Impact of neoadjuvant chemotherapy and stereotactic body radiation therapy (SBRT) on R0 resection rate for borderline resectable and locally advanced pancreas cancer

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Background: Management for borderline resectable pancreas cancer (BRPC) and locally advanced pancreas cancer (LAPC) is controversial. Multiagent chemotherapy (CT) followed by SBRT may allow for tumor downstaging and the ability to perform an R0 resection. Methods: We retrospectively evaluated BRPC and LAPC patients (pts) treated on our multidisciplinary treatment pathway. Pts underwent 2-3 months of CT. Pts without systemic progression received five fractions of SBRT, delivered every other day, to a dose of 30-33 Gy. After restaging, pts underwent surgery if resectable. Overall survival (OS), distant metastasis free survival (DMFS) and local progression free survival (LPFS) were estimated and compared by Kaplan-Meier and log-rank methods. Results: We identified 80 pts with BRPC (65) or LAPC (15) treated with neoadjuvant CT + SBRT between 2011-2017. Median follow up was 20 months. CT primarily included FOLFIRINOX (65%) and gemcitabine/nab-paclitaxel (30%). Of pts completing CT + SBRT, 67 (84%) went to surgery and 53 (79%) of those pts underwent definitive surgery including seven LAPC patients. The remaining 14 pts underwent palliative or exploratory surgery due to intraoperative metastases (43%) or vascular involvement (57%). Of pts undergoing definitive surgery, 51 had R0 resection (96%) and 5 (9%) had a complete pathologic response (PR) to CT + SBRT. The R0 resection rate of the cohort was 64%. OS was 24.5 months. Pts with a complete or marked (14%) PR had significantly better OS than those with a moderate (40%) PR (41.3 vs 30 months, p = 0.04) and pts unable to undergo definitive surgery (18.2 months, p < 0.001). Zero of 11 pts who had a marked or complete PR had local progression, significant compared to those with moderate PR (p = 0.012). DMFS between these two groups was not statistically significantly different. Conclusions: Neoadjuvant CT + SBRT are associated with favorable PR rates and R0 resection rates. Marked or complete PR was associated with improved LPFS and OS compared to moderate PR and pts who did not undergo definitive surgery. DMFS was not significantly different between complete and marked PR compared to those with moderate PR.

Impact of multidisciplinary management in the diagnosis and treatment of neuroendocrine tumors (NET)

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Background: The incidence and prevalence of NETs is increasing and diagnosis and pathologic evaluation of NETs is complex. Given the new advances in local and systemic therapies, multidisciplinary management models have been suggested to assist in treatment decisions. However, scientific data showing definite change in management with multidisciplinary clinic (MDC) review is lacking. We aim to address this need in this study. Methods: 113 GI-NET patients from 2012-18 were reviewed from a dedicated MDC where patients are seen simultaneously by multiple subspecialties, and data on patient characteristics, radiology, tumor pathology and treatment strategies were collected. Change in diagnosis was defined as any change in radiographic or pathologic findings that resulted in a change in the tumor type, grade, site or stage of cancer. Change in management was defined as any recommended change in treatment approach for NETs compared to the prior treatment plan. For patients who did not have a prior treatment plan or were seen directly at MDC, a change of management was considered as yes only if there was a change in diagnosis post MDC. Results: The mean age of patients evaluated was 61, with locally advanced or metastatic disease seen in 81% of patients. Small bowel and pancreatic NETs were the most common primaries (36% each). Significant proportion of NETs were well-differentiated (72%) with < 2 mitosis/10 HPF (47.3%) and Ki-67 of < 3% (36%). Patients were referred to MDC at an average of 2.5 years from diagnosis, with 23% having the MDC as their first visit. 40% had prior resection of primary, 25% were on somatostatin analogues (SSAs) previously and 9% of patients had received prior liver directed therapy (LDT). A significant proportion of patients had change in diagnosis post MDC evaluation: change in site (7%), stage of disease (7%), tumor type (3.5%) and grade (0.1%). A change in management was recommended in 50% of patients, with SSAs recommended in 43.8%, surgery in 25.4% and LDT in 17.5% of the patients. Conclusions: The use of a dedicated MDC to manage NETs had a substantial impact in change in management in a significant percentage of patients evaluated. MDC care for patients diagnosed with NET is recommended for optimal management.

Phase Ib study of WNT inhibitor ipafricept (IPA) with nab-paclitaxel (Nab-P) and gemcitabine (G) in patients (pts) with previously untreated stage IV pancreatic cancer (mPC)

369

Background: The first-in-class recombinant fusion protein IPA blocks WNT signaling by binding WNT ligands, and in combination with Nab-P/G caused tumor regression in pt-derived PC xenografts. This open-label Phase 1b dose escalation study evaluated the combination of IPA with Nab-P/G in untreated mPC pts using a standard 3+3 design. Methods: Dose escalation in cohort 1 started with Nab-P 125 mg/m2 and G 1000 mg/m2 given on days 1, 8 ,15, with IV IPA (3.5 mg/kg) on days 1 and 15, in 28-day cycles. Due to fragility fractures seen in other studies with similar targeted agents, cohorts 2-4 were 6-pt cohorts treated with weekly Nab-P/G + IPA 3 mg/kg (cohort 2) or 5 mg/kg (cohorts 3 and 4) on day 1. These cohorts included strict bone marker monitoring and use of bisphosphonates as indicated. Based on pre-clinical data suggesting improved efficacy with sequential dosing, pts in Cohort 4 received IPA on day 1 followed by weekly chemotherapy starting on day 3 of 28-day cycles. Objectives included safety, maximum tolerated dose, recommended phase 2 dose, pharmacokinetics, immunogenicity, pharmacodynamics, and preliminary efficacy. Results: Twenty-six pts in four dose escalation cohorts were enrolled, five in the cohort one and seven each in cohorts 2-4. Median age was 61.7 years and a majority were male (73%). Reported IPA-related AEs of any grade occurring in ≥ 20% of pts included fatigue, nausea, vomiting, anorexia and pyrexia. IPA-related AEs grade ≥ 3 included 2 events of AST elevation, and 1 each of nausea, maculopapular rash, vomiting and WBC decrease. No dose limiting toxicities or fragility fractures were observed. Of 26 evaluable pts, 9 (34.6%) had a partial response and 12 (46.2%) stable disease, with clinical benefit rate of 80.8%. The study was closed due to termination of the program by the sponsor. At time of data cut off, median progression free survival was 5.9 months (95% CI 3.4-18.4), median overall survival was 9.7 months (95% CI: 7.0-14). One pt remains on therapy under compassionate use with ongoing response. Conclusions: IPA can be safely administered with Nab-P and G in pts with mPC. Additional studies targeting the WNT pathway in pancreatic cancer are warranted. Clinical trial information: NCT02050178.

