Targeted investigational therapy potential to overcome crizotinib resistance in lung cancers

(Press-News.org) Contact information: Lauren Riley
lauren.riley@aacr.org
215-446-7155
American Association for Cancer Research
Targeted investigational therapy potential to overcome crizotinib resistance in lung cancers BOSTON — PF-06463922, an investigational drug being developed by Pfizer Inc., has the potential to become a new treatment option for patients who have lung cancer harboring abnormalities in the ALK gene, according to preclinical results presented here at the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics, held Oct. 19-23.

About 3 to 5 percent of lung cancers harbor ALK gene abnormalities. The drug crizotinib (Xalkori), which blocks ALK protein kinase activity, was approved in August 2011 by the U.S. Food and Drug Administration for the treatment of patients who have these lung cancers. Although robust responses to crizotinib are observed for lung cancers harboring ALK gene abnormalities, the majority eventually become resistant to the effects of the drug. In many cases, resistance arises because of genetic mutations in ALK.

"Resistance to targeted therapies such as crizotinib is a major challenge when treating patients with cancer," said Tod Smeal, Ph.D., associate research fellow in the Oncology Research Unit at Pfizer Inc. in San Diego, Calif. "Our goal is to take advantage of everything we have learned about designing drugs that target kinases like ALK and the ways in which lung cancers become resistant to crizotinib to develop the best next-generation ALK inhibitor we can.

"Our preclinical studies suggest that we are making progress toward achieving our goal: PF-06463922 has potent ALK-inhibiting activity, it is capable of inhibiting all the crizotinib-resistant ALK mutants so far detected in patients, and it can efficiently access the brain. We are excited about these preclinical results and very hopeful that they will translate into meaningful responses in the clinic."

After carefully designing PF-06463922, Smeal and colleagues first showed in cell assays that it potently inhibited the activity of ALK and all eight of the mutant forms of ALK known to cause resistance to crizotinib in patients with lung cancer. They then showed that PF-06463922 inhibited the growth of tumors harboring three of the crizotinib-resistant ALK mutants, including the most resistant ALK mutant, G1202R, in mice.

Further analysis indicated that PF-06463922 readily entered the brains of mice, rats, and dogs. In mice, levels of PF-06463922 in the brain were 20-30 percent of levels of PF-06463922 in the blood. This is potentially clinically relevant because a significant number of lung cancer patients will develop brain metastasis during the course of their disease, according to Smeal, although he noted that it will be important to see if these results in animals hold true in humans.

Smeal and colleagues also found that PF-06463922 potently inhibited the protein ROS1, a close relative of ALK recently implicated in a number of cancer types, including some lung and brain cancers. Further, PF-06463922 had antitumor effects in two mouse models of cancers driven by ROS1 gene abnormalities, leading the researchers to suggest that PF-06463922 has potential as a treatment for this subgroup of cancers, in addition to its promise as a new treatment for ALK-driven cancers.

### Smeal is an employee of Pfizer Inc., which funded the study.

The 2013 International Conference on Molecular Targets and Cancer Therapeutics is being co-hosted by the American Association for Cancer Research (AACR), the National Cancer Institute (NCI), and the European Organisation for Research and Treatment of Cancer (EORTC).

This research will be presented at a press conference entitled "Emerging Therapeutics" during the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics on Sunday, Oct. 20 at 10 a.m. ET in room 202 of the Hynes Convention Center in Boston, Mass. Reporters who cannot attend in person may call in using the following numbers:

U.S./Canada (toll-free): 800-446-2782 International (toll): 847-413-3235

To interview Tod Smeal, contact Katherine Reuter at katherine.reuter@pfizer.com or 917-543-4412. For other inquiries, contact Jeremy Moore at jeremy.moore@aacr.org or 215-446-7109.

