Decrease Cancer Stem Cell Frequency Research Articles

Abstract A081: A phase 1b, open-label, dose escalation and expansion study of demcizumab plus pembrolizumab in patients with locally advanced or metastatic solid tumors

Abstract Introduction: Delta-like ligand 4 (DLL4) is a ligand that activates the Notch pathway. Demcizumab is a humanized, anti-DLL4 antibody that has been shown using an in vivo tumorigenicity limiting dilution assay to inhibit tumor growth and decrease cancer stem cell frequency in minimally passaged human xenograft models. In addition, inhibition of DLL4 has also been shown in preclinical studies to cause an antiangiogenic effect and to decrease the number of monocytic myeloid-derived suppressor cells (MDSCs) within the tumor. Finally, xenograft studies showed enhanced activity when demcizumab was combined with anti-PD1. Therefore, we hypothesized that demcizumab in combination with anti-PD1 may be effective in cancers that are refractory to anti-PD1 therapy and where MDSCs play a role in prognosis such as castrate-resistant prostate cancer and/or may augment the activity of anti-PD-1 in sensitive tumor types. Methods: This was an open-label, phase 1b dose study of demcizumab plus pembrolizumab in patients with advanced or metastatic solid tumors. Patients were enrolled in two stages: a dose-escalation stage and an expansion stage. In the dose escalation phase, patients received demcizumab 2.5 or 5 mg/kg administered IV once every 3 weeks for two 63-day truncated courses (second course starting on Day 168). Pembrolizumab was given at 2 mg/kg administered IV over 30 minutes every 3 weeks. Three cohorts of 10 patients each (anti-PD1 naïve 2L non-squamous NSCLC, anti-PD1 refractory, and advanced castrate-resistant prostate cancer) were planned to be enrolled in the dose escalation portion of the trial and treated with the MTD of demcizumab that was established in the dose escalation phase of the trial. Results: Twenty-seven patients were enrolled in the study: 9 in dose escalation and 18 in expansion. The MTD of demcizumab was determined to be 5 mg/kg (i.e., the highest dose tested). One partial response was observed in a NSCLC patient and 8 patients had stable disease. Peripheral MDSCs were measured over time in 5 of the prostate cancer patients, but no consistent impact was observed on the monocytic MDSCs. Demcizumab plus pembrolizumab was well tolerated. The most common adverse events were fatigue (44%), vomiting (41%), nausea (37%), headache (26%), BNP increased (22%), and decreased appetite (22%). Nine immune-related AEs occurred with only 2 being Grade 3 or greater. Conclusion: Demcizumab plus pembrolizumab therapy was well tolerated, but there was no evidence of enhanced antitumor activity. Citation Format: Melissa Johnson, Drew Rasco, Brian Schneider, Catherine Shu, Robert Jotte, Hema Parmer, Robert Stagg, Juanita Lopez. A phase 1b, open-label, dose escalation and expansion study of demcizumab plus pembrolizumab in patients with locally advanced or metastatic solid tumors [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A081.

Abstract A084: DENALI: a 3-arm double-blind randomized phase 2 study of carboplatin, pemetrexed, and placebo (CPP) versus carboplatin, pemetrexed, and either 1 or 2 truncated courses of demcizumab (CPD) in patients with non-squamous non-small cell lung cancer (NSCLC)

