Ramucirumab in metastatic colorectal cancer: evidence to date and place in therapy

Abstract

Colorectal cancer is the third most frequent cancer worldwide. Overall survival rates have improved greatly over the last few years due, at least in part, to the addition of targeted therapies to standard of care chemotherapy. Angiogenesis plays an important role in colorectal cancer, and therapies directed against the vascular endothelial growth factor (VEGF) axis have contributed significantly to improving the outcome of patients with metastatic colorectal cancer. Over the past few years, several new targeted antiangiogenic agents have been approved for this patient population, confirming the value of inhibiting tumour angiogenesis. The most recent among them is ramucirumab, a fully humanized monoclonal antibody that targets the extracellular domain of VEGF receptor 2. It has proven valuable in multiple tumour types including colorectal cancer. Several phase I and II clinical trials showed a favourable toxicity profile and promising clinical antitumour efficacy in colorectal cancer patients. In the phase III RAISE clinical trial, the addition of ramucirumab to FOLFIRI-based chemotherapy resulted in an improvement of overall survival in patients with metastatic colorectal cancer who had been previously treated with bevacizumab, oxaliplatin and a fluoropyrimidine. On the basis of these results, ramucirumab was approved by the US Food and Drug Administration for this setting. We present an overview of the key preclinical and clinical studies in the development of ramucirumab in the context of metastatic colorectal cancer.

Introduction

Colorectal cancer is the third most frequent cancer worldwide and was responsible for nearly 700,000 deaths worldwide in 2012 [Ferlay et al. 2012]. Approximately 25% of patients are diagnosed with metastatic disease and 50% will develop metastasis [Van Cutsem et al. 2014]. Patients with metastatic disease have a poor prognosis with a 5-year survival rate of only 13.1% [National Cancer Institute, 2015].

Systemic chemotherapy has been the main treatment modality for patients with metastatic colorectal cancer. Current cytotoxic agents are fluoropyrimidine-based regimens in combination with oxaliplatin or irinotecan [Tournigand et al. 2004]. Recently, significant progress has been made in the management of metastatic colorectal cancer. These improvements are due in large part to the availability of new therapeutic agents targeting two major axes, epidermal growth factor receptor (EGFR) signalling and angiogenesis. The anti-EGFR agents cetuximab and panitumumab have demonstrated benefit in RAS (NRAS and KRAS) wild-type patients in first- and second-line treatment in combination with chemotherapy, as well as in chemorefractory patients [Douillard et al. 2010; Ciardiello et al. 2014]. Similarly, clinical benefit derived from agents binding to circulating vascular endothelial growth factor (VEGF), a key determinant in the process of angiogenesis, has been demonstrated and the use of antiangiogenic treatments in conjunction with chemotherapy has also become an accepted standard of care for metastatic colorectal cancer.

Ramucirumab is a monoclonal antibody against the extracellular domain of vascular endothelial growth-factor receptor-2 (VEGFR-2), which was recently approved, by the US Food and Drug Administration (FDA) for its use in metastatic colorectal cancer in the second-line setting in combination with 5-fluorouracil, leucovorin and irinotecan (FOLFIRI).

This review offers an overview of angiogenesis in colorectal cancer and summarizes key data from preclinical and clinical studies in the development of ramucirumab.

Angiogenesis and colorectal cancer

Angiogenesis is a complex process that is precisely regulated at the molecular and genetic levels. While it is an integral part of numerous physiological processes including embryogenesis, wound healing and menstruation, it is also a key component of tumour growth and metastasis, and dysregulation of any aspect of angiogenesis contributes to both of these events. The ‘switch’ to an angiogenic phenotype is considered a hallmark of the malignant process by which pro-angiogenic mechanisms overwhelm negative regulators of angiogenesis [Hanahan and Weinberg, 2000].

