Citations

4018 Background: BTCs are often diagnosed at an advanced stage and have a poor prognosis. The standard therapy for aBTCs is the combination of GC. However, the median overall survival (mOS) is dismal at 11.7 months (mos) with a median progression free survival (mPFS) of 8 mos. Methods: A single arm, phase II study was conducted at MD Anderson and Mayo Clinic Arizona. Patients (pts) with aBTC were treated at initial dose level of G/C/N (in mg/m2) at 1000/25/125 (n = 27) which was reduced to lower doses due to grade 3/4 hematological (heme) toxicity (tox) - G/C/N: 800/25/100 (n = 33). Cycles were q21 days with restaging q3 cycles until progression. PFS was the primary endpoint (endpt). Using a Bayesian hypothesis test-based design, we assumed mPFS of 8 mos under the null hypothesis (H0), 10 mos under the alternative (H1). Secondary endpts included mOS, RECIST v1.1 response rate (RR), safety and CA19-9 response. Results: 60 pts were enrolled with data on 51 available as of the time of this abstract (age: median 60 yrs [range 31-77], ECOG PS 0/1 (17/34), M/F (30/21), intrahepatic cholangiocarcinoma/extrahepatic/gallbladder (32/8/11). Median follow-up was 11.5 mos and median number of treatment (trmt) cycles = 5. Pts at initial dose level had significant grade 3/4 heme tox: neutropenia, febrile neutropenia, anemia, and thrombocytopenia leading to trmt discontinuation in 6/27 pts. After dose reduction to G/C/N (in mg/m2) at 800/25/100, trmt was better tolerated with only 4 pts experiencing grade 4 heme tox. Non-heme tox were grade 3 in 10 pts: nausea/vomiting, diarrhea, thromboembolic event/CVA, hypokalemia, constipation, cystitis, LFT elevations. In the initial 51 pts, mPFS = 11.4 mos (95% CI: 6.1, not reached) and mOS not reached (estimated > 20 mos, 1-year survival rate 66.7%; 95%CI: 65.9-92.2%). 34 pts evaluable for response: disease control rate (PR+CR+SD)-82.3% and RR-32.3%. 3 unresectable cases were operated post trmt with 1 pathologic CR. Conclusions: The combination of GCN was well tolerated at adjusted doses and demonstrates encouraging preliminary efficacy having met its mPFS endpt and a 1-year survival rate higher than historical control. These results merit evaluating GC +/-N in a randomized controlled study. Clinical trial information: NCT02392637.

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.

TPS4148 Background: Cancer stem cells are considered to be fundamentally important for resistance to therapy, recurrence and metastasis. Napabucasin is a first-in-class cancer stemness inhibitor identified by its ability to inhibit STAT3-driven gene transcription and spherogenesis of cancer stem cells (Li et al, PNAS 112(6):1839, 2015). Preclinical studies suggest that napabucasin sensitizes heterogeneous cancer cells to chemotherapeutic agents, including nab-PTX and gem. Encouraging anticancer activity in mPDAC was observed in a phase Ib (El-Rayes et al, ASCO 2016) study of 37 pts, reporting 93% (28/30) disease control rate (DCR) and 50% (15/30) overall response rate (ORR), with 1 complete and 14 partial responses and prolonged disease control ( > 24 wks) in 57% (17/30) of pts who have had a RECIST evaluation. On the basis of these data, a phase III trial is being conducted in North America, Europe, Australia and Asia. Methods: This study (ClinicalTrials.gov NCT02993731) will assess the efficacy of napabucasin+nab-PTX+gem vs nab-PTX+gem in pts with mPDAC (n = 1132). Pts must have been diagnosed with mPDAC < 6 weeks prior to randomization and not have received treatment for metastatic disease. Pts are randomized in a 1:1 ratio to receive napabucasin 240 mg PO twice daily continuously plus nab-PTX+gem IV weekly for 3 out every 4 weeks, or nab-PTX+gem IV weekly for 3 out every 4 weeks. Pts will be stratified by geography, performance status and presence of liver metastases. Treatment will continue until disease progression, death, intolerability or patient/investigator decision to stop. Primary endpoint is overall survival (OS) in the general study population (HR 0.80 for OS improvement from 8.5 to 10.63 months); secondary endpoints include progression free survival (PFS), OS and PFS in the biomarker positive sub-population, ORR and DCR, safety and quality of life. In addition, blood and tumor archival tissue will be assessed for pharmacokinetic and biomarker analyses. Global enrollment is underway. Clinical trial information: NCT02993731.

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

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

3541 Background: Pembrolizumab (PEM) has activity in patients with deficient mismatch repair (dMMR) colorectal cancer (CRC). Oxaliplatin (OX) and 5FU lead to immunogenic cell death and increased antigen presentation. We hypothesized that combining mFOLFOX6 and PEM may enhance immunogenic cell death and improve outcome in patients with CRC irrespective of MMR status. Methods: Subjects ≥18 years old with untreated, unresectable CRC were assigned to a single arm study. The study had a safety run in cohort of six patients (OX 85 mg/m2, leucovorin 400 mg/m2, 5FU 400 mg/m2, 5FU infusion 2400 mg/m2over 46 hours) and PEM 200 mg Q 3 weeks, followed by a phase II cohort. The primary objective was median progression free survival (mPFS), with secondary objectives: safety and toxicity per CTCAE V4.03, median overall survival, response rate, immune related response, disease control rate, and molecular correlates. Results: Between 4/2015 and 9/2016, 30 subjects were enrolled with following characteristics: 11 female, 26 Caucasian, median age: 45 years (25-75), 3 with dMMR, 22 MMR-proficient, and 5 with no available data. During the safety run in, 2 patients had G3 febrile neutropenia (FN) and 1 G4 neutropenia. The data safety monitoring committee recommended dose reduction of mFOLFOX6 to OX 68 mg/m2, leucovorin 400 mg/m2, 5FU of 320 mg/m2, 5FU infusion of 1920 mg/m2over 46 hours and PEM 200 mg Q 3 weeks. At the data cut off (12/29/16), median follow up was 24 weeks (10-66) and 27 patients remained on study. Rate of G3/4 toxicity associated with FOLFOX/PEM and PEM alone was 36.7% and 13.2%, respectively. No further FN was observed. No grade 5 toxicity was seen on study. Best response was recorded as: 1 complete response, 15 partial response (CR +PR = 53%), and 14 stable disease, with 100% DCR at 8 weeks. One patient with dMMR had resection after 2 months of therapy with complete pathologic response. MPFS has not been reached (95% CI: 5.5 months, NR). Conclusions: Based on these preliminary results, PEM/mFOLFOX6 has acceptable toxicity though demonstrated a suggestion of increased neutropenia in the initial cohort. Clinical activity was seen in patients with untreated advanced CRC including those with proficient MMR. Clinical trial information: NCT02375672.