Sorafenib and everolimus in advanced clear cell renal carcinoma: a phase I/II trial of the SCRI Oncology Research Consortium

Clinical results of the EVESOR trial, a multiparameter phase I trial of everolimus and sorafenib combination in solid tumors

PURPOSE

Everolimus (EVE) and sorafenib (SOR) combination was associated with synergistic activity in preclinical models. However, previous clinical studies were hampered by cumulative toxicities when both were given continuously. The academic EVESOR trial (NCT01932177) was designed to assess alternative doses and intermittent dosing schedules of EVE and SOR combination therapy to improve the benefit-risk ratio for patients with solid tumors.

METHODS

EVESOR is a multiparameter dose-escalation phase I trial investigating different doses and dosing schedules, with the final objective of generating data for modeling and simulation. Patients were allocated into continuous (A and B) or intermittent (C and D) schedules to determine the recommended phase II dose (RP2D). The clinical outcomes are presented here.

RESULTS

Forty-three patients were included from 2013 to 2019. Most of them had gynecological (25.6%), cholangiocarcinomas (23.2%), colorectal (14.0%), and breast cancers (11.6%). Dose-escalation up to EVE 10 mg QD and SOR 400 mg BID was possible on intermittent schedules. Five dose-limiting toxicities were observed, and dose reductions were required in 39.5% patients, stabilizing at EVE 5 mg and SOR 200 mg BID for 58.1% of them. The overall response rate was 6.3%, and disease control rate was 75.0%. The median progression-free survival (PFS) was 3.6 months. The longest median PFS were observed in cholangiocarcinomas (9.9 months), and gynecological adenocarcinomas (9.2 months).

CONCLUSION

Intermittent arms were associated with improved efficacy/toxicity profiles; and EVE 5 mg QD and SOR 200 mg BID was defined a clinically feasible dose. Strong signs of efficacy were found in cholangiocarcinomas and gynecologic carcinomas.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01932177.

Sorafenib and everolimus in patients with advanced solid tumors and KRAS-mutated NSCLC: A phase I trial with early pharmacodynamic FDG-PET assessment

BACKGROUND

Treatment of patients with solid tumors and KRAS mutations remains disappointing. One option is the combined inhibition of pathways involved in RAF-MEK-ERK and PI3K-AKT-mTOR.

METHODS

Patients with relapsed solid tumors were treated with escalating doses of everolimus (E) 2.5-10.0 mg/d in a 14-day run-in phase followed by combination therapy with sorafenib (S) 800 mg/d from day 15. KRAS mutational status was assessed retrospectively in the escalation phase. Extension phase included KRAS-mutated non-small-cell lung cancer (NSCLC) only. Pharmacokinetic analyses were accompanied by pharmacodynamics assessment of E by FDG-PET. Efficacy was assessed by CT scans every 6 weeks of combination.

RESULTS

Of 31 evaluable patients, 15 had KRAS mutation, 4 patients were negative for KRAS mutation, and the KRAS status remained unknown in 12 patients. Dose-limiting toxicity (DLT) was not reached. The maximum tolerated dose (MTD) was defined as 7.5 mg/d E + 800 mg/d S due to toxicities at previous dose level (10 mg/d E + 800 mg/d S) including leucopenia/thrombopenia III° and pneumonia III° occurring after the DLT interval. The metabolic response rate in FDG-PET was 17% on day 5 and 20% on day 14. No patient reached partial response in CT scan. Median progression free survival (PFS) and overall survival (OS) were 3.25 and 5.85 months, respectively.

CONCLUSIONS

Treatment of patients with relapsed solid tumors with 7.5 mg/d E and 800 mg/d S is safe and feasible. Early metabolic response in FDG-PET was not confirmed in CT scan several weeks later. The combination of S and E is obviously not sufficient to induce durable responses in patients with KRAS-mutant solid tumors.

