Nov 17 (Reuters) - Merck ( MRK ) said on Monday it

expects a non-risk adjusted commercial opportunity in excess of

$5 billion from Cidara Therapeutics' ( CDTX ) experimental flu

drug.

The drugmaker struck a deal worth nearly $9.2 billion last

week to acquire Cidara to gain access to the long-acting

antiviral drug, CD388, currently in late-stage trial.