Photos: Zambrano-Marrero, Rosario-Gallimore - Official Weigh-In

The weights are in for the special Saturday night edition of Premier Boxing Champions on FS1 and FOX Deportes, April 29 from Sam's Town Live in Las Vegas. Photos by Ryan Hafey/Premier Boxing Champions.

WBA Interim Featherweight Champion Carlos Zambrano (26-0, KOs) defending his title against once-beaten contender Claudio Marrero (21-1, 15 KOs) has been elevated to the main event.

Televised coverage will begin at 10 p.m. ET/7 p.m. PT and will feature undefeated Jeison Rosario (12-0, 9 KOs) taking on once-beaten Nathaniel Gallimore (17-1-1, 14 KOs) in a 10-round middleweight attraction.

Zambrano weighed in at 125-pounds, while Marrero was 125.4. Rosario was 159-pounds, while Gallimore was 157.2.

An unbeaten fighter from Lima, Peru, Zambrano turned pro in 2008 and fought nine of his first 12 bouts in the U.S. He won a South American regional title in 2012 and began moving up the featherweight rankings with a knockout victory over Devis Perez in 2014. He picked up his interim title with a unanimous decision victory over Daniel Ramirez in 2015 and defended the belt successfully against Jose Sanmartin later that year.

A former title challenger who lost a narrow decision to Jesus Cuellar in 2013, Marrero has won seven-straight bouts since then. Most recently, the 28-year-old knocked down Luis Hinojosa four times before stopping him in the fourth round in August 2016. A native of Santo Domingo, Dominican Republic, Marrero was an accomplished amateur who will be fighting in Las Vegas for the second time in his pro career.

An unbeaten fighter out of Santo Domingo, Dominican Republic, Rosario will make his U.S. debut when he enters the ring on May 16. A pro since 2013, the 22-year-old scored knockouts in his first three starts and won a Domincan welterweight title with a second round stoppage of Jose Vidal Soto in 2014. Rosario's last three starts have seen him score TKO victories over Euro Gonzalez plus previously unbeaten fighters Carlos Jairo Cruz and Rafael Lorenzo.

Originally from Kingston, Jamaica and fighting out of Evanston, Illinois, Gallimore enters this fight having won his last four bouts, all by knockout. The 28-year-old has fought professionally since 2014 and was unbeaten in his first 14 outings before losing a narrow split-decision last June. He began his 2017 with a third round stoppage of Angel Hernandez in early April.