Oral stomatitis and mTOR inhibitors: A review of current evidence in 20,915 patients

BACKGROUND

Traditional treatment of malignancies with chemotherapeutic agents is often affected by the damage inflicted on non-cancerous cells. Toxicities of the oral cavity, such as mucositis and stomatitis, are some of the most significant and unavoidable toxicities associated with anti-cancer therapies. For such reason, in the last decades, newer targeted agents have been developed aiming to decrease the rates of side effects on healthy cells. Unfortunately, targeted anti-cancer therapies also showed significant rate of toxicity on healthy tissues. mTOR inhibitors showed some adverse events, such as hyperglycemia, hyperlipidemia, hypophosphatemia, hematologic toxicities, and mucocutaneous eruption, but the most important are still stomatitis and skin rash, often reported as dose-limiting side effects.

PATIENTS AND METHODS

A search of the literature was performed by authors on the PubMed online database using the following key words: "sirolimus" OR "everolimus" OR "temsirolimus" OR "deforolimus" OR "ridaforolimus" combined with the Boolean operator AND with the terms: "stomatitis" OR "mucositis" OR "oral pain." Titles and abstracts of 382 potentially relevant studies were screened; of these, 114 studies were excluded because they did not report the inclusion criteria. In the second round, 268 studies were read full-text, but only 135 reported the inclusion criteria and were included for data extraction. Of the included studies, 95 referred to everolimus use, 16 to ridaforolimus, and 26 to temsirolimus (two studies referred to both everolimus and temsirolimus).

RESULTS

The incidence rate of stomatitis according to the agent used was 25.07% (3,959/15,787) for everolimus, 27.02% (724/2,679) for temsirolimus, and 54.76% (598/1,092) for ridaforolimus. All the three agents analyzed showed high rates of low-grade stomatitis (G1-G2), while the onset of severe stomatitis (G3-G4) was rare.

CONCLUSIONS

Analysis of the reports with patients treated with everolimus, temsirolimus, and ridaforolimus showed a clear prevalence of stomatitis grade 1 or 2. These data differ from that of patients treated with conventional chemotherapy in which mucositis is predominantly of grade 3 or 4.

Role of the NRP-1-mediated VEGFR2-independent pathway on radiation sensitivity of non-small cell lung cancer cells

PURPOSE

To determine if inhibiting neuropilin-1 (NRP-1) affects the radiosensitivity of NSCLC cells through a vascular endothelial growth factor receptor 2 (VEGFR2)-independent pathway, and to assess the underlying mechanisms.

METHODS

The expression of VEGFR2, NRP-1, related signaling molecules, abelson murine leukemia viral oncogene homolog 1 (ABL-1), and RAD51 were determined by RT-PCR and Western blotting, respectively. Radiosensitivity was assessed using the colony-forming assay, and the cell apoptosis were analyzed by flow cytometry.

RESULTS

We selected two cell lines with high expression levels of VEGFR2, including Calu-1 cells that have high NRP-1 expression, and H358 cells that have low NRP-1 expression. Upon inhibition of p-VEGFR2 by apatinib in Calu-1 cells, the expression of NRP-1 protein and other related proteins in the pathway was still high. Upon NRP-1 siRNA treatment, the expression of both NRP-1 and RAD51 decreased (p < 0.01; p < 0.05). Upon ABL-1 siRNA treatment, the expression of NRP-1 was increased and the expression of RAD51 was unchanged. Calu-1 cells treated with NRP-1 siRNA exhibited significantly higher apoptosis and radiation sensitivity in radiation therapy compared to Calu-1 cells treated with apatinib alone (p < 0.01; p < 0.01). The apoptosis and radiation sensitivity in H358 cells with NRP-1 overexpression was similar to the control group regardless of VEGFR2 inhibition.

CONCLUSIONS

We demonstrated that when VEGFR2 was inhibited, NRP-1 appeared to regulate RAD51 expression through the VEGFR2-independent ABL-1 pathway, consequently regulating radiation sensitivity. In addition, the combined inhibition of VEGFR2 and NRP-1 appears to sensitize cancer cells to radiation.

