Pembrolizumab May Work for Mesothelioma Patients

The U.S. Food and Drug Administration (FDA) recently approved an anti-PD-1 therapy that may also prove helpful to mesothelioma patients.

The newly approved therapeutic agent is pembrolizumab. It’s an immunotherapy agent designed to block interaction between PD-1 and its two ligands, PD-L1 and PD-L2.

By creating this blocking action, it helps the immune system recognize cancer cells and then mount an intensified attack against them.

Possible Experimental Use in Mesothelioma Treatment

Pharmaceutical giant Merck of Kenilworth, New Jersey, markets pembrolizumab under the brand name Keytruda. The FDA approved it for patients with metastatic non-small cell lung cancer, but not mesothelioma.

However, because non-small cell lung cancer and mesothelioma are related diseases, some mesothelioma doctors might choose to prescribe pembrolizumab on an experimental basis for their mesothelioma patients in order to investigate how it works for them.

For now then, Merck is touting pembrolizumab as the first and only anti-PD-1 therapy approved for both squamous and non-squamous metastatic non-small cell lung cancer.

As approved by the FDA, pembrolizumab is administered in conjunction with platinum-containing chemotherapy. Pembrolizumab can be given either during or after chemotherapy, according to Merck.

The critical determinant of whether a patient gets pembrolizumab at all is the presence of tumors that express PD-L1. Both non-small cell lung cancer and mesothelioma tumors generally have PD-L1 expression.

Patients for whom pembrolizumab is indicated receive a 2 mg/kg dose once every three weeks. However, Merck’s researchers have not yet been able to establish by how much this dose can extend survival or improve symptoms.

Good Results in Pembrolizumab Clinical Trial

In Merck’s most important clinical study on pembrolizumab leading up to FDA approval, researchers observed at least partial responses to the immunotherapy agent in 95 percent of patients.

Forty-one percent of patients who registered a PD-L1 expression tumor-proportion score of at least 50 percent experienced even stronger responses.

Of that 41 percent, the overwhelming majority — 84 percent — had durable responses, with some lasting longer than six months.

Pembrolizumab does have a drawback, however. Merck reported that it can cause the immune system to attack normal organs and tissues. Apparently, though, this is a rare occurrence, the company indicated.

The most commonly noted adverse reactions to the therapy were fatigue, cough, decreased appetite and dyspnea.

Even so, Merck official were understandably delighted by the FDA’s approval of pembrolizumab. They hailed the product as a reflection of the company’s “deep commitment to bring the benefits of immunotherapy to cancer patients.”

The president of Merck Research Laboratories, Dr. Roger M. Perlmutter, indicated that pembrolizumab was the result of scientific and medical efforts from around the world. Merck said it is now conducting multiple Phase 3 clinical studies in advanced non-small cell lung cancer.

In addition to pembrolizumab, Merck also secured approval for a companion diagnostic tool, said to be the first okayed by the FDA to let physicians chart PD-L1 expression in a patient’s tumor.

The diagnostic tool is made by Dako North America, Inc., an Agilent Technologies company. It is marketed under the name PD-L1 IHC 22C3 pharmDx.