Clinical outcomes of liposomal irinotecan in advanced pancreatic adenocarcinoma patients previously treated with conventional irinotecan-based chemotherapy: a real-world study

Background

The efficacy of combination chemotherapy beyond the first-line setting remains modest in patients with advanced pancreatic adenocarcinoma (PAC). Evidence from recent clinical studies has shown that liposomal irinotecan (nal-IRI) plus 5-fluorouracil (5-FU) and leucovorin (LV) resulted in survival benefits in patients with advanced pancreatic adenocarcinoma (APAC) after progression on gemcitabine-based treatment. However, the survival benefits of nal-IRI in the third and later lines, in which limited options are available, have yet to be extensively studied. Also, some studies have shown conflicting results regarding the impact of prior treatment with conventional IRI on patient outcomes following treatment with nal-IRI. Therefore, this real-world study aimed to evaluate the efficacy and safety of nal-IRI plus 5FU-LV in advanced PAC patients who progressed on conventional IRI-containing regimens.

Methods

A retrospective chart review was conducted between November 2016 to December 2022 on 30 patients diagnosed with advanced PAC who completed at least one cycle of nal-IRI plus 5-FU- LV and were previously treated with conventional IRI. Data regarding survival outcomes were retrieved.

Results

Thirty patients met the inclusion criteria. Overall, 76.7% of the patients received at least two lines of therapy prior to nal-IRI. The median overall duration of nal-IRI treatment was 2.0 months (IQR: 1.3 - 3.9 months). One patient (3.3%) had a partial response, and seven patients (23.3%) had stable disease as their best response. The median progression-free survival (PFS) was 1.9 months (95% CI 1.6 - 2.0) and the 6-month PFS rate was 20.0%. The median overall survival (OS) was 5.0 months (95% CI 3.4 - 7.0), and the 6-month OS rate was 36.7%. An interval between conventional IRI and nal-IRI ≥5.5 months was significantly associated with prolonged OS of 10.2 months (95% CI 3.3 - 12.1) versus 4.3 months (95% CI 2.1 - 5.9; p =0.003). Ten patients (33.3%) experienced grade 3 adverse events, most commonly nausea, fatigue, diarrhea, and non-neutropenic fever.

Conclusion

Nal-IRI plus 5FU/LV had modest survival benefits and an acceptable safety profile in patients with prior conventional IRI. A longer interval between conventional IRI and nal-IRI was associated with increased survival outcomes.

RAD51B Harbors Germline Mutations Associated With Pancreatic Ductal Adenocarcinoma

PURPOSE

Genetic alterations in many components of the homologous recombination, DNA damage response, and repair (HR-DDR) pathway are involved in the hereditary cancer syndromes, including familial pancreatic cancer. HR-DDR genes beyond BRCA1, BRCA2, ATM, and PALB2 may also mutate and confer the HR-DDR deficiency in pancreatic ductal adenocarcinoma (PDAC).

METHODS

We conducted a study to examine the genetic alterations using a companion diagnostic 15-gene HR-DDR panel in PDACs. HR-DDR gene mutations were identified and characterized by whole-exome sequencing and whole-genome sequencing. Different HR-DDR gene mutations are associated with variable homologous recombination deficiency (HRD) scores.

RESULTS

Eight of 50 PDACs with at least one HR-DDR gene mutation were identified. One tumor with BRCA2 mutations is associated with a high HRD score. However, another tumor with a CHEK2 mutation is associated with a zero HRD score. Notably, four of eight PDACs in this study harbor a RAD51B gene mutation. All four RAD51B gene mutations were germline mutations. However, currently, RAD51B is not the gene panel for germline tests.

CONCLUSION

The finding in this study thus supports including RAD51B in the germline test of HR-DDR pathway genes.

Gemcitabine/nab-paclitaxel with pamrevlumab: a novel drug combination and trial design for the treatment of locally advanced pancreatic cancer

Purpose

Pancreatic ductal adenocarcinomas exhibit a high degree of desmoplasia due to extensive extracellular matrix deposition. Encasement of mesenteric vessels by stroma in locally advanced pancreatic cancer (LAPC) prevents surgical resection. This study sought to determine if the addition of a monoclonal antibody to connective tissue growth factor, pamrevlumab, to neoadjuvant chemotherapy would be safe and lead to improved resectability in this surgically adverse patient population.

Methods

In this phase I/II trial, 37 patients with LAPC were randomised 2:1 to gemcitabine/nab-paclitaxel plus (Arm A, n=24) or minus (Arm B, n=13) pamrevlumab. Those who completed six cycles of treatment were assessed for surgical eligibility by protocol-defined criteria. Resection rates, progression-free and overall survival were evaluated.

Results

Eighteen (75%) patients in Arm A and seven (54%) in Arm B completed six cycles of therapy with similar toxicity patterns. In Arms A and B, carbohydrate antigen 19–9 response, as defined by ≥50% decline from baseline, occurred in 13 (65%) and 5 (42%), respectively. Sixteen (16%) per cent of patients were radiographically downstaged by National Comprehensive Cancer Network criteria (5 in Arm A (21%) and 1 (8%) in Arm B). Positron emission tomography normalised in 9 (38%) vs 3 (23%) of patients in Arm A vs Arm B, respectively, and correlated with surgical exploration. Eligibility for surgical exploration was 17 (71%) vs 2 (15%) (p=0.0019) and resection was achieved in 8 (33%) vs 1 (8%) of patients in Arm A vs Arm B (p=0.1193), respectively. Postoperative complication rates were not different between arms.

Conclusions

Neoadjuvant chemotherapy with pamrevlumab holds promise for enhancing resection rates in patients with LAPC without added toxicity. This combination merits evaluation in a larger patient cohort.

