Phase II study of cediranib (AZD 2171), an inhibitor of the vascular endothelial growth factor receptor, for second-line therapy of small cell lung cancer (NCI # 7097)

Abstract

Background

Inhibition of angiogenesis is a novel strategy for the treatment of cancer. We evaluated the safety and efficacy of cediranib, a potent small molecule inhibitor of the vascular endothelial growth factor receptor, in patients with refractory or recurrent small cell lung cancer (SCLC).

Methods

SCLC patients with progression following prior platinum-based chemotherapy only, performance status (PS) of 0-2 and adequate bone marrow, renal and hepatic function were included. The dose of cediranib was 45 mg PO QD for the first 12 patients, and was reduced to 30 mg PO QD for the subsequent patients due to intolerance of the higher dose. Treatment was given on a daily continuous schedule. The primary endpoint was determination of the response rate.

Results

Twenty five patients were enrolled. Patient characteristics: male 13; median age - 61; PS: 0 -12 pts, 1- 12 pts. A median of 2 cycles were administered. Salient grade 3/4 toxicities were fatigue, diarrhea, hypertension, proteinuria and elevated liver enzymes. Tolerability was better with the 30 mg QD dose. Nine patients had stable disease, but none had a confirmed partial response. The median progression-free survival and overall survival were 2 and 6 months respectively. Response criteria to proceed to full accrual were not met. Increase in circulating endothelial cell count was noted at the time of progression in several patients.

Conclusions

Cediranib failed to demonstrate objective responses in recurrent or refractory SCLC at the dose and schedule evaluated. The 45 mg dose was intolerable in a majority of SCLC patients.

Introduction

Small cell lung cancer (SCLC) accounts for approximately 13% of all cases of lung cancer in the United States¹. Platinum-based chemotherapy is the mainstay of treatment for patients with SCLC. Though chemotherapy is associated with a high response rate, the disease recurs in nearly all patients with extensive stage disease ². Topotecan, a topoisomerase 1 inhibitor, is the only Food and Drug Administration (FDA)- approved agent for second line therapy of SCLC ³. Topotecan demonstrated symptom improvement when compared to combination chemotherapy and survival benefit when compared to best supportive care ^{3, 4}. However, its efficacy is restricted to patients with initial sensitivity to platinum-based chemotherapy. Given the poor outcomes associated with SCLC, evaluation of other novel agents for the treatment of SCLC is an urgent priority.

Angiogenesis is critical to the growth and sustenance of cancer ⁵. Vascular endothelial growth factor (VEGF) is an important mediator of angiogenesis in both physiological circumstances and in the milieu of cancer. Studies conducted in patients with SCLC have linked circulating concentrations of VEGF with prognosis ^6–10. Patients with a lower level of circulating VEGF were more likely to respond to chemotherapy compared to those with higher levels of VEGF ⁷. The survival rates were inferior for patients with high VEGF concentrations. Studies have also demonstrated a strong correlation between VEGF expression and tumor microvessel density in SCLC ⁸. In patients with resected SCLC, VEGF overexpression has been shown to correlate with microvessel density, nodal and pathological stage and poor outcome ^{9 10}. The results from these studies suggest that VEGF may be linked to poor outcome in SCLC. Therefore, inhibition of VEGF represents a rational therapeutic strategy for evaluation in SCLC.

Treatment with either an anti-VEGF monoclonal antibody or a VEGFR tyrosine kinase inhibitor results in inhibition of new blood vessel formation, regression of tumor growth and improved survival in preclinical models ¹¹. Cediranib (AZD 2171, Recentin®) is a potent and selective inhibitor of the VEGF receptors 1, 2 and 3 ¹². It has demonstrated anti-cancer activity in a variety of pre-clinical models including lung cancer. It has a high bio-availability with oral administration. The recommended phase II dose of cediranib was 45 mg PO QD as monotherapy when given on a continuous daily schedule ¹³. In phase I studies, cediranib demonstrated anti-cancer activity in a variety of solid organ malignancies ^{13, 14}. Therefore, we conducted a phase II study of cediranib for patients with recurrent and/or refractory SCLC.

