Chordoma is a rare, slow growing malignant tumor arising from remnants of the 
fetal notochord. Surgery is the first choice for chordoma treatment, followed by 
radiotherapy, although postoperative complications remain significant. 
Recurrence of the disease occurs frequently due to the anatomy of the tumor 
location and violation of the tumor margins at the initial surgery. Currently, 
there are no effective drugs available for patients with chordoma. Due to the 
rarity of the disease, there is limited opportunity to test agents in clinical 
trials and no concerted effort to develop agents for chordoma in the 
pharmaceutical industry. To rapidly and efficiently identify small molecules 
that inhibit chordoma cell growth, we screened the NCGC Pharmaceutical 
Collection (NPC) containing approximately 2800 clinically approved and 
investigational drugs at 15 different concentrations in chordoma cell lines, 
U-CH1 and U-CH2. We identified a group of drugs including bortezomib, 17-AAG, 
digitoxin, staurosporine, digoxin, rubitecan, and trimetrexate that inhibited 
chordoma cell growth, with potencies from 10 to 370 nM in U-CH1 cells, but less 
potently in U-CH2 cells. Most of these drugs also induced caspase 3/7 activity 
with a similar rank order as the cytotoxic effect on U-CH1 cells. Cantharidin, 
digoxin, digitoxin, staurosporine, and bortezomib showed similar inhibitory 
effect on cell lines and 3 primary chordoma cell cultures. The combination 
treatment of bortezomib with topoisomerase I and II inhibitors increased the 
therapeutic potency in U-CH2 and patient-derived primary cultures. Our results 
provide information useful for repurposing currently approved drugs for chordoma 
and potential approach of combination therapy.