"Created to replace Superman, Superboy is the closest human equivalent to a Kryptonian that Cadmus scientists could create. His tactile telekinesis approximates superstrength, flight, invulnerability, as well as granting him a number of unique abilities such as disassembing objects with a single touch. The Kryptonian duplication was carried out in such scrupulous detail that the kid is also susceptible to Kryptonite radiation. It is theorized that he is a solar battery like Superman and may have other abilities that he was intended to grow into"
“Cadmus decided to clone their own Man of Steel. Starting by getting a sample of super-genes, right? No way is more like it! Turns out, in Kryptonian, DNA means ‘do not analyze’. But Director Westfield had a second team and Plan B waiting in the wings. They genetically engineered the closest human equivalent to Superman that they could. Mainly, me! And who, may I ask, was I cloned from? The only person that Mr. Forget My Ethics would trust with that much power, of course. Westfield himself! Only good news is that they genetically changed just about everything when they made me.” – Team Superman: Secret Files and Origins #1
“We obtained Superman’s body. But the usual cloning techniques were useless on his alien physiology. We could genetically alter a clone to look like Superman. But we needed to simulate Superman’s powers” – Adventures of Superman #506
“Cadmus certainly knew what they were doing! You’re totally human of course. But they made you as Kryptonian-like as possible.” -Superboy #0
“I’m the closest thing to Superman that advanced genetics could cook up”
“You’re up against the closest genetic equivalent of Superman science could create” – Superboy/Robin WF3 #1 and #2
“Well I think the most common misconception is that Superboy’s a clone of Superman himself. But that’s not true. He is a clone, created by Project Cadmus, which was trying to produce a replacement for Superman when the world thought that he was dead. But the cellstock used to create Superboy didn’t come from Superman. It came from some other source. One that executive director Paul Westfield thought would make Superboy easier to control.” – Superboy #32