ABC is advertising next Thursday's episode as the "series finale." "Shark Tank" will take over the slot for a week before repeats of "Grey's Anatomy" move into the Thursday 8 p.m. time period.

It's official: ABC's Once Upon a Time in Wonderland will not return for a second season.

The Hollywood Reporter has confirmed that the Once spinoff will end its run following its April 3 season-ender, which the network is advertising as a "series finale."

The decision to not move forward with the 13-episode spinoff -- from Once creators Adam Horowitz and Eddy Kitsis -- comes after the series was originally envisioned as a miniseries intended to bridge the gap between seasons of the flagship series.

ABC instead opted to run the series in the fall, scheduling the series in its historically problematic Thursdays at 8 p.m. slot where Last Resort, Charlie's Angels, Missing, My Generation and FlashForward have similarly stumbled. ABC has struggled to launch a hit in the time period since Ugly Betty moved from the 8 p.m. hour in 2009.

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ABC Entertainment Group president Paul Lee told reporters in January that the series, which opened soft in October before quickly sliding further down the rabbit hole in the weeks afterward, that he "should have" slated Wonderland as originally planned.

"That would have been a natural audience to go through there," Lee said in January at the Television Critics Association's winter press tour. "That Thursday slot is difficult. We loved the idea. We knew the creative was great, and so we loved the idea of having a run of empowered women going all the way through Thursday night [with Grey's Anatomy and Scandal]. What we didn’t want to do is play defense on Thursday when we wanted to play offense. But in retrospect, I think it would have done better there, and I should have stuck to the earlier idea. … I totally take responsibility for that."

In an interview in this week's THR, ABC Studios chief Patrick Moran singled out Wonderland as the biggest disappointment this past season. "I really had hoped that Once Upon a Time in Wonderland would work. It was designed to be what they call 'gap programming,' to go in between the regular season, and it probably would have fared better as that," he said.

For their part, producers said that Wonderland would tell a complete tale with a "beginning, middle and end" and was meant to be a "closed-ended story." Horowitz said in August that should the series be successful, "hopefully" another story could be told with the same cast.

Following Wonderland's April 4 conclusion, ABC will test reality hit Shark Tank on Thursday at 8 p.m. for a week as part of a two-night special on April 10 and 11. Repeats of Grey's Anatomy will take over the slot starting April 17, leading into original episodes of the medical drama and Kerry Washington starrer Scandal, giving Shonda Rhimes a three-hour block on the network.

The move to end Wonderland comes a day after ABC canceled rookie Mind Games, adding to a particularly challenging season for the network. Among its freshman class, only dramas Resurrection, Agents of SHIELD and upcoming mini The Black Box -- and comedies The Goldbergs, Trophy Wife and midseason entry Mixology -- remain in consideration for next season.

Check out the promo for next week's series finale below.

Email: Lesley.Goldberg@THR.com

Twitter: @Snoodit