Oncogenic switch and single-agent MET inhibitor sensitivity in a subset of EGFR-mutant lung cancer

[Figure: see text].

Inhibition of Glycogen Synthase II with RNAi Prevents Liver Injury in Mouse Models of Glycogen Storage Diseases

Glycogen storage diseases (GSDs) of the liver are devastating disorders presenting with fasting hypoglycemia as well as hepatic glycogen and lipid accumulation, which could lead to long-term liver damage. Diet control is frequently utilized to manage the potentially dangerous hypoglycemia, but there is currently no effective pharmacological treatment for preventing hepatomegaly and concurrent liver metabolic abnormalities, which could lead to fibrosis, cirrhosis, and hepatocellular adenoma or carcinoma. In this study, we demonstrate that inhibition of glycogen synthesis using an RNAi approach to silence hepatic Gys2 expression effectively prevents glycogen synthesis, glycogen accumulation, hepatomegaly, fibrosis, and nodule development in a mouse model of GSD III. Mechanistically, reduction of accumulated abnormally structured glycogen prevents proliferation of hepatocytes and activation of myofibroblasts as well as infiltration of mononuclear cells. Additionally, we show that silencing Gys2 expression reduces hepatic steatosis in a mouse model of GSD type Ia, where we hypothesize that the reduction of glycogen also reduces the production of excess glucose-6-phosphate and its subsequent diversion to lipid synthesis. Our results support therapeutic silencing of GYS2 expression to prevent glycogen and lipid accumulation, which mediate initial signals that subsequently trigger cascades of long-term liver injury in GSDs.

Abstract 5192: Utilizing NSCLC PDXs derived from patients on osimertinib (AZD9291) clinical trials to further refine therapeutic strategies

Background: Osimertinib (AZD9291)is a mutant-selective EGFR tyrosine kinase inhibitor (TKI) effective against EGFR activating and the T790M acquired resistance mutations.Osimertinib has been approved by the US FDA for patients with EGFR T790M positive NSCLC with resistance to first line EGFR TKIs. However, as acquired resistance to osimertinib is now emerging, we aimed to develop PDXs from patients with: a) acquired resistance to first-line EGFR TKIs prior to enrolling on osimertinib trials and b) post-osimertinib resistance.

Methods: Pre- and post-osimertinib tumor biopsies were implanted into the flank or sub-renal capsule of NSG mice. Successfully established PDXs were expanded and confirmed by ddPCR and NGS to maintain molecular fidelity to the original patient tumor. The osimertinib efficacy in a subset of PDX models was tested and compared to clinical osimertinib response in the patients from whom the PDXs were derived. Acquired osimertinib resistance models were further treated with a panel of novel targeted agent combinations, matching the potential mechanism of osimertinib resistance.

Results: 46 patients underwent a pre-osimertinib or post-osimertinib biopsy. 26 biopsies were from the AURA trial for patients with acquired resistance to first-line EGFR TKIs; 5 biopsies were from the TATTON trial for patients without a T790M mutation; and 7 biopsies were from patients with acquired resistance to osimertinib. A platform of 16 PDX models have been successfully developed and shown to exhibit diverse mechanisms of TKI resistance as confirmed by NGS. These models include: 6 with EGFR T790M; 4 with EGFR non-T790M resistance to erlotinib; and 4 with acquired resistance to osimertinib. In the drug efficacy studies, PDX sensitivity to osimertinib is shown to be comparable to the corresponding patient's clinical response. In the DFCI-243 model (patient: EGFR T790M+, PR 8.9 months), tumors showed regression during the dosing phase and rapidly regrew upon cessation of osimertinib treatment. In contrast, in the DFCI-217 model (patient EGFR T790M+, PR >24 months), tumors showed sustained regression even after osimertinib treatment cessation. In the DFCI-284, a potential model of primary AZD9291 resistance tumors showed no regressions with osimertinib treatment. PDX models have also been used to refine treatment approaches for acquired resistance to osimertinib. DFCI-306 model established from a patient who developed an acquired BRAF mutation while on osimertinib has been shown to respond to either selumetinib or the selumetinib/osimertinib combination.

