Activity and safety of the multi-target tyrosine kinase inhibitor cabozantinib in patients with metastatic gastrointestinal stromal tumour after treatment with imatinib and sunitinib: European Organisation for Research and Treatment of Cancer phase II trial 1317 'CaboGIST'

BACKGROUND

Gastrointestinal stromal tumour (GIST) is commonly treated with tyrosine kinase inhibitors (TKIs), but most patients ultimately develop secondary resistance. Cabozantinib, a multi-targeted TKI inhibitor, has activity in patient-derived GIST mouse xenograft models and can overcome compensatory MET signalling occurring on TKI treatment. European Organisation for Treatment of Cancer (EORTC) 1317 'CaboGIST' assessed the safety and activity of cabozantinib in patients with GIST who had progressed on imatinib and sunitinib.

METHODS

In this multi-center, open label, single arm phase II study, eligible GIST patients received oral cabozantinib (60 mg) once daily. Primary end-point was the progression-free survival rate at 12 weeks assessed by the local investigator per Response Evaluation Criteria in Solid Tumours 1·1. If at least 21 of the first 41 eligible and evaluable patients were progression-free at week 12, the activity of cabozantinib was sufficient to warrant further exploration according to the A'Hern one-stage study design.

FINDINGS

A total of 50 eligible patients started treatment between 02/2017 and 08/2018, including four (8%) still continuing cabozantinib at clinical cut-off (09/2019). The number of 3-weekly treatment cycles ranged from 1 to 30. Among the first 41 eligible and evaluable patients, 24 were progression-free at week 12 (58·5%, 95% confidence interval [CI] 42·0-74·0%). Among all 50 patients, 30 were progression-free at week 12 (60%, 95% CI 45-74%). Seven patients achieved a partial response (14%, 95% CI 6-27%), and 34 had stable disease (68%, 95% CI 53-80%) as best response. Progression was seen in eight patients (16%, 95% CI 7-29%), and one was not evaluable. Disease control was achieved in 41 patients (82%, 95% CI 69-91%). Median progression-free survival was 5·5 months (95% CI 3·6-6·9). The most common adverse events were diarrhoea (76%), palmar-plantar erythrodysesthesia syndrome (60%), fatigue (50%), hypertension (42%), weight loss (40%) and oral mucositis (30%), with 32 (64%) patients requiring dose reductions, 27 (54%) having treatment interruptions and no cabozantinib-related deaths observed.

INTERPRETATION

EORTC 1317 met its primary end-point, with 24/41 patients being progression-free at week 12 of treatment. The objective response was 14% with an encouraging disease control rate of 82%. Results of this trial confirm preclinical findings and warrant further exploration of cabozantinib in GIST.

CLINICAL TRIAL NUMBERS

EORTC 1317, NCT02216578, EudraCT 2014-000501-13.

Is sunitinib a Narrow Therapeutic Index Drug? - A systematic review and in vitro toxicology-analysis of Sunitinib vs. Imatinib in cells from different tissues

Narrow Therapeutic Index Drugs (NTIDs) are characterized by a small range between therapeutic and toxicological effect. Missing international harmonized definition for NTIDs the EMA does not even have a definition of NTIDs in contrast to the U.S. FDA, Health Canada, and the Japanese NIHS. Sunitinib, a tyrosine kinase inhibitor (TKI), indicated for the treatment of certain cancer types, will be running off-patent soon. Falling into the category of NTID would have a major impact on regulatory requirements for generic applications. Our analyses of metadata revealed numerous arguments in favor of a NTID designation. We used in vitro experiments to also give initial experimental answers. Five cell types of different tissue origin were examined for determination of IC50-values in cell viability assays. For comparison, the first-in-class TKI Imatinib was used as reference non-NTID drug. In addition, apoptotic proteins were investigated with respect to their expression and phosphorylation status. These in vitro experiments showed systematically higher toxicity of Sunitinib compared to Imatinib and a different expression and phosphorylation pattern of apoptotic proteins. In vitro data can only give preliminary results and further experiments with clinical blood samples and tumor biopsies are needed to finally clarify NTID status of Sunitinib.

