On October 27, 2015 Threshold Pharmaceuticals, Inc. (NASDAQ: THLD) reported that it will present preclinical data on tarloxotinib bromide*, or "tarloxotinib", in two scientific posters at the AACR (Free AACR Whitepaper)-NCI-EORTC AACR-NCI-EORTC (Free AACR-NCI-EORTC Whitepaper) International Conference on Molecular Targets and Cancer Therapeutics (EORTC-NCI-AACR) (Free ASGCT Whitepaper) (Free EORTC-NCI-AACR Whitepaper), which will be held November 5-9, 2015, in Boston (Press release, Threshold Pharmaceuticals, OCT 27, 2015, View Source [SID:1234507810]). Tarloxotinib is Threshold’s proprietary hypoxia-activated, irreversible epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor exclusively licensed from the University of Auckland, New Zealand. The data highlight preclinical rationale in support of two ongoing Phase 2 proof-of-concept trials of tarloxotinib in non-small cell lung cancer and in squamous cell carcinomas of the head and neck or skin.
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Poster Presentations
Abstract A66: Preclinical efficacy of tarloxotinib bromide (TH-4000), a hypoxia-activated EGFR/HER2 inhibitor: rationale for clinical evaluation in EGFR mutant, T790M-negative NSCLC following progression on EGFR-TKI therapy.
Abstract A67: Preclinical rationale for the ongoing Phase 2 study of the hypoxia-activated EGFR-TKI tarloxotinib bromide (TH-4000) in patients with advanced squamous cell carcinoma of the head and neck (SCCHN) or skin (SCCS).
Both posters will be presented on Friday November 6, 2015, from 12:15 PM – 3:15 PM during Poster Session A in Exhibit Hall C-D.
The abstracts are now available on the AACR (Free AACR Whitepaper)-NCI-EORTC meeting website.
About Non-Small Cell Lung Cancer
Lung cancer is the most common cause of death from cancer worldwide; an estimated 1.8 million new cases were diagnosed in 2012.1 The most common type of lung cancer, non-small cell lung cancer (NSCLC), accounts for approximately 85 to 90 percent of cases.2 EGFR activating mutations occur in approximately 10 percent of NSCLC cases in Caucasian patients and up to 35 percent in Asian patients.3 Tarceva, Iressa, and Gilotrif are the first- and second-generation EGFR inhibitors currently approved for patients with the EGFR activating mutations. Nearly all patients ultimately progress on these therapies due to a variety of resistance mechanisms.
One largely unexplored mechanism of treatment resistance is through expression of not only mutant EGFR but also through the emergence of normal, or "wild-type" EGFR, and its subsequent stimulation by growth factors produced in the tumor microenvironment. Hypoxia upregulates the wild-type EGFR protein and its ligand TGF-alpha, leading to elevated EGFR signaling.4,5 Tumors that are heterozygous for EGFR (containing both wild-type EGFR and mutant EGFR) are associated with worse outcomes than is the case with homozygous mutant EGFR.6 Heterozygous disease has also been proposed as a cause of resistance to EGFR inhibitors.7 Tarloxotinib, which is designed to inhibit both mutant as well as wild-type EGFR in a tumor-selective manner, may effectively address these potentially important mechanisms of treatment resistance.
About Squamous Cell Carcinomas Head and Neck
Most head and neck cancers, which include cancers of the larynx (voice box), throat, lips, mouth, nose, and salivary glands, begin in the squamous cells that line the moist surfaces inside the head and neck, and are therefore referred to as squamous cell carcinomas of the head and neck (SCCHN). SCCHN is diagnosed in approximately 59,000 people in the U.S. annually and is responsible for some 12,000 deaths.8 In the recurrent/metastatic setting, chemotherapy or cetuximab monotherapy is the standard of care with response rates of about ten percent and disease progression occurs within two to three months.9
About Squamous Cell Carcinomas of the Skin
Non-melanoma skin cancers typically resulting from chronic sun exposure or other sources of ultraviolet rays are the most common types of cancer. Twenty percent of these skin cancers originate from squamous cells normally present in the outer layers of the skin (SCCS); five percent of SCCS will become locally advanced, recur, or metastasize. In the U.S., approximately 2,000 deaths per year are attributed to SCCS.10 As with SCCHN, SCCS is associated with EGFR overexpression and appear to be responsive to EGFR inhibitor therapy.11
About Tarloxotinib Bromide
Tarloxotinib bromide, or "tarloxotinib", is a prodrug designed to selectively release a covalent (irreversible) EGFR tyrosine kinase inhibitor under severe hypoxia, a feature of many solid tumors. Accordingly, tarloxotinib has the potential to effectively shut down aberrant EGFR signaling in a tumor-selective manner, thus potentially avoiding or reducing the systemic side effects associated with currently available EGFR tyrosine kinase inhibitors. Tarloxotinib is currently being evaluated in two Phase 2 proof-of-concept trials: one for the treatment of patients with mutant EGFR-positive, T790M-negative advanced non-small cell lung cancer progressing on an EGFR tyrosine kinase inhibitor, and the other for patients with recurrent or metastatic squamous cell carcinomas of the head and neck or skin. Threshold licensed exclusive worldwide rights to tarloxotinib from the University of Auckland, New Zealand, in September 2014.