Patients and methods

Patient eligibility

Patients with SCLC that progressed with one prior regimen (platinum-based chemotherapy) were eligible, regardless of the type of response to first-line therapy. Other salient eligibility criteria were the presence of measurable disease, Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0-2, age > 18 years, and the ability to take oral medications on a regular basis. Qualifying laboratory criteria were: leukocytes ≥3,000/µL; absolute neutrophil count (ANC) ≥1,500/µL; platelet count ≥100,000/µL; serum total bilirubin ≤ institutional upper limit of normal (ULN); serum transminases ≤ 2.5 X ULN; and serum creatinine < ULN. Exclusion criteria were: Known brain metastasis, mean QTc interval >500 msec (with Bazett’s correction) in screening electrocardiogram, history of familial long QT syndrome, proteinuria > + 1 on two consecutive dipsticks taken no less than 1 week apart, class III or IV heart failure (NYHA) and those requiring concurrent use of drugs with proarrhythmic potential, presence of severe intercurrent illness, pregnancy, lactation, patients taking anti-retroviral therapy for HIV disease, use of any other investigational agent within 30 days prior to registration, and concomitant use of nephrotoxic drugs. Patients who had chemotherapy, radiotherapy, or major surgery within 4 weeks (6 weeks for nitrosoureas or mitomycin C) prior to study entry or those who have not recovered from adverse events from agents administered more than 4 weeks earlier were excluded. The study protocol was approved by the institutional review board of each participating institution. All patients signed an informed consent form.

Treatment plan

Cediranib was administered at the dose of 45 mg PO QD for the first 12 patients enrolled to the study. Since 7 of these patients were unable to complete the first cycle of therapy due to intolerance, the protocol was amended to reduce the dose of cediranib to 30 mg PO QD for subsequent patients. The drug was administered on a daily continuous oral schedule. Patients were instructed to take cediranib either 1 hour before, or 2 hours after a meal. Each treatment cycle consisted of 4 weeks of therapy. Treatment cycles were continued until disease progression, unacceptable toxicity or withdrawal of informed consent. Patients were asked to complete a pill diary to document intake of the medication. Radiographic studies were performed every 2 cycles of therapy to assess response. The RECIST criteria were utilized to classify response. Toxicity was graded by the National Cancer Institute Common Terminology Criteria version 3.0.

Dose modifications for toxicity

Dose modifications were done for toxicity attributable to cediranib. All toxicities were to have improved to grade 1 or less before initiation of each cycle of therapy. In the event of toxicity, the dose of cediranib was reduced by one dose level to either 30 mg QD, 20 mg QD or 10 mg QD, from the initial dose. Expected grade 1 toxicities such as proteinuria, hypertension or hemorrhage were treated with dose reduction by 1 level. For other grade 1 or 2 toxicities, dose reduction by 1 level was done if the symptoms did not improve with appropriate supportive care measures. For grade 3 or higher non-hematological toxicity and grade 4 hematological toxicity related to cediranib, the dose was reduced by 1 dose level if symptoms did not resolve to grade 2 or less within 48 hours of appropriate supportive care measures. A maximum of 2 dose reductions were permitted for each patient. Delay in initiation of therapy of longer than 2 weeks due to toxicity resulted in removal from the study. Cediranib was discontinued permanently if patients developed reversible posterior leucoencephalopathy syndrome or symptomatic heart failure.

Patients were provided with a blood pressure monitor and asked to check their blood pressure twice-daily. If two consecutive measurements were > 140/90, they were instructed to call the physician. Guidelines for management of hypertension with appropriate anti-hypertensive therapy were included in the study protocol. Cediranib was held for grade 3 hypertension and appropriate anti-hypertensive therapy was initiated. Treatment was resumed only after recovery to grade 1 or less.

Patient evaluations

Baseline evaluations were conducted within one week prior to initiation of protocol therapy. A history and physical examination, complete blood count with differential (CBC), serum chemistry, vital signs, serum pregnancy test for women of child bearing potential and assessment of performance status were required at baseline. Radiographic studies including computerized axial tomography (CT) scan were performed within four weeks prior to study entry and every two cycles subsequently. Toxicity was assessed before the initiation of every cycle and on an as needed basis. Bone scans and magnetic resonance imaging (MRI) scans were only required when prompted by appropriate symptoms. Routine imaging of the brain was not necessary in asymptomatic patients. Serum levels of troponin-T and I was measured at baseline and after every 2 cycles of therapy if clinically indicated. Serum thyroid stimulating hormone and T4 levels were measured at baseline and with every 2 cycles of therapy. Urine dipstick test for evaluation for proteinuria was done once a week during study therapy. An echocardiogram or a MUGA scan was done at baseline for patients at risk for impaired cardiac function and every 2 cycles if clinically indicated.

