KRAS status (wild-type vs mutant) correlates with efficacy to first-line cetuximab in a study of cetuximab single agent followed by cetuximab + FOLFIRI in patients with metastatic colorectal cancer A Cervantes*, T Macurulla, E Martinelli, E Vega-Villegas, E Rodriguez-Braun, F Ciardiello, C Story, J NIppgen, J Baselga, J Tabernero *Hospital Clinico Universitario, Valencia, Spain (Presenting author)

Background (1) Cetuximab is an IgG1 monoclonal antibody vs epidermal growth factor receptor (EGFR) 1 –Targets the extracellular domain –Competitively inhibits ligand binding to disrupt EGFR signalling Cetuximab is active in metastatic colorectal cancer (mCRC) –First-line as monotherapy or with chemotherapy 2–5 –In other lines following cytotoxic chemotherapy 1,6,7 1 Cunningham D, et al. N Engl J Med 2004;351:337–345; 2 Folprecht G, et al. Ann Oncol 2006;17:450–456; 3 Tabernero J, et al. J Clin Oncol 2007;25:5225–5232; 4 Peeters M, et al. Eur J Cancer Suppl. 2005;3 (Abstract 664); 5 Scheithauer W, et al. Eur J Cancer Suppl. 2007;5(S4) (Abstract O-3003) (updated information presented at meeting); 6 Wilke H, et al. J Clin Oncol 2006;24(18S):(Abstract 3549) (updated information presented at meeting); 7 Sobrero AF, et al. J Clin Oncol 2008;26:2311–2319

Background (2) KRAS is a central downstream mediator of EGFR signaling –It links EGFR activation to cell proliferation and survival Cetuximab’s activity in mCRC may correlate with somatic mutations in codons 12/13 of KRAS 1–6 1 Liévre A, et al. J Clin Oncol 2008;26:374–379; 2 Benvenuti S, et al. Cancer Res 2007;67:2643–2648; 3 De Roock W, et al. Ann Oncol 2008;19:508–515; 4 Finocchiaro G, et al. J Clin Oncol 2007;25(18S) (Abstract 4021); 5 Di Fiore F, et al. Br J Cancer 2007;96:1166–1169; 6 Khambata-Ford S, et al. J Clin Oncol 2007;25:3230–3237

Background (3) Many mCRC chemotherapy regimens are once every 2 weeks We assessed the feasibility of a q2w cetuximab dosing regimen in patients with mCRC in a phase I, open-label, multicenter study Comparison with standard once-weekly (qw) regimen

Study objectives Primary objective –To determine maximum tolerated dose (MTD) a of cetuximab q2w regimen Secondary objectives –To evaluate safety, clinical efficacy, PK and PD –To investigate the relationship between KRAS mutation status and efficacy outcomes a In this case equivalent to recommended dose : q2w; pharmacodynamics, PD; pharmacokinetics, PK

Study design: Eligibility criteria Main inclusion criteria –Adults with measurable EGFR-expressing a mCRC b –ECOG PS ≤2; life expectancy ≥12 weeks –Adequate bone marrow, liver, and renal function Main exclusion criteria –Prior EGFR-targeted agents, or mCRC chemotherapy c –Surgery or irradiation within 4 weeks of study onset –Brain metastases a EGFR status confirmed by immunohistochemistry; b confirmed by histology and with at least one tumor accessible for biopsy and ≥1 bi-dimensionally measurable lesion (not in an irradiated area; c including adjuvant, within 6 months of study onset; ); Eastern Cooperative Oncology Group performance status, ECOG PS

