Kim, Richard D.

415 Background: Immune checkpoint inhibitors (ICI) have been approved in solid tumors with dMMR. However, only limited data are available for PDAC with dMMR given the rarity of dMMR in PDAC. We evaluated efficacy of ICIs in PDAC with dMMR. Methods: Retrospective clinical and pathologic data were collected for patients (pts) with pancreatic adenocarcinoma from May 2017 to June 2020 at Moffitt cancer center. Results: We identified 10 pts with dMMR PDAC. The median age was 64.5 years (range: 42-86) and 4 pts were male. 4 pts had resectable disease, 3 had locally advanced and 3 had metastatic disease at initial diagnosis. MSH6 deficiency (def) was found in 2 cases, PMS2 def in 2, MLH/PMS2 def in 5, and MSH2/MSH6 in 1. 7 pts were treated with ICIs. 3 pts had locally advanced and 4 had metastatic disease when they started ICIs. 5 received Pembrolizumab (pem), 1 received ipilimumab/ nivolumab (ipi/nivo), and 1 received pem then ipi/nivo after progressive disease (PD) on pem. The median number of prior lines of chemotherapy was 1 (range 0-2). 6 pts were evaluable, and 1 had rapid disease progression after 1 dose of pem. Among 6 evaluable pts, 3 had an objective response (1: complete response and 2: partial response), and 2 had stable disease (SD). Median progression-free survival was 8.2 mo, and median overall survival was not reached with median follow-up (FU) of 6.8 mo. The median duration of response was not reached with a median FU of 22.6 mo. The pt with CR remained disease-free for up to 22 months. The pt whose treatment was switched to ipi/nivo after PD on pem achieved SD > 4mo on ipi/nivo. While on immunotherapy, one patient with ipi/nivo developed immunotherapy associated rash requiring systemic steroids, and another on pem developed hypothyroidism requiring levothyroxine. Conclusions: This series suggest ICIs can provide durable clinical efficacy in pts with dMMR PDAC.

Abstract Lessons Learned The combination of trametinib and sorafenib has an acceptable safety profile, albeit at doses lower than approved for monotherapy. Maximum tolerated dose is trametinib 1.5 mg daily and sorafenib 200 mg twice daily. The limited anticancer activity observed in this unselected patient population does not support further exploration of trametinib plus sorafenib in patients with hepatocellular carcinoma. Background The RAS/RAF/MEK/ERK signaling pathway is associated with proliferation and progression of hepatocellular carcinoma (HCC). Preclinical data suggest that paradoxical activation of the MAPK pathway may be one of the resistance mechanisms of sorafenib; therefore, we evaluated trametinib plus sorafenib in HCC. Methods This was a phase I study with a 3+3 design in patients with treatment-naïve advanced HCC. The primary objective was safety and tolerability. The secondary objective was clinical efficacy. Results A total of 17 patients were treated with three different doses of trametinib and sorafenib. Two patients experienced dose-limiting toxicity, including grade 4 hypertension and grade 3 elevation of aspartate aminotransferase (AST)/alanine aminotransferase (ALT)/bilirubin over 7 days. Maximum tolerated dose was trametinib 1.5 mg daily and sorafenib 200 mg twice a day. The most common grade 3/4 treatment-related adverse events were elevated AST (37%) and hypertension (24%). Among 11 evaluable patients, 7 (63.6%) had stable disease with no objective response. The median progression-free survival (PFS) and overall survival (OS) were 3.7 and 7.8 months, respectively. Phosphorylated-ERK was evaluated as a pharmacodynamic marker, and sorafenib plus trametinib inhibited phosphorylated-ERK up to 98.1% (median: 81.2%) in peripheral blood mononuclear cells. Conclusion Trametinib and sorafenib can be safely administered up to trametinib 1.5 mg daily and sorafenib 200 mg twice a day with limited anticancer activity in advanced HCC.

