Isocitrate Dehydrogenase-Mutated Cholangiocarcinoma: Natural History and Clinical Outcomes

Differential isocitrate dehydrogenase 1 and isocitrate dehydrogenase 2 mutation-related landscape in intrahepatic cholangiocarcinoma

BACKGROUND

Patients with intrahepatic cholangiocarcinoma (ICC) are prone to recurrence and poor survival. Targeted therapy related to isocitrate dehydrogenase (IDH) is an extremely important treatment. IDH1 and IDH2 mutations are generally thought to have similar effects on the tumor landscape. However, it is doubtful whether these 2 mutations have exactly the same effects on tumor cells and the tumor microenvironment.

METHODS

All collected tumor samples were subjected to simultaneous whole-exon sequencing and proteome sequencing.

RESULTS

IDH1 mutations accounted for 12.2%, and IDH2 mutations accounted for 5.5%, all missense mutations. Tumors with IDH mutations had lower proportions of KRAS and TP53 mutations. Mutated genes were obviously enriched in the kinase pathway in the tumors with IDH2 mutations. The signaling pathways were mainly enriched in the activation of cellular metabolic activities and an increase of inhibitory immune cells in the tumors with IDH mutations. Moreover, tumors had unique enrichment in DNA repair in IDH1 mutants and secretion of biological molecules in IDH2 mutants. Inhibitory immune cells might be more prominent in IDH2 mutants, and the expression of immune checkpoints PVR and HLA-DQB1 was more prominent in IDH1 mutants. IDH mutants were more related to metabolism-related and inflammation-immune response clusters, and some belonged to the DNA replication and repair cluster.

CONCLUSIONS

These results revealed the differential IDH1 and IDH2 mutation-related landscapes, and we have provided an important reference database to guide ICC treatment.

Targeted Therapies in Advanced Cholangiocarcinoma

Primary tumor resection and liver transplantation are the only curative treatment options for the management of cholangiocarcinoma (CCA). However, for patients with advanced or metastatic disease, palliative systemic therapy remains the only treatment option. The development of targeted therapeutics has begun to shift the treatment paradigm in CCA. Targets of interest in CCA include mutated isocitrate dehydrogenase-1 (mIDH-1), human epidermal growth factor receptor 2 (HER2) overexpression/amplification, and fibroblast growth factor receptor 2 (FGFR2) fusion, in addition to less frequently observed targets such as BRAF V600E, deficient mismatch repair/high microsatellite instability (dMMR/MSI-H), and high tumor mutation burden (TMB-H). These targets are observed in varying frequency among patients with intrahepatic CCA and extrahepatic CCA. Multiple novel therapies have been developed to exploit each of these targets, with some having received United States Food and Drug Administration approval for use in the second-line setting. In the current review, we discuss targets of interest in CCA and summarize current evidence evaluating available therapies directed at these targets.

Developments in FGFR and IDH inhibitors for cholangiocarcinoma therapy

INTRODUCTION

Cholangiocarcinoma (CCA) is an uncommon malignancy originating from epithelial cells of the biliary tract. Regardless of the site of origin within the biliary tree, CCAs are generally aggressive with a poor survival. Surgical resection remains the only chance for cure, yet a majority of patients are not surgical candidates at presentation. Unfortunately, systemic therapies are often ineffective and complicated by side effects. As such, more effective targeted therapies are required in order to improve survival.

AREA COVERED

Genetic analysis of CCA has allowed for a better understanding of the genomic landscape of CCA. Isocitrate dehydrogenase (IDH) and fibroblast growth factor receptor (FGFR) mutations have emerged as the most promising molecular targets for CCA. Inhibitors of IDH and FGFR have proven to have therapeutic benefit with an acceptable safety profile. However, patients often develop resistance rendering the therapy ineffective.

EXPERT OPINION

Understanding the molecular pathways of IDH and FGFR may lead to a better understanding of the mechanisms of resistance. Thus, novel therapies may be developed to improve the efficacy of these therapies. Developing novel biomarkers may improve patient selection and further enhance effectiveness of targeted therapies.

The clinical value of identifying genetic abnormalities that can be targeted in cholangiocarcinomas

INTRODUCTION

Cholangiocarcinomas (CCAs) are a heterogenous group of epithelial malignancies originating at any level of the biliary tree and are subdivided according to their location into intrahepatic (iCCA) and extrahepatic (eCCA).

AREAS COVERED

This review provides an updated analysis of studies of genetic characterization of CCA at the level of gene mutation profiling, copy number alterations and gene expression, with definition of molecular subgroups and identification of some molecular biomarkers and therapeutic targets.

EXPERT OPINION

With the development of genetic sequencing, several driver mutations have been identified and targeted as novel therapeutic approaches, including FGFR2, IDH1, BRAF, NTRK, HER2, ROS, and RET. Furthermore, identification of the cellular and molecular structure of the tumor microenvironment has contributed to the development of novel therapies, such as tumor immunotherapy. Combination therapies of chemotherapy plus targeted molecules or immunotherapy are under evaluation and offer the unique opportunity to improve the outcomes of CCA patients with advanced disease.

