In the event that Amir Khan upsets Canelo Alvarez on May 7, there is a rematch clause in the contract, according to ESPN Deportes, quoting promoter Oscar De La Hoya. This is surely not unexpected, since it's Alvarez's WBC title on the line and he's the A-side fighter, but it's worth a note, so there you go.
Khan (31-3, 19 KO) won a world title at 140 pounds in 2009, when he beat Andriy Kotelnik for the WBA belt. He held that until 2011, when he lost in a unification fight against IBF titleholder Lamont Peterson. Since then, Khan actually hasn't held a world title, though he is sometimes spun as a "two-weight world champion," due to his winning the WBC "Silver" title in 2014 when he beat Luis Collazo, which Khan defended against both Devon Alexander and Chris Algieri.
The fight with Alvarez (46-1-1, 32 KO) will take place at a 155-pound catchweight, with the WBC middleweight title on the line.