Circulating Tumor DNA Analysis From Pts With mCRC Who Were Treated With Panitumumab in ASPECCT CCO Independent Conference Highlights* of the 2017 ASCO Annual Meeting; June 2-6, 2017; Chicago, Illinois *Clinical Care Options (CCO) is an independent medical education organization that provides conference coverage and other unique educational programs for healthcare professionals mCRC, metastatic colorectal cancer. This activity is supported by educational grants from AbbVie, Amgen, AstraZeneca, Celgene Corporation, Genentech, Halozyme, Incyte, and Merck & Co., Inc.

Circulating Tumor DNA Analysis in Pts With mCRC Treated With Panitumumab: Background ASPECCT: randomized, open-label phase III study of anti-EGFR mAbs panitumumab (n = 499) vs cetuximab (n = 500) in pts with chemorefractory wild-type KRAS exon 2 mCRC[1,2] Noninferior OS of panitumumab demonstrated KRAS exon 2 analysis in FFPE tissue has been standard of care for pts undergoing anti-EGFR treatment Current studies used NGS to detect ctDNA in plasma of panitumumab-treated subjects from ASPECCT[3,4] Investigated overall mutational landscape and relationship between RAS mutations and outcomes ct, circulating tumor; FFPE, formalin-fixed paraffin-embedded; mCRC, metastatic colorectal cancer; NGS, next-generation sequencing 1. Price TJ, et al. Lancet Oncol. 2014;15:569-579. 2. Price T, et al. Eur J Cancer. 2016;68:51-59. 3. Boedigheimer M, et al. ASCO 2017. Abstract 3523. 4. Price TJ, et al. ASCO 2017. Abstract 3584. Slide credit: clinicaloptions.com

ASPECCT ctDNA Analysis: Methods 238/499 panitumumab-treated pts from phase III ASPECCT study had baseline and posttreatment plasma samples 24 posttreatment samples unevaluable Plasma analyzed by NGS for mutations with 63-gene panel, 0.1% limit of detection Mutation gain or loss assessed at amino acid level Net change: (sum of mutations gained) – (sum of mutations lost) Net gain and/or net loss of mutations in single gene possible for individual pts Each RAS allele reported as (mutant reads/total reads) fraction ct, circulating tumor; NGS, next-generation sequencing. Slide credit: clinicaloptions.com Boedigheimer M, et al. ASCO 2017. Abstract 3523. Price TJ, et al. ASCO 2017. Abstract 3584.

ASPECCT ctDNA Analysis: Population Characteristics Plasma analysis population mirrored ITT population in BL demographics and tumor characteristics with numerically higher clinical outcome metrics Characteristic Plasma Analysis Population ITT Population Median age, yrs 61 Male sex, % 63 Race, % White Asian Other 48 50 1 53 45 2 ORR, % (95% CI) 28.6 (22.8-34.9) 16.1 (11.8-21.2) Median PFS, mos (95% CI) 4.8 (4.7-5.0) 3.1 (3.0-3.6) Median OS, mos (95% CI) 11.5 (10.3-13.7) 8.4 (7.0-11.1) BL, baseline; ITT, intent to treat. Slide credit: clinicaloptions.com Boedigheimer M, et al. ASCO 2017. Abstract 3523. Price TJ, et al. ASCO 2017. Abstract 3584.

ASPECCT ctDNA Analysis: Pre/Posttreatment Mutational Landscape Pts with multiple mutations in same gene: 29% at BL, 41% posttreatment Max number of mutations per gene in any single pt: 1-16 8 genes arising in analysis known to be commonly mutated: TP53, APC, KRAS, PIK3CA, FBXW7, NRAS, SMAD4, and CTNNB1 ≥ 90% of pts had TP53 mutations at BL and posttreatment, with elevated number of mutations per pt ≥ 10% of pts acquired mutations in ≥ 1 of these genes (by frequency): APC, EGFR, ALK, HER4, TP53, AR, KRAS, BRAF, PDGFRA, STK11, ESR1, FBXWT, and KIT ≥ 40% of pts acquired mutations in APC and EGFR BL, baseline; ct, circulating tumor; PD, progressive disease; PR, partial response; SD, stable disease Slide credit: clinicaloptions.com Boedigheimer M, et al. ASCO 2017. Abstract 3523.