Abstract 546: PARG and WEE1 inhibition in GI cancers: A novel synergistic, targeted therapeutic approach

Colorectal carcinomas (CRC) and pancreatic ductal adenocarcinomas (PDAC) are the 2nd and 3rd leading causes of cancer-related deaths in the U.S. respectively. Recent work from our lab highlighted Poly ADP-Ribose Glycohydrolase (PARG) as a target in PDAC, and PARG inhibition (PARGi) sensitized PDAC cells to the DNA damaging agents, 5-FU and oxaliplatin. Other labs have shown that PARG inhibition causes replication stress in cancer cells. CRC and PDAC cells, while cellularly different, share a high frequency of KRAS and P53 inactivating mutations. High levels of replication stress (RS) has also been well documented in these tumor types. Targeting DNA Damage Response Kinases (DDRKs) in combination with chemotherapy (mostly DNA damage inducers like 5-FU, oxaliplatin, etc.) has gained recent interest in solid tumors but overlapping toxicities and tolerability have been issues clinically. Accordingly, we hypothesized that combined inhibition of PARG and DDRKs could yield synergistic effects in tumors with high replication stress while alleviating adverse events seen in other combination strategies. We determined in drug sensitivity assays that PARGi did not synergize with either the CHK1 inhibitor prexasertib or the ATR inhibitor VE-821 in our cell lines but did synergize with Wee1i (AZD1775) in both PDAC and CRC cell lines (Comb. Analysis, p<.05). Additionally, we assessed long-term cell survival using colony formation assays, which yielded a dramatic reduction in cell survival for Panc1, MiaPaCa-2, CFPAC1 (PDAC cells), HCT116 (CRC cells) and SW480 (CRC cells) cell lines with the combination of PARGi and Wee1i as compared to single-agent controls (p<.001). To validate the targeted synergy between AZD1775 and PARGi, we utilized genetic models of PARG and Wee1 silencing, including CRISPR PARG knockout cell lines, siRNA, and shRNA knockdown models. Genetic knockdown of Wee1 and PARG in PDAC and CRC cell lines yielded strikingly similar results in colony formation assays, with 2 and 12-fold changes respectively compared to Wee1i alone (P-value < .0001). HCT116 CRISPR PARG knockouts yielded a 5-fold difference in Wee1i sensitivity in colony formation assays. Mechanistically, western blot analysis demonstrated PARGi and Wee1i led to >2-fold increases in PARylation, yH2AX, and cleaved-caspase 3 as compared to single-agent controls. In conclusion, combined PARG - Wee1 inhibition is a novel targeting strategy in PDAC and CRC tumors that results in decreased cell viability. We are currently testing the efficacy of AZD1775 in PARG CRISPR-knockout tumors in in vivo xenograft models. Ongoing studies are focused on assessing the effect of Wee1i + PARGi on chromosomal aberrations, disruption in replication fork dynamics via DNA fiber labeling, and cell cycle dependencies.

Citation Format: Lebaron C. Agostini, Aditi Jain, Michael Pishvaian, Charles Yeo, Jonathan Brody. PARG and WEE1 inhibition in GI cancers: A novel synergistic, targeted therapeutic approach [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 546.

Treatment patterns and outcomes in pancreatic cancer: Retrospective claims analysis

Background

Pancreatic cancer represents the third leading cause of US cancer deaths, with median survival <1 year. The goal of this study was to describe systemic treatments, healthcare utilization and costs, and overall survival among patients with unresectable/metastatic disease.

Methods

This study used healthcare claims for commercial and Medicare Advantage enrollees diagnosed with pancreatic adenocarcinoma (at index date) during January 01 2010 to 31 May 2017. Included patients were aged ≥18 years, with continuous 6‐month preindex enrollment. Patients were excluded by resectable disease, another primary cancer, or pregnancy. Cohorts were based on first‐line (LOT1) chemotherapy regimen.

Results

Overall, 12 978 patients (mean age 70 years, 51% male) were included, among which 5610 (43%) received chemotherapy. Of those, 23% received gemcitabine monotherapy, 22% gemcitabine‐nab paclitaxel, 22% FOLFIRINOX, 3% FOLFOX, and 29% received other regimens. Mean LOT1 duration was 112 days; 60% did not undergo subsequent lines of therapy. Moreover, 50% of patients had an emergency room visit and 45% were hospitalized during LOT1. Among treated and untreated patients, mean total 6‐month costs were $52 101. We found that patients receiving FOLFIRINOX had the highest costs, whereas those who received gemcitabine monotherapy had the lowest. Median overall survival (mOS) was 335 days with any first‐line treatment. FOLFIRINOX‐treated patients had the highest mOS (492 days), whereas gemcitabine monotherapy‐treated patients had the lowest (223 days).

Conclusions

A large proportion (57%) of patients with unresectable/metastatic pancreatic cancer did not receive chemotherapy. Healthcare costs were higher for fluorouracil‐based regimens, while lower for gemcitabine‐based regimens. Survival rates were within expectations for advanced pancreatic cancer.

Abstract OT2-03-04: A trial of induction Talazoparib followed by a combination of Talazoparib and Avelumab in advanced breast cancer: The TALAVE study

Background: Patients with advanced breast cancer (ABC) have recently gained access to promising new therapies, including PARP inhibitors (PARPi) and immunotherapy. However, not all patients benefit from these approaches, with response rates highest in patients characterized by a particular biomarker (ie BRCA1/2 mutation or PD-L1 expression). Combination strategies may be more efficacious than single agents and may induce responses in otherwise non-responders. PARPi activate the STING pathway leading to T cell recruitment and stimulate antigen presentation via increased T cell cytotoxic activity, creating a tumor microenvironment that may be more susceptible to immunotherapy. A number of trials have assessed the antitumor efficacy of this combination, though the optimal drug scheduling and the impact of BRCA1/2 status on the effect of PARP inhibition on immunomodulation are unknown. In the TALAVE study, the PARPi talazoparib is combined with the PD-L1 inhibitor avelumab. Talazoparib is an oral small molecule selective inhibitor of PARP-1/2 with potent in vitro PARP trapping capacity. Avelumab is a human IgG1 anti-PD-L1 monoclonal antibody that prevents the interaction between PD-L1 and PD-1 and allows for an engagement of Fc-γ receptors on NK cells to induce tumor-directed ADCC in vitro.

