Novel approaches to gastrointestinal stromal tumors resistant to imatinib and sunitinib

Antitumor efficacy of CHMFL-KIT-110 solid dispersion in mouse xenograft models of human gastrointestinal stromal tumors

PURPOSE

CHMFL-KIT-110, a selective c-KIT kinase inhibitor for gastrointestinal stromal tumors (GISTs), possesses a poorly water-soluble, limiting the further development of the drug. This study was to investigate the antitumor efficacy of CHMFL-KIT-110 and CHMFL-KIT-110 solid dispersion (laboratory code: HYGT-110 SD) in GIST tumor xenograft models and to explore the PK/PD relationship of HYGT-110 SD.

METHODS

Plasma concentrations of HYGT-110 and HYGT-110 SD were determined by LC-MS/MS in KM mice. Antitumor activity was evaluated by measuring tumor volume and weight in c-KIT-dependent GIST xenograft models. PK/PD relationship was assessed by LC-MS/MS and Western Blot in the GIST-T1 xenografted mice.

RESULTS

HYGT-110 exhibited a low oral bioavailability (10.91%) in KM mice. Compared with HYGT-110 treatment, the C_max and AUC_0-t of HYGT-110 SD in mice plasma were substantially increased by 18.81 and 6.76-fold, respectively. HYGT-110 SD (10, 30, and 100 mg/kg/day) also could dose-dependently decrease the tumor volume and weight in the GIST-882 cell-inoculated xenograft mouse models and show 86.35% tumor growth inhibition (TGI) at 28 days at a 25 mg/kg bid dosage in the GIST-T1 cell-inoculated xenograft mouse model. The free concentration of HYGT-110 in plasma was closely correlated with the inhibition of c-KIT phosphorylation levels in tumor tissues.

CONCLUSIONS

In comparison with the HPMC formulation, both improved PK and PD characteristics of the solid dispersion formulation of CHMFL-KIT-110 were observed in in vivo animal experiments.

The Pharmacokinetic-Pharmacodynamic (PKPD) Relationships of AZD3229, a Novel and Selective Inhibitor of KIT, in a Range of Mouse Xenograft Models of GIST

PURPOSE

The emergence of secondary mutations is a cause of resistance to current KIT inhibitors used in the treatment of patients with gastrointestinal stromal tumors (GIST). AZD3229 is a selective inhibitor of wild-type KIT and a wide spectrum of primary and secondary mutations seen in patients with GIST. The objective of this analysis is to establish the pharmacokinetic-pharmacodynamic (PKPD) relationship of AZD3229 in a range of mouse GIST tumor models harboring primary and secondary KIT mutations, and to benchmark AZD3229 against other KIT inhibitors.

EXPERIMENTAL DESIGN

A PKPD model was developed for AZD3229 linking plasma concentrations to inhibition of phosphorylated KIT using data generated from several in vivo preclinical tumor models, and in vitro data generated in a panel of Ba/F3 cell lines.

RESULTS

AZD3229 drives inhibition of phosphorylated KIT in an exposure-dependent manner, and optimal efficacy is observed when >90% inhibition of KIT phosphorylation is sustained over the dosing interval. Integrating the predicted human pharmacokinetics into the mouse PKPD model predicts that an oral twice daily human dose greater than 34 mg is required to ensure adequate coverage across the mutations investigated. Benchmarking shows that compared with standard-of-care KIT inhibitors, AZD3229 has the potential to deliver the required target coverage across a wider spectrum of primary or secondary mutations.

CONCLUSIONS

We demonstrate that AZD3229 warrants clinical investigation as a new treatment for patients with GIST based on its ability to inhibit both ATP-binding and A-loop mutations of KIT at clinically relevant exposures.

Gastrointestinal stromal tumors: diagnosis, therapy and follow-up care in Austria

Optimal treatment for patients suffering from gastrointestinal stromal tumors (GIST) is based on an interdisciplinary treatment approach. Austrian representatives of Medical and Surgical Oncology, Pathology, Radiology, Nuclear Medicine, Gastroenterology, and Laboratory Medicine issued this manuscript on a consensual base within the context of currently available and published literature. This paper contains guidelines and recommendations for diagnosis, therapy, and follow-up of GIST patients in Austria.

