Vukovic, Vojislav

TPS1136 Background: Hsp90 is a molecular chaperone protein required for the stabilization and activation of many proteins, referred to as Hsp90 ‘clients’, including those commonly implicated in breast tumorigenesis such as HER2, EGFR, ER, PI3K, AKT, P53 and VEGFR. Ganetespib is a novel triazolone inhibitor of Hsp90 being studied in over 20 clinical trials, with over 700 patients treated to date. Ganetespib is ~50x more potent than 1st-generation Hsp90 inhibitors, and has been well tolerated in clinical trials with a favorable safety profile. Mild to moderate, transient diarrhea is the most common adverse event associated with ganetespib infusion and is manageable with appropriate supportive care. Ganetespib has shown activity in preclinical models of HER2+, ER+/PR+ and triple negative breast cancer (TNBC). In a phase I trial, ganetespib demonstrated single-agent clinical activity in HER2+ disease with an objective response rate (ORR) of 15% and a disease stabilization rate of 46% in heavily pretreated patients. This efficacy-screening study is designed to provide further evidence of ganetespib activity and identify potentially predictive biomarkers in metastatic breast cancer. Methods: The ENCHANT-1 trial is an international, first-line Phase II study in two cohorts of breast cancer patients: Cohort A, HER2 amplified (n=35), and Cohort B, TNBC (n=35). HER2+ patients must have received prior anti-HER2 therapy in the adjuvant setting. Patients are treated with ganetespib at 150 mg/m2 twice weekly on a three out of four-week regimen. Primary endpoint: ORR assessed using RECIST1.1 criteria. Key secondary endpoints include metabolic effects as assessed by PET/CT at week 3. Tumor genetic signature and proteomic profiling are performed on patient’s tumors in an effort to develop biomarkers of response. At the time of submission 6 patients have been enrolled into this study. Clinical trial information: NCT01677455.

3559 Background: A Phase 3 clinical trial (RECOURSE) showed that trifluridine/tipiracil (FTD/TPI) was effective in the treatment of refractory metastatic colorectal cancer (mCRC) treated with standard chemotherapy and targeted-therapy drugs (Mayer et al. N Engl J Med 2015;372:1909-19). An expanded-access program (EAP) was started to provide access to FTD/TPI for patients with mCRC with similar eligibility and to further assess the safety of FTD/TPI in a “real-world” setting in US patients. Methods: Patients aged ≥18 years with refractory mCRC resistant to ≥2 regimens of standard chemotherapy with appropriate biologics and an Eastern Cooperative Oncology Group performance status of 0 or 1 were enrolled to this open-label EAP. Patients received FTD/TPI 35 mg/m2twice daily for 5 days followed by 2 days’ rest repeated twice followed by 14 days’ rest over a 28-day treatment cycle until drug discontinuation. Sites reported duration of therapy, discontinuation due to disease progression, and adverse events (AEs) for each patient. Results: 549 patients were enrolled; 53.2% were male. Median duration of FTD/TPI therapy was 9.7 weeks, which was similar to US patients from RECOURSE (8.9). 10.2% of patients died during the study period, 9.7% due to disease progression. 76.1% of patients discontinued treatment due to disease progression and 4% discontinued due to AEs. Drug-related clinically significant AEs (all grades) are summarized in the table. Conclusions: Patients with refractory mCRC in this EAP had a similar exposure duration to that reported in US patients from RECOURSE, with no unexpected safety concerns. While gastrointestinal toxicity was lower in this population, this may be due to reporting of “significant” events. The clinical profile of FTD/TPI is confirmed in this larger, non-randomized “real-world” experience. Sponsorship: Taiho Oncology, Inc. Editorial Assistance: Complete HealthVizion. Clinical trial information: NCT02286492. [Table: see text]