Trial design: This is an open-label, multi-institutional trial (NCT03964532) for patients with ABC. During the phase I portion, 6 patients are enrolled regardless of BRCA1/2 mutation status to assess safety of the combination. A maximum of 24 patients will be enrolled. Eligibility criteria include willingness to undergo serial biopsies and no previous exposure to PARPi or prior disease progression on anti-PD1 or anti-PDL1 therapy or within 6 months of use. Patients will be enrolled to two pre-defined cohorts: cohort 1 - BRCA1/2 mutant and HER2 negative ABC (pre-identified presence of somatic or germline BRCA1/2 deleterious mutation) and cohort 2 - BRCA1/2 wild type and TNBC (patients with previous somatic or germline testing for BRCA1/2 that did not reveal a deleterious mutation). Enrolled patients will receive a 4-week induction of talazoparib (1mg orally daily, D1-D28), followed by a combination of talazoparib and avelumab (800mg IV D1 and D15). To assess the efficacy and immunomodulatory effects of PARP inhibition induction followed by anti-PD-L1 therapy, patients will undergo serial tumor biopsies (baseline, post 4 weeks of talazoparib, post 4 weeks of talazoparib and avelumab and at progression for patients who clearly benefitted from therapy) to assess tumor infiltrating lymphocytes (TILs) and PD-L1 expression. Patients will also undergo serial blood sample collection to gauge the peripheral immunoscore by flow cytometry, including an assessment of the number of immune cells and their function.

Specific aims: The primary objective is to evaluate the safety and tolerability of this combination. Secondary objectives includeassessment of anti-tumor efficacy of combined therapy as determined by measurement of ORR, OS, PFS, DOR and DCR and evaluation of the effect of BRCA1/2 mutation, talazoparib alone, and talazoparib plus avelumab on immunomodulation.

Statistical methods: The projected sample size is 24 patients. Sample size is based on a feasibility analysis. Statistics will be primarily descriptive, and toxicities will be tabulated according to grade. PFS and OS will be estimated using the Kaplan Meier method. DCR and DOR will be calculated according to RECIST v1.1 and compared descriptively to historical outcomes. Cox regression models will assess whether measures of immune activation are associated with ORR, PFS or OS.

Accrual: Patient accrual started in April 2019. To date, 3 of the maximum target accrual of 24 patients have been enrolled in the phase I portion of the study (2 on cohort 1 and 1 on cohort 2).

Citation Format: Arielle L Heeke, Michael Pishvaian, Hongkun Wang, Adam Cohen, Jeffrey Schlom, Renee Donahue, Caroline Jochems, Margaret Gatti-Mays, Paula Pohlmann, Antoinette Tan, Claudine Isaacs, Filipa Lynce. A trial of induction Talazoparib followed by a combination of Talazoparib and Avelumab in advanced breast cancer: The TALAVE study [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr OT2-03-04.

The Sustained Induction of c-MYC Drives Nab-Paclitaxel Resistance in Primary Pancreatic Ductal Carcinoma Cells

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive disease with limited and, very often, ineffective medical and surgical therapeutic options. The treatment of patients with advanced unresectable PDAC is restricted to systemic chemotherapy, a therapeutic intervention to which most eventually develop resistance. Recently, nab-paclitaxel (n-PTX) has been added to the arsenal of first-line therapies, and the combination of gemcitabine and n-PTX has modestly prolonged median overall survival. However, patients almost invariably succumb to the disease, and little is known about the mechanisms underlying n-PTX resistance. Using the conditionally reprogrammed (CR) cell approach, we established and verified continuously growing cell cultures from treatment-naïve patients with PDAC. To study the mechanisms of primary drug resistance, nab-paclitaxel-resistant (n-PTX-R) cells were generated from primary cultures and drug resistance was verified in vivo, both in zebrafish and in athymic nude mouse xenograft models. Molecular analyses identified the sustained induction of c-MYC in the n-PTX-R cells. Depletion of c-MYC restored n-PTX sensitivity, as did treatment with either the MEK inhibitor, trametinib, or a small-molecule activator of protein phosphatase 2a. IMPLICATIONS: The strategies we have devised, including the patient-derived primary cells and the unique, drug-resistant isogenic cells, are rapid and easily applied in vitro and in vivo platforms to better understand the mechanisms of drug resistance and for defining effective therapeutic options on a patient by patient basis.

Abstract 4764: A global transcriptome analysis of pancreatic cancer cells distinguishes between acute and acquired PARP inhibitor resistance mechanisms

Pancreatic ductal adenocarcinoma (PDAC) is the 3rd leading cause of cancer related deaths in the U.S. Recent advances in understanding RNA biology in PDAC have shed light on post-transcriptional regulation of genes and pathways through RNA binding proteins (RBP). Our lab has demonstrated that HuR, an RBP, is overexpressed in PDAC cells and stabilizes pro-survival mRNAs. Additionally, our work and others have demonstrated that this level of gene regulation can support drug resistance in PDAC cells. A synthetic lethal strategy employing Poly-ADP ribose polymerase inhibitors (PARPi) in a subset of patients with DNA repair deficient pancreatic cancers has been gaining interest. However, the success of PARPi is often hindered by the emergence of drug resistance in patients who initially respond. We have published that short-term PARPi treatment of PDAC cells causes activation of HuR where it stabilizes a DNA repair enzyme, PAR-glycohydrolase, and mediates acute PARPi resistance. In this study, we generated olaparib acquired resistant pancreatic cancer cells in vitro and acquired pancreatic patient derived xenograft cell lines (pre- and post PARPi) to understand acute versus acquired resistant mechanism(s). In characterising the acquired resistant model of PARPi resistance, we found that these cells are &gt;20 fold more resistant to olaparib and platinums and &gt;5 fold resistant to other PARPi like rucaparib and veliparib, compared to parental cells. No cross resistance was seen with other chemotherapeutics like gemcitabine. Additionally, we also found acquired resistant cells lost PARP-1 protein expression compared to parental cells. Bioinformatic analyses on HuR-RNA immunoprecipitation-microarray (RIP-microarray) data from acutely treated olaparib cells show enrichment of pro-survival mRNAs. Interestingly, these mRNAs are significantly downregulated in acquired resistant cells compared to control cells (i.e., negative log2 fold changes, p&lt;0.001) in differential expression of HuR and HuR established targets. Interestingly, upregulated gene transcripts in these samples belong to pathways that negatively regulate biosynthetic and metabolic processes, and hence may represent pathways to target. Further, in vitro analyses show that parental PDAC cells are sensitive to combined inhibition of PARP and HuR but acquired resistant cells fail to respond to HuR inhibition. In conclusion, HuR mediates acute resistance to PARPi in PDAC cells and HuR inhibitor therapy could enhance PARPi therapy immediately, yet is most likely not useful in the setting of acquired- resistance. Future studies will explore genetic alterations and novel HuR-independent pathways in PARPi acquired resistant cells. Finally, we have begun a line of investigation of combining PARPi therapy with HuR inhibitors in an effort to optimize upfront therapeutic efficacy

