The 27-year-old Blackwood fighter had feared the worst in a row over the status of his fight against the Tunisian Ferid Ben Jeddou after the supervisor Bobby Lee Jnr insisted at the rules meeting that it would be a final eliminator and not for the interim International Boxing Federation title as billed.
But the promoter Frank Warren, in Philadelphia with Frank Bruno to watch Mike Tyson, convinced the IBF president, Bobby Lee Snr, otherwise and Regan responded by knocking out the Italian-based Ben Jeddou in the second round with the sweetest punch of his career.
Chris Pyatt, who lost the World Boxing Organisation middleweight title to Steve Collins 18 months ago, kept his career alive by regaining the Commonwealth light-middleweight belt.
The 32-year-old took some solid right-hand punches from the Australian holder Kevin Kelly. But the referee, Dave Parris, preferred Pyatt's aggression to the way Kelly fought on the retreat and gave him a 118-116.5 points decision.