Study design: Phase I study a Group A (control arm) n=10 Cetuximab 400 mg/m 2 initial dose then 250 mg/m 2 qw Group B (test arm) n=10 Escalating cetuximab doses: 400, 500, 600 mg/m 2 q2w 6 weeks’ treatment Complete PK profile obtained during this period Part I Primary endpoint: DLT assessment FOLFIRI added to patients’ current cetuximab regimen Secondary endpoints Evaluate best overall response Progression-free survival Part II a 20─50 patients planned depending on no. dose-limiting toxicities (DLTs); FOLFIRI: irinotecan 180 mg/m 2 over 30─90 min; FA 400 mg/m 2 over 2 hours; 5-fluorouracil 200 mg/m 2 as bolus and 2400 mg/m 2 over 46 hours, q2w

Study endpoints Primary endpoint –DLTs to determine MTD Secondary endpoints –Adverse events (AEs) –Clinical efficacy (best overall response; PFS) –PK –PD –Biomarker analyses including relationship between KRAS mutation status and efficacy outcomes Progression-free survival, PFS

Definition of DLTs and MTD DLTs –Grade 3/4 AE (except hypersensitivity reactions or grade 3 skin toxicity) –Or administration of <66% of assigned cetuximab dose due to toxicity MTD –Was reached if 2/10 patients in a cohort had a DLT –If ≥3/10 patients had a DLT, the previous cetuximab dose level was considered the MTD –Dose escalation continued if DLTs in ≤1/10 patients

Results: Patients N=62 enrolled between September 2004 and August 2006 KRAS mutation analysis –50 blocks of archived tumor material analyzed –n=2 paraffin-embedded specimen slide sets analyzed –48/52 contained tumor tissues and were evaluable a –19 specimens had KRAS mutation (40% of all evaluable) a By independent histologic evaluation

Results: Baseline patient and disease characteristics (n=62 evaluable) Group A (control) 250 mg/m 2 qw Group B (test) cetuximab mg/m 2 q2wTotal N Male/female, %46/5469/3179/2175/2540/6063/37 Median age, years (range) 67 (55–75) 66 (47–77) 69 (42–80) 59 (41–78) 64 (39–73) 65 (39–80) <65 years, % ≥65 years, % ECOG PS, % Percentages have been rounded to nearest whole number so might not total 100%

Results: DLTs One DLT in cetuximab 700 mg/m 2 q2w group –Grade 4 dyspnea –Patient died due to progressive disease –Also included AEs considered not related to cetuximab Grade 3 anemia Grade 3 liver enlargement Grade 1 productive cough Grade 4 bad general status

Tolerability results: AE overview Group A (control) 250 mg/m 2 qw Group B (test) cetuximab mg/m 2 q2wTotal b a N Any AE, n (%) Part I13 (100) 14 (100)12 (100)10 (100)62 (100) Part II Any grade 3/4 AE, n (%) 13 (100) 14 (100)11 (92)9 (100)60 (98) Part I3 (23)1 (8)1 (7)1 (8)2 (20)8 (13) Part II13 (100)10 (77)12 (86)7 (58)8 (89)50 (82) No deaths due to cetuximab-related AEs in either Part I or Part II; a n=9 in Part II; b n=61 in Part II Most common grade 3/4 AEs: diarrhea (31%), neutropenia (24%), and rash (16%)

Tolerability results: Cetuximab-related AE overview Group A (Control) 250 mg/m 2 qw Group B (test) cetuximab mg/m 2 q2wTotal b a N Any AE, n (%) Part I13 (100) 14 (100)11 (92)9 (90)60 (97) Part II Any grade 3/4 AE, n (%) 13 (100)11 (85) 12 (86)10 (83)8 (89)54 (89) Part I0 (0)1 (8)0 (0) 1 (2) Part II3 (23)0 (0)7 (50)1 (8)4 (44)15 (25) No deaths due to cetuximab-related AEs in either Part I or Part II; a n=9 in Part II; b n=61 in Part II Treatment-related grade 4 AEs: neutropenia (8%); febrile neutropenia, hypocalcemia, and pulmonary embolism (all 2%)

