New Advances in Research and Clinical Insights in Gastrointestinal Stromal Tumor (GIST) Ping Chi, M.D., Ph.D. Human Oncology and Pathogenesis Program (HOPP) & Department of Medicine, Sarcoma Medical Oncology Memorial Sloan Kettering Cancer Center May 24, 2017 Gastrointestinal Stromal Tumor (GIST) Management • Surgery mainstay treatment • Recurrence or metastatic disease - fatal • Refractory to chemotherapy and radiation • ~5,000 cases diagnosed per year in the US. • One of the most common subtypes of soft tissue sarcomas, the most common mesenchymal neoplasm in the GI tract. • Can arise anywhere from the entire GI tract; stomach is the most common primary site (2/3), then small bowel (1/4), esophagus/colon/rectum (the rest). •Peak incidence 50-65 year old. •Familial syndromes Pre-KIT ERA: GIST- A clinicopathological challenge GIST has broad morphological spectrum Sclerosing Palisaded-vacuolated •Difficult to diagnose! Spindle •Difficult to treat! Hypercellular Sarcomatous Clinicopathologically distinct entity! Sclerosing dyscohesive pattern Epithelioid Hypercellular Sarcomatous Miettinen, M. and Lasota, Arch Pathol Lab Med 2006 GIST originates from ICC and highly expresses KIT • Originates from the Interstitial Cells of Cajal (ICCs) of the GI tract • Characterized by KIT positive IHC and activating mutations in KIT or PDGFRA… Interstitial Cell of Cajal (ICC)- GIST of stomach Pacemaker cells of the GI tract H&E α-KIT Hirota, S., et al., Science, 1998 A Paradigm: Normal ICC development vs. GIST Normal ICC development GIST KIT/PDGFRA mutation External KIT/PDGFRA stimuli P P Signaling Aberrant signaling STAT STAT PI3K MAPK PI3K MAPK ETV1 ON ON/OFF TFs TF Chromatin TF Molecular characterization of GIST Corless et al, Nat Rev Cancer, 2011 Imatinib (Gleevec) in GIST • Activity – Abl kinase, KIT, PDGFRA TTF OS Historical OS with Doxorubicin Imatinib-FDA approved as 1st line therapy for GIST 2002! Challenges - Imatinib resistance in GIST 14% - Primary resistance; 50% - Develop imatinib resistance after 2 years Corless et al, NRC, 2011 Resistance Mechanisms: 1. Secondary mutations (50-65%) 2. Genomic Amplification of RTKs 3. Activation alternative signaling pathways 4. Kit-low, imatinib-resistant GIST stem/progenitors 5. Others… How to overcome imatinib resistance? 1) More effective first line therapy than imatinib •Reduce the persistence of disease •Reduce the adaptive responses to imatinib 2) Next generation of targeted therapy for imatinib resistant mutations, KIT exon 14 and exon 17 secondary mutations, PDGFRA D842V mutation A Clinical Conundrum KIT (regulates multiple cell lineages) ICC Melanocyte Germ cell Mast cell Familial GIST - - - GIST activating KIT mutants What is special about the ICC lineage and GIST? ETV1- A Lineage specific survival factor in GIST and ICC ETV1: an “ETS family transcription factor” ExpO (Expression Project for Oncology) 4 p=5.4x10-7 Transcription of genes 2 0 ETV1 (Z-Score) -2 -4 GIST Liver Lung Renal Breast Gastric ETV1 Normalized Expression ETV1Normalized Thyroid Ovarian Bladder Cervical Prostate Sarcoma Colorectal Melanoma Pancreatic Lymphoma Endometrial Head and Neck and Head KIT wt KIT wt KITmutant ∆560 P P MEK MEK