[Corrected 1:38 pm. See below.] Shares of San Diego-based Mirati Therapeutics fell 15 percent Monday as data from an ongoing mid-stage study of one of its experimental cancer drugs disappointed investors.
Mirati (NASDAQ: MRTX) is one of several biotech companies trying to get in on the mix-and-match cancer immunotherapy game. Drugmakers have been combining immunotherapies with other medicines hoping to help more patients respond, and that has led to a slew of deals and alliances to test various regimens in clinical trials. Results so far have been mixed.
Mirati, for instance, has been testing sitravatinib (MGCD516) in combination with nivolumab (Opdivo), an immunotherapy from Bristol-Myers Squibb (NYSE: BMY). The two have been running a Phase 2 study in patients with non-small cell lung cancer (NSCLC), which makes up about 85 percent of lung cancer cases. While immunotherapy has already begun to change how lung cancer is treated, not everyone responds to treatment and there is room for improvement. Bristol and Mirati are specifically targeting people who saw their cancer worsen after immunotherapy—one of the most challenging clinical scenarios for advanced lung cancer, said Ticiana Leal, who leads the thoracic oncology program at the University of Wisconsin, in a statement. Leal presented the data at the European Society For Medical Oncology’s annual meeting in Munich, Germany.
In the statement, Leal said the results were encouraging based on patient responses and the combination’s “favorable” safety profile. Most side effects seen were mild to moderate.
Nonetheless, shares fell from about $40 per share to about $30 apiece after the release of the data, which “fell somewhat short of [Wall Street’s] expectations,” wrote Jefferies analyst Maury Raycroft. Shares closed Monday at about $34, 15 percent below the previous day’s close. Overall, 16 of 56 evaluable patients (29 percent) on the drug combination responded to treatment, and those responses have lasted a median of over nine months, Mirati said. But the responses for roughly half of those patients (seven of 16) were unconfirmed, the company said. [An earlier version of this paragraph misstated the number of patients whose responses were unconfirmed.] Five won’t be confirmed because patients left the study, and another two are awaiting confirmation, Raycroft wrote.
Still, Mirati will press forward. It plans to start a Phase 3 study in NSCLC that will compare a regimen of sitravatinib and immunotherapy to chemotherapy (docetaxel) in patients who have already failed both immunotherapy and chemotherapy. Citing FDA guidance, the company said it will analyze patients’ overall response rate part way through the trial to see if the combination qualifies for “accelerated” approval, on a thinner body of evidence than the agency typically requires. The trial should start in the first half of 2019.
In the statement, Mirati president and CEO Charles Baum said the company believes the Phase 3 study “will demonstrate a greater response rate and overall survival” than the 7 to 11 percent response rate docetaxel has historically shown for these patients.