A phase Ib dose escalation study of vantictumab (VAN) in combination with nab-paclitaxel (Nab-P) and gemcitabine (G) in patients with previously untreated stage IV pancreatic cancer

249

Background: Vantictumab is a fully human monoclonal antibody that inhibits Wnt pathway signaling through binding FZD1, 2, 5, 7, and 8 receptors. A phase Ib study of VAN in combination with Nab-P and G was performed in patients with untreated stage IV pancreatic adenocarcinoma. Methods: Patients received VAN at escalating doses (3-7 mg/kg) in combination with standard dosing of Nab-P and G according to a 3+3 design. Due to fragility fractures occurring in this and other related clinical trials, dosing on an every 2 week schedule in cohorts 1 and 2 was transitioned to every 4 week dosing for cohorts 3 through 5. In these later cohorts, a minimum of six patients were treated at each dose level and additional criteria for maximum tolerated dose (MTD) integrating bone safety parameters were added. The bone safety plan was also revised for these cohorts. Sequential dosing of VAN followed by Nab-P and G was explored in cohort 5. Results: Thirty-one patients (52% male, 48% female) were enrolled and treated in 5 dosing cohorts. Median age was 66. Most common study-treatment related adverse events were nausea (68%) and fatigue (52%). One dose limiting toxicity (DLT) event occurred in the study population—grade 3 dehydration in 1 of 9 patients in cohort 4 (5 mg/kg q4w). Fragility fractures attributed to VAN occurred in two patients in cohort 2 (7 mg/kg q2w). Once the dosing schedule was revised to every 4 weeks, the maximum administered VAN dose was 5 mg/kg. No fragility fractures attributed to VAN occurred in these cohorts; pathologic fracture not attributed to VAN was documented in 2 patients. The study was terminated due to lack of an acceptable therapeutic index. Partial response was documented in 13 patients (42%) and stable disease in 11 (36%). Conclusions: The MTD of VAN plus Nab-P and G was not determined, but the maximum administered dose (MAD) of VAN, 7 mg/kg every 2 weeks, was considered unsafe related to bone toxicity, a known effect of WNT inhibition. After the study was revised, the MAD was 5 mg/kg every 4 weeks, with no protocol-specified bone toxicity observed (n = 16). Clinical trial information: NCT02005315.

Impact of radiation dose during neoadjuvant chemoradiation on postoperative complications in esophageal (EC) and gastroesophageal junction cancers (GEJC)

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Background: Neoadjuvant chemoradiation (nCRT) followed by resection is standard of care for operable stage II-III EC and GEJC; however, it can be associated with significant risk of postoperative complications (POC). The CROSS study group reported no increase in POC severity with nCRT using 41.4 Gy compared to surgery alone as defined by the Comprehensive Complication Index (CCI). We applied the CCI metric to evaluate the impact of nCRT radiation dose of < 50 Gy vs. ≥ 50 Gy on POC rates and compared to the CROSS rates. Methods: We retrospectively reviewed 82 pts (2004-2016) with EC or GEJC treated with nCRT followed by resection at our institution. 29 (35%) pts were treated with < 50 Gy (range 39.6-46.8 Gy) and 53 (65%) were treated with ≥ 50 Gy (range 50.0-52.5 Gy) delivered using IMRT/VMAT (41%), 3D-CRT (46%), or tomotherapy IMRT (12%). Concurrent chemotherapy were carboplatin/paclitaxel (59%), cisplatin/5-FU (17%), or other (24%). Resection was performed by Ivor Lewis esophagectomy (67%), esophagogastrectomy (14%), or trans-hiatal approach (11%). POC within 30 days were graded using the Clavien-Dindo scale and CCI scores were computed and compared between the two dose groups and with the CROSS nCRT group. Results: CCI scores and complication rates between our < 50 Gy and ≥ 50 Gy groups were not significantly different. Assuming a normal distribution of the CROSS CCI scores, there was no significant difference in CCI scores between the CROSS study nCRT, < 50 Gy, or ≥ 50 Gy groups. Rates of pulmonary complications were greater in the CROSS study. Conclusions: In highly selected EC and GEJC pts, definitive nCRT radiation doses do not appear to increase POC rates. Thus, 50 Gy can likely be delivered without increasing toxicity while also achieving a definitive dose for pts not able or willing to undergo subsequent surgery. [Table: see text]

Antibody drug conjugates under investigation in phase I and phase II clinical trials for gastrointestinal cancer

INTRODUCTION

Antibody drug conjugates (ADCs) represent a developing class of anticancer therapeutics which are designed to selectively deliver a cytotoxic payload to tumors, while limiting systemic toxicity to healthy tissues. There are several ADCs which are currently in various stages of clinical development for the treatment of gastrointestinal malignancies.

AREAS COVERED

We discuss the biologic rationale and review the clinical experience with ADCs in the treatment of gastrointestinal malignancies, summarizing the pre-clinical and phase I/II clinical trial data that have been completed or are ongoing.

EXPERT OPINION

While there have been significant advances in the development of ADCs since they were first introduced, several challenges remain. These challenges include (i) the selection of an ideal antigen target which is tumor specific and internalized upon binding, (ii) selection of an antibody which has high affinity for its antigen target and low immunogenicity, (iii) selection of a potent payload which is cytotoxic at sub-nanomolar concentrations, and (iv) optimal design of a linker to confer ADC stability with limited off-site toxicity. Efforts are ongoing to address these issues and innovate the ADC technology to improve the safety and efficacy of these agents.

