AbbVie's lung cancer drug shows promise in first trial

NORTH CHICAGO - AbbVie Inc.'s experimental drug Rova-T showed promise in treating patients with an aggressive form of lung cancer in an early trial, a finding that may help investors gain confidence in the company's decision to acquire Stemcentrx Inc., the biotechnology firm that developed the treatment.

In the first clinical trial of the drug in humans, 68 percent of patients' tumors stopped growing, including 18 percent whose tumors shrank, according to data on 60 people whose cancer had progressed after one or more previous courses of therapy. The results were presented Sunday at the annual meeting of the American Society for Clinical Oncology in Chicago.

The effect was more pronounced in patients who expressed more of the protein marker known as DLL3 that's targeted by the drug. In the 26 patients with high levels of DLL3 expression, 89 percent of tumors stopped growing and 39 percent were reduced in size, according to a statement from Memorial Sloane Kettering Cancer Center, whose researcher Charles Rudin led the study.

"The most exciting thing about this therapeutic is the fact that it's the first time in small cell lung cancer that we have a predictive biomarker, one that we can associate with a higher probability of response to the drug," Rudin said in a telephone interview. He cautioned the results were early, in small numbers of patients, and would need to be verified in larger trials.

Survival Rates

Four patients who had failed two prior therapies were still alive more than six months after treatment, including two who lived for at least 18 months, according to the statement. With the only approved drug for the recurrent disease, a form of chemotherapy called topotecan, median overall survival is seven months, according to Tony Butler, an analyst at Guggenheim Partners.

AbbVie said on April 28 that it would buy Stemcentrx for $5.8 billion, a price that some analysts said at the time might be too high. The acquisition was completed on June 1.

The California biotech firm has focused on cancer stem cells, searching for protein markers they express. Rova-T is an antibody drug conjugate, a type of treatment where one part latches onto a specific marker on the tumor, delivering a toxic payload once it enters the cell.

"Cancer stem cells initiate cancer and drive recurrence," said Brian Slingerland, chief executive officer of Stemcentrx. In theory, targeting stem cells could help ensure that malignancies are eradicated and that the cancer won't come back.

Protein Marker

Stemcentrx identified the DLL3 marker, which is found in 80 percent of tumors of small cell lung cancer patients and, critically, isn't present on normal tissue. The drug's toxicity is "manageable," according to the Sloan Kettering statement, with the main side effects being inflammation and fluid accumulation, low platelet count and rash.

The inflammation and fluid accumulation is "an unusual toxicity," Sloan Kettering's Rudin said. Still, he said he wasn't very concerned because the effect was largely reversed by anti-inflammatory agents and corresponded with the highest dosage levels, which won't be used in future trials.

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To contact the reporter on this story: Caroline Chen in San Francisco at cchen509bloomberg.net To contact the editors responsible for this story: Drew Armstrong at darmstrong17bloomberg.net Stephen West, Cecile Daurat