Efficacy results: Overall response (Part II) a Group A 250 mg/m 2 qw Group B (test) cetuximab mg/m 2 q2wTotal N BOR, n (%) CR0 (0) PR 4 (31)5 (39) 8 (57)4 (33)5 (50)26 (42) SD7 (54) 6 (43)6 (50)3 (30)29 (47) PD2 (15)0 (0) 1 (8)1 (10)4 (7) UE0 (0)1 (8)0 (0)1 (8)1 (10)3 (5) ORR, % (95% CI) 31 (9–61)39 (14–68)57 (29–82)33 (10–65)50 (19–81)42 (30–55) DCR, % (95% CI) 85 (55–98)92 (64–100)100 (77–100)83 (52–98)80 (44–98)89 (78–95) a ITT safety population; percentages have been rounded to nearest whole numbers; best overall response, BOR; complete response, CR; disease control rate, DCR (PR+CR+SD); overall response rate, ORR (PR+CR); partial response, PR; progressive disease, PD; stable disease, SD; unevaluable, UE

Efficacy results: Progression-free response (ITT safety population) Group A (Control) 250 mg/m 2 qw Group B (test) cetuximab mg/m 2 q2wTotal a N Number of events, n (%) a 12 (92) 9 (69) 4 (29) 5 (42) 8 (80) 38 (61) Median PFS, months (95% CI) 4.4 (3.2–9.5) 7.0 (4.6–12.2) 17.4 (9.2–17.4) 6.9 (4.3– ND ) 6.3 (2.7–8.4) 7.2 (6.3–9.8) a Progression or death; not yet determined, ND

Efficacy results: Tumor response stratified by KRAS status Response rate (%) 27.6 (12.7─47.2) 0 (0─17.7) 55.2 (35.7─73.6) 31.6 (12.6─56.6) p=0.015 p=0.144 KRAS wild-type (n=29) Monotherapy (Part I)Combination (Part II) KRAS mutation (n=19)

Efficacy results: PFS by KRAS status Probability of PFS Time (days) a A PFS hazard ratio <1 indicates a lower risk of progression in patients with wild-type KRAS 0.4 KRAS wild-type (n=29)KRAS mutation (n=19) Median PFS, (95% CI)9.4 (7.0–11.3)5.6 (3.3–12.2) PFS hazard ratio a 0.47 (p=0.0475) Mutation Wild-type

PK results: Mean (± SD) cetuximab concentration vs time profile at Week 5 Concentration (µg/mL) Time (h) /250 mg/m 2 q1w (n=13) 400 mg/m 2 q2w (n=8) 500 mg/m 2 q2w (n=9) 600 mg/m 2 q2w (n=10) 700 mg/m 2 q2w (n=6) Cetuximab had a predictable PK profile at all doses; t 1/2 and CL SS values were similar for qw and each q2w dosing regimen

PK results: Cetuximab median trough concentrations during weeks 1–29 Concentration (µg/mL) Time (weeks) /250 mg/m 2 q1w 400 mg/m 2 q2w 500 mg/m 2 q2w 600 mg/m 2 q2w 700 mg/m 2 q2w Cetuximab 500 and 600 mg/m 2 q2w C min values similar to qw; C min & time to steady state much higher at 700 mg/m 2 q2w

PD results: Other biomarker findings Evaluation of skin biopsy samples –Substantial changes from baseline in pEGFR, pMAPK, Ki67, p27, and pSTAT3 with cetuximab –No apparent major differences between dosing schedules

Conclusions Cetuximab 400–700 mg/m 2 q2w was safe and well tolerated; the MTD was not reached t 1/2 and CL SS values similar for qw and q2w doses C min values were much higher at q2w 700 mg/m 2 –500 or 600 mg/m 2 may be most appropriate q2w dosage Outcomes improved for wild-type vs mutant KRAS tumors Other potential biomarkers warrant further study Study supports feasibility of cetuximab q2w as a convenient alternative to weekly regimen in mCRC