Abstract Introduction: Delta-like ligand 4 (DLL4) is a ligand that activates the Notch pathway, which is important for cancer stem cell (CSC) survival. Demcizumab is a humanized, anti-DLL4 antibody that has been shown using an in vivo tumorigenicity limiting dilution assay to inhibit tumor growth and decrease CSC frequency in minimally passaged human xenograft models. In addition, inhibition of DLL4 has also been shown in preclinical studies to cause dysfunctional sprouting of new vessels, resulting in an antiangiogenic effect. Data from a phase 1b study of carboplatin (C), pemetrexed (P), and demcizumab (D) in patients with 1st-line metastatic non-squamous NSCLC led to this double-blind randomized 3-arm placebo (Pl)-controlled phase 2 study. Methods: Patients with non-squamous NSCLC were randomized (1:1:1) to 1st-line therapy with either Arm 1 -CPPl, Arm 2 -CPD with a single 70-day truncated course of demcizumab or Arm 3 - CPD with two 70-day truncated courses of demcizumab (second course starting on Day 168). CP were given at usual dose and schedule; P/D was given IV on days 1 and 15 in cycles 1-3 and 7-9. The primary endpoint was response rate and secondary endpoints included progression-free survival, survival, safety, immunogenicity, pharmacokinetics, and biomarkers of Notch signaling and CSCs in blood, hair follicles, and tumor cells. The primary study analyses compared CPPl to the two pooled CPD arms. Results: 82 patients were randomized and all 82 were treated. The median age was 61, the male/female ratio was 40/42, 80 pts had adenocarcinoma, 0 pts harbored EGFR mutation or ALK rearrangement, and 15 were KRAS mutated. The response/clinical benefit rates were 52%/92% and 28%/79% in the CPPl and pooled CPD arms, respectively (response p value = 0.04). The median progression-free survival (PFS) was 8.7 months (95% CI: 5.4-12.5) in the CPPl arm and 5.5 months (95% CI: 4.1-6.9) in the pooled CPD arms (HR = 2.3; 95%CI: 1.1-4.8). The interim median overall survival (OS) for the CPPl and pooled CPD arms was not reached (95% CI: 16.0—NR) and 15.5 months (95% CI: 8.3-NR) (HR= 2.4; 95% CI: 0.94-6.1), respectively. CPD was generally well tolerated with nausea, fatigue, constipation, anemia, and hypertension being the most common reported toxicities. The incidences of the Grade 3 or greater toxicities of special interest with demcizumab therapy were hypertension (8% vs 25%), pulmonary hypertension (0% vs 0%), heart failure (0% vs. 0%), and bleeding (0% vs. 3.4%) in the CPPl and pooled CPD arms, respectively. Conclusions: The addition of either 1 or 2 truncated courses of demcizumab to 1st-line carboplatin and pemetrexed did not improve the efficacy compared to CPPl in patients with 1st-line metastatic NSCLC. CPD therapy was generally well tolerated. Citation Format: Brett Hughes, Andrew Dean, Ben Markman, Luke Dreisbach, Mariano Provencio, Libero Ciuffreda, Rachel Dear, Peter Graze, Alforia Nadal, Baerin Houghton, Teresa Moran, Rachel Roberts, Grace Dy, Taus Alvaro, Alex Martinez Marti, Rainer Brachmann, Robert Stagg, Ramaswamy Govindan. DENALI: a 3-arm double-blind randomized phase 2 study of carboplatin, pemetrexed, and placebo (CPP) versus carboplatin, pemetrexed, and either 1 or 2 truncated courses of demcizumab (CPD) in patients with non-squamous non-small cell lung cancer (NSCLC) [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A084.

Abstract A41: Use of patient-derived tumor xenografts (PDX) for discovery and development of an anti-Notch2/3 monoclonal antibody targeting cancer stem cells

