I have a large datafile in the following format below:

ENST00000371026 WDR78,WDR78,WDR78,  WD repeat domain 78 isoform 1,WD repeat domain 78 isoform 1,WD repeat domain 78 isoform 2,
ENST00000371023 WDR32   WD repeat domain 32 isoform 2
ENST00000400908 RERE,KIAA0458,  atrophin-1 like protein isoform a,Homo sapiens mRNA for KIAA0458 protein, partial cds.,

The columns are tab separated. Multiple values within columns are comma separated. I would like to remove the duplicate values in the second column to result in something like this:

ENST00000371026 WDR78   WD repeat domain 78 isoform 1,WD repeat domain 78 isoform 1,WD repeat domain 78 isoform 2,
ENST00000371023 WDR32   WD repeat domain 32 isoform 2
ENST00000400908 RERE,KIAA0458   atrophin-1 like protein isoform a,Homo sapiens mRNA for KIAA0458 protein, partial cds.,

I tried the following code below but it doesn't seem to remove the duplicate values.

awk ' 
BEGIN { FS="\t" } ;
{
  split($2, valueArray,",");
  j=0;
  for (i in valueArray) 
  { 
    if (!( valueArray[i] in duplicateArray))
    {
      duplicateArray[j] = valueArray[i];
      j++;
    }
  };
  printf $1 "\t";
  for (j in duplicateArray) 
  {
    if (duplicateArray[j]) {
      printf duplicateArray[j] ",";
    }
  }
  printf "\t";
  print $3

}' knownGeneFromUCSC.txt

How can I remove the duplicates in column 2 correctly?