Li, Youzhi

4106 Background: Cancer stem cells are fundamentally important for resistance to therapy, recurrence and metastasis. Napabucasin is a first-in-class cancer stemness inhibitor in development 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 chemotherapy and targeted agents. Methods: A phase Ib/II multi-center study in mPDAC pts was performed to confirm the RP2D, PK profile and evidence of anticancer activity of napabucasin in combination with nabPTX and Gem. Pts received napabucasin 240 mg BID with weekly nabPTX 125 mg/m2 and gem 1000 mg/m2for 3 out of every 4 weeks until disease progression (PD) or other discontinuation criterion. Results: Of 71 intent to treat (ITT) pts enrolled, 49 (69%) were treatment-naïve and 22 (31%) received neoadjuvant treatment. There were no significant PK interactions, dose-limiting or unexpected toxicities. Most common adverse events (AEs) included grade 1 diarrhea/cramping, nausea and fatigue with grade 3 AEs noted in 12 pts: fatigue (8), electrolyte imbalance (2), diarrhea (1), dehydration (1), nausea (1) and weight loss (1). Among pts who received RECIST evaluation (60), disease control (DCR; CR+PR+SD) was observed in 55 (92%), with 1 CR (2%) and 26 PR (43%) (31 - 78% regression). Of 11 pts with non-evaluable disease, treatment stopped due to compliance (4), consent withdrawal (3), clinical PD (1), toxicity (1), insurance (1) and death (1). Among 71 ITT pts, DCR was observed in 55 (77%), with 1 CR (1.4%) and 26 PR (37%). Maturing median progression free survival and overall survival (OS) in ITT pts is >7.1 and >10.4 m, respectively. Conclusions: This study showed that napabucasin can be combined with nabPTX and gem, with encouraging signs of efficacy in mPDAC now being confirmed in a phase 3 study. Clinical trial information: NCT02231723. [Table: see text]

3529 Background: Cancer stem cells are considered to be fundamentally important for resistance, recurrence and metastasis. Napabucasin is a first-in-class cancer stemness inhibitor in development identified by its ability to inhibit STAT3-driven gene transcription and spherogenesis of cancer stem cells (Li et al, PNAS 112(6):1839, 2015). Preclinically, napabucasin sensitizes cancer cells to chemotherapy and targeted agents. Methods: A phase Ib/II multi-center study in mCRC pts was done to confirm the RP2D and signs of anti-cancer activity of napabucasin in combination with FOLFIRI +/- Bev. Pts received napabucasin 240 mg PO BID with bi-weekly FOLFIRI IV +/- Bev 5 mg/kg until disease progression or other discontinuation criterion. Results: 82 pretreated mCRC pts were enrolled (ITT); including 32 (39%) previously treated with FOLFIRI +/- bev. Of the 82 pts, 48 received FOLFIRI and 34 FOLFIRI plus bev in combination with napabucasin. There was no dose-limiting or unexpected toxicity or significant PK interactions. Most common adverse events (AEs) included grade 1/2 diarrhea, cramping, nausea, vomiting, fatigue and anorexia with grade 4 diarrhea in 1 pt and 27 pts with grade 3 AEs including: diarrhea (15), fatigue (5), dehydration (1), electrolyte imbalance (4), abdominal pain (1), vomiting (1) and weight loss (1), which resolved with dose reduction and supportive care. Disease control (CR+PR+SD) was observed in 55 of 66 pts who received RECIST evaluation (83%), with 1 CR (1.5%), 13 PR (20%) (33-100% regression) and 27 SD with tumor regression (41%). Conclusions: This phase Ib/II study confirmed that napabucasin can be safely combined with FOLFIRI +/- bev, and shows encouraging signs of efficacy in pretreated mCRC pts, including pts previously treated with FOLFIRI +/- bev. Clinical trial information: NCT02024607. [Table: see text]

677 Background: Napabucasin a first-in-class cancer stemness inhibitor in clinical development, suppresses cancer stemness by targeting Stat3-driven gene transcription. Preclinically, potent and broad-spectrum anti-cancer activity was observed in vitro and in vivo, alone and in combination with other agents. In a phase 1 study, napabucasin monotherapy was well tolerated with encouraging signs of anti-tumor activity at the RP2D of 500 mg BID. Methods: The current open-label, multi-center study includes phase II expansion in pts with refractory, K- Raswt mCRC to confirm safety and anti-tumor activity of napabucasin administered orally at 480mg BID in combination with panitumumab (6mg/kg bi-weekly). Results: 72 pts were enrolled, 48 pts were evaluable by RECIST of which 7 (15%) and 41 (85%) had 2 or >3 prior treatment lines, respectively. Of the 48 evaluable pts, 64.6% (31/48) were previously treated with an anti-EGFR agent. No new adverse events (AEs) were observed and most common AEs included grade 1/2 diarrhea, nausea, abdominal cramps, and vomiting. Among 48 pts enrolled who received RECIST evaluation, Disease Control Rate (DCR) was observed in 25 pts (52.1%) of which 3 pts achieved PR (6%) and 22 pts achieved SD (45%). Among 31 pts previously treated with anti-EGFR therapy, DCR was observed in 15 pts (48%) compared with DCR of 59% observed in 10 out of 17 anti-EGFR naïve pts receiving a scan. Conclusions: This phase II study confirmed that napabucasin can be safely combined with panitumumab at full dose and shows encouraging anti-tumor activity in pts with K- Ras wt mCRC, regardless of prior anti-EGFR exposure, suggesting that napabucasin may sensitize pts to repeat anti-EGFR therapy. Clinical trial information: NCT01776307. [Table: see text]