Stomatitis and VEGFR-Tyrosine Kinase Inhibitors (VR-TKIs): A Review of Current Literature in 4369 Patients

Background

Multitargeted tyrosine kinase inhibitors (TKIs) represent a new class of target-specific antineoplastic agents. These agents show some specific adverse events such as fatigue/asthenia, anorexia/loss of appetite, dysgeusia, diarrhea/abdominal pain, hypothyroidism, hypertension, myelosuppression, and stomatitis.

Materials and Methods

A systematic search was performed on PubMed online database using a combination of MESH terms and free text words, “sunitinib” OR “sorafenib” OR “axitinib” OR “cabozantinib” OR “pazopanib” OR “regorafenib” OR “nintedanib” OR “vatalanib” combined through the use of Boolean operator AND with the key words “stomatitis” OR “mucositis,” (i) on human subjects, (ii) written in the English language, and (iii) reporting about the incidence of stomatitis or oral mucositis.

Results

The incidence of stomatitis of any grade was 35.2% for sunitinib, 20.52% for sorafenib, 20.63% for axitinib, and 34.21% for cabozantinib. All the agents showed high rates of low-grade stomatitis (G1-G2), while the onset of severe stomatitis (G3-G4) was very low.

Conclusions

Analysis of the reports with patients treated with sunitinib, sorafenib, axitinib, and cabozantinib showed a clear prevalence of stomatitis grade 1 or grade 2. These data differ from those of patients treated with conventional chemotherapy in which mucositis is predominantly of grade 3 or grade 4.

Lenvatinib in the management of metastatic renal cell carcinoma: a promising combination therapy?

INTRODUCTION

To date, results of combination therapy studies have shown no meaningful clinical benefit over monotherapy and an unacceptably high degree of toxicity in the treatment of metastatic renal cell carcinoma (RCC), with the exception of a combination of immune-checkpoint inhibitors and the association of lenvatinib with everolimus. Lenvatinib is a potent multi-targeted tyrosine kinase inhibitor that targets VEGFR pathways. Everolimus inhibits primarily mTORC1 complex, a downstream effecter of the intracellular PI3K/AKT/mTOR pathway. The association of these two drugs was demonstrated to enhance the inhibitory activity against VEGF and FGF-induced angiogenesis by a vertical inhibition of angiogenic signaling pathways, suggesting a synergistic activity. Areas covered: In this review we summarize the lenvatinib pharmacokinetics, pharmacodynamics, characteristics and the main clinical trial that showed lenvatinib activity in advanced RCC. Expert opinion: Lenvatinib plus everolimus showed promising results in a phase II trial, leading to FDA approval of this combination. Their synergic action on inhibiting the VEGF/VEGFR, FGF (a compensatory mechanism to VEGFR inhibition) and mTOR pathway could be a potential mechanism to overcome treatment resistance. Given that the activity of lenvatinib as an immune-regulator in tumor microenvironment has been demonstrated in cell lines, novel combinations, in particular with immune-checkpoint inhibitors, are under development.

Safety of axitinib and sorafenib monotherapy for patients with renal cell carcinoma: a meta-analysis

We sought to investigate safety of axitinib or sorafenib in renal cell carcinoma (RCC) patients and compare toxicity of these two vascular endothelial growth factor receptor inhibitors. Databases of PubMed and Embase were searched. We included phase II and III prospective trials, as well as retrospective studies, in which patients diagnosed with RCC were treated with axitinib or sorafenib monotherapy at a starting dose of 5 mg and 400 mg twice daily, respectively. The overall incidence of high grade hypertension, fatigue, gastrointestinal toxicity and hand-foot syndrome, along with their 95% confidence intervals (CI), were calculated using fixed- or random- effects model according to heterogeneity test results. A total of 26 trials, including 4790 patients, were included in our meta-analysis. Among them, 6 arms were related to axitinib and 22 were associated with sorafenib. The incidences of hypertension (24.9% vs. 7.9%), fatigue (8.2% vs. 6.6%), and gastrointestinal toxicity (17.6% vs. 11.3%) were higher in patients receiving axitinib versus those receiving sorafenib, while the incidence of hand-foot syndrome was lower in patients receiving axitinib versus those receiving sorafenib (9.5% vs. 13.3%). In conclusion, axitinib showed noticeably higher risks of toxicity versus sorafenib. Close monitoring and effective measures for adverse events are recommended during therapy.