Abstract Accumulating evidence has suggested that tumors may arise and grow as a result of the formation of a subset cell population termed cancer stem cells (CSC) or tumor initiating cells. Several research reports have indicated that CSCs are relatively resistant to conventional therapies. Thus, therapeutic strategies that specifically target cancer stem cells could have a major impact on cancer patient survival. Patient-derived tumor xenografts (PDX) have played a major role in the development of new cancer therapies. The advantage of PDX over standard cell-line xenograft models is that PDX retain much of the molecular, genetic, and histological heterogeneity of the original tumor and are minimally passed. In addition, self-renewal and lineage differentiation, the hallmarks of cancer stem cells, can be demonstrated through serial transplantation in immunodeficient mice. Our therapeutic approach in cancer stem cell drug discovery has been to target key developmental pathways that have been strongly implicated in cancer including the Notch pathway. We carried out tumorigenicity studies in three SCLC PDX models utilizing naïve cells positively enriched for either Notch2 or Notch3 expression. In two of the three models, Notch2+ and/or Notch3+ cell populations resulted in enhanced tumor formation. In a SCLC tumor that expressed low levels of Notch3, the Notch2+ population resulted in 70% tumor formation compared to CD44+ (10%) or CD133+ (45%) enriched populations. We have developed a monoclonal antibody, tarextumab (OMP-59R5), which selectively inhibits the function of both Notch2 and Notch3. Our preclinical data in PDX models demonstrate that tarextumab was efficacious in inhibiting the growth of various indications with minimal intestinal toxicity. Notably, the sensitivity of tarextumab in combination with gemcitabine or gemcitabine plus nab-paclitaxel in pancreatic tumors was associated with higher levels of Notch3 gene expression. Interference with Notch2/3 signaling by tarextumab delays tumor recurrence, decreases cancer stem cell frequency (as determined by in vivo LDA studies) and modulates the function of tumor vasculature. Our ALPINE Phase 1b clinical trial indicates that tarextumab is generally well-tolerated and shows signs of anti-tumor efficacy and modulation of Notch pathway signaling in the clinic. Furthermore, we observe a higher response rate and longer survival in patients with Notch3 high tumors receiving gemcitabine/nab-paclitaxel/tarextumab combination therapy. Analysis of pre- and post-treatment tumor biopsies showed an inhibition of Notch pathway and CSC gene signatures. Ongoing Phase 2 clinical trials evaluate first-line treatment with tarextumab in metastatic pancreatic cancer (ALPINE) and small cell lung cancer (PINNACLE). Collectively, these results demonstrate the utility of PDX models for discovery and development of anti-cancer stem cell therapeutics, identifying pharmacodynamic endpoints of drug actions, identifying predictive biomarkers for patient stratification, and translating these preclinical findings into clinical trials. Citation Format: Marcus M. Fischer, Wan-Ching Yen, Fumiko Axelrod, Christopher Bond, Jennifer Cain, Belinda Cancilla, Randall Henner, Rene Meisner, Aaron Sato, Jalpa Shaw, Tracy Tang, Breanna Wallace, Min Wang, Chun Zhang, Ann Kapoun, Lei Zhou, Jakob Dupont, John Lewicki, Austin Gurney, Tim Hoey. Use of patient-derived tumor xenografts (PDX) for discovery and development of an anti-Notch2/3 monoclonal antibody targeting cancer stem cells. [abstract]. In: Proceedings of the AACR Special Conference: Patient-Derived Cancer Models: Present and Future Applications from Basic Science to the Clinic; Feb 11-14, 2016; New Orleans, LA. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(16_Suppl):Abstract nr A41.

Abstract 4652: Effects of anti-DLL4 treatment on non-small cell lung cancer (NSCLC) human xenograft tumors