Correlative studies

Magnetic separation of circulating endothelial cells

Peripheral blood was to be collected in 10 mL EDTA tubes at baseline, day 15 and at the week 10 assessment. Participation in this part of the study was optional. Tubes were immediately placed on wet ice and shipped or stored overnight at approximately 4°C. Upon arrival, the exact quantity of blood was recorded, transferred into CPT Vaccutainer tubes and centrifuged to exclude granulocytes. Buffy coats were collected, washed, and fixed in 2% paraformaldehyde (PF). Cells were stored at 4°C and analyzed within two weeks from the date received. Magnetic separation and exclusion of CD45-positive cells was performed to enrich for a non-hematopoietic fraction of WBCs. (CD45-microbeads, Miltenyi Biotec) and passed through a magnetic column of a MACS Separation Unit according to the manufacturer’s protocol (all magnetic separation products from Miltenyi Biotec). Both the negative and positive fractions were collected and counted using Z1 series COULTER COUNTER® Cell and Particle Counter (Beckman Coulter, Inc). Three counts were performed for each fraction. The ratio of CD45-negative cells per total WBCs was established, as well as their concentration per volume of blood. Following magnetic separation, cells were cyto-spun onto positively charged Superfrost Plus microscope slides (Fisher Scientific, Inc.) using a Shandon Cytospin 2 centrifuge (Thermo, Inc.). After washing, slides were incubated with FITC-conjugated anti-CD146-antibody (cat. # MAB16985F, Chemicon International, Inc.), PE-conjugated anti-CD133-antibody (cat. # 130-080-801, Miltenyi Biotec) and counterstained with DAPI (Sigma). Cells were observed on an Olympus BX61 Motorized Research Microscope (Olympus America, Inc.) equipped with a fluorescent filter set and analyzed via SlideBook 4.1 software (Intelligent Imaging Innovations, Inc.). Positive and negative cells were counted manually on each slide. Circulating endothelial cells (CECs) were defined as CD45-, CD146+ and DAPI-bright, with no less than 300 CD45- cells being counted. Circulating endothelial progenitors (CEPs) were defined as CD45-, CD133+, CD146+ and DAPI-bright. Both the absolute number and relative percentage of CECs and CEPs among WBCs was determined. VEGF Plasma levels were determined using ELISA as previously reported ¹⁵.

Statistical methods

The primary endpoint of the study was determination of the objective response rate with cediranib in patients with refractory or recurrent SCLC. Secondary endpoints included the assessment of toxicity, overall survival and progression-free survival. An objective response rate of 20% with cediranib was required for further evaluation of the regimen, whereas a response rate of 5% or less would be considered not worthy of further study at this schedule and dose. The Simon two-stage design was utilized. If at least 1 objective response was seen in the first 12 patients, accrual would continue to a maximum of 37 patients. The type I and II error were 10% each with this sample size. Patients who received at least one dose of the study drug were considered evaluable for both toxicity and response.

Results

A total of 25 patients were enrolled between March 2006 and December 2007. An interim analysis was conducted after the first 12 patients were enrolled. Seven out of 12 patients did not complete even one cycle of therapy, due to treatment intolerance. The dose of 45 mg PO QD was deemed undeliverable for this patient population. However, of the 5 patients who completed two cycles of therapy, disease stabilization was noted in 4. After discussion with the co-investigators and the Cancer Therapy Evaluation Program of the National Cancer Institute, the study was amended to reduce the dose of cediranib to 30 mg QD and re-start the trial. The amended design was to follow the initial design at the new dose of 30 mg, but with the additional provision that the study be stopped if more than 3 of the first 6 patients at 30 mg fail to complete their first course, or if more than 6 of the first 12 patients fail to complete their first course. The results for patients enrolled to both dose levels are reported here.

