Citations

Abstract Although the last two decades have seen a broad improvement in overall survival, colorectal cancer is still the second leading cause of cancer deaths worldwide. Patient populations continue to face poor disease prognoses due to the challenges of early detection and the molecular subtypes driving their colorectal cancer. Consequently, many patients present with metastatic colorectal cancer, which often limits options and shifts treatment focus away from curative interventions. BRAFV600E mutations are present in approximately 10% of colorectal cancer tumors and are associated with uninhibited cell proliferation, reduced apoptosis, and resistance to standard therapeutic options. In colorectal cancer, BRAFV600E mutations are associated with decreased overall survival, poor treatment responses, and different patterns of metastatic spread compared with tumors with wild-type BRAF. Success in treating other BRAFV600E-mutant cancers with BRAF inhibitors as monotherapy has not translated into efficacious treatment of metastatic colorectal cancer. Consequently, combination therapy with inhibitors of BRAF, MEK, and EGFR, which overcomes the innate treatment-resistant characteristics of BRAFV600E-mutant colorectal cancer, is now recommended by treatment guidelines.

Abstract Purpose: The RAS/RAF/MEK/ERK signaling pathway is critical to the development of colorectal cancers, and KRAS, NRAS, and BRAF mutations foster resistance to radiation. We performed a phase I trial to determine the safety of trametinib, a potent MEK1/2 inhibitor, with 5-fluorouracil (5-FU) chemoradiation therapy (CRT) in patients with locally advanced rectal cancer (LARC). Patients and Methods: Patients with stage II/III rectal cancer were enrolled on a phase I study with 3+3 study design, with an expansion cohort of 9 patients at the MTD. Following a 5-day trametinib lead-in, with pre- and posttreatment tumor biopsies, patients received trametinib and CRT, surgery, and adjuvant chemotherapy. Trametinib was given orally daily at 3 dose levels: 0.5 mg, 1 mg, and 2 mg. CRT consisted of infusional 5-FU 225 mg/m2/day and radiation dose of 28 daily fractions of 1.8 Gy (total 50.4 Gy). The primary endpoint was to identify the MTD and recommended phase II dose. IHC staining for phosphorylated ERK (pERK) and genomic profiling was performed on the tumor samples. Results: Patients were enrolled to all dose levels, and 18 patients were evaluable for toxicities and responses. Treatment was well tolerated, and there was one dose-limiting toxicity of diarrhea, which was attributed to CRT rather than trametinib. At the 2 mg dose level, 25% had pathologic complete response. IHC staining confirmed dose-dependent decrease in pERK with increasing trametinib doses. Conclusions: The combination of trametinib with 5-FU CRT is safe and well tolerated, and may warrant additional study in a phase II trial, perhaps in a RAS/RAF-mutant selected population.

4099 Background: There is strong rationale to combine an m-TOR inhibitor (TEM) with a VEGF inhibitor (BEV) as a potentially active and well tolerated treatment for HCC. Both agents have shown modest single agent activity in HCC and so evaluated here in a phase II trial. Methods: A modified 2-stage Simon design planned 25 or 50 patients (pts) to test the null hypothesis that true tumor response rate is at most 10% andtrue 6-mo progression-free survival rate (PFS) (by RECIST) is at most 65%, or no better than single agent BEV (6 mo PR >2 pts or PFS 6 mo >18 out of 25.) Toxicity, TTP, PFS and survival were 2nd endpoints. Eligible pts had confirmed HCC with disease unresectable or amenable to other localised therapies, Child Pugh A liver status and no prior systemic therapy involving the VEGF or m-TOR class of agents. TEM was administered at starting dose 25 mg IV d1,8,15,22 with BEV at 10mg/kg IV d 1, 15, all q 28 days (1 cycle). Imaging was q 8 wks. Results: From 09/09 to 09/11, 27 eligible pts were enrolled with 25 evaluable for toxicity and efficacy. Med age 59 yrs, 85% male, PS 0/1: 35/65, 58% metastatic, >85% BCLC stage C. With med 6 cycles (range 1-14) delivered, most pts (88%) experienced a grade 3+ adverse event (a/e.) Common grade 3 a/es related to treatment included thrombocytopenia (40%), neutropenia (20%), leucopenia (12%), fatigue (8%), anemia, mucositis, dyspnea, diarrhea, bleeds, fistula, infections (4% each). There was one possible treatment related death. Per protocol dose reductions/discontinuation for TEM-related a/es were most common. There were 2 confirmed PRs and 16 pts progression-free by 6 mos. A third pt developed a late PR at cycle 13. Median TTP on study was 6 mos, median PFS was 7.4 mos and median survival was 8.3 mos, with 13 pts still alive. Accrual closed at end of stage 1 as neither the number of responses nor the PFS at 6 mos passed the futility stopping rule set for this combination. Conclusions: This multicenter study is the first HCC trial evaluating the BEV/TEM doublet. Despite manageable toxicity, the ORR and 6 mo PFS did not surpass assumptions based on single agent BEV in HCC. Further study of BEV/TEM combination in this advanced HCC population is not recommended.