CDK1 Interacts with Sox2 and Promotes Tumor Initiation in Human Melanoma

: Cancers are composed of heterogeneous subpopulations with various tumor-initiating capacities, yet key stem cell genes associated with enhanced tumor-initiating capacities and their regulatory mechanisms remain elusive. Here, we analyzed patient-derived xenografts from melanoma, colon, and pancreatic cancer tissues and identified enrichment of tumor-initiating cells in MHC class I-hi cells, where CDK1, a master regulator of the cell cycle, was upregulated. Overexpression of CDK1, but not its kinase-dead variant, in melanoma cells increased their spheroid forming ability, tumorigenic potential, and tumor-initiating capacity; inhibition of CDK1 with pharmacologic agents reduced these characteristics, which was unexplained by the role of CDK1 in regulating the cell cycle. Proteomic analysis revealed an interaction between CDK1 and the pluripotent stem cell transcription factor Sox2. Blockade or knockdown of CDK1 resulted in reduced phosphorylation, nuclear localization, and transcriptional activity of Sox2. Knockout of Sox2 in CDK1-overexpressing cells reduced CDK1-driven tumor-initiating capacity substantially. Furthermore, GSEA analysis of CDK1^hi tumor cells identified a pathway signature common in all three cancer types, including E2F, G2M, MYC, and spermatogenesis, confirming a stem-like nature of CDK1^hi tumor cells. These findings reveal a previously unrecognized role for CDK1 in regulating tumor-initiating capacity in melanoma and suggest a novel treatment strategy in cancer via interruption of CDK1 function and its protein-protein interactions. SIGNIFICANCE: These findings uncover CDK1 as a new regulator of Sox2 during tumor initiation and implicate the CDK1-Sox2 interaction as a potential therapeutic target in cancer.

Phase Ib Results of the Rational Combination of Selumetinib and Cyclosporin A in Advanced Solid Tumors with an Expansion Cohort in Metastatic Colorectal Cancer

MEK inhibition is of interest in cancer drug development, but clinical activity in metastatic colorectal cancer (mCRC) has been limited. Preclinical studies demonstrated Wnt pathway overexpression in KRAS-mutant cell lines resistant to the MEK inhibitor, selumetinib. The combination of selumetinib and cyclosporin A, a noncanonical Wnt pathway modulator, demonstrated antitumor activity in mCRC patient-derived xenografts. To translate these results, we conducted a NCI Cancer Therapy Evaluation Program-approved multicenter phase I/IB trial (NCT02188264) of the combination of selumetinib and cyclosporin A. Patients with advanced solid malignancies were treated with the combination of oral selumetinib and cyclosporin A in the dose escalation phase, followed by an expansion cohort of irinotecan and oxaliplatin-refractory mCRC. The expansion cohort utilized a single-agent selumetinib "run-in" to evaluate FZD2 biomarker upregulation and KRAS-WT and KRAS-MT stratification to identify any potential predictors of efficacy. Twenty and 19 patients were enrolled in dose escalation and expansion phases, respectively. The most common adverse events and grade 3/4 toxicities were rash, hypertension, and edema. Three dose-limiting toxicities (grade 3 hypertension, rash, and increased creatinine) were reported. The MTD was selumetinib 75 mg twice daily and cyclosporin A 2 mg/kg twice daily on a 28-day cycle. KRAS stratification did not identify any differences in response between KRAS-WT and KRAS-MT cancers. Two partial responses, 18 stable disease, and 10 progressive disease responses were observed. Combination selumetinib and cyclosporin A is well tolerated, with evidence of activity in mCRC. Future strategies for concept development include identifying better predictors of efficacy and improved Wnt pathway modulation.Significance: These findings translate preclinical studies combining selumetinib and cyclosporin into a phase I first-in-human clinical trial of such a combination in patients with advanced solid malignancies. Cancer Res; 78(18); 5398-407. ©2018 AACR.

A Phase I Dose-Escalation Study of Linsitinib (OSI-906), a Small-Molecule Dual Insulin-Like Growth Factor-1 Receptor/Insulin Receptor Kinase Inhibitor, in Combination with Irinotecan in Patients with Advanced Cancer

Lessons Learned.

The maximum tolerated dose of the combination of linsitinib and irinotecan is linsitinib 450 mg daily on days 1–3 every 7 days and irinotecan 125 mg/m² days 1 and 8 of a 21‐day cycle.

The adverse effects associated with the combination are not significantly increased beyond what is expected of each drug as a single agent.

Multiple negative trials of insulin‐like growth factor‐1 receptor inhibitors performed in unselected patient populations led to the early discontinuation of linistinib development and this trial.

Earlier integration of assessment of potential predictive biomarkers into clinical trials, as was planned in this study, is vital to the development of targeted therapies in oncology.

Background.

This phase I dose‐escalation study was designed to evaluate the safety and tolerability of the combination of irinotecan and insulin‐like growth factor‐1 receptor (IGF‐1R) inhibitor linsitinib in patients with advanced cancer refractory to standard therapy.

Methods.

Dose escalation in three specified dose levels was performed according to a standard 3 + 3 design. Dose levels were as follows: (a) linsitinib 400 mg and irinotecan 100 mg/m², (b) linsitinib 450 mg and irinotecan 100 mg/m², and (c) linsitinib 450 mg and irinotecan 125 mg/m². Linisitinib was administered once daily on days 1–3, 8–10, and 15–17, and irinotecan on days 1 and 8. Assessment of a candidate predictive biomarker was planned in all patients, with further evaluation in an expansion cohort of advanced colorectal cancer.

Results.

A total of 17 patients were treated, with 1 patient in both cohort 2 and 3 experiencing dose‐limiting toxicity. Linsitinib 450 mg and irinotecan 125 mg/m² was the maximum tolerated dose. Sixteen (94%) patients experienced at least one treatment‐related adverse event. Neutropenia was the only grade >3 toxicity (4%). No significant hyperglycemia or QT interval prolongation was noted. No objective responses were observed; 47% (n = 8) had stable disease with median duration of 5.25 months.

Conclusion.

Although the combination was determined safe, the study was halted due to termination of linsitinib development, and biomarker testing was not performed.

