Starfleet ship classes usually share their name with the class prototype ship. (スタートレック3：ミスター・スポックを探せ; Star Trek: The Next Generation Technical Manual) Assuming that only one ship of a given name is in service at any time, the USS Challenger prototype for the Challenger-class was retired some time prior to 2377, when the Galaxy級 USSChallenger (NCC-71099) was seen in VOY: Endgame.
The Challenger-class USS Buran was a "kitbashed" design study and filming model built by Ed Miarecki and Michael Okuda, that was barely glimpsed among the wreckage of the "graveyard" scene in TNG: The Best of Both Worlds, Part II.  It was made from parts of AMT/Ertl USSEnterprise-D model kits, no. 6619, specifically the saucer section and warp nacelles, as well as from parts of a submarine model kit. Okuda recalled on the model, "I don't recall what Ed's original version of the Buran was, but I added the submarine parts and glued on the engines, although it looks like Ed assembled the engines. I thought it was a clever idea, but it ended up looking like a lollipop. Maybe Ed's version was a single nacelle, and I added the second. I don't remember.(...)I think one of the engine mounts was a submarine tower, but I wouldn't swear that both were. I'm pretty sure both engines were fairly stock Ertl large Galaxy nacelles that Ed had made. The actual amount of modelmaking time that Rick S. and I had was minimal, so we would tend to have stuck with stuff that Ed did for us." 
In the Star Trek: The Next Generation Annual story "Thin Ice" published by DC Comics, the USS Marco Polo was stated to be a Challenger-class starship. This design appeared as a variant of the Constellation級 design, with the lower nacelles replaced by a secondary hull.