Abstract Background: Non-small cell lung cancer (NSCLC) accounts for the vast majority of lung cancers, the leading cause of cancer-related deaths. Notch signaling has been shown to play an important role in lung cancer initiation and progression. Delta-like ligand 4 (DLL4) activates the Notch pathway and is important for cancer stem cell (CSC) survival. Demcizumab (OMP-21M18) is a humanized IgG2 anti-DLL4 antibody currently being tested in a Phase 2 trial in combination with pemetrexed and carboplatin for first-line treatment of patients with NSCLC. Previously, OMP-21M18 in combination with its mouse anti-DLL4 surrogate has been shown to inhibit tumor growth, decrease cancer stem cell frequency, and cause dysfunctional sprouting of new vessels resulting in an anti-angiogenic effect in patient-derived tumor xenograft (PDX) models in breast, colon, ovarian, and pancreatic cancers. Here we show results from NSCLC PDX models. Methods and Results: Anti-DLL4 treatment was tested in a series of NSCLC PDX models. Because DLL4 inhibition has been shown to have effects on the tumor as well as the vasculature, the combination of OMP-21M18 (targeting human DLL4) and 21R30 (antibody targeting mouse DLL4) treatment in the PDX models was used to model demcizumab treatment in humans. Treatment with anti-DLL4 in combination with chemotherapy inhibited tumor growth in a series of NSCLC PDX models. Additionally, a tumorigenicity assay showed a decrease in the frequency of tumor-initiating cells following treatment with anti-DLL4 and chemotherapy. Gene expression analysis of tumor samples provided insights into the mechanism of action. Conclusions: Anti-DLL4 treatment in a panel of NSCLC PDX tumor models in vivo showed inhibition of tumor growth and a decrease in the frequency of tumor-initiating cells. Mechanism of action and gene expression analysis of these models treated with anti-DLL4 will be presented. These findings provide additional evidence supporting demcizumab as an effective treatment for NSCLC patients. Citation Format: Alayne Brunner, Fiore Cattaruzza, Wan-Ching Yen, Pete Yeung, Marcus Fischer, Belinda Cancilla, Gilbert O’Young, Raymond Tam, Yu-Wang Liu, Austin Gurney, John Lewicki, Tim Hoey, Min Wang, Ann M. Kapoun. Effects of anti-DLL4 treatment on non-small cell lung cancer (NSCLC) human xenograft tumors. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4652.

A phase 1b study of the anti-cancer stem cell agent demcizumab (DEM) and gemcitabine (GEM) +/- nab-paclitaxel in patients with pancreatic cancer.

341 Background: Delta-like ligand 4 (DLL4) activates the Notch pathway. DEM is a humanized anti-DLL4 antibody that inhibits tumor growth & decreases cancer stem cell frequency in human tumor xenograft models. DEM also has an antiangiogenic effect & synergistic activity when combined with GEM & nab-paclitaxel in pt derived xenograft models of pancreatic cancer. Methods: Pts with 1st line pancreatic cancer were enrolled. Pts in cohorts 1-3 received DEM (2.5 every 2 or 4 wks or 5 mg/kg every 4 wks including 3 truncated pts) & GEM 1000 mg/m2 7 of 8 wks, then 3 of 4 wks. Pts in cohorts 4, 5, 6 & 7 received truncated DEM (2.5, 3.5 or 5 mg/kg every 2 wks through Day 70) & nab-paclitaxel 125 mg/m2 + gemcitabine 1000 mg/m2 3 of 4 wks. The primary objective was to determine the MTD. Other objectives were safety, efficacy, immunogenicity, PK & biomarkers. Results: Fifty-six pts were enrolled; 8, 8, 8, 6, 8, 9 & 9 pts received 2.5 mg/kg every 2 wks, 2.5 mg/kg every 4 wks, 5 mg/kg every 4 wks, 2.5 mg/kg every 2 wks (truncated), 5 mg/kg every 2 wks (truncated), 3.5 mg/kg every 2 wks (truncated) & 3.5 mg/kg every 2 wks (truncated), respectively. Related AEs in > 20% of pts were fatigue (36%), nausea (32%), vomiting (23%), hypertension (21%) & diarrhea (20%). Hypertension was managed with anti-hypertensives. Increased BNP is an early indicator of the cardiac effects of DEM & mildly elevated values were used to initiate a cardioprotective ACE inhibitor or carvedilol. Two pts who received DEM continuously developed reversible pulmonary hypertension & 1 of these pts developed heart failure. As a result, DEM was limited to 70 days in cohorts 4, 5, 6 & 7. In cohorts 1-3, 4 of 16 (25%) pts had a PR. In cohorts 4, 5, 6 & 7, 14 of 28 (50%) pts had a PR & 11 had SD. The truncated DEM pts had a median PFS of 9.0 mos (95% CI: 3.7 mos-NR) & a median survival of 10.1 mos (95% CI: 6.5-16.2 mos), respectively. Conclusions: This therapy was generally well tolerated with fatigue, nausea & vomiting being the most common related AEs. Truncated DEM dosing (i.e., limited to 70 days) avoided clinically significant cardiopulmonary toxicity. Encouraging clinical activity was observed. Biomarker analysis showed modulation of the Notch pathway. Final data will be presented. Clinical trial information: NCT01189929.