Cabozantinib Exhibits Potent Antitumor Activity in Colorectal Cancer Patient-Derived Tumor Xenograft Models via Autophagy and Signaling Mechanisms

Antiangiogenic therapy used in treatment of metastatic colorectal cancer (mCRC) inevitably succumbs to treatment resistance. Upregulation of MET may play an essential role to acquired anti-VEGF resistance. We previously reported that cabozantinib (XL184), an inhibitor of receptor tyrosine kinases (RTK) including MET, AXL, and VEGFR2, had potent antitumor effects in mCRC patient-derived tumor explant models. In this study, we examined the mechanisms of cabozantinib sensitivity, using regorafenib as a control. The tumor growth inhibition index (TGII) was used to compare treatment effects of cabozantinib 30 mg/kg daily versus regorafenib 10 mg/kg daily for a maximum of 28 days in 10 PDX mouse models. In vivo angiogenesis and glucose uptake were assessed using dynamic contrast-enhanced (DCE)-MRI and [¹⁸F]-FDG-PET imaging, respectively. RNA-Seq, RTK assay, and immunoblotting analysis were used to evaluate gene pathway regulation in vivo and in vitro Analysis of TGII demonstrated significant antitumor effects with cabozantinib compared with regorafenib (average TGII 3.202 vs. 48.48, respectively; P = 0.007). Cabozantinib significantly reduced vascularity and glucose uptake compared with baseline. Gene pathway analysis showed that cabozantinib significantly decreased protein activity involved in glycolysis and upregulated proteins involved in autophagy compared with control, whereas regorafenib did not. The combination of two separate antiautophagy agents, SBI-0206965 and chloroquine, plus cabozantinib increased apoptosis in vitro Cabozantinib demonstrated significant antitumor activity, reduction in tumor vascularity, increased autophagy, and altered cell metabolism compared with regorafenib. Our findings support further evaluation of cabozantinib and combinational approaches targeting autophagy in colorectal cancer. Mol Cancer Ther; 17(10); 2112-22. ©2018 AACR.

Abstract 277: Gaining insights into pancreatic cancer intervention with bitter melon, a natural agent, in combination with gemcitabine using patient derived xenografts

Pancreatic cancer (PanC) remains the 4th leading cause of cancer related-deaths in U.S. resulting in a dismal survival rate of &lt;5%. This generates a critical need for identifying novel non-toxic agents aimed at effective PanC management with minimal patient distress. Bitter melon (Momordica charantia), a dietary agent, is actively being examined for its anti-cancer efficacy against a panel of malignancies. Recent data from our group highlights the anti-PanC potential of bitter melon juice (BMJ); its role in PanC-cancer stem cell (CSC) self-renewal/ kinetics and gemcitabine (GEM) resistance in PanC cells. GEM is the standard of care drug used in PanC therapeutics but there has been a continual increase in GEM resistant PanC patients lately. In our current study, we determined the nature of combinations for BMJ (0.5- 2% v/v) and GEM (2- 25 μM) in vitro using 3 human PanC cell lines. Combination indices (CI) determined using Chou-Talalay method for BMJ and GEM were: PANC1 (no observed interaction), AsPC1 (CI=0.5-1, leaning towards synergism) and BxPC3 (CI=0.1-0.8, synergistic). Patient-derived xenografts (PDX) are gaining importance as representatives of the genomic complexities and interactions with tumor microenvironment like primary patient tumors, thereby contributing to accelerated therapeutic approaches. Subsequently, we focused on assessing the efficacy of BMJ alone, or in addition to GEM using the PanC-PDX mouse model. Treatment regimen had 4 cohorts: Controls (untreated); BMJ alone- 200mg/Kg; GEM alone- 50mg/Kg; and Combo (BMJ+GEM). BMJ efficacy was examined in 3 human PanC-PDX explants in nude mice, denoted by PanC-PDX 272, 266 and 271, alongside GEM, and Combo. Tumor volumes recorded post first part of study (~day 35; first sacrifice time-point) showed significant tumor growth inhibition in all treated groups. GEM and Combo displayed comparable efficacies by decrease in tumor volume (~70-80% decrease), followed by BMJ (~50-60% decrease). Interestingly, tumor regrowth determination with subsequent treatment washout period (~30 days), showed maximum tumor regrowth in GEM-treated mice, nearing the untreated controls. BMJ consistently showed a prolonged effect by containment of tumors until the study end (~day 64; second sacrifice time-point). Combo tumors remained close to BMJ, suggesting no apparent antagonistic interference. Notably, at study completion (day 64), BMJ or Combo displayed the most significant and sustained effect on tumor volumes (~60-80% decrease for BMJ, 80-90% decrease for Combo) compared to GEM (~40-50% decrease), after treatments were stopped. Together, these results point to the chemopreventive efficacy of BMJ as a monotherapeutic as well a perfect combinatorial candidate in studies with chemotherapeutic agents like GEM aimed at PanC management utilizing the resourceful PanC-PDX mouse model.

Citation Format: Deepanshi Dhar, Dileep Kumar, Stacey Bagby, Todd M. Pitts, Wells A. Messersmith, Komal Raina, Rajesh Agarwal. Gaining insights into pancreatic cancer intervention with bitter melon, a natural agent, in combination with gemcitabine using patient derived xenografts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 277.

Antitumor activity of the aurora a selective kinase inhibitor, alisertib, against preclinical models of colorectal cancer

Background

The Aurora kinases are a family of serine/threonine kinases comprised of Aurora A, B, and C which execute critical steps in mitotic and meiotic progression. Alisertib (MLN8237) is an investigational Aurora A selective inhibitor that has demonstrated activity against a wide variety of tumor types in vitro and in vivo, including CRC.

Results

CRC cell lines demonstrated varying sensitivity to alisertib with IC₅₀ values ranging from 0.06 to > 5 umol/L. Following exposure to alisertib we observed a decrease in pAurora A, B and C in four CRC cell lines. We also observed an increase in p53 and p21 in a sensitive p53 wildtype cell line in contrast to the p53 mutant cell line or the resistant cell lines. The addition of alisertib to standard CRC treatments demonstrated improvement over single agent arms; however, the benefit was largely less than additive, but not antagonistic.