Tumours require a vascular supply to grow that is achieved via the expression of pro-angiogenic growth factors, including members of the VEGF family of ligands [Folkman, 2003]. Tumour progression and poor prognosis in numerous tumour types, including colorectal carcinoma, has been associated with the overexpression of VEGF [Lee et al. 2000]. The VEGF-related gene family of angiogenic and lymphangiogenic growth factors comprises six secreted glycoproteins, VEGF-A, VEGF-B, VEGF-C, VEGF-D, VEGF-E, and placenta growth factors (PIGF)-1 and -2 [Ferrara et al. 2003]. VEGF ligands mediate their angiogenic effects via several different receptors (Figure 1). Two receptors were originally identified on endothelial cells and characterized as the specific tyrosine kinase receptors VEGFR-1 [Shibuya et al. 1990] and VEGFR-2 [Matthews et al. 1991]. An additional tyrosine kinase receptor, VEGFR-3, was identified subsequently, and has been found to be primarily associated with lymphangiogenesis [Paavonen et al. 2000]. VEGFR-2 is the main mediator of several physiological and pathological effects of VEGF-A on endothelial cells, including proliferation, migration, survival, and permeability. In adults, VEGFR-2 is expressed mainly on vascular endothelial cells, megakaryocytes, and haematopoietic stem cells [Hicklin and Ellis, 2005; Kerbel, 2008]. The VEGF pathway is initiated when VEGF binds to the ectodomain of its receptor in the endothelial cells. This binding activates the intrinsic tyrosine kinase activity, initiating intracellular signalling [Ferrara, 2004]. Preclinical studies have demonstrated that blockade of the VEGF-A/VEGFR-2 interaction inhibits tumour angiogenesis and growth, rendering it a promising approach in anticancer treatments [Zhu et al. 2002].

Figure 1.

Binding specificity of vascular endothelial growth factor family members and their receptors.

VEGF, vascular endothelial growth factor; VEGFR, vascular endothelial growth factor receptor; PIGF, placenta growth factor; Flt, human receptor-type tyrosine kinase gene; NRP, neuropilin; KDR, Kinase Insert Domain Receptor.

Antiangiogenic agents in colorectal cancer

In the context of colorectal cancer, VEGF expression is associated with the induction and maintenance of the neovasculature, and correlates with microvessel count. It plays a key role in tumour growth and metastasis in these patients [Takahashi et al. 1995; Ellis et al. 1996]. Significant research has been invested into developing antiangiogenic agents, and over the last decade, four have been approved by the FDA for metastatic colorectal cancer. Pivotal studies leading to this approval are summarized in Table 1.

Table 1.

Studies targeting angiogenesis in metastatic colorectal cancer.

Reference	Study	Study design	Treatment arms	Primary efficacy end point	Other efficacy end points
Hurwitz et al. [2004]	AVF2017	Randomized phase III trial in patients with previously untreated mCRC	IFL versus IFL + bevacizumab	OS: 20.3 months (IFL + bevacizumab) versus 15.6 months (IFL) (HR, 0.66;p = 0.001)	PFS: 10.6 months (IFL + bevacizumab) versus 6.2 months (IFL) (HR, 0.54; p = 0.001)
Giantonio et al. [2007]	ECOG 3200	Second-line randomized phase III trial in patients failing under fluoropyrimidine and irinotecan therapy	FOLFOX4 versus FOLFOX4 + bevacizumab versus bevacizumab	OS: 12.9 months (FOLFOX4 + bevacizumab) versus 10.8 months (FOLFOX4) (HR, 0.75; p = 0.001)	PFS: 7.3 months (FOLFOX4 + bevacizumab) versus 4.7 months (FOLFOX4) (HR, 0.61; p = 0.001)
Bennouna et al. [2013]	ML 18147	Second-line randomized phase III trial in patients who progressed on one line of fluoropyrimidine-based combination chemotherapy + bevacizumab	Alternate combination chemotherapy versus alternate combination chemotherapy + bevacizumab	OS: 11.2 months (chemotherapy + bevacizumab) versus 9.8 months (chemotherapy) (HR, 0.81;p = 0.0062)	PFS: 5.7 months (chemotherapy + bevacizumab) versus 4.1 months (chemotherapy) (HR, 0.68; p = 0.001)
Van Cutsemet al. [2012]	VELOUR	Second-line randomized phase III trial in patients who progressed following one line of oxaliplatin and fluoropyrimidine	FOLFIRI versus FOLFIRI + aflibercept	OS: 13.5 months (FOLFIRI + aflibercept) versus 12.06 months (FOLFIRI) (HR, 0.817; p = 0.0032)	PFS: 6.9 months (FOLFIRI + aflibercept) versus 4.7 months (FOLFIRI) (HR, 0.758; p = 0.001)
Grothey et al. [2013]	CORRECT	Randomized phase III trial in refractory mCRC	BSC versus regorafenib	OS: 6.4 months (regorafenib) versus 5.0 months (BSC) (HR, 0.77;p = 0.0052)	PFS: 1.9 months (regorafenib) versus 1.7 months (BSC) (HR, 0.49; p = 0.001)
Tabernero et al. [2015]	RAISE	Randomized phase III trial in patients who progressed following first line of oxaliplatin, bevacizumab, and a fluoropyrimidine for mCRC	FOLFIRI versus FOLFIRI + ramucirumab	OS: 13.3 months (FOLFIRI + ramucirumab) versus 11.7 months (FOLFIRI) (HR 0.844; p = 0.0219)	PFS: 5.7 months (FOLFIRI + ramucirumab) versus 4.5 months (FOLFIRI) (HR, 0.793; p = 0.0005)

BSC, best supportive care; FOLFIRI, fluorouracil, leucovorin, and irinotecan; FOLFOX4, infusional fluorouracil, leucovorin, and oxaliplatin; HR, hazard ratio; IFL, irinotecan, fluorouracil, and leucovorin; mCRC, metastatic colorectal cancer; OS, overall survival; PFS, progression-free survival.

