Emergency service were scrambled to the A13 near the Beckton Flyover at just after 7am on Friday.
Witnesses reported that the victim, 19, had collided with the central reservation on the westbound carriageway.
He was taken to hospital where he remains in a life-threatening condition.
His family have been informed and members Met’s Serious Collision Investigation Unit have been trawling the scene for clues to what caused the crash.
They are appealing for any witnesses or drivers who may have dash cam footage to come forward.
Anyone who can help is asked to call the witness appeal line on 0208 597 4847. Alternatively, call 101 or tweet @MetCC quoting CAD 1556/15Jan.