Jose Perez-Garcia

Targeting FGFR with Dovitinib (TKI258): Preclinical and Clinical Data in Breast Cancer

Purpose: Fibroblast growth factor receptor 1 (FGFR1) and FGFR2 amplifications are observed in approximately 10% of breast cancers and are related to poor outcomes. We evaluated whether dovitinib (TKI258), an inhibitor of FGFR1, FGFR2, and FGFR3, presented antitumor activity in FGFR-amplified breast cancers. Experimental Design: Preclinical activity of dovitinib was evaluated in both breast cancer cell lines and an FGFR1-amplified xenograft model (HBCx2). Dovitinib was then evaluated in a phase II trial that included 4 groups of patients with human EGF receptor 2–negative metastatic breast cancer on the basis of FGFR1 amplification and hormone receptor (HR) status. FGFR1 amplification was assessed by silver in situ hybridization. Preplanned retrospective analyses assessed predictive value of FGFR1, FGFR2, and FGF3 amplifications by quantitative PCR (qPCR). Results: Dovitinib monotherapy inhibits proliferation in FGFR1- and FGFR2-amplified, but not FGFR-normal, breast cancer cell lines. Dovitinib also inhibits tumor growth in FGFR1-amplified breast cancer xenografts. Eighty-one patients were enrolled in the trial. Unconfirmed response or stable disease for more than 6 months was observed in 5 (25%) and 1 (3%) patient(s) with FGFR1-amplified/HR-positive and FGFR1-nonamplified/HR-positive breast cancer. When qPCR-identified amplifications in FGFR1, FGFR2, or FGF3 were grouped to define an FGF pathway–amplified breast cancer in HR-positive patients, the mean reduction in target lesions was 21.1% compared with a 12.0% increase in patients who did not present with FGF pathway–amplified breast cancer. Conclusion: Dovitinib showed antitumor activity in FGFR-amplified breast cancer cell lines and may have activity in breast cancers with FGF pathway amplification. Clin Cancer Res; 19(13); 3693–702. ©2013 AACR.

Genomic aberrations in the FGFR pathway: opportunities for targeted therapies in solid tumors

The fibroblast growth factor receptor (FGFR) cascade plays crucial roles in tumor cell proliferation, angiogenesis, migration and survival. Accumulating evidence suggests that in some tumor types, FGFRs are bona fide oncogenes to which cancer cells are addicted. Because FGFR inhibition can reduce proliferation and induce cell death in a variety of in vitro and in vivo tumor models harboring FGFR aberrations, a growing number of research groups have selected FGFRs as targets for anticancer drug development. Multikinase FGFR/vascular endothelial growth factor receptor (VEGFR) inhibitors have shown promising activity in breast cancer patients with FGFR1 and/or FGF3 amplification. Early clinical trials with selective FGFR inhibitors, which may overcome the toxicity constraints raised by multitarget kinase inhibition, are recruiting patients with known FGFR(1-4) status based on genomic screens. Preliminary signs of antitumor activity have been demonstrated in some tumor types, including squamous cell lung carcinomas. Rational combination of targeted therapies is expected to further increase the efficacy of selective FGFR inhibitors. Herein, we discuss unsolved questions in the clinical development of these agents and suggest guidelines for management of hyperphosphatemia, a class-specific mechanism-based toxicity. In addition, we propose standardized definitions for FGFR1 and FGFR2 gene amplification based on in situ hybridization methods. Extended access to next-generation sequencing platforms will facilitate the identification of diseases in which somatic FGFR(1-4) mutations, amplifications and fusions are potentially driving cancer cell viability, further strengthening the role of FGFR signaling in cancer biology and providing more possibilities for the therapeutic application of FGFR inhibitors.The fibroblast growth factor receptor (FGFR) cascade plays crucial roles in tumor cell proliferation, angiogenesis, migration and survival. Accumulating evidence suggests that in some tumor types, FGFRs are bona fide oncogenes to which cancer cells are addicted. Because FGFR inhibition can reduce proliferation and induce cell death in a variety of in vitro and in vivo tumor models harboring FGFR aberrations, a growing number of research groups have selected FGFRs as targets for anticancer drug development. Multikinase FGFR/vascular endothelial growth factor receptor (VEGFR) inhibitors have shown promising activity in breast cancer patients with FGFR1 and/or FGF3 amplification. Early clinical trials with selective FGFR inhibitors, which may overcome the toxicity constraints raised by multitarget kinase inhibition, are recruiting patients with known FGFR(1-4) status based on genomic screens. Preliminary signs of antitumor activity have been demonstrated in some tumor types, including squamous cell lung carcinomas. Rational combination of targeted therapies is expected to further increase the efficacy of selective FGFR inhibitors. Herein, we discuss unsolved questions in the clinical development of these agents and suggest guidelines for management of hyperphosphatemia, a class-specific mechanism-based toxicity. In addition, we propose standardized definitions for FGFR1 and FGFR2 gene amplification based on in situ hybridization methods. Extended access to next-generation sequencing platforms will facilitate the identification of diseases in which somatic FGFR(1-4) mutations, amplifications and fusions are potentially driving cancer cell viability, further strengthening the role of FGFR signaling in cancer biology and providing more possibilities for the therapeutic application of FGFR inhibitors.