Bevacizumab is a humanized immunoglobulin monoclonal antibody directed against VEGF-A. It binds all isoforms of VEGF-A, blocking it from binding to its cognate receptors [Ferrara et al. 2005]. Bevacizumab is the only antiangiogenic agent approved by the FDA for first-line treatment of metastatic colorectal cancer. This approval was based on a phase III clinical trial that compared IFL (irinotecan, fluorouracil, and leucovorin) with IFL plus bevacizumab showing superior overall survival, progression-free survival and response rate [Hurwitz et al. 2004]. In the second-line setting, the E3200 study compared the addition of bevacizumab with infusional fluorouracil, leucovorin, and oxaliplatin (FOLFOX) versus FOLFOX alone in bevacizumab-naïve patients with metastatic colorectal cancer after first-line progression under fluorouracil and irinotecan [Giantonio et al. 2007], demonstrating an overall survival, progression-free survival and response-rate advantage for the combination. The TML trial evaluated the utility of continuing bevacizumab beyond first progression in the second-line setting after first-line treatment with chemotherapy plus bevacizumab [Bennouna et al. 2013]. This study showed an improvement of overall survival favouring continuation of bevacizumab.

Aflibercept is a recombinant fusion protein acting as a soluble receptor that binds to VEGF-A, VEGF-B and PIGF [Holash et al. 2002]. The VELOUR study compared aflibercept in combination with FOLFIRI versus placebo plus FOFLIRI in patients with metastatic colorectal cancer who had progressed on first-line oxaliplatin fluoropyrimidine therapy [Van Cutsem et al. 2012]. The combination of chemotherapy with aflibercept significantly improved overall survival, progression-free survival and response rate compared with FOLFIRI/placebo.

Regorafenib is a multikinase inhibitor targeting BRAF, VEGFR-1/2/3, KIT, TIE-2, PDGFR-β, fibroblast growth factor receptor 1 (FGFR-1), RET, RAF-1, and p38 MAP kinase [Strumberg and Schultheis, 2012]. Recent studies have shown that RAF may be the critical target of regorafenib in HCT116 colon cancer cells [Chen et al. 2014]. It was evaluated in a phase III clinical trial in chemotherapy refractory settings against placebo, showing significant improvement of overall and progression-free survival, although the differences were small [Grothey et al. 2013].

The most recent agent to be approved, ramucirumab (IMC-1121B; ImClone Systems, New York, NY), is a fully humanized immunoglobulin G1 (IgG-1) monoclonal antibody that binds with high affinity to the extracellular VEGF-binding domain of VEGFR-2. The RAISE trial evaluated the addition of ramucirumab to FOLFIRI after progression under first-line oxaliplatin/fluoropyrimidine-based chemotherapy combined with bevacizumab, showing a significant improvement for overall survival as well as for progression-free survival [Tabernero et al. 2015].

Mechanism of action and preclinical background of ramucirumab

Ramucirumab is a fully human IgG-1 monoclonal antibody that binds with high affinity (K_D 50 pmol/l) to the VEGFR-2 extracellular domain, inhibiting VEGFR-2 activation and signalling. In contrast to other agents directed against the VEGF pathway, ramucirumab binds a specific epitope on the extracellular domain of VEGFR-2, blocking all VEGF ligands from binding to this therapeutically validated target. Consequently, it blocks the binding of VEGF-C and VEGF-D to the VEGFR-2 [Jimenez et al. 2005]. As such, ramucirumab has the potential capacity to inhibit multiple activities initiated by VEGF activation of VEGFR-2.

