Activity of erlotinib when dosed below the maximum tolerated dose for EGFR-mutant lung cancer: Implications for targeted therapy development

Therapeutic Drug Monitoring of Kinase Inhibitors in Oncology

Although kinase inhibitors (KI) frequently portray large interpatient variability, a 'one size fits all' regimen is still often used. In the meantime, relationships between exposure-response and exposure-toxicity have been established for several KIs, so this regimen could lead to unnecessary toxicity and suboptimal efficacy. Dose adjustments based on measured systemic pharmacokinetic levels-i.e., therapeutic drug monitoring (TDM)-could therefore improve treatment efficacy and reduce the incidence of toxicities. Therefore, the aim of this comprehensive review is to give an overview of the available evidence for TDM for the 77 FDA/EMA kinase inhibitors currently approved (as of July 1st, 2023) used in hematology and oncology. We elaborate on exposure-response and exposure-toxicity relationships for these kinase inhibitors and provide practical recommendations for TDM and discuss corresponding pharmacokinetic targets when possible.

Management of diarrhea induced by EGFR-TKIs in advanced lung adenocarcinoma

The identification of Epidermal Growth Factor Receptor (EGFR) mutations in lung adenocarcinoma has facilitated the development of personalized medicine based on oncogenic drivers. EGFR-Tyrosine Kinase Inhibitors (TKIs) are part of the targeted therapy; they impede the phosphorylation of the intracellular tyrosine kinase component of EGFR and consequently block signal transduction pathways. These drugs inhibit the proliferation and survival of tumor cells, leading to long-term progression-free survival and overall survival. Diarrhea is one of the most frequent adverse events associated with EGFR-TKIs, affecting at least 18% of patients and reaching up to 95% in some cases. Diarrhea should be managed carefully given its association with important complications, treatment interruptions, and dose reductions. Moreover, nutritional status and quality of life (QoL) can deteriorate due to severe diarrhea. Changes in diet, such as increment of fiber, supplementation with glutamine, and use of probiotics, may contribute to a decrease in the incidence of diarrhea. Improving the control of diarrhea can provide a significant benefit to the QoL of patients.

Prospective evaluation of the relationship between response and exposure of total and unbound erlotinib in non-small cell lung cancer patients

PURPOSE

To evaluate the relationship between treatment efficacy and exposure of total and unbound erlotinib in patients with non-small cell lung cancer (NSCLC) harboring epidermal growth factor receptor (EGFR)-activating mutations.

PATIENTS AND METHODS

EGFR-tyrosine kinase inhibitor naïve NSCLC patients were enrolled, and erlotinib was started at 150 mg/day. Total and unbound exposure of erlotinib were prospectively evaluated.

RESULTS

Of the 70 enrolled patients, 61 had EGFR-activating mutations (30 patients with exon 19 deletions, 31 patients with L858R). The median area under the concentration-time curve from 0 to 24 h (AUC_0-24) of total and unbound erlotinib on day 1 was 37,004 ng·h/mL (range, 9683-63,257 ng·h/mL) and 2338 ng·h/mL (581-5904 ng·h/mL), respectively. The median progression-free survival (PFS) was 10.9 months, and PFS did not differ between each tertile of total and unbound AUC_0-24 on day 1 in 59 patients with EGFR-activating mutations. The worst grade of skin toxicities was significantly correlated with total trough concentration at steady state (C_trough,ss) at each visit for 3 months after the initiation of erlotinib treatment (P < 0.0001). Total and unbound C_trough,ss on day 7-15 in 20 patients whose dose was reduced due to intolerable toxicities was significantly higher than those in 48 patients whose dose was unchanged for 3 months (P = 0.0046, 0.0008).

CONCLUSION

The lack of relationship between efficacy and exposure of total and unbound erlotinib demonstrates that the standard dose of 150 mg/day is sufficient for the treatment of NSCLC harboring EGFR-activating mutations, despite wide inter-individual variability in exposure and dose reduction.

CLINICAL TRIALS REGISTRATION NUMBER

UMIN000012862.