Nephrotoxicity of anticancer treatment

Severe adverse systemic drug events occur commonly as a result of treatment of cancer patients. Nephrotoxicity of chemotherapeutic agents remains a significant complication limiting the efficacy of the treatment. A variety of renal disease and electrolyte disorders can result from the drugs that are used to treat malignant disease. The kidneys are a major elimination pathway for many antineoplastic drugs and their metabolites. Tumour lysis syndrome, an emergency in haematooncology, occurs most often after the initiation of cytotoxic therapy in patients with high-grade lymphomas and acute lymphoblastic leukaemia. Chemotherapeutic agents can affect the glomerulus, tubules, interstitium and renal microvasculature, with clinical manifestations that range from asymptomatic elevation of serum creatinine to acute renal failure requiring dialysis. Some factors such as intravascular volume depletion, as well as concomitant use of other drugs or radiographic ionic contrast media, can potentiate or contribute to the nephrotoxicity. Cytotoxic agents can cause nephrotoxicity by a variety of mechanisms. The most nephrotoxic chemotherapeutic drug is cisplatin, which is often associated with acute kidney injury. Many other drugs such as alkylating agents, antimetabolites, vascular endothelial growth factor pathway inhibitors and epidermal growth factor receptor pathway inhibitors may have toxic effects on the kidneys. The aim of this review is to discuss the issue of nephrotoxicity associated with chemotherapy. In routine clinical practice, monitoring of kidney function is mandatory in order to identify nephrotoxicity early, allowing dosage adjustments or withdrawal of the offending drug.

Lenvatinib for use in combination with everolimus for the treatment of patients with advanced renal cell carcinoma following one prior anti-angiogenic therapy

INTRODUCTION

In patients with mRCC options for second line therapies, following progression on anti-angiogenic agents, that demonstrate a survival advantage in clinical trials have been limited. Recently a number of agents have demonstrated efficacy in this setting. Here in we profile one such therapy, the combination of lenvatinib and everolimus, and discuss the expanded options for therapy available in this setting. Areas covered: In this review, we discuss current algorithms for treatment of mRCC in both the first-line and second-line setting. We discuss the recent addition of cabozantinib and nivolumab, in the second line setting, to the market. Lenvatinib's pharmacology, clinical efficacy and toxicity profile is discussed. A comprehensive literature review was performed using PUBMED. Expert commentary: The current treatment algorithms for mRCC will likely see significant change in the coming years. The addition of immunotherapy to our treatment options in mRCC is of particular importance. Future trials examining the use of immunotherapy, both as monotherapy and in combination with VEGF targeted therapy, will likely be a dominant influence in the therapeutic landscape of mRCC. Progress in terms of the rapid expansion of available active therapies in mRCC needs to be balanced with current deficiencies in terms of predictive biomarkers.

Inefficiencies and Patient Burdens in the Development of the Targeted Cancer Drug Sorafenib: A Systematic Review