Given that ramucirumab does not cross-react with the murine homolog of human VEGFR-2, in vivo evaluations were conducted using a surrogate of ramucirumab, DC101, a rat antimouse VEGFR-2 specific monoclonal antibody [Witte et al. 1998]. DC101 binds with high affinity to the extracellular domain of mouse VEGFR-2 and inhibits VEGF-mediated signalling via VEGFR-2. DC101 exhibited antitumour activity in several mouse xenograft models [Prewett et al. 1999]. In vivo experiments were conducted with DC101 in a murine model of colon carcinoma liver metastases, to investigate the hypothesis that blockade of the VEGF function may lead to both inhibition of angiogenesis and decreased endothelial cell survival. Human colon carcinoma cells were injected into the spleen of nude mice to produce liver metastases. After 7 days of tumour growth, mice received either DC101 or vehicle. Blocking VEGFR-2 activation with the DC101 antibody led to decreased vessel counts in liver metastases from human colon carcinoma cells. An increase in tumour cell death in DC101-treated mice was also seen. Furthermore, those studies demonstrated that blockade of VEGFR-2 led to endothelial cell apoptosis [Bruns et al. 2000].

When combined with various other agents in mouse models, DC101 exhibited an enhanced reduction in tumour growth rate [Bruns et al. 2002; Klement et al. 2002; Sweeney et al. 2002]. In one study, DC101 combined with IFL inhibited growth of the colorectal carcinoma cell line HT-29. This cell line is resistant to oxaliplatin and S12, a murine antibody that blocks circulating VEGF in a similar way to bevacizumab. By contrast, inhibition of tumour growth was not seen in animals treated with IFL plus S12, oxaliplatin plus S12, or control. These results suggest that inhibition of VEGFR-2 could inhibit growth in colorectal tumours resistant to other antiangiogenic agents [Bruns et al. 2000; Tonra et al. 2006].

Clinical development of ramucirumab in colorectal cancer

Early clinical trials

A phase I clinical trial was conducted to evaluate the safety, maximum-tolerated dose, pharmacokinetics, pharmacodynamics and preliminary anticancer activity of ramucirumab using a classic 3-plus-3 design [Spratlin et al. 2010]. Patients with advanced solid malignancies were treated once weekly with escalating doses of intravenous ramucirumab. The initial ramucirumab dose level (2 mg/kg) was selected based on pharmacokinetic and toxicology studies. The dose was increased sequentially by 100% (4 mg/kg), 50% (6 mg/kg), and 33% (8 mg/kg); thereafter, the dose escalation increment was fixed at 25%.

Thirty-seven patients received a total of 888 ramucirumab infusions over seven dose levels ranging from 2 to 16 mg/kg. Dose-limiting toxicities (DLTs) in cycle 1 were reported at 10 and 16 mg/kg, with patients developing grade 3 hypertension and deep vein thrombosis. The maximum tolerated dose of ramucirumab was determined to be 13 mg/kg with a weekly schedule.

Twenty-two patients (60%) experienced grade 3 or worse adverse events. The most frequently reported included hypertension (13.5%) and abdominal pain (10.8%). Hypertension was related to dose and cumulative therapy at higher doses. It generally resolved after administration of common oral antihypertensive treatment. Other grade 3–5 adverse events included anorexia, vomiting, increased blood alkaline phosphatase, headache, proteinuria, dyspnoea and deep vein thrombosis. The most frequently reported adverse events were fatigue (51%), headache (51%), peripheral oedema (35%), diarrhoea (35%), nausea (32%), respiratory infections (32%), abdominal pain (30%), arthralgia (27%), cough (27%) and dyspnoea (27%).

Pharmacokinetics characterization showed that the clearance rate of ramucirumab decreased disproportionately as the dose increased from 2 to 16 mg/kg, suggesting receptor-mediated clearance mechanisms. At doses higher than 8 mg/kg, clearance was saturated, presumably reflecting the fact that all VEGFR-2 sites were blocked. Maximum concentration and area under the concentration-time curve and half-life values also increased disproportionately as the dose increased from 2 to 16 mg/kg, showing a nonlinear exposure. Ramucirumab half-life at steady state ranged from 200 to 300 hours at doses of 8 to 16 mg/kg. Target C_min value was at least 20 μg/ml (based on efficacy data in human tumour xenografts) which was achieved at all doses, except after their first infusion for some patients treated at 2–4 mg/kg (Table 2).

Table 2.

Noncompartmental ramucirumab pharmacokinetics parameters [Spratlin et al. 2010].

