half of the patients did not respond to the medication. Others have side effects that can be serious. And some develop resistance to the drugs later. Researchers continue to investigate those issues to find solutions.
But for now, it’s clear that CSCC patients who had run out of treatment options have a new reason to feel optimistic.