Effect of Tucatinib on Cardiac Repolarization in Healthy Volunteers.

BACKGROUND AND OBJECTIVE: Tucatinib is a selective tyrosine kinase inhibitor of the human epidermal growth factor receptor 2 (HER2) approved to treat metastatic HER2-positive breast and colorectal cancers. The International Council for Harmonisation of Technical Requirements for Human Use (ICH) E14 guideline mandates that new drugs are assessed for potential effects on cardiac repolarization through electrocardiogram (ECG) evaluation in a QT/corrected QT (TQT) study. METHODS: We evaluated the effect of tucatinib on cardiac repolarization in healthy volunteers in a phase I, randomized, partially double-blind, placebo-and positive-controlled three-period crossover study. The primary endpoint was the placebo-corrected change from baseline in QT interval values, corrected for heart rate using Fridericia's method (ΔΔQTcF). RESULTS: After achieving steady-state tucatinib exposures with 300 mg twice daily, the observed ΔΔQTcF ranged from -2.9 msec at 2 hours post-dose to 0 msec at 4 hours post-dose. The upper bound of the 90% confidence interval (CI) was below 5 ms at all post-dose timepoints. Assay sensitivity was confirmed as the lower bound of the 90% CI and was >5 ms following moxifloxacin dosing. As the mean ΔΔQTcF of tucatinib was predicted to be -  1.80 ms (90% CI -  3.90, 0.30) at clinically relevant tucatinib concentrations (511 ng/mL), an effect of tucatinib on QTcF exceeding 10 ms was excluded within observed ranges of tucatinib (up to ~1000 ng/mL). Tucatinib had no clinically relevant effect on heart rate or cardiac conduction. The safety profile of tucatinib was manageable after multiple doses. CONCLUSION: Tucatinib had no clinically relevant effects on studied ECG parameters. This study constitutes a clearly negative TQT study per ICH E14 guidance. CLINICAL TRIAL REGISTRATION: This trial (NCT03777761) was registered on 17 December 2018.

The Pharmacokinetics and Safety of Tucatinib in Volunteers with Hepatic Impairment.

BACKGROUND AND OBJECTIVE: Tucatinib, a highly selective tyrosine kinase inhibitor of the human epidermal growth factor receptor 2 (HER2) approved for HER2-positive metastatic breast cancer, is cleared by hepatic metabolism and subsequent biliary excretion. Liver disease can alter drug disposition and pharmacokinetics (PK). The objective of this study is to characterize PK and safety of tucatinib in volunteers with hepatic impairment. METHODS: This Phase 1 study compared the PK and safety of a single 300-mg oral dose of tucatinib in volunteers with mild, moderate, and severe hepatic impairment (Child-Pugh A/B/C) to healthy volunteers matched for sex, age, and body mass index. Pharmacokinetic parameters were determined for tucatinib and its predominant metabolite ONT-993. RESULTS: Compared with healthy volunteers, tucatinib exposure was similar in volunteers with mild impairment and increased in those with moderate or severe impairment without reaching statistical significance. Respective fold increases in geometric mean ratios for AUC0-t and AUC0-∞ were 1.13 and 1.15 in moderate impairment, and 1.43 and 1.61 in severe impairment compared with healthy volunteers. Three treatment-emergent adverse events (nausea, dermatitis, and increased transaminases) were reported in three volunteers and showed no obvious association with hepatic impairment status. CONCLUSION: The 1.61-fold geometric mean ratio AUC0-∞ increase in volunteers with severe hepatic impairment supports the recommendation in the tucatinib prescribing information to reduce the dose from 300 mg twice daily to 200 mg twice daily in patients with severe impairment; no dose adjustment is recommended for patients with mild or moderate hepatic impairment. This trial (NCT03722823) was registered on October 29, 2018.

Evaluation of Safety and Clinically Relevant Drug-Drug Interactions with Tucatinib in Healthy Volunteers.