Dose level and cycle 1 infusion	Number of patients	Half-life (hours)		PK Parameters in Cycle 1
		Mean	SD	Trough Cmin (μg/ml)		Cmax (μg/ml)		AUC0-∞ (h·μg/ml)		Cl (ml/h/kg)
				Mean	SD	Mean	SD	Mean	SD	Mean	SD
2 mg/kg
First infusion	6	68.4	10.7	6.83	1.60	43.7	6.71	3914	534	0.519	0.075
Last infusion	3	104	22.0	104	21.8	21.3	7.37	78	27	0.222	0.076
4 mg/kg
First infusion	6	92.5	34.5	18.8	10.7	80.3	11.7	9143	4192	0.508	0.220
Last infusion	4	200	51.1	55.5	24.6	155	77.7	25,839	9174	0.179	0.092
6 mg/kg
First infusion	4	86.8	22.4	41.7	1.53	183	25.3	19,099	2331	0.318	0.0.041
Last infusion	4	136	89.6	118	26.3	364	124	45,850	15,040	0.140	0.045
8 mg/kg
First infusion	5	123	34.9	93.4	21.08	325	62.28	43,824	10,341	0.190	0.038
Last infusion	5	318	140	176	57.9	497	168	132,789	47,746	0.067	0.025
10 mg/kg
First infusion	7	110	30.4	166	138	406	152	40,333	9134	0.264	0.085
Last infusion	7	205	61.3	313	157	616	100	156,840	49,016	0.069	0.022
13 mg/kg
First infusion	5	90.1	25.2	103	44.0	429	134	45,710	25,058	0.399	0.275
Last infusion	5	300	136	328	73.8	883	225	236,290	89,906	0.061	0.019
16 mg/kg
First infusion	6	120	34.7	177	42.1	558	132	67,871	13,361	0.245	0.059
Last infusion	5	283	87.0	280	98.1	934	508	190,592	68,357	0.096	0.046

PK, pharmacokinetic; Cmin, minimum concentration; Cmax, maximum concentration; AUC_0-∞, area under the concentration-time curve from zero extrapolated to infinity; Cl, clearance; SD, standard deviation.

First infusion: all PK parameters were calculated over 168 hours after the first infusion in cycle 1.

Final infusion: all PK parameters were calculated over 336 hours after the final infusion in cycle 1 except Cmin, which was calculated 168 hours after the final infusion of cycle 1.

Serum VEGF-A concentrations increased almost immediately after treatment, remaining elevated through to the next treatment. This was considered to be due to the displacement of the native VEGF-A, given that the affinity of ramucirumab for VEGFR-2 is higher than that of the natural ligands. VEGF-A levels remained elevated as long as ramucirumab was present. Soluble VEGFR-1 and VEGFR-2 concentrations generally decreased immediately after ramucirumab treatment. The changes in VEGF-A and soluble VEGFR-1 and -2 were not related to dose. Changes in tumour perfusion and vascularity were evaluated by dynamic contrast-enhanced magnetic resonance imaging in 13 patients, demonstrating decreased tumour perfusion and vascularity in nine patients (69%). A disease control rate of 73% was obtained in the 27 patients with measurable disease, including four with partial response and 23 patients with stable disease as the best response.

Two more phase I clinical trials were recently reported. One evaluated the safety and pharmacokinetics of ramucirumab given every 2 or 3 weeks [Chiorean et al. 2015]. A total of 25 patients were enrolled, 13 of whom were treated with 6, 8 or 10 mg/kg of ramucirumab every 2 weeks and the other 12 were treated with 15 or 20 mg/kg every 3 weeks. No DLTs were observed. The toxicity and the pharmacokinetic profiles were comparable with those reported previously [Spratlin et al. 2010]. Based on the results of these two studies, the recommended phase II doses were established to be 8 mg/kg every 2 weeks and 10 mg/kg every 3 weeks.

In a phase Ib clinical trial, the safety and pharmacokinetics of second-line ramucirumab plus FOLFIRI was evaluated in Japanese patients with metastatic colorectal carcinoma to confirm the recommended dose of ramucirumab in combination with FOLFIRI [Yoshino et al. 2015]. Six patients were enrolled to receive ramucirumab 8 mg/kg every 2 weeks plus FOLFIRI (180 mg irinotecan infusion, 200 mg/m² leucovorin infusion, 5-fluorouracil as a bolus of 400 mg/m² followed by a continuous infusion of 2400 mg/m²). One patient met the DLT criteria with grade 2 proteinuria and grade 4 neutropenia. The addition of ramucirumab to FOLFIRI did not alter the pharmacokinetics of irinotecan or SN-38. Pharmacokinetic and safety profiles were consistent with those previously reported. Regarding efficacy, one patient had a partial response, four had stable disease and one had progressive disease. The median progression-free survival was 7.3 months.