About the American Association for Cancer Research Founded in 1907, the American Association for Cancer Research (AACR) is the world's oldest and largest professional organization dedicated to advancing cancer research and its mission to prevent and cure cancer. AACR membership includes more than 34,000 laboratory, translational, and clinical researchers; population scientists; other health care professionals; and cancer advocates residing in more than 90 countries. The AACR marshals the full spectrum of expertise of the cancer community to accelerate progress in the prevention, biology, diagnosis, and treatment of cancer by annually convening more than 20 conferences and educational workshops, the largest of which is the AACR Annual Meeting with more than 18,000 attendees. In addition, the AACR publishes eight peer-reviewed scientific journals and a magazine for cancer survivors, patients, and their caregivers. The AACR funds meritorious research directly as well as in cooperation with numerous cancer organizations. As the scientific partner of Stand Up To Cancer, the AACR provides expert peer review, grants administration, and scientific oversight of team science and individual grants in cancer research that have the potential for near-term patient benefit. The AACR actively communicates with legislators and policymakers about the value of cancer research and related biomedical science in saving lives from cancer. For more information about the AACR, visit http://www.AACR.org. Follow the AACR on Twitter: @AACR. Follow the AACR on Facebook: http://www.facebook.com/aacr.org.

About the National Cancer Institute The National Cancer Institute (NCI) leads the National Cancer Program and the NIH effort to dramatically reduce the prevalence of cancer and improve the lives of cancer patients and their families, through research into prevention and cancer biology, the development of new interventions, and the training and mentoring of new researchers. For more information about cancer, please visit the NCI Web site at http://www.cancer.gov or call NCI's Cancer Information Service at 1-800-4-CANCER (1-800-422-6237).

About the European Organisation for Research and Treatment of Cancer The European Organisation for the Research and Treatment of Cancer (EORTC) brings together European cancer clinical research experts from all disciplines for trans-national collaboration. Both multinational and multidisciplinary, the EORTC Network comprises more than 2,500 collaborators from all disciplines involved in cancer treatment and research in more than 300 hospitals in over 30 countries. Through translational and clinical research, the EORTC offers an integrated approach to drug development, drug evaluation programs and medical practices. EORTC Headquarters, a unique pan European clinical research infrastructure, is based in Brussels, Belgium, from where its various activities are coordinated and run. http://www.eortc.org

Abstract Number: A277
Presenter: Tod Smeal, Ph.D.

Title: PF-06463922, a novel ROS1/ALK inhibitor, demonstrates sub-nanomolar potency against oncogenic ROS1 fusions and capable of blocking the resistant ROS1G2032R mutant in preclinical tumor models

Authors: Helen Y. Zou, Lars R. Engstrom, Qiuhua Li, Melissa West Lu, Ruth Wei Tang, Hui Wang, Konstantinos Tsaparikos, Sergei Timofeevski, Justine Lam, Shinji Yamazaki, Wenyue Hu, Hovhannes Gukasyan, Nathan Lee, Ted W. Johnson, Valeria Fantin, Tod Smeal. Pfizer, Inc., San Diego, CA

The oncogenic ROS1 gene fusion (Fig-ROS1) was first identified in glioblastoma cells over two decades ago. Recently, ROS1 gene rearrangements were further discovered in a variety of human cancers, including lung adenocarcinoma, cholangiocarcinoma, ovarian cancer, gastric adenocarcinoma, colorectal cancer, inflammatory myofibroblastic tumor, angiosarcoma, and epithelioid hemangioendothelioma, providing additional evidence for ROS1 as an attractive cancer target. The 1st generation Met/ALK/ROS1 inhibitor XALKORI ® (crizotinib) has demonstrated promising clinical response in ROS1 fusion positive NSCLC. But similar to what was seen with acquired ALK secondary resistant mutations in XALKORI refractory patients, a ROS1 kinase domain mutant--ROS1G2032R has been identified in a ROS1 positive NSCLC patient who developed resistance to XALKORI. Therefore, there is an urgent need to develop agents that can overcome this type of resistance.