Citation Format: Aditi Jain, Matthew McCoy, Lebaron A. Agostini, Yuriy Gusev, Subha Madhavan, Michael Pishvaian, Sankar Addya, Eric Londin, Maria R. Gurevich, Chani Stossel, Talia Golan, Charles J. Yeo, Jonathan R. Brody. A global transcriptome analysis of pancreatic cancer cells distinguishes between acute and acquired PARP inhibitor resistance mechanisms [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 4764.

Abstract 1283: Targeting c-MYC and MAPK pathway to overcome pancreatic cancer drug resistance

Background: Acquired resistance to systemic chemotherapy is the main complication in pancreatic ductal adenocarcinoma (PDAC) treatment. Although there are studies focused on gemcitabine resistance mechanisms, our understanding of the mechanisms of nab-paclitaxel (n-PTX) treatment failure remains extremely limited. To enhance the use of properly powered patient-derived platforms, we adopted the conditionally reprogrammed (CR) cell culture technique in order to develop both parental and nab-PTX-resistant cells. The CR approach allowed us to identify the critical role of c-MYC and ERK in the PDAC drug response. Small molecule activators of PP2A (SMAPS) have showed activity in inhibiting lung KRAS-mutant tumor growth. We used SMAPS as new therapeutic agents in PDAC, for its ability to alter c-MYC activity through PP2A dysregulation and enhance PDAC sensitivity to n-PTX.

Methods: Long-term cultures of PDAC CRs were established from treatment-naive PDAC patients’ biopsies, and used to generate drug-resistant cells. Zebrafish and mouse model were used to test the cells’ ability to form tumors and to verify the drug resistance in vivo. Molecular analyses were used to characterize the drug-resistant cells and to identify key pathways involved in the drug resistance evolution. Genomic and chemical alterations of the key proteins were used to confirm the involvement in the drug resistance mechanism. We regulated the expression of c-MYC and ERK using SMAPS as a new targeting agent and trametenib to verify the direct correlation between c-MYC and ERK and the drug resistance mechanism.

Results: Using the credentialed KRAS-mutant CR cultures, we generated n-PTX-resistant cell lines. The parental and nab-PTX resistant cells were subjected to subcutaneous injections in nude mice, and formed tumors in 2-3 weeks. Histological evaluation showed that the CRs self-assembled into ductal structures, surrounded by a desmoplastic stromal microenvironment that faithfully recapitulates human PDAC. Resistant profiles were verified both in mouse and Zebrafish model. RNA microarrays identified a sustained induction of a pro-inflammatory pathway leading to c-MYC overexpression. c-MYC silencing and overexpression confirmed the role of c-MYCin the evolution of nab-PTX resistance. Treatment of the resistant CRs with either trametenib or with SMAPS resulted in enhanced sensitivity to nab-PTX. We furtherverified that the enhanced sensitivity was commensurate with a reduction in p-Erk and c-Myc.

Conclusion: The CR methodology addresses the need for a reliable method for generating primary cell lines on a single patient basis. The ability to rapidly model in vitro, and verify in vivo, that the overexpression of c-MYC contributes to the development of n-PTX resistance is a significant advancement in the field. Our data showed that SMAPs or trametanib overcome a significant component of the n-PTX resistance providing new hope for refractory PDAC.

Citation Format: Erika Maria Parasido, George S. Avetian, Jonathan Brody, Jordan Winter, Eric Londin, Michael Pishvaian, Eric Glasgow, Stephen Byers, Goutham Narla, Christopher Albanese. Targeting c-MYC and MAPK pathway to overcome pancreatic cancer drug resistance [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 1283.

Five-Fraction Stereotactic Body Radiation Therapy (SBRT) and Chemotherapy for the Local Management of Metastatic Pancreatic Cancer

BACKGROUND

The majority of patients with pancreatic cancer are diagnosed with metastatic disease at presentation. Nevertheless, local progression is responsible for up to 30% of deaths and can lead to significant morbidity. As a consequence, further exploration of effective methods of local control and palliation is essential. Stereotactic body radiation therapy (SBRT) is a widely utilized technique for the treatment of localized pancreatic cancer. Here, we report our experience with SBRT and chemotherapy for the local treatment of the metastatic patient population.

METHODS

This single institution retrospective review analyzed 20 patients with pathologically diagnosed metastatic adenocarcinoma of the pancreas. All patients underwent fiducial placement under endoscopic ultrasound (EUS) guidance. SBRT was delivered in five fractions to a total dose of 25 to 30 Gy. Patients received concurrent (given within 1 week of the start of SBRT) or sequential chemotherapy. Local tumor control was evaluated using Response Evaluation Criteria in Solid Tumors. Toxicity was graded using Common Terminology Criteria for Adverse Events version 4.03. Local control and overall survival were reported using the Kaplan-Meier method.

