A higher dose leads to tumor shrinkage in colorectal cancer patients.

The KRAS gene is an important one. When it is functioning properly, it controls cell proliferation. When mutated, the “off” switch is broken and cells continuously grow, often leading to cancer. Amgen is the first company developing a KRAS inhibitor to report clinical data.

In a phase I study reported previously, its drug AMG 510 shrank lung tumors in five of 10 non-small cell lung cancer patients and stopped the growth of tumors in another four patients. It also stopped the growth of colorectal tumors in nearly 75% of the patients participating in the study. The latter patients received the lowest doses of the drug, so it may be more effective at higher doses. In a recent update on the study, Amgen said AMG 510 did indeed shrink tumors in patients with colorectal cancer and cancer of the appendix when given at higher doses.

According to one analyst, there is a potential multi-billion darker market for the KRAS inhibitor.

The phase I study investigated the use of AMG 510 as a single agent for patients that had no additional treatment options. Amgen is now considering investigating its use as an earlier treatment option and in combination with other drugs, including checkpoint inhibitors.