Lung cancer Illustration: VCG

An experimental Amgen Inc drug that targets a specific genetic mutation shrank tumors in 32 percent of advanced lung cancer patients and 7 percent of those with colon cancer, according to data from an early-stage trial presented on Sunday.

The median length of time that patients given the drug sotorasib lived before their disease worsened was 6.3 months for lung cancer patients and 4 months for colorectal cancer patients, the company said. Participants in the 129-patient study were followed for a median of 11.7 months.

Patients in the Phase I trial involving several types of cancer were treated with once daily sotorasib. The oral medication is designed to target a mutated form of a gene known as KRAS that occurs in about 13 percent of non-small cell lung cancers (NSCLC), the most common type of lung cancer.

The KRAS mutation is also found in 1 percent to 3 percent of colorectal and other cancers. Sotorasib is part of a growing trend of precision medicines that target gene mutations driving cancer regardless of which organ the disease originated.

Out of 59 NSCLC patients, 32 percent had a partial response to the drug - tumor shrinkage by at least 30 percent - and 88 percent had either a lesser response or stable disease. For the 42 patients with colorectal cancer, 7 percent had tumor shrinkage and 74 percent had stable disease.

"These are patients that have very few options," said Gregory Friberg, Amgen's head of oncology global development. "They were on a third or fourth line of therapy."

The company expects by the end of 2020 to have results from a mid-stage lung cancer trial that could be used to seek US approval of sotorasib.

Analysts are keen to see how rival KRAS drugs, including data expected later in 2020 from Mirati Therapeutics Inc, will stack up against sotorasib.

Researchers, who presented the Amgen data at a virtual meeting of the European Society for Medical Oncology, said responses were also seen with pancreatic, endometrial, and appendix cancers and melanoma.

Adverse side effects occurred in about 12 percent of trial patients, researchers reported.

Amgen is also testing the drug in combination with other medications, including Merck & Co's immunotherapy Keytruda.