Ukranian world champions Vasyl Lomachenko and Oleksandr Usyk retained their belts on Saturday night in Maryland.
Lomachenko's status as one of the world's best pound-for-pound talents was enhanced when opponent Jason Sosa failed to emerge for the 10th round of their WBO super-featherweight title fight.
The former amateur prodigy improved to 8-1 as a pro, including world titles in two divisions, as his second consecutive opponent withdrew in the corner. Nicholas Walters previously lost to Lomachenko in the same manner.
On the undercard, 2012 Olympic gold medal winner Uysk remained unbeaten in 12 as a professional with a unanimous decision victory against Michael Hunter Jr in defence of the WBO cruiserweight title.
Oleksandr Gvozdyk, a bronze medal winner for Ukraine at the 2012 Games, scored a three-round stoppage of Yunieski Gonzalez to move to 13-0 as a professional light-heavyweight.
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