A phase II randomized trial of cobimetinib plus chemotherapy, with or without atezolizumab, as first-line treatment for patients with locally advanced or metastatic triple-negative breast cancer (COLET): primary analysis.

BACKGROUND: Resistance to standard chemotherapy in metastatic triple-negative breast cancer (mTNBC) is associated with upregulation of the mitogen-activated protein kinase (MAPK) pathway. Cobimetinib, an MAPK/extracellular signal-regulated kinase (MEK) inhibitor, may increase sensitivity to taxanes and programmed death-ligand 1 inhibitors. COLET is a three-cohort phase II study evaluating first-line cobimetinib plus chemotherapy, with or without atezolizumab, in patients with locally advanced or mTNBC. PATIENTS AND METHODS: Patients were ≥18 years with locally advanced or mTNBC. Following a safety run-in, patients in cohort I were randomized 1:1 to cobimetinib (60 mg, D3-D23 of each 28-day cycle) or placebo, plus paclitaxel (80 mg/m2, D1, 8, and 15). Additional patients were randomized (1:1) to cohort II or III to receive cobimetinib plus atezolizumab (840 mg, D1 and D15) and either paclitaxel (cohort II) or nab-paclitaxel [cohort III (100 mg/m2, D1, D8, and D15)]. Primary endpoints were investigator-assessed progression-free survival (PFS) (cohort I) and confirmed objective response rate (ORR) (cohorts II/III). Safety and tolerability were also assessed. RESULTS: In the expansion stages, median PFS was 5.5 months for cobimetinib/paclitaxel versus 3.8 months for placebo/paclitaxel in cohort I [hazard ratio 0.73; 95% confidence interval (CI) 0.43-1.24; P = 0.25]. In cohort I, ORR was 38.3% (95% CI 24.40-52.20) for cobimetinib/paclitaxel and 20.9% (95% CI 8.77-33.09) for placebo/paclitaxel; ORRs in cohorts II and III were 34.4% (95% CI 18.57-53.19) and 29.0% (95% CI 14.22-48.04), respectively. Diarrhea was the most common grade ≥3 adverse events across all cohorts. CONCLUSIONS: Cobimetinib added to paclitaxel did not lead to a statistically significant increase in PFS or ORR, although a nonsignificant trend toward a numerical increase was observed. Cobimetinib plus atezolizumab and a taxane did not appear to increase ORR. This demonstrates the potential activity of a combinatorial MEK inhibitor, chemotherapy, and immunotherapy in this difficult-to-treat population.

Prognostic impact of baseline tumour immune infiltrate on disease-free survival in patients with completely resected, BRAFv600 mutation-positive melanoma receiving adjuvant vemurafenib.

BACKGROUND: We conducted a retrospective exploratory analysis to evaluate the effects of baseline tumour immune infiltrate on disease-free survival (DFS) outcomes in patients with fully resected stage IIC-IIIC melanoma receiving adjuvant vemurafenib monotherapy or placebo in the BRIM8 study. PATIENTS AND METHODS: BRIM8 was a phase III, international, double-blind, randomised, placebo-controlled study. Eligible patients with BRAFV600 mutation-positive, completely resected melanoma were randomly assigned to oral vemurafenib (960 mg twice daily) or matching placebo for 52 weeks. The primary end point was DFS. The association of CD8+ T-cell infiltration and programmed death ligand 1 (PD-L1) expression with DFS, as measured by immunohistochemistry, was explored retrospectively. RESULTS: Four hundred ninety-eight patients were randomly assigned to receive adjuvant vemurafenib (n = 250) or placebo (n = 248); tumour samples were available for biomarker analysis for approximately 60% of patients. In the pooled biomarker population, placebo-treated patients with <1% CD8+ T cells in the tumour centre had shorter median DFS than those with ≥1% CD8+ T cells (7.7 versus 47.8 months). DFS benefit from vemurafenib versus placebo was greater in patients with <1% CD8+ T cells [hazard ratio (HR) 0.56; 95% confidence interval (CI) 0.34-0.92) than in patients with ≥1% CD8+ T cells (HR 0.77; 95% CI 0.48-1.22). Likewise, median DFS was shorter among placebo-treated patients with <5% versus ≥5% PD-L1+ immune cells (IC) in the tumour (7.2 versus 47.8 months). A greater DFS benefit with vemurafenib versus placebo was observed in patients with <5% PD-L1+IC (HR 0.36; 95% CI 0.24-0.56) than in patients with ≥5% PD-L1+IC (HR 0.99; 95% CI 0.58-1.69). CONCLUSIONS: The presence of CD8+ T cells and PD-L1+IC are favourable prognostic factors for DFS. Treatment with adjuvant vemurafenib may overcome the poor DFS prognosis associated with low CD8+ T-cell count or PD-L1 expression. CLINICALTRIALS. GOV IDENTIFIER: NCT01667419.

FAIRLANE, a double-blind placebo-controlled randomized phase II trial of neoadjuvant ipatasertib plus paclitaxel for early triple-negative breast cancer.

