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:

Comparison of splicing factor 3b inhibitors in human cells. Name your splice: FR901464 analogues and herboxidiene inhibit constitutive splicing, most likely by inhibiting spliceosomal subunit SF3b. A parallel comparison of these compounds in a cell-based assay system showed meayamycin B as the most potent splicing inhibitor among these small molecules.
{"Chemical": ["meayamycin B", "FR901464", "herboxidiene"]}