P P MEK P + ERK ERK ERK ETV1 ETV1 Decreased ICC survival Normal ICC development ICC hyperplasia and GIST Chi, P, Chen, Y et al, Nature 2010 Ran L et al., Cancer Discovery, 2015 ETV1 is required for GIST growth and survival GEMM: KitΔ558/+ GIST882 cell (imatinib sensitive) Cecum (Etv1+/+;KitV558Δ/+) Cecum (Etv1-/-;KitV558Δ/+) X) 4 ( H&E X) 20 ( Normalized cell Normalized growth Day H&E GIST48 cell (imatinib resistant) GEMM: KitΔ558/+;Etv1flox/flox;Rosa26CreERT2/CreERT2) Cecal tumor (Ki67 IHC) Cecal tumor (trichrome) control control Etv1 deleted Etv1 deleted Normalized cell Normalized growth Day Chi, P, Chen, Y et al, Nature 2010 Ran L et al., Cancer Discovery, 2015 ETV1 and KIT forms a positive feedback circuit in GIST Mutant KIT GIST882 cells Imatinib (500nM) MEK162 (1µM) Adaptive 1 2 8 1 2 8 0 0 24 24 Time (hr) 0.5 0.5 responses P + P pKIT P KIT Feedback negative pERK MAPK regulators ERK ETV1 ACTIN Excised 3T3 allograft tumors ETV1 Vector KITwt GIST KIT∆560 ETV1 ETV1 cooperates with KIT/MAPK signaling in GIST •KIT/MAPK activation stabilizes ETV1 protein ETV1+KITwt •ETV1 directly upregulates KIT expression •Positive feedback (ETV1 and mutant KIT) •Target the adaptive responses in response to TKIs ETV1+KIT∆560 •Targeting ETV1 protein stability – novel therapeutic approach Chi, P, Chen, Y et al, Nature 2010 Ran L et al., Cancer Discovery, 2015 Unpublished result Synergy of combined MAPK and KIT pathway inhibition GIST882 cells GIST882 xenografts MEK162 (1µM) Vehicle 800 MEK162 Imatinib 0 1 2 8 24 Time (hr) 0.5 Imatinib + MEK162 (dose 1) Imatinib + MEK162 (dose 2) pKIT 600 Imatinib + MEK162 (dose 3) KIT pERK 400 *** ERK P<0.0001 ETV1 200 ACTIN ** * 0 0 5 10 15 % original tumor size tumor original % 20 25 30 35 40 45 50 Imatinib (nM) 0 62.5 125 1000 Days Vehicle Vehicle Imatinib MEK162(µM) 125 0 0 0 0 1.0 0.5 0.5 0.5 1.0 0.5 1.0 MEK162 (0.5 µM) 1.0 MEK162 (1 µM) pKIT 100 MEK162 (2 µM) KIT 75 pERK 50 MEK162 Imatinib+MEK162 ERK 25 ETV1 0 Viability (% control) ACTIN 0 125 250 500 62.5 1000 Imatinib (nM) Chi, P, Chen, Y et al, Nature 2010 Ran L et al., Cancer Discovery, 2015 Molecular biomarker driven novel therapies in GIST More effective first line therapy than imatinib -A phase Ib/II study of MEK162 (binimetinib) in combination with imatinib in patients with advanced gastrointestinal stromal tumor (GIST) (Clinicaltrials.gov#: NCT01991379) - Phase Ib-completed and defined safety and tolerability and modest efficacy in imatinib-resistant GIST, presented in the 2015 ASCO sarcoma oral abstracts. - Phase II in imatinib-naïve patient population is actively accruing. Phase Ib/II study of MEK162 in combination with imatinib in patients with untreated locally advanced and metastatic GIST Primary Objective: Phase Ib: safety and tolerability of combining MEK162 (a MEK inhibitor) and imatinib, MTD and the recommended Phase II dose (RP2D) in GIST patients. Phase II: ORR (CR + PR) by both RECIST 1.1 PBMC Post-treatment Post-treatment biopsy document Pretreatment biopsy biopsy wk 1 recurrence Pretreatment baseline FDG PET at wk4 Evaluate evaluation (FDG PET, Response Rate: CT/MRI, blood, Blood for imatinib Blood for imatinib CT/MRI q8 wks, Echo/MUGA) trough x2 