Sorafenib and irinotecan (NEXIRI) as second- or later-line treatment for patients with metastatic colorectal cancer and KRAS-mutated tumours: a multicentre Phase I|[sol]|II trial

Each year, there are an estimated 1.2 million new cases of colorectal cancer worldwide, with the mortality rate reaching 600 000 (Ferlay et al, 2010). Approximately, half of the patients develop metastases during the course of the disease (Van Cutsem et al, 2010), and for the majority of these patients, treatment is mainly palliative. Over the past 10 years, there has been increasing interest in the combination of chemotherapy (e.g., fluoropyrimidines, irinotecan or oxaliplatin) and targeted therapy (e.g., bevacizumab, cetuximab or panitumumab) in the treatment of metastatic colorectal cancer (mCRC) (Cunningham et al, 2004; Hurwitz et al, 2004; Giantonio et al, 2007; Van Cutsem et al, 2009, 2011; Douillard et al, 2010; Peeters et al, 2010). These combinations have become the standard treatment and resulted in significant improvement in response rate (Cunningham et al, 2004; Hurwitz et al, 2004; Giantonio et al, 2007; Van Cutsem et al, 2009, 2011; Peeters et al, 2010), progression-free survival (PFS) (Cunningham et al, 2004; Hurwitz et al, 2004; Giantonio et al, 2007; Van Cutsem et al, 2009, 2011; Douillard et al, 2010; Peeters et al, 2010) and overall survival (OS) (Hurwitz et al, 2004; Giantonio et al, 2007; Van Cutsem et al, 2009, 2011). In the era of therapeutic personalisation, the identification of molecular biomarkers has a key role in determining both optimal treatment strategies and clinical outcome in patients with mCRC. The presence of the KRAS gene mutation is a well-established predictive factor for lack of response to anti-epidermal growth factor receptor (EGFR) therapies, regardless of the line of treatment (Benvenuti et al, 2007; Di Fiore et al, 2007; Lièvre et al, 2008). At the time of the trial design, there were no effective therapies targeted specifically against KRAS mutant cancers (Tejpar et al, 2012). Indeed, in patients who have disease progression (DP) after irinotecan- or oxaliplatin-based chemotherapies combined with bevacizumab, the addition of cetuximab to irinotecan (Cunningham et al, 2004), or cetuximab or panitumumab as monotherapy are efficacious only in wild-type KRAS tumours (Amado et al, 2008; Karapetis et al, 2008). Sorafenib is an oral inhibitor of tumour cell proliferation and angiogenesis, and the lead compound in a series of Raf signalling pathway inhibitors. It has already proved its efficacy in refractory kidney cancer and unresectable hepatocellular carcinoma (Llovet et al, 2008; Escudier et al, 2009). Even in the presence of KRAS mutation, sorafenib potently inhibits activation of the mitogen-activated-protein kinase pathway and extracellular signal-regulated phosphorylation by inhibiting the serine threonine kinases Raf-1 and B-Raf. In addition, sorafenib inhibits the receptor tyrosine kinase activity of vascular endothelial growth factors (VEGFR 1, 2 and 3) and platelet-derived growth factor receptor beta (Wilhelm et al, 2004). In preclinical models, sorafenib has demonstrated antitumour activity in colorectal cancer cell lines, including those with KRAS-mutated tumours (Wilhelm et al, 2004; Martinelli et al, 2010). In humans, only a Phase I trial showed the feasibility of combining a weekly schedule of irinotecan 125 mg m−2 (D1,8,15,22 D1=D42) and a fixed dose of sorafenib 400 mg twice daily in 34 patients with solid tumours (23 of whom had colorectal cancer) (Mross et al, 2007). However, preclinical promising results had already been gathered on the synergistic effect of this combination particularly in KRAS-mutated tumours (personal communication at the time) and were recently published (Mazard et al, 2013). Novel salvage strategies are needed for improving outcomes in selected KRAS-mutated patients who progress after the failure of all approved standard therapies. In addition, combination schedules need to be evaluated in order to help overcome resistance to chemotherapy. On the basis of the above preclinical and clinical data, we conducted a Phase I/II trial with the aim of assessing the feasibility and efficacy of the combined use of sorafenib and the usual 2-week irinotecan regimen as a second- or later-line