CRS-207 Phase 1B Results Show Strong Response Against Mesothelioma

The developer of the mesothelioma immunotherapy drug CRS-207 has revealed final numbers from its Phase 1 clinical trial. They are very encouraging.

Fifty-nine percent of the patients who received CRS-207 along with standard mesothelioma chemotherapy experienced a response. The response rate to mesothelioma chemotherapy without CRS-207 was only about half that number.

Even better, disease control was seen in 90 percent of those who responded to the combination of CRS-207 and mesothelioma chemotherapy.

CRS-207’s developer announced these findings in mid-April at the European Lung Cancer Conference (ELCC) held in Geneva, Switzerland.

Drug Seeks Protein Expressed by Mesothelioma

CRS-207 is a live, attenuated Listeria monocytogenes bacterium. It is engineered to include a pair of gene deletions. These deletions prevent the Listeria bacterium from being harmful to host humans.

The engineering of this Listeria bacterium includes tweaks that cause it to trigger an anti-mesothelin response and cellular tumor-specific immunity in patients with mesothelioma.

This anti-mesothelin response occurs because the modified bacterium has been endowed with a strong affinity for cells that express mesothelin antigen. Mesothelioma cells express that antigen in quantity.

Data have suggested that CRS-207 works synergistically with chemotherapy drug cocktails consisting of pemetrexed and a platinum agent such as cisplatin.

In the recently concluded Phase1B trial of CRS-207, the developer tried it out on patients diagnosed with advanced unresectable mesothelioma but who still were candidates for chemotherapy.

Determining Results from Mesothelioma Clinical Trial

The developer found 38 mesothelioma patients who filled the bill. They were given two infusions of CRS-207 — spaced two weeks apart — along with the chemotherapy cocktail.

The chemotherapy drugs were given in as many as six cycles that were three weeks apart. After the final cycle, another two rounds of CRS-207 infusions were administered. But, this time, they were spaced three weeks apart.

Then, after eight weeks, the patients were given maintenance doses of CRS-207. The maintenance doses were administered every eight weeks after that until the mesothelioma recurred. Patients received periodic medical follow-up that continued for a maximum of 28 months.

According to the developer, “Patients receiving the combination of CRS-207 and chemotherapy had a deep response, with more than 90 percent disease control.”

A few side effects were noted by the developers during the clinical trial. The main ones were fever and rigors. However, the developers said those lasted only a day at most.

The developers added they thought the side effects were spurred by the infusion procedure itself rather than the CRS-207.

Later, immunohistochemistry analysis was performed on three of the mesothelioma patients. CRS-207 and the mesothelioma chemotherapy combination in those three were found to have boosted recruitment and expansion of leukocytes.

That was good news because the leukocytes recruited and expanded were those capable of infiltrating the mesothelioma tumors. There also were increases in infiltrating CD8+ cells, macrophages and natural killer cells.

Mesothelioma Trial Results Shared at ELCC Conference

The developers used the occasion of their ELCC presentation to outline plans for further CRS-207 clinical trials. The first of those is expected to begin later this year.

Using the ELCC as a forum to share the CRS-207 clinical trial results was helpful because it’s a major event for researchers and clinicians involved in fighting lung cancers of all types, not just mesothelioma.

The ELCC is an annual event sponsored chiefly by the European Society for Medical Oncology and by the International Association for the Study of Lung Cancer. It draws an attendance of roughly 2,000 specialists from around the globe.

The European Society for Medical Oncology is considered a preeminent cancer organization. More than 14,000 medical oncologists and others in related fields from more than 130 countries belong to it.

The International Association for the Study of Lung Cancer was founded in 1974. Its membership includes some 5,000 lung cancer specialists from more than 100 countries.

The developer of CRS-207 is Aduro Biotech, Inc. of Berkeley, California. Aduro Biotech focuses on discovering and bringing to market therapies that work hand-in-glove with the human immune system.