Extended molecular dynamics of a c-kit promoter quadruplex

The 22-mer c-kit promoter sequence folds into a parallel-stranded quadruplex with a unique structure, which has been elucidated by crystallographic and NMR methods and shows a high degree of structural conservation. We have carried out a series of extended (up to 10 μs long, ∼50 μs in total) molecular dynamics simulations to explore conformational stability and loop dynamics of this quadruplex. Unfolding no-salt simulations are consistent with a multi-pathway model of quadruplex folding and identify the single-nucleotide propeller loops as the most fragile part of the quadruplex. Thus, formation of propeller loops represents a peculiar atomistic aspect of quadruplex folding. Unbiased simulations reveal μs-scale transitions in the loops, which emphasizes the need for extended simulations in studies of quadruplex loops. We identify ion binding in the loops which may contribute to quadruplex stability. The long lateral-propeller loop is internally very stable but extensively fluctuates as a rigid entity. It creates a size-adaptable cleft between the loop and the stem, which can facilitate ligand binding. The stability gain by forming the internal network of GA base pairs and stacks of this loop may be dictating which of the many possible quadruplex topologies is observed in the ground state by this promoter quadruplex.

Prevalence of gastrointestinal stromal tumour (GIST) in the United Kingdom at different therapeutic lines: an epidemiologic model

BACKGROUND

The prevalence of patients with gastrointestinal stromal tumourgst (GIST) who fail currently available treatments imatinib and sunitinib (third-line treatment-eligible GIST) is unknown, but is expected to be below an ultra-orphan disease threshold of 2/100,000 population used in England and Wales. Our study was designed to estimate the prevalence and absolute number of UK patients with unresectable/metastatic GIST at first-, second- and eventually third-line treatment.

METHODS

Our open population model estimates the probability that the prevalence of UK third-line treatment-eligible GIST patients will remain under the ultra-orphan disease threshold. Model parameters for incidence, proportion of unresectable/metastatic disease and survival estimates for GIST patients were obtained from a targeted literature review and a UK cancer register. The robustness of the results was checked through differing scenarios taking extreme values of the input parameters.

RESULTS

The base-case scenario estimated a prevalence of third-line treatment-eligible GIST of 1/100,000 and a prevalence count of 598 with a 99.9% likelihood of being below the ultra-orphan disease threshold. The extreme scenarios, one-way and probabilistic sensitivity analyses and threshold analysis confirmed the robustness of these results.

CONCLUSIONS

The prevalence of third-line treatment-eligible GIST is very low and highly likely below the ultra-orphan disease threshold.

Spectrum of mutations in gastrointestinal stromal tumor patients - a population-based study from Slovakia

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of gastrointestinal tract and are characterized by presence of mutations in tyrosine kinases cKIT (KIT) and PDGFRα (PDGFRA). Mutations identified are highly heterogeneous, but some mutations are associated with specific clinical features of the tumor. Samples from 278 GIST patients collected during the period 2004-2011 were screened for mutations in exons 9, 11, 13, and 17 of KIT and 12, 14 and 18 of PDGFRA. Results of mutation screening were summarized and tested for possible association with clinical parameters of tumors. Mutations were identified in 83.81% of patients. Most frequent mutations were found in KIT exon 11 reaching frequency of 62.95%. Other exons contributed to the mutation pool with frequencies 8.27%, 7.55%, 2.52%, 1.44%, 1.08%, and 0.00%, in decreasing order KIT exon 9, PDGRFA exons 18 and 12, KIT exon 13, PDGFRA exon 14, and KIT exon 17. General linear model analysis showed no effect of any individual analyzed mutation on the phenotypic variables, but we confirmed association between mutations KIT exon 9 p. 503-504_dup2, and PDGFRA exon 18 p. D842V and intestinal and gastric localization of tumors.

Locally ablative non-surgical management of colo-rectal liver metastasis

BACKGROUND

Liver is one of the commonest sites of metastasis in colorectal cancer patients. Solitary liver metastasis or oligometastasis are traditionally treated by surgical resection or chemotherapy.

DISCUSSION

There may be a subgroup of these patients who are not suitable for surgery or chemotherapy due to various co-morbid factors. These patients can be treated by novel minimally invasive or noninvasive ablative techniques like interstitial brachytherapy, extracranial stereotactic radiotherapy, and radiofrequency ablation.