PI3K inhibition results in enhanced estrogen receptor function and dependence in hormone receptor–positive breast cancer

Inhibition of the PI3K/AKT pathway results in induction of ER-dependent transcriptional activity and susceptibility to anti-estrogen therapy in ER-positive breast cancer. PIKing the correct therapeutic combination Mutations in a gene called PIK3CA are very common in estrogen receptor–positive breast cancers, and drugs that inhibit PI3K, the protein product of this gene, are already in clinical development. Unfortunately, these drugs are not always effective, and this study by Bosch et al. demonstrates a reason for this problem and a practical way to overcome it. By studying both mouse models and human patients’ tumors, the authors discovered that inhibition of PI3K often stimulates the activity of the estrogen receptor, which then drives tumor growth. By combining PI3K inhibitors with clinically available drugs that inhibit the estrogen receptor, the authors were able to overcome treatment resistance and effectively induce tumor regression in mouse models. Activating mutations of PIK3CA are the most frequent genomic alterations in estrogen receptor (ER)–positive breast tumors, and selective phosphatidylinositol 3-kinase α (PI3Kα) inhibitors are in clinical development. The activity of these agents, however, is not homogeneous, and only a fraction of patients bearing PIK3CA-mutant ER-positive tumors benefit from single-agent administration. Searching for mechanisms of resistance, we observed that suppression of PI3K signaling results in induction of ER-dependent transcriptional activity, as demonstrated by changes in expression of genes containing ER-binding sites and increased occupancy by the ER of promoter regions of up-regulated genes. Furthermore, expression of ESR1 mRNA and ER protein were also increased upon PI3K inhibition. These changes in gene expression were confirmed in vivo in xenografts and patient-derived models and in tumors from patients undergoing treatment with the PI3Kα inhibitor BYL719. The observed effects on transcription were enhanced by the addition of estradiol and suppressed by the anti-ER therapies fulvestrant and tamoxifen. Fulvestrant markedly sensitized ER-positive tumors to PI3Kα inhibition, resulting in major tumor regressions in vivo. We propose that increased ER transcriptional activity may be a reactive mechanism that limits the activity of PI3K inhibitors and that combined PI3K and ER inhibition is a rational approach to target these tumors.

Chemotherapy and role of the proliferation marker Ki-67 in digestive neuroendocrine tumors

Neuroendocrine tumors (NETs) of the digestive tract are a heterogeneous group of rare malignancies. Three major subgroups can be defined: pancreatic endocrine tumors, carcinoid tumors, and poorly differentiated gastroenteropancreatic NETs. Classically, digestive NETS have been considered to have an indolent course characterized for prolonged stabilizations or slow progressions, but there are clear differences in terms of aggressiveness, clinical course, and response to treatment among them. Retrospective studies have identified several clinicopathological and immunohistochemical factors as angioinvasion and proliferative index assessed by Ki-67 expression, which predict biological behavior and correlate with survival. Chemotherapy regimens based on the combination of several active drugs such as streptozocin, doxorubicin, 5-fluorouracil, dacarbazine, and temozolomide show low response rates, which sets the need to improve the results of the medical treatment of these malignancies. This review will analyze the role of Ki-67 in digestive NETs under a clinical perspective and will suggest future fields for development of this approach that enable a better patient selection for chemotherapy. Also a comprehensive review of the literature about chemotherapy in NETs is presented.

Pushing the Envelope in the mTOR Pathway: The Second Generation of Inhibitors

The phosphatidylinositol-3-kinase (PI3K)/mTOR pathway has been a major focus of attention for cancer researchers in the past decade. A preliminary and incomplete understanding of the molecular biology of this complex network has importantly conditioned not only the development of the first generation of mTOR inhibitors, but also the biomarker studies designed to identify the best responders to these agents. Most recently, research in this pathway has focused on the dual nature of mTOR that is integrated by the mTOR complex 1 and complex 2. These two complexes are formed and regulated by different proteins and are also driven by multiple different compensatory feedback loops. This deeper understanding has allowed the development of a promising second generation of inhibitors, which are able to block simultaneously both complexes due to their catalytic activity over mTOR. Moreover, some of them also exert an inhibitory effect over PI3K that is a key player in the feedback loops. This article reviews the newest insights in the signaling of the mTOR pathway and then focuses on the development of the new wave of mTOR inhibitors. Mol Cancer Ther; 10(3); 395–403. ©2011 AACR.