RESULTS

Patient median age was 64 years, and the median pre-treatment Eastern Cooperative Oncology Group performance status was 1. All patients received chemotherapy and half of the patients (10 of 20) received concurrent chemotherapy with folinic acid, fluorouracil, and oxaliplatin or fluorouracil, leucovorin, irinotecan, and oxaliplatin. Nearly all patients (19 of 20) received post-SBRT chemotherapy. Median time from pathological diagnosis to SBRT was 3.9 months. The twelve-month local control and overall survival were 43 and 53%, respectively. However, in patients with planning target volume (PTV) targets smaller than the population median, the 12-month local control was 78%. Median time to local progression (17.8 vs. 3.0 months, p = 0.02) and overall survival (24.9 vs. 8.8, p = 0.001) were also significantly improved in this smaller PTV cohort. Though not statistically significant, there was a trend towards improvement in local control (17.8 vs. 4.3 months, p = 0.17) and overall survival (16.7 vs. 9.7 months, p = 0.087) for those who received concurrent versus sequential chemotherapy, respectively. Lastly, there were no reported grade 3-5 late toxicities.

CONCLUSIONS

As systemic therapies improve, the local management of pancreatic cancer will become increasingly important. Here, we report significantly improved local control with SBRT of smaller PTV tumors with concurrent chemotherapy. Five-fraction SBRT offers a quick and effective modality of local tumor control with minimal toxicity in the metastatic pancreatic cancer population.

Abstract LB-B19: Re-sensitizing Pancreatic Cancer, targeted siRNA inhibition of HuR

We have demonstrated that 3DNA nanocarriers can specifically, effectively, and safely deliver siRNA oligos targeted against a pro-survival hub, HuR (the ELAVL1 gene) in an in vivo, pre-clinical model of pancreatic cancer. Pancreatic cancer remains one of the deadliest cancers with an overall 5 year survival rate of 9%; and is on pace to become the second leading cause of cancer related deaths in the U.S. by 2020. Pancreatic cancer is so deadly, in part, because it is highly refractory to standard chemotherapeutics. In fact, new standard of care regiments such as FOLFIRINOX have only improved survival by a few months. Our previous work has established HuR as a target in pancreatic cancer. HuR is an RNA binding protein that is primarily retained in the nucleus, but upon exposure to cancer associated stressors translocates to the cytoplasm. In the cytoplasm, HuR functions to bind, stabilize, and up-regulate expression of pro-survival target mRNAs. CRISPR-mediated deletion of HuR causes a xenograft lethal phenotype in vivo and increases sensitivity to a variety of drugs, particularly PARP inhibitor therapy, enhancing Olaparib therapy over 20-fold in vitro. In an independent doxycycline inducible knockdown model, HuR depletion combined with Olaparib treatment resulted in a 9.3 fold (p&lt;.001) decrease in tumor volume in vivo. Based on these findings and our previous published work, we have launched into a line of investigation attempting to target HuR in pancreatic cancer cells. We have delivered siHuR oligos tethered to 3DNA nanostructures (Genisphere, LLC) in a targeted fashion using either a folic acid targeting moiety, a transferrin receptor targeted antibody, or an EGFR targeted antibody (i.e., siHuR nanotherapy). Additionally, we are working to combine siHuR nanotherapy with conventional therapeutics. 3DNA nanocarriers are constructed using stable DNA strands assembled and crosslinked in a stepwise fashion, to create a layered nanoscaffold capable of attaching multiple different targeting moieties and deliverables. The siRNA oligos hybridized to the 3DNA were modified in order to withstand systemic RNases during treatment. We first validated the modified siHuR nanotherapy in vitro by evaluating protein and RNA levels of HuR. Second, we validated the expression of our intended targeting moieties in both human cell lines and a tissue microarray consisting of patient derived pancreatic cancer tumors. For the mouse studies, athymic female nude mice were injected with 4 million MIA PaCa-2 cells per flank, and randomized to treatment arms when tumors reached 100mm3. Mice were then treated intraperitoneally twice weekly with either siHuR or siControl nanotherapies (3ug siRNA per treatment) with one of the three targeting moieties. We demonstrated efficacy of systemic targeted delivery of siHuR nanotherapy which improved average overall survival by 35% (p=.012) compared to the control arm, with an increase in survival using a Kaplan-Meier survival analysis (p=.01). We are currently setting up treatments with siHuR nanotherapy in conjunction with a targeted treatment strategy, Olaparib, which has previously been shown to work in conjunction with dox-inducible HuR silencing (i.e.,shRNA targeting) in vivo. Herein, we describe the development of siHuR nanotherapy that, as a monotherapy or most likely with clinically available drugs, may improve outcomes for patients with pancreatic cancer.

Citation Format: Chris W. Schultz, Kevin O'Hayer, Kathryn M. Bormes, Teena Dhir, Samantha Brown, Avinoam Nevlar, Saswati Chand, Henry Thomsett, Wei Jiang, Jessica Bowers, Kelly Rhodes, Michael Pishvaian, Robert Getts, Jonathan Brody. Re-sensitizing Pancreatic Cancer, targeted siRNA inhibition of HuR [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 LB-B19.

Phase 1 Dose Escalation Study of MEDI-565, a Bispecific T-Cell Engager that Targets Human Carcinoembryonic Antigen, in Patients With Advanced Gastrointestinal Adenocarcinomas

INTRODUCTION

MEDI-565, a bispecific, single-chain antibody targeting human carcinoembryonic antigen on tumor cells and the CD3 epsilon subunit of the human T-cell receptor complex, showed antitumor activity in carcinoembryonic antigen-expressing tumors in murine models.

PATIENTS AND METHODS

This phase I, multicenter, open-label dose escalation study enrolled adults with gastrointestinal adenocarcinomas. MEDI-565 was given intravenously over 3 hours on days 1 through 5 in 28-day cycles, with 4 single-patient (0.75-20 μg) and 5 standard 3 + 3 escalation (60 μg-3 mg; 1.5-7.5 mg with dexamethasone) cohorts. Primary objective was determining maximum tolerated dose; secondary objectives were evaluating pharmacokinetics, antidrug antibodies, and antitumor activity.

