Association of the hemochromatosis gene with pazopanib-induced transaminase elevation in renal cell carcinoma.

BACKGROUND & AIMS: Pazopanib has demonstrated clinical benefit in patients with advanced renal cell carcinoma (RCC) and is generally well tolerated. However, transaminase elevations have commonly been observed. This 2-stage study sought to identify genetic determinants of alanine transaminase (ALT) elevations in pazopanib-treated white patients with RCC. METHODS: Data from two separate clinical studies were used to examine the association of genetic polymorphisms with maximum on-treatment ALT levels. RESULTS: Of 6852 polymorphisms in 282 candidate genes examined in an exploratory dataset of 115 patients, 92 polymorphisms in 40 genes were significantly associated with ALT elevation (p<0.01). Two markers (rs2858996 and rs707889) in the HFE gene, which are not yet known to be associated with hemochromatosis, showed evidence for replication. Because of multiple comparisons, there was a 12% likelihood the replication occurred by chance. These two markers demonstrated strong linkage disequilibrium (r(2)=0.99). In the combined dataset, median (25-75th percentile) maximum ALT values were 1.2 (0.7-1.9), 1.1 (0.8-2.5), and 5.4 (1.9-7.6)×ULN for rs2858996 GG (n=148), GT (n=82), and TT (n=1 2) genotypes, respectively. All 12 TT patients had a maximum ALT>ULN, and 8 (67%) had ALT≥3×ULN. The odds ratio (95% CI) for ALT≥3×ULN for TT genotype was 39.7 (2.2-703.7) compared with other genotypes. As a predictor of ALT≥3×ULN, the TT genotype had a negative predictive value of 0.83 and positive predictive value of 0.67. No TT patients developed liver failure. CONCLUSIONS: The rs2858996/rs707889 polymorphisms in the HFE gene may be associated with reversible ALT elevation in pazo-panib-treated patients with RCC.

Approval summary: sunitinib for the treatment of imatinib refractory or intolerant gastrointestinal stromal tumors and advanced renal cell carcinoma.

PURPOSE: To describe the Food and Drug Administration (FDA) review and approval of sunitinib malate (Sutent). Sunitinib received regular approval for the treatment of gastrointestinal stromal tumor (GIST) after disease progression or intolerance to imatinib mesylate (Gleevec). Additionally, sunitinib received accelerated approval for the treatment of advanced renal cell carcinoma. EXPERIMENTAL DESIGN: For the GIST indication, FDA reviewed data from a randomized, placebo-controlled trial with supportive evidence from a single-arm study. For the advanced renal cell carcinoma indication, FDA reviewed data from two single-arm studies of patients with cytokine-refractory metastatic renal cell carcinoma. RESULTS: In patients with imatinib refractory or intolerant GIST, time-to-tumor progression of sunitinib-treated patients was superior to that of placebo-treated patients. Median time-to-tumor progression of sunitinib-treated patients was 27.3 weeks, compared with 6.4 weeks for placebo-treated patients (P < 0.0001). Partial responses were observed in 6.8% of sunitinib-treated patients. In patients with metastatic renal cell carcinoma, partial responses were observed in 25.5% (95% confidence interval, 17.5, 34.9) and 36.5% (95% confidence interval, 24.7, 49.6) of patients treated with sunitinib. Median response durations were 27.1 and 54 weeks. The most common adverse events attributed to sunitinib included diarrhea, mucositis, skin abnormalities, and altered taste. Reductions in left ventricular ejection fraction and severe hypertension were also more common in sunitinib-treated patients. CONCLUSIONS: On January 26, 2006, the FDA approved sunitinib for the treatment of patients with imatinib refractory or intolerant GIST. Accelerated approval was granted for the treatment of advanced renal cell carcinoma.

Control of copper status for cancer therapy.