A phase Ib study of the anti-cancer stem cell agent demcizumab (DEM) & gemcitabine (GEM) +/- paclitaxel protein bound particles (nab-paclitaxel) in pts with pancreatic cancer.

4118 Background: Delta-like ligand 4 (DLL4) activates the Notch pathway. DEM is a humanized IgG2anti-DLL4 antibody that inhibits tumor growth & decreases cancer stem cell frequency in human tumor x...

616PD - A Ph 1B Study of the Anti-Cancer Stem Cell Agent Demcizumab (Dem) & Gemcitabine (Gem) +/- Paclitaxel Protein Bound Particles (Nab-Paclitaxel) in Pts with Pancreatic Cancer

ABSTRACT Aim: Delta-like ligand 4 (DLL4) is a ligand that activates the Notch pathway. DEM is a humanized IgG2 anti-DLL4 antibody that inhibits tumor growth & decreases cancer stem cell frequency in minimally passaged human xenograft models. In addition, DEM has an antiangiogenic effect & synergistic activity when combined with GEM & nab-paclitaxel in human pancreatic tumor-derived xenograft models. Methods: Pts with 1st line pancreatic cancer were enrolled. Pts in cohorts 1-3 received DEM (2.5 every 2 or 4 wks or 5 mg/kg every 4 wks including 3 truncated pts) & GEM 1000 mg/m2 7 of 8 wks, then 3 of 4 wks. Pts in cohorts 4 & 5 received truncated DEM (2.5 or 5 mg/kg every 2 wks through Day 70) & nab-paclitaxel 125 mg/m2 + gemcitabine 1000 mg/m2 3 of 4 weeks. The primary objective was to determine the MTD. Other objectives were safety, efficacy, immunogenicity, PK & biomarkers. Results: Thirty-eight pts were enrolled; 8, 8, 8, 6 & 8 pts received 2.5 mg/kg every 2 wks, 2.5 mg/kg every 4 wks, 5 mg/kg every 4 wks, 2.5 mg/kg every 2 weeks (truncated) & 5 mg/kg every 2 weeks (truncated), respectively. Related AEs in > 20% of pts were nausea (37%), fatigue (34%), nausea, vomiting (32%), decreased appetite (24%) & hypertension (21%). Hypertension was managed with anti-hypertensives. Increased BNP is an early indicator of the cardiac effects of DEM & mildly elevated values are used to initiate cardioprotective therapy with an ACE inhibitor or carvedilol. One pt who received 5 mg/kg continuously developed reversible pulmonary hypertension & heart failure on day 143. As a result, DEM was limited to 70 days in cohorts 4 & 5. In cohorts 1-3, 4 of 16 (25%) pts had a partial response (PR) & 7 had stable disease (SD). In cohorts 4 & 5, 6 of 14 (43%) pts had a PR & 6 had SD. The median PFS for 2.5 & 5 mg/kg every 4 wks and 2.5 mg/kg, 2.5 mg/kg (truncated) & 5 mg/kg (truncated) every 2 wks were 1.7, 7, 3.4, not reached and 3.5 mos., respectively. The 3 truncated pts in cohort 3 had PFS of 5.4, 7 and 9.1 mos. Conclusions: This therapy was generally well tolerated with fatigue, nausea & vomiting being the most common related AEs. Encouraging early clinical activity was observed. Additional data with truncated DEM will be presented. Disclosure: R. Stagg and J. Dupont: I am an employee of OncoMed and own stock in the company. All other authors have declared no conflicts of interest.