ASPECCT ctDNA Analysis: Survival and Pre/Posttreatment Mutational Landscape Significant mutational net gains across multiple gene pathways EGFR pathway: KRAS, EGFR, NRAS, BRAF, MAP2K1, PIK3CA, and AKT1 Non-EGFR pathways: APC, CDK6, SMARCB1, FBXW7, TERT, RB1, CTNNB1, and IDH1 28% of pts experienced overall mutational decline with panitumumab Strong association between OS and total mutations across all genes (HR: 2.26; P < .001) BL, baseline; ct, circulating tumor; PD, progressive disease; PR, partial response; SD, stable disease Slide credit: clinicaloptions.com Boedigheimer M, et al. ASCO 2017. Abstract 3523.

ASPECCT ctDNA Analysis: RAS Mutations Baseline Plasma Posttreatment Plasma Wild type (n = 111) Evaluable (n = 164) Pts treated with panitumumab with BL/posttreatment plasma samples (N = 238) Wild type (n = 188) Emergent RAS mutant (n = 53) Unevaluable (n = 24) RAS mutant (n = 50) BL, baseline; ct, circulating tumor. Slide credit: clinicaloptions.com Price TJ, et al. ASCO 2017. Abstract 3584.

ASPECCT ctDNA Analysis: RAS Mutations and Clinical Response Pts with no RAS mutations: 52% RAS mutations not required for PD, but did not prevent SD or response Global increase in RAS-mutant DNA fraction from BL to posttreatment Similar increases, BL levels (P = .09) in pts with SD vs PD Circulating Levels of Mutant RAS by Best Response and Visit 100 64 32 16 8 Percent Mutant Reads 4 2 1 BL, baseline; ct, circulating tumor; PD, progressive disease; SD, stable disease; SFU, safety follow-up; W, week; WT, wild-type. W1 SFU W1 SFU W1 SFU W1 SFU WT Total 28 50 27 56 94 118 64 116 60 64 38 61 3 1 PD SD PR CR Slide credit: clinicaloptions.com Price TJ, et al. ASCO 2017. Abstract 3584. Reproduced with permission.

ASPECCT ctDNA Analysis: RAS Mutations and Survival OS, 1-yr survival probability not predicted by BL mutant RAS fraction Circulating Levels of Mutant RAS by OS 100 64 32 16 8 Percent Mutant Reads 4 2 1 BL, baseline; ct, circulating tumor; SFU, safety follow-up; W, week; WT, wild-type. W1 SFU W1 SFU W1 SFU WT Total 93 132 68 132 74 85 48 83 18 14 19 0-1 year 1-2 years 2-3 years Slide credit: clinicaloptions.com Price TJ, et al. ASCO 2017. Abstract 3584. Reproduced with permission.

ASPECCT ctDNA Analysis: Conclusions In panitumumab-treated pts with mCRC, significant mutational changes under anti-EGFR selection[1] Tumor heterogeneity increased in some, decreased in others Poorer OS associated with elevation in total mutations Investigators concluded that intraclonal competition, diversification, lineage truncation all potentially occurring BL RAS mutation level did not correlate with clinical outcome[2] Investigators concluded that RAS mutation levels cannot be used at this time to establish treatment decision threshold BL, baseline; ct, circulating tumor; mCRC, metastatic colorectal cancer. Slide credit: clinicaloptions.com 1. Boedigheimer M, et al. ASCO 2017. Abstract 3523. 2. Price TJ, et al. ASCO 2017. Abstract 3584.

Go Online for More CCO Coverage of ASCO 2017! Short slideset summaries and additional CME-certified analyses with expert faculty commentary on key studies in: Breast cancer Gastrointestinal cancer Genitourinary cancer Gynecologic cancers Hematologic malignancies Lung cancer Skin cancer clinicaloptions.com/oncology