Copper is a trace element which is tightly regulated in mammals and lower animals. Disruptions of copper homeostasis in humans are rare and they cause serious disorders such as Wilson's disease and Menke's disease. Copper plays an important role in promoting physiological and malignant angiogenesis. Formation of new blood vessels by a tumor enables tumor growth, invasion, and metastasis are copper requiring processes. The copper chelator tetrathiomolybdate (TM), which quickly and effectively depletes copper stores, is under investigation as an anti-angiogenic agent. Promising results from in vitro experiments, in pre-clinical animal models, and in a phase I clinical trial have led to several phase II trials of TM in patients with advanced cancers.

Population pharmacokinetics of dabrafenib, a BRAF inhibitor: effect of dose, time, covariates, and relationship with its metabolites.

Dabrafenib is a BRAF kinase inhibitor indicated for the treatment of BRAF V600E mutation-positive melanoma. The population pharmacokinetics of dabrafenib, including changes over time and relevant covariates, were characterized based on results from four clinical studies using a nonlinear mixed effects model with a full covariate approach. Steady-state exposures of dabrafenib metabolites (hydroxy-, carboxy-, and desmethyl-dabrafenib) were characterized separately. The pharmacokinetics of dabrafenib were adequately described by non-inducible and inducible apparent clearance that increased with dose and time. Total steady-state clearance (CL/F) at 150 mg BID dose was 34.3 L/h. Based on the induction half-life (67 hours), steady state should be achieved within 14 days of dosing. Capsule shell was the most significant covariate (55%) while sex and weight had only a small impact on exposure (<20%). The AUC ratio (hypromellose:gelatin capsule) is predicted to be 1.80 and 1.42 following single and repeat dosing, respectively. Age, renal (mild and moderate), and hepatic (mild) impairment were not significant covariates. Steady-state pre-dose concentration (%CV) of dabrafenib and of hydroxy-, carboxy-, and desmethyl-dabrafenib at 150 mg BID were 46.6 ng/mL (83.5%), 69.3 ng/mL (64.1%), 3608 ng/mL (14.7%), and 291 ng/mL (17.2%), respectively. Capsule shell, concomitant medications, older age, and weight were predictors of metabolite exposure.

Phase II trial (BREAK-2) of the BRAF inhibitor dabrafenib (GSK2118436) in patients with metastatic melanoma.

PURPOSE: Dabrafenib (GSK2118436) is a potent inhibitor of mutated BRAF kinase. Our multicenter, single-arm, phase II study assessed the safety and clinical activity of dabrafenib in BRAF(V600E/K) mutation-positive metastatic melanoma (mut(+) MM). PATIENTS AND METHODS: Histologically confirmed patients with stage IV BRAF(V600E/K) mut(+) MM received oral dabrafenib 150 mg twice daily until disease progression, death, or unacceptable adverse events (AEs). The primary end point was investigator-assessed overall response rate in BRAF(V600E) mut(+) MM patients. Secondary end points included progression-free survival (PFS) and overall survival (OS). Exploratory objectives included the comparison of BRAF mutation status between tumor-specific circulating cell-free DNA (cfDNA) and tumor tissue, and the evaluation of cfDNA as a predictor of clinical outcome. RESULTS: Seventy-six patients with BRAF(V600E) and 16 patients with BRAF(V600K) mut(+) MM were enrolled onto the study. In the BRAF(V600E) group, 45 patients (59%) had a confirmed response (95% CI, 48.2 to 70.3), including five patients (7%) with complete responses. Two patients (13%) with BRAF(V600K) mut(+) MM had a confirmed partial response (95% CI, 0 to 28.7). In the BRAF(V600E) and BRAF(V600K) groups, median PFS was 6.3 months and 4.5 months, and median OS was 13.1 months and 12.9 months, respectively. The most common AEs were arthralgia (33%), hyperkeratosis (27%), and pyrexia (24%). Overall, 25 patients (27%) experienced a serious AE and nine patients (10%) had squamous cell carcinoma. Baseline cfDNA levels predicted response rate and PFS in BRAF(V600E) mut(+) MM patients. CONCLUSION: Dabrafenib was well tolerated and clinically active in patients with BRAF(V600E/K) mut(+) MM. cfDNA may be a useful prognostic and response marker in future studies.