A Phase 1B Study of the Anti-Cancer Stem Cell Agent Demcizumab (Dem), Pemetrexed (Pem) & Carboplatin (Carbo) in Pts with 1St Line Non-Squamous Nsclc

ABSTRACT Aim: Delta-like ligand 4 (DLL4) activates the Notch pathway and is important for cancer stem cell (CSC) survival. DEM is a humanized IgG2 anti-DLL4 antibody that has been shown to inhibit tumor growth, decrease CSC frequency & cause dysfunctional sprouting of new vessels resulting in an antiangiogenic effect in human tumor xenograft models. Methods: Pts received DEM (2.5 or 5 mg/kg), PEM 500 mg/m2 & CARBO (AUC = 6) every 3 wks X 6 cycles followed by maintenance DEM (cohorts 1-4) or truncated DEM (5 or 7.5 mg/kg), PEM 500 mg/m2 & CARBO (AUC = 6) every 3 wks X 4 cycles followed by maintenance PEM (cohorts 5 & 6). The objectives were to determine the MTD, safety, efficacy, immunogenicity, pharmacokinetics & biomarkers of Notch signaling. Results: Thirty-nine pts were enrolled; 6 received 2.5 mg/kg, 20 received 5 mg/kg, 6 received 7.5 mg/kg of truncated DEM & 7 received 5 mg/kg of truncated DEM. Related AEs in > 20% of pts were: nausea (49%), fatigue (44%), hypertension (41%), vomiting (31%), edema (26%), neutropenia (26%), & increased B-type natriuretic peptide (BNP) (23%). Increased BNP values are an early indicator of the cardiac effects of DEM & mildly elevated values are being used to initiate cardioprotective therapy with an ACE inhibitor or carvedilol. Two pts receiving 5 mg/kg developed reversible pulmonary hypertension & heart failure on days 167 & 183, respectively. As a result, DEM treatment was limited to 63 days in cohorts 5 & 6. One of 32 (3%) evaluable pts had a RECIST CR, 13 (41%) had a PR and 14 had SD. The Kaplan Meier estimated median progression free survivals for the 2.5, 5, truncated 5 & truncated 7.5 mg/kg pts were 4.3, 5.3, not yet reached & 4.4 months, respectively. Five pts who discontinued the study for a reason other than progression (3 continued to receive CARBO & PEM off-study) were progression-free through Days 223 + , 243 + , 457 + , 497 + , 680+ and a sixth pt (who continued to receive CARBO & PEM off-study) progressed at Day 850. Conclusions: This therapy was generally well tolerated with nausea, fatigue & hypertension being the most common drug related toxicities. Encouraging early clinical activity has been observed. Additional data with truncated DEM will be presented. Disclosure: R. Stagg: I am an employee of OncoMed and I own stock in the company; J. Dupont: I work for OncoMed and own stock in the company. All other authors have declared no conflicts of interest.

Abstract B78: A Phase Ib study of demcizumab (DEM, anti-DLL4) with gemcitabine (GEM) in patients with first line locally advanced or metastatic pancreatic cancer.

