The 27-year-old, who will train with the English outfit in Germany, played under current Brentford boss Uwe Rosler when the pair were at Viking Stavanger.
"He is going to join Brentford's training during a pre-season camp in Germany. We will negotiate the form of this potential transfer to England in the coming days," Sadek told CTK.
"Brentford's manager is very keen on taking Martin there because he coached him during a spell at Viking Stavanger."
Fillo has been capped three times by Czech Republic.