Matthew Wongchenko

Cobimetinib combined with vemurafenib in advanced BRAFV600-mutant melanoma (coBRIM): updated efficacy results from a randomised, double-blind, phase 3 trial

BACKGROUND The combination of cobimetinib with vemurafenib improves progression-free survival compared with placebo and vemurafenib in previously untreated patients with BRAF(V600)-mutant advanced melanoma, as previously reported in the coBRIM study. In this Article, we report updated efficacy results, including overall survival and safety after longer follow-up, and selected biomarker correlative studies. METHODS In this double-blind, randomised, placebo-controlled, multicentre study, adult patients (aged ≥18 years) with histologically confirmed BRAF(V600) mutation-positive unresectable stage IIIC or stage IV melanoma were randomly assigned (1:1) using an interactive response system to receive cobimetinib (60 mg once daily for 21 days followed by a 7-day rest period in each 28-day cycle) or placebo, in combination with oral vemurafenib (960 mg twice daily). Progression-free and overall survival were primary and secondary endpoints, respectively; all analyses were done on the intention-to-treat population. This study is registered with ClinicalTrials.gov, number NCT01689519, and is ongoing but no longer recruiting participants. FINDINGS Between Jan 8, 2013, and Jan 31, 2014, 495 eligible adult patients were enrolled and randomly assigned to the cobimetinib plus vemurafenib group (n=247) or placebo plus vemurafenib group (n=248). At a median follow-up of 14·2 months (IQR 8·5-17·3), the updated investigator-assessed median progression-free survival was 12·3 months (95% CI 9·5-13·4) for cobimetinib and vemurafenib versus 7·2 months (5·6-7·5) for placebo and vemurafenib (HR 0·58 [95% CI 0·46-0·72], p<0·0001). The final analysis for overall survival occurred when 255 (52%) patients had died (Aug 28, 2015). Median overall survival was 22·3 months (95% CI 20·3-not estimable) for cobimetinib and vemurafenib versus 17·4 months (95% CI 15·0-19·8) for placebo and vemurafenib (HR 0·70, 95% CI 0·55-0·90; p=0·005). The safety profile for cobimetinib and vemurafenib was tolerable and manageable, and no new safety signals were observed with longer follow-up. The most common grade 3-4 adverse events occurring at a higher frequency in patients in the cobimetinib and vemurafenib group compared with the vemurafenib group were γ-glutamyl transferase increase (36 [15%] in the cobimetinib and vemurafenib group vs 25 [10%] in the placebo and vemurafenib group), blood creatine phosphokinase increase (30 [12%] vs one [<1%]), and alanine transaminase increase (28 [11%] vs 15 [6%]). Serious adverse events occurred in 92 patients (37%) in the cobimetinib and vemurafenib group and 69 patients (28%) in the vemurafenib group. Pyrexia (six patients [2%]) and dehydration (five patients [2%]) were the most common serious adverse events reported in the cobimetinib and vemurafenib group. A total of 259 patients have died: 117 (47%) in the cobimetinib and vemurafenib group and 142 (58%) in the vemurafenib group. The primary cause of death was disease progression in most patients: 109 (93%) of 117 in the cobimetinib and vemurafenib group and 133 (94%) of 142 in the vemurafenib group. INTERPRETATION These data confirm the clinical benefit of cobimetinib combined with vemurafenib and support the use of the combination as a standard first-line approach to improve survival in patients with advanced BRAF(V600)-mutant melanoma. FUNDING F Hoffmann-La Roche-Genentech.

An inhibitor of KDM5 demethylases reduces survival of drug-tolerant cancer cells

The KDM5 family of histone demethylases catalyzes the demethylation of histone H3 on lysine 4 (H3K4) and is required for the survival of drug-tolerant persister cancer cells (DTPs). Here we report the discovery and characterization of the specific KDM5 inhibitor CPI-455. The crystal structure of KDM5A revealed the mechanism of inhibition of CPI-455 as well as the topological arrangements of protein domains that influence substrate binding. CPI-455 mediated KDM5 inhibition, elevated global levels of H3K4 trimethylation (H3K4me3) and decreased the number of DTPs in multiple cancer cell line models treated with standard chemotherapy or targeted agents. These findings show that pretreatment of cancer cells with a KDM5-specific inhibitor results in the ablation of a subpopulation of cancer cells that can serve as the founders for therapeutic relapse.