Optimized Dosing: The Next Step in Precision Medicine in Non-Small-Cell Lung Cancer

In oncology, and especially in the treatment of non-small-cell lung cancer (NSCLC), dose optimization is often a neglected part of precision medicine. Many drugs are still being administered in "one dose fits all" regimens or based on parameters that are often only minor determinants for systemic exposure. These dosing approaches often introduce additional pharmacokinetic variability and do not add to treatment outcomes. Fortunately, pharmacological knowledge is increasing, providing valuable information regarding the potential of, for example, therapeutic drug monitoring. This article focuses on the evidence for the most promising and easily implemented optimized dosing approaches for the small-molecule inhibitors, chemotherapeutic agents, and monoclonal antibodies as treatment options currently approved for NSCLC. Despite limitations such as investigations having been conducted in oncological diseases other than NSCLC or the retrospective origin of many analyses, an alternative dosing regimen could be beneficial for treatment outcomes, prescriber convenience, or financial burden on healthcare systems. This review of the literature provides recommendations on the implementation of dose optimization and advice regarding promising strategies that deserve further research in NSCLC.

Evaluating the utility of therapeutic drug monitoring in the clinical use of small molecule kinase inhibitors: a review of the literature

Introduction: Orally administered small molecule kinase inhibitors (KI) are a key class of targeted anti-cancer medicines that have contributed substantially to improved survival outcomes in patients with advanced disease. Since the introduction of KIs in 2001, there has been a building body of evidence that the benefit derived from these drugs may be further enhanced by individualizing dosing on the basis of concentration.Areas covered: This review considers the rationale for individualized KI dosing and the requirements for robust therapeutic drug monitoring (TDM). Current evidence supporting TDM-guided KI dosing is presented and critically evaluated, and finally potential approaches to address translational challenges for TDM-guided KI dosing and alternate approaches to support individualization of KI dosing are discussed.Expert opinion: Intuitively, the individualization of KI dosing through an approach such as TDM-guided dosing has great potential to enhance the effectiveness and tolerability of these drugs. However, based on current literature evidence it is unrealistic to propose that TDM-guided KI dosing should be routinely implemented into clinical practice.

Efficacy and Tolerability of Erlotinib 100 mg/d vs. Gefitinib 250 mg/d in EGFR-Mutated Advanced Non-small Cell Lung Cancer (E100VG250): An Open-Label, Randomized, Phase 2 Study

Background: Erlotinib-based combination therapy leads to increased efficacy but also toxicity for EGFR-mutated NSCLC. Reducing the dose of erlotinib could improve treatment tolerability, but few evidences are available regarding its efficacy at reduced dose. This randomized phase-2 study intends to compare the efficacy and tolerability between lower dose erlotinib (100 mg/d) and standard dose gefitinib (250 mg/d) in EGFR-mutated NSCLC. Methods: Patients with EGFR-mutated advanced NSCLC were randomized at 1:1 ratio to receive erlotinib 100 mg/d or gefitinib 250 mg/d until disease progression or unacceptable toxicity. The primary endpoint was disease control rate (DCR). Results: Between April 2013 and September 2018, 171 patients were randomized to receive erlotinib (n = 85) and gefitinib (n = 86); 74 in the erlotinib group and 83 in the gefitinib group were include in analysis. DCR with erlotinib and gefitinib were 91% [95% CI 81.7-95.3] and 93% [85.1-96.6], respectively (P = 0.613). Response rate was 62% [50.8-72.4] in the erlotinib group and 53% [42.4-63.4] in the gefitinib group (P = 0.247). No significant difference was observed between erlotinib and gefitinib in median progression-free survival [10.1 vs. 11.3 months, HR = 1.295 [0.893-1.879], P = 0.171] and median overall survival [26.6 vs. 28.7 months, HR = 0.999 [0.637-1.569], P = 0.998]. Subgroup analyses by line of treatment, EGFR subtypes and status of central nervous system (CNS) metastasis found similar results. More toxicity [any-grade, 80 [96%] vs. 66 [89]; grade 3-4, 11 [13%] vs. 4 [5%]] and toxicity-related discontinuation [10 [12%] vs. 3 [4%]] occurred with gefitinib compared with erlotinib. But no significant difference was observed. Conclusion: Lower dose erlotinib (100 mg/d) achieved comparable efficacy compared with standard dose gefitinib (250 mg/d) in EGFR-mutated NSCLC. Clinical Trial Registration: https://clinicaltrials.gov, identifier: NCT01955421.

