You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Sorafenib Hepatobiliary Disposition: Mechanisms of Hepatic Uptake and Disposition of Generated Metabolites. Sorafenib is an orally active tyrosine kinase inhibitor used in the treatment of renal and hepatocellular carcinoma. This study was designed to establish whether transport proteins are involved in the hepatic uptake of sorafenib, and to determine the extent of biliary excretion of sorafenib/metabolites in human hepatocytes. Initial uptake was assessed in freshly isolated, suspended human hepatocytes in the presence of inhibitors and modulators. [(14)C]Sorafenib (1 μM) uptake at 4°C was ~61-63% of the uptake at 37°C, suggesting a high degree of passive diffusion. Hepatocyte uptake of [(14)C]sorafenib was not Na(+)-dependent or influenced by the organic anion transporter 2 (OAT2) inhibitor ketoprofen. However, initial [(14)C]sorafenib hepatocyte uptake was reduced by 46 and 30% compared to control values in the presence of the organic anion transporting polypeptide (OATP) inhibitor rifamycin SV, and the organic cation transporter (OCT) inhibitor decynium 22, respectively. [(14)C]Sorafenib (0.5 to 5 μM) uptake was significantly higher in hOCT1-transfected CHO cells compared to mock cells, and inhibited by the general OCT inhibitor, MPP(+). OCT1-mediated uptake was saturable with a Km of 3.80 ± 2.53 μM and Vmax of 116 ± 42 pmol/mg/min. The biliary excretion index (BEI) and in vitro biliary clearance (Clbiliary) of sorafenib (1 μM) in sandwich-cultured human hepatocytes were low (~11% and 11 ml/min/kg, respectively). Results suggest that sorafenib uptake in human hepatocytes occurs via passive diffusion, and by OCT1 and a rifamycin-sensitive transporter. Sorafenib undergoes modest biliary excretion, predominantly as glucuronide conjugate(s).
{"Chemical": ["sorafenib", "MPP(+)", "rifamycin", "Sorafenib", "rifamycin SV", "decynium 22", "tyrosine", "[(14)C]sorafenib", "Na(+)", "[(14)C]Sorafenib", "ketoprofen"]}