A Phase Ib Dose-Escalation Study of the Oral Pan-PI3K Inhibitor Buparlisib (BKM120) in Combination with the Oral MEK1/2 Inhibitor Trametinib (GSK1120212) in Patients with Selected Advanced Solid Tumors

Purpose: MAPK and PI3K/AKT/mTOR pathways play important roles in many tumors. In this study, safety, antitumor activity, and pharmacokinetics of buparlisib (pan class PI3K inhibitor) and trametinib (MEK inhibitor) were evaluated. Experimental Design: This open-label, dose-finding, phase Ib study comprised dose escalation, followed by expansion part in patients with RAS- or BRAF-mutant non–small cell lung, ovarian, or pancreatic cancer. Results: Of note, 113 patients were enrolled, 66 and 47 in dose-escalation and -expansion parts, respectively. MTD was established as buparlisib 70 mg + trametinib 1.5 mg daily [5/15, 33% patients with dose-limiting toxicities (DLT)] and recommended phase II dose (RP2D) buparlisib 60 mg + trametinib 1.5 mg daily (1/10, 10% patients with DLTs). DLTs included stomatitis (8/103, 8%), diarrhea, dysphagia, and creatine kinase (CK) increase (2/103, 2% each). Treatment-related grade 3/4 adverse events (AEs) occurred in 73 patients (65%); mainly CK increase, stomatitis, AST/ALT (aspartate aminotransferase/alanine aminotransferase) increase, and rash. For all (21) patients with ovarian cancer, overall response rate was 29% [1 complete response, 5 partial responses (PR)], disease control rate 76%, and median progression-free survival was 7 months. Minimal activity was observed in patients with non–small cell lung cancer (1/17 PR) and pancreatic cancer (best overall response was SD). Relative to historical data, buparlisib exposure increased and trametinib exposure slightly increased with the combination. Conclusions: At RP2D, buparlisib 60 mg + trametinib 1.5 mg daily shows promising antitumor activity for patients with KRAS-mutant ovarian cancer. Long-term tolerability of the combination at RP2D is challenging, due to frequent dose interruptions and reductions for toxicity. Clin Cancer Res; 21(4); 730–8. ©2014 AACR.

Molecular Profiling of Patients with Colorectal Cancer and Matched Targeted Therapy in Phase I Clinical Trials

Clinical experience increasingly suggests that molecular prescreening and biomarker enrichment strategies in phase I trials with targeted therapies will improve the outcomes of patients with cancer. In keeping with the exigencies of a personalized oncology program, tumors from patients with advanced chemorefractory colorectal cancer were analyzed for specific aberrations (KRAS/BRAF/PIK3CA mutations, PTEN and pMET expression). Patients were subsequently offered phase I trials with matched targeted agents (MTA) directed at the identified anomalies. During 2010 and 2011, tumor molecular analysis was conducted in 254 patients: KRAS mutations (80 of 254, 31.5%), BRAF mutations (24 of 196, 12.2%), PIK3CA mutations (15 of 114, 13.2%), KRAS and PIK3CA mutations (9 of 114, 7.9%), low PTEN expression (97 of 183, 53.0%), and high pMET expression (38 of 64, 59.4%). In total, 68 patients received 82 different MTAs: phosphoinositide 3-kinase (PI3K) pathway inhibitor (if PIK3CA mutation, n = 10; or low PTEN, n = 32), PI3K pathway inhibitor plus MEK inhibitor (if KRAS mutation, n = 10; or BRAF mutation, n = 1), second-generation anti-EGF receptor monoclonal antibodies (if wild-type KRAS, n = 11), anti-hepatocyte growth factor monoclonal antibody (if high pMET, n = 10), mTOR inhibitor plus anti-insulin-like growth factor-1 receptor monoclonal antibody (if low PTEN, n = 5), and BRAF inhibitor (if BRAF mutation, n = 3). Median time-to-treatment failure on MTA was 7.9 versus 16.3 weeks for their prior systemic antitumor therapy (P < 0.001). Partial response was seen in 1 patient [1.2%, PI3K inhibitor with PIK3CA mutation] and stable disease >16 weeks in 10 cases (12.2%). These results suggest that matching chemorefractory patients with colorectal cancer with targeted agents in phase I trials based on the current molecular profile does not confer a significant clinical benefit. Mol Cancer Ther; 11(9); 2062–71. ©2012 AACR.