Failure in cancer drug development exacts heavy burdens on patients and research systems. To investigate inefficiencies and burdens in targeted drug development in cancer, we conducted a systematic review of all prelicensure trials for the anticancer drug, sorafenib (Bayer/Onyx Pharmaceuticals). We searched Embase and MEDLINE databases on October 14, 2014, for prelicensure clinical trials testing sorafenib against cancers. We measured risk by serious adverse event rates, benefit by objective response rates and survival, and trial success by prespecified primary endpoint attainment with acceptable toxicity. The first two clinically useful applications of sorafenib were discovered in the first 2 efficacy trials, after five drug-related deaths (4.6% of 108 total) and 93 total patient-years of involvement (2.4% of 3,928 total). Thereafter, sorafenib was tested in 26 indications and 67 drug combinations, leading to one additional licensure. Drug developers tested 5 indications in over 5 trials each, comprising 56 drug-related deaths (51.8% of 108 total) and 1,155 patient-years (29.4% of 3,928 total) of burden in unsuccessful attempts to discover utility against these malignancies. Overall, 32 Phase II trials (26% of Phase II activity) were duplicative, lacked appropriate follow-up, or were uninformative because of accrual failure, constituting 1,773 patients (15.6% of 11,355 total) participating in prelicensure sorafenib trials. The clinical utility of sorafenib was established early in development, with low burden on patients and resources. However, these early successes were followed by rapid and exhaustive testing against various malignancies and combination regimens, leading to excess patient burden. Our evaluation of sorafenib development suggests many opportunities for reducing costs and unnecessary patient burden in cancer drug development.

Oncological Impact of M-Tor Inhibitor Immunosuppressive Therapy after Liver Transplantation for Hepatocellular Carcinoma: Review of the Literature

Background: Hepatocellular Carcinoma (HCC) represents the fifth most common malignancy and the third cancer-related cause of death worldwide. Hepatitis B (HBV) and C (HCV) viral infections and alcohol abuse are the principal etiological factors for HCC. Liver transplantation (LT) is oncologically the preferable approach to HCC, as it can remove all the intrahepatic tumor foci, and also the oncogenic cirrhotic liver. The use of mTOR inhibitors (mTORi) for immunosuppression after LT for HCC has been proposed due to rapamycin antitumor activity. We decided to review the literature to clarify the oncological role of mTORi after liver transplantation for HCC, analyzing both present condition and future perspectives. Material and Methods: A systematic literature search was performed using PubMed, EMBASE, Scopus, and the Cochrane Library Central. The search was limited to studies in humans and to those reported in the English language in the period of time between January 2005 and December 2015. Results: The literature search yielded 93 articles; after duplicates were removed, 77 titles and abstracts were reviewed. Most relevant data and papers are herein reported and discussed. Conclusions: So far, the use of mTORi is encouraging in terms of oncological outcomes for patients underwent LT for HCC, both for prevention and treatment of HCC recurrence although definitive data are still awaited.

The Evolution of Nephrectomy and Patient Characteristics in Metastatic Renal Cell Carcinoma Patients Enrolled Into First-Line Tyrosine Kinase Inhibitors Clinical Trials

INTRODUCTION

The objective of this study was to compare rates of nephrectomy (Nx) in, and characteristics of, patients with metastatic renal cell carcinoma (mRCC) enrolled in prospective clinical trials of tyrosine kinase inhibitors (TKIs) that were completed through (Group 1) versus after (Group 2) 2007.

PATIENTS AND METHODS

Searching online databases, we retrospectively identified phase I to III trials with ≥ 15 patients with mRCC treated with first-line TKIs, alone or in combination with other agent(s).

RESULTS

Of 70 trials identified, 42 were included in the analysis (n = 6074 patients). Compared with Group 1, Group 2 patients had significantly less Nx (85.7% vs. 93.7%; P < .001) and prior cytokine therapy (11.1% vs. 46.8%; P < .001). Group 2 also had significantly fewer patients with good prognostic risk (based on Memorial Sloan-Kettering Cancer Center criteria) or performance status (both P < .001). Group 2 patients had a significantly greater objective response rate than Group 1 patients (intent-to-treat analysis: 28.6% vs. 23.1%, respectively; P < .001), whereas Group 1 patients had significantly more stable disease. Clinical benefit was similar in both groups (P = .157), and the means of median progression-free survival were comparable (8.2 and 9.0 months in Groups 1 and 2, respectively; P = .2528).