Methods

Forty-seven CRC cell lines were exposed to alisertib and IC₅₀s were calculated. Twenty-one PDX models were treated with alisertib and the Tumor Growth Inhibition Index was assessed. Additionally, 5 KRAS wildtype and mutant PDX models were treated with alisertib as single agent or in combination with cetuximab or irinotecan, respectively.

Conclusion

Alisertib demonstrated anti-proliferative effects against CRC cell lines and PDX models. Our data suggest that the addition of alisertib to standard therapies in colorectal cancer if pursued clinically, will require further investigation of patient selection strategies and these combinations may facilitate future clinical studies.

Antitumor activity of the polo-like kinase inhibitor, TAK-960, against preclinical models of colorectal cancer

BACKGROUND

Polo-like kinase 1 (Plk1) is a serine/threonine kinase that is a key regulator of multiple stages of mitotic progression. Plk1 is upregulated in many tumor types including colorectal cancer (CRC) and portends a poor prognosis. TAK-960 is an ATP-competitive Plk1 inhibitor that has demonstrated efficacy across a broad range of cancer cell lines, including CRC. In this study, we investigated the activity of TAK-960 against a large collection of CRC models including 55 cell lines and 18 patient-derived xenografts.

METHODS

Fifty-five CRC cell lines and 18 PDX models were exposed to TAK-960 and evaluated for proliferation (IC50) and Tumor Growth Inhibition Index, respectively. Additionally, 2 KRAS wild type and 2 KRAS mutant PDX models were treated with TAK-960 as single agent or in combination with cetuximab or irinotecan. TAK-960 mechanism of action was elucidated through immunoblotting and cell cycle analysis.

RESULTS

CRC cell lines demonstrated a variable anti-proliferative response to TAK-960 with IC50 values ranging from 0.001 to > 0.75 μmol/L. Anti-proliferative effects were sustained after removal of drug. Following TAK-960 treatment a highly variable accumulation of mitotic (indicating cell cycle arrest) and apoptotic markers was observed. Cell cycle analysis demonstrated that TAK-960 treatment induced G2/M arrest and polyploidy. Six out of the eighteen PDX models responded to single agent TAK-960 therapy (TGII< 20). The addition of TAK-960 to standard of care chemotherapy resulted in largely additive antitumor effects.

CONCLUSION

TAK-960 is an active anti-proliferative agent against CRC cell lines and PDX models. Collectively, these data suggest that TAK-960 may be of therapeutic benefit alone or in combination with other agents, although future work should focus on the development of predictive biomarkers and hypothesis-driven rational combinations.

A retrospective review of borderline resectable-locally advanced pancreatic adenocarcinoma (BR-LAPC) undergoing neoadjuvant chemotherapy followed by stereotactic body radiation therapy (SBRT) at the University of Colorado Cancer Center

436

Background: Metastatic pancreatic chemotherapy regimens are often used as neoadjuvant treatment in the LAPC setting. The University of Colorado has a treatment paradigm for BR-LAPC which consists of 2-4 months of chemotherapy followed by SBRT then reevaluated for surgical resection. Methods: Retrospective analysis of patients with pathologically confirmed BR-LAPC who received all neoadjuvant treatment (chemotherapy and SBRT) with intention of undergoing surgical resection at the University of Colorado Cancer Center from 2012 to 2017. Baseline data collected includes demographics, comorbidities, disease characteristics and chemotherapy regimen FOLFIRINOX or Gemcitabine/Nab-Paclitaxel (GNP). The objective of the study is to describe the correlation of neoadjuvant regimens and clinical outcomes. Results: A total of 100 patients were identified with 40 patients collected for the interim analysis. Of these patients 82.5% (N = 33) received FOLFIRINOX and 17.5% (N = 7) received GNP. Patients who received FOLFIRINOX, 78.8% went for surgical resection compared to 85.7% in the GNP group. The number of patients who had a reported College of American Pathology (CAP) grade ≤1, representing no or minimal residual disease, was 3 for the FOLFIRINOX group and no patients in the GNP group. The percent of patients in the FOLFIRINOX group who achieved R0 resections was 90% compared to 83% for the GNP group. Mean initial CA 19-9 was 38.5U/ml, 386.7U/ml, and 1799.8U/ml in CAP grade 1, 2, 3 respectively, while percent reduction in CA 19-9 level during neoadjuvant was 33.3%, 69.7%, and 72.4% respectively. Assessment of the impact of relative dose intensity for each neoadjuvant regimen on clinical outcomes is ongoing. Conclusions: FOLFIRINOX neoadjuvant treatment was associated with improved surgical outcomes including an increased rate of R0 and CAP grade ≤1 resections. Low initial CA 19-9 levels were associated with favorable surgical and pathologic outcomes whereas absolute or relative CA 19-9 reductions with neoadjuvant were not. Final analysis of all 100 patients will be reported.

Clinical and molecular characteristics of younger versus older patients with colorectal cancer

630

Background: Although overall incidence of colorectal cancer is declining, the incidence for young patients (age < 50) with colon cancer is increasing. Reasons for this rise are unclear. Understanding clinical and molecular differences between younger and older cohorts can help guide both patient education strategies and future research into the mechanisms of this phenomenon. Methods: A retrospective analysis of patients diagnosed with colon cancer between 2008 and 2015 who underwent molecular tumor profiling via next-gen sequencing of 26 commonly mutated genes at the University of Colorado. Data collected by chart review includes demographic, pathologic, treatment course, and outcomes. Age group cutoffs for data analysis were set at < 50, 50-65, and > 65 based on screening guidelines and average age of diagnosis Results: We evaluated a total of 242 patients, stage I (n = 1), stage II (n = 65), stage III (n = 68), stage IV (n = 105). Mean age was 59.5 (range 27 to 89). A higher percentage of younger patients were non-smokers (77% of youngest cohort vs 46% of oldest cohort, p < 0.001) and had a non-significant trend towards male gender (youngest cohort 63.8% male, oldest cohort 43.4% male, p = 0.065). Younger patients had similar body mass index (BMI) compared to older patients (BMI 27 vs 25.7, p = 0.35). Younger patients had higher rates of rectal cancer (42% vs 21%, p = 0.01) and lower rates of proximal/right sided colon cancer (20% vs 46.5%, p = 0.014). Younger patients also had lower rates of MSI-H tumors (8% vs 14%, p = 0.01). Finally, younger patients had significantly lower rates of APC (43.1% vs 69.3%, p = 0.009) and BRAF (3.5% vs 19.7%, p = 0.004) mutations. Conclusions: Younger patients ( < 50 years old) with colorectal cancer had lower rates of tobacco use and no difference in obesity rates compared to older patients. In addition, although APC and BRAF mutations were lower in younger patients, there were no mutations that were more prevalent in the young cohort. Therefore, further research into lifestyle factors (specific diet/exercise patterns) or alternative molecular mechanisms are needed.