trough x2 (wk3 then q 12 wks and wk5) Advanced GIST Untreated Imatinib alone Imatinib/ MEK162 Disease (progressed on RP2D advanced lead in (2- week) 1 cycle=4wks progression imatinib) GIST Phase Ib Phase II Completed Ongoing Chi/Tap Patient Characteristics (Phase Ib) Characteristics All Patients n=18 Age (yrs) Median: 60; Range: 30-74 Sex Female: 8; Male: 10 ECOG status 0-1 Number of prior therapy Median: 3; Range: 1-6;15/18 pts ≥ 3 prior therapies Prior therapies: Imatinib 18 Sunitinib 16 Regorafenib 9 Sorafenib 7 Pazopanib 4 Vemurafenib 1 Dasatinib/Ipilimumab trial 2 Linsitinib trial 1 Molecular characteristics: KIT(13, 10/13 with known imatinib-resistant KIT mutations); NF1 loss (1); BRAFV600E/NF1 loss (1); SDH-deficient (1), Unknown (2) Efficacy signal from phase Ib trial of MEK162+Imatinib in GIST a b 120 Choi responses 7/17 (41%) 100 Median PFS : 8 weeks 95% CI: 7 to 56 weeks 80 60 40 (RECIST) 20 % Progression Free Free Progression % Best RECIST (%) RECIST Best 0 -20 Time to Progression (weeks) Maximum Change from Baseline -40 c Dose Pt Prior Therapies Mutational Status Duration Best RR Best Escalation # (wks) (RECIST) RR Cohort (CHOI) Imatinib Imatinib, Sunitinib, SDHA R31X;SDHB >135 SD 4 PR 400mg QD Linsitinib trial loss by IHC (active) (-20%) + Imatinib, Sunitinib, SD MEK162 8 KIT exon11, L576P 55 PR 45mg BID Sorafenib (-16%) Patients who have imatinib-resistant KIT mutations all progressed within 16 weeks. ETV1 is highly expressed in KIT/PDGFRA wild-type GIST 8 KIT 6 4 2 0 ETV1 4 ETV1 3 Relative RNA expression RNA Relative 2 1 Ostrowski J et al., BMC Cancer 2009 0 Leili Ran/Yu Chen Combination Treatment of Imatinib and Binimetinib (MEK162) Timeline of Rx POD on DebulKing Sunitinib, Surgery Started trial & Imatinib (11/20/2012) (1/28/2014) Biopsy (11/5/2015) Linsitinib imatinib+ binimetinib (MEK162) Months: -14 -9 0 22 32 (RECIST: -19%) Target lesion #1 Non-target lesion #1 CT scans of the liver lesions (liver window) liver lesions the of scans CT Before treatment ~12 months ~24 months (RECIST: -20%) (RECIST: -14%) Exceptional response in a patient with SDH-deficient GIST Timeline of Rx POD on DebulKing Sunitinib, Surgery Started trial Biopsy (11/5/2015) & Imatinib (11/20/2012) (1/28/2014) SDHA 100% Linsitinib imatinib+ binimetinib (MEK162) TTN 100% Months: -14 -9 0 22 32 P-0002594-T01-IM3 (Pre) STAM 100% P-0002594-T02-IM5 (Post) SDHA exon 2 p.R31X SDHA 100% IMPACT: SDHA exon 2 p.R31X KDR exon 30OR13C3 p.V1334E100% * TTN 100% *IMPACT genes Liver/peritoneal met PeritonealSLCO6A1 met100% (<5% necrosis) (100% necrosis) STAM 100% ITGB6 100% OR13C3 100% FAT2 100% SLCO6A1 100% LRP10 50% ITGB6 100% WES of FFPE FAT2 100% CASKIN1 50% SDHB IHC Liver met LRP10 50% Archer negative (70%SCNN1G necrosis)50% for fusion CASKIN1 50% GRIK5 50% SCNN1G 50% SH3RF3 50% GRIK5 50% SH3RF3 50% SPON2 50% SDHA IHC Ki67<10% (liver met) SPON2 50% KDR 50% *KDR 50% UPP1 50% UPP1 50% ASNS 50% ASNS 50% Genetic Alteration 500 µm Genetic500 Alteration µm Shallow Deletion Truncating Mutation Inframe MutationShallowMissense Deletion Mutation Truncating Mutation Inframe Mutation Missense Mutation Cristina R. Antonescu Camacho Ordonez/Berger How to overcome imatinib resistance?