Wu, Christina

Abstract Background: Colorectal cancer (CRC) is the second leading cause of cancer death among men and women in the United States, and additional treatment strategies are needed for patients with advanced disease. Prospective therapeutic studies based on tissue-detected genomic targets such as ERBB2 (HER2), BRAF V600E, gene rearrangements/fusions, and microsatellite instability (MSI) have demonstrated clinical benefit for mCRC patients. Although correlative studies and/or retrospective case series utilizing circulating cell-free DNA (cfDNA) next generation sequencing (NGS) have shown that plasma detection of these genomic targets shows promise in mCRC, prospective studies are lacking. We hypothesize that comprehensive genomic profiling of cfDNA will identify actionable targets and improve outcomes for patients with mCRC. Methods: COLOMATE (Colorectal Cancer and Liquid Biopsy Screening Protocol for Molecularly Assigned Therapy; NCT03765736) is a phase II umbrella screening protocol sponsored by the Academic and Community Cancer Research United (ACCRU) consortium. This study utilizes Guardant360™ (Guardant Health, Redwood City, CA) - a blood-based targeted NGS panel - to identify actionable genomic alterations in mCRC patients and to assess the impact of molecularly assigned therapy accordingly under its individual companion studies. Eligible mCRC patients must have progressed on, been intolerant to, or have a contraindication to treatment with a fluoropyrimidine, oxaliplatin, irinotecan, anti-vascular endothelial growth factor (VEGF) monoclonal antibodies (mAbs) and anti-epidermal growth factor receptor (EGFR) mAbs if RAS wild-type. Companion studies are dynamic and currently include those for patients whose tumors are either RAS/BRAF wild-type, HER2 amplified, FGFR altered, RAS mutated, or without any known actionable alteration. Additional companion studies are under active development. The primary objectives of this study are to perform blood-based genomic profiling on patients with treatment refractory mCRC to facilitate accrual to molecularly assigned therapies, and to obtain patient-matched tumor tissue and cell free DNA from peripheral blood to facilitate clinically annotated genomic analyses. Secondary correlative objectives are to explore mechanisms of acquired resistance to molecularly assigned therapy and to explore the correlation between cfDNA mutational burden (allele frequency, copy number) and clinical outcomes such as objective response rate, progression-free survival, and overall survival. Citation Format: Kristen K. Ciombor, Fang-Shu Ou, Andrew Dodge, Tyler Zemla, Christina Wu, Kimmie Ng, Katrina Pedersen, Shumei Kato, Pashtoon M. Kasi, Daniel Ahn, Rebecca Nagy, Richard Lanman, Scott Kopetz, John H. Strickler, Tanios Bekaii-Saab. COLOMATE: Colorectal cancer and liquid biopsy screening protocol for molecularly assigned therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-235.

Abstract Background: HER-2 is a transmembrane receptor that is overexpressed in multiple epithelial tumors. We have previously shown that a first generation HER-2 B-cell peptide vaccine targeting epitopes (628-647) and (316-339) was safe and relatively active. We recently developed a novel B-cell epitope specific vaccine (HER-Vaxx) consisting of epitopes derived from the extracellular domain of HER-2 that correspond to amino acid sequences 597-626 (pertuzumab binding site) and 266-296 (trastuzumab binding site). Methods: This first-in-human Phase 1b study evaluated the safety, optimal immunologic/biologic dose (OID/OBD) and immunogenicity of HER-Vaxx. Using a 3+3 dose escalation design, 3 patients (pts) were treated at each dose level (DL). If <2 pts experience dose-limiting toxicity (DLT), we required an additional 3 pts to be entered at that DL for OID/OBD assessment (defined as the dose level inducing a strong immunogenic response for 5 out of 6 patients). We also required that at least 6 patients at each DL to receive 3 inoculations of the combination vaccines at 3-week intervals and that < 2 of the 6 pts experience DLT before dose escalation. DLs were 1.0 mg (DL1), 1.5 mg (DL2), 2.0 mg (DL3) and 2.5 mg (DL4) of each peptide. Each dose contained 0.025 mg of n-MDP. Results: 49 patients with metastatic and/or recurrent solid tumors and a median of 4 prior lines of chemotherapy received at least one inoculation of HER-vaxx. Common related toxicities include injection site reactions (56% grade 1/2 and 5% grade 3/4). There were no DLTs. The OID/OBD was found to be DL 2 (1.5 mg of each peptide vaccine).A total of 28 patients received ≥ 3 vaccinations including 2 with a partial response and 14 with stable disease. Of those, 6 patients received at least one 6-month boost. The vaccine generated sustained humoral response eliciting HER-2 specific antibodies in the majority of responding patients. Conclusion: We demonstrate that HER-Vaxx is well tolerated and able to generate sustained anti-HER-2 immune response. Given the promise, continuous development of the vaccine is ongoing at the suggested OBD in HER-2 overexpressing tumors. Citation Format: Tanios Bekaii-Saab, Lai Wei, Robert Wesolowski, Daniel Ahn, Christina Wu, Maryam Lustberg, Amir Mortazavi, Bhuvaneswari Ramaswamy, Jay Overholser, Pravin Kaumaya. A Phase Ib of a combination of two chimeric (Trastuzumab-like and Pertuzumab-like) HER-2 B cell peptide vaccine emulsified in ISA 720 and nor-MDP adjuvant in patients with advanced solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT017.