Early outcomes in patients with locally advanced rectal cancer following total neoadjuvant therapy

848

Background: The current standard treatment for locally advanced rectal cancer (LARC) is neoadjuvant chemoradiation followed by surgery, and then adjuvant chemotherapy. An alternative approach currently being offered to patients at University of Colorado is total neoadjuvant therapy (TNT), in which patients receive all of their planned treatment, including systemic chemotherapy, preoperatively. Methods: Records of patients from the University of Colorado multidisciplinary colorectal clinic between 2/2015 and 5/2017 were retrospectively reviewed. Treatment plans for included patients involved 8 cycles of preoperative chemotherapy with FOLFOX (5-fluoruracil, oxaliplatin, leucovorin), followed by chemoradiation with concurrent capecitabine, and then resection. Patient data collected includes demographic information, initial staging, chemotherapy and radiation received, adverse effects, surgical outcomes, and clinical and pathological response to treatment. Results: At the time of our analysis, 14 patients have completed TNT and undergone surgical resection, with either abdominoperineal resection or low anterior resection (LAR), at the University of Colorado. Patients ranged in age from 39 to 74 years (mean age 56) with 8 patients (57%) female sex. All 14 patients received 5-fluorouracil with all 8 cycles, though 4 (29%) required omission of oxaliplatin by cycle 8. Toxicities from preoperative treatment were as expected, without significant delays in surgery. Of the 14 patients, 4 (29%) showed a pathologic complete response (grade 0, no residual tumor) on their surgical pathology, with 8 (57%) having either grade 0 or 1 (minimal residual tumor) response. Of the 5 patients who underwent LAR with diverting loop ileostomies, mean time to ostomy reversal was 53.6 days (range 49-61). No patients developed clinically-apparent metastatic disease during preoperative therapy. Conclusions: The use of preoperative chemotherapy in addition to standard chemoradiation for locally advanced rectal cancer is well-tolerated, results in a high rate of pathologic complete response, and allows for early reversal of diverting ileostomies.

A phase 1, dose-escalation study of PF-06664178, an anti-Trop-2/Aur0101 antibody-drug conjugate in patients with advanced or metastatic solid tumors

Purpose and Methods Trop-2 is a glycoprotein over-expressed in many solid tumors but at low levels in normal human tissue, providing a potential therapeutic target. We conducted a phase 1 dose-finding study of PF-06664178, an antibody-drug conjugate that targets Trop-2 for the selective delivery of the cytotoxic payload Aur0101. The primary objective was to determine the maximum tolerated dose and recommended phase 2 dose. Secondary objectives included further characterization of the safety profile, pharmacokinetics and antitumor activity. Eligible patients were enrolled and received multiple escalating doses of PF-06664178 in an open-label and unblinded manner based on a modified continual reassessment method. Results Thirty-one patients with advanced or metastatic solid tumors were treated with escalating doses of PF-06664178 given intravenously every 21 days. Doses explored ranged from 0.15 mg/kg to 4.8 mg/kg. Seven patients experienced at least one dose limiting toxicity (DLT), either neutropenia or rash. Doses of 3.60 mg/kg, 4.2 mg/kg and 4.8 mg/kg were considered intolerable due to DLTs in skin rash, mucosa and neutropenia. Best overall response was stable disease in 11 patients (37.9%). None of the patients had a partial or complete response. Systemic exposure of PF-06664178 increased in a dose-related manner. Serum concentrations of free Aur0101 were substantially lower than those of PF-06664178 and total antibody. No correlation of Trop-2 expression and objective response was observed, although Trop-2 overexpression was not required for study entry. The intermediate dose of 2.4 mg/kg appeared to be the highest tolerated dose, but this was not fully explored as the study was terminated early due to excess toxicity. Conclusion PF-06664178 showed toxicity at high dose levels with modest antitumor activity. Neutropenia, skin rash and mucosal inflammation were dose limiting toxicities. Findings from this study may potentially aid in future antibody drug conjugate design and trials.

Abstract A083: A phase Ib study of the combination of MLN0128 (dual TORC1/2 inhibitor) and MLN8237 (Aurora A inhibitor, alisertib) in patients with advanced solid tumors