Patient characteristics

A total of 25 patients with a median age of 61 years were enrolled (Table 1). Thirteen patients were treated at the 30 mg PO QD dose of cediranib. The majority of the patients had an ECOG performance status of 0 or 1. One patient had an ECOG PS of 2. Twenty three patients were of Caucasian ethnicity. All patients had received prior platinum-based chemotherapy. Eleven patients had received prior radiotherapy.

Table 1.

Patient baseline characteristics

	All Patients	45 mg QD	30 mg QD
N	25	12	13
Median age (Years)	61	63	63
Male (N)	13	5	8
ECOG PS 0/1/2 (N)	12/12/1	6/6/0	6/6/1
Prior Radiotherapy (N)	11	4	7

Toxicity

The median number of cycles administered for patient treated at the 45 mg PO QD was less than 1 cycle (range 1–5). The reasons for discontinuation of therapy during cycle 1 were: grade 3 fatigue (n=3), elevated liver enzymes (n=2), grade 3 hypertension (n=1) and death due to progressive disease (n=1). Tolerance of cediranib was better with the 30 mg dose with 8 out of 13 patients completing the first 2 cycles of therapy. The median number of cycles at the lower dose was 2 (range 1–8). Common grade 1 or 2 toxicities were nausea, emesis, fatigue, diarrhea, proteinuria and hypertension (Tables 2 & 3). Hypothyroidism was noted in 2 patients whereas one patient developed hyperthyroidism. Three patients died of progressive disease within 30 days of the last day of study therapy.

Table 2.

Toxicity^*

Toxicity	Grade 1/2/3/4 (N)
Albumin	4/0/0/0
Alkaline Phosphatase	3/1/0/0
Alanine aminotransferase	2/1/2/0
Anorexia	5/7/1/0
Aspartase aminotransferase	3/1/1/0
Constipation	4/1/0/0
Creatinine	2/2/0/0
Dehydration	0/3/0/0
Diarrhea	7/5/2/0
Dry mouth	4/0/0/0
Dyspnea	1/3/1/1
Fatigue	6/4/6/2
Hairloss	2/1/-/-
Hemoglobin	1/1/0/0
Hemorrhage	1/1/0/0
Hypertension	3/7/3/0
Infection with grade 1/2 ANC	1/2/0/0
Leukocytes	1/1/0/0
Lymphopenia	0/0/3/0
Mucositis	2/2/0/0
Muscle weakness	2/5/1/0
Nausea	10/1/0/0
Pain	3/6/1/0
Platelets	2/1/0/0
Proteinuria	5/2/3/0
Rash	3/0/0/0
Rash (Hand-foot syndrome)	2/0/1/0
Sodium (low)	2/0/0/0
Thyroid function (low)	1/1/0/0
Voice changes	6/1/0/0
Vomiting	4/1/0/0
Weight loss	3/2/0/0

^*Events those were possible, probable or definitely related to study therapy in > 1 patient in presented in alphabetic order

Table 3.

Grade 3/4 Toxicity by dose level

Toxicity *	45 mg QD G 3/4 (N=12)	30 mg QD G 3/4 (N=13)
ALT/AST	2/0	1/0
Fatigue	2/2	4/0
Diarrhea	2/0	-
Hypertension	1/0	2/0
Proteinuria	2/0	1/0
Hand-foot syndrome	1/0	-

^*Events those were possible, probable or definitely related to study therapy

Efficacy

No objective responses were noted at either of the dose levels of cediranib. Stable disease was observed in 9 patients with 5 and 4 respectively for the 45 mg and 30 mg dose of cediranib. One patient met criteria for partial response after cycle 2 of therapy, but the scan after cycle 4 demonstrated disease progression (Table 4). The lack of any confirmed objective responses resulted in the closure of the study after stage I of the accrual. The median progression-free survival and the median overall survival were 2 months and 6 months respectively. At the 30 mg dose level, the median PFS and survival were 2 and 4 months respectively.

Table 4.

