KRAS mutational subtype and copy number predict in vitro response of human pancreatic cancer cell lines to MEK inhibition.

BACKGROUND: To study the molecular mechanism regulating sensitivity to MEK inhibition in pancreatic cancer cell lines. METHODS: A growth inhibition assay determined sensitivity to MEK162 in a panel of 29 pancreatic cancer cell lines. For the same panel, KRAS mutational status and copy-number variation (CNV) was determine using PCR, array CGH and FISH. Two sensitive and two resistant cell lines were further interrogated for difference in baseline and MEK162-induced gene expression, as well as signal transduction using microarray and western blotting. Cell cycle and apoptosis analysis was measured by flow cytometry. RESULTS: We report a strong correlation between both specific KRAS mutational subtype and CNV, and sensitivity to MEK inhibition. Cell lines with a KRAS (V12) mutation and KRAS gains or loss (n=7) are ∼10 times more resistant than those having neither a KRAS (V12) mutation nor KRAS CNV (n=14). Significant differences in baseline and MEK162-induced gene expression exist between the sensitive and resistant lines, especially in genes involved in RAS, EGF receptor and PI3K pathways. This was further supported by difference in signal transduction. MEK 162 blocked ERK1/2, as well as inhibited PI3K and S6 and increased p27KIP1 levels in the sensitive lines. CONCLUSIONS: Given the potency of MEK162, it may be a promising new therapy for patients with pancreatic cancer and KRAS mutational subtypes, and CNV may serve as important biomarkers for selecting patients that benefit from MEK-targeting based on these preclinical data.

Transient MEK inhibitor-associated retinopathy in metastatic melanoma.

BACKGROUND: Melanoma is one of the most aggressive skin cancers. Recently, selective MEK inhibitors have shown efficacy in patients with advanced BRAF- and NRAS-mutant melanoma. Soon after the initiation of clinical oncology trials with MEK inhibitors, it was observed that some participants developed an eye condition resembling central serous chorioretinopathy. The present article addresses the clinical features and management of these MEK inhibitor-associated retinal syndromes. PATIENTS AND METHODS: Thirty-two patients with advanced cutaneous melanoma were treated with the selective MEK inhibitor binimetinib (MEK162) in three different Phase 1b or 2 clinical trials. Twenty patients on binimetinib monotherapy and 12 on binimetinib plus RAF inhibitor [pan-kinase RAF inhibitor RAF265 (n = 7) or selective BRAF inhibitor encorafenib (LGX818) (n = 5)] combination therapy underwent ophthalmological examinations at regular intervals, including determination of best corrected visual acuity, perimetry, colour vision testing, dilated fundus examination, and multimodal imaging. RESULTS: Grade 1-2 bilateral retinopathies with multiple lesions were observed in 13 of 20 patients on binimetinib monotherapy, 4 of 7 patients on binimetinib plus RAF265 combination therapy, and 2 of 5 patients on binimetinib plus encorafenib combination therapy. In this study population, the rate ranged from 40% to 65%. Retinopathy events appeared during the first 4 weeks, and in some cases, during the first few days of treatment. Patients reported mild and only short-lived visual symptoms. Optical coherence tomography revealed neuroretinal elevations. Central retinal thickness and volume showed dose-dependent increases after the start of treatment, followed by a marked decrease despite continued treatment, which was associated with symptom resolution. No vascular abnormalities were found with fluorescein and indocyanine green angiography. CONCLUSIONS: Treatment with the selective MEK inhibitor binimetinib as a single agent or in combination with RAF inhibitors induced transient retinopathy with multiple bilateral lesions in some patients. Binimetinib-induced retinopathy was usually mild, self-limiting, and tolerable as visual function was not seriously impaired.

Efficacy according to biomarker status of cetuximab plus FOLFOX-4 as first-line treatment for metastatic colorectal cancer: the OPUS study.

BACKGROUND: The randomized phase II OPUS (Oxaliplatin and Cetuximab in First-Line Treatment of Metastatic Colorectal Cancer) study showed that tumor KRAS mutation status was predictive for outcome in patients receiving cetuximab plus FOLFOX-4 (oxaliplatin/5-fluorouracil/folinic acid) as first-line therapy for metastatic colorectal cancer (mCRC). PATIENTS AND METHODS: The biomarker analysis was extended through the use of additional DNA samples extracted from stained tissue sections. KRAS and BRAF tumor mutation status was determined for new (and for BRAF, existing) samples using a PCR technique. Clinical outcome was reassessed according to mutation status. Overall survival data are presented. RESULTS: Of 315 KRAS evaluable patient samples (93%), 179 tumors (57%) were KRAS wild type. Eleven of 309 (4%) KRAS/BRAF evaluable tumors (all KRAS wild type) carried BRAF mutations. The addition of cetuximab to FOLFOX-4 significantly improved progression-free survival (hazard ratio 0.567, P = 0.0064) and response (odds ratio 2.551, P = 0.0027) in patients with KRAS wild-type tumors. A favorable effect on survival was also observed. CONCLUSIONS: These results confirm the efficacy of cetuximab plus FOLFOX-4 in the first-line treatment of patients with KRAS wild-type mCRC and confirm KRAS mutation status as an effective predictive biomarker. The small number of tumors with BRAF mutations precluded the drawing of definitive conclusions concerning the predictive or prognostic utility of this biomarker.

Cetuximab in combination with weekly 5-fluorouracil/folinic acid and oxaliplatin (FUFOX) in untreated patients with advanced colorectal cancer: a phase Ib/II study of the AIO GI Group.

BACKGROUND: This two-part phase Ib/II study investigated the feasibility of administering cetuximab in combination with oxaliplatin and infusional 5-fluorouracil (5-FU)/folinic acid (FA) in a weekly schedule (AIO FUFOX protocol) as first-line treatment in patients with epidermal growth factor receptor-detectable advanced colorectal cancer. PATIENTS AND METHODS: Cetuximab was administered weekly: 400 mg/m(2) initial dose, then 250 mg/m(2) and FUFOX: oxaliplatin 50 mg/m(2), FA 500 mg/m(2) and 5-FU as a 24-h infusion at either 1500 or 2000 mg/m(2) administered for 4 weeks followed by a 1-week rest (one cycle). RESULTS: Dose-limiting toxicity (grade 3 diarrhea) occurred in 3 of 14 assessable patients receiving 5-FU at standard 2000 mg/m(2). This dose was administered to a further 25 patients. Cetuximab combined with FUFOX was generally well tolerated with the most common grade 3/4 adverse events being diarrhea (27%) and paresthesia (16%). The confirmed response rate for patients receiving 5-FU at standard 2000 mg/m(2) (N = 41) was 56%, with a median duration of 9.3 months. Median progression-free and overall survival times including all 49 patients were 8.1 (95% confidence interval 6.0-9.7) and 28.2 months, respectively. Cetuximab pharmacokinetics seemed not to be different for combination with FUFOX compared with cetuximab/irinotecan combinations. CONCLUSION: This protocol is well tolerated and shows promising efficacy supporting further investigation.