Gazidis said short-comings of the team, which finished fourth in the Premier League and a sixth successive season without a trophy, had to be acknowledged and rectified.
"It is going to be an active summer. I expect to be busy and Arsene expects to be busy," Gazidis told a meeting of the Arsenal Supporters Trust at Emirates Stadium on Monday. "We are working hard during this close season - very hard."
Asked if the club had spoken to anybody so far in the transfer market, Gazidis replied: "Yes, many people."
However, he declined to elaborate on who and also refused to answer questions on the future's of midfielders Cesc Fabregas and Samir Nasri who have been linked with moves to other clubs.
"Coming off the end of the season, I can't say anything other than, like you, I share a sense of profound disappointment," he said.
"We had a season that promised a great deal, which looked as though it could turn into a very special season for us, but in the end a familiar story began to tell."
Arsenal had some successes last season, beating Barcelona, Manchester United and Chelsea at home, and spoke of winning a quadruple of trophies in February.
But then, in quick succession, Arsenal lost the League Cup final to Birmingham City, were knocked out of the Champions League by Barcelona and ended the season with a string of losses and draws to finish 12 points behind champions Manchester United.
Gazidis said it was as hard for him as for any other Arsenal supporter to watch the last few games of the season.
"VERY HARD"
"It is very clear that we had some short-comings and during this close season we are going to see some turnover of players, some new signings coming in, and some of our existing squad going out," he added. "It will be a busy close season for the club."
"Arsene's commitment remains very strong. We know that there were moments when we looked as if we were close last season but we need to acknowledge and correct the failings that we had. As I have said there will be new signings and some departures."
Gazidis stressed that new signings had to be made within the club's resources, a policy that has angered some supporters who have looked enviously at rivals Chelsea and Manchester City that have relied on rich benefactors to bank-roll player transfers.
"In order for the club to be the best that it can be and in order to deliver on its values and to deliver the excellence that we expect, it also has to be a good and sustainable business over the long term," Gazidis said.
"It is also important to recognise that it hasn't been a disaster. We still have a young squad. We don't want to throw the baby out with the bathwater. The trick will be identifying which parts to keep and which parts to turnover and how we can do that within our financial capabilities."
Gazidis said Arsenal's spending policy had not been changed by the takeover of the club by U.S. investor Stan Kroenke: "With respect to Stan, we have someone who understands the cl
