Mirati Therapeutics Inc's experimental drug that targets a specific genetic mutation helped about one third of a small subset of patients in a clinical trial whose lung cancer had spread to their brains, the company said on Monday.
Early data show that out of 19 evaluated patients treated with adagrasib, three had complete resolution of central nervous system metastases, and three had partial tumor shrinkage, Mirati said ahead of a presentation in Chicago at the annual meeting of the American Society of Clinical Oncology.
At the median follow up of 6.6 months, another 10 of the patients achieved stabilization of brain metastases, the company said.
Serious side effects occurred in 36% of adagrasib patients.
The oral drug is designed to target a mutated form of a gene known as KRAS that occurs in about 13% of non-small cell lung cancers (NSCLC), the most common type of lung cancer.
"Roughly a third or more patients" with KRAS-mutated lung cancer will develop brain metastases, Mirati Chief Executive David Meek said in an interview.
Those patients have a median overall survival of around five months, according to Dr. Joshua Sabari, a researher on the trial and oncologist at NYU Langone Perlmutter Cancer Center in New York.
Mirati last week said overall results from the trial showed that adagrasib shrank tumors in 43% of 112 advanced lung cancer patients. However it also led to serious side effects, such as liver toxicity and anemia, in 46% of them, sending shares of the company sharply lower.
Mirati shares, which rose 10% on Friday to close at $44.33, are down about 70% so far this year.
Investors have been keen to assess how Mirati's drug stacks up against the first KRAS-targeting cancer drug, Amgen Inc's Lumakras, which was approved by the U.S. Food and Drug Administration last year.
The drugs are part of a growing trend of medicines that target specific gene mutations driving cancer regardless of which organ the disease originated.
The FDA is expected to make an approval decision on Mirati's drug for advanced NSCLC by mid-December.
California-based Mirati is also testing adagrasib as an initial treatment for NSCLC, both alone and in combination with Merck & Co's immunotherapy Keytruda.
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