Abstract Purpose: Patients with metastatic colorectal cancer refractory to chemotherapy have limited treatment options. Ensituximab (NEO-102) is a novel chimeric mAb targeting a variant of MUC5AC with specificity to colorectal cancer. Patients and Methods: Single-arm, phase II trial assessed the efficacy and safety of ensituximab in patients with advanced, refractory cancer who expressed MUC5AC antigen in tumor tissue. Ensituximab was administered intravenously every 2 weeks with 3 mg/kg as recommended phase II dose (RP2D). A minimum sample size of 43 patients was required on the basis of the assumption that ensituximab would improve median overall survival (OS) by 7 months using a one-sided significance level of 10% and 80% power. Written informed consent was obtained from all patients. Results: Sixty-three patients with advanced, refractory colorectal cancer were enrolled and 53 subjects were treated in phase II arm. Median age was 58 years and 46% of the patients were female. Among 57 evaluable patients, median OS was 6.8 months. No responses were observed, and stable disease was achieved in 21% of the patients. The most common treatment-related adverse events (AE) at RP2D included fatigue (38%), anemia (30%), nausea (15%), vomiting (11%), increased bilirubin (9%), constipation (8%), decreased appetite (6%), and diarrhea (6%). Serious AEs at least possibly related to ensituximab occurred in 4 patients and included anemia, nausea, increased bilirubin, and hypoxia. No patients discontinued treatment due to drug-related AEs. Conclusions: Ensituximab was well tolerated and demonstrated modest antitumor activity in patients with heavily pretreated refractory colorectal cancer.

Hepatocellular carcinoma (HCC) is the most common primary liver cancer with dismal prognosis when diagnosed at advanced stages. Surgical resection of the primary tumor or orthotropic liver transplantation serves as a potential curative option. However, this approach is highly dependent on the hepatic reserve and baseline functional status of the patient. Liver directed therapies such as portal vein embolization (PVE), trans-arterial chemoembolization (TACE), and systemic chemotherapy are employed in non-surgical candidates. Sorafenib was the only approved systemic therapeutic agent for almost a decade until the recent approval of lenvatinib by the United States Food and Drug Administration (FDA) as an alternate first-line agent. Regorafenib, nivolumab, pembrolizumab and cabozantinib are approved by the FDA as second-line agents in patients who failed or could not tolerate sorafenib. Ramucirumab was recently FDA approved for the subset of patients that have high alfa-fetoprotein levels (>400 ng/mL). A better understanding of tumorigenesis and encouraging clinical trial results that evaluated immune-checkpoint inhibitors opened doors for immunotherapy in HCC. Immune checkpoint inhibitors have demonstrated a prolonged median overall and progression-free survival in a subset of patients with HCC. On-going translational and clinical research will hopefully provide us with a better understanding of tumor markers, genetic aberrations and other factors that determine the immunotherapy response in HCC. In this review, we sought to summarize the potential role and future directions of immunotherapy in the management of HCC.

TPS4149 Background: Patients with advanced gastric cancer experience a 5 year survival rate <10% even with multimodality therapy representing a clear unmet need for improved treatment. In advanced gastric and gastroesophageal junction (GEJ) adenocarcinoma, ramucirumab (a monoclonal antibody against VEGFR2) has demonstrated clinical activity and has been approved as second line therapy in combination with paclitaxel with a response rate of 28% and absolute overall survival benefit of 8 weeks when compared to placebo. However, there are many patients that cannot tolerate paclitaxel due to prior exposure to oxaliplatin causing neuropathy. Therefore, novel combinations with ramucirumab, is highly desirable. TAS-102 is an oral cytotoxic agent with two active components; trifluridine (TFD) which inhibits tumor cell growth by being incorporated into DNA during DNA synthesis and tipiracil (TPI) which inhibits the metabolism of TFD, thereby prolonging its ability to exert effect. TPI also inhibits platelet derived endothelial cell growth factor which plays a key role with VEGF in tumor angiogenesis. The combination of a cytotoxic agent with an antiangiogenic agent has demonstrated a significant anticancer activity in multiple cancers. In a recent Phase III study, TAS-102 significantly prolonged overall survival as compared to best supportive care in patients with GEJ and gastric cancers that had received at least 2 prior lines of treatment. We hypothesize that a combination of TAS-102 and ramucirumab might increase efficacy without causing unmanageable toxicity. Methods: This is a single institutional phase II single arm two-stage design trial using the combination of TAS-102 and ramucirumab in advanced, refractory gastric or GEJ adenocarcinoma. Eligible patients include those with histologically confirmed gastric or GEJ adenocarcinoma that have received at least 1 prior line of treatment with performance status 0 or 1 and preserved organ function. Ramucirumab will be administered 8mg/kg every 2 weeks and TAS-102 at doses of 35 mg/m2 twice daily. Each cycle length will be 28 days. The primary endpoint is 6 month OS and secondary endpoints are safety, objective response rate and PFS. Fifteen patients will be enrolled in the first stage. If ≥ 7 of the 15 are alive at 6 months, an additional 10 patients will be enrolled in the second phase. Enrollment is currently ongoing. Clinical trial information: NCT03686488.