RESULTS

Thirty-nine patients were enrolled (mean age, 59 years; 56% male; 72% colorectal cancer). Four patients experienced dose-limiting toxicities (2 at 3 mg; 2 at 7.5 mg + dexamethasone): hypoxia (n = 2), diarrhea, and cytokine release syndrome (CRS). Five patients reported grade 3 treatment-related adverse events: diarrhea, CRS, increased alanine aminotransferase, hypertension (all, n = 1), and hypoxia (n = 2); 6 experienced treatment-related serious adverse events: diarrhea, vomiting, pyrexia, CRS (all, n = 1), and hypoxia (n = 2). MEDI-565 pharmacokinetics was linear and dose-proportional, with fast clearance and short half-life. Nineteen patients (48.7%) had antidrug antibodies; 5 (12.8%) had high titers, 2 with decreased MEDI-565 concentrations. No objective responses occurred; 11 (28%) had stable disease as best response.

CONCLUSIONS

The maximum tolerated dose of MEDI-565 in this patient population was 5 mg administered over 3 hours on days 1 through 5 every 28 days, with dexamethasone. Pharmacokinetics were linear. No objective responses were observed.

A Phase 1, Multi-Center, Open-Label, Dose-Escalation Study of 131I-CLR1404 in Subjects with Relapsed or Refractory Advanced Solid Malignancies

This study explores the imaging and therapeutic properties of a novel radiopharmaceutical, (131)I-CLR1404. Phase 1a data demonstrated safety and tumor localization by SPECT-CT. This 1b study assessed safety, imaging characteristics, and possible antineoplastic properties and provided further proof-of-concept of phospholipid ether analogues' retention within tumors. A total of 10 patients received (131)I-CLR1404 in an adaptive dose-escalation design. Imaging characteristics were consistent with prior studies, showing tumor uptake in primary tumors and metastases. At doses of 31.25 mCi/m(2) and greater, DLTs were thrombocytopenia and neutropenia. Disease-specific studies are underway to identify cancers most likely to benefit from (131)I-CLR1404 monotherapy.

Irreversible multitargeted ErbB family inhibitors for therapy of lung and breast cancer

Overactivation of the ErbB protein family, which is comprised of 4 receptor tyrosine kinase members (ErbB1/epidermal growth factor receptor [EGFR]/HER1, ErbB2/HER2, ErbB3/HER3, and ErbB4/HER4), can drive the development and progression of a wide variety of malignancies, including colorectal, head and neck, and certain non-small cell lung cancers (NSCLCs). As a result, agents that target a specific member of the ErbB family have been developed for the treatment of cancer. These agents include the reversible EGFR tyrosine kinase inhibitors (TKIs) erlotinib and gefitinib; the EGFR-targeting monoclonal antibodies cetuximab and panitumumab; and the HER2-targeting monoclonal antibody trastuzumab. Lapatinib is a dual TKI that targets both EGFR and HER2. In addition, TKIs that inhibit multiple members of the ErbB family and also bind their targets irreversibly are under evaluation for the treatment of cancer. Three such compounds have progressed into clinical studies: the EGFR, HER2, and HER4 inhibitors afatinib, dacomitinib, and neratinib. Phase I studies of these agents have shown clinical activity in NSCLC, breast cancer, and other malignancies. Currently, afatinib is approved for EGFR mutation-positive NSCLC and is in development for squamous NSCLC, and dacomitinib is in phase III of clinical development for NSCLC, neratinib is in phase III of clinical development for the treatment of breast cancer, and afatinib is also in phase III development in head and neck cancer. Final results from clinical trials may lead to the potential approval of these agents in a variety of solid tumor malignancies.

A phase I study of the BCR-ABL tyrosine kinase inhibitor nilotinib and cetuximab in patients with solid tumors that can be treated with cetuximab

TPS2624

Background: Therapeutic blockade of Epidermal Growth Factor Receptor (EGFR) signaling with the monoclonal antibody cetuximab is clinically effective in the treatment of patients with metastatic squamous cell carcinoma of the head and neck or KRAS wildtype colorectal cancer. However, these patients eventually become resistant to this therapy. An exploration of the EGFR signaling network using an EGFR network-focused small interfering RNA library identified potential regulators of resistance to EGFR-targeted therapies. The ABL1 gene was identified as a central node to target in this complex genomic pathway. In a preclinical EGFR-expressing cancer cell line model, targeting c-abl, the gene product of ABL1, using nilotinib was found to be highly synergistic in decreasing cell survival when combined with anti-EGFR targeted therapy. Methods: We have initiated an open-label Phase I study for patients who progressed after standard therapies for metastatic KRAS wildtype colorectal cancer or metastatic head and neck squamous cell carcinoma. Enrolled patients must have adequate performance status and organ function. Treatment consists of cetuximab 400 mg/m2 on day 1, then 250 mg/m2 once weekly, and nilotinib twice daily, starting on day 1, according to a traditional 3+3 dose escalation, from 200mg to 300mg BID. Patients are restaged every 2 cycles (every 8 weeks). The primary endpoint is the maximum tolerated dose (MTD) of nilotinib when used in conjunction with cetuximab. Secondary endpoints are clinical benefit rate (defined as rates of stable disease, partial response, and complete response) and response rate. Additionally, biopsies of metastases obtained prior to and after initiation of therapy will be used to establish primary tumor cell cultures using conditional cellular reprogramming to permit the dynamic study of signaling and drug sensitivity through an evaluation of evidence of a drug effect on EGFR signaling and on Antibody-Dependent Cell-Mediated Cytotoxicity. An additional 10 colorectal cancer patients will be treated as an expansion cohort at the MTD. This expansion cohort data may be used to plan a Phase II trial in the future.

