Munster top Pro14 Conference B after their 28-12 victory over Ospreys, while Cardiff Blues were defeated 23-14 by Ulster.
Scarlets made it three from three in Pro14 on Sunday as Glasgow Warriors earned a first win of the season.
Leinster's 21-year-old hooker Ronan Kelleher ran in a hat-trick in their thrashing of the Ospreys, while the Scarlets saw held off Glasgow.
Ruan Pienaar inspired the Cheetahs to victory over the Glasgow Warriors on Friday, while Ulster were too good for the Ospreys.
Alun Wyn Jones will remain on course to break the all-time record for international caps after extending his Welsh Rugby Union contract.
Nicky Smith was linked with the likes of Cardiff Blues, Sale Sharks and Gloucester, but the prop is staying with his home region.
A dramatic final day of the regular season in the Pro14 saw Glasgow Warriors make the semi-finals, while Ospreys and Scarlets will face off.
The Ospreys have announced that Wales fly-half Gareth Anscombe will join from Pro14 rivals Cardiff Blues ahead of the 2019-20 season.
Edinburgh's Pro14 play-off hopes hang by a thread after a damaging home defeat to Ulster, who extended their own domestic season.
Iliesa Ratuva Tavuyara touched down and Tommaso Allan converted with the last play of the game as Benetton Treviso held Leinster in Dublin.
Bonus-point wins for Glasgow Warriors and Munster mean the top two in Conference A remain three points apart.
The Ospreys have confirmed Alun Wyn Jones and George North both sustained injuries during the Six Nations that could end their season.
There will be no imminent merger of Welsh regions after it was confirmed all four will stay as they are next season.
Captain Alun Wyn Jones says the Wales squad have been affected by talk of a merger between the Scarlets and the Ospreys, which is...
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The back-and-forth between the Ospreys, Scarlets and PRB continued on Wednesday, with the Swansea region alleging a "stitch-up".
The Scarlets say the Ospreys approached them last December regarding a possible merger, but the plans have been scrapped.