Fagerson has been out of action with a calf injury since April and Dempsey has been sidelined since the Six Nations due to a hamstring problem.
Speaking in The Scotsman, Glasgow attack coach Nigel Carolan said: "Both are making some really good progress but this weekend is going to be too early for the two of them. Certainly for Zander and his Lions tour, he's well on track there. He's one we could definitely do with at the moment, he's a big player. He's getting close but this weekend is just a bit too soon."
Huw Jones missed Friday night's win over the Stormers due to an ongoing Achilles tendon issue, and is unlikely to be risked against Leinster if there any doubts around his fitness.
"Huw is not the worst," said Carolan. "We need to track him and see how he's progressing through the week. We pulled him [out] last week. He was just a little bit tight in that area. He had a scan and a jab in it. We'll see how he progresses this week.
"He's on track but we're going to have to wait and see. He won't train [on Monday] but we'll see how he is on Tuesday and Thursday.
"Huw wants to do what's best for himself and the club first of all. Maybe if there was no Lions tour he could risk it. But he wants to put the best version of himself out there as well. At the moment, he just has to hold back. He's afraid to just let loose on that, until it settles down.
"Everyone wants to see Huw Jones at full strength and full stride. But if he's holding back, I don't think it"s good for anybody."
Loosehead prop Rory Sutherland is available again after injury and tighthead Sam Talakai should be fit for Dublin despite taking a bang to the arm against the Stormers.
Carolan also commented on the reports Dan Lancaster will be joining up at Scotstoun next season.
The Scottish-qualified stand-off's contract with Racing 92 expires at the end of the season and reprts in the rugby press say he'll join Warriors.
Carolan said Warriors would be in the market for quality Scottish-qualified players.
"I'm not involved in those upstairs decisions," said Carolan. "The way we're playing at the moment, I think we're a club that hopefully will attract a lot of players. For players of national interest, we're definitely a good option at the moment. I'm not too sure who's involved with that side of things but if he does come, he's been doing quite well with Racing this year. He'd be a great acquisition.
"With our backs, we've got serious quality there. If we can add to it, we've got so many guys that we've developed over the last couple of years who are now of national interest. I think on those [international] windows where those guys are away, it's important that we continue to develop our own players. If there's one or two that can add to that quality, I think it's important as well."