Abstract Background: Delta-like ligand 4 (DLL4) is a ligand that activates the Notch pathway which is important for cancer stem cell (CSC) survival. DEM is a humanized IgG2 anti-DLL4 antibody that has been shown to inhibit tumor growth and decrease CSC frequency in minimally passaged human xenograft models. In addition, inhibition of DLL4 has also been shown in preclinical studies to cause dysfunctional sprouting of new vessels resulting in an antiangiogenic effect. DEM also showed synergistic activity when combined with GEM in human pancreatic tumor-derived xenograft models. Material and Methods: Patients with first line stage III or IV pancreatic cancer received DEM (2.5 every 2 or 4 wks or 5 mg/kg every 4 wks) and GEM 1000 mg/m2 7 of the 1st 8 wks and then 3 of every 4 wks until disease progression. The primary objective was to determine the maximum tolerated dose of DEM. Other objectives included: safety, efficacy, immunogenicity, pharmacokinetic, and biomarkers of Notch signaling and CSCs. Results: Twenty four patients were enrolled; 8 pts received 2.5 mg/kg every 2 wks, 8 received 2.5 mg/kg every 4 wks and 8 received 5 mg/kg every 4 wks of DEM. The median age was 65.5 yrs. Three (12.5%) and 21 (87.5%) patients had stage III and IV disease, respectively. Seven, 16 and 1 patients were ECOG performance status 0, 1, and 2, respectively. Related adverse events (all grades) in ≥10% of patients included: fatigue (29%), hypertension (29%), vomiting (29%), nausea (25%), thrombocytopenia (21%), decreased appetite (21%), increased B-type natriuretic peptide (BNP) (13%), anemia (13%), peripheral edema (13%), pulmonary hypertension (13%), dizziness (13%) and rash (13%). The hypertension was successfully managed with oral anti-hypertensives. Increased BNP values appear to be an early indicator of the cardiac effects of DEM and mildly elevated values are being used to initiate cardioprotective therapy with an ACE inhibitor or carvedilol. One patient who received 5 mg/kg developed reversible pulmonary hypertension and heart failure on study day 143. As a result, the duration of DEM will be limited to 70 days in subsequent cohorts and paclitaxel protein-bound particles will also be added to the regimen. Four of 16 (25%) evaluable patients had a RECIST partial response and 7 had stable disease. The median progression free survival for the 5 mg/kg cohort was 5.9 months. The pharmacokinetic and immunogenicity samples are being analyzed and these data will be presented. Conclusion: DEM plus GEM was generally well tolerated with fatigue, hypertension and vomiting being the most common drug related adverse events. The duration of demcizumab therapy is being limited to 70 days in subsequent cohorts due to cardiopulmonary toxicity which was observed following more prolonged administration. Encouraging early clinical activity has been observed. Subsequent cohorts will include paclitaxel protein-bound particles. Enrollment is ongoing and updated results will be presented. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B78. Citation Format: Antonio Cubillo, Michael Jameson, Enrique Grande, Francis Parnis, Peter Grimison, Prasad Cooray, Mark Jeffery, Robert Stagg, Jakob Dupont, Niall Tebbutt. A Phase Ib study of demcizumab (DEM, anti-DLL4) with gemcitabine (GEM) in patients with first line locally advanced or metastatic pancreatic cancer. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B78.

Abstract A71: A Phase Ib study of demcizumab (DEM, anti-DLL4) plus pemetrexed and carboplatin in patients with first line stage IIIb/IV non-squamous non-small cell lung cancer.

Abstract Background: Delta-like ligand 4 (DLL4) is a ligand that activates the Notch pathway which is important for cancer stem cell (CSC) survival. DEM is a humanized IgG2 anti-DLL4 antibody that has been shown to inhibit tumor growth and decrease CSC frequency in minimally passaged human xenograft models. In addition, inhibition of DLL4 has also been shown in preclinical studies to cause dysfunctional sprouting of new vessels resulting in an antiangiogenic effect. Material and Methods: Patients received DEM (2.5, 5, or 7.5 mg/kg), pemetrexed 500 mg/m2, and carboplatin (AUC = 6) every 3 weeks followed by maintenance DEM (first 4 cohorts) or pemetrexed (7.5 mg/kg cohort) every 3 weeks until disease progression. Folic acid, vitamin B12 and dexamethasone were administered as pemetrexed pre-medication. The primary study objective was to determine the maximum tolerated dose of DEM. Other objectives included: safety, efficacy, immunogenicity, pharmacokinetic and biomarkers of Notch signaling. Results: Thirty patients have been enrolled; 6 received 2.5 mg/kg, 20 received 5 mg/kg and 4 received 7.5 mg/kg of DEM once every 3 weeks. The median age was 63 years and 90% had stage IV disease. Related adverse events (all grades) in ≥10% of pts included: nausea (53%), fatigue (50%), hypertension (37%), vomiting (33%), neutropenia (27%), increased B-type natriuretic peptide (BNP) (23%), anemia (20%), peripheral edema (20%), increased ALT (20%), increased AST (17%), dyspnea, (17%), diarrhea (17%), decreased appetite (17%), pulmonary hypertension (13%), dysgeusia (13%), thrombocytopenia (13%), constipation (10%), and rash (10%). The hypertension was managed with oral anti-hypertensives. Increased BNP values appear to be an early indicator of the cardiac effects of DEM and mildly elevated values are being used to initiate cardioprotective therapy with an ACE inhibitor or carvedilol. Two patients receiving 5 mg/kg developed reversible pulmonary hypertension and heart failure on days 167 and 183, respectively. As a result, the duration of DEM was limited to 63 days in the 7.5 mg/kg dose cohort. The pharmacokinetics and immunogenicity specimens are being analyzed and these data will be presented. Nine of the 23 (39%) evaluable patients had a RECIST partial response and 11 had stable disease. The median progression free survival for the 5 mg/kg cohort was 5.3 months. Conclusion: DEM, pemetrexed and carboplatin was generally well tolerated with nausea, fatigue and hypertension being the most common drug related toxicities. The duration of demcizumab therapy is being limited to 63 days in subsequent cohorts due to cardiopulmonary toxicity which was observed following more prolonged administration. Encouraging early clinical activity has been observed. Enrollment is ongoing and updated results will be presented. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A71. Citation Format: Mark McKeage, Dusan Kotasek, Ben Markman, Michael Millward, Manuel Hildalgo, Michael Jameson, Dean Harris, Robert Stagg, Jakob Dupont, Brett Hughes. A Phase Ib study of demcizumab (DEM, anti-DLL4) plus pemetrexed and carboplatin in patients with first line stage IIIb/IV non-squamous non-small cell lung cancer. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A71.