Clearing of circulating tumour DNA predicts clinical response to first line tyrosine kinase inhibitors in advanced epidermal growth factor receptor mutated non-small cell lung cancer

OBJECTIVES

Epidermal growth factor receptor (EGFR) mutations confer sensitivity to tyrosine kinase inhibitors (TKIs) in non-small cell lung cancer (NSCLC). However, a subset of patients has limited or no response. We investigated the initial dynamics of EGFR mutations detected in circulating tumour DNA (ctDNA) during treatment as a predictive marker of outcome.

METHODS

A total of 225 patients with advanced EGFR mutated NSCLC were included for consecutive blood sampling in this prospective multicentre study. Out of these, 146 patients received first line TKI and had a baseline blood sample available for EGFR mutation testing with the Cobas® EGFR mutation test V2. For examinations on clearing and clinical outcome, 98 patients who had detectable ctDNA at baseline and at least one follow-up blood sample were included.

RESULTS

For patients with EGFR mutations present in plasma at baseline, clearing of mutations from the blood during first line TKI served as a positive predictor for objective response rate (p = 0.0008), progression-free survival (PFS) (p < 0.0001) and overall survival (OS) (p < 0.0001). This was seen both for patients who cleared the ctDNA within the first 7 weeks of treatment and patients who cleared the ctDNA at a slower pace. Baseline mutation presence was a negative predictor for PFS (p = 0.0069) and OS (p = 0.0340).

CONCLUSION

The current study is the first to confirm, in a sizeable Caucasian cohort, that clearing of EGFR mutations predict outcome to first line TKI in patients with EGFR mutated NSCLC.

Difference in central nerve system metastasis during gefitinib or erlotinib therapy in patients with EGFR-mutated non-small cell lung cancer: a retrospective study

Background

Central nervous system (CNS) metastasis is a poor prognostic factor in patients with advanced non-small cell lung cancer (NSCLC) harboring epidermal growth factor receptor (EGFR) mutation EGFR-mutant NSCLC and is associated with a deteriorated quality of life (QOL). Some clinical studies have suggested a possible difference in the incidence of CNS metastasis between EGFR-mutant NSCLC patients treated with gefitinib and erlotinib, both of which are classified as first-generation EGFR tyrosine kinase inhibitors (TKIs). However, the difference in the incidence of CNS metastasis between patients receiving these two drugs has not yet been sufficiently well investigated. We analyzed the frequency of occurrence/progression of CNS metastasis in EGFR-mutant NSCLC patients treated with erlotinib and gefitinib as the first-line treatment.

Methods

We analyzed the incidence of CNS metastasis, frequency of progression of CNS metastasis and the treatment outcomes in EGFR-mutant patients who received gefitinib or erlotinib as the first-line EGFR-TKI treatment. CNS progressive disease (PD) was defined as progression of CNS metastasis during EGFR-TKI treatment. We also evaluated the progression-free survival (PFS), CNS-PFS, and overall survival (OS) of the patients who received each of the two drugs.

Results

A total of 170 patients were enrolled in the study, of which 144 had received gefitinib, and 26 had received erlotinib. The frequency of CNS PD in the erlotinib group tended to be lower than that in the gefitinib group (11.5% vs. 29.9%, P=0.06). In patients with no existing CNS metastasis at the start of the EGFR-TKI treatments, the incidence of CNS PD was significantly lower in the erlotinib group than that in the gefitinib group (4.8% vs. 24.5%, P=0.04). A re-biopsy after failure of EGFR-TKI treatment was performed in 48 patients. The incidence of EGFR T790M tended to be higher among patients with CNS PD than in those without CNS PD, although the difference was not statistically significant (66.7% vs. 40.4%; P=0.23).

Conclusions

The incidence of progression of CNS metastasis during erlotinib treatment was lower than that during gefitinib treatment. In addition, the difference in the incidence in patients without existing CNS metastasis at the time of start of EGFR-TKI treatment was significantly lower in the patients treated with erlotinib than in those treated with gefitinib.