11586 Background: Hand-foot skin reaction (HFSR) is the most common regorafenib adverse event. However, no intervention has demonstrated efficacy in preventing or palliating this adverse event, short of modulating the regorafenib dose. Methods: The Regorafenib Dose Optimization Study (ReDOS) was a randomized trial ( https://clinicaltrials.gov/ct2/show/NCT02368886 ); here we describe an a priori secondary analysis of ReDOS with the goal of assessing whether clobetasol 0.05% cream (a potent corticosteroid) applied to the palms and soles twice per day is more effective when prescribed pre-emptively (before the development of HFSR) versus reactively (after the development of HFSR). Patients were assessed during the 1st 2 cycles of regorafenib. Results: Among 116 evaluable patients, 61 received pre-emptive clobetasol, and 55 reactive clobetasol. Baseline demographics were comparable between groups. During the 1st regorafenib cycle, 46% and 52% of patients developed HFSR with pre-emptive and reactive clobetasol, respectively (p = 0.52). However, during the 2nd cycle, 56% (of 47 total patients) and 80% (of 41 total patients), developed this toxicity with pre-emptive and reactive clobetasol, respectively (p = 0.02). Of note, during the 2nd cycle, rates of grade 1,2, and 3 HFSR were 40%, 11%, and 4% (pre-emptive) and 45%, 25%, and 10% (reactive) (p = 0.07). A sensitivity analysis to examine rates of no HFSR over all 2 regorafenib cycles showed that no HFSR occurred in 33% (of 61 total patients) with pre-emptive clobetasol versus 15% (of 55 total patients) with reactive clobetasol (p = 0.02). Patient-reported outcomes showed HFSR compromised activities of daily living, including getting dressed, preparing meals, walking, and even driving, with seemingly worse descriptive outcomes in patients who received reactive therapy. No adverse events from clobetasol were reported. Conclusions: Compared to reactive therapy, pre-emptive topical clobetasol might lessen regorafenib-induced HFSR. Clinical trial information: NCT02368886.

Objectives Liposomal irinotecan (nal-IRI) is a topoisomerase inhibitor proven to improve survival in metastatic pancreatic cancer (mPC). This study describes real-world characteristics of patients treated with nal-IRI for mPC. Methods Patients 18 years or older diagnosed with stage IV mPC and treated with nal-IRI were selected retrospectively from a deidentified electronic health record database of more than 2 million US cancer patients. Demographics, clinical and dosing characteristics, and treatment outcomes were collected. Results Of 257 total patients, 145 (57%) received nal-IRI as first- or second-line therapy. Median nal-IRI treatment duration was 51 days, longer when nal-IRI was used as first/second versus as third-line therapy or later (62 vs 44.5 days). Seventy patients (27.2%) experienced dose modification. Median time to treatment discontinuation was 2.3 versus 1.6 months for first-/second- versus third-line therapy or later, respectively. Median overall survival from nal-IRI initiation was 5.6 versus 4.1 months for first-/second- versus third-line therapy or later, respectively. Prior irinotecan treatment, baseline serum albumin less than 40 g/L, and baseline neutrophil-to-lymphocyte ratio greater than 5 were associated with reduced overall survival. Conclusions This is the first large US study of real-world US mPC patients treated with nal-IRI. These results, comparable to the NAPOLI-1 trial, can help inform future studies and the efficacy of nal-IRI in mPC therapy.