Quantifying the CDK inhibitor VMY-1-103's activity and tissue levels in an in vivo tumor model by LC-MS/MS and by MRI

The development of new small molecule-based therapeutic drugs requires accurate quantification of drug bioavailability, biological activity and treatment efficacy. Rapidly measuring these endpoints is often hampered by the lack of efficient assay platforms with high sensitivity and specificity. Using an in vivo model system, we report a simple and sensitive liquid chromatography-tandem mass spectrometry assay to quantify the bioavailability of a recently developed novel cyclin-dependent kinase inhibitor VMY-1-103, a purvalanol B-based analog whose biological activity is enhanced via dansylation. We developed a rapid organic phase extraction technique and validated wide and functional VMY-1-103 distribution in various mouse tissues, consistent with its enhanced potency previously observed in a variety of human cancer cell lines. More importantly, in vivo MRI and single voxel proton MR-Spectroscopy further established that VMY-1-103 inhibited disease progression and affected key metabolites in a mouse model of hedgehog-driven medulloblastoma.

A global, multicenter phase II trial of lapatinib plus capecitabine in gastric cancer

88

Background: Advanced gastric cancer (GC) is an incurable disease. HER2 overexpression has been reportedin 6%–35% of gastric and gastroesophageal tumors, whereas the EGFR is upregulated in about 18%–28%. Clinical studies confirm that targeting HER2 in combination with chemotherapy is an effective strategy, achieving a median survival of ∼13.5 mos. Lapatinib, a dual tyrosine kinase inhibitor of HER2 and the EGFR, inhibits tumor growth and modulates expression of fluoropyrimidine-targeting genes. LPT109747 is an international, multicenter phase II study investigating the combination of lapatinib + capecitabine in patients with advanced gastric or gastroesophageal junction adenocarcinoma.

Methods: Primary endpoints of the study included clinical response rate, 5 mo PFS and mRNA and protein expression levels of genes involved in the 5-FU and HER2 pathway. HER2 overexpression was not required at study entry. Oral lapatinib was administered (1,250 mg/d, continuously) during a monotherapy run-in period (day -7 to 0) and in combination with oral capecitabine (1,000 mg/m2 BID, 14 of 21 days). Patients were treated until disease progression (PD) or study withdrawal. Biopsies were performed on days -7 and 0. Safety was assessed every 3 weeks and response every 6 weeks by RECIST.

Results: Sixty-seven patients were included in the current analysis: 25% female, 75% male; 51% Caucasian, 45% Asian; median age 60 y (range: 22-89 y); 75% GC, 25% GEJ. All 67 patients were evaluable for response. The overall response rate was 22.4% (16.4% confirmed). 45% of patients had stable disease, and 24% had PD. No complete responses were observed. PD or death at < 5 mo was 63%. At the time of data cut off, PFS at 5 mo was 28.4% (17.3%–40.5%); median follow up was 26.4 weeks (CI: 22.1; 55.9); 39% of patients remain in follow up. Most frequent grade 3/4 events were anemia (13%), hand-foot syndrome (12%), decreased appetite (10%), and nausea (9%).

Conclusions: The combination of lapatinib + capecitabine shows promising efficacy and is well tolerated as 1st line treatment for advanced GC. An analysis of biomarker data may help identify who may benefit most from this regimen.

[Table: see text]

Restoration of DNA-binding and growth-suppressive activity of mutant forms of p53 via a PCAF-mediated acetylation pathway

Tumor-derived mutant forms of p53 compromise its DNA binding, transcriptional, and growth regulatory activity in a manner that is dependent upon the cell-type and the type of mutation. Given the high frequency of p53 mutations in human tumors, reactivation of the p53 pathway has been widely proposed as beneficial for cancer therapy. In support of this possibility p53 mutants possess a certain degree of conformational flexibility that allows for re-induction of function by a number of structurally different artificial compounds or by short peptides. This raises the question of whether physiological pathways for p53 mutant reactivation also exist and can be exploited therapeutically. The activity of wild-type p53 is modulated by various acetyl-transferases and deacetylases, but whether acetylation influences signaling by p53 mutant is still unknown. Here, we show that the PCAF acetyl-transferase is down-regulated in tumors harboring p53 mutants, where its re-expression leads to p53 acetylation and to cell death. Furthermore, acetylation restores the DNA-binding ability of p53 mutants in vitro and expression of PCAF, or treatment with deacetylase inhibitors, promotes their binding to p53-regulated promoters and transcriptional activity in vivo. These data suggest that PCAF-mediated acetylation rescues activity of at least a set of p53 mutations. Therefore, we propose that dis-regulation of PCAF activity is a pre-requisite for p53 mutant loss of function and for the oncogenic potential acquired by neoplastic cells expressing these proteins. Our findings offer a new rationale for therapeutic targeting of PCAF activity in tumors harboring oncogenic versions of p53.

Abstract 4833: Glucose restriction induces degradation of p53 mutants via a selective autophagy-mediated pathway

Introduction. More than 50% of human tumors harbor missense mutations of the p53 gene product. In its wild-type conformation p53 is degraded via the proteasome, mainly through the action of the MDM2 E3 ubiquitin ligase. Unlike the wild-type protein, mutant forms of p53 accumulate at high levels and elude proteolysis, in part due to an altered modality of interaction with MDM2. High levels of p53 mutants in tumors appear to correlate with resistance to radio- and chemo-therapy, and are proposed to promote tumor progression. Furthermore, therapeutic interventions aimed at reducing p53 mutant levels have shown anti-tumor activity in vitro and in vivo. The mechanisms that regulate the stability of wild-type p53 are well understood during the DNA damage response. However, p53 can also be stabilized during adaptive metabolic stress conditions, such as during glucose deprivation. The goal of this work was to determine the effects of glucose availability on the oncogenic activity of mutant p53.

Methods. We investigated the effects of glucose availability in tumor cells expressing p53 mutants, in transgenic animals harboring p53 mutant alleles, and in xenograft models of breast cancer. The read-outs of these experiments were p53 stability, cellular proliferation and response to therapeutic agents.