398 Background: The PI3K/mTOR pathway has emerged as a potential target for anticancer therapy. Considerable evidence suggests that targeting a single isoform of PI3K (p110α) would have sufficient antitumor activity and improved therapeutic window. Further, PI3KCA mutations, gene encoding isoform p110α, are described in pancreatic adenocarcinoma (PAC). BYL719 is an oral class I α-specific PI3K inhibitor that showed preclinical anti-tumor activity. The first in human phase 1 trial of BYL719 defined the maximum tolerated dose (MTD) at 400mg QD. Methods: This was a phase I, single center study (standard 3+3 design). The primary objective was to determine the MTD of BYL719 in combination with gemcitabine (G) and nab-paclitaxel (nabP) as frontline therapy in locally advanced or metastatic PAC. BYL719 was given orally daily (Table). Patients (pts) were restaged q2 cycles. The study was closed prematurely due to slow accrual. Results: Fifteen pts were enrolled (median age was 58 years). Three pts each participated in cohorts 1 and 2. Nine pts were enrolled in cohort 3, but 4 were replaced (3 pts withdrew consent prior to evaluation and 1 missed > 10 days of treatment). One pt in cohort 3 had DLT related to grade 3 nausea and vomiting. A total of 19 grade 3 and 4 adverse events were records as probably or possibly associated with BYL719. The most common ones were hyperglycemia, anemia, and neutrophil count decreased. One pt developed Posterior reversible encephalopathy syndrome (PRES) during cycle 7. Although we could not completely exclude BYL719 as a cause, PRES was attributed to G. One pt had sudden death during cycle 4 that was attributed to progression. Only 8 pts were evaluable for response. Two had stable disease, 5 had partial responses and 1 had progression. The median progression-free survival and overall survival were 5.36 months (1.6 to 10 months) and 8.74 months (3.8 to 21.2 months) respectively. Conclusions: The combination of full doses of G + nabP and BYL719 can be safely administered up to BYL dose of 250 mg/day. Clinical trial information: NCT02155088. [Table: see text]

4016 Background: No standard treatment options are available for patients with advanced BC who fail gemcitabine/platinum therapy. The rationale for evaluation of trametinib was based on the presence of MAPK alterations and on earlier promising results with other MEK inhibitors in BC. Methods: Pts with histologically proven BC who progressed on gemcitabine/platinum were randomized to trametinib (2mg qd) (Arm A) vs infusional 5FU at 2400 mg/m2 over 46 hours or capecitabine (1000 mg/m2PO days 1-14 BID) (Arm B). Patients were stratified by planned chemotherapy 5FU/LV vs capecitabine; and disease site: cholangiocarcinoma vs gallbladder. The primary endpoint was overall survival (OS). Secondary endpoints included progression-free survival (PFS) and response rate (RR). 80 eligible patients (40 for each arm) were needed to detect an improvement in median OS from 5 months to 8.25 months (1.65 HR). A planned interim futility analysis of objective response was performed on the first 14 pts registered to the trametinib arm. Results: The study was stopped early based on the lack of measurable response in the trametinib arm. 53 pts were randomized (27 pts in Arm A vs 26 pts in Arm B). Median age was 62 years and the primary sites of tumor were cholangiocarcinoma (77%) and gallbladder (23%). Median OS was 4.3 months (95% CI 3.1-5.1) for Arm A, and 8.0 months (95% CI 3.2-14.6) for Arm B with a HR of 2.02 (95% CI 1.01-4.03, p=0.05). The median PFS was 1.3 months (95% CI 1.2-1.5) for arm A and 2.8 months (95% CI 1.4-6.9) for arm B with a HR of 2.95 (95% CI 1.38-6.30, p=0.01). Overall RR was 8% (95% CI 0%, 19%) in Arm A vs 10% (95% CI 0%, 23%) in Arm B (p>0.99), and 8% vs 45% had stable disease. Eight pts in Arm A experienced treatment-related ≥ grade 3 toxicities, including one death due to vomiting/dehydration. Seven pts in Arm B experienced treatment-related grade 3 toxicities; no higher grade toxicities were reported. Conclusions: To our knowledge, this is the first prospective randomized study of a targeted agent versus chemotherapy for the second line treatment of BC. In this unselected population, the lack of response to trametinib resulted in early closure. The PFS and OS for trametinib were inferior to 5FU. Clinical trial information: 02042443.