PF-06463922 is a novel, orally available, ATP-competitive small molecule inhibitor of ROS1/ALK with exquisite potency against ROS1 kinase. PF-06463922 inhibited the catalytic activity of recombinant ROS1 with a mean Ki of < 0.005 nM, and inhibited ROS1 autophosphorylation at IC50 values ranging from 0.1 nM to 1 nM cross a panel of cell lines harboring oncogenic ROS1 fusion variants including CD74-ROS1, SLC34A2-ROS1 and Fig-ROS1. PF-06463922 also inhibited cell proliferation and induced cell apoptosis at sub- to low-nanomolar concentrations in the HCC78 human NSCLC cells harboring SLC34A2-ROS1 fusions and the BaF3-CD74-ROS1 cells expressing human CD74-ROS1. In the BaF3 cells engineered to express the XALKORI resistant CD74-ROS1G2032R mutant, PF-06463922 demonstrated nanomolar potency against either ROS1G2032R cellular activity or cell proliferation. In vivo, PF-06463922 demonstrated marked cytoreductive antitumor efficacy at low nanomolar concentration in the NIH3T3 xenograft models expressing human CD74-ROS1 and Fig-ROS1. The antitumor efficacy of PF-06463922 was dose dependent and strongly correlated to inhibition in ROS1 phosphorylation and the downstream signaling molecules pSHP1, pSHP2 and pErk1/2, as well as inhibition of the cell cycle protein Cyclin D1 in tumors. To our knowledge, PF-06463922 is the first reported ROS1 inhibitor that is capable of blocking the resistant ROS1G2032R mutant at predicted pharmacologically relevant concentrations. Our data indicate that PF-06463922 has great potential for treating ROS1 fusion positive cancers including those from patients who relapsed from XALKORI therapy due to acquired ROS1G2032R mutation.

Abstract Number: PR10/B107
Presenter: Tod Smeal, Ph.D.

Title: Is CNS availability for oncology a no-brainer? Discovery of PF-06463922, a novel small molecule inhibitor of ALK/ROS1 with pre-clinical brain availability and broad spectrum potency against ALK-resistant mutations

Authors: Ted W. Johnson, Simon Bailey, Benjamin J. Burke, Michael R. Collins, J. Jean Cui, Judy Deal, Ya-Li Deng, Martin P. Edwards, Mingying He, Jacqui Hoffman, Robert L. Hoffman, Qinhua Huang, Robert S. Kania, Phuong Le, Michele McTigue, Cynthia L. Palmer, Paul F. Richardson, Neal W. Sach, Graham L. Smith, Lars Engstrom, Wenyue Hu, Hieu Lam, Justine L. Lam, Tod Smeal, Helen Y. Zou. Pfizer, Inc., San Diego, CA

Oncogenic fusions of Anaplastic Lymphoma Kinase (ALK) define a subset of human lung adenocarcinoma. The 1st generation ALK inhibitor crizotinib demonstrated impressive clinical benefit in ALK-fusion positive lung cancers and was approved by the FDA for the treatment of ALK-fusion positive NSCLC in 2011. However, as seen with most kinase inhibitors, patients treated with crizotinib eventually develop resistance to therapy. Acquired ALK kinase domain mutations and disease progression in the central nervous system (CNS) are reported as main contributors to patient relapse after ALK inhibitor therapy. Preclinically, crizotinib lacks significant brain penetration and does not potently inhibit activity of ALK kinase domain mutants, so a drug discovery program was initiated aimed to develop a second generation ALK inhibitor that is more potent than existing ALK inhibitors, capable of inhibiting the resistant ALK mutants and penetrating the blood-brain-barrier. These objectives present a considerable challenge in kinase inhibitor chemical space.

Here we report that PF-06463922, a novel small molecule ATP-competitive inhibitor of ALK/ROS1, showed exquisite potencies against non-mutant ALK (Ki END