BACKGROUND AND OBJECTIVE: Tucatinib is approved for treatment of human epidermal growth factor receptor 2-positive metastatic breast cancer. Understanding potential drug-drug interactions (DDIs) informs proper dosing when co-administering tucatinib with other therapies. The aim of this study was to evaluate DDIs between tucatinib and metabolizing enzymes and transporters in healthy volunteers. METHODS: Parts A-C assessed the impact of itraconazole (cytochrome P450 [CYP] 3A4 inhibitor), rifampin (CYP3A4/CYP2C8 inducer), or gemfibrozil (CYP2C8 inhibitor) on the pharmacokinetics of a single 300 mg dose of tucatinib administered orally and its primary metabolite, ONT-993. Parts D and E assessed the effect of steady-state tucatinib on the pharmacokinetics of repaglinide (CYP2C8 substrate), tolbutamide (CYP2C9 substrate), midazolam (CYP3A4 substrate), and digoxin (P-glycoprotein substrate). RESULTS: Tucatinib area under the concentration-time curve from time 0 extrapolated to infinity (AUC0-inf) increased by ~ 1.3- and 3.0-fold with itraconazole and gemfibrozil, respectively, and decreased by 48% with rifampin, indicating that tucatinib is metabolized primarily by CYP2C8, and to a lesser extent via CYP3A. Tucatinib was a strong inhibitor of CYP3A (midazolam AUC0-inf increased 5.7-fold), a weak inhibitor of CYP2C8 and P-glycoprotein, and had no impact on CYP2C9-mediated metabolism in humans. Tucatinib was well tolerated, alone and with co-administered drugs. CONCLUSION: The potential DDIs identified here may be mitigated by avoiding concomitant use of tucatinib with strong CYP3A inducers, moderate CYP2C8 inducers, CYP3A substrates with a narrow therapeutic window (modifying substrate dose where concomitant use is unavoidable), and strong CYP2C8 inhibitors (decreasing tucatinib dose where concomitant use is unavoidable), or by reducing the dose of P-glycoprotein substrates with a narrow therapeutic window. TRIAL REGISTRATION: This trial (NCT03723395) was registered on October 29, 2018.

Tucatinib Inhibits Renal Transporters OCT2 and MATE Without Impacting Renal Function in Healthy Subjects.

Tucatinib is a potent tyrosine kinase inhibitor selective for human epidermal growth factor receptor 2 (HER2) approved by the US Food and Drug Administration for the treatment of HER2-positive metastatic breast cancer and in development for other HER2-positive solid tumors. Modest, reversible serum creatinine (SCr) elevations have been observed in tucatinib clinical trials. SCr is conveyed by the renal drug transporters organic cation transporter 2 (OCT2) and multidrug and toxin extrusion protein 1 (MATE1) and 2-K (MATE2-K) and can increase in the presence of inhibitors of these transporters. In vitro, tucatinib inhibited OCT2-, MATE1-, and MATE2-K-mediated transport of metformin, with IC50 values of 14.7, 0.340, and 0.135 µM, respectively. Tucatinib also inhibited OCT2- and MATE1-mediated transport of creatinine, with IC50 values of 0.107 and 0.0855 µM, respectively. A phase 1 study with metformin administered orally in the absence and presence of tucatinib was conducted in 18 healthy subjects. Renal function was assessed by measuring glomerular filtration rate (GFR; based on iohexol plasma clearance) and endogenous markers (SCr, cystatin C-based estimated glomerular filtration rate [eGFR]) with and without tucatinib. Metformin exposure increased (1.4-fold) and renal clearance decreased (29.99-17.64 L/h) with tucatinib, with no effect on metformin maximum concentration. Creatinine clearance transiently decreased 23% with tucatinib. GFR and eGFR, which are unaffected by OCT2 and/or MATE1/2-K transport, were unchanged with tucatinib. These data demonstrate that tucatinib inhibits OCT2- and MATE1/2-K-mediated tubular secretion of creatinine, which may manifest as mild SCr elevations that are not indicative of renal impairment.

Ultrasonic, bipolar, and integrated energy devices: comparing heat spread in collateral tissues.

BACKGROUND: Integrated devices incorporating ultrasonic and bipolar technology have been used in laparoscopic surgery, however, are not yet incorporated into open operations. Here, we compare thermal spread and recurrent laryngeal nerve (RLN) functional data of the integrated THUNDERBEAT Open Fine Jaw device, the bipolar Ligasure Small Jaw, and the ultrasonic Harmonic Focus for open thyroidectomy. MATERIALS AND METHODS: The three energy devices were compared in a live porcine model using three tissue types including liver, muscle, and thyroid. The devices were fired three times on each energy setting, and the thermal spread was measured by thermocouples that were inserted in surrounding tissues at 1-mm intervals. To determine RLN injury, devices were fired at successive 1-mm increments from the RLN until the monitor signal was lost. RESULTS: When comparing heat generated across these devices at 1 mm, the peak temperature (Celsius) reached in liver tissue was observed with the ultrasonic device (115.4 ± 86.7), in muscle tissue with the integrated device (104.2 ± 82.1), and in thyroid with the bipolar device (81.4 ± 41.3). Temperatures generated at individual settings on each device were similar (P = 0.11-0.81). RLN injury occurred after firing on manually approximated tissue 1-mm away from the RLN for all devices; however, there was no signal loss at ≥2 mm. CONCLUSIONS: Heat transfer was similar among all devices with the exception of the ultrasonic device when used in the liver, which showed higher temperatures. Liver tissue showed the most consistent results. RLN injury did not occur if the devices were fired on manually approximated tissue ≥2 mm from the nerve.

Incidence, Risk Factors, and Clinical Outcomes of Incidental Parathyroidectomy During Thyroid Surgery.

