The second-season chaser made his seasonal reappearance at Wetherby on Saturday when he finished third behind Proschema in the West Yorkshire Hurdle, a race Nicholls has used in the past as a prep for the Coral Gold Cup.
He won four of his six races over fences as a novice, with his two defeats coming on his chasing debut and at the Cheltenham Festival.
Nicholls also has Frodon and Enrillo engaged in the Coral Gold Cup at this stage.
"Threeunderthrufive goes for the Coral Gold Cup. Bravemansgame won't run. He will be taken out of the race," said Nicholls.
"Frodon is going to run at Wincanton on Saturday instead of going to Down Royal because of the ground and one thing and another. He's been dropped 6lb from his last handicap mark, which is a bit more acceptable.
"You would never rule him out because there aren't many options for him now. He will run in the Badger Beer Chase and that has always been a prep race for the Coral Gold Cup so he could go. Enrilo is in the Badger Beer too.
"But with Threeunderthrufive the plan has always been to go for this race and after his run at Wetherby on Saturday, the Coral Gold Cup will be his next start."
Threeunderthrufive is 10/1 second favourite with the sponsors behind joint-market leaders Dusart and Corach Rambler.
Coral's David Stevens said: "Threeunderthrufive is on target for the Coral Gold Cup following his recent Wetherby run, and he goes to Newbury with a major chance as far as we're concerned, with only Corach Rambler and Dusart currently shorter in our betting."