RSK3/4 mediate resistance to PI3K pathway inhibitors in breast cancer

The PI3K signaling pathway regulates diverse cellular processes, including proliferation, survival, and metabolism, and is aberrantly activated in human cancer. As such, numerous compounds targeting the PI3K pathway are currently being clinically evaluated for the treatment of cancer, and several have shown some early indications of efficacy in breast cancer. However, resistance against these agents, both de novo and acquired, may ultimately limit the efficacy of these compounds. Here, we have taken a systematic functional approach to uncovering potential mechanisms of resistance to PI3K inhibitors and have identified several genes whose expression promotes survival under conditions of PI3K/mammalian target of rapamycin (PI3K/mTOR) blockade, including the ribosomal S6 kinases RPS6KA2 (RSK3) and RPS6KA6 (RSK4). We demonstrate that overexpression of RSK3 or RSK4 supports proliferation upon PI3K inhibition both in vitro and in vivo, in part through the attenuation of the apoptotic response and upregulation of protein translation. Notably, the addition of MEK- or RSK-specific inhibitors can overcome these resistance phenotypes, both in breast cancer cell lines and patient-derived xenograft models with elevated levels of RSK activity. These observations provide a strong rationale for the combined use of RSK and PI3K pathway inhibitors to elicit favorable responses in breast cancer patients with activated RSK.

MicroRNA-21 links epithelial-to-mesenchymal transition and inflammatory signals to confer resistance to neoadjuvant trastuzumab and chemotherapy in HER2-positive breast cancer patients

Patients with primary HER2-positive breast cancer benefit from HER2-targeted therapies. Nevertheless, a significant proportion of these patients die of disease progression due to mechanisms of drug resistance. MicroRNAs (miRNAs) are emerging as critical core regulators of drug resistance that act by modulating the epithelial-to-mesenchymal transition (EMT) and cancer-related immune responses. In this study, we investigated the association between the expression of a specific subset of 14 miRNAs involved in EMT processes and immune functions and the response to neoadjuvant trastuzumab and chemotherapy in 52 patients with HER2-overexpressing breast tumors. The expression of only a single miRNA, miR-21, was significantly associated with residual disease (p = 0.030) and increased after trastuzumab-chemotherapy (p = 0.012). A target prediction analysis coupled with in vitro and in vivo validations revealed that miR-21 levels inversely correlated with the expression of PTEN (rs = -0.502; p = 0.005) and PDCD4 (rs = -0.426; p = 0.019), which differentially influenced the drug sensitivity of HER2-positive breast cancer cells. However, PTEN expression was only marginally associated with residual disease. We further demonstrated that miR-21 was able to affect the response to both trastuzumab and chemotherapy, triggering an IL-6/STAT3/NF-κB-mediated signaling loop and activating the PI3K pathway. Our findings support the ability of miR-21 signaling to sustain EMT and shape the tumor immune microenvironment in HER2-positive breast cancer. Collectively, these data provide a rationale for using miR-21 expression as a biomarker to select trastuzumab-chemotherapy-resistant HER2-positive breast cancer patients who may benefit from treatments containing PI3K inhibitors or immunomodulatory drugs.

The next era of treatment for hormone receptor-positive, HER2-negative advanced breast cancer: Triplet combination-based endocrine therapies.

Until recently, the standard of care for hormone receptor-positive (HR+) breast cancer was single-agent endocrine therapy, which aims to prevent estrogen receptor signaling. This therapeutic strategy has extended survival without the toxicity associated with chemotherapy, but primary endocrine therapy resistance is common, and secondary resistance develops over time. Adjunct downstream inhibition of the cyclin-dependent kinase (CDK)4/6 pathway, intended to delay and prevent endocrine therapy resistance, has further extended progression-free survival in patients receiving endocrine therapy; however, resistance still eventually develops in these patients. Addition of phosphatidylinositol-3 kinase (PI3K) or mammalian target of rapamycin (mTOR) inhibitors to combined CDK4/6 and endocrine inhibitor regimens may help prolong CDK4/6 inhibitor sensitivity. Early trials combining CDK4/6 inhibitors, PI3K or mTOR inhibitors, and endocrine therapy have shown encouraging signs of clinical activity. However, further research is needed to help understand the extent of treatment benefit from triplet therapy and where this strategy will fit in the treatment sequence for patients with HR+ breast cancer.