Not quite at the same stage, but Jack went through a phase of 4.30 starts when he was just under 1 - firstly HUGS becuase I know how completely draining it is - it seemed to colour my whole life for about a month - constant exhaustion is no fun at all. I know what you are going through!! You have my virtual hugs!
He was having two 45 min naps per day at that point. I know it may not be easy, and may seem a bit cruel, but I went cold turkey to 1 nap and also started hanging back a little at 4.30 - try and increase by 15 mins per day when you first go into them (unless they're screaming!!). If they are screaming, go and comfort them, but still don't start your day until 15 mins later each time - they will eventually get the message.
Within a week he was sleeping 2 hours after lunch and waking at 6.45. You may want to check out some of the posts on extending naps aswell - Jack did quite well at doing that by himself, but if your LO doesn't, and you do want to cut out the third nap you may need to help them.
You may want to consistently try aiming for 2 naps, bring bedtime forward as suggested and hold back on going in at 4.30.
Just my experience - hth