Phase II single arm study of ramucirumab combined with modified FOLFOX-6 in colorectal cancer patients

An open-label phase II study evaluating the safety and efficacy of ramucirumab combined with modified FOLFOX-6 (mFOLFOX-6) as first-line therapy for metastatic colorectal cancer was performed. Eligible patients received intravenous ramucirumab 8 mg/kg and the mFOLFOX-6 regimen every 2 weeks [Garcia-Carbonero et al. 2014]. Endpoints included progression-free survival, objective response rate, overall survival and safety.

A total of 48 patients were treated. Median progression-free survival was 11.5 months (95% CI, 8.6–13.1 months) (Figure 2). The objective response rate was 58.3% (95% CI, 43.21–72.39), and the disease control rate was an impressive 93.8% with most patients experiencing tumour burden reduction. Median overall survival was 20.4 months (95% CI, 18.5–25.1).

Figure 2.

Kaplan–Meier estimate of progression-free survival for patients treated with ramucirumab + modified FOLFOX6 in a Phase II study [Garcia-Carbonero et al. 2014].

CI, confidence interval; mFOLFOX-6, modified FOLFOX-6 regimen; PFS, progression-free survival.

The most frequent grade 3 or 4 adverse events were neutropenia (33.3% grade 3, 8.3% grade 4), hypertension (16.7% grade 3) and neuropathy (12.5% grade 3). Grade 2 proteinuria was observed in 12.5% of the patients and one patient developed grade 4 nephrotic syndrome. Two patients died due to myocardial infarction and cardiopulmonary arrest potentially related to arterial thromboembolic events. Three patients had grade 3 and 4 venous thromboembolic events.

Pharmacokinetic and pharmacodynamic analyses were conducted in nine patients. Mean trough levels after repeated dosing of 8 mg/kg ramucirumab every 2 weeks exceeded concentrations associated with antitumour activity in preclinical models. Higher baseline levels of soluble VEGFR-1 and VEGF-A and lower baseline levels of VEGF-D appeared to be associated with longer progression-free and overall survival.

Phase III study of ramucirumab versus placebo in combination with FOLFIRI as second-line therapy in colorectal carcinoma patients (RAISE)

Between December 2010 and August 2013, 1072 patients were enrolled into the randomized double-blind phase III RAISE trial. Eligible patients had metastatic pathologically confirmed colorectal carcinoma regardless of KRAS (Kirsten rat sarcoma viral oncogene homolog) exon 2 status and disease progression during or within 6 months of the last dose of first-line therapy with bevacizumab, oxaliplatin, and a fluoropyrimidine for metastatic disease [Tabernero et al. 2015].

Patients were randomized (1:1) to receive 8 mg/kg intravenous ramucirumab plus FOLFIRI regimen (180 mg/m² irinotecan followed by or concurrent with 400 mg/m² leucovorin, followed by 400 mg/m² fluorouracil given as an intravenous bolus then 2400 mg/m² given as a continuous infusion over 48 hours) or placebo plus FOLFIRI, every 2 weeks. Randomization was stratified by geographical location, KRAS mutation status, and time to disease progression after starting first-line treatment. The primary endpoint was overall survival in the intention-to-treat population. Secondary endpoints were progression-free survival, the proportion of patients achieving an objective response, disease control, adverse events and patient-reported outcomes.

Of the 1361 patients screened, 1072 were randomly assigned, 536 to each group. The study population was balanced at baseline (Table 3). A single metastatic site was reported in 32% of patients, 38% had two and 29% had three or more metastatic sites. Fifty percent of the patients had wild-type KRAS exon 2. The median duration of therapy was similar in the ramucirumab and placebo groups.

Table 3.

Patient characteristics for the RAISE phase III study [Tabernero et al. 2015].

	Ramucirumab/FOLFIRI (n = 536)	Placebo/FOLFIRI (n = 536)
Age (years)
Mean (SD)	62 (21–83)	62 (33–87)
<65	324 (60%)	321 (60%)
⩾65	212 (40%)	215 (40%)
Sex
Male	289 (54%)	326 (61%)
Female	247 (46%)	210 (39%)
ECOG performance status
0	263 (49%)	259 (48%)
1	268 (50%)	273 (51%)
2 or 3	1 (<1%)	2 (<1%)
Missing	4 (1%)	2 (<1%)
Time to progression after start of first-line treatment
<6 months	125 (23%)	129 (24%)
⩾6 months	411 (77%)	407 (76%)
KRAS exon 2 status
Mutant	269 (50%)	261 (49%)
Wild type	267 (50%)	275 (51%)
Carcinoembryonic antigen (μg/l)
<200	389 (73%)	393 (73%)
⩾200	108 (20%)	107 (20%)
Missing	39 (7%)	36 (7%)
Primary tumour
Colon	358 (67%)	358 (67%)
Rectum	174 (33%)	171 (32%)
Colorectal	4 (1%)	7 (1%)

SD, standard deviation; ECOG, Eastern Cooperative Oncology Group; KRAS, Kirsten rat sarcoma viral oncogene homolog.