CONCLUSIONS

Use of Nx in mRCC patients participating in clinical trials has declined in the TKI era. More patients with worse prognostic risk profiles are participating in first-line TKI trials after 2007, but objective response rates are higher. Despite patient characteristics that favor the earlier group, progression-free survival is similar as TKIs have replaced cytokines as first-line therapy.

Antiangiogenesis and vascular disrupting agents in cancer: circumventing resistance and augmenting their therapeutic utility

Angiogenesis is a process essential for tumor growth and metastasis. Inhibition of angiogenesis as an anticancer strategy has shown only moderately improved results and is beset with practical limitations, despite theoretical therapeutic advantages. Inevitably resistance develops, through redundancy of signaling pathways and selection for subclonal populations adapted for hypoxic conditions, with more invasive phenotypes. Antiangiogenic-targeted therapies may find improved efficacy in combination therapies; with others in this class, that directly or indirectly target separate pathways or different components of the same pathway, or with a separate class of tumor vasculature-disrupting agents. This review discusses the challenges and strategies for optimization of combination therapies including metronomic administration of drugs and the need for suitable prognostic and surrogate response biomarkers.

Proposal of "cyclic therapy", a novel treatment strategy with targeted agents for advanced renal cell carcinoma

The number of molecular targeted agents for advanced renal cell carcinoma (RCC) has gradually increased, but evidence on the optimal order of selection for such agents has not yet caught up with this trend. In addition, timing of switching molecular targeted drugs may also become an important issue for controlling the disease as types of these drugs grow in number. Based on the fact that the efficacy of a rechallenge of the drug previously used suggests the recovery of the sensitivity, a cyclic therapy in which drugs are changed before exacerbation to repeatedly administer several drugs in a rotated manner, may also be an effective sequential therapy.

Renal effects of molecular targeted therapies in oncology: a review by the Cancer and the Kidney International Network (C-KIN)

A number of cancer therapy agents are cleared by the kidney and may affect renal function, including cytotoxic chemotherapy agents, molecular targeted therapies, analgesics, antibiotics, radiopharmaceuticals and radiation therapy, and bone-targeted therapies. Many of these agents can be nephrotoxic, including targeted cancer therapies. The incidence, severity, and pattern of renal toxicities may vary according to the respective target of the drug. Here, we review the renal effects associated with a selection of currenty approved targeted cancer therapies, directed to vascular endothelial growth factor or VEGF receptor(s) (VEGF/VEGFR), epidermal growth factor receptor (EGFR), human epidermal growth factor receptor2 (HER2), BRAF, anaplastic lymphoma kinase (ALK), programmed cell death protein-1 or its ligand (PD-1/PDL-1), receptor activator of nuclear factor kappa-B ligand (RANKL), and mammalian target of rapamycin (mTOR). The early diagnosis and prompt treatment of these renal alterations are essential in the daily practice where molecular targeted therapies have a definitive role in the armamentarium used in many cancers.

Future perspectives for mTOR inhibitors in renal cell cancer treatment

ABSTRACT 

Everolimus is a mTOR inhibitor that demonstrates antitumor and antiangiogenic activities. In a randomized Phase III trial, patients with metastatic renal cell carcinoma who progressed on sunitinib/sorafenib were treated with everolimus and showed significant improvement in progression-free survival compared with best supportive care. Novel approaches in treatment are expected to ensure less toxic therapies and increase efficacy of everolimus. To provide a new perspective for mTOR inhibitor research and therapy, we discuss renal cell carcinoma cancer stem cells as a potential target for mTOR inhibitors and present new concepts on emerging antiangiogenic therapies. Finally, we point why systems biology approach with reverse molecular engineering may also contribute to the field of drug discovery in renal cell carcinoma.

