1. Improving Patient Outcomes by Targeting the VEGF/VEGFR Axis
Wells Messersmith, MD, FACP
Professor
Director, Gastrointestinal Medical Oncology Program
Co-Head, Division of Medical Oncology
Program co-Leader, Developmental Therapeutics
May 2013

2. Conflict of Interest:
No employment, speaker’s bureaus, stock ownership, royalties, patents, etc
Data Safety Monitoring Board for Morphotek
Local PI of clinical trials by Genentech/Roche, GSK, AstraZeneca, EntreMed, Pfizer, Millenium, Bayer, Onconova, and NIH/CTEP.
Slides: S. Kopetz (MDACC), Chris Lieu (Colorado)

3. Angiogenesis Outline/Objectives: Introduction Role of PlGF
a. Angiogenesis
b. Ongoing trials in GI cancers
Role of PlGF
Mechanisms of resistance

4. Angiogenesis Background
Observation that tumor growth can be accompanied by increased vascularity was reported more than a century ago
In 1939, Ide and colleagues first postulated the existence of a tumor-derived blood-vessel-growth stimulating factor
In 1960s, experiments by Greenblatt and Shubik, and Ehrmann and Knoth, provided early evidence that tumor angiogenesis was mediated by diffusible factors produced by tumor cells
In 1971, Folkman proposed that anti-angiogenesis might be an effective anticancer strategy
C. Lieu, Colorado

5. VEGF
VEGF family of growth factors and their receptor tyrosine kinases mediate proangiogenic effects
Normal endothelial cells engaged in angiogenesis express numerous VEGF receptors, but produce very little detectable VEGF
Tumor cells express VEGF receptors and also produce VEGF (autocrine mechanisms)
Classic signaling is via VEGF-A binding to VEGFR-2, stimulating the PI3K/Akt as well as Raf/MEK/MAPK pathways

6. VEGF Signaling
Kerbel R. N Engl J Med 2008;358:

7. Large Molecule VEGF Inhibitors
VEGF-A
VEGF-R1
(Flt-1)
Migration
Invasion
Survival
VEGF-R3
(Flt-4)
Lymphangiogenesis
VEGF-R2
(KDR/Flk-1)
Proliferation
Permeability
PlGF
VEGF-B
VEGF-C,
VEGF-D
Functions Y
Bevacizumab Y
Ramucirumab
Aflibercept
(VEGF Trap)
PIGF = placental growth factor.
Holash et al, 2002; Roy et al, 2006; Ghosh et al, 2000.

8. Proposed Mechanism of Anti-Angiogenics
Inhibition of new vessel growth and vascular regression
Vascular normalization
Vascular constriction
Direct effects on tumor cell function
Offsetting effects of chemotherapy inducing VEGF levels

9. (selected anti-angiogenic agents)
Phase III’s
(selected anti-angiogenic agents)
Colorectal
Recently reported:
Regorafenib (“CORRECT”) – positive
Aflibercept (“VELOUR”) – positive
Bevacizumab 2nd line (“TML”) – positive
Brivinib (with cetux) – negative
Ongoing
Ramucirumab (VEGFR-2 mAb; “RAISE”): NCT

10. Track Record of TKI’s in Colorectal
Total > 10,000
Kopetz, MDACC

11. Track Record of TKI’s in Colorectal
Agent
FOLFOX
Irinotecan FOLFIRI
EGFRi + chemo
Other
Sunitinib
Phase IIB
Phase III
Phase I/II
Vandetanib
Phase I
Cediranib
Phase II/III
Vatalanib
Phase IIIs
Axitinib
Bevacizumab
Semaxinib
5-FU, phase III
Motesanib
Sorafenib
Pazopanib
Brivanib
Cetux, Phase III
Regorafenib
Phase II
Linifanib
Positive
Negative
Ongoing

12. Track Record of TKI’s in Colorectal
Kopetz, MDACC

13. (selected anti-angiogenic agents)
Phase III’s
(selected anti-angiogenic agents)
Pancreas Cancer
Gem +/- sorafenib “BYPAN” (NCT ) - negative
Gem +/- bevacizumab (CALGB 80303) - negative
Gem +/- Aflibercept (“VANILLA”) - negative
Gem +/- axitinib (NCT ) – negative
Gastro-esophageal
Bevacizumab (“AVAGAST”) – negative (overall population)
Ramucirumab (VEGFR-2) vs BSC – positive
Pancreas Islet Cell / Carcinoid
Sunitinib (NCT ) – positive
Bev vs Interferon, SWOG 0518 (NCT )

14. (selected anti-angiogenic agents)
Phase III’s
(selected anti-angiogenic agents)
HCC
1st Line
Sorafenib (“SHARP”) – positive
Doxorubicin/Sorafenib vs S, CALGB (NCT )
Sorafenib vs brivanib (“BRISK FL”) – negative
Sorafenib vs sunitinib (NCT ) – negative
Sorafenib vs linifanib (ABT-869) (NCT )
2nd Line
Brivanib vs BSC (“BRISK PS”) (NCT ) – terminated
Ramucirumab vs BSC (“REACH”) (NCT )

