Dead Evolution (2005)

Josh Holden plays a hit-man, who is hired to off a scientist who is working on a cell regeneration formula. The hit-man (who Holden later named Angus, and made a side story for him) injects the scientist with his own formula, which kills him. However, neither the hit-man or the greedy company that hired him know the full extent of the formula. We're about to see the results.