4110 Background: Neuroendocrine tumors (NET) comprise around 2% of all malignant tumors of the gastrointestinal system. The genomic landscape of NET has not been well studied. The aim of this study was to confirm the feasibility of next generation sequencing (NGS) using ctDNA in NET and characterize common alterations in the genomic profile. Methods: Molecular alterations in 114 plasma samples from 114 patients with NET using clinical-grade NGS of ctDNA (Guardant360Ò) across multiple institutions were evaluated. The test detects single nucleotide variants in 54-73 genes, copy number amplifications, fusions, and indels in selected genes. Results: A total of 114 NET patients were evaluated, of which 64 (56.1%) were female. Mean age was 59.7 years with a range between 23-89 years. ctDNA NGS testing was performed on 114 plasma samples; 1 patient had testing performed twice. Genomic alterations were defined in 94 (n = 94/114, 82.5%) samples with a total of 289 alterations identified after excluding variants of uncertain significance (VUSs) and synonymous mutations. Alterations were identified in at least one sample from 83 patients; TP53 associated genes were most commonly altered (n = 83/289, 28.7%), followed by KRAS (n = 22, 7.6%), PI3CA (n = 15, 5.2%), CCNE1 (n = 15, 5.2%), BRAF (n = 13, 4.5%), MYC (n = 12, 4.1%), ERBB2 (n = 11, 3.8%), APC (n = 10, 3.5%), EGFR (n = 10, 3.5%), MET (n = 10, 3.5%), PTEN (n = 9, 3.1%), RB1 (n = 9, 3.1%), CDK6 (n = 7, 2.4%), AR (n = 5, 1.7%), ARID1A (n = 5, 1.7%), FGFR1 (n = 5, 1.7%), and PDGFRA (n = 5, 1.7%). Other genomic alterations of low frequency, but clinical relevance included: CDK4 (n = 4, 1.3%), NF1 (n = 4, 1.3%), RAF1 (n = 4, 1.3%), GNAS (n = 3, 1.0%), KIT (n = 3, 1.3%), BRCA2 (n = 2, 0.7%), CCND2 (n = 2, 0.7%), CTNNB1 (n = 2, 0.7%), JAK2 (n = 2, 0.7%), NRAS (n = 2, 0.7%), SMAD4 (n = 2, 0.7%), and TERT (n = 2, 0.7%). Alterations in AKT1, ALK, ATM, BRCA1, CCND1, CDKN2A, FGFR2, MTOR, RHOA, SMO and STK11 were all reported once (n = 1, 0.3%). Conclusions: Evaluation of ctDNA is feasible among individuals with NET. Liquid biopsies are not invasive and can provide personalized options for targeted therapies in NET patients.