RNA-seq reveals aurora kinase-driven mTOR pathway activation in patients with sarcomatoid metastatic renal cell carcinoma

Sarcomatoid metastatic renal cell carcinoma (mRCC) is associated with a poor prognosis, and the biology of the disease has been inadequately characterized. RNA sequencing (RNA-seq) was performed on adjacent benign, clear cell, and sarcomatoid components from clinical specimens with sarcomatoid mRCC. M phase and cell-cycle pathways were enriched in sarcomatoid versus adjacent clear cell components, suggesting greater cell proliferation. The expression of aurora kinase A (AURKA) was increased as part of these pathways, and its increased expression was validated by quantitative PCR (qPCR). Immunohistochemical (IHC) analysis revealed that AURKA levels were increased in sarcomatoid tissue compared with their benign or clear cell parts. The increase in AURKA correlated with increased mTOR pathway activity, as evidenced by increased expression of phosphorylated mTOR (S2448) and ribosomal protein S6K (T389). When AURKA was stably expressed in a RCC cell line (Renca), it resulted in increased expression and activity of mTOR, suggesting that overexpression of AURKA can activate the mTOR pathway. These results warrant the analysis of a larger clinical cohort and suggest that targeting AURKA and/or mTOR in patients with sarcomatoid mRCC should be explored.

IMPLICATIONS

Comparative RNA-seq of adjacent sarcomatoid and clear cell histology of RCC indicates a proliferative phenotype and increased AURKA-dependent activation of mTOR signaling in sarcomatoid RCC, which could be targeted by available agents.

Strategies to overcome resistance to epidermal growth factor receptor monoclonal antibody therapy in metastatic colorectal cancer

Administration of monoclonal antibodies (mAbs) against epidermal growth factor receptor (EGFR) such as cetuximab and panitumumab in combination with conventional chemotherapy substantially prolongs survival of patients with metastatic colorectal cancer (mCRC). However, the efficacy of these mAbs is limited due to genetic variation among patients, in particular K-ras mutations. The discovery of K-ras mutation as a predictor of non-responsiveness to EGFR mAb therapy has caused a major change in the treatment of mCRC. Drugs that inhibit transformation caused by oncogenic alterations of Ras and its downstream components such as BRAF, MEK and AKT seem to be promising cancer therapeutics as single agents or when given with EGFR inhibitors. Although multiple therapeutic strategies to overcome EGFR mAb-resistance are under investigation, our understanding of their mode of action is limited. Rational drug development based on stringent preclinical data, biomarker validation, and proper selection of patients is of paramount importance in the treatment of mCRC. In this review, we will discuss diverse approaches to overcome the problem of resistance to existing anti-EGFR therapies and potential future directions for cancer therapies related to the mutational status of genes associated with EGFR-Ras-ERK and PI3K signalings.

Transglutaminase 2 inhibitor abrogates renal cell carcinoma in xenograft models

PURPOSE

To test whether transglutaminase 2 (TGase 2) inhibitor GK921 alone reverses renal cell carcinoma (RCC) tumor growth. RCC is resistant to both radiation and chemotherapy, and the prognosis remains poor. Despite the recent therapeutic success of vascular endothelial growth factor inhibition in RCC, approximately one-third of RCC patients develop metastatic disease. The expression of TGase 2 is markedly increased in most RCC cell lines, as well as in clinical samples.

METHODS

Previously, we introduced the quinoxaline derivative GK13 as a lead compound for TGase 2 inhibitor. The inhibitory effect of GK13 on TGase 2 was improved in GK921 (3-(phenylethynyl)-2-(2-(pyridin-2-yl)ethoxy)pyrido[3,2-b]pyrazine). GK921 efficacy was tested using sulforhodamine in vitro as well as a xenograft tumor models using ACHN and CAKI-1 RCC cells.

RESULTS

GK921 showed cytotoxicity to RCC (average GI50 in eight RCC cell lines: 0.905 μM). A single treatment with GK921 almost completely reduced tumor growth by stabilizing p53 in the ACHN and CAKI-1 preclinical xenograft tumor models.

CONCLUSION

TGase 2 inhibitor GK921 abrogates RCC growth in xenograft tumor models, suggesting the possibility of a new therapeutic approach to RCC.