Assessment of cabozantinib treatment on QT interval in a phase 3 study in medullary thyroid cancer: evaluation of indirect QT effects mediated through treatment-induced changes in serum electrolytes

RET kinase inhibitors for RET-altered thyroid cancers

Precision oncology has opened a new era in cancer treatment focused on targeting specific cellular pathways directly involved in tumorigenesis. The REarrangement during Transfection (RET) proto-oncogene is involved in the pathogenesis of various thyroid cancer subtypes. Mutations in RET give rise to both hereditary and sporadic medullary thyroid cancer (MTC). RET fusions are found in follicular cell-derived thyroid cancers (papillary, poorly differentiated, and anaplastic). Hence, drugs that block the RET tyrosine kinase receptor have been explored in the management of locally advanced or metastatic thyroid cancer. The multikinase inhibitors (MKIs) with nonselective RET inhibition are sorafenib, lenvatinib, vandetanib, cabozantinib, and sunitinib. Although the efficacy of these drugs varies, a major issue is the lack of specificity resulting in a higher rate of drug-related toxicities, leading to dose reduction, interruption, or discontinuation. Moreover, MKIs are subject to drug resistance by RET Val804 residue gatekeeper mutations. In phase I/II clinical studies, the highly selective first-generation RET inhibitors, selpercatinib and pralsetinib, demonstrate high efficacy in controlling disease even in the presence of gatekeeper mutations combined with greater tolerability. However, resistance mechanisms such as RET solvent front mutations (SFMs) have evolved in some patients, giving the need to develop the selective second-generation RET inhibitors. Although the approval of selpercatinib and pralsetinib in 2020 has profoundly benefited patients with RET-altered thyroid cancer, further research into optimal treatment strategies, mechanisms of drug resistance, long-term consequences of potent RET-inhibition, and development of more effective agents against emergent mutations are much needed.

Parent and Metabolite Concentration-QT Modeling to Evaluate QT-Interval Prolongation at Savolitinib Therapeutic Doses

Savolitinib is an oral, potent, and highly selective MET-tyrosine kinase inhibitor under investigation in various tumor types. A thorough QT study evaluated effects on QT interval after a 600-mg single savolitinib dose in healthy subjects. We report exposure-response (E-R) modeling from this study to characterize the effects of savolitinib and its metabolites, M2 and M3, on QTc changes. In a novel application, in vitro potencies against hERG current provided mechanistic support to model the metabolites' effects. The hERG IC50 estimates (95% CI) were 25.8 (22.2-29.9) and 22.6 (14.7-34.6) μM for parent and M2, respectively. The E-R was described by both linear and E_max models, with exposure captured by an active moiety that consisted of savolitinib and M2 concentrations, weighted by the hERG IC50 ratio (1.14). The maximal increase in ΔΔQTcF and EC50 estimates (95% CI) was 18.5 (9.2-27.7) ms and 5709 (2889-8529) nM, respectively. Ignoring M2 contribution resulted in under prediction of QTcF prolongation in the hypothetical case of inhibited M2 clearance; at 300 mg C_max, the mean (90% CI) of ∆∆QTcF was 9.0 (5.7-12.6) and 5.9 (2.9-8.9) ms using the hERG-informed and parent-only linear models, respectively. Simulations in normal setting confirmed modest QTcF prolongation with 600 mg, but not 300 mg. Using the linear model, the mean (90% CI) maximum ΔΔQTcF were 12.3 (8.6-16.2) and 5.5 (2.6-8.5) ms for 600 and 300 mg, respectively. Further clinical studies will monitor cardiac safety to assess the clinical significance of QT-interval prolongation with savolitinib.

Sensitivity and specificity of drug interaction databases to detect interactions with recently approved oral antineoplastics

Rationale:

Drug-drug interactions (DDIs) with oral antineoplastics (OAs) are of increasing concern given the rapid increase in OA approvals and use in cancer patients. A small pilot study of 20 DDIs with OAs showed significant variability in commonly used DDI screening databases in sensitivity of detecting potentially clinically relevant DDIs. This study builds upon that work by expanding the number of potential DDIs analyzed and including a specificity analysis.

Methods

Newly approved OAs from 2016 to May 2019 (n = 22) were included in this analysis. Prescribing information for each drug was reviewed. A list of explicit and theoretical drug interactions was created for each OA by the two investigators. A board-certified oncology pharmacist adjudicated all DDI pairs for potential clinical significance. In total, 229 DDI pairs were used to analyze sensitivity of 5 DDI databases (Lexicomp®, Micromedex®, Medscape, Eporactes®, & Drugs.com). Additionally, 64 “dummy” or false DDI pairs were created to analyze specificity. Sensitivity and specific were analyzed using Cochran’s Qtest, while accuracy was analyzed using chi-square test.

Results

There was significant variability among the databases with regards to sensitivity (p < 0.0001), specificity (p < 0.0001), and accuracy (p < 0.0001). In terms of accuracy (max score = 400), Lexicomp®(355), Epocrates® (344), and Drugs.com (352) scored higher than MicroMedex® (270) and Medscape (280).

Conclusions

Considerable variability exists among DDI screening databases with regards to OAs and potential drug interactions. Clinicians should be vigilant in both screening for DDIs with OAs and describing DDIs encountered in clinical practice.

