Mesothelioma patients may see a potential new treatment option in another drug that targets and kills cancer stem cells.
Drugmaker Verastem Inc. this month announced the U.S. Food and Drug Administration (FDA) granted VS-5584, a drug that can reduce cancer stem cells efficiently, an orphan drug designation for mesothelioma. Last month, the drug received similar status in Europe.
“We look forward to taking full advantage of the opportunities in order to bring this potential new treatment option to patients as rapidly as possible,” Verastem CEO Robert Forrester said. “This is an important regulatory milestone.”
While Forrester announced the FDA’s orphan drug approval, the federal regulatory agency has not released an official confirmation on VS-5584.
“FDA cannot confirm the existence of or comment on any current/pending product applications,” agency spokeswoman Lyndsay Meyer said.
“The FDA is only able to provide information on approved drug product applications.”
The FDA grants orphan drug designation to products that treat a rare disease or condition when requested by the manufacturer. The drug and condition must meet certain criteria. The designation often helps the development of experimental drugs for rare cancers by giving the manufacturer exclusivity for an extended period and critical tax credits.
Mesothelioma is a rare disease caused by prolonged exposure to asbestos.
Stem Cells Are Key to Cancers
Although cancer stem cells comprise only a small portion of cells in a tumor, they are the underlying cause of metastasis and tumor recurrence with mesothelioma. They also are a major cause of tumor resistance, which allows the cancer to survive and grow despite chemotherapy.
Currently, VS-5584 is part of two clinical trials involving mesothelioma patients. One involves patients with progressive or relapsed mesothelioma, and it is used in combination with VS-6063 (defactinib), another stem cell drug marketed by Verastem and already proven to be effective.
The two-drug combination clinical trial stems from the synergistic activity shown earlier in preclinical work in the laboratory and in animal subject.
A phase I trial on a variety of advanced solid tumors, including mesothelioma, also is testing VS-5584 independently. Scottsdale (AR) Healthcare Center, Cedars-Sinai Medical Center in Los Angeles, Memorial Sloan Kettering Cancer Center in New York and Tennessee Oncology (Nashville) are conducting that trial.
Early Returns Show Promise
VS-5588 alone has been well tolerated, and anti-cancer activity has been observed in the early reports, a company press release shows. Some of the patients have been observed for more than six months. A maximum tolerated dose has not been reached yet.
“We believe we have the opportunity to change the way cancer is treated and to make a significant difference in the lives of many patients,” Forrester said on a conference call earlier this year detailing Verastem’s plans for the future. “We’re onto something really important here.”
Verastem’s other trial using solely VS-6063 involves 55 sites covering 13 different countries. That drug also is being tested with ovarian and non-small-cell lung cancers.
The VS-5584 drug works by targeting a particular class of enzyme found within the stem cells. It has been shown to induce tumor regression in models previously resistant to chemotherapy.
VS-6063 works in similar fashion, but for a different enzyme. Both involve molecule inhibitors of signaling pathways that allow stem cells to proliferate. By inhibiting the pathways, the cancer loses its capacity to grow.
Some scientists also believe that chemotherapy alone, while initially shrinking a tumor, may increase the strength of stem cells.