treatment of patients with mCRC and KRAS-mutated tumours. In addition, we investigated sorafenib’s pharmacokinetic profile, protein expression on tumour tissues and patient genotypes and their association with efficacy and tolerability. This was an open-label, single-arm, multicentre Phase I/II trial. The protocol was approved by the local ethics committee (Comité de Protection des Personnes Sud Méditerranée IV, Montpellier, France, EudraCT number 2008-004285-53) and the French competent authority (Agence Nationale de Sécurité du Médicament et des produits de santé). The trial was registered at ClinicalTrials.gov (NCT00989469). Adverse events were graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE) version 3.0. Dose-limiting toxicities were defined as any Grade 4 non-haematological toxicity (except for vomiting in the absence of adequate prophylaxis), any toxicity requiring a cycle delay of more than 15 days, any Grade 4 haematological toxicity lasting for more than 7 days, any Grade 3-4 febrile neutropenia, and any concomitant sepsis with Grade 3-4 neutropenia. Expression of EGFR, HER2, PTEN, NF-kB and cyclin D1 was evaluated by immunohistochemistry on 3-μm tissue sections of paraffin-embedded specimens as previously performed in previous studies (Chung et al, 2005; Frattini et al, 2007; Scartozzi et al, 2007; Cascinu et al, 2008; Loupakis et al, 2009). The antibody clones, suppliers, antigen-retrieval procedures, dilutions, staining protocols and cut-point scoring are available on request. We investigated for any association between genotypes or protein expression and response to treatment or toxicity. Associations between response to treatment or toxicity and sorafenib’s pharmacokinetic parameters, patient genotypes or protein expression on tumour tissues were investigated by the χ2 test (or the Fisher test, if applicable). A P-value of 0.05 was considered to indicate statistical significance. All patients received at least two courses of treatment and were therefore evaluable for tolerance. There was no toxicity-related death, and most adverse events were Grade 1 or 2. Grade 3 toxicities included diarrhoea (37%), asthenia (22%), neutropenia (18%) and hand-foot syndrome (13%). The main Grade 4 treatment-related toxicity was neutropenia, observed in 16.7% of patients (Table 3). The irinotecan dose was adjusted in 19 patients (35%), and a treatment delay was required in 38 patients (70%). The results of this Phase I/II trial confirmed the feasibility of combining sorafenib and irinotecan in extensively pretreated patients with mCRC and KRAS mutation. In the Phase I part of the trial, dose escalation of irinotecan was achieved without any DLT, and the recommended Phase II dose was irinotecan 180 mg m−2 once every 2 weeks with fixed-dose sorafenib 400 mg b.d. Principal toxicities included hand-foot syndrome, diarrhoea, asthenia and neutropenia. This treatment combination led to a DCR of 65% (95% CI, 51–77%). Median PFS and OS were 3.7 months and 8.0 months, respectively. When compared with previously published data in the same kind of heavily pretreated mCRC population with KRAS mutation, our results appear promising. Two Phase III trials assessed the use of the anti-EGFR antibodies cetuximab and panitumumab alone in patients who failed on standard chemotherapy. Both of these studies reported median PFS and OS of 1.9 months and ~5 months in KRAS-mutated patients, respectively (Amado et al, 2008; Karapetis et al, 2008). More recently, the multitarget drug regorafenib has been evaluated in a randomized Phase III trial as second- or later-line treatment of mCRC with KRAS-mutated or wild-type tumours (Grothey et al, 2013). A total of 760 patients were to receive best supportive care with either oral regorafenib (160 mg daily) or placebo. In this study, 48% of patients had been pretreated by four or more lines for metastatic disease, all had received bevacizumab and 54% had KRAS mutation. The DCR was 41% vs 15% (P<0.001), median PFS was 1.9 vs 1.7 months (HR=0.49; 95% CI, 0.42–0.58, P<0.001) and median OS was 6.4 vs 5 months (HR=0.77; 95% CI, 0.64–0.94, P=0.0052) in the regorafenib arm as compared with placebo, respectively. Subgroup analyses revealed that, among patients treated by regorafenib, KRAS wild-type patients seem to have