Evaluation and Clinical Analyses of Downstream Targets of the Akt Inhibitor GDC-0068

Purpose: The oncogenic PI3K/Akt/mTOR pathway is an attractive therapeutic target in cancer. However, it is unknown whether the pathway blockade required for tumor growth inhibition is clinically achievable. Therefore, we conducted pharmacodynamic studies with GDC-0068, an ATP competitive, selective Akt1/2/3 inhibitor, in preclinical models and in patients treated with this compound. Experimental Design: We used a reverse phase protein array (RPPA) platform to identify a biomarker set indicative of Akt inhibition in cell lines and human-tumor xenografts, and correlated the degree of pathway inhibition with antitumor activity. Akt pathway activity was measured using this biomarker set in pre- and post-dose tumor biopsies from patients treated with GDC-0068 in the dose escalation clinical trial. Results: The set of biomarkers of Akt inhibition is composed of 10 phosphoproteins, including Akt and PRAS40, and is modulated in a dose-dependent fashion, both in vitro and in vivo. In human-tumor xenografts, this dose dependency significantly correlated with tumor growth inhibition. Tumor biopsies from patients treated with GDC-0068 at clinically achievable doses attained a degree of biomarker inhibition that correlated with tumor growth inhibition in preclinical models. In these clinical samples, compensatory feedback activation of ERK and HER3 was observed, consistent with preclinical observations. Conclusion: This study identified a set of biomarkers of Akt inhibition that can be used in the clinical setting to assess target engagement. Here, it was used to show that robust Akt inhibition in tumors from patients treated with GDC-0068 is achievable, supporting the clinical development of this compound in defined patient populations. Clin Cancer Res; 19(24); 6976–86. ©2013 AACR.

Ipatasertib plus paclitaxel versus placebo plus paclitaxel as first-line therapy for metastatic triple-negative breast cancer (LOTUS): a multicentre, randomised, double-blind, placebo-controlled, phase 2 trial

BACKGROUND The oral AKT inhibitor ipatasertib is being investigated in cancers with a high prevalence of PI3K/AKT pathway activation, including triple-negative breast cancer. The LOTUS trial investigated the addition of ipatasertib to paclitaxel as first-line therapy for triple-negative breast cancer. METHODS In this randomised, placebo-controlled, double-blind, phase 2 trial, women aged 18 years or older with measurable, inoperable, locally advanced or metastatic triple-negative breast cancer previously untreated with systemic therapy were recruited from 44 hospitals in South Korea, the USA, France, Spain, Taiwan, Singapore, Italy, and Belgium. Enrolled patients were randomly assigned (1:1) to receive intravenous paclitaxel 80 mg/m2 (days 1, 8, 15) with either ipatasertib 400 mg or placebo once per day (days 1-21) every 28 days until disease progression or unacceptable toxicity. Randomisation was by stratified permuted blocks (block size of four) using an interactive web-response system with three stratification criteria: previous (neo)adjuvant therapy, chemotherapy-free interval, and tumour PTEN status. The co-primary endpoints were progression-free survival in the intention-to-treat population and progression-free survival in the PTEN-low (by immunohistochemistry) population. This ongoing trial is registered with ClinicalTrials.gov (NCT02162719). FINDINGS Between Sept 2, 2014, and Feb 4, 2016, 166 patients were assessed for eligibility and 124 patients were enrolled and randomly assigned to paclitaxel plus ipatasertib (n=62) or paclitaxel plus placebo (n=62). Median follow-up was 10·4 months (IQR 6·5-14·1) in the ipatasertib group and 10·2 months (6·0-13·6) in the placebo group. Median progression-free survival in the intention-to-treat population was 6·2 months (95% CI 3·8-9·0) with ipatasertib versus 4·9 months (3·6-5·4) with placebo (stratified hazard ratio [HR] 0·60, 95% CI 0·37-0·98; p=0·037) and in the 48 patients with PTEN-low tumours, median progression-free survival was 6·2 months (95% CI 3·6-9·1) with ipatasertib versus 3·7 months (1·9-7·3) with placebo (stratified HR 0·59, 95% CI 0·26-1·32, p=0·18). The most common grade 3 or worse adverse events were diarrhoea (14 [23%] of 61 ipatasertib-treated patients vs none of 62 placebo-treated patients), neutrophil count decreased (five [8%] vs four [6%]), and neutropenia (six [10%] vs one [2%]). No colitis, grade 4 diarrhoea, or treatment-related deaths were reported with ipatasertib. One treatment-related death occurred in the placebo group. Serious adverse events were reported in 17 (28%) of 61 patients in the ipatasertib group and nine (15%) of 62 patients in the placebo group. INTERPRETATION Progression-free survival was longer in patients who received ipatasertib than in those who received placebo. To our knowledge, these are the first results supporting AKT-targeted therapy for triple-negative breast cancer. Ipatasertib warrants further investigation for the treatment of triple-negative breast cancer. FUNDING F Hoffmann-La Roche.