Abstract 3357: Targeting cancer stem cells by an anti-DLL4 antibody inhibits epithelial-to-mesenchymal transition, delays tumor recurrence and overcomes drug resistance in breast and pancreatic cancer

Abstract Accumulating evidence suggests that tumor growth, recurrence and metastasis are driven by a subset of highly tumorigenic cells referred to as cancer stem cells (CSCs) or tumor initiating cells. Several investigators have demonstrated that CSCs are relatively resistant to chemotherapy and that tumor recurrence and the development of drug resistance after chemotherapy are mediated by residual cancer stem cells. Furthermore, it has been demonstrated that the process of epithelial-to-mesenchymal transition (EMT) contributes to drug resistance and results in cells with CSC-like characteristics. We previously demonstrated that targeting Notch signaling pathway by a novel anti-DLL4 antibody inhibited tumor growth and decreased cancer stem cell frequency. Using patient-derived breast cancer and pancreatic cancer xenograft tumors we found that residual tumors after conventional chemotherapy (paclitaxel for breast cancer and gemcitabine for pancreatic cancer) were enriched with cancer stem cells. Gene expression analysis of cell populations enriched for CSCs revealed that several mesenchymal-associated genes were up-regulated, whereas epithelial gene was down-regulated. As shown by in vivo limiting dilution analyses, treatment with anti-DLL4 antibody decreased cancer stem cell frequency. Anti-DLL4 reversed chemotherapy-induced mesenchymal gene expression and delayed tumor recurrence. The residual tumor cells treated with conventional therapy eventually developed acquired drug resistance following repeated treatment. Compared to the parental xenograft, the resistant tumors had increased cancer stem cell frequency and tumorigenic ability. Treatment with anti-DLL4 antibody inhibited growth of these resistant tumors and re-sensitized them to the chemotherapeutic agent. This effect was in part due to the ability of the antibody to decrease cancer stem cell frequency in resistant tumors. The combination of antibody and chemotherapeutic agent further decreased cancer stem cell frequency compared to the parental tumor. Gene expression analysis demonstrated that resistant tumors had increased expression of many genes associated with EMT, multidrug resistance, DNA repair, and the Notch and Wnt pathways. Importantly, treatment with anti-DLL4 suppressed many gene expression changes in chemo-resistant tumors and resulted in a gene expression profile more like the original (drug sensitive) tumor. Immunohistochemical analysis indicated that anti-DLL4 mediated anti-tumor effect was associated with inhibition of EMT and induction of differentiation markers. Our findings provide a rationale to target cancer stem cells through interference with Notch pathway as a therapeutic approach in patients who are refractory to chemotherapeutic agents. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3357. doi:1538-7445.AM2012-3357