e15029 Background: ICIs induce durable responses in dMMR CRC pts with overall response rates (ORR) of 30-50%. Even though the loss of expression of any MMR gene predicts ICIs response, it is unknown if ORRs are similar across all MMR genes (MLH1, PMS2, MSH2, and MSH6). In this study, we analyzed the impact of each specific MMR gene loss and clinical characteristics of pts with best response to ICIs. Methods: Pts were eligible if they had confirmed dMMR CRC by IHC or microsatellite instability-high (MSI-H) by PCR, and received ICIs between 01/01/2012 and 10/01/2018 at Winship Cancer Institute of Emory University, Mayo Clinic or Vanderbilt University Medical Center. Due to the pattern of frequent concurrent loss and functional dependency, the groups were categorized as MLH1 ±PMS2 vs. MSH2 ±MSH6. Cox proportional hazard model and Fisher’s exact test were used for the best response and the distribution of variable among the subgroups. Results: A total of 45 pts with dMMR CRC were identified. ORRs in MLH1 ±PMS2 and MSH2 ±MSH6 groups were 68% and 57.1% respectively without statistical difference (Table). Pts with age < 50 and 50-65 years old had better ORRs compared to pts with age >65 (58.3%, 85.7% and 42.1% respectively, P=0.036). Left-sided tumors had a trend toward higher ORRs compared to right-sided tumors (83.3% vs 51.5% P=0.086). Gender and BRAF status were not predictors of response. BRAF mutations were more common in right-sided tumors (29.6% vs 11.1% respectively) and in older patients. Conclusions: Our data suggest that MSI-H CRC pts aged 50-65 treated with ICIs, have improved ORR compared to pts > 65; pts with left-sided tumors have a trend toward improved ORR compared to those with right sided tumors. [Table: see text]

Abstract Purpose: This first-in-human phase I study (NCT 01417546) evaluated the safety profile, optimal immunologic/biological dose (OID/OBD), and immunogenicity of the combination of two peptide B-cell epitope vaccines engineered to represent the trastuzumab- and pertuzumab-binding sites. Although trastuzumab and pertuzumab have been approved for clinical use, patients often develop resistance to these therapies. We have advanced a new paradigm in immunotherapy that focuses on humoral responses based on conformational B-cell epitope vaccines. Patients and Methods: The vaccine is comprised of two chimeric HER-2 B-cell peptide vaccines incorporating a “promiscuous T-cell epitope.” Patients were immunized with the vaccine constructs emulsified with nor-muramyl-dipeptide adjuvant in a water-in-oil Montanide ISA 720VG vehicle. Eligible patients with metastatic and/or recurrent solid tumors received three inoculations every 3 weeks. Results: Forty-nine patients with a median of 4 prior lines of chemotherapy received at least 1 vaccination. Twenty-eight patients completed the 3 vaccination regimens. Six patients received 1 six-month boost after the regimen, and one patient received 7 six-month boosts. No serious adverse reactions or dose-limiting toxicities were observed. The vaccine was well tolerated with dose level 2 as the recommended phase II dose. The most common related toxicity in all patients was injection-site reactions (24%). Two patients had a partial response, 14 had stable disease, and 19 had progressive disease. Conclusions: The study vaccine is safe, exhibits antitumor activity, and shows preliminary indication that peptide vaccination may avoid therapeutic resistance and offer a promising alternative to monoclonal antibody therapies.

e15168 Background: 2-8% of all colorectal cancer (CRC) cases are in younger adults (YAs), patients (pts) less than age 50. However, current understanding of CRC in YAs is inadequate, especially that of sporadic onset. We conducted a study to describe the landscape of genomic alterations in YA CRC pts presenting to a large academic practice. Methods: Adult pts with CRC presenting to The Ohio State University Comprehensive Cancer Center oncology clinics were offered next generation sequencing (NGS) through a customized 22-gene Ion AmpliSeq Mutation Panel as part of clinical care. Commonly mutated areas of select genes (including AKT1, ALK, BRAF, EGFR, ERBB2/4, FBXW7, FGFR1/2/3, KRAS/NRAS, MET, NOTCH1, PIK3CA, PTEN, TP53) were sequenced from tumor sections. Institutional review board approval was obtained to retrospectively analyze this NGS testing between 1/2013-3/2016. Results: 258 CRC pts underwent genomic profiling. 57 pts (22.1%) were YAs at diagnosis (range 22-49 years); 20 pts (7.8%) were 40 years old or younger. 31 YA pts (54.4%) had metastatic disease. Of the YAs with CRC, 18 pts (31.6%) were diagnosed with R-sided colon, 16 pts (28.1%) with L-sided colon, and 22 pts (38.6%) with rectal cancer. 110 genomic alterations were found in YA pts, with a mean of 1.9 mutations per tumor (range 0-6); 35 (31.8%) of these in 32 (56.1%) YA pts were actionable. Of these 110 alterations, 41.8% were in TP53, 28.2% in KRAS/NRAS, 10.0% in PIK3CA, 3.6% in BRAF, 3.6% in FBXW7, and 2.73% in PTEN. 6 YA pts (10.5%) had microsatellite instability (MSI-H). Only 1 pt had concomitant MSI-H and a BRAF mutation; 4 pts with BRAF mutations were microsatellite stable. Comparing our YA pts to a separate cohort of pts age > 50 who had testing done, no significant difference was seen in mutation incidence in KRAS/NRAS (p = 1.0), TP53 (p = 0.3), PIK3CA (p = 0.128), or BRAF (p = 1.0). Conclusions: Genomic profiling through a targeted NGS panel is feasible as part of routine clinical practice. There is disagreement in the literature on genetic mutations in YA compared to older age CRC pts. Knowledge of the genomic landscape in YAs with CRC will lead to improved understanding of the underlying biology of CRC in YAs as it differs from CRC in older pts, and could impact future care of this cohort.