Clinical Outcomes After Progression on First-Line Therapies in IDH1 Mutated Versus Wild-Type Intrahepatic Cholangiocarcinoma Patients

BACKGROUND

Isocitrate dehydrogenase-1 (IDH1) mutations occur in a significant proportion of intrahepatic cholangiocarcinomas (iCCAs). No data are available regarding the prognostic impact of IDH1 mutations in advanced iCCA patients after progression on first-line therapies.

OBJECTIVE

We investigated the role of IDH1 mutation in advanced iCCA after progression on first-line therapies.

PATIENTS AND METHODS

After progression on first-line therapies for advanced iCCA, consecutive patients were retrospectively collected. The IDH1 status was tested at baseline. This analysis aimed to examine the association between the presence of IDH1 missense mutations and survival outcomes in patients with advanced iCCA treated with a second-line therapy.

RESULTS

The analysis included 119 patients; 56/119 (47%) were IDH1 mutated (IDH1m) and 63/119 (53%) were IDH1 wild type (IDH1 WT). At univariate analysis for overall survival (OS), the presence of IDH1 mutation was associated with a worse median OS (mOS; 8.2 vs. 14.1 months; hazard ratio [HR] 1.9, 95% confidence interval [CI] 1.2-3.0, p = 0.0047). Patients harboring IDH1 mutations showed a worse objective response rate (ORR) compared with patients without IDH1 mutation, whereas no significant differences in disease control rate (DCR) were found. Multivariate analysis confirmed IDH1 mutations as an independent negative prognostic factor for OS (HR 1.7, 95% CI 1.1-2.7, p = 0.0256). By evaluating only patients receiving FOLFOX as second-line therapy, no statistically significant differences were found in terms of both OS and PFS between IDH1m and IDH1 WT patients. In this subset of patients, those harboring an IDH1 mutation showed a worse ORR and DCR compared with those without. Finally, at univariate analysis for OS from third-line treatment, the presence of an IDH1 mutation was associated with a trend toward a worse mOS (6.0 vs. 11.9 months; HR 1.6, 95% CI 0.8-3.2, p = 0.25).

CONCLUSION

The present analysis constitutes the first evidence of a negative prognostic impact of IDH1 mutations in a cohort of patients treated after progression on first-line therapies in contrast to IDH1 inhibitors.

An evaluation of ivosidenib for the treatment of IDH1-mutant cholangiocarcinoma

INTRODUCTION

The combination of gemcitabine and cisplatin remains the standard-of-care first-line therapeutic option in patients with the unresectable disease based on the encouraging phase II and phase III trials (ABC-02). Recently, the combination of durvalumab, gemcitabine, and cisplatin has shown modest but statistically significant improvement in median overall survival (OS) as compared to that of the gemcitabine-cisplatin combination. Systemic therapy options such as the combination of 5-flurouracil (5-FU) and oxaliplatin (FOLFOX), 5-FU and liposomal irinotecan, and trifluridine/tipiracil (TAS-102) and irinotecan have shown encouraging results. Therapies targeting FGFR2 fusions/rearrangements, BRAF mutations, microsatellite high tumors, HER2 amplifications, and IDH mutations are currently being extensively evaluated in cholangiocarcinoma with encouraging results.

AREAS COVERED

We briefly discuss the recent advancements in targeted therapy approaches in cholangiocarcinoma with a special focus on ivosidenib.

EXPERT OPINION

Ivosidenib is an excellent option for IDH1-mutant cholangiocarcinoma that progressed on first-line chemotherapy given its excellent tolerability and median OS benefit. However, a few questions remain unanswered - sequencing of targeted therapies, benefits of combining targeted therapy with systemic chemotherapy or with other treatment modalities, such as immunotherapy and localized therapies.

Biology of IDH mutant cholangiocarcinoma

Isocitrate dehydrogenase 1 and 2 (IDH1 and IDH2) are the most frequently mutated metabolic genes across human cancers. These hotspot gain-of-function mutations cause the IDH enzyme to aberrantly generate high levels of the oncometabolite, R-2-hydroxyglutarate, which competitively inhibits enzymes that regulate epigenetics, DNA repair, metabolism, and other processes. Among epithelial malignancies, IDH mutations are particularly common in intrahepatic cholangiocarcinoma (iCCA). Importantly, pharmacological inhibition of mutant IDH (mIDH) 1 delays progression of mIDH1 iCCA, indicating a role for this oncogene in tumor maintenance. However, not all patients receive clinical benefit, and those who do typically show stable disease rather than significant tumor regressions. The elucidation of the oncogenic functions of mIDH is needed to inform strategies that can more effectively harness mIDH as a therapeutic target. This review will discuss the biology of mIDH iCCA, including roles of mIDH in blocking cell differentiation programs and suppressing antitumor immunity, and the potential relevance of these effects to mIDH1-targeted therapy. We also cover opportunities for synthetic lethal therapeutic interactions that harness the altered cell state provoked by mIDH1 rather than inhibiting the mutant enzyme. Finally, we highlight key outstanding questions in the biology of this fascinating and incompletely understood oncogene.