Conclusion: We have developed a platform of NSCLC PDXs from patients with acquired resistance to first-line EGFR TKIs and the newly approved third-generation inhibitor osimertinib. These models can be used to refine treatment strategies in patients with acquired resistance to first-line EGFR TKIs with primary or acquired resistance to osimertinib.

Citation Format: Sangeetha Palakurthi, Man Xu, Amanda J. Redig, Michael Dills, Prafulla Gokhale, Jinyun Choi, Atsuko Ogino, Yanan Kuang, Nora Feeney, Cloud Paweletz, Paul Kirscmeier, Jessie English, Darren Cross, Pasi Jänne. Utilizing NSCLC PDXs derived from patients on osimertinib (AZD9291) clinical trials to further refine therapeutic strategies. [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 5192.

Abstract A105: Credentialing the concept of “co-clinical trials”: Utility of lung cancer PDX models derived from patients on AZD9291 clinical trials

Background: The EGFR T790M mutation is the most common mechanism of acquired drug resistance to currently approved EGFR inhibitors gefitinib, erlotinib, and afatinib. AZD9291 is a mutant-selective EGFR inhibitor effective against both EGFR activating and T790M mutations while sparing wild type EGFR. AZD9291 is highly active in patients with lung cancer with the EGFR T790M mutation, with a response rate of 61% and progression free survival of ∼10 months. However, as resistance to AZD9291 is beginning to emerge, we aimed to develop patient derived xenografts (PDXs) using pre-treatment biopsies obtained from patients with acquired resistance to first-line EGFR inhibitors enrolling on clinical trials with AZD9291. These clinically annotated PDX models allow direct correlation with the clinical efficacy of AZD9291 in patients and may be useful in studying mechanisms of acquired resistance to AZD9291 and refine strategies for treatments.

Methods: Pre-AZD9291 treatment tumor biopsies (core needle biopsies or pleural effusions) were implanted into the flank or sub-renal capsule of NSG mice. Tumors were serially passed in NSG mice for up to 3 generations. Successfully established models were expanded and treated with AZD9291. The efficacy in the PDX model was compared to the clinical efficacy of AZD9291 in the patient from whom the model was derived.

Results: 33 patients underwent a pre-AZD9291 treatment biopsy (26 core needle; 7 pleural effusions). 26/33 patients enrolled in the AURA AZD9291 clinical trial for patients with acquired resistance to first-line EGFR inhibitors. From these patients, 10 PDX models have been successfully developed so far and confirmed by ddPCR to maintain fidelity to the original patient tumor's EGFR mutation status. These models include 6 with EGFR T790M and 4 with EGFR non-T790M mechanisms of resistance to erlotinib. Among the 10 patients used to develop PDX models, the best clinical response to AZD9291 included 5 partial responses, 3 progressive diseases, 1 stable disease and 1 acquired resistance. A subset of these PDX models were further tested for their sensitivity to AZD9291 and the data was consistent with the clinical responses of the patients. Two models, DFCI 243 and DFCI 217 (both with EGFR T790M; both patients with PR > 9 months) were treated with gefitinib (6.25mg/kg) or AZD9291 (25 mg/kg). Both models were confirmed to maintain EGFR T790M and had a dramatic response to AZD9291 but not to gefitinib treatment. However, tumors rapidly regrew upon cessation of AZD9291 treatment. DFCI 306 PDX model established from a patient with acquired resistance to monotherapy with AZD9291, showed AZD9291 resistance in vivo. AZD9291 treatment of DFCI 284, a model with EGFR T790M derived from a patient with primary resistance to AZD9291, is underway.

Conclusion: We have developed PDXs from patients with erlotinib resistance who were treated with AZD9291. The PDX platform is currently being utilized in studies to refine strategies to: a) improve durability of responses to AZD9291 in EGFR T790M mutation positive patients and b) identify combinations in EGFR T790M mutation positive or negative patients who have de novo or acquired resistance to AZD9291.

Citation Format: Sangeetha S. Palakurthi, Man Xu, Amanda Redig, Michael Dills, Prafulla Gokhale, Jihyun Choi, Atsuko Ogino, Yanan Kuang, Nora Feeney, Cloud Paweletz, Paul Kirschmeier, Jessie English, Darren Cross, Pasi A. Janne. Credentialing the concept of “co-clinical trials”: Utility of lung cancer PDX models derived from patients on AZD9291 clinical trials. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr A105.