There are clinical trials being undertaken at The Royal University Liverpool Hospital in England, with the drug named as Nitisinone these trials are on going and results so far are very favourable, but this drug is still awaiting enough results for the drug to be licenced and available for all Alkaptonuria patients.
A low protein diet is also required with this drug, the same trials of this drug has taken place in Maryland United States of America, but I am unaware of the conclusions of these trials.