TPS594 Background: Effective treatment options are very limited for patients with advanced refractory biliary tract cancer (BTC). Fluoropyrimidine-based chemotherapy regimen such as 5-fluorouracil and irinotecan are frequently utilized for these patients after first-line therapy despite lack of FDA approval. Trifluridine/tipiracil (FTD/TPI) is a novel oral nucleoside with antitumor activity in both fluoropyrimidine sensitive and resistant tumors due to its unique mechanisms of action. Given early toxicity and efficacy data from our previous study on single-agent trifluridine/tipiracil (FTD/TPI) in advanced BTC, the clinical evaluation of its combination with irinotecan represents a rational approach for the treatment of advanced refractory BTC. Methods: This is a single-arm phase II trial with a two-stage design to assess the efficacy of trifluridine/tipiracil (FTD/TPI) and irinotecan in advanced refractory BTC. Key eligibility criteria include histologically confirmed advanced, unresectable BTC who have progressed on at least one line of systemic therapy and have measurable disease per RECIST v1.1. Target accrual is 25. Treatment includes trifluridine/tipiracil (FTD/TPI) 25 mg/m2 on days 1-5 and irinotecan 180 mg/m2 on day 1 in 14-day cycles. Patients will be evaluated for response every 4 cycles and in the absence of disease progression, therapy may be given up to 2 years. The primary end point is the progression-free survival rate at 16 weeks. Secondary endpoints include overall response rate, disease control rate, progression-free survival, overall survival, and incidence of adverse events. Correlative biomarker studies include evaluations of circulating tumor DNA and circulating tumor cells at baseline, after 4 cycles and at progression; and development of patient-derived tumor organoids from pre-treatment biopsies for parallel treatments. This study was approved and funded in part by the National Comprehensive Cancer Network (NCCN) Oncology Research Program from general research support provided by Taiho Oncology, Inc. Clinical trial information: NCT 04072445.

TPS592 Background: For advanced CCA, standard of care 1L systemic treatment is GEM + CIS. Genetic alterations in intrahepatic CCA provide potential therapeutic targets. Fibroblast growth factor receptor (FGFR) 2 gene rearrangements driving CCA tumorigenesis were identified almost exclusively in intrahepatic CCA patients (pts) (incidence, 10–16%). In phase 2, PEM (INCB054828), a selective, potent, oral FGFR1–3 inhibitor elicited an objective response rate (ORR) of 35.5% and median progression-free survival (PFS) of 6.9 months (mo) in previously treated, locally advanced or metastatic CCA with FGFR2 rearrangements (NCT02924376). FIGHT-302, a randomized, open-label, phase 3 study will evaluate efficacy and safety of 1L PEM vs GEM + CIS in unresectable/metastatic CCA with FGFR2 fusions or rearrangements (NCT03656536). Methods: Eligible pts are adults with confirmed unresectable/metastatic CCA; no prior systemic therapy for advanced disease < 6 mo before enrollment; radiographically measurable/evaluable disease (per RECIST v1.1); ECOG PS ≤1; documented FGFR2 fusions or rearrangements. Exclusions include clinically significant corneal or retinal disorder; history of calcium and phosphate homeostasis disorder or systemic mineral imbalance with ectopic soft tissue calcification; untreated CNS metastases or history of uncontrolled seizures. Pts will be randomized (1:1; stratified by region and tumor burden) to PEM 13.5 mg QD on a 21-day (d) cycle or GEM (1000 mg/m2) + CIS (25 mg/m2) on D1 and D8 of 21-d cycles (max 8). Crossover to PEM allowed after confirmed progression. PEM titration to 18 mg from cycle 2 allowed for pts without hyperphosphatemia (serum phosphate > 5.5 mg/dL) and Grade ≥2 treatment-related adverse events during cycle 1. Hyperphosphatemia will be managed with diet modifications, phosphate binders, diuretics, or dose adjustments. Treatment will continue until progression or unacceptable toxicity. Primary endpoint is PFS (by independent review). Secondary endpoints are ORR, overall survival, duration of response, disease control rate, safety, and quality of life. Four pts (target N = 432) are enrolled as of Sep 25, 2019. Clinical trial information: NCT03656536.