The clinical efficacy of Afatinib 30 mg daily as starting dose may not be inferior to Afatinib 40 mg daily in patients with stage IV lung Adenocarcinoma harboring exon 19 or exon 21 mutations

Background

Afatinib is a second-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI). Compared to cytotoxic chemotherapy, afatinib has been shown to have better efficacy in the treatment of non-small cell lung cancer harboring EGFR mutations. However, 40 mg daily as the initial dose is often accompanied by serious adverse drug reactions (ADRs) and 28 to 53.3% of patients required a dose reduction. No previous study has compared the clinical efficacy and ADRs of different initial doses (40 mg vs. 30 mg daily) of afatinib in lung cancer treatment.

Methods

Patients with stage IV lung adenocarcinoma diagnosed and treated in two Kaohsiung Medical University-affiliated hospitals in Taiwan between May 2014 and August 2016 were identified and followed until December 2016. Demographic characteristics, responses, progression-free survival (PFS), overall survival (OS), and ADRs were recorded.

Result

A total of 48 patients with stage IV lung adenocarcinoma harboring susceptible EGFR mutations who received afatinib as their first-line therapy were enrolled. Patients using 30 mg daily as the initial dose tended to be older and female and have a smaller body size. The patients using 30 mg of afatinib daily as their initial dose had a similar response rate to those receiving 40 mg daily (76% vs. 95%, p = 0.0862) and the same disease control rate (100% vs. 100%, p = 0.1486). The PFS was similar between the patients receiving 30 mg or 40 mg of afatinib daily (median PFS: 469 vs. 443 days, log-rank p = 0.8418). Patients receiving 30 mg daily had a significantly lower incidence of diarrhea than those using 40 mg daily (41% vs. 100%, p < 0.0001).

Conclusion

An initial afatinib dose of 30 mg daily had similar response and progression-free survival rates as an initial dose of 40 mg daily, but resulted in fewer serious ADRs in this study.

Afatinib Therapy for Brain Metastases Aggravated by a Reduction in the Dose of Erlotinib Due to the Development of Hepatotoxicity

We report an 80-year-old woman with EGFR-mutant lung adenocarcinoma with multiple brain metastases (BMs). All lesions including BM showed a successful resolution after initiating daily 150 mg erlotinib. However, a grade 2 bilirubin-increase developed, and it was necessary to reduce the dose of erlotinib to 50 mg every other day, which aggravated BM. Switching erlotinib to afatinib led to the resolution of BM without an increase in the bilirubin level. Our results indicate that afatinib is an important treatment option when erlotinib-induced hepatotoxicity develops, regardless of the patients' age. Particularly in those patients with BM, switching to afatinib may be preferable to reducing the dose of erlotinib.

Paradigm shift of therapeutic management of brain metastases in EGFR-mutant non-small cell lung cancer in the era of targeted therapy

Non-small cell lung cancer (NSCLC) patients with epidermal growth factor receptor (EGFR) mutations commonly present brain metastases (BM) at the time of NSCLC diagnosis or during the clinical course. Conventionally, the prognosis of BM has been extremely poor, but the advent of EGFR-tyrosine kinase inhibitors (TKIs) has drastically improved the prognosis in these patients. Despite the presence of the blood-brain barrier, EGFR-TKIs have dramatic therapeutic effects on both BM and extracranial disease. In addition, recent systemic chemotherapies reportedly play a role in controlling BM. These treatment modalities can potentially replace whole brain radiotherapy (WBRT) to prevent or delay neurocognitive decline. Therefore, how to utilize these treatments is one issue. The other issue is what kind of treatment is best for recurrence after TKI therapy. Recent reports have shown a positive effect of a combination therapy of EGFR-TKI and radiotherapy on BM. Although neurocognitive decline is underscored when WBRT is considered, a survival benefit from WBRT has been proven especially in the potential long survivors with good prognostic index, especially disease-specific graded prognostic index (DS-GPA). In this review, treatment strategy including chemotherapeutic agents and radiotherapy is discussed in terms of risk-benefit balance in conjunction with DS-GPA.