Fibroblast growth factor receptors (FGFRs) are widely expressed in multiple organ systems and are involved in growth and angiogenesis. Mutations, translocations and amplifications in FGFR genes have been observed in several types of cancer. The purpose of this study was to identify biomarkers that may predict sensitivity and may change upon FGFR inhibition.
240 tumor cell lines from different types of cancer were treated with a small molecule FGFR inhibitor and IC50 values were calculated. Mutations, amplifications, deletions, gene expression analysis, and network analysis were used to find biomarkers that were sensitive or resistant to the inhibitor. Xenografts were used to identify pharmacodynamics biomarkers. Tumors from cancer patients were analyzed for FGFR gene amplifications using Fluorescent in situ hybridization.
FGFR1 mRNA overexpression and FGFR2 amplification were identified as sensitive biomarkers while Kras mutation was associated with resistance. Multiple sensitive cell lines (n = 2-4) were found in cells derived from breast, lung, gastric, kidney, lymphoma, sarcoma, melanoma, and endometrial cancer. No sensitive cell lines were found in colorectal, pancreatic, leukemia, myeloma, or ovarian cancer. In human breast cancer cell lines, amplifications were found for FGFR1 (23%), FGFR2 (11%), and FGFR4 (16%). Of the 26 breast cancer cell lines analyzed for FGFR1 amplification, 5 had moderate amplification (4-10 copies) and 1 was highly amplified (>10 copies). In non-small cell lung cancer cell lines, amplifications were found for FGFR1 (37%) and FGFR2 (20%). In xenografts, pS6 and pMAPK levels changed upon compound treatment. FGFR1 and FGFR2 amplifications were also found in prostate (15% and 15%, respectively) tumors from patients.
This study identified biomarkers for an FGFR small molecule inhibitor. These results may provide a rationale for patient selection and patient dosing when using a FGFR inhibitor.
Note that others, such as ISIS, are pursuing FGFR4 as a target for obesity as well
Activating mutations in the receptor tyrosine kinase, KIT, are found in the majority of gastrointestinal stromal tumors (GIST) and further secondary resistance mutations in KIT frequently arise upon treatment with tyrosine kinase inhibitors such as imatinib. KIT and its mutant forms are sensitive clients of HSP90 and it has been suggested that HSP90 inhibition could be an effective treatment for both imatinib-sensitive and imatinib-resistant GIST, which can occur simultaneously in different clones within the same patient.
AT13387 is a fragment-derived, potent HSP90 inhibitor, which is currently being evaluated in clinical trials. To evaluate its anti-tumor activity against GIST, AT13387 was tested in both imatinib-sensitive (GIST882, GIST-PSW) and imatinib-resistant (GIST430, GIST48) in vitro and in vivo GIST models.
AT13387 inhibited the proliferation of GIST cell lines at sub-100 nM potencies, irrespective of their sensitivity to imatinib. Treatment of GIST882, GIST430 and GIST48 cells with AT13387 induced HSP70, a marker of HSP90 inhibition, whilst reducing the levels of the client proteins KIT, AKT and their phosphorylated forms. A concomitant decrease in the levels of phospho-ERK and phospho-S6 demonstrated that KIT signalling was being inhibited in all cell lines, whilst an increase in cleaved PARP indicated apoptosis. In contrast, treatment with imatinib inhibited KIT signalling only in the imatinib-sensitive line, GIST882.
In vivo, the efficacy of AT13387 was tested in imatinib-sensitive (GIST-PSW) and imatinib-resistant (GIST430) xenograft models. AT13387, dosed once a week, inhibited the growth of both xenografts; depletion of phospho-KIT and inhibition of KIT signalling were again seen in these tumors. As expected, treatment with imatinib caused significant regression of the GIST-PSW tumors but not of GIST430. The combination of imatinib and AT13387 significantly enhanced tumor growth inhibition (T/C 21%) over either of the monotherapies (T/C 30% for AT13387, 46% for imatinib) in the GIST430 xenograft. Importantly, the combination was well tolerated.
