Cushing was suspended for four games without pay after testing positive last September for hCG, a fertility drug that is on the league's banned substance list. He said he never took a banned substance and has no idea how the positive test happened.
McNair hopes to present new evidence that will shorten or eliminate Cushing's suspension, according to the Houston Chronicle and KRIV-TV.
A source told KRIV-TV that Cushing has been going through a battery of medical tests with hopes of showing the NFL the elevated levels of hCG found in his body were naturally occurring.
McNair recently said he believes Cushing is innocent and has paid for some of Cushing's recent tests, according to the Chronicle.
Cushing had 133 tackles for the Texans last season to win The Associated Press Defensive Rookie of the Year award and retained it after a revote following his suspension.
Information from The Associated Press was used in this report.