longer OS than those with KRAS-mutated tumours (HR=0.65; 95% CI, 0.48–0.90 vs HR=0.87; 95% CI, 0.67–1.12; P=0.0038, respectively). However, subsequent analysis demonstrated that there is no statistically significant interaction between OS and KRAS status (Van Cutsem and Grothey, 2013). Our study is limited by the fact that our Phase I definition of DLT was relatively generous, and that dose reductions in sorafenib had been initially planned for cases of Grade 3 diarrhoea. In a trial such as ours using drug combinations, there is the potential for overlapping toxicities, and some of the toxicities reported in Phase I (such as the Grade 3 diarrhoea) would normally have qualified as DLTs. Possibly due to this limitation, only 17% of Phase II patients received full-dose sorafenib 400 mg b.d. Treatment-related toxicities including Grade 3 diarrhoea (37%) and hand-foot syndrome (13%) and Grade 3-4 neutropenia (35%) were primarily responsible for the high frequency of sorafenib dose reductions to 400 mg. This explains the relative dose intensity of 89% for irinotecan and 61% for sorafenib. For future trials investigating the same drug combination, we therefore recommend that diarrhoea is initially managed by reducing the irinotecan dose, starting at 120 mg m−2 and progressively increasing in case of good tolerance. Compliance to sorafenib 400 mg b.d. could therefore be improved. Although there are currently no specific biomarkers predicting response to sorafenib, our exploratory studies demonstrated a significant association between the common G870A polymorphism of CCND1 and stabilising of the disease under the therapy. In particular, the A/A genotype was associated with better disease control on univariate analyses, suggesting cyclin D1 as a potential biomarker of the combination. Our trial supports preclinical data indicating synergistic antitumour effects of combined sorafenib and irinotecan. Sorafenib appears to retain NF-kappa-B in the cytoplasm, and the drug combination may inhibit NF-kappa-B activation, resulting in an enhanced cytotoxicity of irinotecan (Azad et al, 2013). Other studies have shown that multi-tyrosine kinase inhibitors such as sorafenib may also reverse irinotecan resistance (Mross et al, 2007; Azad et al, 2013). Indeed, sorafenib has been identified both in vitro and in vivo as an inhibitor of the drug-efflux pump ABCG2, favouring irinotecan intracellular accumulation thereby enhancing its toxicity (Mazard et al, 2013). This chemosensitizing property previously described by Wei et al (2012) has also been ascribed to the inhibition of the irinotecan-mediated p38 and ERK activation (Mazard et al, 2013). Possible pharmacokinetic interactions between irinotecan and sorafenib also need to be considered. Our pharmacokinetic investigation was limited to sorafenib, and did not reveal any correlation between treatment-related toxicity and efficacy. However, Mross et al (2007) showed that sorafenib administered at 400 mg b.d. significantly increases irinotecan and SN38 exposure. Another pharmacokinetic study suggested a correlation between sorafenib and exposure to its metabolites with OS and DLTs in 18 patients with CRC, who had been treated with irinotecan at a recommended dose of 100 mg m−2 IV D1, D8 (D1=D42), cetuximab according to the standard weekly schedule, and sorafenib 400 mg b.d. (Azad et al, 2013). Whatever the mechanisms involved, further investigation of this combination appears to be warranted to confirm its efficacy. Pharmacokinetic studies are particularly needed to better characterise any synergy between the two agents. Supported by the preclinical data and this trial’s results, the efficacy of the combination is being further tested in an ongoing multicentre randomized Phase II trial (ClinicalTrials.gov NCT01715441). Marc Ychou has served on the Bayer board, Olivier Bouché has received honoraria from Bayer and served on the Pfizer board, and Pierre Laurent-Puig has served on the Amgen, Pfizer and Merck boards. The remaining authors declare no conflict of interest. We would like to acknowledge the editorial assistance of Vanessa Guillaumon, Catriona Holmes and Julie Courraud. We also thank Patrick Chalbos for his significant work as Clinical Research Associate. This research was supported by a grant from Bayer.