Management of Adverse Events Associated with Cabozantinib Treatment in Patients with Advanced Hepatocellular Carcinoma

Cabozantinib is an oral multikinase inhibitor whose targets include vascular endothelial growth factor receptors, MET, and the TAM family of kinases (TYRO3, AXL, MER). Cabozantinib is approved for patients with advanced hepatocellular carcinoma who have been previously treated with sorafenib, based on improved overall survival and progression-free survival relative to placebo in the phase III CELESTIAL study. During CELESTIAL, the most common adverse events (AEs) experienced by patients receiving cabozantinib included palmar-plantar erythrodysesthesia, fatigue, gastrointestinal-related events, and hypertension. These AEs can significantly impact treatment tolerability and patient quality of life. However, AEs can be effectively managed with supportive care and dose modifications. During CELESTIAL, more than half of the patients receiving cabozantinib required a dose reduction, while the rate of treatment discontinuation due to AEs was low. Here, we review the safety profile of cabozantinib and provide guidance on the prevention and management of the more common AEs, based on current evidence from the literature as well as our clinical experience. We consider the specific challenges faced by clinicians in treating this patient population and discuss factors that may affect exposure and tolerability to cabozantinib.

Management of treatment-related toxicities in advanced medullary thyroid cancer

PURPOSE OF REVIEW

Tyrosine kinase inhibitors (TKI), predominantly vandetanib and cabozantinib, are increasingly used for management of advanced medullary thyroid cancer. This review aims to discuss the major and serious adverse events associated with TKI.

RECENT FINDINGS

The choice of TKI depends on the patient's existing comorbidities. Patients who have long QT interval should avoid vandetanib and those at risk of gastrointestinal perforation should avoid cabozantinib. Hypertension is common during the first 3 months. Treatments include ACE inhibitors, calcium channel blockers (avoiding verapamil and diltiazem, which are CYP3A4 inhibitors), and beta blockers. Diuretics should be second line because of derangement of electrolytes, which may exacerbate QT interval. As nitric oxide (NO) blockade and ET1 are implicated in the mechanism of hypertension, nitrates and endothelin receptor antagonists may be used. Thromboembolism may require anticoagulation or revascularization procedures. Prolonged QT interval should be treated by dose interruption and reduction, correction of electrolytes, and avoidance of medications, which prolong QTc interval. Diarrhoea is managed symptomatically and with electrolyte replacement, dermatological adverse events with avoidance of exacerbating factors and topical therapies. Thyroid function should be monitored.

SUMMARY

Toxicities are common with TKI use, and management involves symptomatic treatment, avoidance of triggers, dose interruption, and dose reduction.

The effects of lapatinib on cardiac repolarization: results from a placebo controlled, single sequence, crossover study in patients with advanced solid tumors

PURPOSE

To evaluate the effect of lapatinib on the QTc interval and ECG parameters in patients with advanced solid tumors.

METHODS

This was a multicenter, placebo-controlled study in subjects with advanced solid tumors. Subjects were administered two doses of matching placebo on day 1, 12 h apart and one dose in the morning on day 2. Two doses of lapatinib 2000 mg were administered orally on day 3, 12 h apart and one dose in the morning on day 4. Twelve-lead digital ECGs were extracted from continuous Holter recordings at pre-specified time points over the 24-h period on days 2 and 4. Venous blood samples for lapatinib concentrations were obtained immediately following the ECGs.

RESULTS

A maximum mean baseline-adjusted, placebo time-matched increase in QTcF, (ddQTcF) in the evaluable, (EV) population (n = 37) of 8.8 ms (90% CI 4.1, 13.4) occurred approximately 10 h after the third lapatinib dose. These results were consistent with those in the pharmacodynamic, PD population, (n = 52) (ddQTcF = 7.9 ms; 90% CI 4.1, 11.7). No subject experienced QTcF increases from baseline of > 60 ms on lapatinib or placebo. The geometric mean lapatinib C_max of 3902 ng/mL was observed at 3.6 h post-dose.

CONCLUSIONS

These data show a relevant, treatment-related increase in QTcF after treatment with three doses of lapatinib 2000 mg. This study confirms the need for caution in patients with solid tumors treated with lapatinib, and who are concomitantly receiving drugs that are strong CYP3A inhibitors and/or prolong the QTc.

Cabozantinib as first-line treatment in advanced renal cell carcinoma: a profile of its use

Oral cabozantinib tablets (Cabometyx^®) are an important option for the treatment of advanced renal cell carcinoma (RCC). Cabozantinib is an anti-angiogenic agent and potently inhibits multiple tyrosine kinases, including those implicated in the development of RCC. The previously approved indication of cabozantinib tablets (i.e. treatment of advanced RCC following prior VEGF-targeted therapy) has been extended to include the first-line treatment of advanced RCC in treatment-naïve adults with intermediate or poor risk (EU) and all patients with advanced RCC (USA). These label extensions are based on the results of a randomized, open-label phase 2 trial, in which adults with metastatic RCC of poor or intermediate risk received targeted first-line treatment with cabozantinib or standard-of-care sunitinib. Relative to sunitinib, cabozantinib significantly prolonged median progression-free survival (primary endpoint; investigator and independent assessments), and increased the objective response rate (investigator assessment). The tolerability profile of cabozantinib is comparable to those of other tyrosine kinase inhibitors, with adverse events being manageable with medical intervention, dosage reductions, treatment interruption and/or permanent discontinuation.