Efficacy

	All Pts (N)	45 mg QD (N)	30 mg QD (N)
Objective Response	1*	0	1*
Stable disease	9	5	4
Progression	14	6	8
N/A	1	1	0
Median PFS	2 m	2 m	2 m
Median Survival	6 m	6 m	m

^*unconfirmed response

Correlative Studies

Pre- and on-treatment specimens were available in a subset of patients only and the results are considered anecdotal. Due to the limited sample size and lack of clinical activity, no conclusions could be drawn concerning the relationship between numbers of CECs, VEGF plasma levels and treatment efficacy. We had hypothesized that treatment with cediranib would result in a decrease in viable CECs, particularly in responding patients. Five patients had adequate specimens at baseline and at progression. Four of five patients showed an increase in CECs per ml of blood upon progression, with two patients exhibiting sharp increases (>5-fold) after maintaining baseline levels while on treatment (Figure 1). In two patients, only baseline and progression specimens were available; however, CECs in these patients went from low undetectable at baseline to over 120/ml at progression. In seven patients with serial VEGF levels, discernable trends in plasma levels were not detected with therapy, nor were baseline levels informative.

Figure 1.

Numbers of circulating endothelial cells (defined as CD45^NEG, CD146^POS, CD133^NEG and DAPI bright with viable nuclei), with Day 1 draw immediately prior to initiation of first cycle of treatment and the final draw at time of disease progression.

Discussion

Inhibition of angiogenesis has been successful as a treatment strategy in a variety of solid organ malignancies. Cediranib is a highly selective and potent inhibitor of the VEGF receptor. This study was conducted to investigate the utility of inhibiting the VEGF receptor in patients with recurrent or relapsed SCLC for whom the overall prognosis is poor. Though disease stabilization was noted in a few patients, there were no objective responses. One patient had reduction a partial response after 2 cycles, but the tumor progressed quickly thereafter. The study did not meet the efficacy criteria to proceed to full accrual after the interim analysis. Sorafenib, another small molecule VEGF receptor inhibitor, has also demonstrated comparable results as monotherapy in a study by the Southwest Oncology Group (SWOG 0435)¹⁶. Though objective responses were noted in a few patients, the median PFS and overall survival of 2 months and 5–7 months (platinum-refractory and sensitive patients) were similar to the results with cediranib in our study. When evaluated in the maintenance setting after platinum-based therapy ¹⁷, vandetanib, a dual inhibitor of the VEGFR and EGFR tyrosine kinases, failed to improve outcome. Taken together, these results indicate that VEGF tyrosine kinase inhibitors are not suited for monotherapy of SCLC. The Southwest Oncology Group has recently initiated a phase II study with the combination of cisplatin, etoposide and cediranib (20 mg PO QD) for first line therapy of extensive stage SCLC.

Our study also illustrated the difficulty of administering cediranib at the originally recommended dose of 45 mg PO QD, as only 5 of the first 12 patients were able to complete just one month of treatment. When the dose was reduced to 30 mg QD for subsequent patients, the tolerance was better. In a study for patients with NSCLC, cediranib at the 45 mg dose in combination with carboplatin and paclitaxel was not tolerated well, leading to its dose reduction to 30 mg as in our study, and furthermore to a second reduction to 20 mg for further development of this regimen ¹⁸.

Bevacizumab, a monoclonal antibody against VEGF has also been tested in combination with chemotherapy by two single arm phase II studies ^{19, 20}. Though the treatment was tolerated well, the efficacy was modest with a median survival of approximately 11 months. Given the underwhelming efficacy with anti-angiogenic agents in SCLC, it is hoped that the identification of predictive biomarkers might lead to optimal utilization of these agents. The role of CECs in prediction of response to anti-angiogenic agents has become an important area of research. In the current study, a trend towards increase in CECs was noted at the time of progression in 4 out of 5 patients in whom samples were available. Similar findings were noted by Beerepoot and colleagues in a study that demonstrated higher CECs in patients with progressive malignancy compared to those with stable disease or healthy volunteers ²¹. However, Norden-Zfoni and colleagues noted an increase in CECs during therapy with sunitinib among patients who derived clinical benefit ²². The identification of distinct sub-types of CECS including the progenitor cells and mature cells indicates the degree of complexity and the need for additional studies are necessary to ascertain this marker patients receiving anti-angiogenic therapy. Recently, certain genetic polymorphisms in VEGF have been linked with a favorable outcome with bevacizumab ²³. The relevance of this marker to VEGF tyrosine kinase inhibitors is unknown.

In summary, the treatment of SCLC continues to be a major challenge with a clear need to study new targets and approaches.