Dear Yoyana,
At this moment iLINCS does not facilitate download of the whole collection of signatures and metadata, although you could use the API to download 1000 signatures at a time. We are planing of including batch downloads in the future, but don't have a timeline for when this will be implemented. Please note that LINCS signatures are available for download from LINCS Data Portal and GEO.
Best,
Mario
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Mario Medvedovic, iLINCS PI