TPS3624 Background: To improve survival for patients with mCRC, efforts are needed to identify and treat actionable genomic alterations. HER2 is amplified in approximately 5-8% of patients with KRAS and NRAS (RAS) wild-type mCRC. HER2 functions as an oncogenic driver and a mediator of EGFR antibody (Ab) resistance. Although prior studies have shown that anti-HER2 therapies are active in patients with HER2+ (HER2 IHC 3+ or HER2 amplified) mCRC, there are no HER2-directed therapies approved for these patients. Tucatinib is a potent and highly selective oral small molecule tyrosine kinase inhibitor of HER2, currently being developed to treat metastatic breast cancer. In HER2+ CRC patient derived xenograft models, tucatinib has substantial anti-tumor activity. The addition of the anti-HER2 monoclonal Ab trastuzumab augments tumor growth inhibition. Methods: This single-arm phase II study will test the combination of tucatinib and trastuzumab in patients with HER2+ mCRC. Eligible patients include those with RAS wild-type mCRC who have been previously treated with 5-FU, oxaliplatin, irinotecan, and an anti-VEGF monoclonal Ab. Patients must have HER2+ disease by IHC, FISH, or NGS. Prior treatment with anti-HER2 targeting therapy is excluded. The primary objective is to assess the objective response rate for the combination. Secondary objectives are to evaluate the efficacy (PFS, OS, clinical benefit rate), safety, and tolerability of the combination. Correlation between tissue and blood-based biomarkers and clinical outcomes will be explored. Blood will be collected at baseline and each restaging to determine if the combination eliminates HER2 amplified circulating tumor DNA. Subjects will receive tucatinib at a dose of 300mg by mouth daily, and trastuzumab will be administered every 3 weeks (8 mg/kg IV day 1 of cycle 1, then 6 mg/kg IV Q3 weeks). Response will be assessed every 3 cycles (9 weeks) per RECIST version 1.1. Both agents will be provided by the study. This study was initiated in February 2017. Recruitment is ongoing at 8 sites in the Academic and Community Cancer Research United (ACCRU) network. Clinical trial information: NCT03043313.

3612 Background: The RAS/RAF/MEK signal transduction pathway is critical to the development of colorectal cancer, and tumors harboring KRAS, NRAS, and BRAF mutations were shown to be resistant to radiation. Thus, we conducted a phase I study of trametinib, a potent MEK1/2 inhibitor, in combination with CRT in patients with LARC. Methods: Phase I trial for patients with Stage II/III rectal cancers with a 3+3 design, and an expansion cohort of 12 patients at the maximum tolerated dose (MTD). Trametinib is given orally at 3 dose levels: 0.5mg, 1mg, and 2mg (Mon-Fri). CRT regimen is infusional 5-flourouracil (5FU) 225mg/m2/day (Mon-Fri) and daily fractions of 1.8 Gy (total 50.4Gy). There is a 5-day trametinib lead-in followed by trametinib and CRT. Six to 10 weeks after completion of CRT, patients then proceed to their surgery and adjuvant therapy. The primary endpoint is to identify the MTD and recommended phase 2 dose of trametinib with CRT. Immunohistochemistry staining for phosphorylated –ERK (pERK) and genomic profiling is performed on the tumor samples. Results: Enrollment is complete at all dose levels with18 patients, and 15 patients evaluable for toxicity and response as of Feb 6. One dose-limiting toxicity of diarrhea was observed at the 2mg dose. Grade 3 and most common toxicities are shown in Table 1. No grade 4/5 toxicities have been observed. At 2mg dose level, 3/9 (33%) patients had pathological complete response (pCR) and 2/9 (22%) had a near pCR. Correlative studies confirm decrease in pERK levels with increasing doses of trametinib. Correlation of genomic mutational status with toxicity, response, and outcomes is being analyzed. Conclusions: The combination of trametinib with 5FU CRT is tolerable with promising preliminary activity. Final results will be presented at the meeting. Toxicities. Clinical trial information: NCT01740648. [Table: see text]