BACKGROUND: This hypothesis-generating trial evaluated neoadjuvant ipatasertib-paclitaxel for early triple-negative breast cancer (TNBC). PATIENTS AND METHODS: In this randomized phase II trial, patients with early TNBC (T ≥ 1.5 cm, N0-2) were randomized 1 : 1 to receive weekly paclitaxel 80 mg/m2 with ipatasertib 400 mg or placebo (days 1-21 every 28 days) for 12 weeks before surgery. Co-primary end points were pathologic complete response (pCR) rate (ypT0/TisN0) in the intention-to-treat (ITT) and immunohistochemistry phosphatase and tensin homolog (PTEN)-low populations. Secondary end points included pCR rate in patients with PIK3CA/AKT1/PTEN-altered tumors and pre-surgery response rates by magnetic resonance imaging (MRI). RESULTS: pCR rates with ipatasertib versus placebo were 17% versus 13%, respectively, in the ITT population (N = 151), 16% versus 13% in the immunohistochemistry PTEN-low population (N = 35), and 18% versus 12% in the PIK3CA/AKT1/PTEN-altered subgroup (N = 62). Rates of overall and complete response (CR) by MRI favored ipatasertib in all three populations (CR rate 39% versus 9% in the PIK3CA/AKT1/PTEN-altered subgroup). Ipatasertib was associated with more grade ≥3 adverse events (32% versus 16% with placebo), especially diarrhea (17% versus 1%). Higher cycle 1 day 8 (C1D8) immune score was significantly associated with better response only in placebo-treated patients. All ipatasertib-treated patients with low immune scores and a CR had PIK3CA/AKT1/PTEN-altered tumors. CONCLUSIONS: Adding ipatasertib to 12 weeks of paclitaxel for early TNBC did not clinically or statistically significantly increase pCR rate, although overall response rate by MRI was numerically higher with ipatasertib. The antitumor effect of ipatasertib was most pronounced in biomarker-selected patients. Safety was consistent with prior experience of ipatasertib-paclitaxel. A T-cell-rich environment at C1D8 had a stronger association with improved outcomes in paclitaxel-treated patients than seen for baseline tumor-infiltrating lymphocytes. This dependency may be overcome with the addition of AKT inhibition, especially in patients with PIK3CA/AKT1/PTEN-altered tumors. CLINICALTRIALS.GOV: NCT02301988.

Phase Ib study of atezolizumab combined with cobimetinib in patients with solid tumors.

BACKGROUND: Preclinical evidence suggests that MEK inhibition promotes accumulation and survival of intratumoral tumor-specific T cells and can synergize with immune checkpoint inhibition. We investigated the safety and clinical activity of combining a MEK inhibitor, cobimetinib, and a programmed cell death 1 ligand 1 (PD-L1) inhibitor, atezolizumab, in patients with solid tumors. PATIENTS AND METHODS: This phase I/Ib study treated PD-L1/PD-1-naive patients with solid tumors in a dose-escalation stage and then in multiple, indication-specific dose-expansion cohorts. In most patients, cobimetinib was dosed once daily orally for 21 days on, 7 days off. Atezolizumab was dosed at 800 mg intravenously every 2 weeks. The primary objectives were safety and tolerability. Secondary end points included objective response rate, progression-free survival, and overall survival. RESULTS: Between 27 December 2013 and 9 May 2016, 152 patients were enrolled. As of 4 September 2017, 150 patients received ≥1 dose of atezolizumab, including 14 in the dose-escalation cohorts and 136 in the dose-expansion cohorts. Patients had metastatic colorectal cancer (mCRC; n = 84), melanoma (n = 22), non-small-cell lung cancer (NSCLC; n = 28), and other solid tumors (n = 16). The most common all-grade treatment-related adverse events (AEs) were diarrhea (67%), rash (48%), and fatigue (40%), similar to those with single-agent cobimetinib and atezolizumab. One (<1%) treatment-related grade 5 AE occurred (sepsis). Forty-five (30%) and 23 patients (15%) had AEs that led to discontinuation of cobimetinib and atezolizumab, respectively. Confirmed responses were observed in 7 of 84 patients (8%) with mCRC (6 responders were microsatellite low/stable, 1 was microsatellite instable), 9 of 22 patients (41%) with melanoma, and 5 of 28 patients (18%) with NSCLC. Clinical activity was independent of KRAS/BRAF status across diseases. CONCLUSIONS: Atezolizumab plus cobimetinib had manageable safety and clinical activity irrespective of KRAS/BRAF status. Although potential synergistic activity was seen in mCRC, this was not confirmed in a subsequent phase III study. CLINICALTRIALS.GOV IDENTIFIER: NCT01988896 (the investigators in the NCT01988896 study are listed in the supplementary Appendix, available at Annals of Oncology online).

A role for FOXO1 in BCR-ABL1-independent tyrosine kinase inhibitor resistance in chronic myeloid leukemia.

Chronic myeloid leukemia (CML) patients who relapse on imatinib due to acquired ABL1 kinase domain mutations are successfully treated with second-generation ABL1-tyrosine kinase inhibitors (ABL-TKIs) such as dasatinib, nilotinib or ponatinib. However, ~40% of relapsed patients have uncharacterized BCR-ABL1 kinase-independent mechanisms of resistance. To identify these mechanisms of resistance and potential treatment options, we generated ABL-TKI-resistant K562 cells through prolonged sequential exposure to imatinib and dasatinib. Dual-resistant K562 cells lacked BCR-ABL1 kinase domain mutations, but acquired other genomic aberrations that were characterized by next-generation sequencing and copy number analyses. Proteomics showed that dual-resistant cells had elevated levels of FOXO1, phospho-ERK and BCL-2, and that dasatinib no longer inhibited substrates of the PI3K/AKT pathway. In contrast to parental cells, resistant cells were sensitive to growth inhibition and apoptosis induced by the class I PI3K inhibitor, GDC-0941 (pictilisib), which also induced FOXO1 nuclear translocation. FOXO1 was elevated in a subset of primary specimens from relapsed CML patients lacking BCR-ABL1 kinase domain mutations, and these samples were responsive to GDC-0941 treatment ex vivo. We conclude that elevated FOXO1 contributes to BCR-ABL1 kinase-independent resistance experienced by these CML patients and that PI3K inhibition coupled with BCR-ABL1 inhibition may represent a novel therapeutic approach.