Results. We found that p53 mutant protein levels are exquisitely sensitive to glucose availability: high glucose levels stabilize p53 mutants, while glucose restriction (GR) leads to their MDM2- and proteasome-independent degradation. This degradation requires instead the participation of the autophagic machinery and of the autophagic protein Beclin-1, which forms a complex with p53 in GR-treated cells. Importantly, in breast cancer cell lines GR alone does not lead to a net increase in autophagic flux, thus differing from autophagy activated during serum- or amino acid- depletion. Rather, GR uses the autophagic machinery to degrade selective targets, such as mutant p53. We further show that tumor cells where p53 mutant levels are lower due to GR, have reduced proliferation potential compared to tumors expressing native p53, and can be easily chemo-sensitized, significantly reducing the IC50 of all drugs examined. We then asked whether dietary restriction of glucose affects p53 mutant stability in living organisms. Preliminary results indicate that p53 mutant levels are higher in tissues of animals fed with high glucose-diet, relative to animals fed with a low glucose diet. We are currently investigating whether this change in p53 levels affects proliferation rates.

Conclusions. We propose that GR uses the autophagic machinery to induce degradation of oncogenic mutant p53, and thus interrupts their proliferative signals. Our findings further imply that dietary restriction of glucose would keep p53 mutant activity in check. Finally, GR overcomes the well-known chemo-resistance conveyed by p53 mutations.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4833.

Disruption of transforming growth factor-beta signaling through beta-spectrin ELF leads to hepatocellular cancer through cyclin D1 activation

Transforming growth factor-beta (TGF-beta) signaling members, TGF-beta receptor type II (TBRII), Smad2, Smad4 and Smad adaptor, embryonic liver fodrin (ELF), are prominent tumor suppressors in gastrointestinal cancers. Here, we show that 40% of elf(+/-) mice spontaneously develop hepatocellular cancer (HCC) with markedly increased cyclin D1, cyclin-dependent kinase 4 (Cdk4), c-Myc and MDM2 expression. Reduced ELF but not TBRII, or Smad4 was observed in 8 of 9 human HCCs (P<0.017). ELF and TBRII are also markedly decreased in human HCC cell lines SNU-398 and SNU-475. Restoration of ELF and TBRII in SNU-398 cells markedly decreases cyclin D1 as well as hyperphosphorylated-retinoblastoma (hyperphosphorylated-pRb). Thus, we show that TGF-beta signaling and Smad adaptor ELF suppress human hepatocarcinogenesis, potentially through cyclin D1 deregulation. Loss of ELF could serve as a primary event in progression toward a fully transformed phenotype and could hold promise for new therapeutic approaches in human HCCs.

Cross-regulation of beta-catenin-LEF/TCF and retinoid signaling pathways

Vitamin A derivatives (retinoids) are potent regulators of embryogenesis, cell proliferation, epithelial cell differentiation and carcinogenesis [1]. In breast cancer cells, the effects of retinoids are associated with changes in the cadherin-beta-catenin adhesion and signaling system [2] [3]. beta-catenin is a component of the Wnt signaling pathway, which regulates several developmental pathways [4]. Increases in cytoplasmic beta-catenin and beta-catenin signaling are also associated with numerous cancers, and are particularly important in colon cancer [5]. The oncogenic and developmental effects of beta-catenin are mediated by its interaction with and activation of members of the LEF/TCF family of transcription factors [6] [7] [8]. Here, we shown that retinoic acid (RA) decreases the activity of the beta-catenin-LEF/TCF signaling pathway. This activity of RA was independent of the adenomatous polyposis coli (APC) tumor suppressor and ubiquitination-dependent degradation of cytoplasmic beta-catenin. Consistent with this finding, beta-catenin interacted directly with the RA receptor (RAR) in a retinoid-dependent manner, but not with the retinoid X receptor (RXR), and RAR competed with TCF for beta-catenin binding. The activity of RA on RAR-responsive promoters was also potentiated by beta-catenin. The data suggest that direct regulation of beta-catenin-LEF/TCF signaling is one mechanism whereby RA influences development, cell differentiation and cancer.

Retinoids increase cell-cell adhesion strength, beta-catenin protein stability, and localization to the cell membrane in a breast cancer cell line: a role for serine kinase activity

In this study we show that a breast cancer cell line (SKBR3) that expresses no E-cadherin and very low levels of beta-catenin protein and exhibits a poorly adhesive phenotype in Matrigel responds to retinoic acid (RA) by a marked increase in epithelial differentiation. Specifically, treatment of cells with all-trans-RA, 9-cis-RA, or a RA receptor alpha-specific ligand resulted in a large increase in cell-cell adhesive strength and stimulated the formation of fused cell aggregates in Matrigel. A retinoid X receptor-specific ligand was ineffective. Exposure of cells to 9-cis-RA for as little as 4 h was sufficient to maintain the adhesive phenotype for at least 4 days. The effects of 9-cis-RA required protein and RNA synthesis, but were not mediated by factors secreted by stimulated cells or by direct cell contact and did not require serum. These 9-cis-RA-induced morphological effects were completely reversed by growing cells in 50 microM Ca2+, suggesting a mechanism involving a 9-cis-RA-induced increase in Ca(2+)-dependent adhesion. Consistent with this, beta-catenin protein levels were markedly elevated in the 9-cis-RA-treated cells, and beta-catenin became localized to a Triton-insoluble pool at regions of cell-cell contact. No change could be detected in beta-catenin steady state messenger RNA levels, but 9-cis-RA did increase beta-catenin protein stability. Treatment of cells with low calcium medium did not prevent the 9-cis-RA-induced increase in total beta-catenin protein, but did prevent its movement to a Triton-insoluble pool at the cell membrane. Among several kinase inhibitors, only the broad spectrum kinase inhibitor staurosporine and the protein kinase C inhibitor bisindoylmaleimide reversed the morphological changes induced by 9-cis-RA. Like treatment with low calcium medium, these inhibitors did not prevent the 9-cis-RA-induced increase in total beta-catenin protein levels, but completely prevented the movement of beta-catenin to the cell membrane. These results point to a role for beta-catenin and serine kinase activity in mediating the action of 9-cis-RA in epithelial differentiation.