Association of body-mass index and outcomes in patients with metastatic melanoma treated with targeted therapy, immunotherapy, or chemotherapy: a retrospective, multicohort analysis

BACKGROUND Obesity has been linked to increased mortality in several cancer types; however, the relation between obesity and survival outcomes in metastatic melanoma is unknown. The aim of this study was to examine the association between body-mass index (BMI) and progression-free survival or overall survival in patients with metastatic melanoma who received targeted therapy, immunotherapy, or chemotherapy. METHODS This retrospective study analysed independent cohorts of patients with metastatic melanoma assigned to treatment with targeted therapy, immunotherapy, or chemotherapy in randomised clinical trials and one retrospective study of patients treated with immunotherapy. Patients were classified according to BMI, following the WHO definitions, as underweight, normal, overweight, or obese. Patients without BMI and underweight patients were excluded. The primary outcomes were the associations between BMI and progression-free survival or overall survival, stratified by treatment type and sex. We did multivariable analyses in the independent cohorts, and combined adjusted hazard ratios in a mixed-effects meta-analysis to provide a precise estimate of the association between BMI and survival outcomes; heterogeneity was assessed with meta-regression analyses. Analyses were done on the predefined intention-to-treat population in the randomised controlled trials and on all patients included in the retrospective study. FINDINGS The six cohorts consisted of a total of 2046 patients with metastatic melanoma treated with targeted therapy, immunotherapy, or chemotherapy between Aug 8, 2006, and Jan 15, 2016. 1918 patients were included in the analysis. Two cohorts containing patients from randomised controlled trials treated with targeted therapy (dabrafenib plus trametinib [n=599] and vemurafenib plus cobimetinib [n=240]), two cohorts containing patients treated with immunotherapy (one randomised controlled trial of ipilimumab plus dacarbazine [n=207] and a retrospective cohort treated with pembrolizumab, nivolumab, or atezolizumab [n=331]), and two cohorts containing patients treated with chemotherapy (two randomised controlled trials of dacarbazine [n=320 and n=221]) were classified according to BMI as normal (694 [36%] patients), overweight (711 [37%]), or obese (513 [27%]). In the pooled analysis, obesity, compared with normal BMI, was associated with improved survival in patients with metastatic melanoma (average adjusted hazard ratio [HR] 0·77 [95% CI 0·66-0·90] for progression-free survival and 0·74 [0·58-0·95] for overall survival). The survival benefit associated with obesity was restricted to patients treated with targeted therapy (HR 0·72 [0·57-0·91] for progression-free survival and 0·60 [0·45-0·79] for overall survival) and immunotherapy (HR 0·75 [0·56-1·00] and 0·64 [0·47-0·86]). No associations were observed with chemotherapy (HR 0·87 [0·65-1·17, pinteraction=0·61] for progression-free survival and 1·03 [0·80-1·34, pinteraction=0·01] for overall survival). The association of BMI with overall survival for patients treated with targeted and immune therapies differed by sex, with inverse associations in men (HR 0·53 [0·40-0·70]), but no associations observed in women (HR 0·85 [0·61-1·18, pinteraction=0·03]). INTERPRETATION Our results suggest that in patients with metastatic melanoma, obesity is associated with improved progression-free survival and overall survival compared with those outcomes in patients with normal BMI, and that this association is mainly seen in male patients treated with targeted or immune therapy. These results have implications for the design of future clinical trials for patients with metastatic melanoma and the magnitude of the benefit found supports further investigation of the underlying mechanism of these associations. FUNDING ASCO/CCF Young Investigator Award, ASCO/CCF Career Development Award, MD Anderson Cancer Center (MDACC) Melanoma Moonshot Program, MDACC Melanoma SPORE, and the Dr Miriam and Sheldon G Adelson Medical Research Foundation.

