The Trouble With KRAS


Mutations in the gene that encodes the KRAS protein are frequently encountered in various human cancers. They are found in about 30% of non-small cell lung cancers (NSCLCs), making KRAS the single most common gene mutated in this cancer. The rate of KRAS mutations in other cancers, such as pancreatic or colorectal, is even higher.

A mutant KRAS protein that is always in the “on” position activates many signaling pathways, many of which lead to unrestrained growth and proliferation of cancer cells. This makes KRAS an appealing treatment target. However, challenges abound, and researchers are exploring several different approaches to treating KRAS-mutant cancers.

Unlike mutations in proteins known as receptor tyrosine kinases, like EGFR or ALK, mutated KRAS is a very difficult protein to target with cancer drugs. (So much so that the National Institutes of Health (NIH) has undertaken a special effort to intensify the effort towards successful targeting of mutant KRAS, known as the RAS Initiative.) Continue reading…


MEK Inhibitor Disappoints in KRAS-Mutant NSCLC

Excerpt:

“A targeted combination therapy for patients with KRAS-mutant non-small cell lung cancer (NSCLC) did not improve overall survival (OS) or progression-free survival (PFS), researchers reported.

“The phase III, randomized SELECT-1 trial compared the experimental MEK inhibitor selumetinib, in combination with docetaxel (Taxotere), with docetaxel and placebo as second-line therapy in patients who failed a previous line of therapy, explained Pasi Jänne, MD, PhD, of the Dana Farber Cancer Institute in Boston, and colleagues.

“After a follow-up of approximately 1 year, median OS in the selumetinib combination group was 8.7 months versus 7.9 months in the docetaxel plus placebo group (hazard ratio 1.05, 95% CI 0.85-1.30, P=0.64), they wrote in JAMA.

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Possible Treatment on Horizon for Advanced KRAS-Mutant NSCLC

Excerpt:

“Promising early phase clinical trials have led to the initiation of the phase III JUNIPER trial, which is assessing abemaciclib (LY2835219) for patients with previously treated KRAS-mutant lung cancer, a traditionally hard to treat genetic subtype.

“JUNIPER is an open label phase III study currently recruiting patients with stage IV non–small cell lung cancer (NSCLC) with a detectable KRAS mutation who have progressed following treatment with platinum-based chemotherapy (NCT02152631). Patients will be randomized to receive either abemaciclib or erlotinib, both with best supportive care.

“ ‘KRAS mutations are common in patients with NSCLC, but there have been few clinical advances in our treatment for these patients,’ said investigator Jonathan W. Goldman, MD, of the Department of Medicine, Hematology/Oncology, member of the Signal Transduction and Therapeutics Program Area at UCLA’s Jonsson Comprehensive Cancer Center, who explored the drug in a phase I trial.”

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Efficacy of BET Bromodomain Inhibition in Kras-Mutant Non-Small Cell Lung Cancer

The recent discovery, in hematologic malignancies, that BET bromodomain inhibition impairs MYC expression and MYC transcriptional function established the rationale of targeting KRAS-driven NSCLC with BET inhibition. We performed functional assays to evaluate the effects of JQ1 in genetically defined NSCLC cells lines harboring KRAS and/or LKB1 mutations.

Bromodomain inhibition comprises a promising therapeutic strategy for KRAS mutant NSCLC with wild-type LKB1, via inhibition of MYC function.


Pooled Analysis of the Prognostic and Predictive Effects of KRAS Mutation Status and KRAS Mutation Subtype in Early-Stage Resected Non–Small-Cell Lung Cancer in Four Trials of Adjuvant Chemotherapy

We undertook this analysis of KRAS mutation in four trials of adjuvant chemotherapy (ACT) versus observation (OBS) to clarify the prognostic/predictive roles of KRAS in non–small-cell lung cancer (NSCLC).

KRAS mutation status is not significantly prognostic. The potential interaction in patients with codon-13 mutations requires validation. At this time, KRAS status cannot be recommended to select patients with NSCLC for ACT.


KRAS Mutation as the Biomarker of Response to Chemotherapy and EGFR-TKIs in Patients With Advanced Non-Small Cell Lung Cancer: Clues For Its Potential Use in Second-Line Therapy Decision Making

In patients with non-small cell lung cancer (NSCLC), knowledge of the epidermal growth factor receptor (EGFR) mutation status is fundamental for selecting the treatment involving EGFR-tyrosine kinase inhibitors (EGFR-TKIs). Little information is available regarding the response and progression-free survival (PFS) in platinum-based chemotherapy (CT) versus EGFR-TKIs in the presence or absence of KRAS mutation, particularly in patients without EGFR mutation…”