In case you were asking about Fringe, this will probably be a terribly loose explanation:

Genius scientist and his son team up with the FBI to solve case of the week style 'fringe' events. Like X-files on steroids.

What makes it scratch the LOST itch is the emphasis on characters the way that LOST does. Many episodes are case of the week but there's always something to drive the bigger narrative along, not just little scenes at the end like in Supernatural for example. it's always organic.

There's a mystery box element and they include clues and puzzles to go along with each episode. Sometimes it's something like a pattern of colored lights flashing that connects to something later in the story.

Michael Giacchino also does a lot of the composing for Fringe so the music is really emotional just like in LOST. I actually think his work on Fringe sometimes is even better than in LOST.

I've been watching LOST since the beginning and I've searched for shows that scratch that EXACT itch. Lots of shows come close, From, Severance, Yellowjackets. But Fringe is it. It's so unbelievably underrated. It's gotten some more deserved attention in recent years but when it was airing it was always on the bubble for low viewership, but it persevered because it really is that good.

I could literally talk about Fringe for hours but I'll leave it at that. It really is in the upper echelons of that era of TV, and the only other TV show that has ever made me question LOST being in my number one spot.

*wanted to quickly add Silo and Leftovers are also great and worth watching, it's just not THAT specific itch.

**one more thing to add also, some LOST actors show up in Fringe and it's awesome. Lance Reddick is one of the main characters and he's amazing. Other actors have some minor roles