Background: MLN0128 is an oral inhibitor of mTOR kinase and mTORC1/2 signaling. Alisertib is an oral inhibitor of Aurora A kinase. Senescence and upregulation of genes in the PI3K/AKT/mTor pathway have been observed in triple-negative breast cancer (TNBC) patient-derived xenograft models treated with alisertib, with greater tumor growth inhibition demonstrated in combination with MLN0128 as compared to each agent alone. An investigator-initiated trial was developed to evaluate the combination of MLN0128 and alisertib in patients with advanced solid tumors, followed by an expansion cohort in metastatic TNBC and other selected cancers. The goals of this ongoing study are to evaluate safety, tolerability, pharmacokinetics (PK) and preliminary efficacy of the combination. Results of dose escalation are presented here. Methods: Patients with advanced solid tumors refractory to standard therapy were treated orally at escalating doses with the combination of MLN0128 daily on a continuous schedule and alisertib twice daily (BID) on days 1-7 of a 21-day cycle. Dose escalation was conducted according to a standard 3+3 design. Key eligibility criteria included HgbA1c &lt;7%, fasting serum glucose &lt;130mg/dL and fasting triglycerides &lt;300mg/dL, normal cardiac function, no condition with potential to cause excessive daytime sleepiness (including chronic hypoxia) and no risk of malabsorption of oral medications. PK assessments were performed at various time points after single-agent and combination dosing. Results: A total of 16 patients with refractory cancers were enrolled in dose escalation. No dose-limiting toxicity (DLT) was observed in dose level 1 (MLN0128 1mg/alisertib 30mg) or dose level 2 (2mg/30mg). At the third dose level (2mg/40mg) 2 of 7 patients experienced a DLT (grade 3 fatigue/confusion and grade 2 GERD/nausea leading to study discontinuation). In an alternate dose level cohort evaluating MLN0128 3mg and alisertib 30mg, 2 of 2 patients experienced a DLT of grade 3 fatigue. The maximum tolerated dose (MTD) of the combination was determined to be MLN0128 2mg daily and alisertib 30mg BID. Most common adverse events (AEs) of any grade included alopecia, diarrhea, fatigue and rash in 19% each and nausea in 31% of patients. Most common Grade 3 AEs included fatigue (19%) and decreased neutrophil count (31%). Dose modification was required in 56% of patients, most often due to neutropenia. Median time on study was 3 cycles (range 1-15) at data cutoff. Best response of stable disease was observed in 5 patients (31%), with prolonged stable disease noted in a patient with ER+/HER2- breast cancer (15 cycles) and a patient with castrate-resistant prostate cancer (10 cycles). PK assessments indicate no significant drug interaction between agents. Cmax was 24.7 (± 13.6) ng/mL for MLN0128 and 1049 (±363) ng/mL for alisertib at combination MTD doses. MLN0128 AUC was 128.2 (±72.7) ng/mLxhr and alisertib AUC0-8 was 6119 (±2331) ng/mlxhr at these doses. Conclusions: MLN0128 2mg daily on a continuous schedule and alisertib 30mg BID days 1-7 of a 21-day cycle is the MTD of the drug combination. An expansion cohort in patients with TNBC and other selected cancers is currently enrolling at this dose. Functional imaging and serial tumor biopsies are being integrated into this cohort to assess the pharmacodynamic interactions of the combination.

Citation Format: S. Lindsey Davis, Elaine T. Lam, Bradley R. Corr, Cindy L. O'Bryant, Ashley Glode, Nichole Adler, Todd M. Pitts, John J. Tentler, Anna Capasso, Kyrie Dailey, Natalie J. Serkova, Colin D. Weekes, Daniel L. Gustafson, Christopher H. Lieu, Wells A. Messersmith, Stephen Leong, S. Gail Eckhardt, Jennifer R. Diamond. A phase Ib study of the combination of MLN0128 (dual TORC1/2 inhibitor) and MLN8237 (Aurora A inhibitor, alisertib) in patients with advanced solid tumors [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A083.

Abstract A012: Humanized patient-derived xenografts (PDXs) recapitulate clinical responses in microsatellite stable (MSS) and unstable (MSI-H) colorectal cancer (CRC)

Introduction: Recent data have demonstrated that patients with MSI-H metastatic CRC are more likely to respond to a PD-1 inhibitor as a single agent compared to patients with MSS CRC. Effective immunotherapy approaches for MSS CRC remain a critical unmet need. There is great interest in investigating immune checkpoint inhibition in combination with novel agents, but preclinical studies have been hampered by current models. To gain a better understanding of immune responses and facilitate preclinical evaluation of combination strategies with immunotherapy, we developed a “hematopoietic” humanized mouse model with the intent of leveraging this model for the development of rational combinations in MSS CRC patients. Methods: BRGS (in house breeding) newborn pups were transplanted with CD34+ cells purified from (HLA unmatched) umbilical cord blood at 48 hours. In order to better understand the immune context of these novel animal models, we selected an MSI-high CRC (MDA-C0999-203) and a MSS (CRC172) humanized PDX model. At 16 weeks, MDA-C0999-203 (MSI-H) and CRC172 (MSS) were implanted on both flanks of humanized mice and nonhumanized controls. When the average tumor size reached ~150-300 mm3, both groups of mice were randomized into vehicle and nivolumab (30mg/kg IP twice weekly) stratified by % chimerism (human CD45+ &gt;45%). At the end of the treatment, a portion of the tumor was immediately fixed in formalin for immunohistochemistry and pharmacodynamic analyses with seven-color multispectral imaging using the Perkin Elmer Vectra- 3 instrument, and compared to a surgical specimen from an untreated patient with an MSI-H tumor. Results: In the MSI-H model we observed tumor growth inhibition in the nivolumab-treated, humanized mice with respect to the humanized vehicle-treated control and the nonhumanized nivolumab-treated group (TGII 3.5% vs 76%). In a separate experiment, an MSS CRC humanized PDX model (CRC172) was treated with nivolumab as described above. Although initial control of tumor growth was observed, this was followed by rapid tumor progression (TGII 138.4%). In addition to flow cytometry, an MSI-H CRC tumor directly from a patient was stained for a variety of immunologic markers and analyzed by Vectra. The tumors contained both CD4- and CD8-positive cells, indicating T-cell infiltration. These data are consistent with what was observed by flow cytometry. Similar results were observed in an MSI-H CRC tumor grown as a xenograft in humanized mice both with and without nivolumab. However, in the MSS CRC PDX model, very few CD4 and CD8 cells were observed in the tumor or in the surrounding stroma. Conclusions: We have successfully established in vivo MSI-H and MSS humanized CRC PDXs. All mice were highly chimeric and the MSI-H model demonstrated high TILs, and responding tumors exhibited IFNγ production, high CD8%, higher effector memory % (HLADR+, CD45RO+), and decreased PD-L1 expression by flow cytometry. Interestingly, we also observed greater numbers of T cells in the lymph nodes of the MSI-H PDX. Moreover, immune infiltrates were observed in the MSI-H PDX compared to the MSS by immunohistochemistry. These data suggest that humanized PDX models may be useful in the development of rational combinations of immunotherapy.

Citation Format: Anna Capasso, Julie Lang, Todd M. Pitts, Christopher H. Lieu, Scott Kopetz, Sarah L. Davis, Kimberly Jordan, Stacey M. Bagby, Wells A. Messersmith, Roberta Pelanda, S. Gail Eckhardt. Humanized patient-derived xenografts (PDXs) recapitulate clinical responses in microsatellite stable (MSS) and unstable (MSI-H) colorectal cancer (CRC) [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A012.