746 Background: Pelareorep is a proprietary formulation of live, replication-competent, naturally occurring Reovirus Type 3 Dearing strain. A randomized phase II trial of pelareorep in combination with carboplatin and paclitaxel in first-line treatment of metastatic PDAC (NCT01280058) was performed. Although pelareorep did not improve the primary endpoint of progression-free survival compared to carboplatin and paclitaxel alone, impressive durable responses were seen in the pelareorep arm in some patients (pts). Further, prior studies have noted the immunomodulatory carcinoembryonic antigen-related cell adhesion molecule (CEACAM6/CD66c) as a receptor for specific viral subtypes. We thus speculated that altered CEACAM6 levels may be predictive for pelareorep sensitivity. Methods: Pre-treatment tissue biopsies were collected prior enrolment for all 73 pts on study. Evaluable pts with transcriptomic data was available for only 31 pts. RNA was purified from FFPE tissue and gene expression analysis was performed using SensationPlus FFPE Amplification and WT labelling kit and the Human Transcriptome Array 2.0. CEACAM6 protein expression was determined by immunohistochemistry. Differential gene expression and survival analysis using were performed in R/Bioconductor. Appropriate corrections for multiplicity were performed. Results: When comparing extraordinary responders in the pelareorep treated arm to those with poor outcomes, low levels of CEACAM6 mRNA expression were associated with prolonged PFS in pelareorep-treated pts (adjusted p = 0.05). This effect was not seen in non-pelareorep treated pts. The luminal, but not the cytoplasmic immunohistochemistry score, was highly correlated with mRNA expression levels of CEACAM6, p = 0.001. Modulation of CEACAM6 in vitro and in vivo are underway. Conclusions: CEACAM6 may be a candidate biomarker of sensitivity to pelareorep and, in theory, could improve viral trafficking of this compound in tumor cells. Clinical trial information: NCT01280058 . [Table: see text]

713 Background: AbGn-107 is an ADC directed against AG-7 antigen, a Lewis A-like glycol-epitope expressed in 24-61% of gastric (G), colorectal (CRC), pancreatic (PDA), and biliary (BIL) cancers. Based on promising antitumor activity of AbGn-107 in both in vitro and in vivo preclinical studies, we performed a Phase Ia trial in pts with the aforementioned GI malignancies. Methods: Standard 3+3 dose escalation was used. Key eligibility criteria: locally adv or metastatic G, CRC, PDA, or BIL cancer, previously treated, ECOG PS 0-1; positive AG-7 expression was not required. Two dosing intervals were tested: AbGn-107 administered i.v. Q4 weeks (at doses ranging from 0.1-1.2 mg/kg) and Q2 weeks (at doses from 0.8-1.0 mg/kg). DLTs were based on grade 3/4 hematologic and non-heme AEs occurring during the initial 4-week rx window. Pts were treated until dz progression or unacceptable toxicity, with tumor assessments Q8 weeks. 1o objectives: safety and MTD; 2o objectives: PK, immunogenicity, and efficacy defined by ORR (RECIST 1.1). Results: 35 patients were enrolled across 6 dose levels (median age 61.5 yo (range 40 – 81); G (0)/CRC (12)/PDA (20)/BIL (3); median # lines of prior rx = 3 (range 1-7). Safety: 5 pts experienced Grade 3 or 4 neutropenia, all at higher dose levels, with 1 episode of febrile neutropenia. Other frequent drug-related AEs, mostly grade 1/2, inc. fatigue (29%), nausea (20%), and diarrhea (14%). DLTs include grade 4 CK elevation (n = 1) at 0.8 mg/kg Q4W and grade 3 arthralgias (n = 1) at 1.2 mg/kg Q4W. MTD was not reached at either 1.2 mg/kg Q4W or 0.8 mg/kg Q2W; the 1.0 mg/kg Q2W cohort will complete enrollment in Oct 2019. Efficacy: Median duration of treatment = 56 days (range, 8 – 225 days); best response observed to date is stable dz lasting > 6 months at 0.8 mg/kg Q4W and Q2W cohorts (n = 1 each). Conclusions: Overall, AbGn-107 appears well-tolerated with encouraging prelim signs of efficacy (prolonged dz control) in non-biomarker selected pts with advanced GI cancers. Pre-screening for high AG-7 expression is underway for subjects with G, CRC, PDA, and BIL cancers for the cohort expansion phase of this study, which will be open across multiple sites in U.S. and Taiwan. Clinical trial information: NCT02908451.