HSP105 recruits protein phosphatase 2A to dephosphorylate β-catenin.

ABSTRACT The Wnt/β-catenin pathway causes accumulation of β-catenin in the cytoplasm and its subsequent translocation into the nucleus to initiate the transcription of the target genes. Without Wnt stimulation, β-catenin forms a complex with axin (axis inhibitor), adenomatous polyposis coli (APC), casein kinase 1α (CK1α), and glycogen synthase kinase 3β (GSK3β) and undergoes phosphorylation-dependent ubiquitination. Phosphatases, such as protein phosphatase 2A (PP2A), interestingly, also are components of this degradation complex; therefore, a balance must be reached between phosphorylation and dephosphorylation. How this balance is regulated is largely unknown. Here we show that a heat shock protein, HSP105, is a previously unidentified component of the β-catenin degradation complex. HSP105 is required for Wnt signaling, since depletion of HSP105 compromises β-catenin accumulation and target gene transcription upon Wnt stimulation. Mechanistically, HSP105 depletion disrupts the integration of PP2A into the β-catenin degradation complex, favoring the hyperphosphorylation and degradation of β-catenin. HSP105 is overexpressed in many types of tumors, correlating with increased nuclear β-catenin protein levels and Wnt target gene upregulation. Furthermore, overexpression of HSP105 is a prognostic biomarker that correlates with poor overall survival in breast cancer patients as well as melanoma patients participating in the BRIM2 clinical study.

Biomarker analysis of on-treatment and at progression biopsies from BRIM7 - a phase 1B trial of combined vemurafenib and cobimetinib treatment in BRAF V600 mutated melanoma

Materials and methods Tumor tissues were collected at baseline prior to treatment, on-treatment at cycle 1 day 14 (C1D14) and at disease progression (PD). Modulation of the MAPK and PI3K pathways, cell proliferation, and CD8 T-cells in tumor biopsies were assessed by immunohistochemistry. Changes in transcription profiles upon treatment were measured by qRT-PCR using the Fluidigm/Nanostring platforms.

Repression of Stress-Induced LINE-1 Expression Protects Cancer Cell Subpopulations from Lethal Drug Exposure

Maintenance of phenotypic heterogeneity within cell populations is an evolutionarily conserved mechanism that underlies population survival upon stressful exposures. We show that the genomes of a cancer cell subpopulation that survives treatment with otherwise lethal drugs, the drug-tolerant persisters (DTPs), exhibit a repressed chromatin state characterized by increased methylation of histone H3 lysines 9 and 27 (H3K9 and H3K27). We also show that survival of DTPs is, in part, maintained by regulators of H3K9me3-mediated heterochromatin formation and that the observed increase in H3K9me3 in DTPs is most prominent over long interspersed repeat element 1 (LINE-1). Disruption of the repressive chromatin over LINE-1 elements in DTPs results in DTP ablation, which is partially rescued by reducing LINE-1 expression or function.

Gene expression profiling in BRAF-mutated melanoma reveals patient subgroups with poor outcomes to vemurafenib that may be overcome by cobimetinib plus vemurafenib

Purpose: The association of tumor gene expression profiles with progression-free survival (PFS) outcomes in patients with BRAFV600-mutated melanoma treated with vemurafenib or cobimetinib combined with vemurafenib was evaluated. Experimental Design: Gene expression of archival tumor samples from patients in four trials (BRIM-2, BRIM-3, BRIM-7, and coBRIM) was evaluated. Genes significantly associated with PFS (P < 0.05) were identified by univariate Cox proportional hazards modeling, then subjected to unsupervised hierarchical clustering, principal component analysis, and recursive partitioning to develop optimized gene signatures. Results: Forty-six genes were identified as significantly associated with PFS in both BRIM-2 (n = 63) and the vemurafenib arm of BRIM-3 (n = 160). Two distinct signatures were identified: cell cycle and immune. Among vemurafenib-treated patients, the cell-cycle signature was associated with shortened PFS compared with the immune signature in the BRIM-2/BRIM-3 training set [hazard ratio (HR) 1.8; 95% confidence interval (CI), 1.3–2.6, P = 0.0001] and in the coBRIM validation set (n = 101; HR, 1.6; 95% CI, 1.0–2.5; P = 0.08). The adverse impact of the cell-cycle signature on PFS was not observed in patients treated with cobimetinib combined with vemurafenib (n = 99; HR, 1.1; 95% CI, 0.7–1.8; P = 0.66). Conclusions: In vemurafenib-treated patients, the cell-cycle gene signature was associated with shorter PFS. However, in cobimetinib combined with vemurafenib-treated patients, both cell cycle and immune signature subgroups had comparable PFS. Cobimetinib combined with vemurafenib may abrogate the adverse impact of the cell-cycle signature. Clin Cancer Res; 23(17); 5238–45. ©2017 AACR.