15. Angiogenesis Outline/Objectives: Introduction Role of PlGF
a. Angiogenesis
b. Ongoing trials in GI cancers
Role of PlGF
Mechanisms of resistance

16. Role of Placenta Growth Factor
Angiogenic protein in VEGF family involved in cancer, inflammation, pre-eclampsia, cardiovascular disease
Unlike VEGF, PlGF is undetectable in healthy tissues; upregulated in tumors
Contributes to angiogenic and inflammatory “switch”
Produced by malignant cells, endothelial cells, smooth-muscle cells, pericytes, cancer-associated fibroblasts, tumor-associated macrophages, and other stromal cells
Serum PlGF is prognostic in colorectal cancer (Wei, 2009)
Also prognostic in gastric cancer (Chen, 2004) and HCC (Ho, 2007)

17. Mechanism of Placenta Growth Factor
Loges et al, Clin Cas Res ©American Association for Cancer Research

18. Insights on PlGF Four isoforms of PlGF in humans
PlGF transmits its own signal via VEGFR-1 (results is phosphorylation of different residues than VEGF-A)
PlGF augments VEGF-A signaling by displacing it from soluble VEGFR-1 (a negative regulatory mechanism), thereby increasing availability of VEGF-A
PlGF also causes transphosphorylation of VEGFR-2
PlGF upregulates the expression of proangiogenic molecules such as VEGF, FGF-2, and MMP-9
PlGF knock-out mice are healthy (unless challenged with inflammation, cancer, etc)

19. Role of Placenta Growth Factor
Loges et al, Clin Cas Res ©American Association for Cancer Research

20. PlGF in bevacizumab resistance
Colorectal cell lines that are chronically exposed to anti-VEGF-A therapy with bevacizumab show upregulation of compensatory pathways, including PlGF
These “bev-adapted” cell lines are also more metastatic
Fan et al, British J Cancer. ©Cancer Research UK

21. PlGF and GI Toxicity
In chemically induced models of intestinal injury:
Up to 6 fold increase in PlGF in the injured colon (minimal VEGF increase)
In PlGF knockout mice (-/-),
Substantial intestinal injury
Healing angiogenesis response is absent
Can be rescued by PlGF
Increased weight loss and chronic intestinal injury
Wild-type
PlGF
Knock-Out
(severe
injury)
S. Kopetz, MDACC
Hindryckx et al Lab Invest, ‘10, Fischer, Nat Rev Onc, ’08 ©Nature Publishing Group

22. Angiogenesis Outline/Objectives: Introduction Role of PlGF
a. Angiogenesis
b. Ongoing trials in GI cancers
Role of PlGF
Mechanisms of resistance

23. Resistance Intrinsic Resistance
Tumor cells can use existing blood vessels in vasculature-rich organs (lungs)
Absence of VEGF or VEGF receptors in metastatic tumors
Acquired Resistance
Induced pro-angiogenic factor substitution (FGF, PlGF, etc)
Recruitment of bone marrow-derived cells to restore neovascularization

24. Resistance Pathways Numerous compensatory factors and cell types
Ellis et al. Clin Cancer Res 2008;14:
Numerous compensatory factors and cell types

25. Preclinical Models of Resistance
Preclinical trials in a mouse model of pancreatic neuroendocrine (islet cell) cancer, Rip1–Tag2
Rip1–Tag2 mice were treated with a monoclonal antibody (DC101) that specifically blocked VEGFR signaling (in particular VEGFR2)
Initial response denoted by tumor stasis and reductions in tumor vascularity
Casanovas et al. Cancer Cell 2005:8;

26. Preclinical Models of Resistance
Response phase was transitory (10–14 days) and was followed by tumor regrowth
Dense tumor vasculature restored
Casanovas et al. Cancer Cell 2005:8;

27. Preclinical Models of Resistance
The relapsing tumors were found to express higher levels of the mRNAs for the pro-angiogenic factors fibroblast growth factor 1 and 2
Tumor-derived cells subjected to hypoxic conditions similarly upregulated most of the genes
Casanovas et al. Cancer Cell 2005:8;

28. RECIST Measurements for Representative Patient
Clinical Evidence
RECIST Measurements for Representative Patient
Prior to
Progression
“Angiogenic
Activity”
Hypothesis: resistance to angiogenesis inhibition should precede clinical progression
Kopetz; Lieu

29. PlGF and bFGF are Increased Prior to Progression
p<0.01 compared to baseline
ULN = upper limits of normal for healthy controls
Kopetz. GI ASCO

30. Conclusion
Inhibition of angiogenesis results is modest but meaningful benefit for multiple tumor types, including colorectal cancer.
Dearth of biomarkers for who benefits; who is harmed; how resistance occurs
VEGF-A has been the main focus, but the role other angiogenic signaling proteins (such as PlGF) under active study and drug development
Overcoming resistance via multiple bypassing pathways may be challenging

31. Angiogenesis
Overview
Thank You! 31