Abstract Introduction: 5-fluorouracil (5-FU)-based chemoradiation (CRT) is a standard neoadjuvant treatment strategy for the treatment of locally-advanced rectal adenocarcinomas (LARC). MEK-1/2 inhibition has been shown to radiosensitize Ras mutant tumors in preclinical models, including colorectal cancer. In this phase 1 trial, we are testing MEK-1/2 inhibition in combination with neoadjuvant CRT for LARC. Methods: This trial is a standard 3+3 design testing 3 dose levels of the MEK-1/2 inhibitor trametinib in combination with CRT: 0.5 mg, 1.0 mg, and 2.0 mg daily, followed by an expansion cohort. All patients first receive a one week lead-in dosing of trametinib monotherapy, and undergo a tumor biopsy at the end of that week to assess pharmacodynamic inhibition by immunohistochemistry (IHC). Then, patients receive standard CRT (5-FU 225 mg/m2 per day by continuous infusion during radiotherapy, and 50.4 Gy in 28 fractions, 5 days/ week) in combination with trametinib (5 days/week). Patients have total mesorectal excision (TME) 6-10 weeks after completion of CRT. Results: 17 patients have been enrolled to date, with current enrollment occurring on the trametinib 2 mg expansion cohort (total 18 patients planned). Of these, 15 patients (10 males, 5 females) have toxicity and surgical response data available. Median age is 53 years (range 35-74 years), and 6 patients have Stage II disease, while 9 patients with Stage III disease. There have been no grade 4-5 toxicities. One dose-limiting toxicity (DLT) of diarrhea occurred in the 2mg dose cohort, attributed mainly to 5FU CRT, but led to trametinib discontinuation. Generalized skin rash led to trametinib discontinuation after 2 weeks of therapy for 1 patient and was held for 3 days for 2 patients. All patients completed TME, and 3 patients had wound infection at 2 weeks after TME, while 2 patients had perineal wound infection at 4 weeks after TME. Three out of 9 (33%) patients at the 2mg dose cohort had a pathologic complete response (pCR), and 2/9 (22%) patients had a near pCR. Adjuvant chemotherapy was given to 10 patients, 4 patients did not receive (3 refused), and 1 patient is pending. Correlative research studies have been performed in the first 12 patients enrolled. Examination of phospho-ERK levels using Vectra quantitative immunohistochemistry in pre-treatment versus post-lead-in trametinib tumor tissue reveals dose-dependent decreases in p-ERK expression in both tumor and stromal tissue as trametinib is increased from 0.5 to 2.0 mg (range 18-46% absolute reduction), with maximal reduction observed in the 2 mg cohort. Additionally, we have performed whole exome sequencing of a custom panel of 279 cancer associated genes (IGNITE platform) in tumor and normal tissue, and have identified high frequency mutations in KRAS, BRAF, and TP53, as well as additional lower frequency mutations in every tumor. One patient was noted to have microsatellite instability. Finally, we will present data correlating degree of change in p-ERK staining, mutational analysis, and mismatch repair status with pathologic response. Conclusions: The combination of trametinib with 5-FU-based CRT for LARC is feasible with promising signs of clinical activity and tolerability. Initial analysis of tumor tissue confirms dose-dependent pharmacodynamic inhibition of ERK-1/2 within 5 days of starting trametinib. Citation Format: Terence M. Williams, Christina Wu, Lai Wei, Emily Chan, Ryan Robb, Sameek Roychowdhury, Amy Webb, Cynthia Timmers, Tanios Bekaii-Saab, Evan Wuthrick. A phase I trial combining MEK-1/2 inhibition in combination with 5-fluorouracil and radiation for locally-advanced rectal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr CT088. doi:10.1158/1538-7445.AM2017-CT088