BACKGROUND: The reported rate of incidental parathyroidectomy (IP) during thyroid surgery is between 5.2 and 21.6 %. Current literature reports wide discrepancy in incidence, risk factors, and outcomes. Thus study was designed to address definitively the topic of IP and identify associated risk factors and clinical outcomes with this multi-institutional study. METHODS: This retrospective cohort study included 1767 total thyroidectomies that occurred between 1995 and 2014 at two academic centers. Pathologic reports were reviewed for the presence of unintentionally removed parathyroid glands. Demographics, potential risk factors, and postoperative calcium levels were compared with matched control group. Logistic regression, t tests, and Chi squared tests were used when appropriate. RESULTS: IP occurred in 286 (16.2 %) of thyroidectomies. Risk factors for IP were: malignancy, neck dissection, and lymph node metastases (p = 0.005, <0.001, and <0.001). Fifty-three (19.2 %) of IPs were intrathyroidal. Those with IP were more likely to have postoperative biochemical (65.6 vs. 42.0 %; p < 0.001) and symptomatic (13.4 vs. 8.1 %; p = 0.044) hypocalcemia than controls. The number of parathyroids identified intraoperatively was inversely correlated with the number of parathyroid glands in the specimen (p < 0.001). CONCLUSIONS: Our findings indicate that malignancy, lymph node dissection, and metastatic nodal disease are risk factors for IP. Patients with IP were more likely to have postoperative biochemical and symptomatic hypocalcemia than controls, showing that there is a physiologic consequence to IP. Additionally, intraoperative surgeon identification of parathyroid glands results in a lower incidence of IP, highlighting the importance of awareness of parathyroid anatomy during thyroid surgery.

Radiation-Induced Differentiated Thyroid Cancer Is Associated with Improved Overall Survival but Not Thyroid Cancer-Specific Mortality or Disease-Free Survival.

BACKGROUND: Radiation is a well-described risk factor for differentiated thyroid carcinoma (DTC). Although the natural history of DTC following nuclear disasters and in healthcare workers with chronic radiation exposure (RE) has been described, little is known about DTC following short-term exposure to therapeutic medical radiation for benign disease. This study compares DTC morphology and outcomes in patients with and without a prior history of therapeutic external RE. METHODS: A retrospective review was performed of patients with DTC treated at The University of Chicago between 1951 and 1987, with a median follow-up of 27 years (range 0.3-60 years). Patients were classified as either having (RE+) or not having (RE-) a history of therapeutic RE. Variables examined included sex, age at RE, dose of RE, indication for RE, DTC histology, and outcome. Morphology was determined by blinded retrospective review of all available histologic slides. Outcomes were assessed using Cox proportional hazards model and Kaplan-Meier curves. RESULTS: Of 257 DTC patients, 165 (64%) were RE- and 92 (36%) were RE+, with males comprising a greater proportion of the RE+ group (43.5% vs. 27.3%; p = 0.01). A total of 94.2% of DTC cases were classic papillary cancers; histology did not differ between RE+ and RE- cohorts (p = 0.73). RE was associated with an increased median overall survival (OS; 43 years vs. 38 years; hazard ratio [HR] = 0.55 [confidence interval (CI) 0.34-0.89]; p = 0.01). Survival for males in the RE- group was significantly worse than it was for RE- females (HR = 1.78 [CI 1.05-3.03]; p = 0.03) or RE+ males (HR = 2.98 [CI 1.39-6.38]; p = 0.01). Recurrence did not differ between the RE+ and RE- groups (HR = 0.85 [CI 0.52-1.41]; p = 0.54), nor did DTC-specific mortality (HR = 0.54 [CI 0.21-1.37]; p = 0.20). CONCLUSIONS: While DTC following RE has historically been considered a more aggressive variant than DTC in the absence of RE, the present data indicate that RE+ DTC is associated with better OS than RE- DTC, especially for males. Additionally, recent reports are confirmed of equivalent rates of thyroid cancer recurrence. These results warrant further investigation into the factors underlying this unexpected finding.

Thyroidectomy in a two-year old for graves' disease.

INTRODUCTION: The most common cause of hyperthyroidism in children is graves' disease - an autoimmune disorder in which antibodies stimulate the thyrotropin receptor to signal growth thyroid gland by increasing thyroid hormone synthesis and release. It can be treated with medical therapy, radioactive iodine, or surgery. PRESENTATION OF CASE: JD was a two year old male who presented with severe diarrhea and diffuse neck enlargement. Laboratory work up was consistent with graves' disease. DISCUSSION: Despite maximal outpatient and inpatient treatment with methimazole, atenolol, prednisone, and SSKI, he suffered persistent thyrotoxicosis. He underwent near-total thyroidectomy without complication. CONCLUSION: This case is notable as it may represent the youngest patient in the literature who has undergone thyroidectomy for graves' disease.