Gastrointestinal stromal tumors (GISTs): an updated experience

BACKGROUND

Gastrointestinal stromal tumors (GISTs) are relatively common mesenchymal tumors of the digestive tract characterized by c-KIT mutations. This is a comprehensive review of the current data of the literature on the various aspects of the diagnosis and treatment of these tumors.

METHODS

The stomach is the most commonly involved site for these tumors in the digestive tract. Computed tomography and endoscopy can usually establish the diagnosis. The study of certain specific immunohistochemical markers may contribute to better characterization of these tumors.

RESULTS

Surgical resection of GISTs has been the most effective therapy. In addition, targeted therapy with tyrosine kinase inhibitors may reduce the development of recurrence or decrease the disease progression in patients with metastatic disease.

CONCLUSIONS

The introduction of tyrosine kinase inhibitors has resulted in significant improvement in the overall prognosis of these patients. Furthermore, preoperative imatinib can decrease tumor volume and is associated with complete surgical resection in locally advanced primary GISTs.

Pleomorphic phenotypes of gastrointestinal stromal tumors at metastatic sites with or without imatinib treatment

Secondary resistance of gastrointestinal stromal tumors (GISTs) to tyrosine kinase inhibitors occurs after several years' administration. However, the mechanism of resistance has not been fully clarified. In this study, we analyzed the genotypes and the histologic and immunohistochemical phenotypes of metastatic GISTs with and without imatinib treatment, and clarified the pleomorphic nature of metastatic GISTs. We examined 31 autopsy cases in which the patients died of multiple metastases of GISTs, and two surgically resected specimens with and without imatinib treatment. A total of 152 primary and metastatic lesions in 33 cases of GISTs were examined for histologic and immunohistochemical expression of KIT and CD34. We analyzed the expression of other receptor tyrosine kinases (RTKs) in KIT-negative lesions, including human EGFR-related 2 (HER2), epidermal growth factor receptor (EGFR), hepatocyte growth factor receptor (MET), platelet-derived growth factor receptor-alpha (PDGFRA), and platelet-derived growth factor receptor-beta (PDGFRB). Fifteen lesions in seven cases (9.9%) lacked KIT expression, and 74 (49%) in 22 cases lacked CD34 expression. Eight KIT-negative lesions in five cases expressed PDGFRB, one of which also expressed EGFR, and three lesions in one case expressed MET. Results for the other RTKs were negative. Missense point mutations at PDGFRB gene exon 12 were detected in one PDGFRB-positive case. Our results indicate that histomorphology, immunohistochemical phenotypes, and genotypes of metastatic GISTs vary among lesions, even in cases without imatinib treatment. A KIT-independent mechanism, such as activation of other RTKs, might participate in the proliferation of late-stage GISTs and might be a cause of secondary imatinib resistance.

Gastrointestinal stromal tumors: Recommendations on diagnosis, therapy and follow-up care in Austria

Adequate treatment of gastrointestinal stromal tumors (GISTs) is linked to an interdisciplinary treatment approach. Austrian representatives of medical oncology, surgery, pathology, radiology and gastroenterology have issued this consensus manuscript within the context of currently available and published literature. The paper contains guidelines and recommendations for diagnosis, therapy and follow-up of GIST patients in Austria.

[Imaging of gastrointestinal stromal tumors]

Gastrointestinal stromal tumors (GIST) arising from interstitial cells of Cajal, represent the first type of solid tumor, which is very sensitive to a specific molecularly targeted tyrosine kinase receptor blocker (i. e., imatinib). On CT, which is considered as the reference technique, GISTs typically present as large, well-delineated, heterogeneous and sometimes exophytic masses. In contrast with the absence of lymph node involvement, hepatic metastasis as well as mesenteric involvement can be observed. MR-enteroclysis is indicated to investigate the local extent of the disease in specific cases whereas MR imaging is used to detect hepatic metastasis. Because of a specific treatment, contrast-enhanced imaging is needed for the follow-up of treated tumors. Evaluation of tumor response to treatment is best assessed with CT which still remains the reference imaging technique whereas FDG-PET imaging is used in specific cases.