After a median follow up of 21.7 months, median overall survival was 13.3 months (95% CI, 12.4–14.5) for patients in the ramucirumab group versus 11.7 months (95% CI, 10.8–12.7) for the placebo group (hazard ratio (HR) 0.844; 95% CI, 0.730–0.976; log-rank p = 0.0219) (Figure 3A). All prespecified subgroups had longer survival with ramucirumab than with placebo. Progression-free survival was 5.7 months (95% CI, 5.5–6.2) in the ramucirumab group versus 4.5 months (95% CI, 4.2–5.4) in the placebo group (HR 0.793; 95% CI, 0.697–0.903; log-rank p = 0.0005) (Figure 3B). Objective response rates were equivalent in the two groups (13.4% versus 12.5%; p = 0.63).

Figure 3.

Kaplan–Meier estimates of overall survival (A) and progression-free survival (B) in the intention-to-treat population for ramucirumab versus placebo Tabernero et al. [2015].

FOLFIRI, 180 mg/m² irinotecan followed by or concurrent with 400 mg/m² leucovorin, followed by 400 mg/m² fluorouracil given as an intravenous bolus then 2400 mg/m² given as a continuous infusion over 48 hours.

Significant AEs are summarized in Table 4. Treatment discontinuation due to AEs was reported in 11% of the ramucirumab group and 4% of the placebo group, the most common causative events being neutropenia, thrombocytopenia, diarrhoea and stomatitis. The incidence of dose omissions and dose reductions was similar in the two groups. Significant grade 3 or worse neutropenia was report-ed in 38% of the ramucirumab group versus 24% in the placebo group; however febrile neutropenia incidence was infrequent with minimal difference between arms (3% in the ramucirumab group versus 2% in the placebo group). Minimal differences were seen between arms for grade 3 or worse diarrhoea (11% versus 10%) and fatigue (12% versus 8%) with ramucirumab and placebo, respectively. The frequency of serious AEs was similar in the two treatment groups.

Table 4.

Major grade 3–4 adverse events in the RAISE phase III study, by patient.

	Ramucirumab/ FOLFIRI		Placebo/ FOLFIRI
	Grade 3	Grade 4	Grade 3	Grade 4
Neutropenia	149 (28%)	54 (10%)	77 (15%)	46 (9%)
Thrombocytopenia	15 (3%)	1 (<1%)	2 (<1%)	2 (<1%)
Anaemia	8 (2%)	0	19 (4%)	0
Leukopenia	13 (3%)	1 (<1%)	13 (3%)	1 (<1%)
Febrile neutropenia	11 (2%)	7 (1%)	11 (2%)	2 (<1%)
Diarrhoea	53 (10%)	4 (1%)	44 (8%)	7 (1%)
Fatigue	61 (12%)	0	41 (8%)	0
Neuropathy	5 (1%)	0	2 (<1%)	0

In terms of known associated severe-related adverse events, grade 3 or worse hypertension was seen in 11% in the ramucirumab group versus 3% in the placebo group (Table 5). Most low-grade haemorrhagic events were due to epistaxis, while the majority of grade 3 or worse were gastrointestinal. Grade 3–4 proteinuria was slightly more frequent in the ramucirumab group (3% versus <1%) whereas the incidence of venous thromboembolic events was similar in both groups.

Table 5.

Adverse events related to antiangiogenic treatment.

Adverse event	Ramucirumab/FOLFIRI			Placebo/FOLFIRI
	Grade 3	Grade 4	Grade 5	Grade 3	Grade 4	Grade 5
Haemorrhage	9 (2%)	1 (<1%)	3 (0·6%)	4 (1%)	4 (1%)	1 (<1%)
Gastrointestinal haemorrhage	6 (1%)	1 (<1%)	3 (0·6%)	3 (1%)	2 (<1%)	1 (<1%)
Hypertension	58 (11%)	1 (<1%)	0	15 (3%)	0	0
Proteinuria	15 (3%)	1 (<1%)	0	1 (<1%)	0	0
Venous thromboembolic event	18 (3%)	4 (1%)	0	11 (2%)	0	0
Gastrointestinal perforation	2 (<1%)	3 (1%)	4 (1%)	2 (<1%)	1 (<1%)	0
Arterial thromboembolic event	2 (<1%)	1 (<1%)	1 (<1%)	0	1 (<1%)	5 (1%)