Imatinib mesylate: past successes and future challenges in the treatment of gastrointestinal stromal tumors

Just over a decade ago, gastrointestinal tumours were a poorly understood mesenchymal neoplasm unsuccessfully treated with chemotherapy. Cytotoxic therapy for advanced disease yielded response rates of 10% and median survival of just 18 months. However, the discovery of KIT and platelet derived growth factor receptor alpha (PDGFRA) mutations as oncogenic drivers of most gastrointestinal tumours, paved the way for targeted therapy. Imatinib mesylate, a tyrosine kinase inhibitor, produces a clinical benefit rate (complete response, partial response, and stable disease) of more than 80% in metastatic setting and a median survival of 57 months. Imatinib is now also approved in adult patients following resection of KIT-positive GIST. Major insights into the mechanism of action of imatinib, unique pharmacokinetics, drug resistance, and management of low grade but chronic adverse effects continue to be made.

Cetuximab plus capecitabine and irinotecan compared with cetuximab plus capecitabine and oxaliplatin as first-line treatment for patients with metastatic colorectal cancer: AIO KRK-0104--a randomized trial of the German AIO CRC study group

PURPOSE

The AIO KRK-0104 randomized phase II trial investigated the efficacy and safety of cetuximab combined with capecitabine and irinotecan (CAPIRI) or capecitabine and oxaliplatin (CAPOX) in the first-line treatment of metastatic colorectal cancer (mCRC).

PATIENTS AND METHODS

A total of 185 patients with mCRC were randomly assigned to cetuximab (400 mg/m(2) day 1, followed by 250 mg/m(2) weekly) plus CAPIRI (irinotecan 200 mg/m(2), day 1; capecitabine 800 mg/m(2) twice daily days 1 through 14, every 3 weeks; or cetuximab plus CAPOX (oxaliplatin 130 mg/m(2) day 1; capecitabine 1,000 mg/m(2) twice daily day 1 through 14, every 3 weeks). The primary study end point was objective response rate (ORR).

RESULTS

In the intention-to-treat patient population (n = 177), ORR was 46% (95% CI, 35 to 57) for CAPIRI plus cetuximab versus 48% (95% CI, 37 to 59) for CAPOX plus cetuximab. Analysis of the KRAS gene mutation status was performed in 81.4% of the intention to treat population. Patients with KRAS wild-type in the CAPIRI plus cetuximab arm showed an ORR of 50.0%, a PFS of 6.2 months and an OS of 21.1 months. In the CAPOX plus cetuximab arm, an ORR of 44.9%, a PFS of 7.1 months and an OS of 23.5 months were observed. While ORR and PFS were comparable in KRAS wild-type and mutant subgroups, a trend toward longer survival was associated with KRAS wild-type. Both regimens had manageable toxicity profiles and were safe.

CONCLUSION

This randomized trial demonstrates that the addition of cetuximab to CAPIRI or CAPOX is effective and safe in first-line treatment of mCRC. In the analyzed regimens, ORR and PFS did not differ according to KRAS gene mutation status.

DOG1 for the diagnosis of gastrointestinal stromal tumor (GIST): Comparison between 2 different antibodies

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal neoplasm of the gastrointestinal tract. Discovered on GIST-1 (DOG1) is a recently described protein expressed in GISTs irrespective of mutation status. The aim of this study was to investigate the immunohistochemical expression of DOG1 using 2 different monoclonal antibodies (DOG1.1 and the commercially available K9 antibody) in 668 GIST cases and to compare the results with the expression of KIT. DOG1 and KIT expression also were studied in most human normal tissues and several nonmesenchymal and mesenchymal tumors other than GIST. KIT was expressed in 643 (96.3%) GISTs. DOG1.1 and K9 were positive in 538 (80.5%) and 642 (96.1%) GIST cases, respectively. In 25 (3.7%) KIT-negative GIST cases, DOG1 was expressed in 5 (20.0%) and 19 (76.0%) using DOG1.1 and K9 antibodies, respectively. Only 0.9% of GISTs were negative for KIT, DOG1.1, and K9. Most normal human tissues did not reveal KIT and DOG1 expression. DOG1.1 was positive in only 2 of 57 synovial sarcomas and 1 of 61 soft tissue leiomyosarcomas. K9 was positive in 5 of 57 synovial sarcomas, 1 of 14 angiosarcomas, 1 of 61 soft tissue leiomyosarcomas, 3 of 4 adenoid cystic carcinomas of the head and neck, and in myoepithelial cells of 9 of 11 fibroadenomas of the breast. In conclusion, the commercially available K9 is of great utility for the diagnosis of most KIT-negative GISTs, and the combination of both KIT and K9 antibody in a panel of immunohistochemistry can define the diagnosis of GIST in more than 99% of cases.