Evaluation of TAK-264, an Antibody-Drug Conjugate in Pancreatic Cancer Cell Lines and Patient-Derived Xenograft Models

BACKGROUND

Antibody-drug conjugates (ADCs) are an emerging technology consisting of an antibody, linker, and toxic agent, which have the potential to offer a targeted therapeutic approach. A novel target recently explored for the treatment of pancreatic cancer is guanylyl cyclase C (GCC). The objective of this study was to determine the anti-tumorigenic activity of TAK-264, an investigational ADC consisting of an antibody targeting GCC linked to a monomethyl auristatin E payload via a peptide linker.

METHODS

The antiproliferative effects of TAK-264 assessed in a panel of eleven pancreatic cancer cell lines. Additionally, ten unique pancreatic ductal adenocarcinoma cancer patient-derived xenograft models were treated with TAK-264 and the efficacy was determined. Baseline levels of GCC were analyzed on PDX models and cell lines. Immunoblotting was performed to evaluate the effects of TAK-264 on downstream effectors.

RESULTS

GCC protein expression was analyzed by immunoblotting in both normal and tumor tissue; marked increase in GCC expression was observed in tumor tissue. The in vitro experiments demonstrated a range of responses to TAK-264. Eight of the ten PDAC PDX models treated with TAK-264 demonstrated a statistically significant tumor growth inhibition. Immunoblotting demonstrated an increase in phosphorylated-HistoneH3 in both responsive and less responsive cell lines and PDAC PDX models treated with TAK-264. There was no correlation between baseline levels of GCC and response in either PDX or cell line models.

CONCLUSION

TAK-264 has shown suppression activity in pancreatic cancer cell lines and in pancreatic PDX models. These findings support further investigation of ADC targeting GCC.

Abstract B050: Evaluation of TAK-264, a novel antibody-drug conjugate in pancreatic cancer cell lines and patient-derived xenograft models

Background: Antibody-drug conjugates (ADCs) are an emerging technology consisting of antibody, linker, and toxic agent, which have the potential to offer a more targeted therapeutic approach than standard chemotherapy regimens. ADCs selectively bind to antigens expressed in tumor environments. An emerging target for the treatment of pancreatic cancer is guanylyl cyclase C (GCC). GCC is a transmembrane G protein receptor found on the apical surface of intestinal enterocytes. It plays an important role in GI homeostasis. GCC is highly expressed in various colorectal carcinomas as well as adenocarcinomas of the upper GI tract. The objective of this study was to determine the antitumorigenic activity of TAK-264, an investigational ADC that targets GCC. Experimental Procedures: The antiproliferative effects of TAK-264 were assessed in a panel of eleven pancreatic cancer cell lines with various molecular backgrounds. Additionally, ten unique pancreatic ductal adenocarcinoma (PDAC) cancer patient-derived xenograft (PDX) models were treated with TAK-264 and the efficacy was determined. Tumor size was evaluated twice per week by caliper measurements. Sensitivity to TAK-264 was defined based on tumor growth inhibition that was statistically significant when compared to the vehicle control. Baseline levels of GCC were analyzed by IHC/immunoblotting and RT-PCR on PDX models and cell lines. Immunoblotting was performed to evaluate the effects of TAK-264 on downstream effectors. Results: GCC protein expression was analyzed by immunoblotting in normal versus tumor tissue; a marked increase in GCC expression was observed in tumor tissue when compared to matching normal tissue. The in vitro experiments demonstrated a range of responses to TAK-264 in an SRB assay. Eight of the ten PDAC PDX models demonstrated a statistically significant tumor growth inhibition when compared to the vehicle control. Immunoblotting demonstrated an increase in phosphorylated-Histone-H3 in two cell lines and in the PDAC PDX models treated with TAK-264, indicating a DNA damage response. The analysis of GCC protein expression in normal versus tumor tissue has shown a marked increase in GCC expression in tumor tissue when compared to matching normal tissue. There was no correlation between baseline levels of GCC and response to TAK-264 in either PDX or cell line models. Conclusions: TAK-264, an ADC targeting GCC, has good growth suppression activity in pancreatic cancer cell lines and in pancreatic PDX models. These findings support a hypothesis that further investigation of ADC targeting GCC may lead to novel therapeutic modalities for pancreatic cancer.

Citation Format: Anna R. Schreiber, Anna Nguyen, Stacey M. Bagby, Betelehem Yacob, Kevin Quackenbush, Joe L. Guy, Thomas Crowell, Bradley Stringer, Hadi Danaee, Thea Kalebic, Wells A. Messersmith, John J. Arcaroli, Todd M. Pitts. Evaluation of TAK-264, a novel antibody-drug conjugate in pancreatic cancer cell lines and patient-derived xenograft models [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B050.

The novel ATM inhibitor (AZ31) enhances antitumor activity in patient derived xenografts that are resistant to irinotecan monotherapy

Irinotecan, a standard of care therapy for CRC, elicits cytotoxic effects by generating double strand breaks resulting in DNA damage. The activation of the ATM pathway plays a fundamental role in regulating the cellular response and repair to DNA damage. The objective of this preclinical study was to determine whether ATM inhibition would enhance sensitivity to irinotecan treatment. Treatment effects of AZ31, irinotecan or AZ31 + irinotecan were investigated in CRC cell lines and CRC patient derived xenografts. Activation of ATM and downstream targets p-RAD50 and p-H2AX were evaluated by immunohistochemistry. Combinational effects were demonstrated in 4 out of 8 CRC explants. Interestingly, each of the combinational sensitive CRC PDX models were shown to be more resistant to irinotecan single agent therapy. Treatment with irinotecan significantly elevated the ATM pathway evident by an increase in the activation of H2AX and RAD50. Combinational therapy reduced the activation of H2AX and RAD50 when compared to irinotecan alone in the combination sensitive CRC098. AZ31 + irinotecan was effective at reducing tumor growth in tumors that exhibited resistance to irinotecan in our CRC PDX model. These findings support further investigation of this combinational therapy for the treatment of CRC patients.