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Multifunctional proteins play a variety of roles in metabolism.Here, we examine the catalytic function of the combined 3-deoxy-D-arabino heptulosonate-7-phosphate synthase (DAH7PS) and chorismate mutase (CM) from Geobacillus sp. DAH7PS operates at the start of the biosynthetic pathway for aromatic metabolites, whereas CM operates in a dedicated branch of the pathway for the biosynthesis of amino acids tyrosine and phenylalanine. In line with sequence predictions, the two catalytic functions are located in distinct domains, and these two activities can be separated and retain functionality. For the full-length protein, prephenate, the product of the CM reaction, acts as an allosteric inhibitor for the DAH7PS. The crystal structure of the full-length protein with prephenate bound and the accompanying small angle x-ray scattering data reveal the molecular mechanism of the allostery. Prephenate binding results in the tighter association between the dimeric CM domains and the tetrameric DAH7PS, occluding the active site and therefore disrupting DAH7PS function. Acquisition of a physical gating mechanism to control catalytic function through gene fusion appears to be a general mechanism for providing allostery for this enzyme.

Non-small-cell lung cancer patients with activating mutations in epidermal growth factor receptor (EGFR) respond to EGFR tyrosine kinase inhibitor (TKI) treatment. Nevertheless, patients often develop central nervous system (CNS) metastases during treatment, even when their extracranial tumors are still under control. In the absence of effective options, much higher doses of EGFR TKIs have been attempted clinically, with the goal of achieving high enough drug concentrations within the CNS. Although limited tumor responses have been observed with this approach, the toxicities outside the CNS have been too high to tolerate. We report the discovery and early clinical development of AZD3759, a selective EGFR inhibitor that can fully penetrate the blood-brain barrier (BBB), with equal free concentrations in the blood, cerebrospinal fluid, and brain tissue. Treatment with AZD3759 causes tumor regression in subcutaneous xenograft, leptomeningeal metastasis (LM), and brain metastasis (BM) lung cancer models and prevents the development of BM in nude mice. An early clinical study in patients with BM and LM treated with AZD3759 confirms its BBB-penetrant properties and antitumor activities. Our data demonstrate the potential of AZD3759 for the treatment of BM and LM and support its further clinical evaluation in larger trials.

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