Mirati Therapeutics has reported positive preliminary data from a Phase I/II clinical trial of its investigational drug, MRTX849, for the treatment of solid tumours expressing KRAS G12C mutations.

Results showed clinical activity, including objective responses, with the treatment of non-small cell lung cancer (NSCLC) and colorectal cancer (CRC) patients.

The maximum tolerated dose (MTD) of the drug has not been determined. Dose expansion and patient enrolment are ongoing.

Mirati Therapeutics president and CEO Charles Baum said: “Patients whose tumours carry the KRAS G12C mutation have a poor prognosis, are resistant to standard of care treatment and have no available targeted therapeutic options.

“Early efficacy and safety data from this Phase I/II trial demonstrate the potential of a potent and effective KRAS therapy. We look forward to investigating MRTX849 in patients with a variety of KRAS G12C mutated cancers and bringing the hope of a targeted therapy to them.”

MRTX849 is an oral small molecule intended for the selective inhibition of a form of KRAS bearing a substitution mutation (G12C).

The company noted that KRAS G12C mutations are found in nearly 14% of NSCLC adenocarcinoma patients and 4% of colorectal cancer patients, among other cancer types.

The open-label, multi-centre trial evaluated 150mg, 300mg, 600mg and 1,200mg once-daily doses of MRTX849, as well as a 600mg twice-daily dose.

It enrolled a total of 17 patients, consisting of ten with NSCLC, four suffering from CRC, and three with other tumour types.

Of the 12 evaluable participants, three of five with NSCLC and one of two with CRC had a partial response with 600mg. The remaining patients achieved stable disease (SD).

In addition, three of six NSCLC patients and one of four with CRC experienced a partial response across all dose levels. The treatment-related adverse events (AEs) observed during the study were primarily grade 1 events.