Quality of life was assessed; patients completed the EORTC QLQ-30 (quality of life questionnaire) at baseline, prior to every cycle for the first 6 months, then every fourth cycle, at treatment discontin-uation, and at the 30-day follow up [Garcia-Carbonero, 2015]. A transient worsening of quality of life was reported with ramucirumab relative to placebo (global quality of life, physical functioning, role functioning, cognitive functioning, pain, fatigue, dyspnoea and appetite loss). Nevertheless, when assessing for sustained deterioration, there were no statistical differences, leading the investigators to conclude that the addition of ramucirumab to FOLFIRI extends overall and progression-free survival without sustained impaired quality of life.

Conclusion

Colorectal cancer is one of the most frequent tumours worldwide and is difficult to manage in the metastatic setting. The armament of successful agents used to treat this disease has expanded considerably in the last decade with a consequent improvement in survival outlook for many patients in this population. The RAISE trial demonstrates the value of the addition of ramucirumab to FOLFIRI as second-line treatment with a significant improvement in overall survival over placebo plus FOLFIRI, adding a new strategic option for improving outcome in these patients. Toxic effects of ramucirumab combined with FOLFIRI are manageable and do not differ from the known toxicity profile of antiangiogenic agents. Based on the results of the RAISE clinical trial, on April 2015 the FDA approved ramucirumab for use in combination with FOLFIRI in the treatment of patients with metastatic colorectal cancer whose disease has progressed on a first-line regimen containing bevacizumab, oxaliplatin, and a fluoropyrimidine.

The antiangiogenic treatment landscape has been provided with different antiangiogenic drugs with similar efficacy and toxicity profiles. They differ with respect to their mechanism of action and pharmacokinetic properties. Bevacizumab targets VEGF-A to cause ligand sequestering; aflibercept blocks VEGF-A, VEGF-B, and PlGF using the IgG-1 FC-VEGF receptor construct, and ramucirumab targets VEGFR-2 to prevent receptor activation by VEGF-A.

When comparing the results of the RAISE trial to other randomized clinical trials assessing the combination of chemotherapy with antiangiogenics in second-line treatment, efficacy outcomes are in a similar ballpark although study designs vary. The RAISE study differs from the other studies by virtue of a relatively homogeneous population with all patients having received bevacizumab as first-line therapy with chemotherapy based on oxaliplatin and fluoropyrimidine. In contrast, the TML study included patients who received either FOLFIRI or FOLFOX as first-line therapy [Bennouna et al. 2013] while in the VELOUR trial only 30% of patients received first-line bevacizumab [Van Cutsem et al. 2012]. Regardless of these differences, the results of these three trials support the hypothesis that inhibition of angiogenesis beyond first-line progression is an effective approach for improving survival.

Ramucirumab showed a manageable safety profile, which is along the same lines as other known VEGF inhibitors. Compared with the VELOUR trial, there were more grade 3 or 4 adverse events in patients treated with aflibercept than in the patients treated with ramucirumab in the RAISE trial, and especially for those attributable to anti-VEGF treatment.

Since new antiangiogenic agents are emerging in colorectal cancer, more studies comparing the efficacy of those drugs in the second-line setting are needed in order to help guide physicians in selecting the optimal option for a given patient. Furthermore, the evaluation of ramucirumab in other ‘niche’ clinical settings would be of interest, such as after first-line treatment without bevacizumab or as monotherapy for patients who do not tolerate chemotherapy. The addition of antiangiogenic therapy to anti-EGFR targeted agents is being evaluated in a randomized phase II study of irinotecan and cetuximab with or without ramucirumab in KRAS wild-type colorectal cancer patients who have progressed while on treatment with bevacizumab/chemotherapy [ClinicalTrials.gov identifier: NCT01079780].

Given this scenario, potential predictive biomarkers to select patients who are likely to benefit from those treatments are needed. Efficacy of bevacizumab and aflibercept may be affected by the local concentration of targeted ligands, while ramucirumab may be less influenced due to its binding to the VEGFR-2 extracellular domain. Nevertheless, there is an absence of validated biomarkers to reliably select patients who are likely to benefit from antiangiogenic treatments. Further translational research in this field is critical to improve patient selection, thus avoiding unnecessary exposure to toxicity and allowing prediction of the best responders. Data from the RAISE trial are currently being exploited to explore this avenue.

In summary, ramucirumab added to FOLFIRI improves overall survival in the second-line setting for metastatic colorectal cancer after progression on 5-fluorouracil, oxaliplatin and bevacizumab.