AT13387 is currently being evaluated in a Phase II GIST trial both as single agent and in combination with imatinib. These results support the potential efficacy of the compound in both imatinib-sensitive and imatinib-resistant GIST and its current testing in this disease.
ASTX management seemed to indicate on a 10/26 webcast that the phase 1 data for this compound would be presented at this meeting, but this is the only listed abstract. I am seeking clarification from the company.
Tumor cells primarily utilize aerobic glycolysis, rather than oxidative phosphorylation, to metabolize glucose (the Warburg effect). The M2 splice form of pyruvate kinase (PKM2), the enzyme catalyzing the rate-limiting final step of glycolysis, is highly upregulated in tumors. Unlike the M1 splice form (PKM1), a constitutively active tetramer found predominantly in non-cancerous tissues, PKM2 is an inactive dimer under normal physiological conditions. Tetramerization of PKM2 requires binding of the allosteric activator fructose-1,6-bisphosphate (FBP), an upstream glycolytic intermediate, resulting in a fully active enzyme. Inactivation of PKM2 by cancer cells may allow glycolytic intermediates to be diverted into other biosynthetic pathways necessary for biomass production. The finding that PKM2 rather than PKM1 expression enhances tumorigenicity suggests that activators of PKM2 may have anti-tumor properties. We have identified and developed a series of small molecule PKM2 activators that exhibit low nM activation activity in biochemical and cell-based assays that measure pyruvate and ATP production. The extent of activation of these compounds is equal to or greater than that of FBP in biochemical assays. In addition, preliminary studies show that PKM2 activators inhibit the growth of lung cancer cell lines in vitro. The current lead compound was tested in established subcutaneously implanted A549 lung adenocarcinoma xenografts, where we observed a statistically significant 54% decrease in tumor growth, with no observable toxicity. These data suggest that this class of PKM2 activators is effective as tumor cell metabolic regulators with anti-tumor activity for lung cancer and potentially other malignancies.
Note that this program has been mentioned as being included in the Montigen spinout company.
The proto-oncogene PIM kinase family (PIM-1, -2 and -3) comprises constitutively active serine/threonine kinases upregulated in multiple cancer indications, including lymphoma, leukemia, multiple myeloma, prostate, bladder, gastric and head & neck cancers. Overexpression of one or more PIM family members in patient tumors frequently correlates with poor prognosis. The PIM kinases function by inhibiting apoptosis in MYC-driven tumors, promoting tumor cell survival and proliferation. PIM-1 and PIM-2 overexpression models were obtained in the human prostate cancer cell lines PC-3M and 22RV-1 and the non-tumorigenic mouse NIH-3T3 background. Overexpression of PIM kinases led to enhanced cell growth and tumorigenicity in both NIH-3T3 and 22RV-1 cell lines. In the PC-3M cell line, enhanced phosphorylation of the PIM kinase substrate BAD (pBAD) was observed following PIM overexpression. Enhancement of pBAD was inhibited by SGI-1776, a well-described PIM inhibitor [this drug was terminated by Supergen after phase 1 due to cardiac toxicity], as well as next generation PIM inhibitors exhibiting 4-10 fold improved potency against the PIM kinase family. The current PIM inhibitors display sub-µM activity in pharmacodynamic marker, proliferation and 2D colony formation assays using the PC-3M prostate cancer cell line, the UM-UC-3 bladder cancer cell line, and the HSC3 head & neck cancer cell line. The second generation PIM inhibitors possess favorable hERG and CYP inhibition profiles compared with SGI-1776, and demonstrate excellent oral bioavailability. In vivo xenograft studies using both PIM overexpression models and clinically relevant solid tumor models will facilitate identification of a clinical candidate.
Note that this program will be included in the Montigen spinout company from Astex