1093PDVEMURAFENIB AND COBIMETINIB POTENTLY INHIBIT PS6 SIGNALING IN BRAFV600 MUTATION–POSITIVE LOCALLY ADVANCED OR METASTATIC MELANOMA FROM BRIM7 STUDY

ABSTRACT Aim: Combined BRAF and MEK inhibition, compared with BRAF inhibitor alone, may delay the onset of resistance. Vemurafenib + cobimetinib (vem + cobi) was evaluated in patients naive to or previously treated with BRAF inhibitor (BRAFi) in a phase Ib trial: BRIM7 (NCT01271803). Modulation of signaling pathways and transcriptional profiles were assessed in tumor samples. Methods: Tumor tissues were collected at baseline, on-treatment at cycle 1 day 14 (C1D14), and at disease progression (PD). Modulation of cell-signaling pathways was assessed in tumor biopsy specimens by immunohistochemistry (IHC) or reverse-phase protein array (RPPA). Tumor transcriptional profiles were measured on a NanoString platform. Results: pERK levels were inhibited an average of 86 ± 14% with vem + cobi in paired biopsy specimens (n = 7) at C1D14 compared with baseline, which coincided with enhanced down-regulation of ERK transcriptional targets, compared with vem alone (n = 20). Cytoplasmic pERK was inhibited by 92 ± 3% in BRAFi-naive patients and by 95 ± 3% in patients with PR/CR responses. The inhibition of S6 ribosomal protein phosphorylation (pS6) showed significant differences based on treatment response and prior treatment status. By IHC, pS6 levels were clearly reduced in BRAFi-naive patients (82 ± 8%) compared with patients whose disease progressed with BRAFi treatment (31 ± 22%) and similarly in PR/CR patients (88 ± 11%) vs PD/SD patients (33 ± 19%). These observations were verified in independent samples by RPPA: levels of pS6 (S235/236 and S240/244) and a pS6 downstream effector, p4EBP1 (T37/46), were significantly inhibited in the same patients. At PD, tumor pERK, pS6, and Ki67 inhibition were attenuated to different degrees in each patient, whereas transcriptional programs largely reverted to baseline profiles. Conclusions: Vem + cobi treatment resulted in robust modulation of tumor cell signaling and transcriptional programs. In concordance with reports for single-agent BRAF or MEK inhibitor treatment, potent inhibition of pS6 was observed in BRAFi-naive patients and patients with PR/CR, which may contribute to the enhanced response to the vem + cobi combination. Disclosure: Y. Yan: Employee of Genentech, Inc.; G. McArthur: Consultant: Roche-Genentech, Novartis, GSK, BMS, Millenium, Amgen Research: Pfizer, Millenium, Novartis; T. Gajewski: Consultant: Bayer, B-I, Abbvie, Roche/Genentech, Jounce, Dendreon, Amgen Investigator: BMS, Merck, Roche/Genentech, Incyte, Ono; I. Puzanov: Consultant: Roche (honoraria) Investigator: Roche/Genentech (funds to university); O. Hamid: Research/advisory board/consultant/speaker: Genentech; R. Gonzalez: Research/consultant/honoraria: GSK, Roche/Genentech, BMS; Y. Wang: Employee: Genentech; S. Lu: Employee: Genentech; M. Wongchenko: Employee: Genentech; N.W. Choong: Employee: Roche/Genentech Stockholder: Roche; A. Ribas: Consultant: Amgen, GSK, Genentech, Merck Stockholder: Kite Pharma.