Not really. The X-15 is/was a hypersonic research platform, intended to research flight in the (upper) atmosphere. The X-15B, as stated by the OP, was a manne

Not really. The X-15 is/was a hypersonic research platform, intended to research flight in the (upper) atmosphere. The X-15B, as stated by the OP, was a manned spaceflight program. The X-37 is basically a reusable (unmanned) satellite. They are very different programs. There are perhaps some engineers that worked on both programs because North American eventually became owned by Boeing, but the programs share no design heritage that I can tell.