The following study suggests ABT-263 could be an effective treatment for synovial sarcoma and even more so in combination with doxorubicin:
http://www.ncbi.nlm.nih.gov/pubmed/22797074
There is no open trial at the moment for this drug but a phase I study was completed for solid tumor:
http://www.ncbi.nlm.nih.gov/pubmed/21282543
The major adverse effect was thrombocytopenia (low platelet count).
Hopefully a phase II study will soon follow...